Hughes Electrical and Electronic Technology PDF

HUGHES HUGHES HUGHES “This excellent book has become a legend over the years....

HUGHES HUGHES HUGHES “This excellent book has become a legend over the years. It is, undoubtedly, the most popular and the most useful book on the subject of electrical TENTH EDITION and electronic technology.” Dr Naren Gupta, Napier University “In terms of giving an insight into electrical and electronic engineering, Dr John Hiley and Dr Keith Brown are this book is excellent.” both lecturers in the Department of Electrical, Dr Michael Lampérth, Imperial College London Electronic and Computer Engineering at TECHNOLOGY TENTH EDITION ELECTRICAL AND ELECTRONIC Heriot-Watt University. The late Edward Hughes was Vice Principal and Head of the Engineering Department, Brighton College of Technology. All engineers need to understand the fundamental principles of electrical and electronic technology. The tenth edition of this best-selling text offers ELEC TRICAL AND ELEC TRONIC TECHNOLOGY TENTH EDITION He was a fellow of Heriot-Watt University. a clear and comprehensive introduction to the area with balanced coverage of electrical, electronic, and power engineering. This revision has been updated to The late Ian McKenzie Smith was formerly take into account key developments in the subject, including a new chapter on Deputy Principal, Stow College, Glasgow. Electrical Energy Systems – an important addition which explores (among other topics) the principles of sustainable electricity generation. Hughes Electrical and Electronic Technology is a must-have text for all university and college engineering students requiring a comprehensive introduction to electrical and electronic engineering. It is also appropriate as a reference for any practitioners and technicians working in this, or any other engineering discipline. Key features l New chapter on Electrical Energy Systems l Extended chapters on: Fibreoptics; Induction Motors; and Operational Amplifiers JOHN HILEY, KEITH BROWN AND IAN McKENZIE SMITH l Additional worked examples and end-of-chapter problems to help reinforce learning and test understanding l Retains its established features of chapter objectives, highlighted key equations, summaries of formulae, and key terms and concepts Cover image © Getty Images REVISED BY JOHN HILEY, KEITH BROWN www.pearson-books.com AND IAN McKENZIE SMITH CVR_HUGH0110_10_SE_CVR.indd 1 30/4/08 10:59:11 ELEA_A01_Q4.qxd 5/13/08 9:39 Page i HUGHES ELECTRICAL AND ELECTRONIC TECHNOLOGY ELEA_A01_Q4.qxd 5/13/08 9:39 Page ii We work with leading authors to develop the strongest educational materials in engineering, bringing cutting-edge thinking and best learning practice to a global market. Under a range of well-known imprints, including Prentice Hall, we craft high quality print and electronic publications which help readers to understand and apply their content, whether studying or at work. To find out more about the complete range of our publishing please visit us on the World Wide Web at: www.pearsoned.co.uk ELEA_A01_Q4.qxd 5/13/08 9:39 Page iii HUGHES ELECTRICAL AND ELECTRONIC TECHNOLOGY tenth edition EDWARD HUGHES Revised by John Hiley, Keith Brown and Ian McKenzie Smith ELEA_A01.qxd 5/19/08 11:38 AM Page iv Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England and Associated Companies throughout the world Visit us on the World Wide Web at: www.pearsoned.co.uk First published under the Longman imprint 1960 Tenth edition 2008 © Pearson Education Limited 1960, 2005, 2008 The right of Edward Hughes to be identified as author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior written permission of the publisher or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, Saffron House, 6–10 Kirby Street, London, EC1N 8TS. ISBN: 978-0-13-206011-0 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Library of Congress Cataloging-in-Publication Data Hughes, Edward, 1888– Hughes electrical and electronic technology / Edward Hughes ; revised by John Hiley, Keith Brown, and Ian McKenzie Smith. – 10th ed. p. cm ISBN 978-0-13-206011-0 1. Electric engineering – Textbooks. 2. Electronics – Textbooks. I. Hiley, John. II. Brown, Keith, 1962– III. Smith, Ian McKenzie. IV. Title. Tk146.H9 2008 621.3–dc22 2008017741 10 9 8 7 6 5 4 3 2 1 12 11 10 09 08 Typeset in 10/11pt Ehrhardt MT by 35 Printed and bound by Ashford Colour Press Ltd., Gosport ·· ELEA_A01_Q4.qxd 5/13/08 9:39 Page v Short contents Prefaces xvii 27 Microprocessors and Programs 558 28 Control Systems 590 29 Signals 603 Section 1 Electrical Principles 1 30 Data Transmission and Signals 622 31 Communications 634 1 International System of Measurement 3 32 Fibreoptics 647 2 Introduction to Electrical Systems 12 3 Simple DC Circuits 30 4 Network Theorems 61 Section 3 Power Engineering 657 5 Capacitance and Capacitors 92 6 Electromagnetism 132 33 Multiphase Systems 659 7 Simple Magnetic Circuits 147 34 Transformers 680 8 Inductance in a DC Circuit 162 35 Introduction to Machine Theory 714 9 Alternating Voltage and Current 197 36 AC Synchronous Machine Windings 736 10 Single-phase Series Circuits 222 37 Characteristics of AC Synchronous 11 Single-phase Parallel Networks 243 Machines 749 12 Power in AC