PERMANENT MAGNET

ELECTRICAL AND COMPUTER ENGINEERING

A Series of Reference Books and Textbooks

FOUNDING EDITOR

Marlin 0. ThurstonDepartment of Electrical Engineering

The Ohio State University

Columbus, Ohio

1. Rational Fault Analysis, edited by Richard Saeks and S. R. Liberty2. Nonparametric Methods in Communications, edited by

Kazakos and Kazakos3. Interactive Pattern Recognition, Chien4. Solid-State Electronics, Lawrence f. Murr5. Electronic, Magnetic, and Thermal Properties of Solid Materials, Klaus

6. Magnetic-Bubble Memory Technology, Hsu Chang7. Transformer and Inductor Design Handbook, Colonel Wm.

McLyman8. Classical and Modern Theory and Applications,

Samuel Seely and Alexander9. One-Dimensional Digital Signal Processing, Chen

10. Interconnected Dynamical Systems, Raymond A. and RichardSaeks

Modern Digital Control Systems, Raymond G. Jacquot12. Hybrid Circuit Design and Manufacture, Roydn Jones13. Magnetic Core Selection for Transformers and Inductors: A Users

Guide to Practice and Specification, Colonel Wm. McLyman14. Static and Rotating Electromagnetic Devices, Richard H. fngelmann15. Energy-Efficient Electric Motors: Selection and Application, John C.

16. Electromagnetic Compossibility, Heinz17. Electronics: Models, Analysis, and Systems, James G. 18. Digital Filter Design Handbook, Fred J. Taylor19. Multivariable Control: An Introduction,20. Flexible Circuits: Design and Applications, Steve with con-

tributions by Carl A. fdstrom, Jr., Ray Greenway, and William P.Kelly

21. Circuit Interruption: Theory and Techniques, Thomas Jr.22. Switch Mode Power Conversion: Basic Theory and Design, K. Kit Sum23. Pattern Recognition: Applications to Large Data-Set Problems,

Tze Bow

24. Custom-Specific Integrated Circuits: Design and Fabrication, Stanley

Hurst25. Digital Circuits: Logic and Design, Ronald C. Emery26. Large-Scale Control Systems: Theories and Techniques, S.

Mahmoud, Mohamed F. Hassan, and Mohamed G. Darwish27. Microprocessor Software Project Management, T. and Cedric

V. W. Armstrong (Sponsored by Ontario Centre for Microelectronics)28. Low Frequency Electromagnetic Design, Michael P. Perry29. Multidimensional Systems: Techniques and Applications, edited by

Spyros G. Tzafestas30. AC Motors for High-Performance Applications: Analysis and Control,

Sakae Yamamura31. Ceramic Motors for Electronics: Processing, Properties, and Applica-

tions, edited by Relva C. Buchanan32. Microcomputer Bus Structures and Bus Interface Design, Arthur L.

Dexter33. End Users Guide to Innovative Flexible Circuit Packaging, Jay J.

Minie t34. Reliability Engineering for Electronic Design, Norman B. 35. Design Fundamentals for Low-Voltage Distribution and Control, Frank

and Jack L. Warren36. Encapsulation of Electronic Devices and Components, Edward R.

Salmon37. Protective Relaying: Principles and Applications, J. Lewis Blackburn38. Testing Active and Passive Electronic Components, Richard F. Powell39. Adaptive Control Systems: Techniques and Applications, V. V. Chalam40. Computer-Aided Analysis of Power Electronic Systems, Venkatachari

Rajagopalan41. Integrated Circuit Quality and Reliability, Eugene R. Hnatek42. Systolic Signal Processing Systems, edited by E. Jr.43. Adaptive Digital Filters and Signal Analysis, Maurice G. Be//anger44. Electronic Ceramics: Properties, Configuration, and Applications, edi-

ted by Lionel M. Levinson45. Computer Systems Engineering Management, Robert S. A/ford46. Systems Modeling and Computer Simulation, edited by Naim A. Kheir47. Rigid-Flex Printed Wiring Design for Production Readiness, Walter S.

