basic to site specific electric training

Basic to Site SpecificElectric Training

Create by: Theunis Venter

Safety:

• No job is so important, that

• Low / High voltages can cause electrical shock, burns and death.• Do isolation procedure on power before proceeding with any work on

electrical equipment. This procedure should be read in conjunction with the following documents: ASSESSMENTS, METHOD STATEMENTS, WORKS / HEALTH & SAFETY PROCEDURES,INSTALLATION & COMMISSIONING PROCEDURE

• Never ever take any “SHORT CUTS” on any work you do.

can’t follow working procedures.


Course Outline

• ANSI Standard Device Designation and Explanations.

• Basic Electrical Knowledge and Safety Update.

• Test Equipment.

• Electrical Motors

• Cable Glanding / Splicing Procedures.

• IP Rating of Enclosures and Light Fixtures.

• Basic Understanding and Configure of Siemens SIMOCODE-DP System Motor Protection and Control.

• Basic Understanding of SAG Mill Sprint Electric PL/PLX Digital DC Drive


ANSI Standard Device Designation and Explanations.

Master Element is the initiating device, such as a control switch, voltage relay, float switch, etc., which serves either directly or through such permissive devices as protective and time -delay relays to place an equipment in or out of operation.

Time Delay Starting or Closing Relay is a device that functions to give a desired amount of time delay before or after any point of operation in switching sequence or protective relay system, except as specifically provided by service function.

Checking or Interlocking Relay is a relay that operates in response to the position of a number of other devices (or to a number of predetermined conditions) in an equipment, to allow an operating sequence to proceed, or to stop, or to provide a check of the position of these devices or of these conditions for any purpose.

Master Contactor is a device generally controlled by device function or the equivalent and the required permissive and protective devices that serves to make and break the necessary control circuits to place an equipment into operation under the desired conditions and to take it out of operation under other or abnormal conditions.

Stopping Device is a control device used primarily to shut down an equipment and hold it out of operation. (This device may be manually or electrically actuated, but excludes the function of electrical lockout on abnormal conditions.)

Starting Circuit Breaker is a device whose principal function is to connect a machine to its source of starting voltage.

Anode Circuit Breaker is a device used in the anode circuits of a power rectifier for the primary purpose of interrupting the rectifier circuit if an arc-back should occur.


Control Power Disconnecting Device is a disconnecting device, such as a knife switch, circuit breaker, or pull-out fuse block, used for the purpose of respectively connecting and disconnecting the source of control power to and from the control bus or equipment. Note: control power is considered to include auxiliary power which supplies such apparatus as small motors and heaters.

Reversing Device is a device that is used for the purpose of reversing a machine field or for performing any other reversing functions.

Unit Sequence Switch is a switch that is used to change the sequence in which units may be placed in and out of service in multiple-unit equipment.

Over-Speed Device is usually a direct-connected speed switch which functions on machine over-speed.

Synchronous-Speed Device is a device such as a centrifugal switch, a slip-frequency relay, a voltage relay and undercurrent relay or any type of device that operates at approximately the synchronous speed of a machine.

Under-Speed Device is a device that functions when the speed of a machine fall below a pre –determined value.

Speed or Frequency Matching Device is a device that functions to match and hold the speed or frequency of a machine or of a system equal to, or approximately equal to, that of another machine, source, or system.


Shunting or Discharge Switch is a switch that serves to open or to close a shunting circuit around any piece of apparatus (except a resistor, such as a machine field, a machine armature, a capacitor, or a reactor). Note: This excludes devices that perform such shunting operations as may be necessary in the process of starting a machine by devices or their equivalent, and also excludes device function that serves for the switching of resistors.

Accelerating or Decelerating Device is a device that is used to close or to cause the closing of circuits which are used to increase or decrease the speed of a machine.

Starting-to-Running Transition Contactor is a device that operates to initiate or cause the automatic transfer of a machine from the starting to the running power connection.

Valve is one used in a vacuum, air, gas, oil, or similar line, when it is electrically operated or has electrical accessories such as auxiliary switches.

Distance Relay is a relay that functions when the circuit admittance, impedance, or reactance increases or decreases beyond predetermined limits.

Equalizer Circuit Breaker is a breaker that serves to control or to make and break the equalizer or the current-balancing connections for a machine field, or for regulating equipment in a multiple -unit installation.

Undervoltage Relay is a relay that functions on a given value of under-voltage.


Temperature Control Device is a device that function to raise or lower the temperature of a machine or other apparatus, or of any medium, when its temperature falls below, or rises above, a predetermined value. Note: An example is a thermostat that switches on a space heater in a switchgear assembly when the temperature falls to a desired value as distinguished from a device that is used to provide automatic temperature regulation between close limits and would be designated as device function.

Synchronizing or Synchronism-Check Device is a device that operates when two a-c circuits are within the desired limits of frequency, phase angle, or voltage, to permit or to cause the paralleling of these two circuits.

Apparatus Thermal Device is a device that functions when the temperature of the shunt field or the amortisseur winding of a machine, or that of a load limiting or load shifting resistor or of a liquid or other medium, exceeds a predetermined value: or if the temperature of the protected apparatus, such as a power rectifier, or of any medium decrease below a predetermined value.

Flame Detector is a device that monitors the presence of the pilot or main flame of such apparatus.

Isolating Contactor is a device that is used expressly for disconnecting one circuit from another for the purposes of emergency operation, maintenance, or test.

Annunciator Relay is a non-automatically reset device that gives a number of separate visual indications of the functions of protective devices, and which may also be arranged to perform a lockout function.


Separate Excitation Device is a device that connects a circuit, such as the shunt field of a synchronous converter, to a source of separate excitation during the starting sequence; or one that energizes the excitation and ignition circuits of a power rectifier.

Directional Power Relay is a device that functions on a desired value of power flow in a given direction or upon reverse power resulting from arc back in the anode or cathode circuits of a power rectifier.

Position Switch is a switch that makes or breaks contact when the main device or piece of apparatus which has no device function number reaches a given position.

Master Sequence Device is a device such as a motor-operated multi-contact switch, or the equivalent, or programming device, such as a computer, that establishes or determines the operating sequence of the major devices in an equipment during starting and stopping or during other sequential switch operations.

Brush-Operating or Slipping Short-Circuiting Device is a device for raising, lowering, or shifting the brushes of a machine, or for short-circuiting its slip rings, or for engaging or disengaging the contacts of a mechanical rectifier.

Polarity or Polarizing Voltage Device is a device that operates, or permits the operation of, another device on a predetermined polarity only, or verifies the presence of a polarizing voltage in an equipment.

Undercurrent or Underpowered Relay is a relay that function when the current or power flow decreases below a predetermined value.


Bearing Protective Device is a device that functions on excessive bearing temperature, or on another abnormal mechanical conditions associated with the bearing, such as undue wear, which may eventually result in excessive bearing temperature.

Mechanical Condition Monitor is a device that functions upon the occurrence of an abnormal mechanical condition (except that associated with bearing as covered under device function 38), such as excessive vibration, eccentricity, expansion shock, tilting, or seal failure.

Field Relay is a relay that functions on a given or abnormally low value or failure of a machine field current, or on excessive value of the reactive component of armature current in an A-C machine indicating abnormally low field excitation.

Field Circuit Breaker is a device that functions to apply or remove the field excitation of a machine.

Running Circuit Breaker is a device whose principal function is to connect a machine to its source of running or operation voltage. This function may also be used for a device, such as a contractor, that is used in series with a circuit breaker or other field protecting means, primarily for frequent opening and closing of the breaker.

Manual Transfer or Selector Device is a manually operated device that transfers the control circuits in order to modify the plan of operation of the switching equipment or of some of the devices.


Unit Sequence Starting Relay is a relay that function to start the next available unit in a multiple-unit equipment upon the failure or non-availability of the normally preceding unit.

Atmospheric Condition Monitor is a device that functions upon the occurrence of an abnormal atmospheric condition, such as damaging fumes, explosive mixtures, smoke or fire.

Reverse Phase or Phase Balance Current Relay is a relay that functions when the polyphase currents are of reverse-phase sequence, or when the polyphase currents are unbalanced or contain negative phase-sequence components above a given amount.

Phase-Sequence Voltage Relay is a relay that function upon a predetermined value of polyphase voltage in the desired phase sequence.

Incomplete Sequence Relay is a relay that generally returns the equipment to the normal, or off, position and locks it out if the normal starting, operating, or stopping sequence is not properly completed within a predetermined time. If the device is used for alarm purposes only, it should preferably be designated as 48A (alarm).

Machine or Transformer Thermal Relay is a relay that functions when the temperature of a machine armature or other load-carrying winding or element of a machine or the temperature of a power rectifier or power transformer (including a power rectifier transformer) exceeds a predetermined value.

Instantaneous Overcurrent or Rate of Rise Relay is a relay that functions instantaneously on an excessive value of current or on an excessive rate of current rise, thus indicating a fault in the apparatus or circuit being protected.


AC Time Overcurrent Relay is a relay with either a definite or inverse time characteristic that functions when the current in an AC circuit exceed a predetermined value.

AC Circuit Breaker is a device that is used to close and interrupt an AC power circuit under normal conditions or to interrupt this circuit under fault of emergency conditions.

Exciter or DC Generator Relay is a relay that forces the DC machine field excitation to build up during starting or which functions when the machine voltage has been built up to a given value.

High-Speed DC Circuit Breaker is a circuit breaker which starts to reduce the current in the main circuit in 0.01 second or less, after the occurrence of the DC overcurrent or the excessive rate of current rise.

Power Factor Relay is a relay that operates when the power factor in an AC circuit rises above or falls below a predetermined value.

Field Application Relay is a relay that automatically controls the application of the field excitation to an AC motor at some predetermined point in the slip cycle.

Short-Circuiting or Grounding Device is a primary circuit switching device that functions to short-circuit or to ground a circuit in response to automatic or manual means.


Rectification Failure Relay is a device that functions if one or more anodes of a power rectifier fail to fire, or to detect and arc-back or on failure of a diode to conduct or lock properly.

Overvoltage Relay is a relay that functions on a given value of over-voltage.

Voltage or Current Balance Relay is a relay that operates on a given difference in voltage, or current input or output, or two circuits.

Time-Delay Stopping or Opening Relay is a time-delay relay that serves in conjunction with the device that initiates the shutdown, stopping, or opening operation in an automatic sequence or protective relay system.

Liquid or Gas Pressure or Vacuum Relay is a relay that operates on given values of liquid or gas pressure or on given rates of change of these values.

Ground Protective Relay is a relay that functions on failure of the insulation of a machine, transformer, or of other apparatus to ground, or on flashover of a DC machine to ground. Note: This function is assigned only to a relay that detects the flow of current from the frame of a machine or enclosing case or structure of piece of apparatus to ground, or detects a ground on a normally ungrounded winding or circuit. It is not applied to a device connected in the secondary circuit of current transformer, in the secondary neutral of current transformers, connected in the power circuit of a normally grounded system.


Governor is the assembly of fluid, electrical, or mechanical control equipment used for regulating the flow of water, steam, or other medium to the prime mover for such purposes a starting, holding speed or load, or stopping.

Notching or Jogging Device is a device that functions to allow only a specified number of operations of a given device or equipment, or a specified number of successive operations within a given time of each other. It is also a device that functions to energize a circuit periodically or for fractions of specified time intervals, or that is used to permit intermittent acceleration or jogging of a machine at low speeds for mechanical positioning.

AC Directional Overcurrent Relay is a relay that functions on a desired value of AC over-current flowing in a predetermined direction.

Blocking Relay is a relay that initiates a pilot signal for blocking of tripping on external faults in a transmission line or in other apparatus under predetermined condition, or cooperates with other devices to block tripping or to block re-closing on an out-of-step condition or on power savings.

Permissive Control Device is generally a two-position, manually-operated switch that, in one position, permits the closing of a circuit breaker, or the placing of an equipment into operation, an in the other position prevents the circuit breaker or the equipment from being operated.

Rheostat is a variable resistance device used in an electric circuit, which is electrically operated or has other electrical accessories, such an auxiliary, position or limit switches.


Liquid or Gas Level Relay is a relay that operates on given values of liquid or gas level or on given rates of change of these values.

DC Circuit Breaker is a circuit breaker that is used to close and interrupt a DC power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions.

Load Resistor Contactor is a contactor that is used to shunt or insert a step of load limiting, shifting, or indicating resistance in a power circuit, or to switch a space heater in circuit, or to switch a light or regenerative load resistor, a power rectifier, or other machine in and out of circuit.

Alarm Relay is a relay other than an annunciator, as covered under device function 30 that is used to operate or to operate in connection with, a visual or audible alarm.

Position Changing Mechanism is a mechanism that is used for moving a main device from one position to another in an equipment: as for example, shifting a removable circuit breaker unit to and from the connected, disconnected, and test positions.

DC Overcurrent Relay is a relay that function when the current in a DC circuit exceeds a given value.

Pulse Transmitter is used to generate and transmit pulses over a telemetering or pilot-wire circuit to the remote indicating or receiving device.


Phase-Angle Measuring or Out-Of-Step Protective Relay is a relay that functions at a pre-determined phase angle between two voltages or between two currents or between a voltage and current.

AC Reclosing Relay is a relay that controls the automatic reclosing and locking out of an AC circuit interrupter.

Liquid or Gas Flow Relay is a relay that operates on given values of liquid or gas flow or on given rates of change of these values.

Frequency Relay is a relay that functions on a predetermined value of frequency (either under or over or on normal system frequency) or rate of change of frequency.

DC Reclosing Relay is a relay that controls the automatic closing and re-closing of a DC circuit interrupter, generally in response to load circuit conditions.

Automatic Selective Control or Transfer Relay is a relay that operates to select automatically between certain sources or conditions in an equipment, or performs a transfer operation automatically.

Carrier or Pilot Wire Receiver Relay is a relay that is operated or restrained by a signal used in connection with carrier-current or d-c pilot-wire fault directional relaying.

Locking Out Relay is an electrically operated hand, or electrically reset relay or device that functions to shut down or hold an equipment out of service, or both, upon the occurrence of abnormal conditions.


Differential Protective Relay is a protective relay that functions on a percentage or phase angle or other quantitative difference of two currents or of some other electrical quantities.

Auxiliary Motor or Motor Generator is one used for operating auxiliary equipment, such as pumps, blowers, exciters, rotating magnetic amplifiers, etc.

Line Switch is a switch used as a disconnecting, load-interrupter, or isolating switch in an AC or DC power circuit, when this device is electrically operated or has electrical accessories, such as an auxiliary switch, magnetic lock, etc.

Regulating Device is a device that functions to regulate a quantity, or quantities, such as voltage, current power, speed, frequency, temperature, and load at a certain value or between certain (generally close) limits for machines, tie lines, or other apparatus.

Voltage Directional Relay is a device which operates when the voltage across an open circuit breaker or contactor exceeds a given value in a given direction.

Operating Mechanism is the complete electrical mechanism or servomechanism, including the operating motor, solenoids, position switches, etc., for a tap changer, induction regulator, or any similar piece of apparatus which otherwise has no device function number.


Voltage and Power Directional Relay is a relay that permits or causes the connection of two circuits when the voltage difference between them exceed a given value in a predetermined direction and causes these two circuits to be disconnected from each other when the power flowing between them exceeds a given value in the opposite direction.

Field-Changing Contactor is a contactor that functions to increase or decrease, in one step, the value of field excitation on a machine.

Tripping or Trip-Free Relay is a relay that function to trip a circuit breaker, contactor or equipment, or to permit immediate tripping by other devices; or to prevent immediate re -closure of a circuit interrupter if it should open automatically even though its closing circuit is maintained closed.* Used only for specific applications in individual installations where none of the assigned numbered functions.

SCADA Supervisory Control and Data Acquisition(On site we call it “WinCC”)

Serial Link cable between devices which carries electrical pulses in series

Multi-drop is a shared serial link between several devices using some form of addressing scheme.

Protocol the language used by devices to communicate with each other.

Master/Slave is a protocol which uses a one Master to many Slaves relationship between devices.


Timeout is a period of time allowed for a device to respond.

Retry is a re-transmission of a message which did not receive a valid response.

Error Detection used to ensure a message is received without error.

Baud Rate is also called Bits per Second – speed of transmission.

Data Bits is the number of bits per packet that make up the data.

Stop Bits is the number of bits per packet that make up the stop sequence.

Thermal Capacity of the motor is the heat input required to take the motor to the maximum temperature it can withstand without suffering damage. The thermal capacity is derived from the maximum time the motor can be stalled / locked. The engineer uses the maximum stall time when cold to select a protection curve number to ensure a trip will occur prior to the maximum stall time.

