automatic power factor corrector using arduino

Automatic power factor corrector

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Chapter 1

Introduction


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1 Introduction:

In the present technological revolution, power is very precious and the power system is

becoming more and more complex with each passing day. As such it becomes necessary to

transmit each unit of power generated over increasing distances with minimum loss of

power. However, with increasing number of inductive loads, large variation in load etc. the

losses have also increased manifold. Hence, it has become prudent to find out the causes of

power loss and improve the power system. Due to increasing use of inductive loads, the load

power factor decreases considerably which increases the losses in the system and hence

power system losses its efficiency.

An Automatic power factor correction device reads power factor from line voltage and

line current by determining the delay in the arrival of the current signal with respect to

voltage signal from the source with high accuracy by using an internal timer. It determines

the phase angle lag (ø) between the voltage and current signals and then determines the

corresponding power factor (cos ø). Then the microcontroller calculates the compensation

requirement and accordingly switches on the required number of capacitors from the

capacitor bank until the power factor is normalized to about unity.

Automatic power factor correction techniques can be applied to industrial units, power

systems and also households to make them stable. As a result the system becomes stable and

efficiency of the system as well as of the apparatus increases. Therefore, the use of

microcontroller based power factor corrector results in reduced overall costs for both the

consumers and the suppliers of electrical energy.

Power factor correction using capacitor banks reduces reactive power consumption

which will lead to minimization of losses and at the same time increases the electrical

system‘s efficiency. Power saving issues and reactive power management has led to the

development of single phase capacitor banks for domestic and industrial applications. The

development of this project is to enhance and upgrade the operation of single phase capacitor

banks by developing a micro-processor based control system.

The control unit will be able to control capacitor bank operating steps based on the

varying load current. Current transformer is used to measure the load current for sampling

purposes. Intelligent control using this micro-processor control unit ensures even utilization

of capacitor steps, minimizes number of switching operations and optimizes power factor


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correction. The Choke used in the Compact Fluorescent Lamp (CFL) will be used as an

Inductive load.


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Chapter 2

Review of Literature


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2.1 Power Factor:

Power factor is an energy concept that is related to power flow in electrical systems.

To understand power factor, it is helpful to understand three different types of power in

electrical systems.

Real Power is the power that is actually converted into useful work for creating heat,

light and motion. Real power is measured in kilowatts (kW) and is totalized by the electric

billing meter in kilowatt-hours (kWh). An example of real power is the useful work that

directly turns the shaft of a motor Reactive Power is the power used to sustain the

electromagnetic field in inductive and capacitive equipment. It is the non- working power

component. Reactive power is measured in kilovolt-amperes reactive (kVAR). Reactive

power does not appear on the customer billing statement.

Total Power or Apparent power is the combination of real power and reactive power.

Total power is measured in kilovolt-amperes (kVA) and is totalized by the electric billing

meter in kilovolt-ampere-hours (kVAh). Power factor (PF) is defined as the ratio of real

power to total power, and is expressed as a percentage (%).

Or

Power factor cos φ is defined as the ratio between the Active component IR and the

total value of the current I; φ is the phase angle between the voltage and the current.

Figure 1 Power Triangle.

Power factor = 𝐑𝐞𝐚𝐥 𝐏𝐨𝐰𝐞𝐫 (𝐤𝐖𝐇)

𝐓𝐨𝐭𝐚𝐥 𝐏𝐨𝐰𝐞𝐫 (𝐤𝐕𝐀𝐇)𝒙𝟏𝟎𝟎


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2.2 Power Factor Correction:

Power factor correction is the process of compensating for the lagging current by

creating a leading current by connecting capacitors to the supply. A sufficient capacitance

can be connected so that the power factor is adjusted to be as close to unity as possible.

Power factor correction (PFC) is a system of counteracting the undesirable effects of

electric loads that create a power factor that is less than one (1). Power factor correction

may be applied either by an electrical power transmission utility to improve the stability

and efficiency of the transmission network or, correction may be installed by individual

electrical customers to reduce the costs charged to them by their electricity service

provider.

An electrical load that operates on alternating current requires apparent power, which

consists of real power and reactive power. Real power is the power actually consumed by

the load. Reactive power is repeatedly demanded by the load and returned to the power

source, and it is the cyclical effect that occurs when alternating current passes through a

load that contains a reactive component. The presence of reactive power causes the real

power to be less than the apparent power, so the electric load has a power factor of less

than one.

The reactive power increases the current flowing between the power source and the

load, which increases the power losses through transmission and distribution lines. This

results in operational and financial losses for power companies. Therefore, power

companies require their customers, especially those with large loads, to maintain their

power factors above a specified amount especially around ally 0.90 or higher, or be subject

to additional charges. Electrical engineers involved with the generation, transmission,

distribution and consumption of electrical power have an interest in the power factor of

loads because power factors affect efficiencies and costs for both the electrical power

industry and the consumers. In addition to the increased operating costs, reactive power

can require the use of wiring, switches, circuit breakers, transformers and transmission

lines with higher current capacities.

Power factor correction attempts to adjust the power factor of an AC load or an AC

power transmission system to unity (1) through various methods. Simple methods include

switching in or out banks of capacitors or inductors which act to cancel the inductive or

capacitive effects of the load, respectively. example, the inductive effect of motor loads


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may be offset by locally connected capacitors. It is also possible to effect power factor

correction with an unloaded synchronous motor connect across the supply. The power

factor of the motor is varied by adjusting the field excitation and be made to behave like a

excited. Non-linear loads create harmonic currents in addition to the original AC current

capacitor when over

There are two types of PFCs:

1. Passive.

2. Active

2.2.1 Passive PFC:

The simplest way to control the harmonic current is to use a filter: it is possible to

design a filter that passes current only at line frequency 50Hz. This filter reduces the

harmonic current, which means that the non-linear device now looks like a linear

load. At this point the power factor can be brought to near unity, using capacitors or

inductors as required. This filter requires large-value high-current inductors,

however, which are bulky and expensive.

A passive PFC requires an inductor larger than the inductor in an active PFC, but

costs less. This is a simple way of correcting the nonlinearity of a load is by using

capacitor banks. It is not as effective as active PFC. Passive PFCs are typically more

power efficient than active PFC. (Wolfle, W.H2003).

2.2.2 Active PFC:

An "active power factor corrector" (active PFC) is a power electronic system that

controls the amount of power drawn by a load in order to obtain a power factor as

close as possible to unity. In most applications, the active PFC controls the input

current of the load so that the current waveform is proportional to the mains voltage

waveform (a sine wave). The purpose of making the power factor as close to unity

(1) as possible is to make the load circuitry that is power factor corrected appear

purely resistive (apparent power equal to real power).

In this case, the voltage and current are in phase and the reactive power

consumption is zero. This enables the most efficient delivery of electrical power from


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the power company to the consumer. Some types of active PFC are: Boost, Buck and

Buck-boost. Active power factor correctors can be single-stage or multi-stage. Active

PFC is the most effective and can produce a PFC of 0.99 (99%). (Fairchild 2004)

2.2.3 Advantages of Power Factor Correction:

There are several advantages in utilizing power factor correction capacitors.

These include:

• Reduced demand charges.

• Increased load carrying capabilities in existing circuits.

• Improved voltage

• Power system loses

2.3 The disadvantages of a low power factor:

Power factor plays an important role in AC circuits and power dissipation in the power

system is dependent on the power factor of the system. We know that the power in a three

phase AC circuit is:

P = √3 V × I cosφ

And the current on a three phase AC circuit is:

I = P

3xVx cos𝛗

Also the power in a single Phase AC circuit is:

P = V × I cosφ

And the current on a three phase AC circuit is:

I = P

Vx cos𝛗

It is evident from the equations for the currents that the current is proportional to cosφ

i.e. power factor. In other words, as the power factor increases the net current flowing in

the system decreases and when the power factor decrease the net current in the system

increases.


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2.3.1 The advantages of an improved power factor:

Higher power factors result in:

• Reduction in system losses, and the losses in the cables, lines, and feeder

circuits and therefore lower cable sizes could be opted for.

• Improved system voltages, thus enable maintaining rated voltage to motors,

pumps and other equipment. The voltage drop in supply conductors is a resistive

loss, and wastes power heating the conductors. Improving the power factor,

especially at the motor terminals, can improve the efficiency by reducing the

line current and the line losses.

• Improved voltage regulation.

• Increased system capacity, by release of KVA capacity of transformers and

cables for the same KW, thus permitting additional loading without immediate

expansion.

2.4 Power Factor and Electrical Loads:

In general, electrical systems are made up of three components: resistors, inductors and

capacitors. Inductive equipment requires an electromagnetic field to operate. Because of

this, inductive loads require both real and reactive power to operate. The power factor of

inductive loads is referred to as lagging, or less than 100%, based upon our power factor

ratio.

