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CHAPTER 4

ELECTRICAL DEVICE AND CONTROL (EDC)


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ELECTRICAL DEVICE & CONTROL(INTRODUCTION TO CONTROL ELEMENTS)

BASIC CONTROL SYSTEM (BLOCK DIAGRAM)

signal

processingoutput

signal

input

Switching

component

Amplifying

component

Electrical

Actuator

Pushbuttons etc Relay, timer etc Motor, lamp etc


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DEFINITION OF CONTROL SYSTEM

Control system- A mechanical, optical, or electronic system that is used to maintain a

desired output.

Control - Control, as applied to control circuits, is a broad term that means anything from

a simple toggle switch to a complex system of components which may include relays,

contactors, timers, switches, and indicating lights. Every electrical circuit for light or

power has control elements. One example of a simple

control circuit is a light switch used to turn lights on and off.

There are many other devices and equipment systems in industrial applications. Motor

control, for example, can be used to start and stop a motor and protect the motor,

associated machinery, and personnel. In addition, motor controllers might also be used

for reversing, changing speed, jogging, sequencing, and pilot-light indication. Control

circuits can be complex: accomplishing high degrees of automatic and precise machine

operation.


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EXAMPLESOF APPLICATION BYUSING CONTROL SYSTEM


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COMPONENTS IN CONTROL CIRCUIT

SELECTOR SWITCHES

PILOT LIG

HTS

RELAY

PUSH BUTTON

LIMIT SWITCHES


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ELECTRICAL INPUT ELEMENTS

FUNCTION OF SWITCH : To open or close the flow of current to the consuming device.

TYPE : "pushbutton switches" (push-buttons), and "control switches".

CONTROL SWITCH : In control switches, the two switching positions are mechanically interlocked. Aswitching position is maintained until the switch is activated once again.

PUSH-BUTTON : A push-button only opens or closes a current circuit for a short time. The selected

switching position is only active while the push-button is pressed.

Both switch types are available for operation with normally closed contacts, normally open contacts

or

changeover contacts.

BASIC TYPE OF SWITCH:

1. Normally open contact

2. Normally closed contact

3. Changeover switch


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ELECTRICAL DEVICE & CONTROL(ELECTRICAL INPUT COMPONENTS)


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SENSOR

Used to provide signals representative of conditions in a machine or process.

Provide analogue and discrete signals, to control devices or systems

Discrete signals

Provide ON or OFF signals

Provide information that represents the presence or absence of an object e.g. detects thepresence of bottles on a conveyor.

There are 3 types of sensor in control system:

Touch sensor limit switches

No touch sensor inductive proximity sensor, capacitive proximity sensor, ultrasonic

proximity sensor, reed switch and photoelectric sensor

Sensor ObjectDetected

Technology

Inductive Metal Electromagnetic field

Capacitive Any Electrostatic field

Ultrasonic Any Sound waves

Photoelectric Any Light


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ELECTRICAL DEVICE & CONTROL(ELECTRICAL SIGNAL PROCESSING COMPONENTS)

CONTROL RELAYS

Relay is an electro mechanical device which is commonly used to connect two different circuits. It

can connect a low voltage circuit to a high voltage circuit or a low current circuit to a high current

circuit or simply to isolate two circuits.

The simplest relay has one set of contacts (commonly called "change-over" contacts). Inside the

relay is a coil (called a solenoid) and when the coil is energised, the centre core of the solenoid

becomes magnetised and moves an arm closer to the coil. A "contact" is connected to this arm and

the contact touches another contact to complete a circuit.

The contacts are labelled "common" for the moving contact, "normally open" and "normally

closed."


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RELAY

OPERA

TION Contact Type: Normally Open (NO) & Normally Closed (NC)

When power is applied to the control circuit, the electromagnetic coil will be energized.

The resultant electromagnetic field pulls the armature and contacts toward the electromagnet,

closing the contacts. This allows current to flow through the contacts.

When power is removed, spring tension pushes the armature away, opening the contacts.


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BASIC CONSTRUCTION OF RELAY

Coil Energized / de-energized

Contact open / closed


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CONTACTOR

Most motor applications require the use of remote control devices to start and stop

the motor.

Magnetic contactors are commonly used to provide this function.

Contactors are also used to control distribution of power in lighting and heatingcircuits.


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BASIC CONSTRUCTION OF CONTACTOR

CONTROL CIRCUIT POWER CIRCUIT


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BASIC OPERATION OF CONTACTOR


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BASIC OPERATION OF CONTACTOR


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TIMER RELAY or TIMER

Used in control switching operations involving time delay.

Available timing range from 0.05 sec to 10 hours.


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TIMER RELAY

Two types :On-delay and Off delay.

An upward pointing arrow indicates On-delay action.

A downward arrow indicates Off-delay.

On-delay functioning means that once a timer has received a signal to turnon, its output will change state after a predetermined delay.