Hot / Cold Ratio Defined as the ratio of stalled time of the motor when hot against stalled time when cold. For example, Stall time (Hot) = 6s and Stall Time (Cold) = 9s then Ratio = 6/9 x 100 = 66%

Cooling Time is the stopped motor cooling time defines the length of time for a motor to reach a steady ambient temperature from its maximum temperature (I.e. 100% thermal capacity).



Basic Electrical Knowledge and Safety Update.Basic Electricity Knowledge Update:

What is electricity? Electricity is the movement (flow) through a conductor of electric charges. In solids such as metal wire, the charges consist of negatively charged electrons. In gases and liquids, we have both electron and ion flow. As shown above a typical atom consists of a nucleus composed of positively charged protons and neutral (no charge) neutrons. Much like a solar system, atoms have rings of negatively charged electrons that orbit the positively charged nucleus. In a normal atom the number of positive and negative charges are equal, leaving the entire atom with no electric charge. The number of protons is also known as atomic number and determines what the chemical element is. Helium has two protons; copper has 29 protons, while aluminum has 13 protons

The Law of Charges states that unlike charges attract while like charges repel. In the helium atom above, the attraction of two positively charged protons in the nucleus keep the two electrons from flying off into space. Centrifugal force from the electrons spinning around the nucleus keeps the electrons from falling inward. If we were to add enough energy (heat, light, friction, etc.) to the atom, the electrons will spin faster and faster until one of them is thrown off and becomes a free electron.


This would leave the atom with a net positive charge as we have two positive protons and one negative electron. This is called an iron and an ion can be negative or positive. Note that ions and other charged particles can be influenced by a magnetic field.

ConductorsAs illustrated above many chemical elements have rings (shells) of electrons that vary from two to thirty two. In the electrical industry we are concerned only with the very outer ring known as the valence ring. The valence shell contains between one and eight electrons. The number of electrons in the valence ring determines if the atom is a conductor or an insulator. The octet rule in chemistry says for an atom to be stable, it must have eight electrons. In the case of sodium above, we could add seven electrons or remove one electron. It’s much easier to remove the one electron. In general a conductor is an atom with one to three valence electrons. Copper, silver, and gold all have one valence electron. Iron, cobalt, nickel, and zinc have two, aluminum has three. Gold, silver, and copper are the best conductors. In electric wire we use mainly copper and aluminum. All are metals and besides being good electrical conductors, are also good heat conductors. An alloy consists of mixture of two or more metals. Common alloys include brass, bronze, pewter, and stainless steel. Alloys have properties superior to the metals that went into them. Brass (mixture of copper and zinc) is harder and more durable than either copper or zinc. Stainless steel (iron mixed with carbon, chrome and nickel) resists rust and is stronger than iron alone. Tin mixed with lead makes electrical solder. The electrical conductivity of an alloy falls between the metals that went into them. Brass is a better conductor than zinc, but not as good as copper. In copper wire we use pure copper to make the best conductor. The sodium above is a metal and would be a good conductor, but can’t be used because it burns in the presence of air or water. Silver is a better conductor than copper, but the cost is too high to use for wire. A common alloy in the electrical industry is chrome, an alloy of chromium and nickel. It’s used to make heating elements.


InsulatorsChemical elements with five to eight valence electrons are insulators. Many of these elements are gases (oxygen, nitrogen, argon, helium, etc.) or unstable solids such a sulfur or phosphorus. In the real world insulators are often molecules and compounds. (Mixtures of atoms.) Common insulators include glass, rubber, mica, plastics, wood, etc. They are insulators because their chemical structures tightly bound the electrons. Think of it as electron super-glue. If enough force is supplied, electrons can be stripped away, but often cling to the surface. Typical is walking across a carpet and getting a minor shock when one touches a metal doorknob causing an electric discharge. We call this static electricity. Lightning is also static electricity.

SemiconductorsA third class of materials is called semiconductors. They are neither good insulators nor good conductors, but somewhere in between. They have four valence electrons and include Carbon, silicon, and germanium. Silicon and germanium are used to make semiconductor devices such as diodes and transistors while carbon is not. Carbon in its diamond form is an insulator and in its graphite form is a conductor used to make motor brushes.


Electron FlowElectricity is the flow of electric charges. In this discussion we will stick to solids. This is accomplished by using some form of energy to knock a valence electron off one atom into the next atom to the next, etc. Think of this as a water pipe full of Ping-Pong balls where a ball is inserted into one end and a ball falls out the other end. Energy is transferred from one ball tothe next ball down the line. Metals have loose valence electrons and require little energy to dislodge them. The electrons are so tightly bonded in insulators massive amounts of energy are needed to dislodge an electron. The process often destroys the insulator. Electron flow goes from negative (-) to positive. (+) In this class we will use conventional flow.Although it has been established that the electron theory is probably correct, the conventional current theory is still used to a large extent. There are several reasons for this. Most electronic circuits use a negative ground or common. When this is done, the positive terminal is considered to be above ground, or hot. It is easier for most people to think of something flowing down rather than up, or from a point above ground to ground. An automobile electrical system (negative ground) is a good example of this type of circuit. Most people consider the positive battery terminal to be the “hot” terminal.

Various symbols for grounds.

Do not assume they are connected to each other or are always the same! Many of the people that work in the electronics field prefer the conventional current flow theory because all the arrows on the semiconductor symbols point in the direction of conventional current flow. If the electron flow theory is used, it must be assumed those current flows against the arrow. In the military and here I'll use electron flow.


Electrical measurements generally use engineering (and scientific) notation. Engineering notation differs from the standard metric in that it uses steps of 1,000 instead of steps of For example if we have a 10 kilo-ohm (10k) resistor and want to convert to ohms, we multiply by 1000 to get ohms, in this case 10,000 ohms. If we have a 27,000-ohm resistor and want to convert to kilo-ohms, we divide by 1000 to get 27 kilo-ohms or 27k. Another example is if we have .5 volts, we would change to milli volts (mV) by multiplying by 1000 to 500 milli volts (mV) or often expressed as 500mV. If we want to change milli volts to volts we divide by 1000. Note that milli amps (mA) is used in electronics more than electricity.

Ohms LawOhm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One amp flowing through one ohm produces one volt. (I) Current is what flows on a wire or conductor like water through a pipe. Current (electrons) flow from negative to positive through a conductor. Current is measured in (A) amperes or amps.


A coulomb is a quantity measurement of electrons. One coulomb equals 6,250,000,000,000,000,000 electrons. The definition of one amp (A) is one coulomb per second passing a point. The letter I, stands for intensity of current flow, or A, which standsfor amps, are often used in Ohm's Law formulas. (E) Voltage is the difference in electrical potential between two points in acircuit.It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.Voltage is the potential energy of an electrical supply stored in the form of an electrical charge, and the greater the voltage the greater is its ability to produce an electrical current flowing through a conductor.This energy has the ability to do work. Voltage is sometimes called ElectromotiveForce, (EMF) with the circuit symbol V, although E is mostly used today. Here I'll use E. (R) Resistance (electrical friction) determines how much current will flow through a component. Resistors are used to control voltage and current levels.Resistance is measured in Ohms, using the Greek symbol Omega. (Looks like an upside-down horseshoe.)An ohm is a measurement of resistance (R) in an electric circuit. The letter R is used to represent Ohm's Law formula.The watt (W) is a measurement of power in an electrical circuit. The letter P represents power in Ohm's Law formula while Watts is the unit of measurement. (P) Power is the amount of current times the voltage. These are the main formulas to know:

Also: P = I * V


ResistorsResistors are used in two main applications: as voltage dividers and to limit the flow of current in a circuit. The value of a fixed resistor cannot be changed. There are several types of fixed resistors, such as composition carbon, metal film, and wire wound. Carbon resistors (not much used today) change their value with age or if overheated. Metal film resistors never change their value, but they are more costly than carbon resistors.

Fixed resistors

The advantage of wire wound resistors is their high power ratings. Resistors often have bands of color to indicate their resistance value and tolerance. Resistors are produced in standard values.


ThermistorsA thermistor is a resistor that changes value with temperature. The resistance decreases with increased temperature, we say the thermistor has negative temperature coefficient. If the resistance increases with an increase in temperature, we say the thermistor has a positive coefficient. Thermistors can be used to measure temperature.

Photocells (also called photo resistors) decrease resistance in the presence of light based on light intensity. They are used to measure light intensity or as an “electric eye” in streetlights.

Variable resistors (or potentiometers) can change their value by turning a knob, etc. These are the older style “volume controls” used in consumer electronics.


The internal construction of a potentiometer has a slider attached to the shaft which when adjusted changes resistance in relation to the two outer terminals.

In the above circuit diagram a potentiometer is connected to a 12 volt DC source. As the control is adjusted the voltmeter will read 0-12 volts. Note the grounds donate a common connection.


Proper Use of a Multimeter

In measuring current with a multimeter the student has to understand how to attach the meter. When measuring current the ampmeter must be placed in series by breaking the electrical path and inserting the ammeter into the path. Note that an ammeter should never be placed across (parallel) to any component or the meter will be damaged or blow a fuse. An ammeter has a very low internal resistance. More on that later. This differs from a clamp-on ammeter that measures the magnetic field generated by electrical current flow. We will look more into that in the section on magnetics.To measure voltage the meter must be placed in parallel as shown above. Voltmeters have a high internal resistance.

Meters - Measuring CurrentAmmeter must be part of the circuit to measure the currentVOM – multimeter that measures E, I, R


Meters - Measuring VoltageVoltmeter measures across the circuit (in parallel to the voltage to be measured)

Meters - Measuring ResistanceOhmmeter: measures across the resistor (but be sure the circuit is not turned on “hot”).Puts in a known voltage and measures the current, so it requires a battery. If the circuit is energized, will give the wrong reading! Never leave a multimeter set at “ohms” – will run down its battery!


Ohms Law

Pictured above is the Ohms Law pie chart that has twelve formulas broken into four quadrants.

We have a power source and a load R1. Current will flow from negative to positive as shown by the arrows and the resistance of R1 will limit the current.Let’s look at several sample problems and how to solve them. For this class we will find all values including I in amps, V in volts, R in ohms, and P in watts. Note that with resistive loads AC and DC work the same.

Note there are no multiply or divide keys on a computer keyboard, so we use / for divide and * for multiply.Problem 1: An electric heating element has a resistance of 16 ohms and is connected to 240 volts AC. What is the current and how much heat is produced?How to proceed: First we ask, “What do I know?”We know the resistance R = 16 ohms. We know voltage V = 240. And we know our two formulas stated earlier as I = V/R and I*V = P.

First we find I: I = V/R = 240/16 = 15 amps. Now we find P (the heat produced in this case): P = I*V = 15*240 = 3600 watts.


Problem 2:A 480-volt circuit has a current flow of 3 amps. What is the resistance R and the power P?What do I know? V = 480 volts; I = 3 amps.P = I*V = 480*3 = 1440 watts.To find R we must transpose the two formulas: I = V/R or 3 = 480/R;Divide both sides of the equation by 480 (or multiply by 1/480) we get 3/480 = 1/R (the 480 cancel):This comes out to be .00625 = 1/R; now we take the reciprocal of both sides of the equation: the reciprocal of 1/R = R; reciprocal of .00625 = 1/. 00625 = 160ohms. (One can also use the reciprocal key on their calculator too.) Thus R = 160 ohms.For the student terrified of mathematics, we can use a pie chart. In our previous problem we knew V = 480 volts, I = 3 amps, and P = 1440 watts. Now we need to find R, we look at the formulas in the lower right-hand quadrant. Any of the three will work, but V/I is the easiest to use.R = V/I = 480/3 = 160. We get the same answer. Whether one wants to use math or the pie chart is an individual choice. Often we use both.

Problem 3:An electric motor has an apparent resistance (more on apparent resistance in AC) of 15 ohms. With eight amps of current, what is the voltage and power?What do we know? R = 15 ohms; I = 8 amps.Using the pie chart to find P (lower left quadrant) knowing both R and I we use I squared times R;P = (8*8) * 15 (do the 8 times 8 first); 64*15 = 960 watts.To find V (upper right quadrant) we can use I*R = 8*15 = 120 volts.


Series Circuits

Pictured is a typical series circuit such as Christmas tree lights. When we close the switch, the lamps will light up as current flows through the lamp filaments generating intense heat, which produces light.

Properties of series circuits:The current through each device in a series circuit is equal. In this case each light bulb has the same identical current through each individual filament. In we will assume each light bulb is 40 watts at 15 volts. Using I =P/V = 40/15 = 2.67 amps. The power source must supply 2.67 amps to power the circuit.

Failure of any one element in the string will break the current path for all devices in the string. If one light bulb burns out (opens), all of the lights would turn off regardless of the power switch. This is what happens to Christmas lights when a single bulb goes bad. Note that all of the voltage supplied to a series circuit will appear across the open element.

The sum of the voltage drops across each element in a series circuit equals the voltage supplied by the source. Let’s assume each of the eight light bulbs is rated at 15 volts. 15 volts times eight equals 120 volts. That is the voltage that must be supplied from the source to light up all eight light bulbs.

The power consumed by each element in a series circuit equals the total power supplied by the source. In this case let’s assume each light bulb uses 40 watts of power. 40 times eight equals 320 watts of power that must be supplied by the source.


The total resistance of a series circuit is the sum of the individual resistances. In the above example we have been using a string of 40-watt bulbs at 15 volts each. We use the formula V times V divided by P from the pie chart to get R = 5.625 ohms for each lamp. The total resistance of the circuit is 5.625 * 8 = 45 ohms. There is another way to check this to see if we are right. I = 2.67 amps and P = 320 watts. 2.67 * 2.67 = 7.13, so 320 divided by 7.13 = 44.88 ohms. This is a typical example ofrounding errors.) So I now know the original answer was correct.

In the previous example we used eight light bulbs in series and all had identical power, resistance, and voltage ratings. Allof the factors are directly related and depend on each other. So we had a nice uniform voltage drop and resistance from one circuit element to the next. In the figure above we have replaced the light bulbs with five resistors. These could be resistors, heating elements, lamps, etc. Here I will assume resistors.We are using a DC source and not an AC source. AC has no polarity but DC does. If one placed a DC meter across resistor 1 (red lead on the positive side, black lead to the battery side) we would read the voltage drop across the resistor. Reverse the meter leads and we will read a negative voltage, so turn the leads around.


The voltage across resistor 1 (R1) depends on the value of the resistor and the current through it. (Use the formula I*R fromthe chart.) For example if the resistance of R1 is 2000 ohms (2k) and the current 25 milliamps (mA), how do we solve the problem?

First convert milliamps (mA) to amps by dividing by 1000 to get .025 amps.Next multiply .025 by 2000 ohms (or 2k) to get voltage across R1 which is 50 volts. How much power does the resistor use? Multiply 50 volts times .025 amps we get 1.25 watts. Resistors come in standard power ratings such as one-eight watt, quarter watt, 1 watt, 2 watt, etc.We would have to use at minimum a 2 watt or higher else the resistor will overheat and fail.What about total power and total resistance? If all five resistors were the same value of 2k, it would be easy to multiply byfive. But here we have different values for each resistor. R2 = 3k; R3 = 1.5k; R4 = 1.2k; R5 = 2.2k. Note the current is identical through each resistor at .025 amp.

The voltage across R2 = 3000 * .025 = 75 volts and P = 1.875 watts or 1875 mW.The voltage across R3 = 1500 * .025 = 37.5 volts and P = .9375 watts or 937.5 mWThe voltage across R4 = 1200 * .025 = 30 volts and P = .750 watts or 750 mW.The voltage across R5 = 2200 * .025 = 55 volts and P = 1.375 watts or 1375 mW.Total P = 1.25 + 1.875 + .9375 + .750 + 1.375 = 6.1875 watts.Total V = 50 + 75 + 37.5 + 30 + 55 = 247.5 volts.Total R = 2k + 3k + 1.5k + 1.2k + 2.2k = 3.4k or 3400 ohms.

Check: total P = total V * total I = 247.5 volts * .025 amps = 6.1875 watts.


One last thing to note is the voltage drop in a series circuit is proportional to resistance. The higher the resistance, the higher the voltage drops. So the highest value resistor (3k) had the highest voltage drop at 75 volts.

An application

On thepicture two separate series circuits. We have a photocell in series with a 1000-ohm (1k) fixed resistor. If we connect meter from ground to point “V” what will our meter read? Remember a photocell decreases resistance in the presence of light. Let’s assume VCC = +12 volts while ground is negative.

Let’s assume in the dark the photocell resistance = 11,000 ohms (11k). We have a total circuit resistance of 1k + 11K = 12k (which we will call Rt) which gives us a current of 12 volts divided by 12,000 ohms = .001 amp or 1 mA.In the left-hand circuit the voltage drop across R1 (or VR1) = 11,000 ohms *. 001 amps = 11 volts. The same current flow through R2 so VR2 = 1000 ohms *.001 amps = 1 volt. As in all series circuits the voltage drops when added together should equal the source voltage. 1 volt + 11 volts = 12 volts.


