The McGroW'Hill Companies Electric Drives Concepts and Applications Second Edition The McGroW'Hill Companies ABOUT THE AUTHOR Vedam Subrahmanyam received his MSc (Engineering) degree in Electrical Machine Design from Madras University in 1963 and his PhD from IIT Madras in 1973. He joined ITT Madras in 1966 and served as a Professor in the department of Electrical Engineering. Prior to this, he had taught for two years at Visweswaraya Regional College of Engineering, Nagpur, and Regional Engineering College, Warangal, as a faculty member. A popular academician, he has guided several research students at the MTech and PhD levels. Prof. Subrahmanyam has published around 60 articles in national and interna- tional journals and has also presented papers at international conferences. He has attended programmes in Germany and worked as a faculty member at the Uni- versity of Dar-es-Salaam for two years. He is the author of well-acclaimed books like Power Electronics: Devices, Converters, Applications and Thyristor Control of Electric Drives, the latter published by Tata McGraw-Hill. The McGroW'Hill Companies Electric Drives Concepts and Applications Second Edition Vedam Subrahmanyam Former Professor Department of Electrical Engineering Indian Institute of Technology Chennai m L J Tata McGraw Hill Education Private Limited NEW DELHI McGraw-Hill Offices New Delhi New York St Louis San Francisco Auckland Bogota Caracas Kuala Lumpur Lisbon London Madrid Mexico City Milan Montreal San Juan Santiago Singapore Sydney Tokyo Toronto The McGroW'Hill Companies Tata McGraw-Hill Published by the Tata McGraw Hill Education Private Limited, 7 West Patel Nagar, New Delhi 110 008. Electric Drives, 2e Copyright © 2011, 1994, by Tata McGraw Hill Education Private Limited. 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Typeset at ACE PRO India Private Limited, Ghaziabad 201 014, and printed at Avon Printers, Plot No 16, Main Loni Road, Jawahar Nagar Indl. Area, Shahdara, Delhi 110 094. Cover: SDR RAXCRRQZDRBCZ The McGraw-Hill Companies I The McGroW'Hill Companies Dedicated to my beloved mother late Smt Seshamma The McGraw HIII Companies The McGroW'Hill Companies Contents C Preface XI Introduction 1 1. Characteristics of Electric Motors 5 1.1 Introduction 5 1.2 Characteristics of DC Motors 6 1.3 Characteristics of a Three-phase Induction Motor 29 1.4 Characteristics of Synchronous Motors 46 1.5 Braking of Electric Motors 57 1.6 Starting of Electric Motors 75 Worked Examples 83 Problems 93 Multiple-Choice Questions 98 References 100 2. Dynamics of Electric Drives 101 2.1 Introduction 101 2.2 Classification of Electric Drives 102 2.3 Basic Elements of an Electric Drive 103 2.4 Dynamic Conditions of a Drive System 116 2.5 Stability Considerations of Electrical Drives 118 Worked Examples 123 Problems 127 Multiple-Choice Questions 128 References 129 3. Converters for Feeding Electric Motors 130 3.1 A General Survey of Converters for Feeding Electric Motors 130 3.2 Phase Controlled Line Commutated Converters 143 3.3 DC Choppers 210 3.4 Inverters 224 3.5 Cycloconverters 243 3.6 AC Voltage Controller 246 The McGroW'Hill Companies Contents Worked Examples 273 Problems 286 Multiple-Choice Questions 290 References 291 4. Control of Electric Motors 293 4.1 Induction Motor Drives 295 4.2 Synchronous Motor Drives 343 4.3 DC Drives 367 4.4 Permanent Magnet Synchronous Motor 413 4.5 Classification of Permanent Magnet Synchronous Motors 419 4.6 Cycloconverter-fed Synchronous Motor 425 Worked Examples 429 Problems 448 Multiple-Choice Questions 458 References 464 5. Rating and Heating of Motors 466 5.1 Requirements of a Drive Motor 466 5.2 Power Losses and Heating of Electric Motors 466 5.3 Heating and Cooling of an Electric Motor 468 5.4 Classes of Duty and Selection of Motor 474 Worked Examples 491 Problems 494 Multiple-Choice Questions 495 References 496 6. Control Techniques for Electrical Drives 497 6.1 Introduction 497 6.2 Basic Features of an Electric Drive 499 6.3 Block Diagram Representation of Drive Systems 500 6.4 Signal Flow Graph Representation of the Systems 504 6.5 Transfer Functions 505 6.6 Transient Response of Closed Loop Drive Systems 517 6.7 Frequency Response Approach 524 6.8 Stability of Controlled Drives 531 6.9 Compensation and the Use of Controllers to Improve the Performance 543 Worked Examples 587 Problems 598 The McGroW'Hill Companies O Contents Multiple-Choice Questions 601 References 602 7. Drives for Specific Applications 603 7.1 Drive Considerations for Textile Mills 604 7.2 Steel Rolling Mills 609 7.3 Cranes and Hoist Drives 615 7.4 Cement Mills 625 7.5 Sugar Mills 629 7.6 Machine Tools 631 7.7 Paper Mills 633 7.8 Coal Mines 635 7.9 Centrifugal Pumps 636 7.10 Turbocompressors 642 7.11 Summary of Thyristorised AC and DC Drives 645 Multiple-Choice Questions 650 References 652 8. Microprocessors and Control of Electrical Drives 653 8.1 Introduction 653 8.2 Dedicated Hardware Systems versus Microprocessor Control 654 8.3 Application Areas and Functions of Microprocessors in Drive Technology 656 8.4 Control of Electric Drives Using Microprocessors 663 8.5 Some Aspects of Control System Design of Microprocessor Based Variable Speed Drives 698 8.6 Stepper Motors 699 Multiple-Choice Questions 709 References 710 Appendix A 711 Appendix B 721 Index 727 The McGraw HIII Companies