Circuits 259 38 Induction Motors 760 13 Complex Notation 273 39 Electrical Energy Systems 791 14 Resonance in AC Circuits 298 40 Power Systems 835 15 Network Theorems Applied to AC Networks 321 41 Direct-current Machines 855 42 Direct-current Motors 869 43 Control System Motors 886 Section 2 Electronic Engineering 349 44 Motor Selection and Efficiency 896 45 Power Electronics 915 16 Electronic Systems 351 17 Passive Filters 358 18 Amplifier Equivalent Networks 387 Section 4 Measurements 933 19 Semiconductor Materials 407 20 Rectifiers 419 46 Electronic Measuring Instruments 935 21 Junction Transistor Amplifiers 433 47 Analogue Measuring Instruments 955 22 FET Amplifiers 464 23 Further Semiconductor Amplifiers 474 Appendix: Symbols, Abbreviations, Definitions 24 Interfacing Digital and Analogue Systems 490 and Diagrammatic Symbols 979 25 Digital Numbers 508 Answers to Exercises 984 26 Digital Systems 523 Index 995 ELEA_A01_Q4.qxd 5/13/08 9:39 Page vi ·· ELEA_A01_Q4.qxd 5/13/08 9:39 Page vii Contents Prefaces xvii 3.4 Kirchhoff’s laws 42 3.5 Power and energy 49 Section 1 Electrical Principles 1 3.6 Resistivity 52 3.7 Temperature coefficient of resistance 54 3.8 Temperature rise 56 1 International System of Measurement 3 Summary of important formulae 57 Terms and concepts 58 1.1 The International System 4 1.2 SI derived units 5 1.3 Unit of turning moment or torque 6 1.4 Unit of work or energy 7 4 Network Theorems 61 1.5 Unit of power 8 1.6 Efficiency 9 4.1 New circuit analysis techniques 62 1.7 Temperature 10 4.2 Kirchhoff’s laws and network solution 62 Summary of important formulae 10 4.3 Mesh analysis 70 Terms and concepts 11 4.4 Nodal analysis 72 4.5 Superposition theorem 75 4.6 Thévenin’s theorem 77 2 Introduction to Electrical Systems 12 4.7 The constant-current generator 81 4.8 Norton’s theorem 84 2.1 Electricity and the engineer 13 4.9 Delta–star transformation 86 2.2 An electrical system 13 4.10 Star–delta transformation 87 2.3 Electric charge 15 4.11 Maximum power transfer 88 2.4 Movement of electrons 15 Summary of important formulae 89 2.5 Current flow in a circuit 16 Terms and concepts 89 2.6 Electromotive force and potential difference 16 2.7 Electrical units 17 2.8 Ohm’s law 20 5 Capacitance and Capacitors 92 2.9 Resistors 22 2.10 Resistor coding 23 5.1 Capacitors 93 2.11 Conductors and insulators 25 5.2 Hydraulic analogy 94 2.12 The electric circuit in practice 26 5.3 Charge and voltage 95 Summary of important formulae 27 5.4 Capacitance 95 Terms and concepts 28 5.5 Capacitors in parallel 96 5.6 Capacitors in series 96 5.7 Distribution of voltage across capacitors 3 Simple DC Circuits 30 in series 97 5.8 Capacitance and the capacitor 98 3.1 Series circuits 31 5.9 Electric fields 99 3.2 Parallel networks 36 5.10 Electric field strength and electric flux density 99 3.3 Series circuits versus parallel networks 41 5.11 Relative permittivity 101 ELEA_A01_Q4.qxd 5/13/08 9:39 Page viii viii CONTENTS 5.12 Capacitance of a multi-plate capacitor 102 5.13 Composite-dielectric capacitors 103 8 Inductance in a DC Circuit 162 5.14 Charging and discharging currents 106 5.15 Growth and decay 107 8.1 Inductive and non-inductive circuits 163 5.16 Analysis of growth and decay 109 8.2 Unit of inductance 164 5.17 Discharge of a capacitor through a resistor 112 8.3 Inductance in terms of flux-linkages 5.18 Transients in CR networks 114 per ampere 166 5.19 Energy stored in a charged capacitor 119 8.4 Factors determining the inductance of a coil 169 5.20 Force of attraction between oppositely 8.5 Ferromagnetic-cored inductor in a d.c. circuit 171 charged plates 120 8.6 Growth in an inductive circuit 172 5.21 Dielectric strength 121 8.7 Analysis of growth 175 5.22 Leakage and conduction currents in 8.8 Analysis of decay 177 capacitors 122 8.9 Transients in LR networks 179 5.23 Displacement current in a dielectric 123 8.10 Energy stored in an inductor 182 5.24 Types of capacitor and capacitance 123 8.11 Mutual inductance 185 Summary of important formulae 126 8.12 Coupling coefficient 188 Terms and concepts 127 8.13 Coils connected in series 189 8.14 Types of inductor and inductance 191 Summary of important formulae 192 Terms and concepts 193 6 Electromagnetism 132 6.1 Magnetic field 133 9 Alternating Voltage and Current 197 6.2 Direction of magnetic field 133 6.3 Characteristics of lines of magnetic flux 133 9.1 Alternating systems 198 6.4 Magnetic field due to an electric current 134 9.2 Generation of an alternating e.m.f. 198 6.5 Magnetic field of a solenoid 135 9.3 Waveform terms and definitions 202 6.6 Force on a current-carrying conductor 136 9.4 Relationship between frequency, speed and 6.7 Force determination 138 number of pole pairs 204 6.8 Electromagnetic induction 140 9.5 Average and r.m.s. values of an alternating 6.9 Direction of induced e.m.f. 140 current 204 6.10 Magnitude of the generated or induced e.m.f. 141 9.6 Average and r.m.s. values of sinusoidal 6.11 Magnitude of e.m.f. induced in a coil 143 currents and voltages 206 Summary of important formulae 145 9.7 Average and r.m.s. values of non-sinusoidal Terms and concepts 145 currents and voltages 211 9.8 Representation of an alternating quantity by a phasor 212 7 Simple Magnetic Circuits 147 9.9 