Principles of Electric Machines with Power Electronic Applications

490 Pages·2002·30.04 MB·English

by  Mohamed E. El-Hawary

PRINCIPLES OF
ELECTRIC MACHINES
WITH POWER
ELECTRONIC
APPLICATIONS
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PRINCIPLES OF
ELECTRIC MACHINES
WITH POWER
ELECTRONIC
APPLICATIONS
Second Edition
MOHAMED E. EL-HAWARY
IEEE Power Engineering Society, Sponsor
PRlEEe•" •
SIR". ..•
PO\NER
ON
ENGINEERING
IEEE Press PowerEngineering Series
Mohamed E. El-Hawary, Series Editor
+
IEEE
PRESS
roWILEY"
~INTERSCIENCE
A JOHN WILEY &SONS, INC., PUBLICATION
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Technical Reviewers
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Copyright :{';2002 byThe Institute ofElectrical and ElectronicsEngineers,Inc. All rights reserved.
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LibraryofCongressCataloging-in-PublicationData isavailable.
El-Hawary,Mohamed,E.
PrinciplesofElectric Machineswith Power ElectronicApplicationsl
Mohamed, E. El-Hawary.
p. em.
Includesbibliographical referencesand index.
ISBN 0-471-20812-4(cloth: alk. paper)
10 9 8 7 6 5 4 3 2 I
CONTENTS
PREFACE ix
Chapter 1 INTRODUCTION 1
1.1 Electric Machines I 1
1.2 Roots in Observation I 2
1.3 Beginnings I 3
1.4 Foundations of Electromagnetism I 5
1.5 The Dawn of Electrodynamics I 7
1.6 Early Electric Generators I 9
1.7 Early Electric Motors I 10
1.8 Alternating Current I 11
1.9 PowerElectronics: Scope and A Brief History I 13
1.10 Structure of the Power System I 18
1.11 Outline of theText I 21
Chapter2 PRINCIPLESOF ELECTROMAGNETISMAND
ELECTROMECHANICAL ENERGYCONVERSION 23
2.1 Introduction I 23
2.2 Magnetic-Field Laws I 24
2.3 Permeability andMagnetic-Field Intensity I 31
2.4 Magnetic Circuits I 35
2.5 Flux Linkages, Induced Voltages,Inductance,andEnergy I 50
v
vi CONTENTS
2.6 Hysteresis Loop / 54
2.7 Eddy-Current and Core Losses / 59
2.8 Energy Flow Approach / 60
2.9 Field Energy / 64
2.10 Multiply Excited Systems / 69
2.1I Reluctance Motors / 72
2.12 Doubly Excited Systems / 75
2.13 Salient-Pole Machines / 77
2.14 Round or Smooth Air-Gap Machines / 80
2.15 Machine-Type Classification / 84
2.16 P-Pole Machines / 85
Problems / 89
Chapter 3 POWERELECTRONIC DEVICES AND SYSTEMS 103
3.1 Introduction / 103
3.2 Power Semiconductor Devices / 103
3.3 Control Characteristics of Power Devices / 106
3.4 Power Semiconductor Diodes / 108
3.5 PowerTransistors / 115
3.6 The Thyristors / 138
3.7 Power Electronic Systems / 175
3.8 Power Integrated Circuits and Smart Power / 178
Problems / 179
Chapter 4 DIRECT-CURRENTMOTORS 183
4.I Introduction / 183
4.2 Construction Features / 184
4.3 Circuit Model of dc Generator / 185
4.4 Circuit Model of dc Motors / 187
4.5 dc Series Motors / 190
4.6 de Shunt Motors / 203
4.7 Compound Motors / 212
4.8 Motor and Load Matching / 224
4.9 Conventional Speed Control of de Motors / 224
4.10 Reversal of Direction of Rotation / 241
4.11 Starting de Motors / 241
4.12 Adjustable Speed de Motor Drives / 251
CONTENTS vii
4.13 ac-dc Drives for de Motors I 255
4.14 de-de Drives for de Motors I 261
Problems I 265
Cha~M5 TRANSFORMERS 273
5.1 Introduction I 273
5.2 Ideal Transformers I 274
5.3 TransformerModels I 278
5.4 TransformerPerformance Measures I 286
5.5 Single-Phase Connections I 292
5.6 Three-WindingTransformers I 296
5.7 Three-Phase Systems and TransformerConnections I 300
5.8 Autotransformers I 313
Problems I 316
Chapter6 INDUCTION MOTORS AND THEIR CONTROL 323
6.1 Introduction I 323
6.2 MMF Waves and the Rotating Magnetic Field I 324
6.3 Slip I 329
6.4 Equivalent Circuits I 331
6.5 SimplifiedEquivalent Circuits I 334
6.6 Torque Characteristics I 338
6.7 Some Useful Relations I 341
6.8 Internal Mechanical Power I 344
6.9 Effects ofRotor Impedance I 348
6.10 Classification ofInduction Motors I 351
6.11 Starting Induction Motors I 354
6.12 Conventional Speed Control ofInduction Motors I 362
6.13 Adjustable Speed Drives: General Considerations I 370
6.14 Variable-Voltage-Constant-Frequency Drives I 372
6.15 Variable-Voltage-Variable-Frequency Drives I 376
6.16 de-Link-Converter Drives I 381
6.17 Voltage-Fed InverterDrives I 383
6.18 Current-Fed InverterDrives I 385
6.19 CycloconverterDrives I 386
6.20 Regulation ofSlip Power I 387
Problems I 389
viii CONTENTS
Chapter 7 SYNCHRONOUS MACHINES 397
7.I Introduction / 397
7.2 Round-Rotor Machines: Equivalent Circuit / 401
7.3 Armature Reaction / 406
7.4 Principal Steady-State Characteristics / 410
7.5 Power Angle Characteristics and the Infinite-Bus Concept / 415
7.6 Synchronous-MotorOperation / 423
7.7 Salient-Pole Machines / 430
Problems. / 437
Chapter 8 FRACTIONAL-HORSEPOWER ALTERNATING
CURRENT MOTORS 443
8.1 Introduction / 443
8.2 Rotating Magnetic Fields in Single-Phase Induction Motors / 443
8.3 Equivalent Circuits for Single-Phase Induction Motors / 448
8.4 Power and Torque Relations / 454