Rigling48. Analog Methods for Computer-Aided Circuit Analysis and Diagnosis,

edited by Takao Ozawa49. Transformer and Inductor Design Handbook: Second Edition, Revised

and Expanded, Colonel Wm. T.50. Power System Grounding and Transients: An Introduction, A. P.

Meliopoulos51. Signal Processing Handbook, edited by C. H. Chen52. Electronic Product Design for Automated Manufacturing, H. Richard

53. Dynamic Models and Discrete Event Simulation, William Delaney and Vaccari

54. FET Technology and Application: An Introduction, Edwin S. Oxner

55. Digital Speech Processing, Synthesis, and Recognition, Sadaoki Furui56. VLSI RISC Architecture and Organization, Stephen Furber57. Surface Mount and Related Technologies, Gerald Ginsberg58. Uninterruptible Power Supplies: Power Conditioners for Critical

Equipment, David C. 59. Polyphase Induction Motors: Analysis, Design, and Application, Paul

Cochran60. Battery Technology Handbook, edited by A. Kiehne61. Network Modeling, Simulation, and Analysis, edited by Ricardo

Garzia and Mario R. Garzia62. Linear Circuits, Systems, and Signal Processing: Advanced Theory

and Applications, edited by Nobuo Nagai63. High-Voltage Engineering: Theory and Practice, edited by Khalifa64. Large-Scale Systems Control and Decision Making, edited by Hiroyuki

Tamura and Tsuneo Yoshikawa65. Industrial Power Distribution and Illuminating Systems, Kao Chen66. Distributed Computer Control for Industrial Automation,

Popovic and P. 67. Computer-Aided Analysis of Active Circuits, Adrian68. Designing with Analog Switches, Steve Moore69. Contamination Effects on Electronic Products, Taufscher70. Computer-Operated Systems Control, Magdi S. Mahmoud71. Integrated Microwave Circuits, edited by Yoshihiro Konishi72. Ceramic Materials for Electronics: Processing, Properties, and Ap-

plications, Second Edition, Revised and Expanded, edited by C.Buchanan

73. Electromagnetic Compatibility: Principles and Applications, David A.Weston

74. Intelligent Robotic Systems, edited by Spyros G. Tzafesfas75. Switching Phenomena in High-Voltage Circuit Breakers, edited by

Kunio Nakanishi76. Advances in Speech Signal Processing, edited by Sadaoki Furui and

M. Mohan Sondhi77. Pattern Recognition and Image Preprocessing, Sing-Tze78. Energy-Efficient Electric Motors: Selection and Application, Second

Edition, John C. 79. Stochastic Large-Scale Engineering Systems, edited by Spyros G.

Tzafestas and Keigo Watanabe80. Two-Dimensional Digital Filters, Wu-Sheng Lu and Anfoniou81. Computer-Aided Analysis and Design of Switch-Mode Power Supplies,

Lee82. Placement and Routing of Electronic Modules, edited by Michael Pecht83. Applied Control: Current Trends and Modern Methodologies, edited by

Spyros G. Tzafesfas84. Algorithms for Computer-Aided Design of Multivariable Control

Systems, and Hugh F. 85. Symmetrical Components for Power Systems Engineering, Lewis

86. Advanced Digital Signal Processing: Theory and Applications, GlennZelniker and Fred J. Taylor

87. Neural Networks and Simulation Methods, Jian-Kang88. Power Distribution Engineering: Fundamentals and Applications,

James J. Burke89. Modern Digital Control Systems: Second Edition, Raymond G. 90. Adaptive Filtering in Signal Processing and Control, A.

Regalia91. Integrated Circuit Quality and Reliability: Second Edition, Revised and

Expanded, Eugene R. Hnatek92. Handbook of Electric Motors, edited by Richard H. Engelmann and

William H. Middendotf93. Power-Switching Converters, Simon S. Ang

94. Systems Modeling and Computer Simulation: Second Edition, A.Kheir

95. Filter Design, Richard Lee Ozenbaugh96. Power Hybrid Circuit Design and Manufacture, Haim Taraseiskey97. Robust Control System Design: Advanced State Space Techniques,

Chia-Chi98. Spatial Electric Load Forecasting, H. Lee Willis99. Permanent Magnet Motor Technology: Design and Applications, Jacek

F. Gieras and Mitchell Wing100. High Voltage Circuit Breakers: Design and Applications, Ruben D.

Garzon101. Integrating Electrical Heating Elements in Appliance Design, Thor

Hegbom102. Magnetic Core Selection for Transformers and Inductors: A Users

Guide to Practice and Specification, Second Edition, Co/one/ Wm. T.