Addition and subtraction of sinusoidal alternating quantities 214 7.1 Introduction to magnetic circuits 148 9.10 Phasor diagrams drawn with r.m.s. 7.2 Magnetomotive force and magnetic values instead of maximum values 216 field strength 148 9.11 Alternating system frequencies in practice 217 7.3 Permeability of free space or magnetic Summary of important formulae 218 constant 149 Terms and concepts 218 7.4 Relative permeability 151 7.5 Reluctance 153 7.6 ‘Ohm’s law for a magnetic circuit’ 153 10 Single-phase Series Circuits 222 7.7 Determination of the B/H characteristic 156 7.8 Comparison of electromagnetic and 10.1 Basic a.c. circuits 223 electrostatic terms 158 10.2 Alternating current in a resistive circuit 223 Summary of important formulae 159 10.3 Alternating current in an inductive circuit 224 Terms and concepts 159 10.4 Current and voltage in an inductive circuit 226 ELEA_A01_Q4.qxd 5/13/08 9:39 Page ix CONTENTS ix 10.5 Mechanical analogy of an inductive circuit 228 13.12 Parallel loads 292 10.6 Resistance and inductance in series 229 Summary of important formulae 294 10.7 Alternating current in a capacitive circuit 232 Terms and concepts 295 10.8 Current and voltage in a capacitive circuit 233 10.9 Analogies of a capacitance in an a.c. circuit 234 14 Resonance in AC Circuits 298 10.10 Resistance and capacitance in series 234 10.11 Alternating current in an RLC circuit 236 14.1 Introduction 299 Summary of important formulae 240 14.2 Frequency variation in a series RLC circuit 299 Terms and concepts 241 14.3 The resonant frequency of a series RLC circuit 302 14.4 The current in a series RLC circuit 302 14.5 Voltages in a series RLC circuit 302 11 Single-phase Parallel Networks 243 14.6 Quality factor Q 303 14.7 Oscillation of energy at resonance 305 11.1 Basic a.c. parallel circuits 244 14.8 Mechanical analogy of a resonant circuit 306 11.2 Simple parallel circuits 244 14.9 Series resonance using complex notation 306 11.3 Parallel impedance circuits 248 14.10 Bandwidth 307 11.4 Polar impedances 252 14.11 Selectivity 309 11.5 Polar admittances 255 14.12 Parallel resonance 312 Summary of important formulae 257 14.13 Current magnification 313 Terms and concepts 257 14.14 Parallel and series equivalents 314 14.15 The two-branch parallel resonant circuit 315 Summary of important formulae 318 12 Power in AC Circuits 259 Terms and concepts 318 12.1 The impossible power 260 12.2 Power in a resistive circuit 260 15 Network Theorems Applied to AC 12.3 Power in a purely inductive circuit 261 Networks 321 12.4 Power in a purely capacitive circuit 263 12.5 Power in a circuit with resistance and 15.1 One stage further 322 reactance 264 15.2 Kirchhoff’s laws and network solution 322 12.6 Power factor 266 15.3 Nodal analysis (Node Voltage method) 329 12.7 Active and reactive currents 268 15.4 Superposition theorem 329 12.8 The practical importance of power factor 270 15.5 Thévenin’s theorem 331 12.9 Measurement of power in a single-phase 15.6 Norton’s theorem 336 circuit 271 15.7 Star–delta transformation 340 Summary of important formulae 271 15.8 Delta–star transformation 341 Terms and concepts 271 15.9 Maximum power transfer 343 Terms and concepts 344 13 Complex Notation 273 Section 2 Electronic Engineering 349 13.1 The j operator 274 13.2 Addition and subtraction of phasors 275 16 Electronic Systems 351 13.3 Voltage, current and impedance 276 13.4 Admittance, conductance and susceptance 279 16.1 Introduction to systems 352 13.5 RL series circuit admittance 280 16.2 Electronic systems 353 13.6 RC series circuit admittance 280 16.3 Basic amplifiers 353 13.7 Parallel admittance 281 16.4 Basic attenuators 356 13.8 Calculation of power using complex notation 285 16.5 Block diagrams 356 13.9 Power and voltamperes 286 16.6 Layout of block diagrams 357 13.10 Complex power 287 Summary of important formulae 357 13.11 Power factor improvement or correction 291 Terms and concepts 357 ELEA_A01_Q4.qxd 5/13/08 9:39 Page x x CONTENTS 20.6 Zener diode 429 17 Passive Filters 358 Summary of important formulae 430 Terms and concepts 431 17.1 Introduction 359 17.2 Types of filter 359 17.3 Frequency response 361 21 Junction Transistor Amplifiers 433 17.4 Logarithms 361 17.5 Log scales 364 21.1 Introduction 434 17.6 The decibel (dB) 365 21.2 Bipolar junction transistor 434 17.7 The low-pass or lag circuit 368 21.3 Construction of a bipolar transistor 435 17.8 The high-pass or lead circuit 372 21.4 Common-base and common-emitter circuits 435 17.9 Passband (or bandpass) filter 375 21.5 Static characteristics for a common-base 17.10 Stopband (or bandstop) filters 378 circuit 436 17.11 Bode plots 378 21.6 Static characteristics for a common-emitter Summary of important formulae 384 circuit 437 Terms and concepts 385 21.7 Relationship between α and β 438 21.8 Load line for a transistor 439 18 Amplifier Equivalent Networks 387 21.9 Transistor as an amplifier 441 21.10 Circuit component selection 447 21.11 Equivalent circuits of a transistor 448 18.1 Amplifier constant-voltage equivalent networks 388 21.12 Hybrid parameters 452 18.2 Amplifier constant-current equivalent networks 390 21.13 Limitations to the bipolar junction transistor 453 18.3 Logarithmic units 392 21.14 Stabilizing voltage