Off-delay timers will change state at a predetermined time after they have

received a signal to turn off.


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TIMER RELAY


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ELECTRICAL DEVICE & CONTROL(ELECTRICAL SAFETY COMPONENTS)

OVERLOAD RELAY

Overload relays are specialized circuit breakers used with industrial motors to protect the

motors from damages caused by overload or electrical faults.

Single-phase and multi-phase power systems typically include an overload relay for

interrupting power in the power conductors when a fault condition occurs, such as a ground

fault, phase loss, overcurrent, or undercurrent condition.

OVERLOAD

RELAY


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ELECTRICAL DEVICE & CONTROL(ELECTRICAL SAFETY COMPONENTS)

MOTOR STARTER

Contactor and overload relays are separate control devices. When a contactor is

combined with an overload relay, it is called a motor starter.


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ELECTRICAL DEVICE & CONTROL(ELECTRICAL OUTPUT COMPONENTS)

LINE DIAGRAM

POWER CIRCUIT AND CONTROL CIRCUIT


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ELECTRICAL DEVICE & CONTROL(CIRCUIT DESIGN)

INTRODUCTION TO ELECTRICAL CIRCUIT


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ELECTRICAL SYMBOL (INPUT / CONTACT)


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ELECTRICAL SYMBOL (OUTPUT)


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ELECTRICAL SYMBOL


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COMBINATION OF SIGNAL INPUT

Switching ON


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COMBINATION OF SIGNAL INPUT

Switching OFF


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Installation Example #1 (Series)

11 12

23 24

31 32

43 44H1

H2

H3

H1

H2

H3

11 12

23 24

31 32

43 44

11 12

23 24

31 32

43 44

11 12

23 24

31 32

43 44

0V

24V


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11 12

23 24

31 32

43 44

H1

H2

H3

H1

H2

H3

11 12

23 24

31 32

43 44

11 12

23 24

31 32

43 44

11 12

23 24

31 32

43 44

0V

24V Installation Example #2 (Parallel)


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CIRCUIT DIAGRAM USING RELAY


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CIRCUIT DIAGRAM USING RELAY (LATCHING/HOLDING)

LATCHING/HOLDING


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CIRCUIT DIAGRAM (POWER AND CONTROL CIRCUIT)


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Installation Example #1 (Using Relay)

H1

H2

H3

H1

H2

H3

11 12

23 24

31 32

43 44

11 12

23 24

31 32

43 44

0V

24V

A1 A2

41 52

13 14

51 62

23 24

61 72

33 34


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Installation Example #1 (Latching)

H1

H2

H3

H1

H2

H3

11 12

23 24

31 32

43 44

11 12

23 24

31 32

43 44

0V

24V

A1 A2

41 52

13 14

51 62

23 24

61 72

33 34


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Installation Example #3 (Control Circuit)


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L2

L1

A1 A2

41 52

13 14

51 62

23 24

61 72

33 34

1 2

3 4

5 6

95 96

97 98

1 2

3 4

5 6

1 2

3 4

1 2

3 4

5 6

Installation Example #3 (Power Circuit)

L3 U1 V1 W1

U2 V2 W2


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EXERCISE

1. Press (S1 AND S2) OR S3 H1 ON

2. Press (S1 OR S2) AND S3 H1 ON

3. Press S1 AND S2 H1 ON

Press S3 OR S4 H1 OFF

4. Press S1 OR S2 H1, H2 ON

Press S3 AND S4 H1, H2 OFF

5. Press (S1 OR S2) AND S3 H1 ON, H2 ON

Press S1 AND S2 H1 OFF, H2 OFF6. Press S1 H1 ON, H2 OFF, H3 ON, H4 ON

Press S2 H1 OFF, H2 ON, H3 OFF, H4 ON


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Press (S1 AND S2) OR S3 H1 ON

ANSWERPress (S1 OR S2) AND S3 H1 ON


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ANSWERPress S1 AND S2 H1 ON

Press S3 OR S4 H1 OFF

Press S1 OR S2 H1, H2 ON

Press S3 AND S4 H1, H2 OFF


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DESIGN CIRCUIT DIAGRAM USINGSEQUENCE CHART (GRAFCET)

CONDITION (OUTPUT)

(LAMP H1 ON)

0

1

INITIAL POSITION(LAMP H1 OFF)

TRANSITION (INPUT)(PRESSS1 AND S2)


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DESIGN CIRCUIT DIAGRAM USINGBLOCK SEQUENCE (GRAFCET)


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UP

RIGHT

LEFT

DOWN

WAIT

UP

DOWN

LEFT


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PRACTICAL TASK1. PERFORM THIS CONTROL CIRCUIT.

TRAFFIC LIGHT CONTROL CIRCUIT 2 LAMPS


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PRACTICAL TASK2. PERFORM THIS CONTROL CIRCUIT.

RUNNING LIGHT CONTROL CIRCUIT 3 LAMPS

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