final year project report (1)

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Riphah International University Islamabad
POWER ELECTRONICS TRAINER
B. Sc Electrical Engineering (Electronics)
Batch 2010
Supervisor
Engr. Qaiser Hussain Alvi
Assistant Professor
Submitted By
Syed Bilal Ali 10B19EE
Abu Bakar Munawar 10B84EE
Muhammad Adnan Mushtaq 10B47EE
DEPARTMENT OF ELECTRICAL ENGINEERING
FACULTY OF ENGINEERIRG AND APPLKIED SCIENCES
RIPHAH INTERNATIONAL UNIVERSITY, ISLAMABAD
AUGUST 2014

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POWER ELECTRONICS TRAINER
B. Sc Electrical Engineering (Electronics)
Batch 2010
Supervisor
Engr. Qaiser Hussain Alvi
Assistant Professor
Submitted By
Syed Bilal Ali 10B19EE
Abu Bakar Munawar 10B84EE
Muhammad Adnan Mushtaq 10B47EE
A Project Report submitted in partial fulfillment of the
requirements for the award of Bachelor’s Degree in
Electrical Engineering
DEPARTMENT OF ELECTRICAL ENGINEERING
FACULTY OF ENGINEERING AND APPLIED SCINCES
RIPHAH INTERNATIONAL UNIVERSITY, ISLAMABAD
AUGUST 2014

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Undertaking
I/We certify that project work titled “POWER ELECTRONICS TRAINER” is my/our own work.
No portion of the work presented in this project has been submitted in support of another award
or qualification either at this institution or elsewhere. Where material has been used from other
sources it has been properly acknowledged / referred.
Syed Bilal Ali
10B19EE
Abu Bakar Munawar
10B84EE
Muhammad Adnan Mushtaq
10B47EE

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Acknowledgements
We would like to thank Engr; Qaiser Hussain Alvi guiding us in understanding the concepts of
Power Electronics. .We would like to thank all our teachers especially Engr; Sajid Ali guiding us
in solving our problems related to Power Electronics Trainer. We would also like to thank our
project supervisor Engr; Qaiser Hussain Alvi for his cooperation and support to bring this project
to completion.
We would also like to thank our families and friends for their continuous encouragement and
moral support.

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Contents
Undertaking..................................................................................................................................................................3
Acknowledgements..................................................................................................................................................4
Chapter 1.....................................................................................................................................................................8
Introduction ...........................................................................................................................................8
1 BACKGROUND........................................................................................................................................8
1.1 Power Electronics ...........................................................................................................................8
1.2 History of Power Electronics..........................................................................................................8
1.3 Power Semiconductor devices: .......................................................................................................9
2 What is Power Electronics Trainer.........................................................................................................9
1.1. Block Diagram........................................................................................................................10
1.2. About Block diagram..............................................................................................................11
1.3. DC POWER SUPPLY ............................................................................................................11
............................................................................................................................................................11
 LM7805 (3 pin voltage regulator)...............................................................................................11
 LM 7812 (3-pin voltage regulator) .............................................................................................12
 LM317 (3-Terminal Positive Adjustable Regulator) ..................................................................14
1.4. AC Power Supply: ..................................................................................................................15
a. XR-2206......................................................................................................................................15
1.5. Characteristic Block:...............................................................................................................17
1.6. Potentiometer Block:...............................................................................................................17
1.7. Triggering Block:....................................................................................................................17
1.8. Power Circuit Block:...............................................................................................................17
1.9. Testing Block:.........................................................................................................................17
Chapter 2...................................................................................................................................................................18
Theory Related to Project ................................................................................................................18
Statement:..........................................................................................................................................18
2.1 Technique 1...............................................................................................................................18
2.1.1 Designing modules in Proteus 8: .............................................................................................18
2.2 Technique 2...............................................................................................................................19
2.2.1 Hardware designing: ..................................................................................................................19