supplies 454 18.4 Frequency response 395 21.15 Transistor as a switch 458 18.5 Feedback 397 Summary of important formulae 458 18.6 Effect of feedback on input and output Terms and concepts 459 resistances 401 18.7 Effect of feedback on bandwidth 403 18.8 Distortion 403 22 FET Amplifiers 464 Summary of important formulae 404 Terms and concepts 404 22.1 Field effect transistor (FET) 465 22.2 JUGFET 465 19 Semiconductor Materials 407 22.3 IGFET 467 22.4 Static characteristics of a FET 469 19.1 Introduction 408 22.5 Equivalent circuit of a FET 469 19.2 Atomic structure 408 22.6 The FET as a switch 471 19.3 Covalent bonds 409 Summary of important formulae 472 19.4 An n-type semiconductor 411 Terms and concepts 472 19.5 A p-type semiconductor 412 19.6 Junction diode 413 19.7 Construction and static characteristics of a 23 Further Semiconductor Amplifiers 474 junction diode 416 Terms and concepts 418 23.1 Cascaded amplifiers 475 23.2 Integrated circuits 479 23.3 Operational amplifiers 480 20 Rectifiers 419 23.4 The inverting operational amplifier 481 23.5 The summing amplifier 482 20.1 Rectifier circuits 420 23.6 The non-inverting amplifier 484 20.2 Half-wave rectifier 420 23.7 Differential amplifiers 485 20.3 Full-wave rectifier network 423 23.8 Common-mode rejection ratio 486 20.4 Bridge rectifier network 424 Summary of important formulae 487 20.5 Smoothing 427 Terms and concepts 487 ELEA_A01_Q4.qxd 5/13/08 9:39 Page xi CONTENTS xi 26.14 Timing diagrams 542 24 Interfacing Digital and Analogue 26.15 Combinational and sequential logic circuits 543 Systems 490 26.16 Synchronous and asynchronous sequential circuits 543 24.1 The need for conversion 491 26.17 Basic storage elements 544 24.2 Digital-to-analogue conversion 491 26.18 Integrated circuit logic gates 552 24.3 D/A converter hardware 494 Summary of important formulae 553 24.4 D/A converters in practice 496 Terms and concepts 554 24.5 R/2R ladder D/A converter 498 24.6 Analogue-to-digital conversion 499 24.7 Simple comparator 501 24.8 A/D converters 502 27 Microprocessors and Programs 558 24.9 Converters in action 504 Terms and concepts 505 27.1 Microprocessors 559 27.2 Microprocessor operation 559 27.3 Microprocessor control 562 27.4 Programs 566 25 Digital Numbers 508 27.5 Simple programs 569 27.6 Control programs 571 25.1 Introduction 509 27.7 Programming in hexadecimal 25.2 Binary numbers 509 representation 573 25.3 Decimal to binary conversion 510 27.8 The programmable logic controller 576 25.4 Binary addition 511 27.9 Control system characteristics 577 25.5 Binary subtraction 512 27.10 Flexibility of PLCs 577 25.6 Binary multiplication 512 27.11 Inside a PLC 578 25.7 Binary division 513 27.12 The PLC program 579 25.8 Negative binary numbers 515 27.13 Input devices 581 25.9 Signed binary addition 516 27.14 Outputs 582 25.10 Signed binary subtraction 517 27.15 A practical application 582 25.11 Signed binary multiplication 518 Terms and concepts 587 25.12 Signed binary division 519 25.13 The octal system 520 25.14 Hexadecimal numbers 521 Terms and concepts 522 28 Control Systems 590 28.1 Introduction 591 28.2 Open-loop and closed-loop systems 592 26 Digital Systems 523 28.3 Automation 593 28.4 Components of a control system 593 26.1 Introduction to logic 524 28.5 Transfer function 594 26.2 Basic logic statements or functions 524 28.6 Regulators and servomechanisms 595 26.3 The OR function 524 28.7 In transient periods 597 26.4 The AND function 525 28.8 Damping 598 26.5 The EXCLUSIVE-OR function 525 Terms and concepts 601 26.6 The NOT function 526 26.7 Logic gates 526 26.8 The NOR function 527 26.9 The NAND function 527 29 Signals 603 26.10 Logic networks 528 26.11 Combinational logic 529 29.1 Classification of signals 604 26.12 Gate standardization 532 29.2 Representation of a signal by a continuum 26.13 Karnaugh maps for simplifying of impulses 610 combinational logic 535 29.3 Impulse response 612 ELEA_A01_Q4.qxd 5/13/08 9:39 Page xii xii CONTENTS 29.4 Convolution sum for discrete-time systems 612 Section 3 Power Engineering 657 29.5 Convolution integral for continuous-time systems 615 29.6 Deconvolution 616 33 Multiphase Systems 659 29.7 Relation between impulse response and unit 33.1 Disadvantages of the single-phase system 660 step response 617 33.2 Generation of three-phase e.m.f.s 660 29.8 Step and impulse responses of discrete-time 33.3 Delta connection of three-phase windings 661 systems 618 33.4 Star connection of three-phase windings 662 Summary of important formulae 619 33.5 Voltages and currents in a star-connected Terms and concepts 620 system 665 33.6 Voltages and currents in a delta-connected system 666 30 Data Transmission and Signals 622 33.7 Power in a three-phase system with a balanced load 669 33.8 Measurement of active power in a 30.1 Transmission of information 623 three-phase, three-wire system 670 30.2 Analogue signals 623 33.9 Power factor measurement by means of 30.3 Digital signals 624 two wattmeters 672 30.4 Bandwidth 626 33.10 Two-phase systems 675 30.5 Modulation 627 Summary of important formulae 676 30.6 Filters 629 Terms and concepts 677 30.7 Demodulation 630 30.8 Amplifying signals 631 30.9 Digital or analogue? 