103. Statistical Methods in Control and Signal Processing, edited byKatayama and Sueo Sugimoto

104. Radio Receiver Design, Robert C. Dixon105. Electrical Contacts: Principles and Applications, edited by G.

106. Handbook of Electrical Engineering Calculations, edited G.Phadke

107. Reliability Control for Electronic Systems, Donald J. 108. Embedded Systems Design with 8051 Microcontrollers: Hardware and

Software, Zdravko Karakehayov, Knud Christensen, and O/eWinther

109. Pilot Protective Relaying, by E/more110. High-Voltage Engineering: Theory and Practice, Second Edition,

Revised and Expanded, Hussein Morshedy, and Roshdy Radwan

111. Filter Design: Second Edition, Revised and Expanded, RichardLee Ozenbaugh

112. Electromagnetic Compatibility: Principles and Applications, Second

Edition, Revised and Expanded, David A. Weston113. Permanent Magnet Motor Technology: Design and Applications,

Second Edition, Revised and Expanded, Jacek Gieras and MitchellW i n g

Additional Volumes in Preparation

High Voltage Circuit Breakers: Design and Applications, SecondEdition, Revised and Expanded, Ruben

PERMANENT

Design and Applications

Second Edition, Revised and Expanded

JACEK F.

United Technologies Research Center

Hartford, Connecticut

London, United Kingdom

MARCEL DEKKER, INC. NEW YORK

ISBN: o-8247-0739-7

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Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

Neither this book nor any part may be reproduced or transmitted in any form or by any

means, electronic or mechanical, including photocopying, microfilming, and recording, or

by any information storage and retrieval system, without permission in writing from the

publisher.

Current printing (last digit):

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PRINTED IN THE UNITED STATES OF AMERICA

Preface to the

Second Edition

The importance of permanent magnet motor technology and its impact on

electromechanical drives has significantly increased since publication of the

first edition of this book in 1996. The permanent magnet (PM)

prices have dropped and their performance has improved, brushless motor

technology has become much more mature, in many applications commu-

tator motors have been replaced by more reliable brushless motors, new

PM motor topologies have found their first applications, and significantprogress in control techniques and design computations has been achieved.

Application of small PM brushless motors has increased on a large scale not

only in computer hardware but also in consumer electronics, building equip-

ment, force, airborne apparatus, instrumentation and automation

systems. The era of electric and hybrid cars is close and it is obvious thatPM brushless motors are the highest power density and efficiency traction

motors. The all-electric ship, more electric aircraft, advanced combat vehi-

cle, smart buildings and other large-scale research programs also stimulate

the development of PM motors. Since the 1996 book does not cover themost recent advances, the authors have prepared this revised, improved,

and expanded second edition. We believe that the new edition will serve

as both a textbook and design handbook for PM motors and will stimulate

innovations in this field.

F. Gieras

Mitchell Wing

111

Preface to the

First Edition

In a modern industrialized country about 65% of electrical energy is con-

sumed by electrical drives. Constant-speed, variable-speed or servo-motor

drives are used almost everywhere: in industry, trade and service, house-

holds, electric traction, road vehicles, ships, aircrafts, military equipment,

medical equipment and agriculture. Electromechanical drives for speed and

position control play a key role in robotics, factory automation, process con-

trol, energy conservation and electric vehicles. There is an increasing need

to train students, electrical engineers, and electromechanical engineers in

the area of modern electrical motors and drives, their control, simulation

and CAD.

Vector control methods developed in the early 1970s allow for controlling

three-phase induction motors in the same way as d.c. commutator motors.

This new control technology, in connection with the high reliability, very

limited maintenance and low price of cage induction motors, has made

induction motors the most popular motors today.

