Automatic Power Factor Corrector Using Arduino report

AUTOMATIC POWER FACTOR DETECTOR AND
CORRECTOR USING ARDUINO UNO
The Project Report submitted in partial fulfilment of the requirements of the
DEGREE OF BACHELOR OF ENGINEERING
By
Mr. NITESH A .KAMBLI ARMIET/BE/EE/NA08
Mr. DURGESH G. KADU ARMIET/BE/EE/KD220
Mr. RANDHIR S. YADAV ARMIET/BE/EE/YR253
Under the Guidance of
ALAMURI RATNAMALA INSTITUTE OF ENGINEERING AND
TECHNOLOGY
Affiliated to
UNIVERSITY OF MUMBAI
Department of Electrical Engineering
Academic Year – 2016-2017
PROF.P.SRINIVASA RAO

CERTIFICATE
This dissertation report entitled “Automatic Power Factor Detector and
Corrector using Arduino UNO” by Mr. Nitesh A. Kambli is approved for the
degree of Bachelor of Engineering in Electrical Engineering for academic year 2016
- 2017.
Examiners
____________________________
Supervisor
____________________________
Prof. SRINIVASA.RAO
______________________________ ____________________________
Head of the Department Principal
Date:
Place:

Declaration
I declare that this written submission represents my ideas in my own words and where
others ideas or words have been included, I have adequately cited and referenced the original
sources. I also declare that I have adhered to all principles of academic honesty and integrity
and have not misrepresented or fabricated or classified any idea, data, fact and source in my
submission. I understand that any violation of the above will be cause for disciplinary action by
the Institute and can also evoke penal action from the sources which have thus not been
properly cited or from whom proper permission has not been taken when needed.
Mr. Nitesh A. Kambli
Date:

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. Srinivasa Rao
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.
Mr. Nitesh A.Kambli

ABSTRACT
In recent years, the power quality of the ac system has become great concern due
to the rapidly increased numbers of electronic equipment, power electronics and high
voltage power system. Most of the commercial and industrial installation in the country
has large electrical loads which are severally inductive in nature causing lagging power
factor which gives heavy penalties to consumer by electricity board. This situation is taken
care by PFC. Power factor correction is the capacity of absorbing the reactive power
produced by a load. In case of fixed loads, this can be done manually by switching of
capacitors, however in case of rapidly varying and scattered loads it becomes difficult to
maintain a high power factor by manually switching on/off the capacitors in proportion to
variation of load within an installation. This drawback is overcome by using an APFC
panel. In this paper measuring of power factor from load is done by using Atmega328
microcontroller and trigger required capacitors in order to compensate reactive power and
bring power factor near to unity.
KEYWORDS: Automatic power factor correction, embedded technology, Efficiency of the
system increases, Improve the power system performance.

Abbreviations
A - Ampere
V - Volt
P - Power
Q - Reactive Power
S - Apparent Power
PCB - Printed Circuit Board
PIC - Peripheral Interface Controller
IEEE - Institution of Electrical and Electronic Engineering
IC - Integrated Circuit
SPI - Serial Peripheral Interface
R - Resistor
L - Inductance
C - Capacitor
X - Reactance
Z - Impedance
Kw - Killo-Watt
KVa - killo-volt-ampere
kVAr - killo-volt-ampere-reactive
P.F. - Power Factor
I - Current
CFL - Compact Fluorescent Lamp
Tx - Transformer

LIST OF FIGURES
FIG. NO. TITLE NAME PAGE NO.
1 Power Triangle 5
2 Pure Resistive Load Circuit 12
3 The waveform for pure resistive load 13
4 Pure Capacitive load circuit 13
5 The waveform for pure Capacitive load 14
6 Pure Inductive load circuit 14
7 The wave form for pure inductive load 15
8 Block of PFC using ATMEGA 328 20
9 Block diagram of APFC 22
10 Voltage Transformer/Potential transformer 25
11 Carbon Film Resistor 26
12 Light Emitting Diodes (LED) 27
13 Schematic of an LED 28
14 Electrolytic Capacitors 29
15 Ceramic Capacitors 31
16 Pin out diagram of an LM7805 regulator 33
19 Secondary Winding of a Ring CT 37
20 Potential transformer 38
21 Circuit Diagram of ZCD detector 39
22 Simulation in Multisim Software 40
23 ZCD Output waveform on Multisim 40
26
Current and Voltage inputs to the X-OR
gate 41
27 Truth Table for X-OR operation 42
28 ZCD outputs of as input to the X-OR 42
29 X-OR output of line voltage and current 43
30 Relay Module 44
31 Relay drive by Arduino 44