In most commercial and industrial facilities, a majority of the electrical equipment acts

as a resistor or an inductor. Resistive loads include incandescent lights, baseboard heaters

and cooking ovens. Inductive loads include fluorescent lights, AC induction motors, arc

welders and transformers.

Typical average power factor values for some inductive loads:


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Load PF %

Induction Motor 70-90

Small Adjustable Speed Drive 90-98

Fluorescent Lights

Magnetic Ballast & Electronic Ballast 70-80 & 90-95resp.

Arc Welders 35-80

2.5 Capacitor:

A capacitor (originally known as condenser) is a passive two-terminal electrical

component used to store energy in an electric field. The forms of practical capacitors vary

widely, but all contain at least two electrical conductors separated by a dielectric

(insulator); for example, one common construction consists of metal foils separated by a

thin layer of insulating film. Capacitors are widely used as parts of electrical circuits in

many common electrical devices. When there is a potential difference (voltage) across the

conductors, a static electric field develops across the dielectric, causing positive charge to

collect on one plate a negative charge on the other plate.

Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single

constant value, capacitance, measured in farads. This is the ratio of the electric charge on

each conductor to the potential difference between them. The capacitance is greatest when

there is a narrow separation between large areas of conductor; hence capacitor conductors

are often called plates, referring to an early means of construction. In practice, the dielectric

between the plates passes a small amount of leakage current and also has an electric field

strength limit, resulting in a breakdown voltage, while the conductors and leads introduce

an undesired inductance and resistance. Capacitors are widely used in electronic circuits

for blocking direct current while allowing alternating current to pass, in filter networks, for

smoothing the output of power supplies, in the resonant circuits that tune radios to

particular frequencies, in electric power transmission systems for stabilizing voltage and

power flow, and for many other purposes.

Capacitors also require reactive power to operate. However, capacitors and inductors

have an opposite effect on reactive power. The power factors for capacitors are leading.


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Therefore capacitors are installed to counteract the effect of reactive power used by

inductive equipment. (Hammond, P 1964).

2.5.1 Power Factor capacitors:

Power factor capacitors may conveniently be switched on and off with individual

motors. This assures that the capacitor is energized only during the times when the

motor is energized - when you need power factor correction. For this type of

application, typically a Fixed Capacitor Bank is used. This is the simplest and most

economical form of power factor correction. Depending on the manner in which you

connect the capacitor, you may or may not need to include fuses Harmonics will

reduce the life of power factor capacitors. Whenever there are harmonic producing

loads on the power system, the capacitor bank should include a capacitor protection

reactor that will detune ‖ the capacitor bank to a frequency where no harmonic energy

exists. Instead of the capacitor protection reactor we intend using a microcontroller

to detune the capacitor bank to a frequency where no harmonics energy can exist

thereby improving the correction of Power factor.

2.5.2 Uses of Automatic Power Factor Capacitors:

When the load conditions and power factor in a facility change frequently, the

demand for power factor improving capacitors also changes frequently. In order to

assure that the proper amount of power factor capacitor kVARs are always

connected to the system (without over-correcting), an Automatic Type Capacitor

System should be used for applications involving multiple loads. A microcontroller

automatic compensation system is formed by:

• Some sensors detecting current and voltage signals;

• An intelligent unit that compares the measured power factor with the desired

one and operates the connection and disconnection of the capacitor banks with

the necessary reactive power (power factor regulator);

• An electric power board comprising switching and protection devices;

• Some capacitor banks.


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2.6 Power Factor in Resistor, Inductance and capacitance circuit:

In a purely resistive AC circuit, voltage and current waveforms are in phase, changing

polarity at the same instant in each cycle. Where reactive loads are present, such as with

capacitors or inductors, energy storage in the loads result in a time difference between the

current and voltage waveforms. This stored energy returns to the source and is not

available to do work at that load. A circuit with low power factor will have a higher

current to transfer a given quality of real power than a circuit with a high power factor. In

order to get the current reading with the oscilloscope for the diagram for pure resistive,

capacitive and inductive loads below. A resistor with a negligible value was introduced in

the circuit and the current value was measured across it. This assumption was made using

ohms law:

V=IR but R‘s value is negligible therefore V=I, This assumption was used to get the

waveform for current

Figure 2. Pure resistive load circuit.


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Figure 3. The waveform for pure resistive load, Voltage and current are in phase.

Figure 4. Pure Capacitive load circuit.


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Figure 5. The waveform for pure capacitive load, Voltage lag current by 90 .

Figure 6. Pure Inductive load circuit.


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Figure 7: The wave form for pure inductive load, the current lags the voltage by 90°C.

2.7 Power factor Harmonics:

Harmonics are sinusoidal voltages or currents having frequencies that are whole

multiples of the frequency at which the supply system is designed to operate (e.g. 50Hz or

60 Hz). E.g. a 250 Hz sine-wave signal, superposed onto the fundamental 50 Hz mains

frequency, will be designated as the 5th harmonic or as the harmonic of 5th order (5 x 50

Hz). Any signal component having a frequency which is not an integer multiple of the

fundamental frequency is designated as an inter harmonic component or referred to more

simply as an inter harmonic. Harmonics and inter harmonics are basically the result of

modern developments in electricity utilization and the use of electronic power conditioning

modules. Using switching power supplies to control loads and to reduce power

consumption results in unwanted frequencies superimposed on the supply voltage. The

presence of voltage at other frequencies is, as far as possible, to be avoided.


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2.7.1 Potential Sources of Harmonics:

• Switched mode power supplies Dimmes, Current Regulators, Frequency

Converters.

• Voltage source inverters with pulse width modulated converters.

• Low power consumption lamps.

• Electrical arc-furnaces.

• Arc welding machines.

• Induction motors with irregular magnetizing current associated with saturation of

the iron.

• All equipment with built-in switching devices or with internal loads with

nonlinear voltage/current characteristics.

2.7.2 Effects of Harmonics on Mains supplies:

• Distortion of main supply voltage, unwanted currents flowing in the supply

network generate additional energy losses.

• Defective operation of regulating devices, disturbed operation of florescent

lamps, television receivers or other equipment.

• Malfunction of ripple control and other mains signaling systems, protective

relays and, possibly, other of control systems.

• Additional losses in capacitors and rotating machines.

• Additional acoustic noise from motors and other apparatus, reducing the

efficiency of motors.

• Telephone interference.

• High harmonic amplitudes may not only cause malfunctions, additional losses

and overheating, but also overload the power distribution network and overheat

the neutral conductor and cause it to burn out.


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2.7.3 For the purpose of harmonic current limitation, equipment is classified

as follows:

Class A: Balanced three-phase equipment;

• Household appliances excluding equipment identified as Class D;

• Tools excluding portable tools;

• Dimmers for incandescent lamps;

• Audio equipment;

• Equipment not specified in one of the three other classes shall be

considered Class A equipment

Class B: Portable tools.

Class C: Lighting equipment.

Class D: Equipment having a specified power < 600W of the following types:

• Personal computers and personal monitors;

• Television receivers.

2.7.4 Fixed Versus Automatic Capacitors:

Fixed capacitor banks are always on at all times, regardless of the load in the

facility, while an automatic capacitor bank varies the amount of correction supplied

to an electrical system. An automatic capacitor is much more expensive per kVAr

than a fixed system. 100 kVAr of fixed capacitors will save as much power factor

penalties as a 100 kVAr automatic capacitor. Generally, when a capacitor is

connected to a system there is a reduction in amperage on the system. This reduction


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in amperage reduces the voltage drop across a transformer, which results in a higher

voltage in the system. If 100 kVAr is connected to a 1000 KVA transformer, there is

approximately a ¾% voltage rise on the system (if there are no other loads on the

system). The more kVAr connected, the higher the voltage rise. This voltage rise is

counter acted by the increase of load in the facility. Typically, in the night and on

weekends, utility voltage are higher than normal, and facilities that are not normally

loaded during these times, could experience a higher than normal voltage rise if too

much capacitance is connected to their system. Based on this, we generally limit

fixed capacitors to 10% to 15% fixed kVAr to KVA of transformer size. We would

recommend an automatic capacitor bank if the amount of kVAr exceeds 20% of the

KVA size of the transformer.


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Chapter 3

Proposed System


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Proposed System:

Microcontroller base automatic controlling of power factor with load monitoring is

shown in fig.8.

Fig.8 block of PFC using ATMEGA 328

The principal element in the circuit is PIC microcontroller. The current and voltage

single are acquired from the main AC line by using Current Transformer and Potential

Transformer. These acquired signals are then pass on the zero crossing detectors. Bridge

rectifier for both current and voltage signals transposes the analog signals to the digital signal.

Microcontroller read the RMS value for voltage and current used in its algorithm to select the

value of in demand capacitor for the load to correct the power factor and monitors the behavior

of the enduring load on the basis of current depleted by the load. In case of low power factor

Microcontroller send out the signal to switching unit that will switch on the in demand value of

capacitor. The tasks executed by the microcontroller for correcting the low power factor by

selecting the in demand value of capacitor and load monitoring are shown in LCD.