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2.3 Components Used:........................................................................................................................19
2.3.1 Silicon controlled rectifiers (SCR) (c106d): ........................................................................19
............................................................................................................................................................21
2.3.2 TRIAC (BT136).......................................................................................................................22
2.3.3 DIAC (DB3) .............................................................................................................................25
2.3.4 UJT (2n2646p)...........................................................................................................................28
a. Characteristics of UJT.................................................................................................................28
Chapter 3...................................................................................................................................................................29
Implementation of Project................................................................................................................29
3.1 Experiments Performed............................................................................................................29
3.2 Identify the terminals of SCR:..................................................................................................29
Conclusion: .........................................................................................................................................29
3.3 Uncontrolled rectifiers of power diodes..................................................................................30
Observations:......................................................................................................................................30
Conclusion:..........................................................................................................................................30
3.3 Characteristics of SCR when anode and gate both are DC ...............................................30
Observations:......................................................................................................................................31
Conclusion:..........................................................................................................................................31
3.4 To adjust the firing angle α of SCR.........................................................................................32
Conclusion...........................................................................................................................................33
3.5 characteristics of SCR when anode source is AC and gate source is DC .......................33
Conclusion...........................................................................................................................................34
3.6 To observe and measure the 180 angle of the SCR............................................................34
Conclusion...........................................................................................................................................35
3.7 single phase half wave controlled rectifier.............................................................................35
Conclusion...........................................................................................................................................37
3.8 Single phase full wave control rectifier...................................................................................37
Observations:......................................................................................................................................38
Conclusion:..........................................................................................................................................38
3.9 Characteristics of DIAC ............................................................................................................38
Conclusion:..........................................................................................................................................39
3.10 & 3.11 Triggering response of TRIAC..................................................................................39
Observations:......................................................................................................................................41

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Conclusion:..........................................................................................................................................41
3.12 Triggering response of TRIAC...............................................................................................42
Observations:......................................................................................................................................42
Conclusion...........................................................................................................................................43
3.13 Generation of pulse triggering using a UJT.........................................................................43
Conclusion:..........................................................................................................................................44
3.14 UJT triggering circuit for SCR................................................................................................45
Conclusion...........................................................................................................................................46
Chapter 4...................................................................................................................................................................47
Simulation Results.............................................................................................................................47
Dc Power supply circuit diagram: ..................................................................................................47
PCB design (DC Power supply) :...................................................................................................47
3-D View: ...........................................................................................................................................48
Dimensions:.......................................................................................................................................48
Ac supply circuit diagram:...............................................................................................................48
PCB Layout of Ac supply: ...............................................................................................................49
3-D View ............................................................................................................................................49
Dimensions:.......................................................................................................................................49
TRAINER LAYOUT:.........................................................................................................................50
Dimensions:.......................................................................................................................................50
3-D View: ...........................................................................................................................................51
Potentiometer layout:.......................................................................................................................51
............................................................................................................................................................51
Dimensions:.......................................................................................................................................52
3-D View: ...........................................................................................................................................52
Conclusion .................................................................................................................................................................53
Future Recommendations .......................................................................................................................................54
References ...................................................................................................................................................................55

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Chapter 1
Introduction
1 BACKGROUND
1.1 Power Electronics
Power electronics combine power, electronics, and control. Control deals with the steady-
state and dynamics characteristics of closed -loop systems. Power deals with the static and
rotating power equipment for generation, transmission, and distribution of electric energy.
Electronics deal with the solid state devices and circuits for signal processing to meet the desired
control objectives. Power electronics may be defined as the application of solid state electronics
for the control and conversion of electric power.
Power electronics are based primarily on the switching of power semiconductor devices.
With the development of power semiconductor technology, the power handling capabilities and
the switching speed of the power devices have improved tremendously .Power electronics have
already found an important place in modern technology and are now used as in great variety of
high power products, including heat controls light controls, motor controls, power supplies,
vehicle propulsion systems, and high voltage direct current (HVDC) systems.
The power conversion systems can be classified according to the type of the input and output
power
AC to DC (rectifier)
DC to AC (inverter)
DC to DC (DC-to-DC converter)
AC to AC (AC-to-AC converter)
1.2 History of Power Electronics
The origins of power electronics can be traced back many years, at which time mercury-arc
devices were utilized for the rectification of AC to DC or the inversion of DC to AC. However,
today’s rapidly growing usage of power electronics has resulted from the development of solid-
state power devices. Specifically, then, we will limit the use of the name power electronics to
those applications in which electrical power flows through and is controlled by one or more
solid-state power devices. All of the important parameters of the electrical waveform are subject
to regulation or conversion by solid-state power devices, including effective voltage, effective
current, frequency, and/or power factor.
Often the control of electrical power is desired simply as a means for controlling some non-
electrical parameter. For example, drives for controlling the speed of a motor. In other

