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2. Power Electronics
and
Drives
Chinttan N. Dewalia
4/8, Anandnagar, Paud Road, Kothrud, Pune-411038.

3. First Indian Edition, April, 2010
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Chinttan N. Dewalia
Diploma in Instrumentation and ControlEngineering
(Dr. Babasaheb Ambedkar Technological University, Lonere.)
B.E. Instrumentation Engineering
( Dr. D.Y.Patil college of engineering ,Pimpri,Pune.)
The Indian Edition: Rs. 360.00
Power Electronics and Drives
By Chinttan N. Dewalia
© April, 2010, Chinttan Publications
Published by Chinttan Publications, 4/8, Anandnagar, Paud Road, Kothrud , Pune – 411038., Tel.no.: 8888101055, 9226269333. E-
mail: chinttanpublications@gmail.com
Printed in India

4. Table of contents iii
Contents
Preface xiii
Acknowledgements xiv
Dedication xv
Roadmap to the syllabus xvi
1 POWER SEMICONDUCTOR DEVICES...........................[1-1 to 1-144]
1.1 INTRODUCTION..................................................................................................................[1-1]
1.2 POWER DIODES..................................................................................................................[1-2]
1.2.1 Construction [1-2]
1.2.2 Steady state characteristics .................................................................................................................................[1-3]
1.2.3 Switching characteristics of power diode.........................................................................................................[1-4]
1.2.4 Type of power diodes ..........................................................................................................................................[1-7]
1.3 DATA SHEET AND RATINGS OF POWER DIODES .........................................................[1-8]
1.3.1 Applications [1-11]
1.4 POWER BJT........................................................................................................................[1-11]
1.4.1 Construction........................................................................................................................................................[1-11]
1.4.2 Operation..............................................................................................................................................................[1-12]
1.4.3 Effect of collector drift layer ............................................................................................................................[1-12]
1.4.3.1 Steady state characteristics of power BJT..............................................................................[1-13]
1.4.3.2 Switching characteristics...........................................................................................................[1-14]
1.4.4 Switching limits ..................................................................................................................................................[1-16]
1.4.4.1 Second Breakdown.....................................................................................................................[1-16]
1.4.4.2 Forward biased safe operating area (FBSOA) .......................................................................[1-17]
1.4.4.3 RBSOA..........................................................................................................................................[1-17]
1.4.4.4 Power derating ............................................................................................................................[1-17]
1.4.4.5 Breakdown voltages...................................................................................................................[1-18]
1.4.4.6 Thermal runaway........................................................................................................................[1-18]
1.4.5 Ratings and data sheets of power BJT ............................................................................................................[1-19]
1.5 POWER MOSFET...............................................................................................................[1-21]
1.5.1 Construction........................................................................................................................................................[1-21]
1.5.2 Operation..............................................................................................................................................................[1-23]
1.5.3 Static characteristics of power MOSFET .......................................................................................................[1-24]

5. Table of contentsiv
1.5.4 Switching characteristics of power MOSFET................................................................................................[1-24]
1.5.4.1 Turn on characteristics...............................................................................................................[1-25]
1.5.4.2 Turn off characteristics..............................................................................................................[1-25]
1.5.5 Safe operating Area (SOA)................................................................................................................................[1-26]
1.5.6 Parallel operation................................................................................................................................................[1-27]
1.5.7 Ratings and data sheet of MOSFET ................................................................................................................[1-28]
1.5.8 Do’s and don’ts...................................................................................................................................................[1-29]
1.5.9 Advantages ..........................................................................................................................................................[1-29]
1.5.10 Applications of Power MOSFETs ...............................................................................................................[1-29]
1.6 STATIC INDUCTION TRANSISTOR (SIT).......................................................................[1-30]
1.7 INSULATE GATE BIPOLAR TRANSISTOR (IGBT).........................................................[1-31]
1.7.1 Construction [1-31]
1.7.2 Operation..............................................................................................................................................................[1-33]
1.7.3 Steady state characteristics of IGBT................................................................................................................[1-33]
1.7.4 Switching characteristics of IGBT...................................................................................................................[1-34]
1.7.5 Safe operating area (SOA).................................................................................................................................[1-35]
1.7.6 Application of IGBT...........................................................................................................................................[1-36]
1.7.7 Ratings and data sheets of IGBT......................................................................................................................[1-36]
1.8 BASE / GATE DRIVE CIRCUITS.......................................................................................[1-38]
1.8.1 Need for gate or base drive circuits.................................................................................................................[1-38]
1.8.2 Isolation techniques............................................................................................................................................[1-38]
1.8.3 Base drive circuits for power BJT ...................................................................................................................[1-39]
1.8.3.1 Isolated BJT base drive circuit .................................................................................................[1-42]
1.8.3.2 Numericals ...................................................................................................................................[1-42]
1.8.4 Gate drive circuit for power MOSFET / IGBT ..............................................................................................[1-43]
1.9 SILICON CONTROLLED RECTIFIER (SCR)...................................................................[1-44]
1.9.1 Construction [1-44]
1.9.2 Operation of SCR................................................................................................................................................[1-45]
1.9.3 Steady state characteristics ...............................................................................................................................[1-46]
1.9.4 Two transistor analogy......................................................................................................................................[1-48]
1.9.5 Switching characteristics...................................................................................................................................[1-50]
1.9.5.1 Turn – on – Mechanism.............................................................................................................[1-50]
1.9.5.2 Dynamic turn – on characteristics ...........................................................................................[1-52]
1.9.5.3 Turn off mechanism...................................................................................................................[1-53]
1.9.5.4 Turn off characteristics..............................................................................................................[1-53]
1.9.6 SCR ratings ..........................................................................................................................................................[1-54]
1.9.6.1 Voltage ratings ............................................................................................................................[1-56]
1.9.6.2 Current ratings.............................................................................................................................[1-57]
1.9.6.3 Power ratings...............................................................................................................................[1-59]