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Chapter 4

System Design


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4.1 Principle:

Fig 9: Block Diagram of Automatic Power Factor Correction Circuit.

The above given circuit for Automatic Power Factor detection and correction operates

on the principal of constantly monitoring the power factor of the system and to initiate the

required correction in case the power factor is less than the set value of power factor. The

current and voltage signals are sampled by employing instrument transformers connected

in the circuit. The instrument transformers give stepped down values of current and voltage,

whose magnitude is directly proportional to the circuit current and voltage. The sampled

analog signals are converted to suitable digital signals by the zero crossing detectors, which

changes state at each zero crossing of the current and voltage signals. The ZCD signals are

then added in order to obtain pulses which represent the time difference between the zero

crossing of the current and voltage signals.

The time period of these signals is measured by the internal timer circuit of the Arduino

by using the function pulseIn(), which gives the time period in micro seconds. The time

period obtained is used to calculate the power factor of the circuit. Now if the calculated

power factor is less than the minimum power factor limit set at about 0.96-0.98, then the


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microcontroller switches on the require number of capacitors until the power factor is

greater than or equal to the set value.

4.2 Circuit Description:

Automatic Power Factor Correction system is based on the AVR microcontroller

ATmega 328. The voltage and current in the circuit are stepped down using a potential

transformer and a current transformer respectively. These transformed a.c signals are next

fed to a Zero Crossing Detector (ZCD) circuit. The output of the Zero Crossing Detector

(ZCD) is a square wave, in which each change of state represents a zero crossing of the a.c

waveform. The signal goes high on the first zero crossing of the current or voltage

waveform and then goes low on the next zero crossing of the signal, thereby generating a

square wave. Two separate Zero Crossing Detector (ZCD) circuits are used for voltage and

current waveform. The two square waves are then summed using an Exclusive OR (X-OR)

gate. The output of the summer gives the phase angle difference which is given to the

Arduino microcontroller on one of its digital I/O pins (pin 3).

The value on the pin is read using the function pulseIn(pin, value, timeout), where the

parameters pin depicts the number of the pin on which you want to read the pulse. (int),

value depicts the type of pulse to read i.e., either HIGH or LOW. (int) and timeout

(optional) depicts the number of microseconds to wait for the pulse to start, default is one

second (unsigned long). The function reads a pulse (either HIGH or LOW) on a pin. For

example, if value is HIGH, pulseIn() waits for the pin to go HIGH, starts timing, then waits

for the pin to go LOW and stops timing. It finally returns the length of the pulse in

microseconds or gives up and returns 0 if no pulse starts within a specified time out.

The timing of this function has been determined empirically and will probably show

errors in longer pulses. Hence, it works efficiently on pulses from 10 microseconds to 3

minutes in length. The difference is measured with high accuracy by using internal timer.

This time value obtained is in microseconds (µs). It is converted in milliseconds (ms) and

is then calibrated as phase angle φ using the relation:

𝛗 =t

T∗ 360

http://arduino.cc/en/Reference/Constants







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....equation

Where:

φ = difference in phase angle

t = time difference in milliseconds (ms);

T = the time period of one AC cycle (i.e., 20ms);

The corresponding power factor is calculated by taking cosine of the phase angle

obtained above (i.e., cosφ). The values are displayed in the serial monitor which in this

case is the computer screen. The display can also be obtained on a separate display by using

the serial transmission pins: Serial Transmission (Tx) and Serial Reception (Rx) of the

Arduino but that would require appropriate interfacing circuitry. The microcontroller then

based on the algorithm then switches on the required number of capacitors from the

capacitor bank by operating the electromagnetic relays until the power factor is normalized

to the set limit.

4.3 Power Supply:

A good power supply is very essential as it powers all the other modules of the circuit.

In this power supply we use step-down transformer, IC regulators, Diodes, Capacitors

and resistors (presets and pots).

4.3.1 Components:

A. Voltage Transformer:

A voltage transformer or a potential transformer is a wire-wound, static

electromagnetic device that is used to transform the voltage level of input voltage.

A transformer has two windings: a primary winding to which the input is

connected and a secondary winding from which the transformed voltage is


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obtained. The input voltage is transformed (either stepped up or down) according

to the turns ratio of the primary and the secondary windings. The transformer used

in the power supply here gives an output of +12V or -12V or a total of 24V for an

input voltage of 230V.

Fig 10: Voltage Transformer/Potential transformer

Voltage transformers are a parallel connected type of instrument

transformer. They are designed to present negligible load to the supply being

measured and have an accurate voltage and phase relationship to enable

accurate secondary connected metering

The voltage transformer used in the power supply is designed for single

phase 230 V, 50Hz. It has three terminals in the secondary side, the output is

taken from the two end wires and is equal to 24V, because the voltage

regulator should have an input voltage much greater than the output voltage.

B. Diodes:

In electronics a diode is a two-terminal electronic component with asymmetric

conductance. It has low (ideally zero) resistance to current flow in one direction

and high (ideally infinite) resistance(tunnel diodes, Gunn diodes, IMPATT

diodes), and to produce light (light emitting diodes). Tunnel diodes exhibit

negative resistance, which makes them useful in certain types of circuits.

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C. Resistors:

A resistor is a passive two-terminal electrical component that implements

electrical resistance as a circuit element.

Fig 11: Carbon Film Resistor

The current through a resistor is in direct proportion to the voltage across the

resistor's terminals. This relationship is represented by:

𝐼 =V

R

where I is the current through the conductor in units of amperes, V is the

potential difference measured across the conductor in units of volts, and R is the

resistance of the conductor in units of ohms (symbol: Ω). The ratio of the voltage

applied across a resistor's terminals to the intensity of current in the circuit is

called its resistance, and this can be assumed to be a constant (independent of the

voltage) for ordinary resistors working within their ratings.

Resistors are common elements of electrical networks and electronic circuits and

are ubiquitous in electronic equipment. Practical resistors can be made of various

compounds and films, as well as resistance wire (wire made of a high-resistivity

alloy, such as nickel-chrome). Resistors are also implemented within integrated

circuits, particularly analog devices, and can also be integrated into hybrid and

printed circuits.

The electrical functionality of a resistor is specified by its resistance: common

commercial resistors are manufactured over a range of more than nine orders of

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magnitude. When specifying that resistance in an electronic design, the required

precision of the resistance may require attention to the manufacturing tolerance

of the chosen resistor, according to its specific application. The temperature

coefficient of the resistance may also be of concern in some precision

applications. Practical resistors are also specified as having a maximum power

rating which must exceed the anticipated power dissipation of that resistor in a

particular circuit: this is mainly of concern in power electronics applications.

Resistors with higher power ratings are physically larger and may require heat

sinks. In a high-voltage circuit, attention must sometimes be paid to the rated

maximum working voltage of the resistor. While there is no minimum working

voltage for a given resistor, failure to account for a resistor's maximum rating may

cause the resistor to incinerate when current is run through it.

D. Light Emitting Diodes (LED):

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as

indicator lamps in many devices and are increasingly used for general lighting.

Appearing as practical electronic components in 1962, early LEDs emitted low-

intensity red light, but modern versions are available across the visible, ultraviolet,

and infrared wavelengths, with very high brightness.

Fig12: Light Emitting Diodes (LED)

When a light-emitting diode is switched on, electrons are able to recombine with

holes within the device, releasing energy in the form of photons. This effect is

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http://en.wikipedia.org/wiki/Photon

http://en.wikipedia.org/wiki/Photon


28 | P a g e

called electroluminescence, and the color of the light (corresponding to the energy

of the photon) is determined by the energy band gap of the semiconductor. An

LED is often small in area (less than 1 mm2), and integrated optical components

may be used to shape its radiation pattern. LEDs have many advantages over

incandescent light sources including lower energy consumption, longer lifetime,

improved physical robustness, smaller size, and faster switching. However, LEDs

powerful enough for room lighting are relatively expensive, and require more

precise current and heat management than compact fluorescent lamp sources of

comparable output.

Light-emitting diodes are used in applications as diverse as aviation lighting,

automotive lighting, advertising, general lighting and traffic signals. LEDs have

allowed new text, video displays, and sensors to be developed, while their high

switching rates are also useful in advanced communications technology. Infrared

LEDs are also used in the remote control units of many commercial products

including televisions, DVD players and other domestic appliances. LEDs are used

to create a new form of wireless internet access called Li-Fi, or light fidelity. LEDs

are also used in seven-segment display.