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applications, power electronics is used to control the temperature of an oven, the rate of an
electrochemical refining process, the intensity of lighting, etc.
1.3 Power Semiconductor devices:
A majority of the devices are made of silicon. These devices can be divided broadly into three
types.
 Power diodes
 Transistors
 Thyristors
These can be divided into five types.
 Power diodes
 Thyristors
 Power bipolar junction transistors.(BJTS)
 Power metal oxide semiconductor field effect transistors (MOSFETS)
 Insulated-gate bipolar transistors (IGBTs)
2 What is Power Electronics Trainer
As in our daily life we use a lot of electronic devices which are controlled from external circuit.
Such as Heating and lighting control, Induction heating, Uninterruptible power supplies (UPS),
Fluorescent lamp ballasts, Electric power transmission, automotive electronics, Electronic
ignitions, Motor drives, Battery chargers, Electric vehicles, Alternators, Flywheels, Electric
vehicles Motors, Regenerative braking ,Switching power supplies, Power conditioning for
Switching power supplies, Spacecraft power systems, Power conditioning for alternative power
sources, Solar cells ,Fuel cells, Flywheel powered Fuel cells, Wind turbines. To understand
these controlling circuits there must be a trainer by which the controlling devices can be studied.
By using power semiconductor switching devices such as Silicon controlled rectifiers (SCR),
TRIAC, DIACS, uni-junction transistor (UJT) the output wave form is measured. Thyristors and
triacs are switched on by using a gate. They automatically switch off again when the conducted
current reaches zero. Power electronics trainer contains different blocks likewise dc supply block
, Ac power supply block, triggering block , potentiometer block ,characteristics block , power
circuit block. The trainer is designed to present and practice principle of basic power electronics.
The trainer shows the standard symbols of electronic control on desktop panel.

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The system is supplied by power supplies required to run the experiment. The connection to and
from the modules are easy and save to build. It will give an ease to the user for understanding
basic concept of power electronics. In this project we make different modules for trainer on
which we performed lab experiments. Experiments will be discussed in last section of the report.
1.1. Block Diagram

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1.2. About Block diagram
1.3. DC POWER SUPPLY
We made dc power supply using center tap transformer with primary voltage of 220Vac
and secondary voltage of 15+15Vac with 1 A. We make the fixed 12V dc using LM7812 and
fixed 5V dc using LM7805.For variable dc supply we use LM317 which gives us 0-40V dc. For
protection we use 2A fuse in series with the secondary winding.
 LM7805 (3 pin voltage regulator)
Features
 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

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 LM 7812 (3-pin voltage regulator)
Features
 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

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 LM317 (3-Terminal Positive Adjustable Regulator)
Features
• Output-Current In Excess of 1.5 A
• Output-Adjustable Between 1.2 V and 37 V
• Internal Thermal Overload Protection
• Internal Short-Circuit Current Limiting
• Output-Transistor Safe Operating Area Compensation
Absolute maximum ratings

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1.4. AC Power Supply:
We make the ac supply using xr2206 from which we get 6Vp-p and variable frequency
from 0-1 MHz .Our sine wave generator will give square wave and triangular wave also.
XR-2206 is a 16 pin IC, pin 1 and pin 12 is put to ground .Vcc is given to pin 4, at pin 3
potentiometer is placed for varying amplitude as output amplitude is directly proportional to the
resistance, R3, on Pin 3. The frequency of oscillation, fo, is determined by the external timing
capacitor, C, across Pin 5 and 6, and by the timing resistor, R, connected to either Pin 7 or 8. The
frequency is given as:
f =1/RC Hz
Frequency can be adjusted by varying either R or C. Temperature stability is optimum for
4kohm< R < 200kohm. Recommended values of C, are from 1000pF to 100microF.at pin 2 we
will get sine/triangle wave form and at pin 11 we get square wave form .for triangle wave form
pin 13 and pin 14 must be open circuit (s1 open).
a. XR-2206
FEATURES
 Low-Sine Wave Distortion, 0.5%, Typical
 Excellent Temperature Stability, 20ppm/°C, Typ.
 Wide Sweep Range, 2000:1, Typical
 Low-Supply Sensitivity, 0.01%V, Typ.
 Linear Amplitude Modulation
 TTL Compatible FSK Controls
 Wide Supply Range, 10V to 26V
 Adjustable Duty Cycle, 1% TO 99%

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1.5. Characteristic Block:
It contains three main components TRIAC (BT136), SCR (c106d), UJT (2n2646p) and
DIAC (DB3). For finding the characteristics values we put these component in this block.
1.6. Potentiometer Block:
It contains Variable resistors of values (1kΩ,2kΩ,10k Ω,5kΩ,50kΩ,500kΩ,100kΩ) 1/4
Watt with Fixed resistors of (33Ω ,56Ω ,100Ω ,150Ω ,220Ω ,470Ω ,1kΩ,1.2kΩ 1.5kΩ
,5.6kΩ ,47kΩ ,100kΩ ) 1/4 Watt and the resistance tolerance is 20%
Maximum Voltage: 500 VAC
Power Rating: 250mA, 0.25W
Total Rotation: 300°
1.7. Triggering Block:
It contains the triggering components likewise UJT, resistors and capacitors for triggering
the SCR and TRIAC.
1.8. Power Circuit Block:
It contains power diodes used for uncontrolled rectifiers.
1.9. Testing Block:
It contains two analog meters i.e. dc Voltmeter and dc Ampere meter. The range of
voltmeter is 0-50 V dc and ampere meter has range about 0-500mA

