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    MOTOR DRIVESModeling, Simulation, Analysis,

    Design, and Applications

  • Titles included in the series

    Supervised and Unsupervised Pattern Recognition:Feature Extraction and Computational Intelligence

    Evangelia Micheli-Tzanakou, Rutgers University

    Switched Reluctance Motor Drives: Modeling,Simulation, Analysis, Design, and Applications

    R. Krishnan, Virginia Tech

    The Power Electronics HandbookTim L. Skvarenina, Purdue University

    The Handbook of Applied Computational IntelligenceMary Lou Padgett, Auburn University

    Nicolaos B. Karayiannis, University of HoustonLofti A. Zadeh, University of California, Berkeley

    The Handbook of Applied NeurocontrolsMary Lou Padgett, Auburn University

    Charles C. Jorgensen, NASA Ames Research CenterPaul Werbos, National Science Foundation

    I n d u s t r i a l E l e c t r o n i c s S e r i e sSeries Editor

    J. David Irwin, Auburn University



    R. Krishnan Fellow, IEEEThe Bradley Department of Electrical and Computer Engineering

    Fellow, Center for Organizational and Technological Advancement (COTA)Virginia Tech, Blacksburg, Virginia

    Boca Raton London New York Washington, D.C.CRC Press

    Modeling, Simulation, Analysis,Design, and Applications

    I n d u s t r i a l E l e c t r o n i c s S e r i e s

  • This book contains information obtained from authentic and highly regarded sources. Reprinted materialis quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonableefforts have been made to publish reliable data and information, but the author and the publisher cannotassume responsibility for the validity of all materials or for the consequences of their use.

    Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronicor mechanical, including photocopying, microfilming, and recording, or by any information storage orretrieval system, without prior permission in writing from the publisher.

    Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431.

    Trademark Notice:

    Product or corporate names may be trademarks or registered trademarks, and areused only for identification and explanation, without intent to infringe.

    Visit the CRC Press Web site at www.crcpress.com

    2001 by CRC Press LLC

    No claim to original U.S. Government worksInternational Standard Book Number 0-8493-0838-0

    Library of Congress Card Number 2001025727Printed in the United States of America 1 2 3 4 5 6 7 8 9 0

    Printed on acid-free paper

    Library of Congress Cataloging-in-Publication Data

    Ramu, Krishnan.Switched reluctance motor drives: modeling, simulation, analysis, design, andapplications / Krishnan Ramu.

    p. cm.(Industrial electronics series)Includes bibliographical references and index.ISBN 0-8493-0838-0 (alk. paper)1. Reluctance motors. I. Title. II. Series.

    TK2787 .R35 2001621.46dc21 2001025727

    0838_Frame_FM.fm Page iv Monday, May 21, 2001 6:47 AM


  • ForMadhivanan and Ilankeeran

    0838_Frame_FM.fm Page v Monday, May 21, 2001 6:47 AM

  • Preface

    Industrial interest in switched reluctance motor (SRM) drives has varied since 1850s.The recent surge of activity since the 1980s has spurred university and industrialresearch and product development in the U.K. and U.S. and in a very small measurein some other countries. This interest has been primarily due to the emerging marketsfor variable speed drives in consumer and industrial products, such as home appli-ances, air conditioning, hand tools, fans, pump motor drives, extruders, and auto-motive and railway accessory drives. These new applications for variable speed drivesare very cost sensitive while demanding higher reliability and an equivalent perfor-mance of dc and induction motor drives at the minimum. SRM drive systemspromise to meet such demands in some select high-volume applications, hence thespurt of activity in this field. The expansion of knowledge in this field has beengreat, and it is timely to summarize in this book some of the key results in modeling,simulation, analysis, and design procedures for SRMs; their converter topologies;system integration; control techniques with and without position sensors; the muchtalked-about noise issue; and, finally, their applications. With that perspective, thisbook has been in preparation for the last 12 years, and the material has been taughtin a number of IEEE forums, at industrial sites, and at the graduate level at theauthors university and at Padova University in Italy.