FIG. NO. TITLE NAME PAGE NO.
32 ULN2003A 45
33 Sugar Cube relays 46
34 Schematic Diagram of the Sugar Cube relay 46
35 Relay connection On MATLAB 47
36 Capacitor bank with the control module 47
37 Table for PF multiplier 49
38 Arduino UNO Board 50
39 Arduino Uno Pin Description 51
40 Schematic for Arduino UNO 52
41 ATmega328 IC 53
42
The main programming window of the
Aurduino 59
43 APFC Hardware 64
44 Schematic Power Supply Section 65
45 Schematic for Sensing Circuit 66
46
Schematic For Controlling and display
section 67
47 Before PFC correction result 68
48 After PFC correction result 68
49 Resistive load result 69

CONTENT
SR NO TOPIC NAME PAGE NO
1 Introduction 1
2 Review of literature 4
2.1 Power factor 5
2.2 Power factor correction 6
2.2.1 Passive PFC 7
2.2.2 Active PFC 7
2.2.3 Advantage of power factor correction 8
2.3 Disadvantage of low power factor 8
2.3.1 Advantage of improved power factor 9
2.4 Power factor of electrical loads 9
2.5 Capacitor 10
2.5.1 Power factor capacitors 11
2.5.2 Uses of Automatic power factor capacitors 11
2.6
P.F. in Resistor, Inductance and
capacitance circuit
12
2.7 Power factor harmonics 15
2.7.1 Potential source of harmonics 16
2.7.2 Effect of harmonics on main supplies 16
2.7.3 Purpose of harmonic current limitation 17
2.7.4 Fixed versus Automatic capacitors 17
3 Proposed system 19
4 System Design 21
4.1 Principle 22
4.2 Circuit Description 23
4.3 Power supply 24
4.3.1 Components 24
4.3.2 Circuit diagram 34
4.3.2 Explanation 35
4.4 Current Transformer 36
4.5 Potential transformer 37
4.6 Zero crossing detector 38
4.7 Summer/Adder(X-OR) gate 40
4.8 Relay module 43
4.8.1 Relay driver 45
4.8.2 Relay operation 46
4.9 Capacitor Bank 47

SR NO TOPIC NAME PAGE NO
4.1O Microcontroller 49
4.10.1 Introduction 49
4.10.2 Overview 50
4.10.3 Summary 51
4.10.4 schematic & Reference design 52
4.10.5 Input & Output 52
4.10.6 Communication 54
4.10.7 Programming 54
4.10.8 Automatic (software) Reset 55
4.10.9 USB overcurrent protection 55
4.10.10 Physical characteristics 56
5 Software 57
5.1 Software development environment 58
5.2 Pulse In 60
5.3 Program 60
6 Hardware 63
6.1 Hardware 64
6.1.1 Schematics 65
6.2 Result 68
7 Project Costing 70
8 Conclusion 73
8.1 Conclusion 74
8.2 Reference 74

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

7 | P a g e
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

8 | P a g e
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.

9 | P a g e
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.

11 | P a g e
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.

16 | P a g e
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

20 | P a g e
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

24 | P a g e
....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

25 | P a g e
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

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

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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

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.

32 | P a g e
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.

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

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.

35 | P a g e
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 (1000̊F) 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

36 | P a g e
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.

37 | P a g e
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_XFO
1

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

41 | P a g e
• 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.

42 | P a g e
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.

43 | P a g e
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

44 | P a g e
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.

45 | P a g e
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

48 | P a g e
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

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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:

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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.

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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.

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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.

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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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5.2pulseIn():
• 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

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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

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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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Automatic Power Factor Corrector Using Arduino report

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