POWER ELECTRONICS Dr. PS. BIMBHRA Ph.D., ME. (Hons.), RLE. (india), M.LS.TE., MLEE. (W.K,) Professor & Head of Electrical and Electronics Engineering Department Thapar Institute of Engineering and Technology PATIALA-147001 With the Assistance of : Mrs. Surinder Kaur ny e@ THROUGHLY REVISED AND ENLARGED EDITION 8 KHANNA PUBLISHERS # 2.B NATH MARKET, NAI SARAK ‘3 EBLease DELHI-110006 Phones : 391 23 80 ; 722 41 79 @ Fax : 3980311 Published by : Romesh Chander Khanna, for, KHANNA PUBLISHERS 2-B, Nath Market, Nai Sarak Delhi-110006. All Rights Reserved [This book or part thereof cannot be translated or reproduced in any form (except for review or criticism) without the written permission of the Author and the Publishers] ISBN No. : 81-7409-056-8 Third Edition : 1999, Novernber Sixth Reprint : 2002 Price : Rs. 150/- Computer Typeset at : Softserve Computer Systems Phone : 2462423 Printed at: RAHEEL NASEEM PRINTING PRESS, Dabi-110002 PREFACE The advent of thyristors has revolutionized the art of electric power conversion and its con- trol. Many more semiconductor devices such as triacs, asymmetrical thyristors, gate-turn-off. thyristors, power MOSFET, insulated gate bipolar transistor and MOS-controlled thyristors are now available. The use of these semiconductor devices has pervaded the industrial applications relating to the field of Electrical, Electronics, Instrumentation and Control Engineering. In other words, power-electronic components find their use in low as well as high power applications. The purpose of this book is to provide a good understanding of the power-electronic components and the behaviour of power-electronic controllers by presenting systematically all important aspects of semiconductor devices and the common types of electric power controllers. The book begins with the study of salient features of power diodes, power transistors, MOS-controlled thyristor and other members of thyristor family. Then their applications in the different types of power converter configurations are presented in a lucid detail. This book is intended to serve as an introductory course to the undergraduate students of Electrical, Electronics, Instrumentation and control disciplines. It is presumed that the reader is familiar with the basics of elementary electronics and circuit theory. The material presented here can be covered in one semester with the omission of some topics. The instructor, after browsing through the book for some time, can plan the course contents and its sequence without loss of continuity. The book contains twelve chapters. Chapter 1 gives an overview of merits and demerits of power-electric controllers and briefly discusses the topics covered in this book. This chapter also touches upon the significance of power electronics. Chapter 2 describes the characteristics of power diodes, power transistors and MOS-controlled thyristor. In Chapter 3 are presented diode circuits and rectifiers. Chapter 4 explains the characteristics of thyristors in detail and of triacs, GTOs etc. in brief. Thyristor commutation techniques are given in Chapter 5. In Chapter 6, the principles of conversion from ac to de involving single-phase as well as three-phase converters are presented. Chapters 7 to 10 pertain to the treatment of de choppers, inverters, ac voltage controllers and cycloconverters respectively. While chapter 11 gives study of several applications of power electronics, Chapter 12 discusses electric drives. A large number of illustrative diagrams and a wide variety of worked examples add to the clarity of the subject matter. The material given in this book is class-room tested. In the appendix, large number of objective-type questions relat- ing to Chapter 2 to 10 are given. The material added in the present edition includes Chapter 11 and Chapter 12. Some topics have been re-written to make the presentation more lucid. Many more illustrative examples to reinforce the understanding of the subject matter