    The book presumes a familiarity with fundamentals of electromechanics, intro-ductory power electronics, and linear control system theory, all at the undergraduatelevel. The intended audience for the book is electrical engineers in industrial andfederal laboratories and students at the senior/graduate level in universities. Tradi-tional trappings of worked examples and exercise problems are done away with, asthis subject demands complete immersion and therefore much more intensive studyand initiative to do extensive work by the readers on their own. The book is organizedas follows.

    Chapter 1 contains the introduction to SRM, its principle of operation, varioustypes of SRM configurations including linear SRM, and the equivalent circuit.Chapter 2 discusses the magnetic equivalent circuit derivation and an analyticalapproach to the evaluation of the key three-dimensional relationships among fluxlinkages, excitation current, and rotor position in the SRM. The nonlinear materialcharacteristics are preserved in this approach. These machine characteristics arecentral to the analysis and design of SRMs.

    Chapter 3 contains an analytical design procedure for the SRM based on theoutput power equation that is prevalent in the design of electrical machines. Theresistive and core losses for thermal consideration, criteria for the selection of statorand rotor back iron thickness, pole height, number of phases, ratio of pole arc topole pitch, self-starting requirements to be fulfilled in the design, inductance mea-surement, and design of linear SRM from an equivalent rotary SRM are addressed

    0838_Frame_FM.fm Page vii Monday, May 21, 2001 6:47 AM

  • from fundamentals. Steady-state computation of air gap torque is also derived inthis chapter.

    Converters and their classification, principle of operation, design considerations,and merits and demerits of each converter and their impact on the machine outputform the core of Chapter 4. Converters that have some merit from the point of viewof industrial applications are considered in this selection.

    The converter, SRM, and load are integrated through a controller. The basic drivesystem control is developed and illustrated with an implementation to demonstratethe similarity of this drive to dc and ac drives. The inadequacy of such controllersfor high-performance applications is discussed, and contributing factors are identi-fied. The heart of a high-performance system is current control, and various methodsof current control such as the conventional linearized controller, linearizing anddecoupling controller, and hybrid controller are systematically derived and devel-oped. An alternative to current control is the flux linkages control, and its merits anddemerits are discussed. The torque controller to produce very little torque rippleusing torque distribution function-based control is introduced and its performance isstudied in detail. Finally, analytic derivations of the speed controller gain and timeconstants are made using the symmetric optimum method. Throughout this chapter,an analytical approach is emphasized to understand the relationship between machineparameters and output variables. Usually the literature neglects mutual coupling inperformance prediction. It is shown in the text that its omission may lead to as muchas 6% torque ripple even in very good machine designs. Methods to include mutualcoupling effects in performance prediction and in the linearized and decoupledcurrent controller, flux linkage controller, and torque controller designs are presented.

    Dynamic modeling, simulation, and analysis play crucial roles in the drivesystem analysis and design and are considered in Chapter 6. The subsystems mod-eling and their integration are developed step by step. The simulation procedure isillustrated with results to enhance the understanding of the SRM drive.

    The SRM drive has been plagued with the acoustic noise problem. To understandthis issue, the sources of acoustic noise are explained in Chapter 7. Measures tomitigate noise from magnetic, mechanical, aerodynamic, and electronic sources arepresented. Active noise cancellation techniques using the power converter controlare also described. A brief summary of qualitative measures to reduce noise is given.In order to facilitate noise quantification in laboratories, an introduction to measure-ment is included in this chapter.

    The necessity for absolute rotor position information in SRM drives increasesthe complexity of motor manufacture, with the mounting of position sensors resultingin higher costs compared to other drives that do not require rotor position sensorsfor their operation, such as dc and ac motor drives. Various electronic methods forestimating or predicting the rotor position information are discussed along with theiralgorithms in Chapter 8. These methods are not invasive mechanically and use only thevoltage applied across the winding and the current flowing in it. Many of the methodsdiscussed in the literature are classified and their implementations are discussed toenable readers to asse