6. Table of contents v
1.9.6.4 Temperature ratings ...................................................................................................................[1-60]
1.9.7 Gate characteristics ............................................................................................................................................[1-60]
1.9.8 Triggering requirements ....................................................................................................................................[1-64]
1.9.9 Triggering techniques ........................................................................................................................................[1-64]
1.9.9.1 Resistance firing circuit.............................................................................................................[1-64]
1.9.9.2 Resistance capacitance firing circuit .......................................................................................[1-66]
1.9.10 Isolation techniques............................................................................................................................................[1-69]
1.9.10.1 Pulse transformer........................................................................................................................[1-69]
1.9.10.2 Integral cycle triggering or burst triggering ...........................................................................[1-71]
1.10 TRIAC..................................................................................................................................[1-73]
1.10.1 Construction.....................................................................................................................................................[1-73]
1.10.2 Operation ..........................................................................................................................................................[1-74]
1.10.3 Triggering modes ............................................................................................................................................[1-74]
1.10.4 Steady – state characteristics.........................................................................................................................[1-76]
1.10.5 Application of TRIAC.....................................................................................................................................[1-77]
1.10.6 Advantages and Disadvantages of TRIACs ................................................................................................[1-77]
1.10.7 Ratings of TRIAC ............................................................................................................................................[1-78]
1.11 MOS CONTROLLED THYRISTORS (MCT).....................................................................[1-78]
1.11.1 Turn on process ...............................................................................................................................................[1-79]
1.11.2 Turn-off process ..............................................................................................................................................[1-80]
1.11.3 Ratings of MCT ...............................................................................................................................................[1-80]
1.12 GATE TURN OFF THYRISTOR (GTO).............................................................................[1-81]
1.12.1 Construction.....................................................................................................................................................[1-82]
1.12.2 Operation ..........................................................................................................................................................[1-83]
1.12.3 Turn off mechanismof GTO.........................................................................................................................[1-83]
1.12.4 Applications of GTO ......................................................................................................................................[1-84]
1.12.5 GTO characteristics.........................................................................................................................................[1-84]
1.12.6 Ratings of GTO................................................................................................................................................[1-85]
1.13 LIGHT ACTIVATED SILICON-CONTROLLED RECTIFIERS (LASCR)........................[1-88]
1.13.1 Applications .....................................................................................................................................................[1-89]
1.13.2 Ratings of LASCR ...........................................................................................................................................[1-89]
1.14 COMPARISON TABLES....................................................................................................[1-91]
1.14.1 Comparison between IGBTs and MOSFETs ..............................................................................................[1-91]
1.14.2 Comparison between SCR and BJT..............................................................................................................[1-91]
1.14.3 Comparison between BJT and power MOSFET........................................................................................[1-92]
1.14.4 Comparison between power MOSFET and Thyristors.............................................................................[1-92]
1.14.5 Comparison between SCR and TRIAC ........................................................................................................[1-93]
1.14.6 Comparison between the SCR, BJT, MOSFET and IGBT........................................................................[1-93]
1.14.7 Comparison between GTO and Thyristor...................................................................................................[1-93]