So the voltmeter on the left-hand circuit will read 1 volt while it will read 11 volts on the right-hand circuit. Now we shine a bright light onto the photocell and its resistance drops to 1000 ohms. What will the meter read now? Our total resistance (Rt) = 1000 ohms +1000 ohms = 2000 ohms. (2k)

Our current = 12 volts / 2000 ohms = .006 amp or 6 mA. VR1 = 1000 ohms *.006 = 6 volts. VR2 = 1000 ohms * 1000 = 6 volts. Now the voltmeter will read 6 volts on either circuit.

With the left-hand series circuit voltage increased with light intensity while it dropped on the right-hand circuit. By measuring the voltage across either circuit we can measure light intensity. This is exactly what light meters did on older cameras. We could have easily replaced the photocell with a thermistor (to measure temperature or any kind variable resistance sensor and got the same effect.

Parallel Circuits


Pictured above is a typical parallel circuit with the light bulbs connected in parallel and all three in series with a fuse. Fuses and circuit breakers as current operated devices are always connected in series. See page 340 in the textbook.

Parallel circuits differ from series circuits in several important ways:

The voltage across each element is a parallel circuit is identical. If the voltage from the generator is 120 volts, then the voltage measured across each light bulb would be 120 volts.

The current through each element of a parallel circuit is different. In this case we could have a 120-watt, a 240-watt, and a 60-watt light bulb all connected to the same power source without one effecting the other.

The failure of one element in a parallel circuit will not affect the other elements. For example in household electric wiring a blown (open) light bulb in the kitchen won’t affect the living room.

The total current drawn from the generator equals the sum of the currents from each circuit element. From the examples above with three bulbs each at 120 volts, the 120 watt bulb draws 1 amp, the 240 watt bulb draws 2 amps, and the 60 bulb draws .5 amp, the total I = 1 + 2 + .5 = 3.5 amps. (Use P/V)

The total power drawn from the generator is the sum of the power drawn by each element. In the above example total P = 120 watts +240 watts + 60 watts = 420 watts. Check: divide 420 watts by 3.5 amps =120 volts.


The total resistance of a parallel circuit is always less than the least resistance. Using the examples above, the resistance of the 120 watt bulb = V divided by I = 120 volts divided by 1 amp = 120 ohms. The resistance of the 240 watt bulb = 120 volts divided by 2 amps = 60 ohms. The resistance of the third bulb = 120 volts divided by .5 amps = 240 ohms. To see if the above statement is correct, let’s divide the 120 volts by the total current (I) of 3.5 amps = 34.3 ohms. Note that the lower the resistance of an element in a parallel circuit the higher the wattage or power drawn from the generator, thus the 240 watt bulb has the least resistance. One final question: what size fuse should we use? Fuses also come in a number of sizes, so at 3.5 amps total we would have to use a fuse rating greater than 3.5 amps. 4 or 5 amps would be fine. 30 amps would be absurd because the idea is to blow the fuse before the wiring catches fire. Never replace a fuse with a value higher than the original!

The example is a simplified view of home electrical wiring. (120 volts) The wall outlets are wired in parallel. If one was to plug a 1200-watt hair dryer into one wall socket and a 1500-watt microwave into a neighboring wall socket, could a 20-amp breaker carry the load? The answer is no. 1200 watts at 120 volts = 10 amps. 1500 watts at 120 volts = 12.5 amps. Total = 22.5 amps. Also note the light bulbs are wired in series with a switch, but both are wired in parallel with the wall sockets and all are wired parallel with the panel box. This is called a combination circuit. Most electrical/electronic devices use combination circuits


As the circuit illustrates when resistors are wired in series, the total resistance is obtained by adding the resistor values


Test the Theory

In the case of parallel circuits if the resistors have the same value take the value of one resistor and divide by the number of resistors. Take two 1000-ohm resistors and wire them in parallel. Measure the resistance. Did the measured value match the expected value?

Test the TheoryFor resistors that are not the same we use the reciprocal formula. (Page 138 in the textbook.) If R1 = 1000 ohms, R2 = 2000 ohms, and R3 = 3000 ohms, calculate the total resistance. With the battery voltage at 12 volts, calculate on paper the current though each resistor and the total current in amps and milliamps. Then measure the current through each resistor to see if they match the current supplied by the battery. How do we attach an ammeter to check current?

Test the TheoryWire a 100-watt light bulb in series with a 40-watt light bulb. Apply power, which bulb is brighter? Why? Measure the voltage drop across each individual light bulb. Do the measured values when added equal the voltage supplied?


Resistor Information

Resistor symbols differin different countries

More resistors symbols

How to read a color code on a resistor. For example a 3.3k (3300) ohm resistor color code would be orange-orange-red or 33 * 100. What is the color-codes for a 1k, a 2k, and a 3k resistor?


Measuring Resistance, In Circuit and Out

The resistor is the fundamental electronic component. By resisting the flow of electrons in a simple and predictable way, a resistor allows the designer to easily manipulate currents and voltages—and currents and voltages are what circuits are all about.

Before You MeasureThe resistance, or simply the “value” of a resistor determines how it will influence the circuit to which it is connected. You need to know the resistance of your resistor—sometimes the approximate value is fine--but sometimes you need precision. The value of a resistor is usually indicated on the component itself, with either old-fashioned colored bands or printed numerals. But these are nominal values, meaning that the actual resistance can be a certain percentage higher or lower than this indicated value. If the tolerance of the resistor is 10%, for example, a “1000 ohm” resistor could actually be anywhere between 900 and 1100 ohms.

Why Measure?So if the resistance value is labeled right there on the resistor, why would you need to measure? There are two reasons: • You may not be able to confidently determine the resistance from the label—maybe the component is old and the label is

faded, or maybe you don’t understand the color code. • You may need to know the exact value of a specific resistor, not the nominal value. A high-precision circuit requires high-

precision components. If the reference voltage for an analog-to-digital converter is determined by an external resistor, you need to know the exact value of that resistor in order to accurately interpret your digitized measurements


The Easy WayThe most common and simplest way to measure resistance is with a digital multimeter, or DMM. This indispensable device knows all about Ohm’s law and is happy to do the work for you: when you connect the terminals of the resistor to the two probes, it supplies a known current, measures the resulting voltage drop, and calculates the resistance. The trouble is, this approach only works if you can take your resistor out of the circuit; the DMM’s reading cannot be trusted if the resistor’s terminals are connected to other components. So if you need to know the value of a resistor that cannot be isolated from other components, you will have to be more creative.


Web Site to do Resistor Calculations for you

https://www.eeweb.com/toolbox/4-band-resistor-calculator/


https://www.eeweb.com/toolbox/6-band-resistor-calculator

Or

https://www.elprocus.com/online-resistor-color-code-calculator/



https://www.eeweb.com/toolbox/6-band-resistor-calculator

https://www.elprocus.com/online-resistor-color-code-calculator/


FORMULAS, EQUATIONS & LAWS

Symbolic: E =VOLTS ~or~ (V = VOLTS) P =WATTS ~or~ (W = WATTS) R = OHMS ~or~ (R = RESISTANCE) I =AMPERES ~or~ (A = AMPERES) HP = HORSEPOWER PF = POWER FACTOR kW = KILOWATTS kWh = KILOWATT HOUR VA = VOLT-AMPERES kVA = KILOVOLT-AMPERES C = CAPACITANCE EFF = EFFICIENCY (expressed as a decimal)

DIRECT CURRENT:

AMPS= WATTS÷VOLTS I = P ÷ E A = W ÷ V

WATTS= VOLTS x AMPS P = E x I W = V x A

VOLTS= WATTS ÷ AMPS E = P ÷ I V = W ÷ A

HORSEPOWER= (V x A x EFF)÷746

EFFICIENCY= (746 x HP)÷(V x A)


AC SINGLE PHASE ~ 1ø AMPS= WATTS÷(VOLTS x PF) I=P÷(E x PF) A=W÷(V x PF)

WATTS= VOLTS x AMPS x PF P=E x I x PF W=V x A x PF

VOLTS= WATTS÷AMPS E=P÷I V=W÷A

VOLT-AMPS= VOLTS x AMPS VA=E x I VA=V x A

HORSEPOWER= (V x A x EFF x PF)÷746

POWERFACTOR= INPUT WATTS÷(V x A)

EFFICIENCY= (746 x HP)÷(V x A x PF)

AC THREE PHASE ~ 3ø AMPS= WATTS÷(1.732 x VOLTS x PF) I = P÷(1.732 x E x PF)

WATTS= 1.732 x VOLTS x AMPS x PF P = 1.732 x E x I x PF

VOLTS= WATTS÷AMPS E=P÷I

VOLT-AMPS= 1.732 x VOLTS x AMPS VA=1.732 x E x I

HORSEPOWER= (1.732 x V x A x EFF x PF)÷746

POWERFACTOR= INPUT WATTS÷(1.732 x V x A)

EFFICIENCY= (746 x HP)÷(1.732 x V x A x PF)


Basic Electricity Safety Update:

Qualified Employees:Have training to avoid the hazards of working on or near an exposed electrical partsAre trained to work on energized electrical equipmentCan lock out or tag out machines and equipmentKnow the safety‐related work practices of the OSHA regulations and the NFPA standards, includingrequired PPEQualified employees have the training to know how to recognize and avoid any dangers that might be present when working on or near exposed electrical parts.Qualified employees know how to lock out and tag out machines so the machines will not accidentally be turned on and hurt the employees that are working on them.Qualified employees also know safety‐related work practices, including those by OSHA and NFPA, as well as knowing what personal protective equipment should be worn.

Affected Employees:Can work on a machine or piece of equipmentCannot work on electrical devicesDO NOT have the training to work on energized partsIf you are not qualified to work on electrical equipment, but are still required to work near electrical equipment, you are considered to be an affected employee.Safe working practices for affected employees are just as important as practices for qualified employees.


As an affected employee, you will be working on machines and other pieces of equipment, but not on electrical devices. You will, though, still be working around electrical parts that can kill you.Since you do not have the training to work on these parts, you are considered to be an affectedemployee because just being near some of these parts can be very dangerous.

What Is Electricity?Electricity is a type of energyElectricity is everywhere: motors, heaters, lights, speakersTo help you understand what an arc flash is, we will start by introducing electricity.Electricity is a type of energy. In your home you can see electricity being used everywhere.Electricity can make the motors of a washing machine, refrigerator, or blender spin.Electricity can heat up rooms with a heater, dry your clothes in a dryer, and toast bread in a toaster.Electricity can also be used to light up rooms, create sounds in speakers, and run a computer.

How Is Electricity Used In Manufacturing?Lights in the building, Motors, Welders, Control devicesIn a manufacturing setting, electricity is used even more. Electricity provides power to practicallyevery piece of equipment in a manufacturing facility.It is used to light the buildings, provides power to electric motors, gives the power needed to runa welder, and also provides the control power needed so an operator can run a piece ofmachinery from a distance.


ElectricityElectricity is the flow of energy from one place to anotherA flow of electrons (current) travels through a conductorElectricity travels in a closed circuitWhen you think of electricity you should think of it as a form of energy that flows from one place to another.Electricity involves the flow of electrons in a closed circuit through a conductor. But don’t worry if you don’t understand all of this yet. We will cover each of these items and more in detail as we progress through the training.

Electric Charge, Static Electricity, and Current ElectricityWhen an electric charge builds up in one place it is called static electricityElectricity that moves from one place to another is called current electricityThe electrons that are involved in electricity have an electric charge.When an electric charge builds up in one place it is called static electricity.We can understand electric charge by looking at someone touching a static electricity generator.In the picture her hair is standing up because of an electric charge that builds up in her hair.The electricity that builds up when you scoot your feet on the floor on a cool, dry day and shock someone is also because of static electricity.Lightning is another spectacular display of static electricity.Electricity that moves from one place to another is called current electricity.An electric current, then, is the flow of electric charge. Electric currents move through wires to make motors spin, lights light up, and heaters warm a house.


ConductorsConductors allow the flow of electricitySilver, Copper, Gold, Aluminum, Iron, Steel, Brass, Bronze, Mercury, Graphite, Dirty water and ConcreteElectric current flows through electrical conductors.A conductor is anything that allows the flow of an electric charge. A common conductor you probably already know about is copper. Copper wires conduct electricity.Copper, as well as aluminum, is often used to deliver electric current to machines in manufacturing settings as well as any electric appliances at home.As you can see from the slide, most metals are good conductors. Some of the conductors listed that might surprise you are dirty water and concrete.

InsulatorsInsulators do not normally allow the flow of electricityGlass, Rubber, Oil, Asphalt, Fiberglass, Porcelain, Ceramic, Quartz, (dry) cotton, (dry) paper, (dry) wood, Plastic, Air, Diamondand Pure water.An insulator is just the opposite of a conductor. It does not allow the flow of an electric charge and keeps electricity from getting to unwanted areas.The plastic insulation around a copper wire is an example of an insulator. Others you might not have thought of are glass, oil, and pure water.As we go further into the training we will find out that electricity can flow through insulators under certain circumstances.An arc flash is one of the circumstances where air actually acts as a conductor.


Three Basic HazardsShock/Electrocution, Arc Flash and Arc BlastNow that you have a fairly good idea of what electricity is, let’s go over some of the hazards involved in working around electrical devices.They include shock, electrocution, arc flash, and arc blast.These hazards are present in any circuits over 50 volts.

Dangers of Shock and ElectrocutionElectricity can kill youMost deaths are preventableWhile electricity is useful, it can also hurt or kill you. Accidents from electricity happen far moreoften than you would like to think.Electricity has long been recognized as a serious workplace hazard, exposing employees toelectric shock, electrocution, burns, fires, and explosions.If a person is killed by getting shocked, then they are considered to have been electrocuted.In 2009, 268 workers died from electrocutions at work, accounting for almost 5 percent of allon‐the‐job fatalities that year, according to the Bureau of Labor Statistics.30,000 victims each year are lucky enough to only get shocked and not killed.What makes these statistics more tragic is that most of these fatalities and injuries could havebeen easily avoided by using safe work practices such as making sure that electrical equipmentis locked out, tagged out, and de-energized.


Scare PicturesWhile no one likes seeing pictures of injuries, we do need to show you just how devastatingelectrical injuries can be. These next five pictures are from OHSA’s web site.

Entrance Wound

When you are shocked, electricity travels through your body. Severe injuriescan show up where the electricity enters and leaves your body.This picture shows how the resistance of the body turns electricity into heat.This man was lucky to survive since the electricity entered his body so close tohis spinal cord.


Exit Wound

Here is a picture of where electricity exited a man’s foot.The charred hole is just the surface of the wound. As the electricity traveled through his foot, it created lots of heat and burned the inside of his foot so much that the doctors had to cut the foot off a few days after the injury.

Internal Injuries

In this picture, the worker was shocked by the metal tool he was using, such as a pair of pliers. The resistance of the metal made it heat up, causing the burnt skin below his thumb.The visible part of the wound looks bad, but there were severe internal injuries that were not immediately visible. These internal injuries were from the current flowing through his hand.


This is the same hand a few days later. As you can see there was so much damage that skin had to be sliced open to make room for all the swelling.The injury below the burn from the metal tool was caused from heat as well, but the heat in these areas was from the current going through his hand, not the heat of the tool.

Involuntary Muscle Contraction

In this picture, a worker fell and grabbed a power line to catch himself.There was so much current in his hand that his first two fingers were mummified and had to be removed.His hand is bent like this because as the tendons in his hand were cooked, they shrunk, painfully drawing up the workers hand.


Getting ShockedYou become part of the circuit.The current traveling through your body can kill you.Most people know what an electrical shock is. The pictures gave you a good idea of what can happen when you are shocked, but let’s go over some of the details of shock and electrocution some more.Electric shocks can be harmless like getting shocked when touching a doorknob after walking on carpet, or a shock can be deadly.An electric shock occurs when current passes through the body. The current can cause damage to muscles (including heart muscles), the nervous system, and other parts of the body.Getting shocked means your body is becoming part of the circuit. You become a conductor because of the current running through your body.

Causes of Electric ShockTwo different live wires A live wire and a ground wireThere are many ways that a person’s body can become part of an electrical circuit and getshocked.You will get an electric shock if you touch a live wire and an electrical ground or if you touch a live wire and another wire of a different potential.So, if you touch any live wire and then touch either a different live wire or a ground wire, you can get shocked.Many have been shocked at home, but at the work place, voltage and current are much higher creating a greater chance of getting hurt.


ElectrocutionElectrocution means death by electricity.Less resistance leads to more current passing through the body.Affected employees must pay special attention to electrical hazards that can cause electrocution because they often work near electrical circuits.Electrocution, then, occurs when a person is shocked with enough current that they die. This is because the large amounts of current flowing through the body can cause severe internal andexternal injuries.The chances of being electrocuted go up when working around water or when you are sweating OR when you are not wearing the proper protective clothing.

