automatic power factor correction report

PROJECT’17 Automatic Power Factor Correction
1
DEPARTMENT OF ELECTRICAL AND ELECTRONICS, SCET
Chapter 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.
Power factor is defined as the ratio of real power to apparent
power. This definition is often mathematically represented as KW/KVA, where the
numerator is the active (real) power and the denominator is the (active + reactive) or
apparent power. It is a measure of how effectively the current is being converted into
useful work output. A load with a power factor of 1.0 result in the most efficient
loading of the supply and a load with a power factor of 0.5 will result in much higher
losses in the supply system. A poor power factor can be the result of either a
significant phase difference between the voltage and current at the load terminals, or it
can be due to a high harmonic content or distorted/discontinuous current waveform.
Poor load current phase angle is generally the result of an inductive load such as an
induction motor, power transformer, lighting ballasts, welder or induction furnace. A
distorted current waveform can be the result of a rectifier, variable speed drive,
switched mode power supply, discharge lighting or other electronic load.
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

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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 correction.

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Chapter 2
LITERATURE SURVEY
Pavg = VIcosφ
Where, φ is the phase angle between the voltage and current. The term cosφ is called
the power factor. Power factor is the ration between the KW and the KVA drawn by
an electrical load where the KW is the actual load power and the KVA is the apparent
load power. It is a measure of how effectively the current is being converted into
useful work output and more particularly is a good indicator of the effect of the load
current on the efficiency of the supply system.
Apparent Reactive
Power Power
Active Power
Fig 2.1: Power Triangle
A load with a power factor of 1.0 result in the most efficient loading of the supply and
a load with a power factor of 0.5 will result in much higher losses in the supply
system. A poor power factor can be the result of either a significant phase difference
between the voltage and current at the load terminals or it can be due to a high
harmonic content or distorted/discontinuous current waveform. Poor load current
phase angle is generally the result of an inductive load such as an induction motor,
power transformer, lighting ballasts, welder or induction furnace. A distorted current
waveform can be the result of a rectifier, variable speed drive, switched mode power
supply, discharge lighting or other electronic load.

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2.1. Power Factor Correction
Capacitive Power Factor correction is applied to circuits which include induction
motors as a means of reducing the inductive component of the current and thereby
reduce the losses in the supply. There should be no effect on the operation of the
motor itself. An induction motor draws current from the supply that is made up of
resistive components and inductive components.
 The resistive components are:

i. Load current
ii. Loss current
 The inductive components are

i. Leakage reactance
ii. Magnetizing current
MOTOR
CURRENT
MAGNETIZING
CURRENT
WORK CURRENT
Fig 2.2: Current Triangle
The current due to the leakage reactance is dependent on the total current drawn by
the motor but the magnetizing current is independent of the load on the motor. The
magnetizing current will typically be between 20% and 60% of the rated full load
current of the motor. The magnetizing current is the current that establishes the flux in
the iron and is very necessary if the motor is going to operate. The magnetizing
current does not actually contribute to the actual work output of the motor. It is the
catalyst that allows the motor to work properly. The magnetizing current and the
leakage reactance can be considered passenger components of current that will not
affect the power drawn by the motor, but will contribute to the power dissipated in the
supply and distribution system.

5
Chapter 3
DESIGN AND DEVELOPMENT
3.1BLOCK DIAGRAM
Fig:3.1 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

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3.2 CIRCUIT DIAGRAM
Fig:3.2 Circuit Diagram of APFC
3.3 CIRCUIT DESCRIPTION
The voltage signal obtained is converted into the digital by comparator circuit since
micro controller accepts the digitized format only. This is given to the microcontroller
as one input. Similarly, for current signal, from the current transformer is converted
into voltage signal by rectification. As previously digitized the voltage signal, this
current signal in the form of voltage is also digitized by the comparator circuit.

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These two digitized signals i.e. voltage and currents are sent to the
microcontroller as the inputs. According to the program written microcontroller
calculates the time difference between the zero crossings of these two signals. This
time difference is indirectly proportional to the system power factor. The information
about this power factor and the power loss is displayed on the LCD display. And
according to the range calculated by the microcontroller program; this drives the
relays which switches the shunt capacitors across the load.
While increasing of the inductive load by connecting the other loads like motors to
this circuit results in reduced power factor. This will make the microcontroller to
drive the more number of relays resulting in more shunt capacitors to be connected.
In this project simple method of capacitor requirement calculation used based
on the time delay between the voltage and current to bring the power factor near to
unity. But in real time applications it will not be so. It requires the calculations like
load current magnitude and KVAR requirement etc. Number of capacitors
requirements depends on the load on the particular system. These parameters must be
considered while dealing with the commercial power factor improvement or
compensating products.
3.3.1 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. It is a commonly used term in electronics, mathematics, sound
and image processing. 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.
A zero crossing detector is an important application of op-amp comparator circuit. It
can also be referred to as a sine to square wave converter. Anyone of the inverting or
the non-inverting comparators can be used as a zero crossing detector. The reference
voltage in this case is set to zero. The output voltage waveform shows when and in

