Newnes Electrical Power Engineer’s Handbook Second Edition This page intentionally left blank Newnes Electrical Power Engineer’s Handbook Second Edition D.F. Warne AMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORD PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO Newnes is an imprint of Elsevier Newnes An imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 30 Corporate Drive, Burlington, MA 01803 First published 2005 Copyright © 2005, D.F. Warne. All rights reserved The right of D.F. Warne to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 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 Permissions may be sought directly from Elsevier’s Science and Technology Rights Department in Oxford, UK: phone: (+44) (0) 1865 843830; fax: (+44) (0) 1865 853333; e-mail: permissions@elsevier.co.uk. You may also complete your request on-line via the Elsevier homepage (http://www.elsevier.com), by selecting ‘Customer Support’ and then ‘Obtaining Permissions’ British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress ISBN 0 7506 6268 9 Printed and bound in Great Britain For information on all Elsevier publications visit our website at www.books.elsevier.com Contents Acknowledgements xvii 1 Introduction 1 2 Principles of electrical engineering 5 2.1 Nomenclature and units 5 2.2 Electromagnetic fields 5 2.2.1 Electric fields 5 2.2.2 Electric currents 7 2.2.3 Magnetic fields 9 2.2.4 Electromagnetism 11 2.3 Circuits 13 2.3.1 DC circuits 13 2.3.2 AC circuits 17 2.3.3 Magnetic circuits 21 2.4 Energy and power 22 2.4.1 Mechanical energy 22 2.4.2 Electrical energy 22 2.4.3 Per-unit notation 24 2.4.4 Energy transformation effects 25 3 Materials for electrical engineering 29 3.1 Introduction 29 3.2 Magnetic materials 29 3.2.1 Soft (high permeability) materials 31 3.2.1.1 Sheet steels 32 3.2.1.2 Amorphous alloys 33 3.2.1.3 Nickel iron alloys 34 3.2.1.4 Ferrites and garnets 34 3.2.1.5 Soft magnetic composites 35 3.2.2 Hard (permanent magnet) materials 35 3.2.2.1 Alnico alloys 35 3.2.2.2 Ferrites 35 3.2.2.3 Rare earth alloys 36 3.2.2.4 Bonded magnets 37 3.2.2.5 Applications 37 3.2.3 Other materials 38 3.2.4 Standards 39 3.3 Insulating materials 39 3.3.1 Solid dielectrics 41 3.3.1.1 Inorganic (ceramic and glass) materials 42 3.3.1.2 Plastic films 42 3.3.1.3 Flexible insulating sleeving 42 3.3.1.4 Rigid fibrous reinforced laminates 42 vi Contents 3.3.1.5 Resins and varnishes 43 3.3.1.6 Pressure-sensitive adhesive tapes 43 3.3.1.7 Cellulosic materials 43 3.3.1.8 Combined flexible materials 43 3.3.1.9 Mica products 43 3.3.1.10 Textile insulation 44 3.3.1.11 Elastomers and thermoplastics 44 3.3.2 Liquid dielectrics 46 3.3.3 Gas insulation 47 3.3.4 Vacuum insulation 48 3.3.5 Standards 48 3.4 Conducting materials 49 3.4.1 Conductors 49 3.4.1.1 Copper and its alloys 49 3.4.1.2 Aluminium and its alloys 53 3.4.1.3 Resistance alloys 54 3.4.2 Semiconductors 54 3.4.2.1 Impurity effects and doping 55 3.4.2.2 The transistor 57 3.4.2.3 Printed circuits and integrated circuits 58 3.4.2.4 The microprocessor 58 3.4.3 Superconductors 59 3.4.4 Standards 60 4 Measurements and instrumentation 63 4.1 Introduction 63 4.1.1 Definition of terms 63 4.1.2 Range, accuracy and error 63 4.1.3 Dynamic effects 64 4.1.4 Signals and standards 64 4.1.5 P&ID symbols 65 4.2 Pressure 65 4.2.1 The manometer 65 4.2.2 Elastic sensing elements 68 4.2.3 Piezo elements 68 4.3 Flow 70 4.3.1 Differential pressure flowmeters 70 4.3.2 Turbine flowmeters 72 4.3.3 Vortex shedding flowmeters 73 4.3.4 Electromagnetic flowmeters 74 4.3.5 Ultrasonic flowmeters 74 4.3.6 Mass flowmeters 75 4.4 Temperature 76 4.4.1 The thermocouple 76 4.4.2 The resistance thermometer 77 4.4.3 The pyrometer 77 4.5 Position 80 4.5.1 The potentiometer 80 4.5.2 The synchro and resolver 80 Contents vii 4.5.3 The linear variable differential transformer (LVDT) 82 4.5.4 The shaft encoder 82 4.5.5 The variable capacitance transducer 83 4.5.6 Laser distance measurement 84 4.5.7 Proximity switches and photocells 85 4.6 Level 85 4.6.1 The pressure-based system 85 4.6.2 Electrical probe 85 4.6.3 Ultrasonic transducers 86 4.6.4 Nucleonic methods 87 4.7 Weighing and force 88 4.7.1 Stress and strain 88 4.7.2 The strain gauge 89 4.7.3 Bridge circuits 89 4.7.4 The load cell 92 4.8 Acceleration and speed 92 4.8.1 Speed 92 4.8.2 Accelerometers and vibration transducers 93 4.9 Current 94 4.10 HART and Fieldbus 95 4.11 Data acquisition 96 4.12 Installation notes 102 5 Generators 105 5.1 Introduction 105 5.2 Main generator types 105 5.3 Principles of operation 107 5.3.1 No-load operation 107 5.3.2 The effect of load 112 5.3.3 Damping of transients 115 5.3.4 Voltage waveform 115 5.3.5 Connecting generators in parallel 117 5.3.6 Operating limits when in parallel with the mains 117 5.4 The Automatic Voltage Regulator (AVR) 118 5.5 Brushless excitation 119 5.5.1 Separate exciter 120 5.5.2 Capacitor excitation 122 5.5.3 Induction generator 123 5.5.4 Inductor alternator 125 5.6 Construction 126 5.6.1 Stator 126 5.6.2 Rotor 127 5.6.3 Cooling 128