8.5 Starting Single-Phase Induction Motors / 459
Problems / 473
BIBLIOGRAPHY 475
INDEX 477
PREFACE
This book offers an introduction to principles of electric machines and the closely
related area ofpower electronics and adjustable speeddrives.It isdesigned for stu
dents inelectrical andother engineeringdisciplines, aswellasbeing a useful refer
ence andself-study guide for the professional dealing withthis important area. The
coverage of the book is intended to enable its use in a number of ways including
service courses taught to nonelectrical majors. The organization and details ofthe
material allow a maximum flexibilityfortheinstructortoselect topics for inclusion
incourses in the modem engineering curriculum.
This book does not require a level of mathematical sophistication beyond that
given in undergraduate courses in basic physics and introductory electric circuits.
The emphasis incoverage isgiven toanimproved understanding ofthe operational
characteristicsoftheelectric apparatus discussed, onthebasis oflinear mathemati
cal models. Almost everykeyconceptisillustrated throughthe useofin-text exam
ples that are worked out in detail to enforce the reader's understanding. Many
practical problems inelectric machines operation involvethe use of known perfor
mance variables under a given operational condition topredict the same variables
under different operating conditions. These problems canbeeasily dealt with using
thebasic performancecharacteristicstoobtain somecorollaryresultsthat areuseful
forthispurpose. Onmanyoccasions, thistexttakesthetimetoderivesomeofthese
useful relations to allow the student to deal with these common and important
problems.
The firstchapterprovides ahistorical perspectiveonthedevelopment ofelectro
mechanical energy conversion devices andstartsbytracingtheorigins ofelectricity
leadinguptothefundamental discoveries ofthenottoodistantpast.Whilethistopic
is not an integral part of the conventional coverage in texts and courses in this
ix
X PREFACE
area, this chapter should provide interesting insights into the influence of these
developments on present day civilization. It is through an appreciation ofthe past
developmentsandachievementsthat wecan understandour presentand forge ahead
with future advances.
Chapter2offerssome backgroundnecessarytocomprehendthebasicsofelectric
machine operations. The advent of the SCR and subsequent developments in solid
state and power electronics technology introduced new elements in the practice of
motorspeed control. This importantarea is now of sufficientmaturity that itshould
form an integral part of any comprehensive treatment ofelectric motors. This text
recognizes this need byofferinginChapter3,adetailedtreatmentof powerelectro
nic devices and systems to allow integration of the discussion with each electric
motor with its adjustable speed drive application in the subsequent chapters.
Chapters 4 to 8 deal with the conventional topics covered in present courses in
electric machines and transformers. Emphasis is given to practical aspects, such
as dealing with matching motors to loads, speed control, starting, and in general
to the main performance characteristics ofthe devices discussed.
I have attempted to make this book as self-containing as much as possible. As a
result, the reader will find that many background topics such as magnetic circuits,
the per unit systemand three-phase circuitsare included in the text's main body, as
opposed to the recent trend towards including many appendices dealing with these
topics. Instudyingandteachingelectricalmachines,ithasbeen myexperiencethata
problem-solving approach is most effective when exploring this rich area. As a
result, the reader will find many problems at the end ofeach chapter that reinforce
the concepts learned in the chapter.
Atextbooksuch asthis could not have been written without the continuinginput
of the many students who have gone through many versionsofits material as itwas
developed. My sincere thanks to the members ofthe many classes I was privileged
to teach this fascinating area. I wish to acknowledge the able work ofElizabeth J.
Sanford in puttingthis manuscript ina bettershape than I was able to produce. My
continuing association with the IEEE Press and Wiley staff have been valuable
throughout the manystagesofpreparingthis text. Iwish toexpressmy appreciation
for their work.
loweadebtofgratitudetomany ofmy colleagueswho reviewedthis manuscript
and provided many valuable comments that improved this work considerably: It is
always a great pleasure to acknowledge with thanks the continuing support of
Dalhousie University during the course of preparing this text. As always, my
wife, Dr. Ferial EI-Hawary's patience and understanding have made this project
anotherjoy to look forward to completing.
MOHAMED E. EL-HAWARY
Halifax, Nova Scotia
March 2002