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Chapter 2
Theory Related to Project
Statement:
The Power Electronics Trainer will be based on the basic principle of Power Electronics .To
develop a trainer in which all experiments of power electronics can be implemented.
2.1 Technique 1
2.1.1 Designing modules in Proteus 8:
First we have designed all our modules in proteus 8 i.e. dc supply module, ac supply
module, trainer module. In designing we checked all the possible errors and then removed. We
make the design in that way that user can use in easy way. To insure the safety we used fuses.
We also checked the compatibility of Power Electronics Trainer that how much experiments can
be performed in this trainer, which is minimum 14 lab experiments. We checked our circuit
layouts, measured there dimensions, port sizes, length from one port to another port and checked
the final shape of our modules in 3-d view.
3-d view of dc power supply

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2.2 Technique 2
2.2.1 Hardware designing:
For implementation of our circuit first we used copper printable circuit board (PCB).but
as it is not too much good as fiber PCB .As fiber is strong and reliable to use in hardware that’s
why we use it in our project .we print our required layouts on the yellow paper after that we put
these papers on the fiber PCB sheet and starts ironing it for 10 mints then after when the
complete circuit is transferred to the PCB Sheet. After that we put these PCB sheets in a tub with
some water and ferric chloride for etching, when etching is completely done then only circuit on
fiber sheet has the copper, its mean our etching is complete then it is cleaned by petrol. The
output points are drilled for putting connectors and components. After that soldering is done
with soldering iron, for connecting all modules hardware we used glue gun and magic depoxi.
All these modules are then adjusted in a plastic sheet panel of 2*2 foot.
2.3 Components Used:
 SCR c106d
 TRIAC (BT136)
 UJT(2n2646p)
 DIAC(DB3)
 Diode(1n4007)
 LED (red)
 Resistors and potentiometers
 Transformer
 Regulators
 Banana ports(male and female)
 Analog Meters
 XR-2206
 Knobs
2.3.1 Silicon controlled rectifiers (SCR) (c106d):
We have used SCR (C106d) through hole in our trainer. The thyristor is a Type 2 switch
containing three internal PN junctions in series. When the anode is negative with respect to the
cathode, the center junction is forward biased, but the two outer Junctions are reversed biased.
Therefore a thyristor blocks the flow of reverse current until the breakdown voltage of the two
other junctions is exceeded. If the anode is positive with respect to the cathode, the two outer
junctions are forward biased but the center junction is reverse biased. Therefore forward current
is also blocked until the breakdown voltage of the center junction is exceeded. However, the
third terminal of a thyristor is connected to the P layer adjoining the cathode N layer. If this
terminal is made positive with respect to the cathode, forward current flows across the cathode

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PN junction. If the anode terminal is also positive, this forward current across the cathode
junction initiates a regenerative internal action which then permits current flow across the
reverse biased center junction. In other words, this third terminal allows the thyristor to be turned
on. Because of the control which this terminal exercises over current flow, it is known as the
“gate”. Once forward current flow is initiated, the thyristor latches in its on state, the gate loses
its control, and current continues until it is commutated by some external means.
i. Steady-State V-I Characteristic of a Thyristor
The reverse blocking state is similar to that of a diode, as is the forward blocking state,
and each is characterized by a leakage current and a breakdown voltage.
When a small current is applied to the gate, the forward breakover voltage decreases. If the
applied forward voltage exceeds this decreased breakover voltage, the thyristor switches to its
on-state. This state is characterized by a forward voltage drop, Once the thyristor is in its on-
state, it will remain there until the current is reduced (by external means) to a value which is less
than a minimum value known as the holding current. It then reverts to the blocking state.

