Electric machine theory for power engineers

Book Review ELECTRIC MACHINE THEORY FOR POWER ENGINEERS, by Van E. Mablekos. 698 pages, Harper & Row, New York, 1980. In the Preface, the author stated that this text is especially designed to be used as a one year introductory course for electrical engineering students whose major field is power systems engineering. The text is unique in that it serves as an electric machines text with a natural extension into power systems engineering, and the material is presented from the systems point of view. This text is of value also to the nonelectrical engineering student interested in excitation systems, synchronous devices, and the basics of power systems engineering. In an Editor’s Note, it was revealed to the reviewer’s surprise that Professor Van E. Mablekos passed away on 22 January 1979 and the preparation of the manuscript for publication had to be done by Professor Demosthenes P. Gelopulos and Eugenio Villaseca of Arizona State University. There are altogether 7 chapters and 5 appendices. Chapter 1 develops the fundamental magnetic circuit, with the aid of Biot-Savart’s law and Ampere’s law and sets forth the fundamentals of transformer operations. The equivalent circuit of the real transformer is first developed. Then the balanced three-phase transformer, the autotransformer, and the Scott transformer are introduced. Chapter 2 introduces the principles of motoring and generation and Kron’s primitive machine. The chapter heading is “dc Energy Converters”, while the heading of the first chapter is simply “Transformers”. Torque-speed characteristics of various dc motor types and voltageecurrent characteristics of various dc generator types are given. Applications of dc energy converters, dynamic analysis, and parameter measurement for equivalent circuits of dc devices are then covered. Chapter 3 deals with “Three-Phase Systems Theory”. Three-phase balanced generators (both Y-connected and n-connected) are presented. After a brief Vol. 316, No. 1, pp. 125-126, July 1983 Printed in Great Britain

discussion of transmission lines, balance three-phase loads and power measurement methods are presented. Chapter 4 develops the theory of the rotating field in the stator and rotor structures of the three-phase induction device. An equivalent circuit is given. Torque vs slip characteristics are derived. Methods for speed control of an induction motor are covered. Then the two-phase induction motor and the single-phase motor are discussed with their applications. Chapters 5 and 6 cover synchronous machines-fundamental concepts and system considerations. In Ch. 5 the equivalent circuit of the synchronous generator is derived. Phasor diagram analysis under unity power-factor, lagging and leading power-factor is given. Similarly, the equivalent circuit of the synchronous motor is derived and phasor diagram analysis is given. Real and reactive power vs powerangle characteristics are discussed. Applications of balanced three-phase and two-phase synchronous devices are covered. The single-phase, reluctance-type and hysteresis-type synchronous devices are included. This book is unique in adopting the system point of view in the study of rotating machines-energy converters. In Ch. 6, dynamic analysis of synchronous machines connected to an infinite bus is made using linear and nonlinear analysis (Cases 1 and 2). The solution of the swing equation is given. Balanced, three-phase, salient-pole machines are then analyzed. Three-phase faults involving constant-reactance and variablereactance techniques are considered. The last chapter deals with parameter measurement of three-phase synchronous machines. In the salient-pole machine, both direct axis and quadrature axis reactances X, and X, must be measured. For transient studies, Xi, Xi, Xh and Xi must also be measured. Special effort is made to familiarize the reader (or student) with the technique of measuring the time constants associated with the dynamic modeling of synchronous devices.

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Book Review The book has 5 appendices: A. Frequency-domain analysis ; B. Instrumentation; C. Stability theory; D. Definitions and theorems ; and E. Solid state power electronics : The silicon controlled rectifier (SCR) or thyristor. Appendix E is worth reading. There are many figures, diagrams and pictures, as well as numerical examples. It can be suitably used in a senior course for electrical and system engineers. The author had refrained from introducing more theoretical and mathematical material into this textbook. For example, there is only one brief mention of Kron’s primitive machine but no mention of “diakoptics” or “tensor analysis”. The author did a re-

markable essay on this reviewer’s “Collected Papers” (see J. Franklin Inst., Vol. 297, No. 2, 1974). However, he did not mention the “revolving-field theory” of synchronous machines and the “forward and backward components” parallel to the “two-reaction theory” and the “direct and quadrature components”. We regret very much the passing of Professor Mabelkos; however, this remarkable book will live as a memorial to him by his friends and colleagues. Y. H. Ku Moore School of Electrical Engineering University of Pennsylvania Philadelphia, PA 19104, U.S.A.

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of the Franklin Institute Pergamon Press Ltd.