632 34 Transformers 680 Terms and concepts 633 34.1 Introduction 681 34.2 Core factors 681 34.3 Principle of action of a transformer 682 31 Communications 634 34.4 EMF equation of a transformer 683 34.5 Phasor diagram for a transformer on no load 685 31.1 Basic concepts 635 34.6 Phasor diagram for an ideal loaded 31.2 Information theory for source coding 637 transformer 687 31.3 Data communications systems 639 34.7 Useful and leakage fluxes in a transformer 689 31.4 Coding for efficient transmission 640 34.8 Leakage flux responsible for the inductive 31.5 Source coding 643 reactance of a transformer 691 Summary of important formulae 645 34.9 Methods of reducing leakage flux 691 Terms and concepts 645 34.10 Equivalent circuit of a transformer 692 34.11 Phasor diagram for a transformer on load 693 34.12 Approximate equivalent circuit of a transformer 694 32 Fibreoptics 647 34.13 Simplification of the approximate equivalent circuit of a transformer 695 32.1 Introduction 648 34.14 Voltage regulation of a transformer 696 32.2 Fibre loss 648 34.15 Efficiency of a transformer 700 32.3 Refraction 649 34.16 Condition for maximum efficiency of a 32.4 Light acceptance 651 transformer 701 32.5 Attenuation 652 34.17 Open-circuit and short-circuit tests on a 32.6 Bandwidth 652 transformer 703 32.7 Modulation 653 34.18 Calculation of efficiency from the 32.8 Optical fibre systems 654 open-circuit and short-circuit tests 704 Summary of important formulae 655 34.19 Calculation of the voltage regulation from Terms and concepts 656 the short-circuit test 704 ELEA_A01_Q4.qxd 5/13/08 9:39 Page xiii CONTENTS xiii 34.20 Three-phase core-type transformers 706 37.5 Three-phase synchronous motor: 34.21 Auto-transformers 706 principle of action 757 34.22 Current transformers 707 37.6 Advantages and disadvantages of the 34.23 Waveform of the magnetizing current of synchronous motor 757 a transformer 708 Terms and concepts 758 34.24 Air-cored transformer 709 Summary of important formulae 710 Terms and concepts 710 38 Induction Motors 760 38.1 Principle of action 761 35 Introduction to Machine Theory 714 38.2 Frequency of rotor e.m.f. and current 762 38.3 The equivalent circuit of the three-phase 35.1 The role of the electrical machine 715 induction motor 763 35.2 Conversion process in a machine 715 38.4 Mechanical power and torque 769 35.3 Methods of analysis of machine performance 717 38.5 The torque/speed curve and effect of 35.4 Magnetic field energy 718 rotor resistance 773 35.5 Simple analysis of force of alignment 719 38.6 Experimental tests to obtain motor 35.6 Energy balance 720 equivalent circuit parameters 775 35.7 Division of converted energy and power 723 38.7 Starting torque 780 35.8 Force of alignment between parallel 38.8 Starting of a three-phase induction motor magnetized surfaces 724 fitted with a cage rotor 781 35.9 Rotary motion 727 38.9 Comparison of cage and slip-ring rotors 782 35.10 Reluctance motor 728 38.10 Braking 782 35.11 Doubly excited rotating machines 730 38.11 Single-phase induction motors 783 Summary of important formulae 732 38.12 Capacitor-run induction motors 785 Terms and concepts 732 38.13 Split-phase motors 786 38.14 Shaded-pole motors 786 38.15 Variable speed operation of induction motors 787 36 AC Synchronous Machine Windings 736 Summary of important formulae 788 Terms and concepts 788 36.1 General arrangement of synchronous machines 737 36.2 Types of rotor construction 737 36.3 Stator windings 739 39 Electrical Energy Systems 791 36.4 Expression for the e.m.f. of a stator winding 742 36.5 Production of rotating magnetic flux by 39.1 Energy units 792 three-phase currents 742 39.2 Forms of energy 792 36.6 Analysis of the resultant flux due to 39.3 Energy conversion and quality of three-phase currents 744 energy 792 36.7 Reversal of direction of rotation of the 39.4 Demand for electricity and the National Grid 796 magnetic flux 746 39.5 Generating plant 801 Summary of important formulae 747 39.6 Nuclear power 805 Terms and concepts 747 39.7 Renewable energy 807 39.8 Distributed/Embedded generation 829 39.9 The cost of generating electricity 830 Summary of important formulae 832 37 Characteristics of AC Synchronous Terms and concepts 833 Machines 749 37.1 Armature reaction in a three-phase 40 Power Systems 835 synchronous generator 750 37.2 Voltage regulation of a synchronous generator 751 40.1 System representation 836 37.3 Synchronous impedance 752 40.2 Power system analysis 837 37.4 Parallel operation of synchronous generators 755 40.3 Voltage-drop calculations 838 ELEA_A01_Q4.qxd 5/13/08 9:39 Page xiv xiv CONTENTS 40.4 The per-unit method 841 44.5 The motor and its environment 900 40.5 Per-unit impedance 842 44.6 Machine efficiency 901 40.6 Base power – SB or MV AB 844 44.7 Hysteresis 902 40.7 Faults in a power system 847 44.8 Current-ring theory of magnetism 902 40.8 Representation of a grid connection 850 44.9 Hysteresis loss 904 Summary of important formulae 852 44.10 Losses in motors and generators 907 Terms and concepts 852 44.11 Efficiency of a d.c. motor 909 44.12 Approximate condition for maximum efficiency 910 41 Direct-current Machines 855 44.13 Determination of efficiency 910 Terms and concepts 913 41.1 General arrangement of a d.c. machine 856 41.2 Double-layer drum windings 857 