7. Table of contentsvi
1.14.8 Comparison of various power devices.........................................................................................................[1-94]
1.15 DIAC....................................................................................................................................[1-95]
1.15.1 Principle of DIAC............................................................................................................................................[1-95]
1.15.2 Phase control using DIAC – TRIAC .............................................................................................................[1-97]
1.16 SILICON UNILATERAL SWITCH (SUS)..........................................................................[1-97]
1.16.1 V-I characteristic of SUS................................................................................................................................[1-98]
1.16.2 SUS Characteristics.........................................................................................................................................[1-98]
1.16.3 Ratings of SUS.................................................................................................................................................[1-99]
1.16.4 Applications of SUS........................................................................................................................................[1-99]
1.17 TRIGGERING USING ICs (IC 785)....................................................................................[1-99]
1.18 UNIJUNCTION TRANSISTOR (UJT)..............................................................................[1-101]
1.18.1 Construction...................................................................................................................................................[1-101]
1.18.2 Equivalent circuit of UJT.............................................................................................................................[1-103]
1.18.3 Characteristics of UJT..................................................................................................................................[1-104]
1.18.4 UJT relaxation oscillator..............................................................................................................................[1-105]
1.18.5 UJT relaxation oscillator for pulse outputs...............................................................................................[1-106]
1.18.6 Triggering using UJT ...................................................................................................................................[1-107]
1.18.7 Phase control using pedestal and ramp triggering ...................................................................................[1-108]
1.19 PROGRAMMABLE UNIJUNCTION TRANSISTOR (PUT)............................................[1-110]
1.19.1 PUT relaxation oscillator.................................................................................................................................[1-111]
1.19.2 Advantages of the PUT.....................................................................................................................................[1-112]
1.20 CLASSIFICATION OF FORCED COMMUTATION METHODS...................................[1-114]
1.20.1 Class A: self commutated by resonating the load....................................................................................[1-114]
1.20.2 Class B - self commutation by an LC circuit ..............................................................................................[1-116]
1.20.3 Class C - complimentary voltage commutation..........................................................................................[1-118]
1.20.4 Class D – auxiliary voltage commutation .................................................................................................[1-120]
1.20.5 Class E – external pulse source for commutation....................................................................................[1-124]
1.20.6 Class F commutation: (Line commutation) ..............................................................................................[1-125]
1.20.7 Auxiliary current commutation (Class D).................................................................................................[1-126]
1.21 OVERVOLTAGE PROTECTION.....................................................................................[1-128]
1.21.1 Snubber circuits dv/dt suppression.............................................................................................................[1-128]
1.21.2 Non-linear surge suppressors......................................................................................................................[1-132]
1.21.3 Crowbar Circuits ...........................................................................................................................................[1-134]
1.22 OVERCURRENT PROTECTION.....................................................................................[1-134]
1.22.1 Fuse SCR co-ordination in A.C. circuits....................................................................................................[1-136]
1.22.2 Fuses in D.C. circuits....................................................................................................................................[1-137]
1.22.3 Complete protection of converter[ ..............................................................................................................1-137]
1.23 di/dt PROTECTION...........................................................................................................[1-138]
1.24 dv/dt PROTECTION ..........................................................................................................[1-139]