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2.3.2 TRIAC (BT136)
The major drawback of an SCR is that it can conduct current in one direction only.
Therefore, an SCR can only control dc power or forward biased half-cycles of a.c. in a load.
However, in an a.c. system, it is often desirable and necessary to exercise control over both
positive and negative halfcycles. For this purpose, a semiconductor device called triac is used.
A triac is a three-terminal semiconductor switching device which can control alternating current
in a load. Triac is an abbreviation for triode a.c. switch. ‘Tri’– indicates that the device has three
terminals and ‘ac’ means that the device controls alternating current or can conduct current in
either direction.
i. Characteristics of TRIAC
Because the triac essentially consists of two SCRs of opposite orientation
fabricated in the same crystal, its operating characteristics in the first and third quadrants
are the same except for the direction of applied voltage and current flow. The V-I
characteristics for triac in the 1st
and 3rd
quadrants are essentially identical to those of an
SCR in the 1st
quadrant. The triac can be operated with either positive or negative gate
control voltage but in normal operation usually the gate voltage is positive in quadrant I
and negative in quadrant III.
V-I characteristics of TRIAC

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2.3.3 DIAC (DB3)
A diac is a two-terminal, three layer bidirectional device which can be switched from its
OFF state to ON state for either polarity of applied voltage. The diac can be constructed in either
npn or pnp form. The two leads are connected to p-regions of silicon separated by an n-region.
The structure of diac is very much similar to that of a transistor. However, there are several
important differences:
(i) There is no terminal attached to the base layer.
(ii) The three regions are nearly identical in size.
(iii)The doping concentrations are identical (unlike a bipolar transistor) to give the device
symmetrical properties.
When a positive or negative voltage is applied across the terminals of a diac, only a small
leakage current IBO will flow through the device. As the applied voltage is increased, the leakage
current will continue to flow until the voltage reaches the breakover voltage VBO. At this point,
avalanche breakdown of the reverse-biased junction occurs and the device exhibits negative
resistance i.e. current through the device increases with the decreasing values of applied voltage.
The voltage across the device then drops to ‘breakback’ voltage VW.
For applied positive voltage less than + VBO and negative voltage less than −VBO, a small
leakage current (±IBO) flows through the device. Under such conditions, the diac blocks the
flow of current and effectively behaves as an open circuit. The voltages + VBO and –VBO are
the breakdown voltages and usually have a range of 30 to 50 volts.
When the positive or negative applied voltage is equal to or greater than the breakdown voltage,
diac begins to conduct and the voltage drop across it becomes a few volts. Conduction then
continues until the device current drops below its holding current.
Functioning as a trigger diode with a fixed voltage reference, the DB3/DB4 series can be used in
conjunction with triacs for simplified gate control circuits or as a starting element in fluorescent
lamp ballasts.
Voltage-current characteristic curve

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Diagram 3: Rise time measurement.

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2.3.4 UJT (2n2646p)
A unijunction transistor (abbreviated as UJT) is a three-terminal semiconductor switching
device. This device has a unique characteristic that when it is triggered, the emitter current
increases regeneratively until it is limited by emitter power supply. Due to this characteristic, the
unijunction transistor can be employed in a variety of applications e.g., switching, pulse
generator, saw-tooth generator etc.
Since the device has one pn junction and three leads, it is commonly called a unijunction
Transistor .With only one pn-junction, the device is really a form of diode. Because the two base
terminals are taken from one section of the diode, this device is also called double-based diode.
The emitter is heavily doped having many holes. The n region, however, is lightly doped. For
this reason, the resistance between the base terminals is very high (5 to 10 kΩ) when emitter lead
is open.
a. Characteristics of UJT
Initially, in the cut-off region, as VE increases from zero, slight leakage current flows
from terminal B2 to the emitter. This current is due to the minority carriers in the reverse biased
diode .Above a certain value of VE, forward IE begins to flow, increasing until the peak voltage
VP and current IP are reached at point P.
After the peak point P, an attempt to increase VE is followed by a sudden increase in emitter
current IE with a corresponding decrease in VE. This is a negative resistance portion of the curve
because with increase in IE, VE decreases. The device, therefore, has a negative resistance region
which is stable enough to be used with a great deal of reliability in many areas e.g., trigger
circuits, saw tooth generators, timing circuits. The negative portion of the curve lasts until the
valley point V is reached with valley-point voltage VV and valley-point current IV. After the
valley point, the device is driven to saturation.
V-I graph for UJT

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Chapter 3
Implementation of Project
3.1 Experiments Performed
About 14 experiments are implemented in our trainer and we performed all of them one
by one. Result are given below.
3.2 Identify the terminals of SCR:
Set the digital meter at ohmmeter of any suitable range. Checked all the terminals of
SCR. Only two terminals give one specified resistance. The common terminal of digital meter
was cathode.
The active wire (+ve wire) of digital meter was gate. Remember anode and cathode are power
terminals and gate is control terminal of SCR.
Conclusion:
After completing this experiment, we have identified the terminals of SCR and also
confirmed the working and functionality of SCR.

