Fundamentals of electric drives

364 Pages·2019·17.446 MB·English

by  Mohamed A. El-Sharkawi

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SE / El-Sharkawi / Fundamentals of Electric Drives ISBN-13: 9781305970960 ©2019 Designer: Harasymczuk Design
Text & Cover printer: Quad Graphics Binding: PB Trim: 7.375 x 9.25" CMYK
Fundamentals of
Electric Drives
Second Edition
Mohamed A. El-Sharkawi
University of Washington
Australia ● Brazil ● Mexico ● Singapore ● United Kingdom ● United States
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© 2019, 2000 Cengage Learning®
Fundamentals of Electric Drives,
Second Edition
Unless otherwise noted, all content is © Cengage.
Mohamed A. El-Sharkawi
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Dedicated to my family and my students
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Preface
A modern electric drive system consists of a motor, an electric converter, and a controller
that are integrated to perform a mechanical maneuver for a given load. Because the torque/
volume ratio of modern electric drive systems is continually increasing, hydraulic drives
are no longer the only option used for industrial applications. In addition to their use in
industrial automation, modern electric drives have other widespread applications, rang-
ing from robots to automobiles to aircraft. Recent advances in electric drive design have
resulted in low-cost, lightweight, reliable motors. Advances in power electronics have
led to a level of performance that was not possible a few years ago; induction motors, for
example, were never used in variable-speed applications until the development of variable
frequency and rapid switching. Due to advances in power electronics, several new designs
of electric motors are now available, such as brushless and stepper motors.
Modern electric drive systems are used increasingly in such high-performance ap-
plications as robotics, guided manipulations, transportation, renewable energy, and ac-
tuation. In these applications, controlling the rotor speed is only one of several goals; the
full range includes controlling the starting, speed, braking, and holding of the electric
drive systems. The exploration of these control functions forms the core of this text.
Purpose and Features
This book is designed to be used as a teaching text for a one-semester course on the fun-
damentals of electric drives. Readers are expected to be familiar with the basic circuit
theories and the fundamentals of electronics, as well as with three-phase analysis and
basic electric machinery.
In this book, I cover the basic components of electric drive systems, including me-
chanical loads, motors, power electronics, converters, and gears and belts. Each compo-
nent is first discussed separately; various components are then combined in a discussion
of the complete drive system. If instructors use this book in the first course on the sub-
ject, they will not need to use additional material because this book is self-contained.
The focus of this book is on the fundamentals of electric drive systems. The general
types of electric loads and their dependence on speed are explained early in the book,
and load characteristics are considered throughout. To help the reader understand why a
particular motor is selected for a particular application, I present and highlight the dif-
ferences and similarities of electric motors.
Power converters are discussed in some detail, with ample mathematical analysis.
Early in the book, I present several solid-state switching devices and specific charac-
teristics of each; this comparison of solid-state devices allows the reader to understand
their features, characteristics, and limitations. Triggering, synchronization, modulation,
isolation, and protection of power electronic devices are also discussed in detail.
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vi Preface
Converters are divided into several groups: ac/dc, ac/ac, dc/ac, and dc/dc. Several
circuits are given for these converters and are analyzed in detail to help readers un-
derstand their performance. Detailed analyses of the electrical waveforms of power-
converter circuits demonstrate the concepts of power and torque in a harmonic
environment.
After readers become familiar with electric machines and power converters, they
can comprehend the integration of these two major components that creates an electric
drive system. This book includes detailed explanations of the various methods for speed
control and braking. Well-known applications appear throughout the book in order to
demonstrate the theories and techniques. Discussions of the merits, complexities, and
drawbacks of the various drive techniques help readers form opinions from the perspec-