8. Table of contents vii
Review Questions...........................................................................................................................................................[1-140]
2 THYRISTOR APPLICATIONS .............................................[2-1 to 2-78]
2.1 INTRODUCTION..................................................................................................................[2-1]
2.2 PHASE CONTROLLED RECTIFIERS (AC – DC CONVERTER).......................................[2-2]
2.2.1 Concept of line and forced commutation .........................................................................................................[2-2]
2.2.2 Classification of rectifiers ...................................................................................................................................[2-2]
2.2.3 Classification of phase controlled converters..................................................................................................[2-3]
2.2.4 Principle of phase controlled converter operation..........................................................................................[2-7]
2.2.5 Single phase half wave converter with R - L load.........................................................................................[2-10]
2.2.6 Effect of free wheeling diode (Df)...................................................................................................................[2-12]
2.2.7 Single phase full converter for R load.............................................................................................................[2-14]
2.2.8 Single phase fully controlled bridge circuit with (R - L) load ....................................................................[2-16]
2.2.9 Single phase semi converter .............................................................................................................................[2-22]
2.2.9.1 Half controlled bridge rectifier with R load...........................................................................[2-22]
2.2.10 Half controlled bridge rectifier with R - L load.............................................................................................[2-24]
2.2.11 Free wheeling action in semi converter ..........................................................................................................[2-29]
2.2.12 Advantages of half controlled converter over full control converter circuit ............................................[2-29]
2.2.13 Comparison between full converter and semi converter..............................................................................[2-29]
2.3 THREE PHASE SYSTEM...................................................................................................[2-35]
2.3.1 Line and phase voltage and currents in three phase delta connection.......................................................[2-37]
2.3.2 Line and phase voltages and currents in three phases star connection......................................................[2-38]
2.3.3 Power in three phase balanced system............................................................................................................[2-40]
2.3.4 Three phase full converter for resistive (R) load...........................................................................................[2-41]
2.3.5 Detailed operation with ‘R’ load for = 30 .................................................................................................[2-48]
2.3.6 Three phase semi converter for resistive load ...............................................................................................[2-48]
2.4 A.C. VOLTAGE CONTROLLER........................................................................................[2-54]
2.4.1 Single phase bidirectional (full wave) a.c. voltage controller ....................................................................[2-55]
2.4.2 Single phase a.c. voltage controller with resistive (R) load ........................................................................[2-56]
2.4.3 Single phase a.c. voltage controller with inductive (R - L) load ................................................................[2-58]
2.4.4 Three phase a.c. voltage controller for ‘R’ load (Star connected regulator) ............................................[2-65]
2.4.5 Three phase bidirectional delta connected regulator....................................................................................[2-69]
2.5 SCR – UJT OPERATED D.C. CIRCUIT..............................................................................[2-71]
2.6 AC power control using SCR – UJT......................................................................................[2-72]
2.7 A.C. POWER CIRCUIT OF A UNIVERSAL SPEED CONTROLLER FAN REGULATOR[2-73]
2.8 PHASE CONTROL USING TRIAC.....................................................................................[2-75]
Review Questions..............................................................................................................................................................[2-77]
3 INVERTERS.............................................................................[3-1 to 3-72]

9. Table of contentsviii
3.1 INTRODUCTION..................................................................................................................[3-1]
3.2 THYRISTOR INVERTER CLASSIFICATION ....................................................................[3-2]
3.2.1 Classification according to the method of commutation ...............................................................................[3-2]
3.2.2 Classifications according to connections..........................................................................................................[3-3]
3.3 SERIES INVERTERS .....................................................................................................................................................[3-3]
3.3.1 Basic series inverter .............................................................................................................................................[3-3]
3.3.2 Circuit analysis......................................................................................................................................................[3-6]
3.3.3 Design aspects.......................................................................................................................................................[3-8]
3.3.4 Modified series inverter.......................................................................................................................................[3-9]
3.3.5 Three phase series inverter................................................................................................................................[3-11]
3.3.6 High frequency series inverter .........................................................................................................................[3-12]
3.4 PARALLEL INVERTER.....................................................................................................[3-13]
3.4.1 Basic parallel inverter ........................................................................................................................................[3-13]
3.4.2 Parallel inverter with feedback diodes............................................................................................................[3-18]
3.5 SINGLE PHASE HALF BRIDGE VOLTAGE SOURCE INVERTERS.............................[3- 21]
3.5.1 Operation with resistive R load........................................................................................................................[3-22]
3.5.2 Operation with RL Load....................................................................................................................................[3-25]
3.6 SINGLE PHASE FULL BRIDGE INVERTER....................................................................[3-28]
3.6.1 Operation with resistive load............................................................................................................................[3-28]
3.6.2 Operation with RL load .....................................................................................................................................[3-31]
3.7 THREE PHASE BRIDGE INVERTERS.................................................................[3-34]
3.7.1 Comparison between the two conduction modes..........................................................................................[3-48]
3.8 PULSE - WIDTH MODULATED (PWM) INVERTERS[3-50]
3.8.1 Single pulse modulation ....................................................................................................................................[3-50]
3.8.2 Multiple pulse modulation ................................................................................................................................[3-52]
3.8.3 Sinusoidal pulse modulation (SPWM) ............................................................................................................[3-55]
3.8.4 Realization of PWM in single phase bridge inverters ..................................................................................[3-57]
3.9 Basic circuit schemes of IGBT/MOSFET based inverter.......................................................[3-60]
3.10 RESONANT CONVERTERS..............................................................................................[3-63]
3.10.1 Zero current switching (ZCS) resonant converters .......................................................................................[3-63]
3.10.1.1 L-Type ZCS resonant converter ...............................................................................................[3-64]
3.10.1.2 M - Type ZCS Resonant Converter .........................................................................................[3-66]
3.10.2 Zero voltage switching (ZVS) resonant converters.......................................................................................[3-68]
3.11 COMPARISONS BETWEEN ZCS AND ZVS RESONANT CONVERTERS......................[3-70]
Review Questions..............................................................................................................................................................[3-71]
4 CHOPPERS...............................................................................[4-1 to 4-42]
4.1 INTRODUCTION..................................................................................................................[4-1]
4.2 BASIC CHOPPER CLASSIFICATION.................................................................................[4-2]