Shock Can Occur Without Touching Live PartsCircuits can be completed through the airIf you think you have to actually touch live wires to get shocked, you would be wrong. Just as static electricity can shock you even before you touch a door knob, electric currents can reach out and shock you if your body gets in a position that it could become part of the circuit.This will be important to know when learning about arc flash because, in an arc flash, the circuit is completed through the air, not just through wires.This is because, even though air has insulating values, it has its limits. If there is enough voltage, the circuit can be completed just by going though the air.For example, with live parts at 72,500 volts, you must keep body parts and other grounded items more than two feet away to avoid current flowing through you because at that high of voltage, the circuit can be completed even through a foot of air.


How Shock Is Measured

Condition Resistance (ohms)Dry Wet

Finger Touch 40,000 ‐ 1,000,000 4,000 ‐ 15,000Hand Holding Wire 15,000 ‐ 50,000 3,000 ‐ 6,000Finger Thumb Grasp 10,000 ‐ 30,000 2,000 ‐ 5,000Hand Holding Pliers 5,000 ‐ 10,000 1,000 ‐ 3,000Palm Touch 3,000 ‐ 8,000 1,000 ‐ 2,000Hand around1 1/2 pipe 1,000 ‐ 3,000 500 ‐ 1,500Hand Immersed ‐ 200 ‐ 500Foot Immersed ‐ 100 ‐ 300As you can see from this chart, wet, sweaty conditions can be much more dangerous than dry conditions because water and sweat decrease the resistance to electricity, allowing more current to flow through the body when someone is shocked or electrocuted.It always makes good sense to stay away from energized parts, but especially so when conditions are wet.This is why electricians are required to wear gloves and use special tools when working on electrical equipment. The proper clothing and tools keep the resistance through their body high enough to keep from getting shocked.Other factors other than water or sweat will determine the resistance of someone being shocked.


Resistance will often depend on the path of the circuit through the body. A shock from one finger to another finger on the same hand will probably provide less resistance than a shock traveling from one hand to the other or from a hand to the ground through a foot.In any situation where the circuit has a chance to go through the heart, the dangers can be life-threatening.As you’re looking over the chart, notice how the wet situations offer less resistance than the dry situations. This is because current will flow through dirty water and sweat much more easily than through air and dry skin.Also, grabbing a wire would be much more dangerous than just barely touching a wire because more of your skin would be in contact with the wire.Regular metal tools also increase the chance of getting shocked. This is why electricians often have specialized tools for working on electrical equipment.

How to Avoid Shock HazardsDo not work on energized (live) equipmentStay away from electrical wires on the groundNever open an electrical panelAvoid working around water or wet locationsKeep work areas clean and tidyThe best way to keep from getting shocked is to stay away from electrical shock hazards.


Obviously you should never work on live or energized electrical equipment, not only because it is dangerous, but also because you are not qualified to work on the equipment.Another hazard involves live electrical wires in the wrong place. So if you see wires lying on the ground, do not go near them and tell your supervisor immediately.Since you will often have to work near electric panels, make sure to never open them. Opening the panel increases the chances of getting shocked or setting off an arc flash.Another hazard is water. Although sometimes it may be unavoidable, try to never work in wet areas that are near electrical equipment.Keeping your work area clean and organized can help you spot electrical hazards that you might otherwise miss in a messy work area. If you need to clean a work area that is disorganized and dirty, be very careful so no unseen hazards will hurt you.

How to Avoid Shock HazardsNever use a damaged outletNever use a damaged electrical cordNever use a cord with the ground prong missingDo not plug too many things into one outletStay alertEven when you are not working around high voltage equipment or electrical panel boxes, shock hazards still exist.Damaged outlets should never be used. If you see a damaged outlet or suspect an outlet might be damaged, stop using it and notify your supervisor immediately.The same goes for cords and plugs. If you see an electrical cord that looks worn out, it might have exposed wires. Also plugs that are damaged might not be properly grounded, increasing the chances of getting shocked.


Another possible hazard is having too many items plugged into the same outlet or on the same circuit breaker. Most often, the circuit breaker will safely open the circuit, but the sudden loss of electricity to electrical equipment could still cause injuries.Above all, just stay alert. Always be on the lookout for hazards and be prepared to stop working, protect those around you, and get help to take care of the situation as fast and as safely as you can.

Arc FlashWhat Is An Arc Flash?

An arc flash is a short circuit through the air in an electrical panel box or any other piece of energized electrical equipment. Air, as you have already learned, is normally an insulator, but with a high enough voltage, a slipped tool, or a panel box that is dirty, the circuit can be completed, causing a short.

When the short happens and the circuit is completed through the air, the air breaks down to where it offers little‐to‐no resistance to the flow of electricity.Remember, this is what a short circuit is. A short circuit will have almost zero resistance and will have very high levels of current. The high current is what is responsible for the arc flash.The tremendous amounts of energy released in an arc flash make for a very bright, very hot, andvery loud explosion.


Arc Flash vs. Safely Completed CircuitsHigher than normal currentsNow in a safely completed circuit, such as when a motor turns on a manufacturing line, the circuit is complete, just like in an arc flash, but a safely completed circuit has a load on the circuit offering resistance.So in a safely completed circuit, the resistance affects the current in the circuit, keeping the current under dangerously high levels.Think of a lamp plugged into the outlet of your house. When you turn it on, the circuit is completed, but the light bulb has resistance, so the current stays within safe limits.If you were to stick a paper clip in an outlet, the circuit will also be completed, but this time it will be a short circuit because the metal paper clip offers very little resistance to the flow of electricity.By the way, NEVER stick a paper clip into an electrical outlet. It is dangerous, and if you do it you will receive an electric shock or worse.

High Voltage Short CircuitA short circuit, as shown in this next video, does not have a load providing resistance. The arc that forms goes right through the air with little‐to‐no resistance.The same thing happens in an arc flash. The circuit is completed straight through the air.http://www.youtube.com/watch?v=PXiOQCRiSp0&feature=relatedOr Jacob's Ladder_ 500kV Switch Opening - YouTube (360p) in Video file

http://www.youtube.com/watch?v=PXiOQCRiSp0&feature=related


Where Does An Arc Flash Occur?Electrical panel boxCopper cablesLow voltage, high currentTo understand how an arc flash occurs, lets create an imaginary arc flash.To create an arc flash, a small piece of copper wire is placed between two of the wires coming into a three phase panel box. When the power is turned on, the small metal wire quickly vaporizes because of the high current and allows the air to break down between the two copper cables, decreasing the resistance and allowing dangerous levels of current to flow in a circuiteven after the small wire is gone.The larger copper cables will also vaporize, adding to the explosive power and brightness of the arc flash.Arc flashes can occur on any high voltage electrical equipment, not just in panel boxes.

Arc Flash Test VideoIn this next video, you will see how scientists create arc flashes in order to study them.

View “Arc Flash PPE Laboratory Testing Video - YouTube (360p)” in Video file


What Causes An Arc Flash?

Slipped tools or handsFalling partsDust, water, corrosion, oilAnimalsSometimes there is no known cause

When arc flashes occur by accident, they can sometimes be caused much like the way they are made on purpose.An accidental slip of a tool, a loose part, or even your hand touching live parts can provide the start the current needs to jump from one cable to the next.Loose connections in the electrical equipment, improper installation, and parts that break and fall are other possible triggers.Dust, water, impurities, contamination, corrosion, oil, and grease can also provide a starting route for the short circuit.Even animals or bugs can get into electrical devices and start an arc flash.Typically there is a reason for arc flash accidents, although we may not always know what it was.The unpredictable nature of arc flash accidents is why it is so important to know about them and stay away from dangerous situations.


What Happens During An Arc Flash

We have already mentioned some of the dangers of an arc flash, but let’s cover them more fully now.An arc flash is brighter than the sun, hotter than the sun, sends metal pieces flying away from the explosion at over 700 miles per hour, and is louder than a jet.

Bright LightSkin damageBlindnessThe bright light from an arc flash can cause severe skin damage, although you might not notice it since your skin would probably be burned so much from the extreme heat.Your eyes, though, even if wearing safety glasses, can receive enough blinding light in that short instant that you will never be able to see again.Going blind is just the first of many injuries an arc flash can give you.


Hot TemperaturesWelding arc = 3,000° F (1648.89 °C)Sun = 9000° F (4982.22 °C)Arc Flash = 35,000° F (19426.67 °C)

When an arc flash occurs, it gets really hot, some of the highest temperatures known to man.Just to show you how hot the 35,000 degrees Fahrenheit of an arc flash are, let’s look at a couple of items we know are hot.The temperature of welding arc is 3000° F. That is hot enough to melt and fuse together metal.The temperature of the Sun is 9000° F. That is hot enough for atomic fusion.The temperature of an electrical arc flash, though, can reach 35,000° F. It is difficult to really understand how hot that is and how destructive it can be, but luckily arc flashes don’t last very long.But you can get severe burns from the heat of an arc flash even though it lasts only for a fraction of a second.The chances of getting severely burned can be reduced by wearing the proper protective clothing. We will go over the selection of personal protective clothing, or PPE, later in the training.

Large ExplosionVaporized copper expands to 67,000 times its original sizeMetal flies toward you at 700 miles per hour (1126.54 km per hour)The intense heat from an arc flash can cause solid copper cables to change to liquid and then to vapor almost instantly.When copper vaporizes, it expands to 67,000 times its original size, this leads to the large explosion ‐ a very large explosion.The explosion creates a pressure wave sending shrapnel (such as equipment parts flying like an exploding grenade) hurling at high speed (over 700 miles per hour).


Very LoudYou can lose your hearingEar plugs might not helpSince the explosion happens so fast, the quickly moving air can damage your ear drums, causing a worker near the blast to become deaf…never being able to hear again.Severe arc blasts will have a noise level of more than 140 decibels at a distance of two feet away.Most ear plugs provide effective protection up to about 105 dB Regular ear plugs, then, do not provide adequate protection from arc flash accidents.

Arc Flash/Arc BlastThey always occur togetherAn arc flash always causes an arc blastYou will often hear the terms arc flash and arc blast used together because they always happen together.The bright light and high temperature is the arc flash. The explosion and the loud blast is the arc blast.For this training, though, we will continue to use arc flash for the entire event: light, heat, sound, and explosion.


Arc Flash VideosLet’s look at a couple of videos of actual arc flash accidents to see just how fast they can happen and how explosive they can be.

View “Arc Flash Fatality Video.wmv - YouTube (360p)” is Video file

As you can see the doors are open on this energized equipment.These circuit breakers are normally motorized. In most cases the doors are closed when opening and closing a breaker.If the door must be open, the bus or bus bar, which is a thick strip of copper or aluminum that is used to carry very large currents or distribute current to multiple devices within switchgear or other equipment, should be de‐energized before working on it. The worker does not have the proper PPE to be working near exposed live equipment.Notice the piece of test equipment on the floor. There must be a problem with the motor, and it looks like they are trying to close the breaker manually.The second worker, possibly the supervisor, gives the worker the OK to proceed just before the explosion.


Arc Flash Is UnpredictableEvery worker should assume the worstAnother item the test acknowledged is the highly unpredictable nature of arc flash accidents.The report stated “Workers and equipment may be at risk from electrical arc, even at times when codes, standards, and procedures are seemingly adequately addressed” meaning that even if everything is done right, an arc flash can still occur.They also advised that “workers should ‘assume the worst’ and use available personal protective equipment.”

Approach boundariesFlash protection boundaryLimited approach boundaryRestricted approach boundaryProhibited approach boundaryThe shock boundaries are calculated based on the amount of voltage being supplied to the equipment. The flash protection boundary requires more data.While the amount of current and the how long the arc flash lasts are the two big factors to consider when figuring out how severe an arc flash will be, how bad you get hurt also depends on how close you are to it.Just a few inches could be the difference between life and death when close to an arc flash.If a very large arc flash accident happens and no one is near it, no one gets hurt. This is why arc flash boundaries are so important.The four common boundaries around electrical hazards are the flash protection boundary, the limited approach boundary, the restricted approach boundary, and the prohibited approach boundary.


Arc Flash Boundary Table

Specific Restricted Areas and Boundaries for the Company InvolvedThis will change for each company and will be 5 to 10 minutes long, or will be deleted if the company requests so.


Calculating Arc Flash HazardsAvailable current and voltsTimeDistancePPEWe have already mentioned four things that contribute to how bad you are hurt in an arc flash accident: the available current and voltage, how long the arc flash lasts, how far away you are from the arc flash, and what type of personal protective equipment, or PPE, you are wearing.You are responsible for making sure you are wearing the right PPE, but the arc flash boundaries will already be calculated for you and put on a label.The intensity of the arc flash can range from a small flash of light to an explosion. The available current and how long it takes for the short circuit to be broken are the two factors used in calculating the flash protection boundary.

Just A Fraction of A SecondArc flashes don’t last very long, but they are still powerful enough to killSince alternating current is what manufacturing companies use to power most of their equipment, arc flash incidents are sometimes measured in cycles.If a company is using 480‐volt, three‐phase AC at 60‐hertz and the short circuit stays complete for six cycles, then it lasted one‐tenth of a second.This is easily enough time to allow an explosion large enough to kill you even if you are up to 10 feet away.So just a tiny amount of time, then, is needed for an arc flash to cause horrible injuries to affected workers near a piece of electrical equipment.


Personal Protective Equipment (PPE)You can see how important clothing is to protecting your body from an arc flash by taking a piece of fabric, say from a t‐shirt, and putting it over your finger and touching it quickly to a hot iron. You will probably not feel any heat since you touched it for just a fraction of a second.Of course if you held your finger there for more than a second or two your finger would get burned and blister, but this is not what happens in an arc flash.In an arc flash, the temperature is much higher, but hopefully lasts only a short amount of time, sort of like quickly touching a hot iron – only at tens of thousands of degrees for the arc flash instead of a couple of hundred of degrees for the iron.When this level of heat is involved for such a short amount of time, the part of clothing or skin that does come in contact with the heat will be completely destroyed. Hopefully it will be your protective equipment and not your skin that is destroyed in the arc flash accident.This is one of the reasons why wearing personal protective clothing is so important. If something is going to get burned and destroyed, you want it to be your clothing and not your skin.

CaloriesCalories measure energy1.2 calories per centimeter squaredSame as holding your finger over the flame of a lighterWhen dealing with personal protective equipment, or PPE, you will often hear the word calorie.This “calorie” is the same you are used to hearing when talking about food.Its formal definition is “the energy required to raise one gram of water one degree Celsius at one atmosphere” or the amount of energy it takes to heat up a few drops of water one degree.


You will get second‐degree burns at 1.2 calories per centimeter squared per second.This might be a little hard to grasp, but think of it this way: One calorie per centimeter squared per second, is like holding your finger over the tip of the flame of a cigarette lighter for one second.This could easily give you a second degree burn.

When You Need To Wear PPEIf you…• Open electrical panels that have energized (live) conductors inside• Work on, install, or maintain energized conductors or equipment• Stand within about 4 ft. of an open electrical panel…you need to be qualified and wear the proper PPELet’s look at some situations where you would need to wear PPE for arc flash hazards.The first is if you need to open electrical panels that have energized or live conductors inside.As an affected employee, you will not have to do this.You would also have to wear the right PPE if you work on, install, or maintain energized conductors or electrical equipment.Again, only qualified employees need to do this type of work. As an affected employee, you will not do this type of work.What about the next one? Standing within four feet of an open electrical panel.Now you might be doing this, so although you will not be working on live equipment, you still might need to work in an area that will require you to wear arc flash personal protective equipment.


What PPE Do I Need To Wear?Clothing, Voltage‐rated gloves, Face shields, Full protection suits, Insulated blankets, Safety glasses and Ear plugs.Personal protective clothing includes not just cotton clothing and flame resistance clothing, but also includes voltage rated gloves, face shields, full‐coverage flash suits, and insulated blankets.Remember that any time you cross the arc flash protection boundary, you need to wear the proper PPE. This does not mean you will need to dress up in the full‐coverage flash suit every time you cross the flash protection boundary, but you will need some level of protection.When you go to work, you need to make sure to always wear cotton clothing. Materials like nylon or acetate will ignite and melt on your skin if an arc flash occurs, causing severe burns.You should also always wear safety glasses and ear plugs if you are working near moving parts.Let’s look over some of the different levels of protection to see what you would need to wear in different situations.

PPE Care and InspectionThe employee wearing the protective clothing and PPE must inspect them each time they need to wear them.If you notice any damage to any of the PPE, report it immediately. Do not use the damaged PPE and do not enter any flash protection boundaries until the PPE is repaired or replaced.Remember, if you are required to wear PPE, it is your responsibility to make sure it is in safe working order.Since you will probably not be trained in how to inspect PPE properly, you will have to ask for help if you need to inspect arc rated PPE.