41.3 Calculation of e.m.f. generated in an armature 45 Power Electronics 915 winding 860 41.4 Armature reaction 861 45.1 Introductory 916 41.5 Armature reaction in a d.c. motor 864 45.2 Thyristor 916 41.6 Commutation 865 45.3 Some thyristor circuits 918 Summary of important formulae 867 45.4 Limitations to thyristor operation 920 Terms and concepts 867 45.5 The thyristor in practice 920 45.6 The fully controlled a.c./d.c. converter 920 45.7 AC/DC inversion 921 42 Direct-current Motors 869 45.8 Switching devices in inverters 924 45.9 Three-phase rectifier networks 925 42.1 Armature and field connections 870 45.10 The three-phase fully controlled converter 927 42.2 A d.c. machine as generator or motor 870 45.11 Inverter-fed induction motors 927 42.3 Speed of a motor 872 45.12 Soft-starting induction motors 928 42.4 Torque of an electric motor 873 45.13 DC to d.c. conversion switched-mode 42.5 Speed characteristics of electric motors 875 power supplies 929 42.6 Torque characteristics of electric motors 876 Summary of important formulae 931 42.7 Speed control of d.c. motors 877 Terms and concepts 932 Summary of important formulae 883 Terms and concepts 883 Section 4 Measurements 933 43 Control System Motors 886 43.1 Review 887 46 Electronic Measuring Instruments 935 43.2 Motors for regulators 887 43.3 RPC system requirements 888 46.1 Introduction to analogue and electronic 43.4 Geneva cam 889 instruments 936 43.5 The stepping (or stepper) motor 889 46.2 Digital electronic voltmeters 937 43.6 The variable-reluctance motor 890 46.3 Digital electronic ammeters and 43.7 The hybrid stepping motor 891 wattmeters 939 43.8 Drive circuits 893 46.4 Graphical display devices 939 Terms and concepts 894 46.5 The two-electrode vacuum device 940 46.6 Control of the anode current 941 46.7 Cathode-ray tube 941 44 Motor Selection and Efficiency 896 46.8 Deflecting systems of a cathode-ray tube 942 46.9 Cathode-ray oscilloscope 943 44.1 Selecting a motor 897 46.10 Use of the cathode-ray oscilloscope in 44.2 Speed 897 waveform measurement 947 44.3 Power rating and duty cycles 898 46.11 Digital oscilloscope 953 44.4 Load torques 899 Terms and concepts 953 ELEA_A01_Q4.qxd 5/13/08 9:39 Page xv CONTENTS xv 47.11 The potentiometer 966 47 Analogue Measuring Instruments 955 47.12 A commercial form of potentiometer 967 47.13 Standardization of the potentiometer 968 47.1 Introduction 956 47.14 Calibration of an ammeter by means of a 47.2 Electrical analogue indicating instruments 956 potentiometer 968 47.3 Controlling devices 957 47.15 Calibration accuracy and errors 968 47.4 Damping devices 957 47.16 Determination of error due to instrument 47.5 Permanent-magnet moving-coil ammeters errors 971 and voltmeters 958 Terms and concepts 976 47.6 Thermocouple instruments 962 47.7 Electrodynamic (or dynamometer) instruments 962 47.8 Electrostatic voltmeters 964 Appendix: Symbols, Abbreviations, Definitions 47.9 Rectifier ammeters and voltmeters 964 and Diagrammatic Symbols 979 47.10 Measurement of resistance by the Answers to Exercises 984 Wheatstone bridge 965 Index 995 ELEA_A01_Q4.qxd 5/13/08 9:39 Page xvi ELEA_A01_Q4.qxd 5/13/08 9:39 Page xvii Preface to the Tenth Edition As the tenth edition is in course of preparation, one is reminded, almost daily, of impending energy shortages and of the consequences for the environment of using energy. In particular, the ways in which electricity is generated are the subject of fierce debate. The environmentally conscious champion the merits of renewable sources of electrical energy such as wind, wave or tidal power. Pragmatists currently seem to favour the replacement of fossil fuel fired stations by nuclear generation, but this raises conflicting environmental issues; the benefits of much reduced CO2 emissions but at the cost of radioactive waste. It is only too clear that Electrical and Electronic Engineers have a vital part to play in any future solutions for electrical energy supply, and to that end the tenth edition includes a new chapter on electrical energy systems. This chapter seeks to introduce students to the topics of conventional and sustainable electricity generation technology and to highlight in a compar- ative manner some of the problems and merits associated with the many dif- ferent techniques. It includes a brief introduction to the topic of integrating small renewable sources into large power systems. There is, in addition, much other new material. There are updates to the electronics chapters on operational amplifiers, sequential logic and counters, microprocessors, fibreoptics, switchmode power supplies and digital oscillo- scopes. The electrical sections have been strengthened too with new material on Ohm’s Law for a magnetic circuit, on complex power, the power triangle and power factor correction. The chapter on the induction motor has been substantially revised and now includes an extensive section on the induction motor equivalent circuit with new worked examples. Finally, we would like to acknowledge the support of our families during the course of the preparation of this new edition which is dedicated to our children: Robin and Helen; Ben, Rachel and Megan. John Hiley Keith Brown Heriot Watt University, Edinburgh June 