are also included. It is hoped that the book in its present form will serve the purpose of students for the courses on Power Electronics of all Indian Universities. The author is grateful to all those students who interacted with the author, in the class-room or outside, during the teaching of this subject. This interaction has greatly influenced the author’s style of teaching and writing to a great extent and every effort has gone into making the subject matter presentation as easily comprehensible as possible. Finally, the author expresses his gratitude to his wife for her perennial encouragement, un- derstanding and patience during the preparation of this book. The author also places on record the assistance rendered by his two sons during the gruelling task of proof-reading. Suggestions leading to the improvement of the book will be gratefully acknowledged. Patiala Dr. PS. Bimbhra 14th November, 1999 1. INTRODUCTION 2.0... cece cree eee eee ee meee teens 1.1. Concept of Power Electronics ......----+-45 : 1.2. Applications of Power Electronics 1.3. Advantages and Disadvantages of Power-Electronic Converters 1.4. Power Electronic Systems .. 1... eee ee 1.5. Power Semiconductor Devices... . . 1.6. Types of Power Electronic Converters . . 1.7. Power Electronic Modules... 2.0 ee ee ee 2. POWER SEMICONDUCTOR DIODES AND TRANSISTORS ..........-.+.- 7-32 2.1. Characteristics of Power Diodes 2.066 0 ee 2.1.1. Diode V-I Characteristics . . . . 2.1.2, Diode Reverse Recovery Characteristics 2.2. Types of Power Diodes 2.6... eee ee eee 2.2.1. General-purpose Diodes 2.2.2. Fast-recovery Dicdes ...... 2.2.3. Schottky Diodes .....-.5- 2.3. Power Transistors . 20-6. ee ee eee 2.3.1. Bipolar Junction Transistors .. 6... ee ee ee 2.3.1.1. Steady-state Characteristics. 2.3.1.2. Transistor Switching Performance... 2.2... 0 ee ee “4 2.3.1.8. Safe Operating Area... 6 es tad 2.4. Power MOSFETS.......-----55 2.4.1. MOSFET Characteristics .........---- 2.4.2. Comparison of MOSFET with BJT 2.5. Insulated Gate Bipolar Transistor (IGBT) 2.5.1, Basic Structure and Working 2.5.2, LGBT Characteristics ....... 2.5.3. Switching Characteristics ©... ee ee 2.5.4, Applications of IGBT . 2... eee 2.6. Mos-controlied Thyristor (MCT)... .. - . 2.7. New Semiconducting Materials 2.6... ee 3. DIODE CIRCUITS AND RECTIFIERS... ..--.- 565 3.1. Diode Circuits with DC Source 3.1.1. Resistive Load... 3.1.2, RC Load ....... 3.1.3. RL Load ....... 3.1.4, LC Load 3.1.5. RLC Load 3.2. Freewheeling Diodes 3.3. Diode and L-Circuit 3.4. Recovery of Trapped Energy... ..-.- +--+ 2s 04 3.5. Single-phase Diode Rectifiers 3.5.1. Single-phase Half-wave Rectifier . se 3.6. Zener Diodes . 2... (viii) + 4. THYRISTORS 2... 06. eee rece eee te ee eee wee ee ns G21EY 4.1. 4.2. 4.3. 4.4, 45. 4.6. 4.7. 4.8. 4.9, 4.10. 4.11. 4,12. 4.13. 4.14, 4,15, 4.16. Terminal Characteristics of Thyristors ............. 4.1.1. Static V-I Characteristics of a Thyristor Thyristor Turn-on Methods ......-.-------505. Switching Characteristics of Thyristors ........... 4.3.1, Switching Characteristics during Turn-on ... .. 4.3.2. Switching Characteristics During Turn-off ... . . Thyristor Gate Characteristics ©... ..05------- . Two-transiste~ Model of a Thyristor ... . Thyristor Ratings... .......0..-4- 4.6.1. Anode Voltage Ratings . : 4.6.2. Current Ratings... 0 ..0..0..-0 00005 . Thyristor Protection 2... eee ee eee . 4.7.1. Design of Snubber Circuits 4.7.2, Overvoltage Protection 2.0. 0. ee 4.7.2.1. Suppression of Overvoltages. ©... 0 21. ee 99 4.7.3, Overcurrent Protection... 6 ee eee 100 4.7.4, Gate Protection 2.00. ee ee ee 101 Heating, Cooling and Mounting of Thyristors . wee 108 4.8.1, Thermal Resistance... 6 ee ee eee 104 4.8.2. Heat Sink Specifications ©... 0. 0. ee 105 4.8.3. Thyristor Mounting Techniques . . : woe. 106 Series and Parallel Operation of Thyristors ... 2... 2.2... 2.000000 000. 110 4.9.1. Series Operation. ©... 6 ee 4.9.2. Parallel Operation. ......... Other Members of the Thyristor Family . 