Appropriate Tools for Safe WorkingTools are often made of metal, and metal is a good conductor.This makes metal tools potentially very dangerous around electrical hazards, unless the tools are properly insulated.Insulated tools, then, must be used whenever working on energized electrical equipment.Here is a picture of some insulated tools for working on live parts. Notice the double triangle symbol to show workers that this is an insulated screwdriver.Since you will not be working on energized equipment, you will not need to use insulated tools, but you should know what they look like since you might see them on the job.


Working Safely

Look for labelsLook for unlabeled hazardsAssume all equipment is live and energizedLook for lockouts and lock out box in control roomWear the right clothing to workUse PPE when needed

• Now that you have a good idea about what to look for when you see an arc flash hazard label, let’s go through some tips to make sure you continue to work safely around these hazards.

• Always be on the lookout for hazards, whether they are labeled or not.• Assume that all equipment is fully energized with electricity. Do not think that just because someone is working around an

electrical hazard that they have de-energized the equipment.• Also be aware of any equipment that is locked out or tagged out. Locking out and tagging out a machine makes sure no

one tries to energize a piece of equipment while someone else is working on it.• If you see a tag like the one shown in the picture, do not try to remove it. Only the person who locked out the machine

has the authority to turn it back on.• Also, wear the right clothing to work. PPE will be provided by the employer, but you should wear your own non‐melting

clothing, work boots, and safety glasses.


What To Do If An Arc Flash Occurs

To someone elseStay away from the explosionGet helpStay calmTo youGet away from the explosionGet helpStay calm

• If you are near an arc flash accident and see someone who is injured, don’t follow your instincts to rush in and save them. You might set off another arc flash and be killed. You will not be able to help if you are dead.

• What you should do is get help right away. The time it takes for a critically injured person to get help is crucial in helping them survive the accident.

• Let other workers know about the accident and get someone to call 911. If you are not trained in giving medical attention, do not try. Wait until someone who is trained shows up to help.

• It you are the one who is injured in an arc flash accident, try to get away and get help immediately. What will most likely happen is that you will automatically try to get away if you are still conscious and will probably not remember much.

• Also, stay calm. Hopefully you will be wearing the right protective clothing and the proper PPE.• If not, you might be in the 95 percent of all accidents that could have been prevented by working safety and wearing the

right protection.


Summary• Electrocution is a shock that kills• Pure water is an insulator, sweat is a conductor• Arc flashes are short circuits with low resistance and high current• Arc flash labels will help you stay away and wear the right PPE• Thanks for being so attentive today. To quickly summarize some of the things you have learned today, let’s go through a

few final points.• Electricity is powerful and can be dangerous. Be careful around it.• Electrocutions are shocks that kill you. Stay away from shock hazards, especially when you are sweating, since sweat is a

conductor of electricity even though pure water is not.• Arc flashes are short circuits that happen when no load or resistance is in a circuit and the circuit is completed through

the air, causing an explosion. The explosion is bright, loud, and hot.• Since an arc flash’s intensity is determined by the available current and how long it lasts, arc flash hazard studies are done

to figure out safety boundaries and PPE levels for each hazard.• The labels will be placed where you can see them so you can stay away or wear the right PPE so that the PPE is destroyed

in an arc flash instead of your skin.• Always keep in mind that no equipment is so important and no service so urgent that we cannot take the time to do

the job safely.


• Always keep in mind that no equipment is so important and no service so urgent that we cannot take the time to do the job safely.

• Always verify your test instruments.• Isolate power personally if repair is necessary.• Verify that no voltage is present before making any repairs.• Think about what you are testing and what you expect to find. Random probing with the test instruments can cause

serious mistakes for personnel and equipment.• Be aware of the mechanical dangers. What may happen when the machine is energized either normally or

abnormally?• Be certain any temporary work is absolutely safe.• Verify safe working order after completion. Remove all test jumpers and device defeats. Check all safety circuits before

returning the machine to normal service.• Use electrical “SAFTEY HOOK” to remove any person from electrical source and NEVER EVER TRY TO REMOVE A

PERSON BY HAND or REMOVE ELECTICAL SOURCE BY HAND.


Basic Test Equipment

Test instruments come in various types, shapes and sizes. The most common types of volt-ohm-meters are grouped in two categories, analog and digital. There is also a type of ohmmeter called a meg-ohm-meter that will be discussed later in this chapter.

The Analog Volt-Ohm-Meter (VOM)

Troubleshooting with an Analog VOMThe analog VOM is frequently used in conventional trouble-shooting but is becoming more obsolete due to digital multi-meters. The VOM can tell the trouble-shooter if voltage is present or not, and can also tell how much is present. At times this additional information can be helpful. There are some concerns to be aware of when using test instruments such as the VOM.Meter Damage - It is easy to overlook the range and function selected on a VOM. If the wrong range or function is selected, incorrect readings and/or meter destruction can occur.Calibration Errors - Most instruments of this type need periodic calibration. An instrument that is out of calibration can cause lost time and wasted efforts due to the incorrect readings.Expense - Initial cost of industrial quality VOM's is quite high. As with any precision instrument, extra care must be taken to protect it.


The Digital Multi-Meter (DMM)

Digital multi-meters (DMM) have generally replaced the analog-type multimeter (VOM) as the test device of choice for maintainers because they are easier to read, are often more compact and have greater accuracy. The DMM performs all standard VOM measurement functions of a-c and d-c. Some offer frequency and temperature measurement. Many have such features as peak-hold display that provides short-term memory for capturing the peak value of transient signals as well as audible and visual indications for continuity testing and level detection.To compare these two types of multi-meters, let us examine their pros and cons in more detail:

• Ease of reading. One of the greatest problems with an analog meter is the errors that occur due to the human factor when reading off the value from the many different scales. The thin analog needle against a calibrated scale is similar to the hands of a clock against the number scale indicating the hours.

When you look at an analog clock, you have to determine where the hands are, which number the hand is nearest to, andso on. With a digital clock, however, the time is read directly from a display. With the analog meter, the decoding of the scale is necessary, while the digital multimeter displays the magnitude, polarity (+ or -), and the units (V, A, or Α) on typically a four-or five-digit readout. A disadvantage of the digital multimeter is its slow response to display the amount on the readout once it has been connected in the circuit. To compensate for this disadvantage, most DMMs have a bar graph display below the digital readout, as shown in Fig. 2, showing the magnitude of the measured quantity using more or lessbars. A bar graph reading is updated 30 times per second while the digital display is updated only 4 times per second.


The bar graph is used when quickly changing signals cause the digital display to flash or when there is a change in the circuit that is too rapid for the digital display to detect. For example, a contact’s resistance changes momentarily from zero to infinity when a contact “bounces”. A DMM cannot indicate contact bounce because the digital display requires more than 250 milliseconds to update.A DMM set to measure voltage may display a reading before the leads are connected to a powered circuit. This is known as a “ghost voltage” and is produced by magnetic fields, fluorescent lights and such which may be in close proximity. These voltages enter the meter through the open test leads which act as antennae. These voltages are very low and will not damage a meter but can be confusing as to their source.

• Accuracy - DMMs are typically accurate to 0.01 % and have no need for a zero-ohms adjustment. Returning to the example of the analog and digital clock, a person reading the time from the traditional analog clock would say that the time is almost 12:30. The wearer of the digital watch, however, will be totally specific and give the time as 12:27. Similarly, an analog reading on a meter of about 7 V becomes 7.15 V with the far more accurate DMM.

• Price - Digital meters have complicated internal circuitry that is why the digital readout meters usually have a more expensive price tag than the analog readout multi-meters.

Fig. 2


When troubleshooting with the digital multimeter, the maintainer is able to “see” the situation and the problem within the circuit or system. Fig. 3 illustrates a typical auto ranging digital multimeter. Of course for the meter to be of any use it must first be connected to the circuit or device to be tested. Both leads, one red and the other black, must be inserted into the correct meter lead jacks. The black lead is connected to the meter jack marked COM or common. It is usually the lower right jack as in this illustration. (Be aware that not every meter has the same jack configuration.) The red lead is connected to either of the appropriate jacks depending on what the maintainer wants to measure; ohms, volts or amperes. The two jacks on the left are utilized when measuring current, either in the 300mA or the 10 ampere range.

The display shows other functions as well.• Low battery indicator• Annunciators show what is being measured (volts, ohms, amps, etc.)• Autopolarity indicates negative readings with a minus sign when the leads are connected incorrectly without any damage• Auto ranging automatically selects proper measurement range• One selector switch makes it easy to select measurement functions• Overload protection prevents damage to the meter and the circuit, and protects the user.

Fig. 3


Measuring resistance – Fig. 4 shows the steps that should be followed when measuring resistance. Remember that resistance measurements are carried out without the power being applied to the component under test, and resistance values can vary by as much as 20% due to the tolerance of certain resistors. Do not be misled if your meter reading is slightly different from the color band on the resistor. If a resistor’s value is off and exceeds the tolerance, the resistor should be replaced. A resistor will rarely short, but typically will open. If a resistor does open, the DMM display will flash on and off or display OL (open line) because the resistor has an infinite resistance.

1. Turn off power to the circuit2. Select resistance Ω3. Plug the black test lead into the COM jack and the red test lead into the Ω jack4. Connect the probe tips across the component or portion of the circuit for which you want to determine the resistance5. View the reading and be sure to note the unit of measure, Ω, KΩ, MΩ, etc.


Measuring voltage – Fig. 5 shows the steps that should be followed when measuring voltage. The measurement of both voltage and resistance is where the DMM finds its greatest utilization. For voltage and resistance measurement, the red lead is inserted into the V – Ω (volt or ohm) meter jack.

1. Select volts AC (V~), volts DC (V---), mvolts (V---) as desired2. Plug the black test lead into the COM jack and the red test lead into the V jack3. Touch the probe tips to the circuit across a load or power source as shown (parallel to the circuit to be tested)4. View the reading being sure to note the unit of measureNote: For DC readings of the correct polarity (+ or -), touch the red test probe to the positive side of the circuit, and the black test probe to the negative side of the circuit ground. If youreverse the connections, a DMM with auto-polarity will merely display a minus sign indicating negative polarity. With an analog meter you risk damaging the meter.


Measuring current – Fig. 6 shows the steps that should be followed when measuring current. The measurement of current is rarely performed when troubleshooting, as the circuit path has to be opened to insert the DMM in series with the current flow. However, if current is to be measured, the red lead is inserted into one of the ampere jacks, 10 amp (10A) or 300 milliamp (300 mA) input jack depending on the expected value of the reading.

1. Turn off the power to the circuit2. Disconnect, cut or unsolder the circuit, creating a place where the meter probes canbe inserted3. Select amps AC (A~), or amps DC (A---) as desired4. Plug the black test lead into the COM jack and the red test lead into 10 amp (10A) or300 milliamp (300mA) jack depending on the expected value of the reading5. Connect the probe tips to the circuit across the bread as shown so that all currentwill flow through the meter ( a series connection)6. Turn the circuit power back on7. View the reading being sure to note the unit of measureNote: If test leads are reversed a negative (-) sign will be displayed


Meg-ohm meterAn ordinary ohmmeter cannot be used for measuring resistance of multi-millions of ohms, such as conductor insulation. To adequately test for insulation breakdown, it is necessary to use a much higher potential than is furnished by an ohmmeter's battery. This potential is placed between the conductor and the outside surface of the insulation. An instrument called a meg-ohm meter is used for these tests. The meg-ohm meter is a portable instrument consisting of two primary elements.• A hand-driven DC generator G, which supplies the necessary voltage for making the measurement• The instrument portion, which indicates the value of the resistance being measured. The instrument portion is of the

opposed-coil type as shown above. Coils a and b are mounted on the movable member c with a fixed angular relationship to each other, and are free to turn as a unit in a magnetic field. Coil b tends to move the pointer counterclockwise and coil a clockwise.

• Coil a is connected in series with R3 and the unknown resistance RX to be measured. The combination of coil R3 and RX form a direct series path between the positive (+) and negative (-) brushes of the DC generator. Coil b is connected in series with R2 and this combination is also connected across the generator. There are no restraining springs on the movable member of the instrument portion of the meg-ohm meter. Therefore, when the generator is not operated, the pointer floats freely and may come to rest at any position on the scale.

• The guard ring intercepts leakage current. Any leakage currents intercepted are shunted to the negative side of the generator. They do not flow through coil a; therefore, they do not affect the meter reading. If the test leads are open-circuited, no current flows in coil a. However, current flows internally through coil b, and deflects the pointer to infinity, which indicates a resistance too large to measure. When a resistance such as RX is connected between the test leads; current also flows in coil a, tending to move the pointer clockwise. At the same time, coil b still tends to move the pointer counterclockwise. Therefore, the moving element, composed of both coils and the pointer, comes to rest at a position at which the two forces are balanced.


• This position depends upon the value of the external resistance, which controls the relative magnitude of current in coil a. Because changes in voltage affect both coil a and coil b in the same proportion, the position of the moving system is independent of the voltage. If the test leads are short-circuited, the pointer rests at zero because the current in coil a is relatively large. The instrument is not injured under the circumstances because the current is limited by R3.

• To avoid excessive test voltages, most meg-ohm meters are equipped with friction clutches. When the generator is cranked faster than its rated speed, the clutch slips and the generator speed and output voltage are not permitted to exceed their rated values. For extended ranges, a 1000-volt generator is available. When extremely high resistances, such as 10,000 meg-ohms or more, are to be measured, a high voltage is needed to cause sufficient current flow to actuate the meter movement.

• A good rule of thumb for megger motors, conductors, etc. is to use a voltage level twice the voltage insulation rating of the device to be checked.

• Another rule of thumb is a 1MΩ value of motor insulation is considered to be acceptable.

• Anything below this value is considered to be suspect.Note: Always discharge the meg-ohm meter after taking readings. The dielectric can act like a capacitor and hold a charge, especially for higher voltages.


Electrical Drivers:

AC DRIVES

AC Drive Advantages• Cost - Three phase AC motors are much cheaper than DC motors of the same horsepower. AC controllers alsoincrease the

efficiency of an AC motor.• Maintenance - AC motors are virtually maintenance free.• Speed Control - AC motors have a wide range of speed control (up to 20 to 1).• Fully Regenerative - Four-quadrant control is easily achieved.• Good Open Loop Control - Typical open loop speed regulation is less than 5%.• Quick Response - AC motors have a relatively low inertia, which provides better response.• Easily Synchronized - Multi-motor systems are easily synchronized with a single AC Drive controller.

• Selection of Motors - Wide range of standard three phase motors are available.


AC Drive Interface CircuitsTypical interface circuits that can be applied to AC drives are shown in the figure below.

• The most recognized AC drive interfaces are the AC supply, and the stator. The feedback circuit can be a tachometer or it can be an optical encoder, an AC generator, a linear voltage displacement transformer, and even a current transformer.

• The drive condition circuit varies from a simple LED, to selectable conditions that will cause an output to change state. These can be conditions such as "drive at speed" or "drive in current limit". These conditions are outputs from the drive that can be used in external circuits.

• The run permissive include all of the external circuits that enable the drive. These can be safety gates, interlocks or contacts from another drive showing that it is "running at speed".

• The speed reference circuit is shown as a three-wire connection. The most common manual configuration is a three-wire pot used to manually set the speed reference. Other sources for the speed reference are an analogue output card from a PLC or a motion controller like the Allen Bradley IMC 121. These basic interface circuits can be identified on almost all drives. Recognizing them and being able to verify their function is a prime responsibility of troubleshooters.


Basic AC Drive SystemAn AC adjustable frequency drive typically consists of three basic parts: operator controls, drive controller (often referredto as an inverter) and an AC motor. The figure below shows a block diagram of these components.

The operator controls allow the operator to start, stop, and change direction and speed of the controller by simply turningpotentiometers or other operator devices. These controls may be an integral part of the controller or may be remotely mounted. Programmable controllers are often used for this function. The Drive Controller converts a fixed voltage AC to an AC waveform with adjustable frequency and voltage. It consists of a Control Unit and a Power Conversion Unit as seen in the figure above. The Control Unit oversees the operation of the drive and provides valuable system diagnostic information.


The figure below shows a block diagram of the Power Conversion Unit with the regulator shown as part of the control unit and the speed reference as part of the operator controls.

The Power Conversion Unit performs several functions. In the converter block, it rectifies the incoming fixed AC voltage (changes AC to DC). The resultant DC voltage is then filtered through an LC low pass filter to obtain a DC voltage bus in the intermediate block. The inverter block then produces an AC current and voltage output having the desired frequency to control the motor.The AC Motor converts the adjustable frequency AC from the drive controller to rotating mechanical energy.


