A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller. ACKNOWLEDGEMENT Our Quest for practical knowledge led us in to the esteemed Organization Automatic Electric Co. (Lonavla), which is a hall of fame. If words are considered as symbols of approved and tokens of acknowledges, then let Words play the heralding role of expressing our gratitude. We profusely thank our director Sri. Mr. Pramod Kale and our university Coordinator Dr. D. Shaligram for their encouragement and support through out the project. We extend our heartiest thanks to our respected Project coordinator, Mrs. Preeti Salunkhe, who is always a constant source of inspiration for us and for her motivations in making this project completion. We are very thankful to our beloved guide Ms. Jyutika Nalawade, for her valuable and patient guidance throughout our endeavor. We remember With Regards and respect the assistance and encouragement given by her. We are very much indebted to our beloved parents who have given this opportunity to join in this course and are great source of Department of Electronics science, University of Pune (Sep’06- Feb’07) Page 1 of 80
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
ACKNOWLEDGEMENT
Our Quest for practical knowledge led us in to the esteemed Organization
Automatic Electric Co. (Lonavla), which is a hall of fame. If words are considered as
symbols of approved and tokens of acknowledges, then let Words play the heralding role
of expressing our gratitude. We profusely thank our director Sri. Mr. Pramod Kale and
our university Coordinator Dr. D. Shaligram for their encouragement and support
through out the project.
We extend our heartiest thanks to our respected Project coordinator,
Mrs. Preeti Salunkhe, who is always a constant source of inspiration for us and for her
motivations in making this project completion.
We are very thankful to our beloved guide Ms. Jyutika Nalawade, for her
valuable and patient guidance throughout our endeavor. We remember With Regards and
respect the assistance and encouragement given by her. We are very much indebted to
our beloved parents who have given this opportunity to join in this course and are great
source of encouragement for us. Above all, the GRACE OF GOD of all creations led us
to complete our project successfully.
Department of Electronics science, University of Pune (Sep’06-Feb’07) Page 1 of 63
A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
EXECUTIVE SUMMERY
In our day to day life we use a lot many devices to satisfy our needs or to make
our life comfortable and luxurious. Every device needs a power supply, to work on. And
for the optimum functioning of the device it is necessary that the supply should be
reliable. That is, it should provide a constant voltage.
But this is not possible always. There are many reasons due to which there is a
fluctuation in the supply voltage. This change in the supply voltage may cause the
device to damage or make it work in an undesired way, which no one would desire.
Hence the best alternative is to regulate the supply voltage. This is what we have
tried to achieve here. Our project is supply voltage regulation, using controller and SCR.
In our project we provide the load with a constant voltage of 240 V ac., in spite of
any variation in the input voltage. The voltage regulation is achieved by controlling the
firing angle of the SCR so precisely that the load receives a constant supply. The
voltage across the load is stepped down and provided to ADC. ADC will produce a
digital signal corresponding to the input analog signal. This digital signal from ADC is
then processed by the controller and generates a firing pulse for SCR, hence controlling
the load current.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
INDEX
1. INTRODUCTION .………………………………………………. 4
2. AIM & OBJECTIVES ....………………………………………... 7
3. PROJECT PLANNING .…………………………………………. 9
4. BLOCK DIAGRAM ...………..………………………………… 12
5. BLOCK DIAGRAM DESCRIPTION .……….………………… 14
6. COMPONENT SEPECIFICATIONS .…………………………. 18
7. CIRCUIT DIAGRAM .…………………………………………. 47
8. FUNCTIONALITY .……………………………………………. 49
9. SOFTWARE FLOW CHART .…………………………………. 51
10. RESULTS & CONCLUSION .…………………………………. 58
11. BIBLIOGRAPHY .……………………………………………... 60
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
CHAPTER 1
Introduction
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
INTRODUCTION
In our day to day life we use a lot many devices to satisfy our needs or to make
our life comfortable and luxurious. Every device needs a power supply, to work on. And
for the optimum functioning of the device it is necessary that the supply should be
reliable. That is, it should provide a constant voltage.
But this is not possible always. There are many reasons due to which there is a
fluctuation in the supply voltage. This change in the supply voltage may cause the
device to damage or make it work in an undesired way, which no one will desire.
Hence the best alternative is to regulate the supply voltage. This is what we have
tried to achieve here. Our project is supply voltage regulation, using controller and SCR.
Silicon Controlled Rectifiers also called Thyristors controller, employing novel
technology, which is designed to provide a price effective solution for applications that
require power, current or voltage regulation with some power factor correction and a
smother process control. Traditional phase-angle control causes lots of harmonic
current distortion on the main power supply. This in turn creates voltage distortion which
affects power quality. There is no simple accessory available for reducing this problem.
However, when simple voltage or current regulation is required often phase-
angle control is the most cost effective solution.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
Thyristors and triacs are switched on by using a gate. They automatically switch
off again when the conducted current reaches zero.