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3.3 Uncontrolled rectifiers of power diodes
We connected power diodes in the form of the bridge circuit as given below. We applied
the ac signal from 0-10Vp-p to the rectifier circuit .oscilloscope was connected on the output
across the R1 .The output was less than the input applied because some voltage drop occurs
across the power diodes.
Circuit for uncontrolled rectifier.
Observations:
Serial Number Vin (peak to peak) Vo across (each
diode)
Vo total across R1
1 10Vp-p D1=5.5v D2=5.5v
D3=5.4 D4=5.5
5Vp-p
2 8Vp-p D1=4v D2=4v D3=4
D4=4.2
4Vp-p
3 6Vp-p D1=3v D2=3v D3=3
D4=3v
3Vp-p
Conclusion:
After completing this experiment, we have shown the characteristics of the power
diode.in the uncontrolled bridge rectifier circuit, we have shown the working and functionality of
power diode.
3.3 Characteristics of SCR when anode and gate both are DC
We have connected the circuit as below. We measured the IAk which flows in the SCR
when SCR is in on state. The thyristor is turned off in two ways.
1) By decreasing V1 2) By increasing the load.

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Apply these two conditions to reduce IH. The gate voltage and current should be enough to turn
on the thyristor.in our experiment voltage is 5V and current is more than 1mA.
IAK=
Circuit for characteristics of SCR
Observations:
V1 (v) IG (mA) IAK measured
(mA)
VAK (v) IAK calculated
(mA)
5V 1 mA 3.61 mA 0.55 V 3.7 mA
5V 2.02 mA 3.61 mA 0.65 V 3.65 mA
5V 2.55 mA 3.60 mA 0.65 V 3.625 mA
Conclusion:
In this experiment we have proved that a thyristor needed a signal triggering to conduct.
The holding current is the minimum anode current needed to maintain the thyristor in the on
state. Once the thyristor is turned on by the gate signal and the anode current is greater than the
holding current IH, the thyristor will remain conducting even if the gate signal is removed.

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3.4 To adjust the firing angle α of SCR
Firing angle is that angle after this angle SCR will turn on. We can adjust this angle from
0- .firing angle is adjusted through gate voltage and current.it is also possible to change the
output voltage by varying firing angle.
Circuit for adjusting firing angle of SCR
Waveforms

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Conclusion
After completing this experiment, we are able to change the firing angle of SCR by
changing the different values of gate voltage and gate current at gate control circuit.
3.5 characteristics of SCR when anode source is AC and gate source is DC
By changing the variable resistance gate current can be controlled and hence firing angle is
varied. The Ig must be greater than 200µA to turn on the SCR.
Vdc= (1+cosα)
Ig (on) ≥ 200µA
Vg (on) ≥ 0.7 V
Circuit for SCR when anode source is AC and gate source is DC.

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Waveforms
Conclusion
After completing this experiment, we are able to adjust the firing angle of SCR when
anode source is AC and gate source is DC. It is also possible to vary the output voltage of the
circuit by changing the firing angle of SCR.
3.6 To observe and measure the 180 angle of the SCR
By changing the variable resistor we can change the value of RC time constant, the time
constant RC circuit controls the firing angle of SCR.
When negative cycle comes D2 on and C begins to change up to its peak value, AT full negative
peak D2 turns off during remaining negative cycle C continuously discharges.
During positive half cycle C continue its charging because of time constant. After C fully
discharged it again start to charge with opposite polarity. When it charge to a certain value it
turns the diode D1.so the SCR switch like short circuit and load current starts flow. Firing angle
is measured by comparing the output signal with input signal, where the difference of the
position of the output to the input signal is firing angle.

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Circuit for measuring 180 firing angle of SCR
α + α+
Wave forms
Conclusion
After completing this experiment, we are able to vary the firing angle of thyristor in full
range by using the RC phase shift circuit.
3.7 single phase half wave controlled rectifier
For positive half cycle of input ac supply SCR is forward biased and turned on and output
voltage is appeared across the load. the instant of time where the SCR turns on is called the firing
angle α of the SCR. the firing angle of SCR is varied by changing the value of the potentiometer

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in the circuit the positive half of output can also control by changing the value of α.the average
dc output voltage can be calculated as
Vdc= (1+cosα)
When α=0 then maximum output appears at the load.
Circuit for half wave controlled rectifier
α α+ α+
Wave forms