2008 ELEA_A01_Q4.qxd 5/13/08 9:39 Page xviii Preface to the First Edition This volume covers the electrical engineering syllabuses of the Second and Third Year Courses for the Ordinary National Certificate in Electrical En- gineering and of the First Year Course leading to a Degree of Engineering. The rationalized M.K.S. system of units has been used throughout this book. The symbols, abbreviations and nomenclature are in accordance with the recommendations of the British Standards Institution; and, for the con- venience of students, the symbols and abbreviations used in this book have been tabulated in the Appendix. It is impossible to acquire a thorough understanding of electrical principles without working out a large number of numerical problems; and while doing this, students should make a habit of writing the solutions in an orderly man- ner, attaching the name of the unit wherever possible. When students tackle problems in examinations or in industry, it is important that they express their solutions in a way that is readily intelligible to others, and this facility can only be acquired by experience. Guidance in this respect is given by the 106 worked examples in the text, and the 670 problems afford ample oppor- tunity for practice. Most of the questions have been taken from examination papers; and for permission to reproduce these questions I am indebted to the University of London, the East Midland Educational Union, the Northern Counties Technical Examination Council, the Union of Educational Institutions and the Union of Lancashire and Cheshire Institutes. I wish to express my thanks to Dr F. T. Chapman, C.B.E., M.I.E.E., and Mr E. F. Piper, A.M.I.E.E., for reading the manuscript and making valuable suggestions. Edward Hughes Hove April 1959 ELEA_A01_Q4.qxd 5/13/08 9:40 Page xix Publisher’s acknowledgements We are grateful to the following for permission to reproduce copyright material: Figure 38.18: Martin Bond/Science Photo Library; Table 39.11: Royal Academy of Engineering, 2004 (www.raeng.org.uk/policy/reports/ electricityreports.htm). Copyright © Royal Academy of Engineering repro- duced with permission. In some instances we have been unable to trace the owners of copyright material, and we would appreciate any information that would enable us to do so. ELEA_A01_Q4.qxd 5/13/08 9:40 Page xx ELEA_C01_Q4.qxd 5/13/08 9:42 Page 1 Section one Electrical Principles 1 International System of Measurement 2 Introduction to Electrical Systems 3 Simple DC Circuits 4 Network Theorems 5 Capacitance and Capacitors 6 Electromagnetism 7 Simple Magnetic Circuits 8 Inductance in a DC Circuit 9 Alternating Voltage and Current 10 Single-phase Series Circuits 11 Single-phase Parallel Networks 12 Power in AC Circuits 13 Complex Notation 14 Resonance in AC Circuits 15 Network Theorems Applied to AC Networks ELEA_C01_Q4.qxd 5/13/08 9:42 Page 2 ·· ELEA_C01_Q4.qxd 5/13/08 9:43 Page 3 Chapter one International System of Measurement Objectives Contents When you have studied this chapter, you should 1.1 The International be familiar with the International System of Measurement System 4 be familiar with a variety of derived SI units 1.2 SI derived units 5 be aware of the concepts of torque and turning moment 1.3 Unit of turning moment or torque 6 be capable of analysing simple applications of the given SI units 1.4 Unit of work or have an understanding of work, energy and power energy 7 be capable of analysing simple applications involving work, energy 1.5 Unit of power 8 and power 1.6 Efficiency 9 have an understanding of efficiency and its relevance to energy and 1.7 Temperature 10 power Summary of important be capable of analysing the efficiency of simple applications formulae 10 have an understanding of temperature and its units of measurement Terms and concepts 11 Electrical technology is a subject which is closely related to the technologies of mechanics, heat, light and sound. For instance, we use electrical motors to drive machines such as cranes, we use electric heaters to keep us warm, we use electric lamp bulbs perhaps to read this book and we use electric radios to listen to our favourite music. At this introductory stage, let us assume that we have some understanding of physics in general and, in particular, let us assume that we have some understanding of the basic mechanics which form part of any study of physics. It is not necessary to have an extensive knowledge, and in this chapter we shall review the significant items of which you should have an understanding. We shall use these to develop an appreciation of electrical technology. In particular, we shall be looking at the concepts of work, energy and power since the underlying interest that we have in electricity is the delivery of energy to a point of application. Thus we drive an electric train yet the power source is in a generating station many kilometres away, or we listen to a voice on the phone speaking with someone possibly on the other side of the world. It is electricity which delivers the energy to make such things happen. ELEA_C01_Q4.qxd 5/13/08 9:43 Page 4 4 SECTION 1 ELECTRICAL PRINCIPLES 1.1 The International The International System of Units, known as SI in every language, was