Therefore, these devices can be used in power regulators and by switching at a
predetermined position on the AC sine wave (the phase-angle) the effective voltage can
be reduced or increased. This can be used to regulate voltage or power to a load.
In our project we provide the load with a constant voltage of 240 V ac., in spite of
any variation in the input voltage. The voltage regulation is achieved by controlling the
firing angle of the SCR so precisely that the load receives a constant supply. The
voltage across the load is stepped down and provided to ADC. ADC will produce a
digital signal corresponding to the input analog signal. This digital signal from ADC is
then processed by the controller and generates a firing pulse for SCR, hence controlling
the load current.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
CHAPTER 2
Aim & Objective
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
AIM & OBJECTIVE
AIM:-
To develop a system for controlling fluctuation in the three phase Voltage supply
using SCR and Controller.
OBJECTIVE:-
To upgrade the existing three phase analog regulatory system, to a three phase,
microcontroller based SCR drive system. So that if any fluctuation comes in three phase
voltage supply, controller will Sense that fluctuation and accordingly give triggering
pulses to the SCR to get controlled regulated output at the load.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
CHAPTER 3
Project planning
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
PROJECT PLANNING
Exactly what was planned in the project?
To design hardware for voltage regulation by using SCR bridge
To sense fluctuation in the single phase voltage supply.
To sense zero crossing of the input sine wave.
To get correct firing angle of SCR for getting correct control voltage.
To calculate the correct delay time for giving trigger pulse to SCR.
To trigger SCR depending upon calculated data and get the regulated
output.
To implement the same for three phase voltage supply.
What is achieved?
We designed hardware for voltage regulation by using SCR bridge
We sensed fluctuation in the single phase voltage supply.
We sensed zero crossing of the input sine wave.
We got correct firing angle of SCR for getting correct control voltage.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
We calculated the correct delay time for giving trigger pulse to SCR.
TIME SCHEDULING
S.no Schedule days
1 Understanding project details 2
2 Finalizing project modules 3
3 Data collection 7
4 Selection of Microcontroller and its peripherals 4
5 Component search 11
6 Circuit Design 5
7 Hardware assembly 7
8 Hardware testing and debugging 7
9 Software coding (for calculating correct delay for different
angle)
2
10 Preparing look up table for different ADC values 1
11 Software coding(for voltage fluctuation) 3
12 Testing code on hardware 8
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
13 Project report & presentation 3
CHAPTER 4
Block Diagram
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
BLOCK DIAGRAM
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POWER SUPPLY
SCR BRIDGE CKT
230V AC
MICRO--CONTROLLER
O/P
ZEROCROSSINGDETECTOR
CLOCK & RESET CKT
POTENTIAL DIVIDER
24V AC
A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
CHAPTER 5
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ADC
A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
Block Diagram Description
BLOCK DIAGRAM DESCRIPTION
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
POWER SUPPLY
This is the first block of our system. We have used a step-down centre tap
transformer, with the voltage rating of 240V ac as primary voltage and 24-0-24V ac as
the secondary voltage. The current rating of the transformer is 500mA.
The stepped-down ac signal is supplied to the rectifier & regulator. It consists of a
simple rectifier diode bridge network along with some filtering circuit, for smoothing out
the input signal. This filtered and rectified signal is then regulated using a positive
voltage regulator, to the desired value (say 5 V dc & 15 V dc) and also negative voltage
regulator to the desired value (say -15 V dc).For these purpose; we are using three
regulator chips.
LM7805 (+5V DC)
MC7815C (+15V DC)
L7915 (-15V DC)
The basic input requirement of the two regulators 7815 & 7915 is 23v dc. i.e. it
needs at lest this voltage to provide a constant +/-15V. This is why we have selected
the center-tap transformer of 24V dc. But the input voltage requirement of 7805 is just
about 13v dc; hence we have reduced the voltage of the transformer to 13V through a
resistor in series.
The input of the regulator is provided with a filter capacitor of 10uF, 50v. and the
output with 0.01uf, forming a pie filter for better signal to noise ratio.
ZERO CROSSING DETECTOR
This circuit is containing of OP-AMP UA 741.This is mainly used to detect the
zero crossing of the input sine wave so that we can get Synchronization.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
The output of ZCD is given to the PORT pin 2.5 of the Microcontroller. Here ZCD
is used so that we can give trigger angle to the SCR at Correct time.
The op-amp in the ZCD is just a sine to square wave generator. It converts in the
input 24V ac signal to the square wave of 5 V and of the same frequency as that of the
sine wave. Op-amp UA 741 is provided with a dual supply, obtained from the positive
and negative regulators (+15V & -15V dc).
The output pin of the ZCD is provided with a rectifying diode which restricts the
negative signal from reaching the controller pin to avoid any damage to it.
SCR BRIDGE NETWORK
This block consists of a pair of SCR & diodes. Input to the SCR Bridge circuit is
fluctuated Single phase voltage supply, which is given to anode of both the SCRs and
cathode of both the diodes. Cathode of both the SCRs and Anode of both the diodes
are provided to the load. We have assumed a resistive load of 10K ohm. From this load
resistor one voltage signal will go to the Potential divider for feedback purpose. This will
act as the input signal to the ADC.