Fig13: Schematic of an LED

http://en.wikipedia.org/wiki/Electroluminescence



http://en.wikipedia.org/wiki/Band_gap



http://en.wikipedia.org/wiki/Radiation_pattern



http://en.wikipedia.org/wiki/Fluorescent_lamp



http://en.wikipedia.org/wiki/Navigation_light#Aviation_navigation_lights



http://en.wikipedia.org/wiki/Automotive_lighting#Light_emitting_diodes_.28LED.29




http://en.wikipedia.org/wiki/Traffic_signal

http://en.wikipedia.org/wiki/Traffic_signal

http://en.wikipedia.org/wiki/Li-Fi




http://en.wikipedia.org/wiki/Seven-segment_display






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E. Electrolytic Capacitor:

An electrolytic capacitor is a capacitor that uses an electrolyte (an ionic

conducting liquid) as one of its plates to achieve a larger capacitance per unit

volume than other types, but with performance disadvantages. All capacitors

conduct alternating current (AC) and block direct current (DC) and can be used,

amongst other applications, to couple circuit blocks allowing AC signals to be

transferred while blocking DC power, to store energy, and to filter signals

according to their frequency. Most electrolytic capacitors are polarized; hence,

they can only be operated with a lower voltage on the terminal marked "-" without

damaging the capacitor. This generally limits electrolytic capacitors to supply-

decoupling and bias-decoupling, since signal coupling usually involves both

positive and negative voltages across the capacitor. The large capacitance of

electrolytic capacitors makes them particularly suitable for passing or bypassing

low frequency signals and storing large amounts of energy. They are widely used

in power supplies and for decoupling unwanted AC components from DC power

connections.

Fig.14: Electrolytic Capacitors (200V, 1000˚F)

Super capacitors provide the highest capacitance of any practically available

capacitor, up to thousands of farads, with working voltages of a few volts.

Electrolytic capacitors range downwards from tens (exceptionally hundreds) of

thousands of microfarads to about 100 nano farads smaller sizes are possible but

http://en.wikipedia.org/wiki/Capacitor



http://en.wikipedia.org/wiki/Electrolyte



http://en.wikipedia.org/wiki/Capacitance



http://en.wikipedia.org/wiki/Alternating_current



http://en.wikipedia.org/wiki/Direct_current




http://en.wikipedia.org/wiki/Coupling_(electronics)

http://en.wikipedia.org/wiki/Coupling_(electronics)




http://en.wikipedia.org/wiki/Electronic_filter



http://en.wikipedia.org/wiki/Power_supply



http://en.wikipedia.org/wiki/Supercapacitors

http://en.wikipedia.org/wiki/Supercapacitors

http://en.wikipedia.org/wiki/Farad




30 | P a g e

have no advantage over other types. Other types of capacitor are available in sizes

typically up to about ten microfarads, but the larger sizes are much larger and

more expensive than electrolytic (film capacitors of up to thousands of

microfarads are available, but at very high prices). Electrolytic capacitors are

available with working voltages up to about 500V, although the highest

capacitance values are not available at high voltage. Working temperature is

commonly 85°C for standard use and 105° for high-temperature use; higher

temperature units are available, but uncommon.

Unlike other types of capacitor, most electrolytic capacitors require that the

voltage applied to one terminal (the anode) never become negative relative to the

other (they are said to be "polarized"), so cannot be used with AC signals without

a DC polarizing bias (non-polarized electrolytic capacitors are available for

special purposes).

Capacitance tolerance and stability, equivalent series resistance (ESR) and

dissipation factor are significantly inferior to other types of capacitors, leakage

current is higher and working life is shorter. Capacitors can lose capacitance as

they age and lose electrolyte, particularly at high temperatures. A common failure

mode which causes difficult-to-find circuit malfunction is progressively

increasing ESR without change of capacitance, again particularly at high

temperature. Large ripple currents flowing through the ESR generate harmful

heat.

Two types of electrolytic capacitor are in common use: aluminum and tantalum.

Tantalum capacitors have generally better performance, higher price, and are

available only in a more restricted range of parameters. Solid polymer dielectric

aluminum electrolytic capacitors have better characteristics than wet-electrolyte

types in particular lower and more stable ESR and longer life at higher prices and

more restricted values.

F. Ceramic Capacitor:

A ceramic capacitor is a fixed value capacitor in which ceramic materials act as

the dielectric. It is constructed of two or more alternating layers of ceramic and a

metal layer acting as the electrodes. The composition of the ceramic material

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defines the electrical behavior and therefore applications of the capacitor. Ceramic

capacitors are divided into two application classes:

• Class 1 ceramic capacitors offer high stability and low losses for resonant

frequency applications.

• Class 2 ceramic capacitors offer high volumetric efficiency for buffer, by-pass

and coupling applications.

The different ceramic materials used for ceramic capacitors, para electric or

ferroelectric ceramics influences the electrical characteristics of the capacitors.

Using mixtures of para electric substances based on titanium dioxide results in

very stable and linear behavior of the capacitance value within a specified

temperature range and low losses at high frequencies. But these mixtures have a

relatively low permittivity so that the capacitance values of these capacitors are

relatively small.

Fig15: Ceramic Capacitors

Higher capacitance values for ceramic capacitors can be achieved by using

ferroelectric materials like barium titanate together with specific oxides. These

dielectric materials have higher permittivities, but at the same time their

capacitance values are more or less nonlinear over the temperature range and the

losses at high frequencies are much higher.


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G. Voltage Regulators (7805, 7809, 7812):

A voltage regulator is designed to automatically maintain a constant voltage

level. A voltage regulator may be a simple "feed-forward" design or may include

negative feedback control loops. It may use an electromechanical mechanism, or

electronic components. Depending on the design, it may be used to regulate one

or more AC or DC voltages. Electronic voltage regulators are found in devices

such as computer power supplies where they stabilize the DC voltages used by

the processor and other elements. In automobile alternators and central power

station generator plants, voltage regulators control the output of the plant. In an

electric power distribution system, voltage regulators may be installed at a

substation or along distribution lines so that all customers receive steady voltage

independent of how much power is drawn from the line.

Voltage regulator is any electrical or electronic device that maintains the voltage

of a power source within acceptable limits. The voltage regulator is needed to

keep voltages within the prescribed range that can be tolerated by the electrical

equipment using that voltage. Such a device is widely used in motor vehicles of

all types to match the output voltage of the generator to the electrical load and to

the charging requirements of the battery. Voltage regulators also are used in

electronic equipment in which excessive variations in voltage would be

detrimental.

In motor vehicles, voltage regulators rapidly switch from one to another of three

circuit states by means of a spring-loaded, double-pole switch. At low speeds,

some current from the generator is used to boost the generator‘s magnetic field,

thereby increasing voltage output. At higher speeds, resistance is inserted into the

generator-field circuit so that its voltage and current are moderated. At still higher

speeds, the circuit is switched off, lowering the magnetic field. The regulator

switching rate is usually 50 to 200 times per second.

Electronic voltage regulators utilize solid-state semiconductor devices to smooth

out variations in the flow of current. In most cases, they operate as variable

resistances; that is, resistance decreases when the electrical load is heavy and

increases when the load is lighter.

http://en.wikipedia.org/wiki/Voltage_source



http://en.wikipedia.org/wiki/Feed_forward_(control)



http://en.wikipedia.org/wiki/Negative_feedback




http://en.wikipedia.org/wiki/Control_theory

http://en.wikipedia.org/wiki/Control_theory

http://en.wikipedia.org/wiki/Mechanism_(technology)

http://en.wikipedia.org/wiki/Mechanism_(technology)










http://en.wikipedia.org/wiki/Alternator



http://en.wikipedia.org/wiki/Power_station



http://en.wikipedia.org/wiki/Electric_power_distribution




http://www.britannica.com/EBchecked/topic/394340/motor-vehicle

http://www.britannica.com/EBchecked/topic/394340/motor-vehicle

http://www.britannica.com/EBchecked/topic/357048/magnetic-field

http://www.britannica.com/EBchecked/topic/499254/resistance

http://www.britannica.com/EBchecked/topic/499254/resistance


33 | P a g e

Voltage regulators perform the same function in large-scale power-distribution

systems as they do in motor vehicles and other machines; they minimize

variations in voltage in order to protect the equipment using the electricity. In

power-distribution systems the regulators are either in the substations or on the

feeder lines themselves. Two types of regulators are used: step regulators, in

which switches regulate the current supply, and induction regulators, in which an

induction motor supplies a secondary, continually adjusted voltage to even out

current variations in the feeder line.

HERE we use 3 types of voltage regulators of lm78XX series such as 7805, 7809

and 7812.

Fig16: Pin out diagram of an LM7805 regulator


http://www.britannica.com/EBchecked/topic/182915/electricity


34 | P a g e


The LM78XX series of three terminal positive regulators are available in the

TO-220 package and with several fixed output voltages, making them useful

in a wide range of applications. Each type employs internal current limiting,

thermal shut down and safe operating area protection, making it essentially

indestructible. If adequate heat sinking is provided, they can deliver over 1A

output current. Although designed primarily as fixed voltage regulators, these

devices can be used with external components to obtain adjustable voltages

and currents.

