Practical Variable Speed Drives and Power Electronics [1 ed.] 0750658088, 9780750658089, 9781417505494
Typical practical applications of VSDs in process control and materials handling, such as those for pumping, ventilation
279 44 5MB
English Pages 299 Year 2003
Cover......Page 1
Half Title Page......Page 2
Titles in the series......Page 3
Title Page......Page 4
Copyright......Page 5
Preface......Page 6
Contents......Page 8
1.1 The need for variable speed drives......Page 13
1.2 Fundamental principles......Page 14
1.3 Torque-speed curves for variable speed drives......Page 19
1.4 Types of variable speed drives......Page 23
1.5 Mechanical variable speed drive methods......Page 25
1.6 Hydraulic variable speed drives methods......Page 26
1.7 Electromagnetic or 'Eddy Current' coupling......Page 28
1.8 Electrical variable speed drive methods......Page 32
2.1 Introduction......Page 48
2.2 Basic construction......Page 49
2.3 Principles of operation......Page 51
2.4 The equivalent circuit......Page 53
2.5 Electrical and mechanical performance......Page 57
2.6 Motor acceleration......Page 60
2.7 AC induction generator performance......Page 62
2.8 Efficiency of electric motors......Page 63
2.9 Rating of AC induction motors......Page 64
2.10 Electric motor duty cycles......Page 66
2.11 Cooling and ventilation of electric motors (IC)......Page 72
2.12 Degree of protection of motor enclosures (IP)......Page 74
2.13 Construction and mounting of AC induction motors......Page 75
2.14 Anti-condensation heaters......Page 77
2.16 Motor selection......Page 78
3.2 Definitions......Page 80
3.3 Power diodes......Page 83
3.4 Power thyristors......Page 85
3.5 Commutation......Page 88
3.6 Power electronic rectifiers (AC/DC converters)......Page 89
3.7 Gate commutated inverters (DC/AC converters)......Page 106
3.8 Gate controlled power electronic devices......Page 116
3.9 Other pwoer converter circuit components......Page 124
4.1 Introduction......Page 126
4.2 The sources of electromagnetic interference......Page 128
4.3 Harmonics generated on the supply side of AC converters......Page 130
4.4 Power factor and displacement factor......Page 141
4.5 Voltages and current on the motor side of PWM inverters......Page 143
5.2 AC frequency converter protection circuits......Page 152
5.3 Operator information and fault diagnostics......Page 160
5.4 Electric motor protection......Page 162
5.5 Thermal overload protection — current sensors......Page 164
5.6 Thermal overload protection — direct temperature sensing......Page 165
6.1 The overall control system......Page 168
6.2 Power supply to the control system......Page 169
6.3 The DC bus charging control system......Page 171
6.4 The PWM rectifier for AC converters......Page 173
6.5 Variable speed drive control loops......Page 175
6.6 Vector control for AC drives......Page 179
6.7 Current feedback in AC variable speed drives......Page 186
6.8 Speed feedback from the motor......Page 188
7.1 Introduction......Page 190
7.2 The basic selection procedure......Page 191
7.3 The loadability of converter fed squirrel cage motors......Page 192
7.4 Operation in the constant power region......Page 195
7.5 The nature of the machine load......Page 196
7.6 The requirements for starting......Page 206
7.7 The requirements for stopping......Page 208
7.9 Selecting the correct size of motor and converter......Page 215
7.10 Summary of the selection procedures......Page 217
8.1 General installation and environmental requirements......Page 221
8.2 Power supply connection and earthing requirements......Page 223
8.3 Start/stop control of AC drives......Page 226
8.4 Installing AC converters into metal enclosures......Page 228
8.5 Control wiring for variable speed drives......Page 234
8.6 Commissioning variable speed drives......Page 239
9.1 Soft-switching......Page 241
9.2 The matrix converter......Page 243
A.2 Microtherm (thermostat)......Page 245
A.3 Thermistor sensors and thermistor protection relays......Page 246
A.4 Thermocouple......Page 250
A.5 Resistance temperature detector (RTD)......Page 252
B.1 Current shunt......Page 256
B.2 Principle of the Hall effect sensor......Page 257
C.1 Analog speed transducers......Page 260
C.2 Digital rotary speed and position transducers......Page 262
D.2 International standards......Page 274
D.4 United States of America standards......Page 275
D.6 South African standards......Page 276
Appendix E: Glossary of common terms used with AC variable speed drives......Page 278
Index......Page 289
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- Malcolm Barnes CPEng BSc(ElecEng) MSEE
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Practical Variable Speed Drives and Power Electronics
Titles in the series Practical Cleanrooms: Technologies and Facilities (David Conway) Practical Data Acquisition for Instrumentation and Control Systems (John Park, Steve Mackay) Practical Data Communications for Instrumentation and Control (John Park, Steve Mackay, Edwin Wright) Practical Digital Signal Processing for Engineers and Technicians (Edmund Lai) Practical Electrical Network Automation and Communication Systems (Cobus Strauss) Practical Embedded Controllers (John Park) Practical Fiber Optics (David Bailey, Edwin Wright) Practical Industrial Data Networks: Design, Installation and Troubleshooting (Steve Mackay, Edwin Wright, John Park, Deon Reynders) Practical Industrial Safety, Risk Assessment and Shutdown Systems (Dave Macdonald) Practical Modern SCADA Protocols: DNP3, 60870.5 and Related Systems (Gordon Clarke, Deon Reynders) Practical Radio Engineering and Telemetry for Industry (David Bailey) Practical SCADA for Industry (David Bailey, Edwin Wright) Practical TCP/IP and Ethernet Networking (Deon Reynders, Edwin Wright) Practical Variable Speed Drives and Power Electronics (Malcolm Barnes)
Practical Variable Speed Drives and Power Electronics Malcolm Barnes CPEng, BSc(ElecEng), MSEE, Automated Control Systems, Perth, Australia .