10. Table of contents ix
4.3 STEP DOWN CHOPPER ......................................................................................................[4-3]
4.3.1 Principle of operation of step down chopper with R load .............................................................................[4-3]
4.3.2 Working principle of step down chopper (bulk converter) with RL load ...................................................[4-5]
4.3.3 Step down chopper for RL load (derivation for maximum ripple current).................................................[4-7]
4.3.4 Numericals ...........................................................................................................................................................[4-10]
4.4 STEP UP CHOPPER (BOOST CHOPPER) ........................................................................[4-15]
4.4.1 Numericals ...........................................................................................................................................................[4-17]
4.5 CONTROL STRATEGIES..................................................................................................[4-18]
4.5.1 Numericals ...........................................................................................................................................................[4-24]
4.6 JONES CHOPPER ..............................................................................................................[4-22]
4.6.1 Design considerations........................................................................................................................................[4-23]
4.7 CHOPPER CONTROL OF D.C. SERIES MOTOR.............................................................[4-24]
4.7.1 Circuit analysis....................................................................................................................................................[4-25]
Review Questions..............................................................................................................................................................[4-40]
5 SWITCHED MODE POWER SUPPLIES (SMPS) ..............[5-1 to 5-20]
5.1 INTRODUCTION..................................................................................................................[5-1]
5.2 SWITCHING MODE REGULATORS..................................................................................[5-6]
5.2.1 Buck regulators.......................................................................................................................................................[5-7]
5.2.2 Boost regulators....................................................................................................................................................[5-10]
5.2.3 Buck-Boost regulators .........................................................................................................................................[5-14]
5.3 COMPARISON OF REGULATORS....................................................................................[5-18]
5.4 ADVANTAGES AND DISADVANTAGES..........................................................................[5-18]
Review Questions..............................................................................................................................................................[5-19]
6 DRIVES................................................................................... [6-1 TO 6-72]
6.1 CONCEPT AND REQUIREMENT OF DRIVES ..................................................................[6-1]
6.2 ADVANTAGES OF DRIVES.................................................................................................[6-2]
6.3 PARTS OF ELECTRICAL DRIVES.....................................................................................[6-3]
6.3.1 Electrical Motors ..................................................................................................................................................[6-3]
6.3.2 Power modulators.................................................................................................................................................[6-4]
6.3.3 Sources ...................................................................................................................................................................[6-8]
6.3.4 Control Unit...........................................................................................................................................................[6-9]
6.4 CHOICE OF ELECTRICAL DRIVES..................................................................................[6-9]
6.5 STATUS OF dc AND ac DRIVES..........................................................................................[6-9]
6.6 CONTROL BY AC VOLTAGE CONTROLLERS AND SOFT START..............................[6-10]
6.7 VARIABLE FREQUENCY CONTROL FROM VOLTAGE SOURCES.............................[6-11]
6.7.1 Variable frequency control of an induction motor........................................................................................[6-11]