The gate of the SCR is connected to the PORT2.0 and PORT2.1. A specific
triggering pulse is provided to the gate of the SCR of sufficient time delay so as to keep
the load voltage constant.
POTENTIAL DIVIDER
To get controlled output we need to give feedback signal from the SCR bridge
circuit to ADC. But here feed back signal is nearer of 240V. So, we required to step it
down to the +5V.
Because of this, here we have used potential divider network. From this potential
divider network we will get voltage signal around +5V. To obtain the voltage of 5V ac
from 240V ac we have used the network ratio of 59:1. The upper 59K resistor is fix while
the lower 1K is a pot of 10k. Then after this voltage signal is given to ADC0808.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
ANALOG TO DIGITAL CONVERTER (ADC 0808)
Here we get input from potential divider network which is around +5V. Then this
analog value is converted to digital data and is given to Microcontroller. ADC 0808 has
four channels but we need only one, hence we have selected channel 0 for input. The 8
bit digital output of ADC is provided to the port 1 of controller.
MICROCONTROLLER 89C51RD2
This block is the only decision making block, which decides whether any
fluctuation in the supply line has occurred or not. It continuously compares the signal
with the reference described in the software. If there is no change then SCR will be fired
by it at phase angle 0 deg. But if it finds some fluctuation, then it will generate the pulse
at a measured time delay to provide the firing angle of the SCR (through gate) such that
the fluctuations will be nullified, and the supply to the load remains unaffected, in-spite
the fluctuations.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
CHAPTER 6
Components Specification
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
COMPONENT SPECIFICATION
POWER SUPPLY
SPECIFICATION OF IC LM7805:-
_ 3-Terminal Regulators
_ Output Current up to 1.5 A
_ Internal Thermal-Overload Protection
_ High Power-Dissipation Capability
_ Internal Short-Circuit Current Limiting
_ Output Transistor Safe-Area Compensation
Description information
This series of fixed-voltage integrated-circuit voltage regulators is designed for a
wide range of applications. These applications include on-card regulation for elimination
of noise and distribution problems associated with single-point regulation. Each of these
regulators can deliver up to 1.5 A of output current. The internal current-limiting and
thermal-shutdown features of these regulators essentially make them immune to
overload. In addition to use as fixed-voltage regulators, these devices can be used with
external components to obtain adjustable output voltages and currents.
Absolute maximum ratings over virtual junction temperature range (unless
otherwise noted)
Input voltage, VI: A7824C 40 V)
All others 35 V
Operating virtual junction temperature, TJ 150C
Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260C
Storage temperature range, Tst -65C to 150C
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
The LM7805 series of three terminal regulators are available with several fixed
output voltages. The voltages available allow regulators to be used in logic systems,
instrumentations, Hi-Fi and other solid state electronics equipment without any external
feedback components.
These ICs are designed as fixed voltage regulator and with adequate heat
sinking can deliver output currents in excess of 1A.The input capacitor Ci=0.33µF is
used, if regulator is located far from the power supply filter capacitor. It filters out the
effect of stray inductance of wire, ceramic or tantalum capacitor may be used. To
improve the transient response of regulator capacitor of 0.1µF is connected at output. It
utilizes common ground fir input and output and has dropout voltage (Vin – Vo) of 2 V.
Device type with input voltages
Output voltage(V)
Output current
QuiescentCurrent(mA)
Line regulation(mV)
Load regulation(mV)
Ripple rejection(dB)
78XXC(35)
51215
1A 8 256075
50120150
807270
78LXXAC(35)
51215
100Ma 3 to 53 to53.1 to 5
102025
51012
625451
78LXXC(35)
51215
100mA 3 to 63 to 6.53.1 to 6.5
102025
51012
605249
78MXX (35)
51215
0.5A 4 to 104 to 104 to 10
50120150
100240300
787169
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
SPECIFICATION OF MC7815 (+15V REGULATOR)
These voltage regulators are monolithic integrated circuits designed as fixed–
voltage regulators for a wide variety of applications including local, on–card regulation.
These regulators employ internal current limiting, thermal shutdown, and safe–area
compensation. With adequate heat sinking they can deliver output currents in excess of
1.0 A. Although designed primarily as a fixed voltage regulator, these devices can be
used with external components to obtain adjustable voltages and currents.
• Output Current in Excess of 1.0 A
• No External Components Required
• Internal Thermal Overload Protection
• Internal Short Circuit Current Limiting
• Output Transistor Safe–Area Compensation
• Output Voltage Offered in 2% and 4% Tolerance
• Available in Surface Mount D2PAK and Standard 3–Lead Transistor Packages
• Previous Commercial Temperature Range has been extended to a Junction
Temperature Range of –40°C to +125°C.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.
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A Project Report on Three Phase Voltage Regulation using SCR & Micro-Controller.