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Conclusion
After completing this experiment, we are able to measure and calculate the average
controlled dc output voltage in the single phase half wave controlled rectifiers by using thyristor
as switches.
3.8 Single phase full wave control rectifier
The bridge rectifier circuit provides the full wave rectified output voltage. This
rectified voltage will apply on the SCR with the help of voltage divider circuit. The voltage
divider circuit consists of two resistors.one resistor is fixed and other is variable which is used to
control the firing angle of SCR in the full wave controlled circuit. The output voltage is varied by
changing this firing angle. The dc value at O/P may be given as
Vdc (average) = (1+cosα)
Circuit of full wave controlled rectifier
Waveforms

38
Observations:
Serial number Vin(input voltage) Vout (measured) Vout ( calculated )
1 3Vp-p 0.4Vp-p 0.5Vp-p
2 4Vp-p 0.5Vp-p 0.6Vp-p
3 6Vp-p 1.3Vp-p 1.2Vp-p
Conclusion:
After completing this experiment, we are able to measure and calculate the average controlled dc
output voltage across the load in the single phase full wave controlled rectifier.
3.9 Characteristics of DIAC
The circuit is connected as below, to measure the breakover voltage of DIAC we give it a dc
power supply and we measured the forward break over voltage is 31V and in reverse the break
over voltage is measured which is 31V.In circuit when LED is on then it means the current flows
in the circuit when its breakover voltage occur.
Circuit diagram for characteristics of DIAC

39
Conclusion:
After completing this experiment, we are able to know that DIAC can turn on from the off state
to the on state on both directions, because it has bidirectional symmetrical directions switching.
3.10 & 3.11 Triggering response of TRIAC
The main objective of this experiment is to investigate the triggering response of
TRIAC in the four quadrants and determine the holding current of IH1 and IH2
Circuit diagram of first quadrant triggering..
Starting at 0V, increase the voltage V1 until the TRIAC triggers and the LED lights up .Record
the voltage at voltmeter and current on Amps meter when LED is on. This TRIAC triggers by
applying a positive voltage to the terminal A2 and opposite voltage to the gate G with respect to
the A1 and this is called as first quadrant triggering.

40
A2
A1
Circuit diagram of second quadrant triggering.
Starting at 0V, increase the voltage V1 until the TRIAC triggers and the LED lights up .Record
the voltage at voltmeter and current on Amps meter when LED is on. This TRIAC triggers by
applying a negative voltage to the terminal A2 and opposite voltage to the gate G with respect to
the A1 and this is called as second quadrant triggering.
Modify the circuit again by applying a negative voltage to terminal A2 and gate G. gate G is
given a negative voltage by reversing the polarity of V1 as given below.
A2
A1
Circuit diagram of third quadrant triggering
Triggered the TRIAC in previous step and record the voltage in voltmeter and current on amp
meter. TRIAC triggering by applying negative voltage to terminal A2 and to gate G is known as
third quadrant triggering.
Modified the circuit again by applying a positive voltage to terminal A2 and a negative voltage
to gate G, as given below.

41
A2
A1
Circuit diagram of fourth quadrant triggering
Pz = VI
Observations:
Quadrant G A2 Voltage Current Pz (mW)
I + + 1.20V 1.44mA 1.72mW
II + - 1.25V 3.84mA 4.8mW
III - - 1.16V 2.5mA 2.9mW
IV - + 1.18V 4.05mA 4.79 mW
Conclusion:
After completing this experiment, we are able to know that the TRIAC operates at four operation
quadrants with different response for each quadrant. As is the case with the thyristor, a TRIAC
also has a holding current IH but in (both directions).

42
3.12 Triggering response of TRIAC
We connect the circuit given below diagram
Circuit for triggering TRIAC
Vs=1- + sin
Observations:
Sr.No Vin(p-p) α Vout(measured) Vout(calculated)
1
6V(p-p) 20
ₒ 5.4V(p-p) 5.3 V(p-p)
2
4 V(p-p) 15
ₒ 3.8 V(p-p) 3.7 V(p-p)
3 8 V(p-p)
30
ₒ 7.6 V(p-p) 8.466 V(p-p)