11. Table of contentsx
6.8 VOLTAGE SOURCE INVERTER (VSI) CONTROL..........................................................[6-13]
6.8.1 VSI induction motor drives ...............................................................................................................................[6-13]
6.9 CYCLOCONVERTER CONTROL.....................................................................................[6-15]
6.10 CLOSED LOOP SPEED CONTROL AND CONVERTER…............................................... [6-16]
6.11 CURRENT SOURCE INVERTER CONTROL...................................................................[6-18]
6.11.1 Regenerative braking and multiquadrant operation ........................................................................................[6-19]
6.11.2 Closed loop speed control of CSI drives ...........................................................................................................[6-19]
6.11.3 Comparison of current source inverter (CSI) and voltage source inverter (VSI) drives ...........................[6-20]
6.12 CURRENT REGULATED VOLTAGE SOURCE INVERTER CONTROL........................[6-20]
6.13 VARIABLE FREQUENCY DRIVE (VFD) FUNDAMENTALS..........................................[6-22]
6.13.1 AC motor speed...................................................................................................................................................[6-22]
6.13.2 Voltage and frequency relationship.................................................................................................................[6-23]
6.13.3 VFD speed torque characteristics ....................................................................................................................[6-23]
6.13.4 Variable frequency drive (VFD) output module ...........................................................................................[6-24]
6.13.5 Inverter principles...............................................................................................................................................[6-25]
6.13.6 Output switching sequence...............................................................................................................................[6-25]
6.13.7 VFD three-phase waveform..............................................................................................................................[6-26]
6.13.8 Pulse width modulation .....................................................................................................................................[6-27]
6.14 dc MOTORS AND THEIR PERFORMANCE.....................................................................[6-27]
6.15 METHODS OF MOTOR CONTROL USING.....................................................................[6-29]
6.16 METHODS OF ARMATURE VOLTAGE CONTROL.......................................................[6-30]
6.17 WARD LEONARD DRIVES ...............................................................................................[6-31]
6.18 TRANSFORMER AND UNCONTROLLED RECTIFIER CONTROL ..............................[6-34]
6.19 CONTROLLED RECTIFIER FED dc DRIVES..................................................................[6-35]
6.19.1 Single phase fully controlled rectifier control of dc separately excited motor...........................................[6-36]
6.19.2 Single phase half controlled rectifier control of dc separately excited motor ............................................[6-37]
6.19.3 Three phase fully controlled rectifier control of dc separately excited motor .........................................[6-37]
6.19.4 Three phase half controlled rectifier control of dc separately excited motor...........................................[6-39]
6.20 RECTIFIER CONTROL OF dc SERIES MOTOR..............................................................[6-39]
6.21 CHOPPER-CONTROLLED dc DRIVES.............................................................................[6-41]
6.22 CHOPPER CONTROL OF SEPARATELY EXCITED dc MOTOR...................................[6-41]
6.22.1 Control of motoring............................................................................................................................................[6-41]
6.22.2 Regenerative braking .........................................................................................................................................[6-42]
6.22.3 Motoring and Regenerative Braking ...............................................................................................................[6-42]
6.22.4 Dynamic Braking................................................................................................................................................[6-44]
6.23 CHOPPER CONTROL OF SERIES MOTOR.....................................................................[6-45]
6.24 SINGLE PHASE SCR DRIVE..............................................................................................[6-45]
6.24.1 Single phase half wave converter drives ........................................................................................................[6-47]

12. Table of contents xi
6.24.2 Single phase semi converter drives .................................................................................................................[6-48]
6.24.3 Single phase full converter drives....................................................................................................................[6-49]
6.24.4 Single phase dual converter drives ..................................................................................................................[6-50]
6.25 THREE PHASE SCR DRIVE..............................................................................................[6-51]
6.25.1 Three phase half wave converter drives .........................................................................................................[6-51]
6.25.2 Three phase semi converter drives ..................................................................................................................[6-52]
6.25.3 Three phase full converter drives.....................................................................................................................[6-52]
6.25.4 Three phase dual converter drives ...................................................................................................................[6-53]
6.26 REVERSIBLE SCR DRIVES ..............................................................................................[6-54]
6.26.1 Single fully controlled rectifier with a reversing switch ................................................................................[6-54]
6.26.2 Dual converter[6-55]
6.26.3 Field current reversal............................................................................................................................................[6-56]
6.27 CLOSED LOOP CONTROL SYSTEM ...............................................................................[6-57]
6.27.1 Open loop transfer function..............................................................................................................................[6-57]
6.27.2 Closed loop transfer function ...........................................................................................................................[6-61]
6.27.3 Phase locked loop control.................................................................................................................................[6-64]
6.27.4 Microcomputer control of d.c. drives..............................................................................................................[6-65]
6.28 BRUSHLESS dc MOTOR DRIVES.....................................................................................[6-66]
6.28.1 Brushless dc motor drive for servo applications ...........................................................................................[6-67]
6.28.2 Low cost brushless dc motor drives...................................................................................................................[6-70]
6.28.3 Important features and applications ...................................................................................................................[6-71]
Review Questions..............................................................................................................................................................[6-72]
7 INDUSTRIAL APPLICATIONS ............................................[7-1 to 7-28]
7.1 INTRODUCTION..................................................................................................................[7-1]
7.2 RESISTANCE HEATING .....................................................................................................[7-2]
7.3 INDUCTION HEATING .......................................................................................................[7-3]
7.3.1 High frequency power source for induction heating ......................................................................................[7-6]
7.3.2 Oscillator circuit used in induction heaters......................................................................................................[7-6]
7.3.3 Spark gap generator..............................................................................................................................................[7-7]
7.3.4 Mercury Arc converters.......................................................................................................................................[7-9]
7.3.5 Motor Generator sets............................................................................................................................................[7-9]
7.4 ELECTRONIC HEATERS EMPLOYED FOR INDUCTION HEATING.............................[7-9]
7.4.1 Static generators (or converters) used for high frequency induction heating...........................................[7-14]
7.4.2 Double hybrid type static converters...............................................................................................................[7-15]
7.4.2.1 Power section ..............................................................................................................................[7-15]
7.4.2.2 Control section............................................................................................................................[7-15]
7.4.2.3 Input section................................................................................................................................[7-16]
7.4.2.4 Rectifier section..........................................................................................................................[7-16]