tive of a design engineer.
Examples and Problems
In each chapter, examples and problems simulate several aspects of drive performance.
The problems address key design and performance issues and are therefore more than
mere mathematical exercises.
New Features
Improved focus on the basic principles of power electronic devices, including both
synchronization and isolation circuits.
New sections on brushless motors have been added to Chapters 5 and 6.
Additional analysis of static Scherbius drives.
New coverage of wind energy systems operating in regenerative braking.
Applications to electric vehicle, robotic, and electric tractions are provided throughout.
New sections on regenerative, dynamic, and concurrent braking of BLDC motors.
New examples and exercises have been added throughout the book.
Supplements
An Instructor’s Solutions Manual and Lecture Note PowerPoint slides are available
for this book on Cengage Learning’s secure, password-protected Instructor Resource
Center. The Instructor Resource Center can be accessed at https://login.cengage.com.
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Second Edition
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Preface vii
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ACkNOwlEdgmENtS
I wish to thank the reviewers for this edition who asked to be acknowledged:
Youakim Kalaani of Georgia Southern University and Mehrdad Ehsani of Texas
A&M University. The other reviewers wished to remain anonymous. All of their
feedback was very helpful.
I wish to acknowledge and thank the Global Engineering team at Cengage Learning
for their dedication to this new book:
Timothy Anderson, Product Director; Mona Zeftel, Senior Content Developer;
Rebecca Donahue, Content Project Manager; Alexander Sham, Product Assistant; and
Rose Kernan of RPK Editorial Services, Inc. They have skillfully guided every aspect
of this text’s development and production to successful completion.
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Contents
1 ElEMEntS oF ElEctric DrivE SyStEMS 1
1.1 Historical Background 2
1.2 Basic Components of an Electric Drive System 5
1.2.1 Mechanical Loads 6
1.2.2 Electric Motors 8
1.2.3 Power Sources 9
1.2.4 Converters 9
1.2.5 Controllers 10
2 introDuction to SoliD-StAtE DEvicES 12
2.1 Transistors 13
2.1.1 Bipolar Transistor 13
2.1.2 Field Effect Transistor (FET) 16
2.2 Thyristors 19
2.2.1 Four-Layer Diode 19
2.2.2 Silicon-Controlled Rectifier 21
2.3 Other Power Devices 23
2.3.1 Darlington Transistor 23
2.3.2 Insulated Gate Bipolar Transistor (IGBT) 24
2.4 Ratings of Power Electronic Devices 25
2.5 di/dt and dv/dt Protection 26
Problems 31
3 introDuction to SoliD-StAtE Switching circuitS 32
3.1 Single-Phase, Half-Wave, ac/dc Conversion for Resistive Loads 32
3.1.1 Root-Mean-Squares 35
3.1.2 Electric Power 37
3.1.3 dc Power 40
3.1.4 Power Factor 41
3.2 Single-Phase, Full-Wave, ac/dc Conversion for Resistive Loads 43
3.3 Single-Phase, Half-Wave, ac/dc Conversion for Inductive Loads Without
Freewheeling Diode 46
3.3.1 Average Voltage Across Inductance and Resistance 49
3.3.2 Average Power of Inductance 50
3.3.3 RMS Voltage 51
3.4 Single-Phase, Half-Wave, ac/dc Conversion
for Inductive Loads with Freewheeling Diode 52
viii
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Contents ix
3.5 Three-Phase, Half-Wave, ac/dc Conversion for Resistive Loads 56
3.6 Three-Phase, Half-Wave, ac/dc Conversion for Inductive Loads 59
3.7 Three-Phase, Full-Wave, ac/dc Conversion 60
3.8 dc/dc Conversion 66
3.9 dc/ac Conversion 70
3.9.1 Single-Phase, dc/ac Converter 70
3.9.2 Three-Phase dc/ac Converter 71
3.9.3 Voltage, Frequency, and Sequence Control 77
3.9.4 Pulse-Width Modulation (PWM) 80
3.10 Energy Recovery Systems 84
3.10.1 Charging Operation 84
3.10.2 Discharging Operation 88
3.11 Three-Phase Energy Recovery Systems 91
3.12 Current Source Inverter 94
3.13 Triggering Circuits 96
3.13.1 Synchronization of Triggering Circuits 97
3.13.2 Isolation of Triggering Circuits 100
Problems 104
4 Joint SpEED-torquE chArActEriSticS oF ElEctric
MotorS AnD MEchAnicAl loADS 107
4.1 Bidirectional Electric Drive Systems 108
4.2 Four-Quadrant Electric Drive Systems 110
Problems 113
5 SpEED-torquE chArActEriSticS oF ElEctric
MotorS 114
5.1 Brush-type dc Motors 114
5.1.1 Separately Excited Motors 117
5.1.2 Shunt Motors 121
5.1.3 Series Motors 122
5.1.4 Compound Motors 124
5.2 Brushless dc Motor 126
5.2.1 Unipolar BLDC Motor 127
5.2.2 Bipolar BLDC Motor 128
5.2.3 Model and Analysis of BLDC Motors 133
5.3 Induction Motors 136
5.3.1 Equivalent Circuit 140
5.3.2 Power Flow 144
5.3.3 Torque Characteristics 147
5.3.4 Starting Procedure 151
5.4 Synchronous Motors 153
5.4.1 Reactive Power 155
5.4.2 Power Flow 158
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