4.10.1, PUT (Programmable Unijunction Transistor) 4.10.2. SUS (Silicon Unilateral Switch) 4.10.3. SCS (Silicon Controlled Switch) . . wee 4.10.4, Light Activated Thyristors .........---- 4.10.5. Static Induction Thyristors (SITHs)........ 4.10.6. The Diac (Bidirectional Thyristor Diode) 4.10.7. The Triac. 2. ee ee 4.10.8. Asymmetrical Thyristor (ASCR) ... . 4.10.9. Reverse Conducting Thyristor (RCT) 4.10.10. Other Thyristor Devices tee Gate Turn Off (G.T.O.) Thyristor 6... ee eee 4.11.1. Static V-I Characteristics of GTOs 4.11.2. Switching Performance... ... - tae tee Firing Circuits for Thyristors .. 1... 06-0 es 4.12.1. Main Features of Firing Circuits 2... 0. ee 4.12.2. Resistance and Resistance-Capacitance Firing Circuits... . . 4.12.3, Unijunction Transistor (UJT) Pulse Transformer in Firing Circuits Triac Firing Cirevnit..........00.-.. Gating Circuits for Single-phase Converters 4.15.1. Gate Pulse Amplifiers 4.15.2. Pulse Train Gating . . be ee Cosine Firing Scheme 2.1... 0. ce ee eee (ix) 6. THYRISTOR COMMUTATION TECHNIQUES . eee cere eee eeeces =» 160-174 5.1. Class A Commutation : Load Commutation... 6... 0 eee ee eee 160 5.2. Class B Commutation : Resonant-Pulse Commutation .........----5--: 162 5.3. Class C Commutation ; Complementary Commutation...........----5> 165 5.4, Class D Commutation : Impulse Commutation .... 6.6.26 ous rn 167 5.5. Class E Commutation : External Pulse Commutation .....-..--5.-5--- 169 5.6. Class F Commutation : Line Commutation ...... 0-0 sree eects 170 6. PHASE CONTROLLED RECTIFIERS . wee e eee reece cere nee LIRA 6.1. Principle of Phase Control... 6 0. ee et te 176 6.1.1. Single-phase Half-wave Circuit With RL Load... 1... 2-2 178 6.1.2. Single-phase Half-wave Circuit With RL Load And Freewheeling Diode . . 180 6.1.3. Single-phase Half-wave Circuit With RLE Load .....---- +--+ +> 182 6.2. Full-wave Controlled Converters 2... 06 eee et te es 187 6.3. Single-phase Full-wave Converters .. 6.60 eee eee es 188 6.3.1. Single-phase Full-wave Mid-point Converter... ...-- +--+ --5--> 189 6.3.2. Single-phase Full-wave Bridge Converters ...-. 6. - +--+ 5-05 191 6.3.2.1. Single-phase Full Converter. 2... 00.0 ee ee et 191 6.3.2.2. Single-phase Semiconverter... 6. 6 0. eee eet 194 6.3.2.3. Analysia of Two-pulse Bridge Converter With Continuous Conduction. 196 6.4, Single-phase Two-pulse Converters with Discontinuous Load Current ........ 200 6.4.1. Single-phase Full Converter With Discontinuous Current .......--- 200 6.4.2. Single-phase Semiconverter With Discontinuous Current ....-...-- 201 6.5. Three-phase Converter Systema using Diodes... .--- +--+ ee eee eee 203 6.6. Three-phase Thyristor Converter Circuits... - 6-2 ee ee 209 6.6.1. Three-phase Full Converters... 2.6.62 - eee ete tee 210 6.6.2. Three-phase Semiconvertera .. 2. - 6-0 ee tee eee ees 214 6.7. Effect of Source Impedance on the Performance of Converters .......--.-- 22t 6.7.1, Single-phase Full Converter ©. 05.0 ee tees 222 6.7.2. Three-phase Full Converter Bridge... . 60ers 224 6.8. Dual Converters 0... 10.0 ee ee 228 6.8.1, Ideal Dual Converter .. . . 6.8.2. Practical Dual Converter . . 6.9. Some Worked Examples... 66 1. ee ee et To 7. CHOPPERS ........-085 wena oe . . 7.1. Principle of Chopper Operation . . . eee 7.2. Control Strategies ©. 00. et ee ees 7.2.1. Constant Frequency System ©... ee ee 250 7.2.2. Variable Frequency System 6... 6 ee ee es 250 7.8. Step-up Choppers... 0.6 te eee 251 7.4, Types of Chopper Circuits ©... 6. ee ee 254 7.4.1, First-quadrant, or Type-A, Chopper... -- 2-2 et eee ee 255 7.4.2. Second-quadrant, or Type-B, Chopper... . - - rr 255 7.4.3. Twb-quadrant Type-a Chopper, or Type-C Chopper ......--..---- 256 7.4.4. Two-quadrant Type-b Chopper, or Type-D Chopper ......---.---- 256 7.4.5. Four-quadrant Chopper, or Type-E Chopper ..-.-. +--+ +--+ 50> 257 7.5, Steady State Time-domain Analysis of Type-A Chopper .......--- 000065 259 7.5.1, Steady State Ripple... 6... ee 263