With the world-wide trend to energy conservation, there is a need to

increase the efficiency of a.c. drives, small and large. The recent advance-

ments of permanent magnet (PM) materials, solid-state devices and mi-

croelectronics have contributed to new energy efficient, high performance

electric drives which use modern PM brushless motors. Owing to rare-earth

these motors have higher efficiency, power factors, output power per

mass and volume, and better dynamic performance than cage induction

motors without sacrificing the reliability. It is quite possible that these PM

brushless motor drives will become predominant in the next century.

Progress in PM materials has also revolutionized construction of other

PM motors such as commutator motors and stepping motors, as well

as making possible the manufacture of large PM motors (megawatts) and

micromotors (milliwatts).

v i Preface to the First Edition

New electromechanical drive technology has had an impact on teaching

and training. Modern electrical drives courses in electrical engineering de-

partments and the continuing education of practicing engineers require a

book which can cover the broad topic of PM motors and their applications.

In comparison with other recent books on the subject, this book coversnot only brushless PM motors but also other types of PM motors (d.c.

commutator, large, micro-, special purpose, disk, stepping motors), their

applications, and principles of optimization and design. This book can also

be used as a handbook of PM motors.

The aim of Chapter 1, Introduction, is to bring the reader into the

modern world of electromechanics and motion control. The structure ofelectromechanical drives and classification of PM motors are described. The

current and future trends in the PM motors and drives industry are dis-cussed. This chapter also shows the reader how to select PM motors to

meet the specific requirements of electrical drives. The second chapter,

Permanent Magnet Materials and Circuits, is devoted to the physics ofhard magnetic materials and practical calculation of PM circuits. Analysis

of magnetic circuits is based on PM materials currently available on the

market. How to find an operating point, including armature reaction, andhow to evaluate the permeance and permeances for leakage fluxes

are emphasized. Chapter 3, Finite Element Analysis, deals with CAD de-

sign of PM motors with the aid of the finite element method (FEM). Field

equations, their solutions, boundary conditions, pre-processing and post-

processing routines and determination of integral parameters (inductances,back EMF, forces, torques) are discussed. According to a survey made in

different parts of the world, nearly 20% of electrical engineers working in

industry require additional updated knowledge in Chap-ter 4, Commutator Motors, deals with cost effective d.c. commutator

motors with barium ferrite manufactured in large quantities. Chapter

5 Theory of Permanent Magnet Synchronous Motors discusses analysis of

synchronous motors with Chapter 6, Brushless Motors, empha-sizes the differences between the synchronous motors (sinusoidally excited)

and (square wave) brushless motors. The next three chapters, Ax-

ial Flux Motors, High Power Density Brushless Motors, and Brushless

Motors of Special Construction, focus on a large family of brushless mo-

tors with moving such as motors of cylindrical and disk construction,micromotors, large motors (ship propulsion), single-phase motors, trans-

verse flux motors, and other configurations. Special attention is paid to

their application to modern electrical drives. Stepping motors with active

PM rotors are discussed in Chapter 10, Stepping motors. Fundamentals of

modern mathematical methods of optimization, including population-based

incremental learning, are found in Chapter 11, Optimization. This

Preface to the First Edition

ter also shows how to integrate FEM into optimization routines. The book

concludes with a discussion of reliability, vibration and noise, condition

monitoring, protection and lubrication of PM motors (Chapter

12, Maintenance).

In each chapter, applications of PM motors to various electromechanicaldrives are presented. Some examples of applications are limited to block

diagrams but most show ready-to-implement solutions to practical motion

control problems or how to modernize existing traditional drives. Eachchapter also contains numerical examples of performance calculations or

design of PM motor drives. Both classical and finite element approaches

are used.

This book was written in the Department of Electrical Engineering at

the University of Cape Town. Research carried out by the Electrical Ma-

chines Group is partially presented in Chapters 2, 4, 5, 6 and 11. The rest

of the material was selected and compiled on the basis of abundant

literature on PM motors and drives. The authors are aware that not all

existing PM motor designs have been described and not all contributionsto the development of PM motor drives have been included. This is never

possible and the authors apologize to researchers whose work has not been

covered.

The book has been sponsored by the Foundation for Research Devel-

opment (FRD) with some financial support received from Eskom and theUniversity of Cape Town.

F. Gieras

Mitchell Wing