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what direction an input 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. And if there is noise in between the two input nodes, the output may fluctuate
between positive and negative saturation voltage ‗Vsat‘. .Here IC LM358 is used as a
zero crossing detector.
Fig:3.3 Zero Crossing Detector
3.3.2 Design of capacitor
Motor input = P, Original P.F = Cosθ1, Final P.F = Cosθ2
Required Capacitor
kVAR = P (Tan θ1 – Tan θ2)
We know that; IC = V/ XC
Whereas XC = 1 / 2 π F C
IC = V / (1 / 2 π F C)
IC = V 2 F C
And,
kVAR = (V x IC) / 1000 … [kVAR = (V x I)/ 1000]
We have already calculated the required Capacity of Capacitor in kVAR, so we can
easily convert it into Farads by using this simple formula
Required Capacity of Capacitor in Farads/Microfarads
C = kVAR / (2 π f V2) in microfarad

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3.4 COMPONENTS AND THEIR DESCRIPTION
3.4.1 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 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.
Fig:3.4.1 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

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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.
3.4.2 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.
Fig:3.4.2 Current Transformer
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.

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3.4.3 Capacitor Bank
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 four ac capacitors, all rated at 400V, 50 Hz i.e., the supply
voltage and frequency. The value of capacitors is different and it consists of four
capacitors of 2.5farad. 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 capacitors.
Fig:3.4.3 Capacitor Bank
3.4.4 LM358
The abbreviation LM358 indicates an integrated circuit to 8 feet, containing
two operational amplifiers at low power. The LM358 is designed for general use
as amplifiers, high-pass filters and low, band pass filters and analogue adders.
One of the particularities of this integrated is to be designed to be able to operate with
a single static power that ranges from a minimum of 3 V to a maximum of 32 V
although typically there settles at levels between 5 V and 15 V. In fact, , while most of

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the integrated circuits containing the operational needs two power supplies, a positive
and a negative, the LM358 can be connected to one positive supply while the negative
supply is replaced by the mass . However, depending on the needs, it can also introduce
the negative power supply by connecting the leg called ground to the appropriate
generator. In feeding regime double the voltage range is ± 1.5 ÷ 16 V.
Fig:3.4.4 LM358 Op-amp
3.4.5 Summer/Adder (X-OR) gate:
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.

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Fig:3.4.5 X-OR gate
3.4.6 Relay Driver:
The ULN2003A 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:
Fig:3.4.6 ULN 2003A
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

14
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:3.4.6 Pinout of uln2003a
3.4.7 RELAY
The relays used in the control circuit are high-quality Single Pole-Double Throw
(SPDT), sealed 6V 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 6V supply is used) and the
controlled circuit is a power circuit with voltage around 230V ac.
The relays are individually driven by the relay driver through a 6V 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 up to 8V,

15
with a minimum switching voltage of 5V. The contacts of the relay are rated up to 7A
@ 270C AC and 7A @ 24V DC.
Fig:3.4.7 relay
3.4.8 LCD (Liquid Crystal Display)
LCD panel consist of two patterned glass panels in which crystal is filled
under vacuum. The thickness of glass varies according to end use. Most of the LCD
modules have glass thickness in the range of 0.70 to 1.1mm.
Normally these liquid crystal molecules are placed between glass plates to form a
spiral stair case to twist the light. These LCD cannot display any information directly.
These act as an interface between electronics and electronics circuit to give a visual
output. The values are displayed in the 2x16 LCD modules after converting suitably.
The liquid crystal display (LCD), as the name suggests is a technology based on the
use of liquid crystal. It is a transparent material but after applying voltage it becomes
opaque. This property is the fundamental operating principle of LCDs.

16
Fig:3.4.8 Liquid Crystal Display
3.4.9 Arduino Uno
Fig:3.4.9 Arduino Uno
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.

17
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.
The Arduino Uno can be powered via the USB connection or with an external power
supply. The power source is selected automatically.
External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or
battery.
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
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 bootloader
SRAM 2 KB (ATmega328)
EEPROM 1 KB (ATmega328)
Clock Speed 16 MHz
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.