DC DRIVES

Analog DC DrivesOne of the mainstays of DC Drives is the analog drive. The analog drive does not use a microprocessor or other forms of digital processing. The transistor and the operational amplifier are the active components in the drive. The analog drive is cheaper to build which is why it is still being made today.

Digital DC DrivesThe analog drive used transistors and op amps to perform its control functions. The digital drive is different in that it uses a microprocessor to bring about its control functions. The typical digital drive will have a logic and control board as the center of its drive control system. One of the benefits gained through the use of digital drives is their ability to communicate with other digital systems as shown below.


DC Drive Interface CircuitsTypical interface circuits that can be applied to either analog or digital drives are shown in the figure below.

• The most recognized DC drive interfaces are the AC supply, the armature (A1 - A2), and the field (F1 - F2).

• The feedback circuit can be a tachometer or it can be an optical encoder, an AC generator, a linear voltage displacement transformer, and even a current transformer.

• The drive condition circuit varies from a simple LED, to selectable conditions that will cause an output to change state.

• These can be conditions such as "drive at speed" or "drive in current limit". These conditions are outputs from the drive that can be used in external circuits.

• The run permissive include all of the external circuits that enable the drive. These can be safety gates, interlocks or contacts from another drive showing that it is "running at speed".

• The speed reference circuit is shown as a three-wire connection. The most common manual configuration is a three-wire pot used to manually set the speed reference.

• Other sources for the speed reference are an analogue output card from a PLC or a motion controller like the Allen Bradley IMC 121. These basic interface circuits can be identified on almost all drives. Recognizing them and being able to verify their function is a prime responsibility of troubleshooters.


DC Drive Block DiagramA typical block diagram of a DC drive's circuits which, can be applied to either analog or digital drives is shown in the figure below.

DC Drive Block DescriptionsError Circuit - Compares reference and feedback signals and produces an error signal for any correction needed.Usually contains two loops.(1) Major loop - the regulation loop(2) Minor loop - the current loop (much faster than the major loop)Sync Circuit - Provides a time frame or "window" where the gate pulse may be developed. It synchronizes the drive with the incoming line voltage.Delay Circuit - Produces a signal that triggers the firing circuit exactly where the gate pulse is to be placed within the sync window. This is the timing function of the drive. Usually produces a ramp voltage that will trigger the firing circuit at a particular level.Firing Circuit - Uses the signal developed by the Delay Circuit to generate a pulse with proper voltage, current, and time so that the pulse will fire the SCR's.


Power Circuit - Contains the power devices, SCR's, and diodes to drive the motor.Electronic Power Supply - Supplies all the necessary D.C. voltages to the electronic circuits.Clamping Circuit - Limits the drive in some manner. It may not allow the drive to run at all or may limit the drive in current, speed, etc.Run Permissive - Any conditions that must be met to run the drives, such as close to run circuits, E-stops, safeties, etc.Usually external inputs to the drive.

BASIC DC MOTOR PRINCIPLES

Electromotive ForceWhen a current carrying conductor is placed in a magnetic field it is subjected to an electromotive force. The direction of the force is given by the right hand rule.

F = Force on the conductor in newton.B = Flux density.I = Current in amperes.


The electromotive force is a result of the two magnetic fields and their interaction. The right hand rule is one way to establish the direction of force, another is the basic magnetic laws. Like poles repel and opposite poles attract. Thepermanent magnets flux lines travel from north to south. The left hand rule would indicate the flux lines around the wire.Once the flux lines from both sources are established the direction of force is known, flux lines traveling in oppositedirections-attract.

TorqueTorque is produced when a force exerts a twisting action on a body, tending to make it rotate.T = Fr , where T = Torque, F = Force, and r = radiusThe developed torque is directly proportional to:B: the flux density set up by the permanent magnet.L: the effective length of the current carrying conductor.I: the amount of current in the conductor.N: the numbers of loops.D: the distance between the two opposite live conductors.Torque = BLIND (unit for torque = Nm)Since B,L,N, and D are constants, the torque depends only on I, the amount of current in the conductor.Torque is produced in a DC Motor through the interaction of two magnetic fields.This force is the result of Field Flux (φf ) and Armature Flux (φarm ). T = k φf φarmTo change the speed of a DC Motor, you must affect the torque equilibrium.If a motor is at constant speed: Tmtr = Tload.To accelerate, this relationship must be taken out of equilibrium: Tmtr > Tload


Cable Glanding / Splicing Procedures

Photos from plant area what do you see wrong:

Cable rack not support cables,but cables support cable rack.

WHAT CAN GO WRONG?

Do E&I look after installation ?

WHAT CAN GO WRONG?


When cables are not used any more, do E&I only rollthe cable up without removing or isolate them?

WHAT CAN GO WRONG?

Is this how an cable be spliced?

WHAT CAN GO WRONG?


When an cable have NO slag(Extra cable) and rubber against steel what will happen after a time?

No extra cable (Loop cable) when needif anything happen when motor needsto be change out

Is this the way an cable glandneeds to be installed?

WHAT CAN GO WRONG?


Cable Glanding procedures

Why Should You Specify Cable Glands?How often have we heard: • We don't specify Cable Glands, as long as they have the relevant certification then it must be fit for purpose.• We leave it to contractor to sort out. • We are too busy concentrating on the high value, long lead time items to bother about such an insignificant value

product.In a recent paper presented at the Hazard Ex conference by a Senior Manager of CENELEC Standards Inspections, it was stated, Resources should be directed at eliminating the following common faults:• Unauthorized modifications.• Badly made-off or unsuitable cable entry devices.• Corrosion.It went on to say that out of these three factors, the most common fault was bad installation of Cable Glands. The paper was specifically referring to maintenance procedures, but this could equally be applied to new installations.

Incorrect specification and installation combined with the lack of ability to inspect the Cable Gland in it's operable conditioncan cause equipment failure and corrosion of cable armor and braid. The safety risks inherent in this is incalculable, as is the consequential loss of production.This statement alone should be enough reason why specification of Cable Glands is an important decision. Just relying on the fact that a Cable Gland has a certificate "fit for purpose" is not enough.


So What Should You Take Into Account When Specifying The Cable Gland?

Certification and SelectionOf course, it is vital that the correct Cable Gland is selected and is certified as appropriate for the hazardous area in which it is to be used. We provide technical information in our Cable Gland catalogue and also supply a Cable Gland selection software application to take the specifier step-by-step through the process of selection. If still in doubt our Technical Department has a team of experienced engineers to assist. But just relying on a Cable Gland that is certified for the type of protection that is required (e.g. "fit for purpose") is not enough.

Ingress Of MoistureOne of the most important features of a Cable Gland is elimination of moisture ingress, not only into the equipment, but alsointo the armor clamping area of the Cable Gland itself. Water ingress into this area has been shown to cause catastrophic corrosion of cable armor and braids, with the associated costs of new cabling and downtime. IP ratings give a guide to protection of water and dust ingress into the equipment but not necessarily into the Cable Gland itself.

DTS01In 1991 Shell UK recognized that IP ratings are not necessarily sufficient to meet the harsh conditions found in many hazardous area installations and developed a far more demanding test DTS01 to eliminate water ingress under thermal cycling and deluge conditions. We have taken Shell's DTS01 test one step further and our DTS01 test certificate is extended to show no water ingress into the armor clamping area of the Cable Gland when fitted with a deluge seal. This is clearly an issue when specifying Cable Glands. Not all Cable Gland manufacturers test certificates cover ingress protection into the armor clamping area, nor do they cover the full operating temperature range for which they have been certified for use.


SealsCable Gland seals perform two functions:• Prevents the products of an explosion reaching the outside atmosphere if an explosion occurs inside the enclosure.• Stops water and dust ingress into the equipment and Cable Gland.

Seal MaterialsVarious seal materials are used by different Cable Gland manufacturers, but in general they fall into two categories:• Thermoset (TSE) These materials are cross-linked (vulcanized) during the molding process with the application of heat and

pressure. Once formed, they will not 'melt' and will exhibit optimum sealing properties over a wide range of temperatures.

• Thermoplastic (TPE) Although much cheaper to manufacture than TSE seals they 'melt' when heated and their sealing properties deteriorate as operating temperatures increase. Ideal for appliance feet, soft touch knobs and handles, they are not recommended for critical sealing applications.

TSE's on the other hand, are far more suitable for Cable Gland seals and are the only materials used by Hawke International in our range of compression and diaphragm Cable Gland seals. TSE's have better elastic properties over a wider range of temperatures, e.g.:Compression set (recovery from deformation), the test is done usually at elevated temperatures and a test piece is squashed in a clamp by 25% of it's thickness, left in an oven for 3 days, at the end of which the sample is left to recover at ambienttemperature. The difference between the original thickness and the new thickness (the ‘set’) is expressed as a percentage of the amount it was squashed by - a good TSE will show a compression set % of less than a 3rd of that shown by even the best TPE.


The ageing resistance of TSE's is better, particularly ozone, UV, oxidization resistance and ‘weathering’ resistance. The chemical and oil resistance of TSE's can be infinitely better. The temperature resistance of TSE's is much better. For example, silicone TSE has a maximum intermittent operating temperature of 300°C, whereas most TPE's soften appreciably at 100°C. Silicone will operate effectively at -60°C, whereas the best TPE works at -40°C. Flame resistance is better, silicone has the additional benefit of being low smoke and fume and zero halogen.

Cable Tolerances and ConstructionCable costs are significant in a hazardous area installation and we have seen moves to reduce costs by reducing specificationand tolerances of the cables. Cable Glands employ a rear sealing system with an extremely wide tolerance range, which takes into consideration variation in cable diameters along it's length and does away with the need to specify Cable Glands with special outer seals.

Cold FlowThere are also requirements for some cables to be flame-resistant or flame retardant in accordance with IEC 60331 and IEC 60332. Many of these cables exhibit ‘cold flow’ of the inner sheath bedding. That is, the material will flow away from pressure applied to it, such as that of a Cable Gland inner seal of the compression or displacement type, hence creating an inefficient seal. The code of practice EN 60079-14 / IEC 60079-14 Clause 10.2 notes clearly states that a Cable Gland employing a compression (displacement) seal should not be used on cable exhibiting "cold flow characteristics". Cable Glands uses a diaphragm inner seal that complies with this requirement in the code of practice, in that it exerts minimal pressure on the cables inner sheath. It does not cause ‘cold flow’ but maintains IP and explosion requirements.


Correct InstallationOnly training of the Cable Gland installer in the correct practice of installation can ensure that the Cable Gland will functioncorrectly. Most reputable contractors ensure that their personnel have been fully trained and in many cases, it is a requirement that they hold a certificate from a recognized training authority such as CompEx. However, in some regions of the world, this is not so stringent, therefore it is important that the Cable Gland selected has been designed with ease of installation in mind, that every Cable Gland comes with detailed installation instructions and is easy to inspect at each stage of the installation operation. Cable Glands designed with minimum components, ease, speed and simplicity of installation.

Safety Through InspectabilitySafety is of prime importance on hazardous area installations. Safety depends on many factors, some of which have already been discussed. Inspectability of equipment also plays a key part in safety. Can all the safety features of the Cable Gland be inspected, preferably easily? All our Cable Glands can be easily disassembled to allow visual inspection of the armor clamping arrangement.

Why You Should Specify Cable GlandsIf you are interested in safety, reliability and the lowest lifetime cost through reduced downtime and loss of production of your plant, then you should take the time to consider specifying the features you require from your Cable Gland.


SpecificationIn summary, what key features during specification of Cable Glands should you be considering?• The most common fault experienced on hazardous area installations is incorrect selection and bad installation of Cable

Glands.• Will a Cable Gland that is certified "fit for purpose" meet all your requirements?• There are necessary features that are not covered in the certification process. Does the Cable Gland meet your

requirements for ingress of dust and moisture?• Does it have a test certificate covering the deluge requirements of DTS01 for ingress into the equipment and into the

armor clamping arrangement of the Cable Gland?• Will the Cable Gland seals give long life and protection from water ingress under the typical heat cycling and operational

conditions on site?• Are they produced from the best Thermoset (TSE) material?• Will the Cable Gland sealing range cope with the cable diameter tolerances without the need for special seals?• Is the Cable Gland suitable for use on cables that exhibit ‘cold flow’ characteristics and in line with the code of practice

IEC/EN 60079-14 Clause 10.2?• Is the Cable Gland fast and easy to install with minimum parts and clear assembly instructions?• Will the Cable Gland enhance safety on your site through ease of inspection?

Videos:http://www.ehawke.com/technical/installation-videos.html#

http://www.ehawke.com/technical/installation-videos.html


General info on Area Classification

Area classification is the division of a facility into three-dimensional hazardous areas and non-hazardous areas and the subdivision of the hazardous area into ‘Zones’.Hazardous areas may be sud-divided into three Zones as shown below.

Flammable Gases and Vapours

Zone 0An area in which an explosive atmosphere is constantly present, or present for long

periods.

Zone 1An area in which an explosive atmosphere is likely to occur in normal operation.

(Rough Guide: 10 hours or more / year but less than 1,000 hours / year)

Zone 2

An area in which an explosive atmosphere is not likely to occur in normal operation

and if it occurs it will exist only for a short time.

(Rough Guide: Less than 10 hours / year)Combustible Dusts

Zone 20

An area in which combustible dust, as a cloud, is present continuously or frequently,

during normal operation, in sufficient quantity to be capable of producing an

explosive concentration of combustible dust in a mixture with air.

Zone 21

An area, in which combustible dust, as a cloud, is occasionally present during normal

operation, in a sufficient quantity to be capable of producing an explosive

concentration of combustible dust in a mixture with air.

Zone 22

An area, in which combustible dust, as a cloud, may occur infrequently and persist

for only a short period, or in which accumulations of layers of combustible dust may

give rise to an explosive concentration of combustible dust in a mixture with air.

For further information on the classification of hazardous areas see:IEC/EN 60079-10 - Electrical Apparatus for Explosive Gas Atmospheres, Classification of Hazardous Areas.Energy Institute (Formerly Institute of petroleum) - Model Code of Safe Practice in the Petroleum Industry. E115 Area Classification Code for Petroleum Installations.


Classification SocietyA Classification Society may also enforce requirements for the design and installation of facilities. These requirements, which are in addition to statutory requirements, may influence the design and installation of the electrical systems. Classification Societies include ABS, DNV and Lloyds Register.

Design and Installation of Electrical Systems for Hazardous (Classified) AreasThere are numerous regulation codes, guidelines and standards for the design, selection and installation of electrical installation in potentially explosive atmospheres. These requirements are in addition to the requirements for installations in non-hazardous areas.There are several types of protection, i.e. construction techniques, available for electrical apparatus in hazardous areas. The type of protection permitted will depend upon the applicable installation codes and rules to be adopted.The selection of electrical apparatus should be in accordance with the following:Classification of the hazardous area.Temperature class or ignition temperature of the gas, liquid, vapor's, mist, dust or fiber.Where applicable, the gas, vapor or dust classification in relation to the group or subgroup of the electrical apparatus.External influences and ambient temperature.

IEC Wiring MethodsWith the introduction of cables incorporating new construction materials and especially cables with fire retardant or fire resistant properties such as cables complying with IEC 60331 and IEC 60332, cables may exhibit "cold flow" characteristics.

http://www.eagle.org/

http://www.dnv.com/

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"Cold flow" is a term used for thermoplastic materials that flow when subjected to pressure at ambient temperature. These "cold flow" characteristics could have adverse effects on the protection of the apparatus. A suitable cable gland should be usedthat does not incorporate displacement / compression seals that act upon the part(s) of the cable having cold flow characteristics.To overcome this problem, we have developed cable glands that incorporate diaphragm seals that act upon the "cold flow" cable sheath without compressing or damaging the cable. A typical cable gland incorporating displacement/compression seals and incorporating a diaphragm seal are shown below.

No cable damage due to diaphragm sealcable gland design.

Cable damage as found with cable gland designs incorporating compression / displacement seals.


Wiring Methods for Type of Protection ‘e’ - Increased Safety:The cable entry device, e.g. cable gland, must comply with all the requirements referred to in the appropriate standard, be appropriate to the cable type and maintain the type ‘e’ integrity of the equipment.A minimum ingress protection rating of IP54 is required for increased safety equipment. To meet with this requirement it may be necessary to provide a seal between the cable gland and the equipment, for example, by the use of a sealing washer or thread sealant. Where cable glands are fitted into non-metallic enclosures, metallic enclosures with a painted type finish or enclosures with non-threaded clearance holes, additional ingress and earthing / bonding considerations may be necessary.

CENELEC and IEC Degree of Protection, IP CodeThe standards IEC/EN 60529 describes a system for classifying the degrees of protection provided by the enclosures of electrical equipment as follows:

First Number Second Number

Code Number Icon Protection Description Code Number Icon Protection Description

0 Non-protected.

Protection of

persons against

access to hazardous

parts inside the

enclosure and

against solid foreign

objects.