4.1.2 Circuit Diagram:

Fig. 19: Circuit Diagram Power Supply.


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4.1.3 Explanation:

The input supply i.e., 230V, 50 Hz AC is applied across the primary of a step-

down transformer (usually a 12-0-12, i.e., the output is either 12V or 24V; a

transformer is an electromechanical static device, which transforms one voltage to

another without changing its frequency). The output is taken across the secondary

coil and is applied to a rectifier section. The rectifier section is Bridge Rectifier,

formed by arranging four IN4001 diodes in a bridge pattern. Diodes are used for

rectification purposes. The output of the bridge circuit is not pure d.c; an a.c

component is also present in the form of a ripple. In order to reduce this ripple, an

electrolytic capacitor (1000F) is connected at the output of the diode bridge. The

Cathode terminals of the diode‘s D2 & D3 are connected to the positive (+ve)

terminal of the capacitor and thus the input of the IC Regulator (7805 & 7812).

The voltage regulators here are used to obtain the fixed voltage as per

requirement. A voltage regulator is a circuit that supplies a constant voltage

regardless of changes in load currents. These IC‘s are designed as fixed voltage

regulators and with adequate heat sinking can deliver output currents in excess of

1A. The output of the IC regulator is given to the LED through resistors. When the

output of the IC is given to the LED, it gets forward biased and thus LED glows.

Similarly, for negative voltage the Anode terminals of the diodes D1 & D4 are

connected to the negative terminal of the capacitor and thus to the Input pin of the

IC regulator with respect to ground. The output of the IC regulator (7912) which is a

negative voltage is given to the terminal of LED, through resistor, which makes it

forward bias, LED conducts and thus LED gloves) Power module provides supply

to the circuit and drives all other modules . 12V battery is used as a terminal block.

The positive terminal of battery is connected to the switch. When the switch is closed

the current flows through the circuit. Switch is connected to the positive terminal of

the diode which acts as a secure connector. The diode opposes reverse current, as if

by mistake, terminals of battery gets wrongly connected, it does not allow this current

to pass and protects other equipment’s from being damaged.

An LED is used to indicate whether supply is on or not. It is connected in parallel

with supply. The negative of the diode is connected to the electrolytic capacitor of


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capacity 1000µF. It is used to prevent surges or spike to enter in the circuit.

Connecting wires act as storage elements like capacitors and inductors so when

supply is switched ‗on‘, a spike of voltage occurs across the circuit initially, so this

capacitor helps to protect the other devices of circuit from being damaged by this

spike of voltage. In parallel to this electrolytic capacitor a ceramic capacitor of 0.1µF

which is used to filter high frequency noise. One end of this capacitor is connected

to positive of LM7812, which provides a 12V regulated signal to drive L293D IC of

motor module. The negative of this IC is connected to the ground. In parallel to

LM7812 IC 7809 and 7805 regulators are connected which provides a regulated

supply of 9V and 5V respectively. The 5V supply is used to drive Arduino processing

module.

4.4 Current Transformer:

The current transformer is an instrument transformer used to step-down the current in the

circuit to measurable values and is thus used for measuring alternating currents. When the

current in a circuit is too high to apply directly to a measuring instrument, a current

transformer produces a reduced current accurately proportional to the current in the circuit,

which can in turn be conveniently connected to measuring and recording instruments. A

current Transformer isolates the measuring instrument from what may be a very high

voltage in the monitored circuit. Current transformers are commonly used in metering and

protective relays. Like any other transformer, a current transformer has a single turn wire

of a very large cross section as its primary winding and the secondary winding has a large

number of turns, thereby reducing the current in the secondary to a fraction of that in the

primary. Thus, it has a primary winding, a magnetic core and a secondary winding. The

alternating current in the primary produces an alternating magnetic field in the magnetic

core, which then induces an alternating current in the secondary winding circuit. An

essential objective of a current transformer design is to ensure the primary and secondary

circuits are efficiently coupled, so the secondary current is linearly proportional to the

primary current.


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Fig19: Secondary Winding of a Ring CT

Also known commonly as a Ring C.T, the current carrying conductor is simply passed

through the center of the winding. The conductor acts as the primary winding and the ring

contains the secondary winding.

The most common design of a Current transformer consists of a length of wire wrapped

many times around a silicon steel ring passed around the circuit being measured. The

current transformers primary circuit consists of a single turn of conductor, with a secondary

of many tens or hundreds of turns. The primary winding may be a permanent part of the

current transformer, with a heavy copper bar to carry current through the magnetic core.

Shapes and sizes may vary depending upon the end user or switch gear manufacturer.

Typical examples of low voltage, single ratio metering current transformers are either ring

type or plastic molded case. High-voltage current transformers are mounted on porcelain

insulators to isolate them from ground.

A 220Ω resistor is connected across the output terminals of the current transformer‘s

secondary winding, this is because the microcontroller cannot sense the current directly but

it is applied in the form of a voltage across a resistor.

4.5 Potential Transformer:

A potential transformer, a voltage transformer or a laminated core transformer is the

most common type of transformer widely used in electrical power transmission and

appliances to convert mains voltage to low voltage in order to power low power electronic


38 | P a g e

devices. They are available in power ratings ranging from mW to MW. The Insulated

laminations minimize eddy current losses in the iron core.

A potential transformer is typically described by its voltage ratio from primary to

secondary. A 600:120 potential transformer would provide an output voltage of 120V when

a voltage of 600V is impressed across the primary winding. The potential transformer here

has a voltage ratio of 230:24 i.e., when the input voltage is the single phase voltage 230V,

the output is 24V.

Fig20: Potential transformer used as an Instrument Transformer

The potential transformer here is being used for voltage sensing in the line. They are

designed to present negligible load to the supply being measured and have an accurate

voltage ratio and phase relationship to enable accurate secondary connected metering. The

potential transformer is used to supply a voltage of about 12V to the Zero Crossing

Detectors for zero crossing detection. The outputs of the potential transformer are taken

from one of the peripheral terminals and the central terminal as only a voltage of about

12V is sufficient for the operation of Zero crossing detector circuit.

4.6 Zero crossing detector:

A zero crossing is a point where the sign of a mathematical function changes (e.g.

from positive to negative), represented by the crossing of the axis (zero value) in the graph

of the function. In alternating current the zero-crossing is the instantaneous point at which

there is no voltage present. Ina a sine wave this condition normally occurs twice in a cycle.


39 | P a g e

signal crosses zero volts. If input voltage is a low frequency signal, then output voltage

will be less quick to switch from one saturation point to another.

Fig21: Circuit Diagram of ZCD detector

The 230 V, 50 Hz is stepped down using voltage transformer and a current transformer

is used to extract the waveform of current. The output of the voltage transformer is

proportional to the voltage across the load and the output of current transformer is

proportional to the current through the load. These waveforms are fed to voltage

comparators constructed using LM358 op-amp. Since it is a zero crossing detector, its

output changes during each zero crossing of the current and voltage waveforms. The

outputs are then fed to the summer consisting of the X-OR gate.

Fig22: Simulation in Multisim Software

The IC operates on a 12V d.c supply applied to pin 8 and pin 4 is connected to the

ground. The current transformer output is fed to pin no. 2 and 3 where pin no. 3 is grounded.

The digital output comprising of a square wave is obtained from pin no. 1. As the input

N40 N40

U

LM3

16

IRON_CORE_XFO1


40 | P a g e

sinusoidal signal crosses over to either side of the zero line, the ZCD circuit toggles its

output from 0 (i.e., 0V) to 1 (i.e., 5V), thereby generating a square wave at its output as is

evident from the waveform given in the figure below.

Fig23: ZCD Output waveform on Multisim

4.7 Summer/Adder (X-OR) gate:

1 General description:

The ‘HC86 and ‘HCT86 contain four independent EXCLUSIVE OR gates in one

package. They provide the system designer with a means for implementation of the

EXCLUSIVE OR function. Logic gates utilize silicon gate CMOS technology to achieve

operating speeds similar to LSTTL gates with the low power consumption of standard

CMOS integrated circuits. All devices have the ability to drive STTL loads. The HCT logic

family is functionally pin compatible with the standard LS logic family.

Features:

• Typical Propagation Delay: 9ns at VCC = 5V,

• CL = 15pF, TA = 25oC

• Fan-out (Over Temperature Range)

• Standard Outputs . . . . . . . . . . . . . . . 10 LSTTL Loads

• Bus Driver Outputs . . . . . . . . . . . . . 15 LSTTL Loads

• Wide Operating Temperature Range . . . -55oC to 125oC

• Balanced Propagation Delay and Transition Times


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• Significant Power Reduction Compared to LSTTL.

Fig26: Current and Voltage inputs to the X-OR gate and the output on purely Resistive load

Fig27: Current and Voltage inputs to the X-OR gate and the output on Resistive and Inductive Load.