43
Conclusion
After completing this experiment, we are able to know the triggering of TRIAC by using RC
phase shifter circuit and also how to calculate the firing angle of TRIAC.
3.13 Generation of pulse triggering using a UJT
The unijunction transistor (UJT) is commonly used for generating triggering signals
for SCRs. UJT has three terminals called the emitter E, base1 B1, and base two B2. Between B1
and B2 the unijunction has the characteristics of an ordinary resistance. This resistance is the
interbase resistance RBB and has value in the range 4.7 to 9.1Kohm.
When dc voltage VS is applied, the capacitor C charged through resistor R because the emitter
circuit of the UJT is in the open state the time constant of the charging circuit is T1 = RC. When
the emitter voltage VE, which is same as the capacitor voltage VC, reaches the peak voltage VP,
the UJT turn ON and capacitor C discharges through RB1 at the rate determine time constant
T2=RB1C. T2 is much smaller than T1. When the emitter voltage VE decays the valley point Vv,
the emitter ceases to conduct, the UJT turn OFF, and the charging cycle is repeated. The wave
form of the triggering voltage VB1 is identical to the discharging current of capacitor C. The
triggering voltage VB1 should be designed to be sufficiently large to turn ON the SCR. The
period of oscillation, T, is fairly independent of the dc supply voltage VS, and is given by
T= =RC ln
Where parameter ŋ is called the intrinsic stand-off ratio. The value of ŋ lies between 0.51 and
0.82.
We made the circuit given below
Circuit diagram of generation of pulse triggering using UJT.

44
Waveforms
When the capacitor charges through power supply and when it charge to the value greater than
VP it conducts or UJT turns ON and capacitor at this instant goes to discharging mode. As C
reaches the value V,UJT 0++ and capacitor charging starts again. The output taken at VR2 and
platted.
As
R1 <
R2 >
If the circuit satisfies the above two criteria of R1 and R2, it works as relaxation oscillator.
Conclusion:
After completing this experiment, we are able to observe that when R1 and C1
increases, the period of trigger signal increase to and oppositely frequency decreases. When R3
increase, the voltage drop between B2 and B1 decreases as well as the voltage up. The UJT will
only function at the negative region of the resistance the adjustment of the value of R in the
trigger circuit is meant to fulfill this condition.

45
3.14 UJT triggering circuit for SCR
We connect the circuit given below diagram.
Circuit diagram for UJT triggering circuit for SCR.

46
UJT output pulse is used here to trigger on SCR. UJT used in controlled circuit for SCR to
provide gate turn on pulse.
The bridge converts AC to DC and full wave dc. A zener
diode provides specific voltage or fix voltage to UJT. UJT
work here as relaxation oscillator which produces a pulse
used to turn on SCR.
SCR conducts only when gate pulse reaches at its gate
terminal and turn SCR on current flows through SCR and to
load. The SCR off only when voltage applied across it goes
to zero or in reverse direction polarity.
Conclusion
After completing this experiment, we are able
to turn on the SCR by using the UJT triggering circuit at the
gate terminal of SCR. By using voltage control at the
triggering pulse frequencies control enables to be controlled
In closed loop manner.
Wave form for the circuit diagram.

47
Chapter 4
Simulation Results
Dc Power supply circuit diagram:
PCB design (DC Power supply) :

48
3-D View:
Dimensions:
Size = 195.584 X 129.546 mm (L X W)
Ac supply circuit diagram:

49
PCB Layout of Ac supply:
3-D View
Dimensions:
Size = 134.62 X 66.04 mm (L X W)

50
TRAINER LAYOUT:
Dimensions:
Size = 304.8 X 256.54 mm (LXW)

51
3-D View:
Potentiometer layout:

52
Dimensions:
Size = 236.22 X 204.47 mm (L X W)
3-D View:

53
Conclusion
We started the project with the objectives mentioned in the project statement and achieved all of
them. We have implemented all modules given in the block diagram in chapter 1.we have made
the project much economical and cheaper. Our trainer will show the basic response of power
electronic components. The modules are safe and secure to achieve the reliability of the system.
Experiments are performed and results are showed in chapter3. This trainer will give an ease in
making circuit to user, as all modules are implemented in a single desktop panel.

54
Future Recommendations
We would like to recommend the following features to be incorporated in our developed
software
 We would recommend for improvement in design software, we used proteus 8.
 We would recommend the use of multi meter instead of analog meters for the
measurement of resistance and ac voltage and current.
 We would recommend the use of LCD with ac supply.
 We would recommend to improve the body of the panel also.

55
References
Books:
[1] Muhammad H. Rashid, Power Electronics circuits, Devices and application (3rd
edition) paper
back August 14,2003, ISBN: 13: 978-0131011403
[2] John William motto, JR ,Introduction to Solid State Power Electronics, POWEREX, Inc. 200
Hillis Street Youngwood, PA 15697-1800
Websites:
 www.datasheets4u.com
 www.datasheetcatalog.com
 www.semiconductor.phillips.com
 www.alldatasheet.com

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