0 Non-protected

Protection of the

equipment inside

the enclosure

against harmful

effects due to the

ingress of water.

1

Protected against

objects of 50mm

diameter and

greater.

An object probe,

sphere of 50mm

diameter, shall not

fully penetrate.

1

Protected against

vertically falling

water drops.

Vertically falling

drops shall have no

harmful effects.




2

Protected against solid

foreign objects of

12.5mm diameter and

greater.

An object probe,

sphere of 12.5mm

diameter, shall not fully

penetrate.

2

Protected against

vertically falling water

drops when enclosure

tilted up to 15°.

Vertically falling drops shall

have no harmful effects when

the enclosure is tilted at any

angle up to 15° on either side

of the vertical.

3


foreign objects of

2.5mm diameter and

greater.

An object probe,

sphere of 2.5mm

diameter, shall not

penetrate at all.

3Protected against

spraying water.

Water sprayed at an angle up

to 60° on either side of the

vertical shall have no harmful

effects.

4


foreign objects of

1.0mm diameter and

greater.

An object probe,

sphere of 1.0mm

diameter, shall not

penetrate at all.

4Protected against

splashing water.

Water splashed against the

enclosure from any direction

shall have no harmful effects.

5 Dust-protected.

Ingress of dust is not

totally prevented, but

dust shall not penetrate

in a quantity to

interfere with

satisfactory operation

of apparatus or to

impair safety.

5Protected against water

jets.

Water projected in jets against

the enclosure from any

direction shall have no harmful

effects.




6 Dust-tight. No ingress of dust. 6Protected against

powered water jets.

Water projected in

powerful jets against the

enclosure from any

direction shall have no

harmful effects.

Typical Designation : IP66

7

Protected against the

effects of temporary

immersion in water for

30 mins.

Ingress of water in

quantities causing

harmful effects shall not

be possible when the

enclosure is temporarily

immersed in water under

standardized conditions

of pressure and time.

8

Protected against the

effects of continuous

immersion in water.

Ingress of water in

quantities causing

harmful effects shall not

be possible when the

enclosure is continuously

immersed in water under

conditions which shall be

agreed between

manufacturer and user

but which are more

severe than for numeral

7.


The protection of the enclosure and the equipment inside against external influences or conditions, such as: mechanical impacts, corrosion, corrosive solvents, solar radiation, icing moisture (e.g. produced by condensation), and explosive atmospheres, are matters that should be dealt with by the relevant product standard.There are additional and supplementary optional letters to the above coding; these designators are A, B, C & D and H, M, S & W, and further information can be found in the relevant standard(s).

Deluge Ingress ProtectionOn offshore facilities, equipment may be located in areas subject to emergency deluge systems. Equipment that has been evaluated as certified for use in hazardous areas may not be suitable for use in these locations. A testing method for electrical equipment to be installed in areas subject to deluge systems, DTS01, has been prepared by the Explosion and Fire Hazards Group of ERA Technology (now known as ITS) in collaboration with Shell UK Exploration and Production Ltd.Testing includes:Energizing the equipment (where appropriate) for 60 minutes prior to the deluge test, then interrupting the electrical power at the start of the deluge test and resuming after 60 minutes until the completion of the deluge test.Carrying out insulation resistance testing before and after pre-conditioning and after the deluge test, where applicable.Carrying out pre-conditioning by exposure to vibration and thermal ageing at 90% relative humidity and at a temperature 20k above the equipment's maximum service temperature and/or at least 80°C of any appropriate seals.Carrying out deluge test using a deluge chamber fitted with deluge nozzles that apply a salt water solution deluge pressure within the range of 3.5 bar to 4.5 bar at a water temperature in the range of 5°C to 10°C for 3-hours.


Installation Instructions For Cable Gland

It is not necessary to dismantle the cable gland any further than illustrated belowSub Assembly A C R Sub Assembly B

Entry Component Main Item Detachable AnyWay Body Outer Seal Nut

Cone Clamping Ring

• If required fit shroud over the cable outer sheath. Prepare the cable by removing the cable outer sheath and the armor to suit the geometry of the equipment. Remove a further 18mm (maximum) of outer sheath to expose the armor. If applicable remove any tapes or wrappings to expose cable inner sheath. Separate the gland into two sub-assemblies “A & B”. Ensuring that the outer seal is relaxed, pass sub-assembly “B” over the cable outer sheath and armor followed by the “AnyWay” clamping ring (R). Note: On maximum size cables the clamping ring may only pass over the armor.


• Ensure that the inner seal is relaxed and secure sub-assembly “A” into the equipment as indicated.

• Locate the detachable armor cone (C) into the recess of sub-assembly “A”. Pass cable through sub-assembly “A”, evenly spacing the armor around the cone.

• Whilst continuing to push the cable forward to maintain the armor in contact with the cone tighten the main item by hand until heavy resistance is achieved, then tighten a further full turn with a spanner.


• Hold the main item with a spanner then tighten sub-assembly “B” onto sub-assembly “A” ensuring the two components make “metal to metal” contact.

• Tighten the outer seal nut until either: i) the outer seal nut makes metal to metal contact with the gland body, or ii) the outer seal nut has clearly engaged the cable and cannot be further tightened without the use of excessive force by the installer. This completes the procedure for the direct entry installation. Please see overleaf for remote installation


Jointing Instructions for LV cables

Important Notes• These instructions are relevant for a range of different Low Voltage straight and branch joints including CM0 – CM5, CB1 and

CB2 models. They show typical arrangements but the procedures are the same for any variation of joint.

• Instructions assume that cables are de-energized.

• Instructions are for guidance only, and subject to standard jointing procedures which should always be followed.

• Dispose of all waste materials and packaging safely; clear accidental spillage immediately

• Do not use in a confined, unventilated area; avoid breathing the resin curing vapors.

• Wear protective gloves provided at all times when handling cold pour resins.

• Avoid contact with skin and eyes. In case of accidental contact treat the area with copious quantities of water. Full Health & Safety information is available upon request.

• Smoking should be prohibited.


Straight Joints

Cable Size mm2 Dimension ‘X’ mm1.5 - 25 2535 - 120 35150 - 185 40Telephone/Pilot/Control 25


2 x Branch Joints

Main Cable Size mm2 Dimension ‘X’ mm1.5 - 25 2535 40NB. The above joint may be constructed without cutting through the mains cable (“uncut main”) using the appropriate connectors. In this case remove the outer sheath, armors andbedding to the above dimensions. Both the service branch and mains cables may be 2, 3 or 4 core.


Jointing the CablesClean and decrease the armors and lead sheath (if present) and abrade the outer sheath from the armors to a distance of 10mm outside the joint case. When jointing the cables use the connectors (if provided) or other approved types. For power cables use phase separators (if supplied) in the vicinity of the connectors and in any event ensure approx. 10 mm separationbetween connectors. A typical connection for a branch joint is shown below using mechanical connectors.

Remove the insulation from each end of the earth strap as shown. Attach the braid to the main cable armors using constant force spring 1. When attaching the ends of the braid allow the braid to extend beyond the spring and after applying one full turn fold the braid back over the spring, 2, as shown. Cut off any excess. For straight joints simply use spring 1 on each side of the joint.


Completing the JointAfter making the earth braid connections place a half of the joint case around the joint positioning centrally. Cut the ends of the case to suit the cables using a hacksaw. Make sure that the connectors are at least 10mm apart.


General InstructionUse PVC tape at the cable entry points to seal the joint case. Mix the resin as instructed on the resin pack and pour into the joint case until the case is completely full. Finally fit the lid to the filler hole. Ensure cable joint is level and both cables and joint are supported independently. For applications up to 1000 volts, the joints may be filled under load conditions. The completed joint should be left uncovered before back-filling for two hours to allow the resin to fully cure. Ensure that there is no movement of the cable cores during curing of the resin.


IP Rating of Enclosures

This is an Remote I/O station that get info from the field to help Control Room to control the process. This is how it looks inside, because the IP Rating of the enclosure“FAILS”

Gland holes not close after cables removed


Degrees of protection are classified in three general categories.1) Protection of persons against access to hazardous parts inside enclosures.This is intended to cover protection of persons against accidental contact with electrically ‘live’ or otherwise hazardous mechanical parts contained within the enclosure, e.g. rotating blades, switch mechanisms etc.

2) Protection of the equipment inside the enclosure against the ingress of solidforeign objects.Intended to cover protection of the equipment mounted inside against tools, and/or strands of wire and/or the harmful ingress of dust particles. Barriers, shapes of openings or any other means - whether attached to the enclosure or formed by the enclosed equipment - suitable to prevent or limit the penetration of the specified test probes are considered as a part of the enclosure, except when they can be removed without the use of a key or tool.

3) Protection of the equipment inside the enclosure against harmful ingress of water.Intended to cover protection of equipment from harmful effects due to dripping, spraying, splashing and hosing or totalimmersion.It should be noted that the specified degrees of protection in this third area of BS EN 60529 do not include a strictclassification for weather resistance, corrosion prevention, or resistance to other physically hazardous conditions.

BS EN 60529 states in clause 2, that measures to protect against,• mechanical impact • solar radiation• corrosion • icing • corrosive solvents • moisture (condensation) • fungus • explosive atmospheres • vermin • contact with moving parts external to the enclosure are not considered and should form part of the product specification where relevant.


Where an enclosure needs to be machined or adapted for the attachment of cable glands, conduit or any other equipment, any instructions provided by the enclosure manufacturer should be strictly observed to ensure the required degree of protection is maintained.

The degrees of protection provided by an enclosure are indicated by the IP code in the following way:


Selection should be made by initially considering the protection required at the place of installation:a) of persons likely to use or come into contact with the equipment.b) the suitability of the enclosure for the working environment for which it is intended.The specified/claimed IP Code applies when the equipment/enclosure is properly installed, according to the manufacturers’ instructions.In areas where only skilled (2) and/or instructed persons (3) have access, an enclosure with a lower protection category may be acceptable, whereas the opposite would apply where uninstructed persons have access.e.g. In general, wiring accessory product standards specify protection against access to hazardous parts. A typical requirement for accessories used in domestic or commercial environments will be IP2XD.Note 2: Skilled Person. A person with technical knowledge or sufficient experience to enable him/her to avoid dangers which electricity may create.Note 3: Instructed Person. A person adequately advised or supervised by skilled persons to enable him/her to avoid dangers which electricity may create.


IP Rating use in Mining


Electrical Light IP Rating

Is this the way to installed and maintained Electrical Lights?


What is light?Light is that part of the electromagnetic spectrum that is perceived by our eyes. The wavelength range is between 380 and780 nm. By day we see in color, while at night we can only see in shades of grey.

Light has a triple effect• Light for visual functions• Illumination of task area in conformity with relevant standards• Glare-free and convenient• Light creating biological effects• Supporting people’s circadian rhythm• Stimulating or relaxing• Light for emotional perception• Lighting enhancing architecture• Creating scenes and effects

Basic parameters used in lightingLuminous fluxThe luminous flux describes the quantity of light emitted by a light source. The luminous efficiency is the ratio of the luminous flux to the electrical power consumed (lm/W). It is a measure of a light source’s economic efficiency.


IlluminanceIlluminance describes the quantity of luminous flux falling on a surface. It decreases by the square of the distance (inversesquare law). Relevant standards specify the required illuminance (e.g. EN 12464 “Lighting of indoor workplaces”).Illuminance: E(lx) =luminous flux (lm) / area (m2)

Luminous intensityThe luminous intensity describes the quantity of light that is radiated in a particular direction. This is a useful measurement for directive lighting elements such as reflectors. It is represented by the luminous intensity distribution curve (LDC).

LuminanceLuminance is the only basic lighting parameter that is perceived by the eye. It specifies the brightness of a surface and is essentially dependent on its reflectance (finish and color).

Light colorThe light color describes the color appearance of the light.

Color temperature Appearance Associationww (warm white) up to 3300 K reddish warmnw (intermediate white) 3300–5300 K white neutraltw (cool white) from 5300 K bluish cool


Application area – Light for Industry

Vapor tight luminaires• Polycarbonate housing• Minimum six polycarbonate or stainless steel

latches• Continuous check on seal and mounting

brackets.• Check glands and covers for any damage to

uphold IP65 rated• Check fluorescent tubes for correct light in

area.


Basic Understanding and Configure of Siemens SIMOCODE-DP System Motor Protection and Control.

SIMOCODE pro (SIRIUS Motor Management and Control Device) is a flexible and modular motor management system for motors with constant speeds in low-voltage applications. It optimizes the link between the control system and the motor feeder, increases plant availability and allows significant savings to be made during installation, commissioning, operation and maintenance. SIMOCODE pro is installed in the low-voltage switchgear system and links the higher-level automation system (via PROFIBUS DP) and the motor feeder intelligently.It comprises the following functions:• Multifunctional and electronic full motor protection, independently of the automation system• Integrated control functions for motor control (instead of hardware)• Detailed operating, service and diagnostics data• Fail-safe shutdown up to SIL3 using fail-safe expansion modules (SIMOCODE pro V only)• Open communication via PROFIBUS DP, the standard for fieldbus systems.• Parameterization with the SIMOCODE ES software package.• Only the switching and short-circuit protection mechanisms of the main circuit (contactors, circuit breakers, fuses) are

additionally needed.

Benefits• The quantity of cabling required between the motor feeder and the PLC is reduced significantly by connecting the entire

motor feeder to the process control system via the bus.


• Automated processes are decentralized by means of configurable control and monitoring functions in the feeder. This saves automation system resources and ensures that the feeder is fully functional and protected even if the control system or bus system fails.

• By recording and monitoring operating, service and diagnostics data in the feeder and process control system, plant availability is increased, and the feeder is easier to service and maintain.

• The user can implement plant-specific requirements for every motor feeder thanks to the high degree of modularity.• SIMOCODE pro provides compact solutions and different levels of functions for every customer application.• By replacing the control circuit hardware with an integrated control function, the quantity of required hardware

components with wiring is reduced. This drives down storage costs and limits potential wiring errors.• Using electronic full motor protection allows the motors to be used more efficiently and ensures that the tripping

characteristic remains stable and the tripping response stays the same, even after many years.

Communication:SIMOCODE pro has an integrated PROFIBUS DP interface. This replaces all individual wiring and distribution boxes (normally required to exchange data with a higher-level automation system) with a single two-wire cable.SIMOCODE pro supports:• Baud rates up to 1.5 Mbit / s or 12 Mbit / s• Automatic baud rate detection• Communication with up to 3 masters• Time synchronization via PROFIBUS (SIMATIC S7)• High-precision timestamping (SIMATIC S7)• Cyclic services (DPV0) and acyclic services (DPV1)• DPV1 communication downstream from the Y-link.


Monitoring functionsCurrent limit monitoring - is used for process monitoring. This enables incipient anomalies in the system to be detected in good time. If a current limit is exceeded but still below the overload limit, it can, for example, indicate a dirty filter on a pump, or an increasingly sluggish motor bearing. If the current limit is undershot, it can be the first sign of a worn-out drive motor belt.

Ground-fault monitoring - Residual current monitoring relays are used in industry to• Protect systems from damage caused by residual currents• Prevent production losses caused by unplanned downtime• Perform maintenance to meet all demands.

Voltage monitoring - SIMOCODE pro V allows voltage monitoring of a three-phase current network or a single-phase network for Undervoltage or further availability:• Monitoring for Undervoltage: Two-level monitoring for freely selectable limits. The response of SIMOCODE pro V on

reaching a pre-warning level or trip level can be freely parameterized.• Monitoring for further availability: Even when the motor is switched off, SIMOCODE pro V can indicate the further

availability of the feeder by measuring the voltage directly at the circuit breaker or fuses.

Temperature monitoring - SIMOCODE pro S and SIMOCODE pro V offer the option of implementing analogtemperature monitoring, e.g. of the motor windings or the bearings - SIMOCODE pro S with the multifunction module, SIMOCODE pro V with the temperature module. SIMOCODE pro S and SIMOCODE pro V support two-level monitoring for over temperature for freely selectable limit values.


Active power monitoring - The active power curve of a motor reflects its actual load. Excess load results in increased wear of the motor and, thus, may lead to premature motor failure. Excessively low active power can indicate no-load operation of the motor, for example. SIMOCODE pro V offers the option of two-level active power monitoring for freely selectable upper and lower limits respectively. The response of SIMOCODE pro V on reaching a prewarning level or trip level can be freely parameterized and delayed.

Cos phi monitoring - The power factor fluctuates more than either the motor current or the active power does, particularly in the low-end performance range of a motor. Monitoring the power factor is therefore a particularly suitable way of distinguishing between no-load operation and faults, e.g. a broken drive belt or drive shaft. SIMOCODE pro V enables two-level monitoring of the power factor (cos phi) for freely selectable minimum limits. The response of SIMOCODE pro V on reaching a prewarning level or trip level can be freely parameterized and delayed.