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Inputs Output

Na Nb Ny

L L L

L H H

H L H

H H L

Note: H = High level voltage (5V) L = Low level voltage (0V)

Table27: Truth Table for X-OR operation.

The X-OR gate, 7486 IC DIP package is used to add the two square wave signal outputs

of the zero crossing detector circuits of the line current and line voltage. The output of the

X-OR gate is the time lag between the zero crossing of the voltage signal and current signal

as illustrated below:

Fig 28: ZCD outputs of current and voltage as inputs to the X-OR.


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Fig 29: X-OR output of line voltage and current

The output of the zero crossing detector of the line voltage is given to pin no. 4 i.e., 2A

and the output of the zero crossing detector of the line current is given to pin no. 5 i.e., 2B.

The output from the X-OR gate is taken from the pin no 6 i.e., 2Y and is then applied to an

Analog pin, pin no. 3 of the Arduino microcontroller.

4.8 Relay Module:

The relay module comprises of eight electro-magnetic relays which are controlled by

the outputs on the digital pins of the Arduino microcontroller. The relays are used to switch

on the required number of capacitors as required for power factor correction. The relays

are normally in the Normally Open‖ (NO) state and the contacts are closed only when the

logic on any of the digital pins is high. As the logic on a pin goes high, the Normally Open‖

contacts of the relay are now closed and the corresponding capacitor in connected in

parallel with the load.

The relay module is interfaced with the digital pins of the Arduino microcontroller using

a parallel port and bus. The relay driver is supplied with a voltage of 12V from the power


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supply. Each of the relays has an LED connected across its terminals to indicate that the

relay has been switched on and is functional.

Fig 30: Relay Module

Fig 31: Relay drive by Arduino.


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4.8.1 Relay Driver:

The ULN2001A, ULN2002A, ULN2003A and ULN2004A are high voltage,

high current Darlington arrays each containing seven open collector Darlington pairs

with common emitters. Each channel rated at 500mA and can withstand peak

currents of 600mA. Suppression diodes are included for inductive load driving and

the inputs are pinned opposite the outputs to simplify board layout. The four versions

interface to all common logic families.

These versatile devices are useful for driving a wide range of loads including

solenoids, relays, DC motors, LED displays filament lamps, thermal print heads and

high power buffers. The ULN2001A/2002A/2003A and 2004A are supplied in 16

pin plastic DIP packages with a copper lead frame to reduce thermal resistance. They

are available also in small outline package (SO-16) as

ULN2001D/2002D/2003D/2004D.

Fig 32: Pin diagram of the Relay driver ULN2003A.


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4.8.2 Relay Operation:

The relays used in the control circuit are high-quality Single Pole-Double

Throw (SPDT), sealed 12V Sugar Cube Relays. These relays operate by virtue

of an electromagnetic field generated in a solenoid as current is made to flow in

its winding. The control circuit of the relay is usually low power (here, a 12V

supply is used) and the controlled circuit is a power circuit with voltage around

230V a.c.

The relays are individually driven by the relay driver through a 12V power

supply. Initially the relay contacts are in the Normally Open state. When a relay

operates, the electromagnetic field forces the solenoid to move up and thus the

contacts of the external power circuit are made. As the contact is made, the

associated capacitor is connected in parallel with the load and across the line.

The relay coil is rated upto 14V, with a minimum switching voltage of 10V. The

contacts of the relay are rated upto 7A @ 270C AC and 7A @ 24V DC.

Fig 33: Sugar Cube relays

Fig 34: Schematic Diagram of the Sugar Cube relay


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4.9 Capacitor Bank:

A capacitor bank is a grouping of several identical or non-identical capacitors interconnected in

parallel or in series with one another. These groups of capacitors are typically used to correct or

counteract undesirable characteristics such as power factor lag or phase shifts inherent in alternating

current electrical power supplies. Capacitor banks may also be used in direct current power supplies

to increase stored energy and improve the ripple current capacity of the power supply. The capacitor

bank consists of a group of eight (8) a.c. capacitors, all rated at 230V, 50 Hz i.e., the supply voltage

and frequency. The value of capacitors is different and it consists of four capacitors of 2.5µfarad,

two capacitors of 4.5 farad and two remaining capacitors are rated at 10µfarads each. All the

capacitors are connected in parallel to one another and the load. The capacitor bank is controlled

by the relay module and is connected across the line. The operation of a relay connects the

associated capacitor across the line in parallel with the load and other capacitor.

Fig 36: Capacitor bank in the circuit along with the control module.

Fig 35: Relay connection On

MATLAB


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Example 4

What value of Capacitance must be connected in parallel with a load drawing 1kW

at 70% lagging power factor from a 208V, 60Hz Source in order to raise the overall

power factor to 91%.

Solution:

You can use either Table method or Simple Calculation method to find the required value

of Capacitance in Farads or kVAR to improve Power factor from 0.71 to 0.97. So I used

table method in this case.

P = 1000W

Actual Power factor = Cosθ1 = 0.71

Desired Power factor = Cosθ2 = 0.97

From Table, Multiplier to improve PF from 0.71 to 0.97 is 0.783

Required Capacitor kVAR to improve P.F from 0.71 to 0.97

Required Capacitor kVAR = kW x Table Multiplier of 0.71 and 0.97

= 1kW x 0.783

=783 VAR (required Capacitance Value in kVAR)

Current in the Capacitor =IC = QC / V

= 783 / 208

= 3.76A

And

XC = V / IC

= 208 / 3.76 = 55.25Ω

C = 1/ (2 π f XC)

C = 1 (2 π x 60 x 55.25)

C = 48 μF (required Capacitance Value in Farads)


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Fig.37: Table for PF multiplier

4.10 Microcontroller:

4.10.1 Introduction:

The Microcontroller or the processing module is an interfacing and controlling

module, that interfaces the various peripherals and other modules used in the circuit.

It integrates the function of various modules such as the Zero Crossing Detector

(ZCD), X-OR gate, Relay driver (ULN2003A) etc.


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4.10.2 Overview:

The Arduino Uno is a microcontroller board based on the ATmega328. It has 14

digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs,

a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and

a reset button. It contains everything needed to support the microcontroller; simply

connect it to a computer with a USB cable or power it with a AC-to-DC adapter or

battery to get started.

The Uno differs from all preceding boards in that it does not use the FTDI USB-

to-serial driver chip. Instead, it features the Atmega16U2 (Atmega8U2 up to version

R2) programmed as a USB-to-serial converter.

Revision 2 of Uno board has a resistor pulling the 8U2 HWB line to ground, making

it easier to pit into DFU mode.

Revision 3 of the Uno board has the following features:

• Pinout: added SDA and SCL pins that are near to the AREF pin and two other

new pins placed near to the RESET pin, the IOREF that allow the shields to adapt

Fig 38: Arduino UNO Board


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to the voltage provided from the board. In future, shields will be compatible with

both the board that uses the AVR, which operates with 5V and with the Arduino

Due that operates with 3.3V. The second one is a not connected pin that is

reserved for future purposes.

• Stronger RESET circuit.

• ATmega 16U2 replace the 8U2.

"Uno" means one in Italian and is named to mark the upcoming release of

Arduino 1.0. The Uno and version 1.0 will be the reference versions of Arduino,

moving forward. The Uno is the latest in a series of USB Arduino boards, and the

reference model for the Arduino platform; for a comparison with previous versions,

see the index of Arduino boards.

Fig 39: Arduino Uno Pin Description.

4.10.3 Summary:

Microcontroller ATmega328

Operating Voltage 5V

Input Voltage (recommended) 7-12V

Input Voltage (limits) 6-20V

Digital I/O Pins 14 (of which 6 provide PWM output)

Analog Input Pins 6

http://arduino.cc/en/Main/Boards




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DC Current per I/O Pin 40 mA

DC Current for 3.3V Pin 50 mA

Flash Memory 32 KB (ATmega328) of which 0.5 KB

used by boot loader

SRAM 2 KB (ATmega328)

EEPROM 1 KB (ATmega328)

Clock Speed 16 MHz

4.10.4 Schematic & Reference Design:

Fig 40: Schematic for Arduino UNO

4.10.5 Input and Output:

Each of the 14 digital pins on the Uno can be used as an input or output using

pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each

pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor

(disconnected by default) of 20-50 kOhms. In addition, some pins have specialized

functions:

http://arduino.cc/en/Reference/PinMode




http://arduino.cc/en/Reference/DigitalWrite

http://arduino.cc/en/Reference/DigitalWrite

http://arduino.cc/en/Reference/DigitalRead




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Fig 41: ATmega328 IC

• Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial

data. These pins are connected to the corresponding pins of the ATmega8U2

USB-to-TTL Serial chip.

• External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt

on a low value, a rising or falling edge, or a change in value. See the

attachInterrupt() function for details.

• PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the analogWrite()

function.

• SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI

communication using the SPI library.

• LED: 13. There is a built-in LED connected to digital pin 13. When the pin is

HIGH value, the LED is on, when the pin is LOW, it's off.

The Uno has 6 analog inputs, labeled A0 through A5, each of which provide 10

bits of resolution (i.e. 1024 different values). By default they measure from

ground to 5 volts, though is it possible to change the upper end of their range

using the AREF pin and the analog Reference() function.

Additionally, some pins have specialized functionality:

TWI: A4 or SDA pin and A5 or SCL pin. Support TWI communication using

the Wire library.

There are a couple of other pins on the board:

• AREF: Reference voltage for the analog inputs. Used with analog Reference().

• Reset: Bring this line LOW to reset the microcontroller. Typically used to add a

reset button to shields which block the one on the board.

http://arduino.cc/en/Reference/AttachInterrupt




http://arduino.cc/en/Reference/AnalogWrite




http://arduino.cc/en/Reference/SPI



http://arduino.cc/en/Reference/AnalogReference


http://arduino.cc/en/Reference/Wire







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4.10.6 Communication:

The Arduino Uno has a number of facilities for communicating with a computer,

another Arduino, or other microcontrollers. The ATmega328 provides UART TTL

(5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An

ATmega16U2 on the board channels this serial communication over USB and

appears as a virtual com port to software on the computer. The '16U2 firmware uses

the standard USB COM drivers, and no external driver is needed. The Arduino

software includes a serial monitor which allows simple textual data to be sent to and

from the Arduino board. The RX and TX LEDs on the board will flash when data is

being transmitted via the USB-to-serial chip and USB connection to the computer

(but not for serial communication on pins 0 and 1).

A Software Serial library allows for serial communication on any of the Uno's

digital pins. The ATmega328 also supports I2C (TWI) and SPI communication. The

Arduino software includes a Wire library to simplify use of the I2C bus; see the

documentation for details. For SPI communication, use the SPI library.

4.10.7 Programming:

The Arduino Uno can be programmed with the Arduino software (download).

Select "Arduino Uno from the Tools > Board menu (according to the microcontroller

on your board). For details, see the reference and tutorials.

The ATmega328 on the Arduino Uno comes pre burned with a bootloader that

allows you to upload new code to it without the use of an external hardware

programmer. It communicates using the original STK500 protocol (reference, C

header files).

You can also bypass the bootloader and program the microcontroller through the

ICSP (In-Circuit Serial Programming) header; see these instructions for details.

The ATmega16U2 (or 8U2 in the rev1 and rev2 boards) firmware source code

is available. The ATmega16U2/8U2 is loaded with a DFU bootloader, which can be

activated by:

• On Rev1 boards: connecting the solder jumper on the back of the board (near the

map of Italy) and then resetting the 8U2.

http://www.arduino.cc/en/Reference/SoftwareSerial











http://arduino.cc/en/Main/Software

http://arduino.cc/en/Reference/HomePage



http://arduino.cc/en/Tutorial/HomePage



http://arduino.cc/en/Tutorial/Bootloader



http://www.atmel.com/dyn/resources/prod_documents/doc2525.pdf

http://www.atmel.com/dyn/resources/prod_documents/doc2525.pdf

http://www.atmel.com/dyn/resources/prod_documents/avr061.zip




http://arduino.cc/en/Hacking/Programmer




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• On Rev2 or later boards: there is a resistor that pulling the 8U2/16U2 HWB line

to ground, making it easier to put into DFU mode.

4.10.8 Automatic (Software) Reset:

Rather than requiring a physical press of the reset button before an upload, the

Arduino Uno is designed in a way that allows it to be reset by software running on a

connected computer. One of the hardware flow control lines (DTR) of

theATmega8U2/16U2 is connected to the reset line of the ATmega328 via a 100

µfarad capacitor. When this line is asserted (taken low), the reset line drops long

enough to reset the chip. The Arduino software uses this capability to allow you to

upload code by simply pressing the upload button in the Arduino environment. This

means that the bootloader can have a shorter timeout, as the lowering of DTR can be

well-coordinated with the start of the upload.

This setup has other implications. When the Uno is connected to either a computer

running Mac OS X or Linux, it resets each time a connection is made to it from

software (via USB). For the following half-second or so, the bootloader is running

on the Uno. While it is programmed to ignore malformed data (i.e. anything besides

an upload of new code), it will intercept the first few bytes of data sent to the board

after a connection is opened. If a sketch running on the board receives one-time

configuration or other data when it first starts, make sure that the software with which

it communicates waits a second after opening the connection and before sending this

data. The Uno contains a trace that can be cut to disable the auto-reset. The pads on

either side of the trace can be soldered together to re-enable it. It's labeled "RESET-

EN". You may also be able to disable the auto-reset by connecting a 110 ohm resistor

from 5V to the reset line; see this forum thread for details.

4.10.9 USB Overcurrent Protection:

The Arduino Uno has a resettable poly fuse that protects your computer's USB

ports from shorts and overcurrent. Although most computers provide their own

internal protection, the fuse provides an extra layer of protection. If more than 500

mA is applied to the USB port, the fuse will automatically break the connection until

the short or overload is removed.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1213719666/all





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4.10.10 Physical Characteristics:

The maximum length and width of the Uno PCB are 2.7 and 2.1 inches

respectively, with the USB connector and power jack extending beyond the former

dimension. Four screw holes allow the board to be attached to a surface or case. Note

that the distance between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple

of the 100 mil spacing of the other pins.


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Chapter 5

Software


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5.1 Software Development Environment:

The Arduino is a single-board microcontroller, intended to make the application of

interactive objects or environments more accessible. The hardware consists of an open-

source hardware board designed around an 8-bit Atmel AVR microcontroller or a 32-bit

Atmel ARM. Current models feature a USB interface, 6 analog input pins, as well as 14

digital I/O pins which allow the user to attach various extension boards. Introduced in 2005,

at the Interaction Design Institute Ivrea, in Ivrea, Italy, it was designed to give students an

inexpensive and easy way to program interactive objects. It comes with a simple Integrated

Development Environment (IDE) that runs on regular personal computers and allows

writing programs for Arduino using a combination of simple Java and C or C++.

The Arduino Integrated Development Environment (IDE) is a cross platform

application written in Java, and is derived from the IDE for the processing programming

language and the wiring projects. It is designed to introduce programming to artists and

other newcomers unfamiliar with software development. It includes a code editor with

features such as Syntax highlighting, Brace matching and Automatic Indentation, and is

also capable of compiling and uploading programs to the board with a single click. A

program or code written for the Arduino is called a Sketch‖.

The Arduino IDE also comes with a software library called ―Wiring‖ from the original

Wiring Project, which makes many common input/output operations much easier. Users

need only define two functions to make a runnable cyclic executive program:

• setup(): a function run once at the start of a program that can initialize settings.

• loop(): a function called repeatedly until the

• board powers off .

The previous code will not be seen by a standard C++ compiler as a valid program, so

when the user clicks the “Upload to I/O Board” button in the IDE, a copy of the code is

written to a temporary file with an extra include header at the top and a very simple main()

function at the bottom to make it a valid C++ program. The Arduino IDE uses the GNU


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tool chain and AVR Libc to compile programs and uses avrdude to upload programs to the

board As the Arduino platform uses Atmel microcontrollers, Atmel‘s development

environment AVR Studio or the newer Atmel Studio, may also be used to develop software

for the Arduino.

Fig 42: The main programming window of the Arduino IDE.


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5.2 pulseIn():

• Description:

The function reads a pulse (either HIGH or LOW) on a pin. For example, if value is

HIGH, pulseIn() waits for the pin to go HIGH, starts timing, then waits for the pin to

go LOW and stops timing. Returns the length of the pulse in microseconds. Gives up

and returns 0if no pulse starts within a specified time out. The timing of this function

has been determined empirically and will probably show errors in longer pulses.

Works on pulses from 10 microseconds to 3 minutes in length.

• Syntax:

pulseIn(pin, value)

• Parameters:

pin: the number of the pin on which you want to read the pulse. (int)value: type of

pulse to read either HIGH or LOW. (int) timeout (optional): the number of

microseconds to wait for the pulse to start; default is one second (unsigned long),

return spin the number of the pin on which you want to read the pulse. (int) value: type

of pulse to read: either HIGH or LOW. (int) timeout (optional): the number of

microseconds to wait for the pulse to start; default is one second (unsigned long),

returns the length of the pulse (in microseconds) or 0 if no pulse started before

tinmeout (unsigned long).