13. Table of contentsxii
7.4.2.5 Inverter section............................................................................................................................[7-16]
7.4.2.6 Compensation section................................................................................................................[7-16]
7.5 THYRISTORISED SUPPLIES USED IN INDUCTION FURNACES.................................[7-17]
7.6 ADVANTAGES OF INDUCTION HEATING.....................................................................[7-18]
7.7 APPLICATIONS OF INDUCTION HEATING...................................................................[7-18]
7.8 DIELECTRIC HEATING....................................................................................................[7-18]
7.9 APPLICATIONS OF DIELECTRIC HEATING.................................................................[7-22]
7.10 TEMPERATURE CONTROL.............................................................................................[7-22]
7.10.1 Automatic Temperature Controller Using IC 741 ........................................................................................[7-23]
7.10.2 Phase control circuits for regulating temperature ............................................................................................[7-25]
7.10.3 Remote temperature controller ...........................................................................................................................[7-25]
Review Questions..............................................................................................................................................................[7-26]
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14. xiii
Preface
For making the application compact, cost effective and low power consumption is demanding the Power Electronics
and Electrical Machines in every field to evolve in the technology day by day and it is a great challenge for the instrument
engineer to make use of various technologies simultaneously. For this purpose, the students should be aware of some
basics of Electronics engineering related technology. Different types of components, devices, their applications with
examples should be known. For designing purposes, the knowledge of different types of electronic terms used must be
familiar. This book gives the basics of those devices and electrical drives useful for the applications and designing the
Electronic and Electrical systems.
This book is an introductory text to the theory and practice of power electronics and electrical drives. This book is
the outcome of notes written during our curriculum.
The book is specially written for third year students of Instrumentation and control engineering. However, it should
prove suitable for other branches of engineering which include Power Electronics and Electrical Drives as one of their
subjects.
Thus it is hoped that the following aspects will emerge after studying this book:
1. Power devices and Electrical drives are the subject of study with its own intricacies and challenges. It is intimately
related to Electronics and Electrical science and practice, and as such it is not the degenerate child of any other
branch of engineering.
2. The design of electronic devices and systems is not a mathematical problem, but should be perceived as an
engineering task, with all its attractive challenges and practical shortcomings.
3. A good understanding of physical and electrical phenomena taking place in a devices and circuits is of paramount
importance for the design of simple and effective electronic design schemes.
4. Several alternative circuit configurations are usually possible for a given product or unit or a complete electronic
system. The selection of the "best" among themis the central question to be resolved.
5. There exist a plethora of electronics and simulation tools and design methodologies that one should be familiar with
before attempting to tackle electronic and electrical design problems.
The book begins with……
Chapter-1 covers various power devices like power diodes, power BJT, power MOSFET, SIT, IGBT. SCR, TRIAC,
MCT, GTO and LASCR. Various triggering devices DIAC, SUS, 585, UJT and PUT and various circuit protection
scheme.
Chapter-2 deepens the study of thyristors with their applications in DC and AC power control. Different design circuits
using SCR UJT,TRAIC,DIAC,
Chapter-3 describes various types of inverters using above power devices.
Chapter-4 discusses different choppercircuits for different applications.
Chapter-5 gives applications of power devices in various types of power supplies and their basics.
Chapter-6 covers the concepts of electrical drives like AC and DC drives and their modern controls.
Finally ,Chapter-7 finishes with the industrial power electronics and applications.
INTENDED READERSHIP
The book is specially written for the students of T.E. Instrumentation and control engineering university course. It is also
seen as being of value to students of MSc, BSc, Electronics and telecommunications, information technology, computer
engineering, Electronic Science and Instrumentation Science. It can also be used by senior students and practicing
engineers in the broad field of Control Systems and instrumentation technology.
BACKGROUND KNOWLEDGE ASSUMED
A prerequisite for using this book is basic knowledge of electronics covered in the previous curriculum in the
Instrumentation Engineering course.
A basic knowledge of science and mathematics has been assumed. The science required is basic physical science. Key
elements of science are developed in appropriate chapters. The mathematics required is just the ability to handle the
numbers, integration, summation, interpret graphs and in a few instances, handle simple algebraic equatio n. Knowledge
of the subject of biology at Xth
and XIIth
class level would be very useful, although not absolutely essential.
- Chinttan N. Dewalia

