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 3

rd 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

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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

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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.

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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.

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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).

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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) 20ₒ

5.4V(p-p) 5.3 V(p-p)

2

4 V(p-p) 15ₒ

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)

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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.

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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.

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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.

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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.

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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.

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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

Documents

final year project report (1)