5.3 Program:

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 6, 5, 4, 3);// constants won't change. They're used here to

// set pin numbers:

const int buttonPin = 2; // the number of the pushbutton pin

const int ledPin = 8; // the number of the LED pin






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// variables will change:

int buttonState = 0; // variable for reading the pushbutton status

void setup()

// initialize the LED pin as an output:

pinMode(ledPin, OUTPUT);

// initialize the push button pin as an input:

pinMode(buttonPin, INPUT);

lcd.begin(16, 2);

lcd.print(" A.P.F.C.A.D");

delay(10000);

void loop()

// read the state of the pushbutton value:

buttonState = digitalRead(buttonPin);

// check if the pushbutton is pressed.

// if it is, the buttonState is HIGH:

if (buttonState == HIGH)

lcd.clear(); // Start with a blank screen

lcd.setCursor(0, 1); // Set the cursor to the second line

lcd.print("Power Factor=1");

lcd.setCursor(0, 0); // Set the cursor to the beginning

lcd.print("Resistive load");

delay(5000);

// turn LED on:

digitalWrite(ledPin, LOW);

else


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lcd.print("Before PFC=0.5");


lcd.print("Inductive Load");

delay(5000);

// turn LED off:

digitalWrite(ledPin, HIGH);



lcd.print("After PFC=1");


lcd.print("Inductive Load");

// delay(5000);


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Chapter 6

Hardware


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6.1 Hardwaer:

PFC (power factor correction; also known as power factor controller) is a feature

included in some computer and other power supply boxes that reduces the amount

of reactive power generated by a computer. Reactive power operates at right angles to true

power and energizes the magnetic field. Reactive power has no real value for an electronic

device, but electric companies charge for both true and reactive power resulting in

unnecessary charges. PFC is a required feature for power supplies shipped to Europe.

In power factor correction, the power factor (represented as "k") is the ratio of true

power (kwatts) divided by reactive power (kvar). The power factor value is between 0.0

and 1.00. If the power factor is above 0.8, the device is using power efficiently. A standard

power supply has a power factor of 0.70-0.75, and a power supply with PFC has a power

factor of 0.95-0.99.

PFC is not used solely for computer power supplies. In other industries, PFC equipment

is used to reduce the reactive power produced by fluorescent and high bay lighting, arc

furnaces, induction welders, and equipment that uses electrical motors.

Fig43: APFC HARDWARE

http://searchcio-midmarket.techtarget.com/definition/reactive-power

http://whatis.techtarget.com/definition/true-power

http://whatis.techtarget.com/definition/true-power

http://searchcio-midmarket.techtarget.com/definition/magnetic-field


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6.1.1 Schematics:

A. Power Supply Section:

• This is section basically use for supplying to sensing section, Arduino

Board Display and Relay Section.

• Basically in this section include Center tap tx (15-0-15), Diode (1N4007),

Ele. Capacitor, Regulator IC(LM7812,7912)

•

Fig44: Schematic Power Supply Section.


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B. Sensing circuit:

• This is section basically sense current and voltage across and series to the

load.Then using integrator circuit convert square wave to pure dc.then this

signal pass to the comparator circuit comparator compare it and according

to load get output high or low to the scr. This signal pass to the controlling

section.

• This section basically use Current tx, Potential tx, LM741, Resistor,

Capacitor and SCR (BT151).

Fig45: Schematic for Sensing Circuit.


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C. Controlling Section:

• This is section sense the voltage from sensing ckt and show particular load

on the display with PF. If PF is Low then switch the capacitor and maintain

PF unit.

• In this section use ATmega328, 16X2 LCD, ULN2003, Crystal, Relay,

Capacitor (4µF/230VAC).

Fig46: Schematic For Controlling and display section.


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6.2 Result:

A. Inductive Load:

Fig.47: Before PFC

Fig.48: After P.F.C.


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B. Resistive load:

Fig.49: Resistive Load


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Chapter 7

Project Costing


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7 Project Costing:

Sr.

No.

Component Specification Quanti

ty

Rate

(Rs/unit)

Total

cost

1 Arduino UNO - 1 560 560

2 Center tap transformer 18-0-18

250mA

1 180 180

3 Step down transformer 18 Volt 2 150 300

4 16x2 LCD display - 1 155 155

5 Current transformer 20A/20ma 1 240 240

6 Euro Style connector - 2 100 200

7 Isolation transformer 230/230V,2Amp 1 600 600

8

Choke ballast - 1 150 150

9 AC capacitor 2 µF,230VAC 1 250 250

10 Sugar cube Relay 12VDC 1 45 45

11 General purpose PCB Large 2 50 100

12 ON OFF switch 2 amp 2 25 50

13 BT151 SCR 1 30 30

14 LM7812 Regulator 2 20 40

15 LM7912 Regulator 1 20 20

16 LM741 with base Opamp 4 20 80

17 ULN2300 Driver IC 1 25 252

18 Preset 10k 6 6 36

19 Led 3mm 1 2 2

20 Ele. Cap. 460 µF/63V 3 10 30

1000 µF/63V 2 10 20

100 µF/63V 3 3 9

21 1N4007 - 15 2 30

22 Incandescent Lamp 230VAC/100W 1 20 20

23 Lamp Holder 1 25 25

24 Resistor 1K 1/4 W 10 1 10

25 Green connector 2 pin 7 10 70

3 pin 2 12 24

26 Berg strip M/F 2 30 60

27 Spacer plastic 5mm 100gm 50 50

28 Striker tie - 24 3 72

29 DC power male jack 5mm 1 10 10

30 Teflon wire - 1 Role 90 90


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31 Multi stand wire 2𝑚𝑚2 3 meter 15 45

32 Screw nut 3mm 30 3 90

33 Soldering wire - 1 Role 80 80

34 2 pin top 2 amp 1 10 10

35 Ply board 5mm 1 60 60

Total 3072 4095


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Chapter 8

Conclusion


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8.1 Conclusion:

The Automatic Power Factor Detection and Correction provides an efficient

technique to improve the power factor of a power system by an economical way. Static

capacitors are invariably used for power factor improvement in factories or distribution

line. However, this system makes use of capacitors only when power factor is low

otherwise they are cut off from line. Thus, it not only improves the power factor but also

increases the life time of static capacitors. The power factor of any distribution line can

also be improved easily by low cost small rating capacitor. This system with static capacitor

can improve the power factor of any distribution line from load side. As, if this static

capacitor will apply in the high voltage transmission line then its rating will be

unexpectedly large which will be uneconomical & inefficient. So a variable speed

synchronous condenser can be used in any high voltage transmission line to improve power

factor & the speed of synchronous condenser can be controlled by microcontroller.

8.2 References:

• P. N. Enjeti and R Martinez, ―A high performance single phase rectifier with input

power factor correction,‖ IEEE Trans. Power Electron.vol.11, No. 2, Mar.2003.pp

311-317

• J.G. Cho, J.W. Won, H.S. Lee, ―Reduced conduction loss zero-voltage-transition

power factor correction converter with low cost,‖ IEEE Trans. Industrial Electron.

vol.45, no 3, Jun. 2000, pp395-400

• V.K Mehta and Rohit Mehta, ―Principles of power system‖, S. Chand & Company

Ltd, Ramnagar, New delhi-110055, 4th Edition, Chapter 6.

• Dr. Kurt Schipman and Dr. Francois Delince, ―The importance of good power

quality‖, ABB power quality Belgium.

• Robert. F. Coughlin, Frederick. F. Driscoll, ―Operational amplifiers and linear

integrated circuits‖, 6thEdition, chapter 4.

• International Journal of Engineering and Innovative Technology (IJEIT) Volume 3,

Issue 4, October 2013 272 Power Factor Correction Using PIC Microcontroller

• www.arduino.cc

http://www.arduino.cc/

http://www.arduino.cc/


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• Design and Implementation of Microcontroller-Based Controlling of Power Factor

Using Capacitor Banks with Load Monitoring, Global Journal of Researches in

Engineering Electrical and Electronics Engineering, Volume 13, Issue 2, Version 1.0

Year 2013 Type: Double Blind Peer Reviewed International Research Journal

Publisher:

Global Journals Inc. (USA) Online ISSN: 2249-4596 & Print ISSN: 0975-5861

• Electric power industry reconstructing in India, Present scenario and future

prospects, S.N. Singh, senior member, IEEE and S.C. Srivastava, Senior Member,

IEEE.


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ACKNOWLEDGEMENT

I would like to take the opportunity to express my heartfelt gratitude to the people

whose help and co-ordination has made this project a success. I thank Prof.

SHRINIVAS for knowledge, guidance and co-operation in the process of making this

project.

I owe project success to my guide and convey my thanks to him. I would like to express

my heartfelt to all the teachers and staff members of Electrical Engineering department

of ARMIET for their full support. I would like to thank my principal for conductive

environment in the institution.

I am grateful to the library staff of ARMIET for the numerous books, magazines made

available for handy reference and use of internet facility.

Lastly, I am also indebted to all those who have indirectly contributed in making this

project successful.

NITESH A. KAMBLI

DURGESH G. KADU

RANDHIR S. YADAV


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