15. xiv
Acknowledgements
Even effort has been made to give credit where it is due for the material contained herein. If inadvertently we have
omitted giving credit, future publications will give due credit to those that are brought to the author’s attention.
I am vastly indebted to many people who have helped and inspired me, in various ways, to start, continue, and
complete this book. I cannot find words to describe the debt I owe to all of my colleagues at various colleges in Pune and
Mumbai University for having created a stimulating atmosphere of academic excellence, the basic element of any long-
lasting endeavor.
My wife Bhaktti and staff of my company typed the original manuscript with great care, artistic taste, skill, and
dedication, unparalleled in my own experience.
With my ongoing publishing activity after Industrial data communications, another new and challenging subject for
which I have authored this book. As a publisher, whatever I amexpecting fromthe author, I have considered all the points
while writing the book.
Many thanks to all the faculty members & teachers in various colleges in Mumbai & Pune University & those who
supported & encouraged me to publish the various useful & needful books. The books that are bridging the gap of
contents & simplification between reference materials & applied curriculum of engineering course in Mumbai & Pune
University which will further conform to all the curriculums in Indian Universities. This book is the outcome of eight
years of of Publishing experience and own technical background. The suggestions fromall side will be very helpful to the
future reader and students of this subject because the intention is that to have a standard book for this subject. Thanks to
all the students for encouraging me to publish this book.
Unfortunately, sources were not always noted or available; hence, it became impractical to provid e an accurate
acknowledgement. Regardless of the source, I wish to express my gratitude to those who may have contributed to this
work, even though anonymously.
- Mr.Chinttan N. Dewalia
D.I.E., B. E. Instrumentation Engg.
(Dr.D.Y.Patil College of Engg., Pune University)
Typesetting, editing and art:
Mrs. Bhaktti C. Dewalia

16. xv
To my wife Bhaktti

17. xvi
ROADMAP TO THE SYLLABUS
(In accordance with the university revised syllabus for T.E. Instrumentation and control Engineering)
1. POWER SEMICONDUCTOR DEVICES: a) Introduction to construction, characteristics, ratings, data sheets and
applications of power diodes, power BJT, power MOSFET, SIT and IGBT. b) Study of Thyristors: constructions,
characteristics, ratings of SCR, TRIAC, MCT, GTO and LASCR. c) Comparison and selection criteria for above
devices. d) Switching / triggering method: Switching methods/ types of triggering, triggering devices DIAC, SUS,
TCA 785, UJT and PUT. e) Thyristors Commutation Techniques. f) Protection Scheme against over-current, over-
voltage, dv/dt and di/dt.
Go to Chapter 1 Power SemiconductorDevices
2. THYRISTOR APPLICATIONS: a) Controlled rectifiers: Principles of operations of phase controlled converters,
single phase half bridge, semi converter and bridge converters. Design of SCR based DC power circuits including
UJT as triggering device and application. b) AC power control using SCR-UJT and TRIAC-DIAC like universal
speed controller fan regulator. Design of SCR/TRIAC based AC power control circuits including UJT/DIAC as a
triggering device.
Go to Chapter 2 ThyristorApplications
3. INVERTERS: Principles of operation of inverters, PWM inverter, series and parallel inverters, bridge inverter, basic
circuit scheme of IGBT/Power MOSFET based inverter circuits. Suitability in different applications of different
capacities and frequencies operation. Principle of ZVC/ZCS resonant converters.
Go to Chapter 3 Inverters
4. CHOPPERS: Basic operation of choppers, study of different types of simple chopper circuits like step up choppers,
step down choppers and Jones chopper, DC motor speed control application using chopper.
Go to Chapter 4 Choppers
5 SWITCH MODE POWER SUPPLIES: Basic concept schemes, Working principles of Buck, Boost, Buck-Boost
converter merits and demerits and applications.
Go to Chapter 5 Switch Mode Power Supplies
6 DRIVES: a) AC Motor Drives: Concept and requirement of drives, Current fed and voltage fed drives, PWM
technique (using IGBT/BJT) for control. b) DC Motor Drives: DC drives for brushed/brushless motors, methods of
motor control using constant voltage and constant current techniques.
Go to Chapter 6 Drives
7 INDUSTRIAL APPLICATIONS: a.)Induction and Dielectric heating process, Block diagram, Merits/demerits and
applications. b.) Temperature controller using thyristor principle and circuit scheme.
Go to Chapter 7 Industrial Applications

18. xvii