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3.5 COST ANALYSIS
RELAY 6V ,240V 5A 4 15
TRANSFORMER
CT
5A 1 35
DIODE IN4007 4 2
Table 3.1 Cost Analysis
COMPONENTS SPECIFICATION QUANTITY AMOUNT
ARDUINO UNO 1 300
74LS86 XOR 1 8
ULN2003A 1 10
LM358 1 30
LCD 2*16 1 120
CAPACITOR
CERAMIC
2.5uf 4 20
RESISTOR 4.7K 4 1
CAPACITOR
CERAMIC
.1uf 3 3
TRANSFORMER
PT
240/9V 1 55
REGULATOR 7805,7812 2 10

19
Chapter 4
RESULT ANALYSIS
4.1 RESULT
The expected outcome of this project is to measuring the power factor value
displaying it in the LCD and to improve power factor using capacitor bank and reduce
current draw by the load using microcontroller and proper algorithm to turn on
capacitor automatically, determine and trigger sufficient switching of capacitor in
order to compensate excessive reactive components, thus bringing power factor near
to unity ,there by improving the efficiency of the system and reducing the electricity
bill.
To verify the performance of the automatic power factor correction using
microcontroller a prototype is developed and tested. Figure shows the system setup
for the automatic power correction using microcontroller. The power supply is of 12-
6V using step down transformer. And it contains a microcontroller, LCD module
which is displaying correct power factor and relays which help to include capacitor
banks to the circuit as per the necessity. Prototype is verified using, an inductive load.
Which initially gives a lagging power factor, which by than gives an improved power
factor close to unity by the proper working of the APFC unit.
Fig:4.1

20
4.2 WORKING MODEL
Fig:4.2 Project Model

21
4.3 PROTEUS SIMULATION
Fig:4.3.1 ZCD Simulation in Multisim Software
Fig:4.3.2 ZCD outputs of current and voltage as inputs to the X-OR

22
Chapter 5
FUTURE SCOPE
The automotive power factor correction using capacitive load banks is very efficient
as it reduces the cost by decreasing the power drawn from the supply. As it operates
automatically, manpower is not required and this Automated Power Factor Correction
using capacitive load banks can be used for the industries purpose in the future
5.1 ADVERSE EFFECT OF OVER CORRECTION
1. Power system becomes unstable
2. Resonant frequency is below the line frequency
3. Current and voltage increases
5.2 ADVANTAGES OF CORRECTED POWER FACTOR
1. Reactive power decreases
2. Avoid poor voltage regulation
3. Overloading is avoided
4. Copper loss decreases
5. Transmission loss decreases
6. Improved voltage control
7. Efficiency of supply system and apparatus increases

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Chapter 6
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.
It can be concluded that power factor correction techniques can be applied to the
industries, power systems and also households to make them stable and due to that the
system becomes stable and efficiency of the system as well as the apparatus increases.
The use of microcontroller reduces the costs. Due to use of microcontroller multiple
parameters can be controlled and the use of extra hard wares such as timer, RAM,
ROM and input output ports reduces.

24
REFERENCE
 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,
 International Journal of Engineering and Innovative Technology (IJEIT) Volume 3,
Issue 4, October 2013 272 Power Factor Correction Using PIC Microcontroller
 www.arduino.cc
 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.

25
ANNEXURES

26
ANNEXURE 1 (ARDUINO PROGRAMMING)
PROGRAM
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++
int x,y,r=0;
float z;//time,angle,pf,radians,pf2 relay
#define echoPin 11 // Echo Pin
#define pf1 9
#define pf2 8
#include <LiquidCrystal.h>
LiquidCrystal lcd(3, 4, 5, 6, 7, 8);//LCD RS-12,En-11,D4-5,D5- 4,D6-
3,D7-2,
void setup()
{
relayinit();
usinit();
lcdstart();
digitalWrite(pf1,LOW);
}
void loop()
{
uscheck();
}
void usinit(void)
{

27
pinMode(echoPin, INPUT);
}
void uscheck(void)
{
x = pulseIn(echoPin,LOW);//reads duartion pulse in Microseconds
y = (x*9)/1000;
z=cos(y*.01745);
if(y>10 && r==0){digitalWrite(pf1,LOW);r=1;}
else if (r==1 && y>10){digitalWrite(pf1,LOW); r=0;}
if(x>500)
{
delay(500);
lcd.setCursor(0, 0);
lcd.print("THE BEST PROJECT");
lcd.setCursor(0, 1);
lcd.print("POWERFACTOR=");
lcd.print(z);
}
}
void relayinit(void)
{
pinMode(pf1,OUTPUT);
pinMode(pf2,OUTPUT);
// pinMode(overvoltrelay,OUTPUT);
}
void lcdstart(void)
{
lcd.begin(16, 2);// set up the LCD's number of columns and rows:
lcd.clear();
}

28
ANNEXURE 2
PCB DESIGN
We are here using the software "gEDA" for designing the PCB. gEDA is a powerful
package for designing single-sided and double sided PCBs.
It provides a comprehensive range of tools including schematic drawing, schematic
capture, component placement, automatic routing, Bill of Materials reporting and
file generation for manufacturing
RELAY MODULE PCB DESIGN
ZERO CROSSING DETECTOR

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ANNEXURE 3 (ATmega 328P)

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31

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ANNEXURE 4 (LM 358)

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ANNEXURE 4 (ULN 2003A)

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