Monitoring operating hours, stop time, and number of starts - SIMOCODE pro can monitor the operating hours and stop times of a motor to avoid plant downtimes due to failed motors caused by either running too long (wearing out) or being stopped for too long. For example, if an adjustable limit value is exceeded, a signal indicating that the relevant motor requires maintenance or replacement can be generated. After replacing the motor, the operating hours and motor stop times can be reset. To avoid excessive thermal strain and premature aging of a motor, the number of motor starts in a selected time frame can be limited. The limited number of possible starts can be indicated by pre-warnings.


Monitoring additional process variables via the analog module - SIMOCODE pro V allows measuring and monitoring of any other process variables via the analog module. For example, the fill level can be monitored to protect a pump against dry operation, or a differential pressure transducer can be used to monitor the degree of pollution in a filter. If the fill level undershoots a specified level, the pump can be switched off and, if a specific differential pressure value is exceeded, the filter is to be cleaned. SIMOCODE pro V supports two-level monitoring of the corresponding process variable for freely selectable upper and lower limits. The response of SIMOCODE pro V on reaching a prewarning level or trip level can be freely parameterized and delayed.

Phase sequence identification - SIMOCODE pro allows the direction of rotation of a motor to be determined by identificationof the phase sequence. If the direction of rotation is wrong, a signal can be generated or the motor switched off.

Monitoring any measured values using unrestricted limit monitors - SIMOCODE pro can monitor every measured value in the system for undershooting or overshooting a set threshold value by means of unrestricted limit monitors.• For use of SIMOCODE pro V with current / voltage measuring module• Temperature module or multifunction module additionally required• Analog module additionally required• Ground-fault module or multifunction module and residual current transformer additionally required


Data transfer


Commissioning and programming of Simocode

Step and DescriptionStep1Switch on the power supply. In a fault-free state, the following LEDS should light up or flash green:• "Device" (lights up) • "Bus" if PROFIBUS DP is connected (lights up or flashes).Proceed to Step 2. Otherwise, carry out diagnostics according to the LED display. For more information, see Diagnostics via LED display on the basic unit and on the operator panel (Table 15.5). Try to rectify the fault.


Step 2 If you wish to make SIMOCODE pro available on the PROFIBUS DP, set the PROFIBUS DP address.


Step 3 Parameterize SIMOCODE pro or check the existing parameterization, e.g. with a PC on which SIMOCODE ES software is installed. For this, connect the PC / PG to the system interface with the PC cable (see the figure below).Notice: With SIMOCODE pro C use the system interface on the front and with SIMOCODE pro S use the right-hand system interface.

Step 4 Start SIMOCODE ES.


Video to view

SIMOCODE PRO - YouTube (360p) in video folderSIMOCODE pro for PROFINET - YouTube (360p) in video folder


Basic Understanding of SAG Mill Sprint Electric PL/PLX Digital DC Drive

The PL/X DC motor controller uses closed loop control of armature current and feedback voltage to give precise control of motor torque and speed. The unit also controls the motor excitation field. The closed loop parameters are programmable by the user and a wealth of inputs and outputs are provided to allow very complex motion control processes to be achieved. The series is comprised of 5 frame variants each with 2 and 4 quadrant models. Selected 2 quadrant models also offer a unique regenerative stopping facility.Programming the unit is designed to be simple. A large backlit alphanumeric display guides the user through a friendly menu structure to select options and parameter changes. Built in application software blocks are provided to be connected up as desired. Comprehensive fault monitoring and serial communications allow off site programming and remote diagnostics. All models are stock items. These units are very compact. The savings made possible in panel space and enclosure costs may be significant.

How do they work?This shows the basic arrangement of the drive control loops. The 3-phase thyristor bridge is a phase controlled rectifier, which delivers power to the motor armature. The armature current (and hence the motor torque) is sensed to provide feedback to the inner current loop. After being scaled this is compared to the current demand. The current error amplifier is able to detect any difference, and then act in such a way that the current feedback remains identical to the current demand during normal operation. This inner loop monitors the armature current and delivers more current or less current as required.The outer speed loop works in the same way as the inner current loop but uses different parameters. In the above example, the demand is provided by the user in the form of a speed reference, and the speed feedback is derived from a shaft-mounted tachometer. Any difference is detected and translated into a new current demand level.


This level provides the right amount of current (and hence torque) to reduce the speed error to zero. This new demand level is presented to the inner current loop, which obeys as rapidly as possible.The whole process is performed on a continuous basis giving superb speed accuracy and dynamic performance. In typical systems, there are numerous house keeping tasks and interface requirements. For these, the PL/X series has a wealth of standard features to benefit the user.A range of standard application blocks is included, with a user-friendly configuration facility that displays a description of the selected connection points. The programming menu is designed for rapid travel to the desired parameter using 4 keys and a large backlit alphanumeric display. A large number of monitoring facilities is available to enable display of all points in the block diagram. The unit is supplied with PL PILOT, a superb PC windows based configuration and monitoring tool.


Useful things to know about the PL/X• The unit comes from the factory with a built in default personality which will be suitable for most applications, but may be

re-programmed by the user. Up to 3 total instrument recipes can be stored.• The default personality can be restored by holding down all 4 keys and applying the control supply, but the calibration values

relevant to the motor are unaffected by this procedure. • There are over 700 programmable parameters available, but only a handful of these will need to be adjusted by most users.• Internal connections between blocks and parameters are easily altered to suit special applications.• All parameters have a unique identification number called a PIN (Parameter Identification Number)• When parameters are altered by the user they become effective immediately. However the alterations will be lost if the

control supply is removed prior to performing a parameter save.• Most parameters may be adjusted while the drive is running to assist commissioning. If this is not advisable the unit requests

a stop condition.• There is a built in ‘meter’ which allows monitoring of all relevant inputs and outputs including power connections, in

engineering units and percentages. There are also default % diagnostic summary windows.• There is a large selection of robust inputs and outputs to interface with typical systems.• The drive personality is stored in one memory device which is designed to be transportable to another unit in the event of a

breakdown. See 10.2.3.3 PARAMETER EXCHANGE / Eeprom transfer between units.• All the drive parameter values may be listed out on a printer. Parameters that have been altered from the default are

identified in the listing. They may also be sent to, or received from, another unit or computer.• The unit contains standard special applications blocks that are normally switched off unless activated by the user. These

include signal processors, PIDs etc. They do not take part in the prime control of the motor, but may be used to construct more complex systems at no extra cost. There is a facility to provide a super fast current response for high performance applications.


Control terminals electrical specification

UNIVERSAL INPUTS(UIP2 – UIP9) - 8 analogue inputs with up to 5mV +sign resolution (+/- 0.4%) 4 input voltage ranges +/-5/10/20/30V on each input 8 digital inputs with settable thresholds. Good noise immunity. Overvoltage protected to +/-50V.

ANALOGUE OUTPUTS(AOP1 AOP2 AOP3 and IARM on T29) - 4 analogue outputs (+/- 0.4%), 3 programmable, 1 committed to output armature current signal 2.5mV plus sign resolution. Short circuit protection to 0V. Output current +/-5mA maximum Output range 0 to +/-11V.

DIGITAL INPUTS(DIP1 - DIP4) - 4 digital inputs. Logic low below 2V, Logic high above 4V. Low noise immunity. Overvoltage protection to +50V. Input impedance 10K Ohms DIP3 and DIP4 may also be used for encoder quadrature signals.

DIGITAL IN/OUTPUTS(DIO1 – DIO4) - 4 digital inputs. Also programmable as outputs (see digital outputs). Logic low below 6V. Logic high above 16V. Overvoltage protection to +50V. Input impedance 10K Ohms. When used as digital outputs the spec. is the same as DOP1-3.

DIGITAL OUTPUTS(DOP1 – DOP3) - 3 outputs (for 4 more outputs with this spec. use DIO1/2/3/4). Short circuit protected. (Range 22 to 32 Volts for OP high) Over-temperature and over-voltage protected to +50V. Each output can deliver up to 350mA. Total for all outputs of 350mA, this spec. also applies to DIO1/2/3/4 when they are programmed as outputs.

TACH INPUT(25(0V) + 26) - +/- 200V range Input impedance 150K Ohms


REFERENCE OUTPUTS( +10 (T27) & -10 (T28) +/-10.00V, 0.5%, 10mA max. Short circuit protection to 0V.

ARMATURE CURRENT(IARM) +/-5V linear output for +/-100% model rating current. Output current capability 10mA max. Short circuit protection to 0V. Programmable Uni-polar or Bi-polar output mode (tolerance+/-5%).

THERMISTOR INPUT(THM) Motor temperature thermistor. If unused then connect to 0V. OK<200 Ohms, Overtemp >2K Ohms. Connect from THM to 0V.

CONTACTOR CONTROL - 24V Logic inputs. Logic low below 6V, logic high above 16V Input impedance. 10K Ohms. Overvoltage protection to +50VRUN JOG START - Drive enable. Electronic enable for current loop and contactor drop out delays Jog input with programmable contactor drop out delay Start/stop. Drops contactor out at zero speed. The drive will not start unless all alarms are clear. The drive will not restart after alarm induced contactor drop out, unless START is removed for at least 50mS and re-applied.CSTOP +24V - Coast stop. Drops contactor out immediately (100ms). Input impedance 10K Ohms. +24V output for external logic (Range 22 to 32 Volts). Short circuit protected. Overvoltage protection to +50V. Shares total current capability of ‘Digital Outputs’ (350mA), plus extra 50mA of its own. Total maximum available 400mA.

Jog Digital Input JOG T32When the Jog Input is held high the drive jogs (rotates slowly while requested to), provided input Start T33 is low. When the Jog Input is removed the drive will ramp down to zero obeying the Jog/Slack Ramp time. Jog speeds can be selected by input T19. See the description of the start input below for further information about the jog control. See 6.3.5 JOG CRAWL SLACK / Jog mode select PIN 42.


Start/stop main contactor control Digital input START T33When a high input is applied to this terminal the controller will operate provided there are no alarms, the coast stop input (T34) is already high, the controller run input (T31) is high and the Jog input is low. When the input is removed the controller will perform a ramped stop to zero speed. The rate of deceleration will be set according to the programmed stop ramp time. The PLX models will regenerate if necessary to maintain the ramp rate. So will the PL models that have the electronic stopping facility. The PL models that do not have this facility will not be able to decelerate faster than the natural coast down rate. For all models, when the motor has reached zero speed, then the main contactor will de-energise.Note. The user control input contact must be maintained using external interlocking relay logic, or LAT1/2 on terminals 47 and 48. See 4.3.4 Using pushbuttons for simple STOP / START.The Start and Jog inputs provide the following operating featuresa) Normal runningb) Jogging with 2 selectable jog speeds and programmable contactor drop out delayc) Crawling. The crawl speed is a programmable parameterd) Slack take up with 2 selectable take up speedsWith start high and jog low, then jog going high acts as a slack take up. With start low the jog input is a jog control. The jog/slack speed 2 select input is on T19 (Jog mode select).With jog low and mode select high, then start going high acts as the crawl control. See 6.3.5 JOG CRAWLSLACK / Jog mode select PIN 42The crawl uses the run mode ramp times to accelerate, and the Stop mode ramp times to stop.


Coast stop main contactor control Digital input CSTOP T34With a high input, the controller operates normally. When the Coast Stop is at zero volts or open circuit, the main contactor is open and the drive no longer operates. If this input drops low during running then the main contactor will de-energise within 100mS and the motor will coast to rest under the influence of external factors e.g. friction and inertia, or by using an external dynamic braking resistor to dissipate the rotational energy. Note. The CSTOP must be high for at least 50mS prior to START going high. Note. When the digital outputs are shorted the 24V output will continue to operate with a current capability of 50mA. This is so that the CSTOP line does not go low and shut down the drive. If it is important that the drive continues running with a shorted digital output then a digital output set permanently high may be used as an auxiliary 24V power output for other tasks, allowing the main 24V output to be devoted entirely to the CSTOP function.

Contactor control questions and answers

Question. Why is it so important to prevent the contactor 1) Breaking current or 2) Making current?Answer. 1) Breaking current. The motor armature is an inductive load. This helps to smooth the current by storing electrical energy during a charging period and releasing it during a discharging period. However if the circuit is suddenly broken then the stored energy has nowhere to go. This results in a rapid rise in voltage as the inductor (motor armature) seeks to find a discharge path. This rapid transient may cause thyristors in the armature bridge to avalanche on and become conductive. If this happens to a pair of thyristors then an effective short circuit may be formed across the armature. Then a second effect occurs. If the motor is rotating and is suddenly shorted then the mechanical energy stored in the rotation of the motor and load isthen generated into the short circuit. This could be a destructive amount of energy. The thyristors then become permanently shorted, and the next time that the contactor closes, the supply fuses will blow.


Solution.Always let the PL/X control the contactor. It has been designed to hold the contactor in while it safely quenches the armature current. Use the CSTOP for emergency opening of the contactor via the PL/X. This terminal is electromechanical but also lets the PL/X quench the current in time. If safety codes prevent the PL/X from being used in the emergency stop sequence, ensure that the CSTOP is opened 100mS prior to the main contactor opening.Answer. 2) Making current. If the PL/X has been instructed to start making current, but the main contactor has not yet closed, then the motor will not be able to rotate. This will cause the PL/X to phase further forward in an attempt to produced the desired speed. If the contactor then closes it will present a stationary motor armature on a fully phased forward stack, straight on to the supply, producing destructive current. All this will occur in a few cycles of current which is far too fast for the speed loss alarms to operate.Solution.1) Insert an auxiliary normally open contact on the main contactor in series with the RUN input on T31.2) Alternatively use contactor wiring method shown in 4.3.2.

Question. Plenty of systems do not appear to suffer from failures due to opening the contactor incorrectly so why is it so important?Answer. If the armature current is discontinuous, which is very common, then there is much less stored inductive energy and the current also goes to zero every current cycle. This makes it highly unlikely that a destructive situation occurs. The high risk situations are regenerative applications and continuous current modes. Even in these cases it does not always result in a destructive sequence.


Question. Even if the contactor operates according to the recommendations how is protection afforded if the contactor coil supply is lost.Answer. This is a difficult problem to solve using electronics. The only reliable insurance is to insert a DC Semi-conductur fuse in the armature circuit. This fuse should open before the thyristor junction fails.Question. What if the grid system fails totally?Answer. This is not as bad as losing the contactor coil supply. Most installations naturally have other loads that provide a safe discharge path before the contactor opens.Question. What if the grid system fails for a few cycles? (Brown outs)Answer. The PL/X is designed to ride through these kinds of supply dips. As soon as it loses synchronization the armature current is quenched. The armature voltage is then monitored so that when the supply returns the PL/X picks up into the rotating load at the correct speed.Question. What other sorts of problems occur?Answer. Most problems occur when users are retro-fitting the PL/X into an existing system. Sometimes these systems have previously controlled the contactor via a PLC or Drive healthy relay. These control systems may not be interfaced correctly with PL/X and situations occur that drop out the contactor too quickly, or bring it in too late. Another common problem is that the contactor is controlled correctly for normal running but incorrectlyduring jogging or emergency stopping. Another instance is the installation is designed correctly but the commissioning engineer uses a local op station to get each PL/X going, that has an in built control problem.Summary. Use the PL/X to control the main contactor for STOP, START, jogging and emergency stop. All sequencing occurs automatically. Fit semiconductor fuses in the AC supply and armature circuits. The cost of a fuse is marginal compared to the cost of repairing a damaged drive and suffering machine downtime and engineer call out costs.


The parameters that will be selected for quick start calibration are as follows

By selecting Armature Voltage a quick start is more easily achieved.• The speed feedback is always present, and in the correct polarity.• The motor and/or load can be seen to be rotating correctly and at approximately the correct speed.• If a tacho generator or encoder is fitted then it can be checked for the correct polarity and output levels prior to including it

in the feedback loop.• Other parameters such as ramp rates and stopping modes can be checked and or set before proceeding to final accurate

calibration.• The system may need pre-test prior to shipping and no tachogenerator is available. For this quick start procedure it is only

necessary to set the above parameters.


Key functions

The user display has been designed to make programming as simple as possible. 4 keys arranged as up/down and left/right are used to step through the tree structure in their nominated direction. Notice that tapping the left key allows you to exit from any location back to the start point on the previous menu level. The selected menu is displayed on the upper line of characters. If you hold the left key down you will quickly arrive back at the default % diagnostic windows. The level number is displayed at the right hand end of the top line. As well as travelling around the tree structure the keys perform other functions. These are as follows.


When DC Motor change out or Tachogenerator change out calibration settings need to be change in program

Name plate setting need to be change and how to do it can be found from Page 60 -70 in SPRINT PLX MANUAL


END of Basic Electrical

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