Newnes An imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 200 Wheeler Road, Burlington, MA 01803 First published 2003 Copyright 2003, IDC Technologies. All rights reserved No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP. Applications for the copyright holder's written permission to reproduce any part of this publication should be addressed to the publisher
British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 07506 58088 For information on all Newnes publications, visit our website at www.newnespress.com
Typeset and Edited by Vivek Mehra, Mumbai, India Printed and bound in Great Britain
Preface The rapid adoption of automation techniques in industry has increased the requirement for better process control. This has resulted in many new applications for AC variable speed drives (VSDs) to control the speed and torque of driven machinery. Variable speed drives (VSDs) are also used to meet particular starting and stopping requirements. The variable speed drives book promotes a sound understanding of how VSDs work and how to correctly select, install, commission and maintain them. There is also detailed coverage of many typical applications in process control and materials handling such as those for pumping, ventilation, conveyers and hoists. This book will benefit anyone associated with the use of VSDs in the industrial or automation environment. This book will also benefit those working in system design as well as site commissioning, maintenance and troubleshooting. Although a basic understanding of electrical engineering principles is essential, even those with a superficial knowledge of VSDs will substantially benefit from this book. In particular, if you work in any of the following areas, you will benefit from this book: • Consulting electrical engineers • Plant engineers and instrument technicians • Operations technicians • Electrical maintenance technicians and supervisors • Instrumentation and control system engineers • Process control engineers • Mechanical engineers We would hope that you will learn the following from this book: • The principles of AC variable speed drives for industrial speed control • The essentials of squirrel cage induction motors • The latest developments in power electronic converters used for VSDs • How to select the correct AC variable speed drive for industrial applications • How to identify faults on VSDs and how to rectify them • The key issues about flux vector control and how it can be used in drive applications • The main concepts in interfacing the control circuits of VSDs with PLCs/DCSs using serial data communications The structure of the book is as follows.
Chapter 1: Introduction. A review of the fundamentals in variable speed drives including motion concepts, torque speed curves, types of variable speed drives, mechanical variable speed drive methods and electrical variable speed drive methods. Chapter 2: 3-phase AC induction motors. These versatile and robust devices are the prime movers for the vast majority of machines. This chapter covers the basic construction, electrical and mechanical performance, motor acceleration, AC induction generator performance, efficiency of electric motors, rating of AC induction motors, duty cycles, cooling and ventilation, degree of protection of motor enclosures, methods of starting and motor selection.
xii Preface
Chapter 3: Power electronic converters. This chapter deals with the active components (e.g. diodes, thyristors, transistors) and passive components (e.g. resistors, chokes, capacitors) used in power electronic circuits and converters.
Chapter 4: Electromagnetic compatibility (EMC). Interference in circuits refers to the presence of unwanted voltages or currents in electrical equipment, which can damage the equipment or degrade its performance. The impact of variable speed drives can be severe and this chapter examines what causes interference and how to minimize its impact.
Chapter 5: Protection of AC converters and motors. The protection of AC variable speed drives includes the protection of the AC converter and the electric motor. The main methods of protection are examined.
Chapter 6: Control systems for AC variable speed drives. The overall control system can be divided into four main areas of the inverter control system, speed feedback and control system, current feedback and control system and the external interface.
Chapter 7: Selection of AC converters. Although manufacturers’ catalogs try to make it as easy as possible, there are many variables associated with the selection and rating of the optimum electric motor and AC converter for a VSD application. This chapter covers many of the principles for the correct selection for AC variable speed drives, which use pwm-type variable voltage variable frequency (VVVF) converters to control the speed of standard AC squirrel cage induction motors.
Chapter 8: Installation and commissioning. The main issues here of general installation and environmental requirements, power supply and earthing requirements, start/stop of AC drives, installing AC converters into metal enclosures, control wiring and commissioning variable speed drives.
Chapter 9: Special topics and new developments. Typical topics of soft-switching and the matrix converter are examined here.
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