System formally introduced in 1960 and has been accepted by most countries as their only legal system of measurement. One of the SI’s most important advantages over its predecessors is that it is a coherent system wherever possible. A system is coherent if the product or quotient of any two quantities is the unit of the resultant quantity. For example, unit area results when unit length is multiplied by unit length. Similarly unit velocity results when unit length or distance is divided by unit time. The SI is based on the measures of six physical quantities: Mass Length Time Electric current Absolute temperature Luminous intensity All other units are derived units and are related to these base units by definition. If we attempt to analyse relationships between one unit and another, this can be much more readily achieved by manipulating symbols, e.g. A for areas, W for energy and so on. As each quantity is introduced, its symbol will be highlighted as follows: Energy Symbol: W Capital letters are normally used to represent constant quantities – if they vary, the symbols can be made lower case, i.e. W indicates constant energy whereas w indicates a value of energy which is time varying. The names of the SI units can be abbreviated for convenience. Thus the unit for energy – the joule – can be abbreviated to J. This will be highlighted as follows: Energy Symbol: W Unit: joule (J) Here the unit is given the appropriate unit abbreviation in brackets. These are only used after numbers, e.g. 16 J. By comparison, we might refer to a few joules of energy. Now let us consider the six base quantities. The kilogram is the mass of a platinum-iridium cylinder preserved at the International Bureau of Weights and Measures at Sèvres, near Paris, France. Mass Symbol: m Unit: kilogram (kg) It should be noted that the megagram is also known as the tonne (t). The metre is the length equal to 1 650 763.73 wavelengths of the orange line in the spectrum of an internationally specified krypton discharge lamp. Length Symbol: l Unit: metre (m) Length and distance are effectively the same measurement but we use the term distance to indicate a length of travel. In such instances, the symbol d may be used instead of l. In the measurement of length, the centimetre is additional to the normal multiple units. ELEA_C01_Q4.qxd 5/13/08 9:43 Page 5 CHAPTER 1 INTERNATIONAL SYSTEM OF MEASUREMENT 5 The second is the interval occupied by 9 192 631 770 cycles of the radiation corresponding to the transition of the caesium-133 atom. Time Symbol: t Unit: second (s) Although the standard submultiples of the second are used, the multiple units are often replaced by minutes (min), hours (h), days (d) and years (a). The ampere is defined in section 2.7. Electric current Symbol: I Unit: ampere (A) The kelvin is 1/273.16 of the thermodynamic temperature of the triple point of water. On the Celsius scale the temperature of the triple point of water is 0.01 °C, hence 0 °C = 273.15 K A temperature interval of 1 °C = a temperature interval of 1 K. The candela is the unit of luminous intensity. 1.2 SI derived units Although the physical quantities of area, volume, velocity, acceleration and angular velocity are generally understood, it is worth noting their symbols and units. Area Symbol: A Unit: square metre (m2) Volume Symbol: V Unit: cubic metre (m3) Velocity Symbol: u Unit: metre per second (m/s) Acceleration Symbol: a Unit: metre per second squared (m/s2) Angular velocity Symbol: ω Unit: radian per second (rad/s) The unit of force, called the newton, is that force which, when applied to a body having a mass of one kilogram, gives it an acceleration of one metre per second squared. Force Symbol: F Unit: newton (N) F = ma [1.1] F [newtons] = m [kilograms] × a [metres per second2] Weight The weight of a body is the gravitational force exerted by the earth on that body. Owing to the variation in the radius of the earth, the gravitational force on a given mass, at sea-level, is different at different latitudes, as shown in Fig. 1.1. It will be seen that the weight of a 1 kg mass at sea-level in the London area is practically 9.81 N. For most purposes we can assume The weight of a body  9.81m newtons [1.2] where m is the mass of the body in kilograms. ELEA_C01_Q4.qxd 5/13/08 9:43 Page 6 6 SECTION 1 ELECTRICAL PRINCIPLES Fig. 1.1 Variation of weight with latitude Example 1.1 A force of 50 N is applied to a mass of 200 kg. Calculate the acceleration. Substituting in expression [1.1], we have 50 [N] = 200 [kg] × a ∴ a = 0.25 m/s2 Example 1.2 A steel block has a mass of 80 kg. Calculate the weight of the block at sea-level in the vicinity of London. Since the weight of a 1 kg mass is approximately 9.81 N, Weight of the steel block = 80 [kg] × 9.81 [N/kg] = 785 N In the above example, it is tempting to give the answer as 784.8 N but this would be a case of false accuracy. The input information was only given to three figures and therefore the answer should only have three significant numbers, hence 784.8 ought to be shown as 785. Even here, it could be argued that the 80 kg mass was only given as two figures and the answer might therefore have been shown as 780 N. Be careful to show the answer as a reasonable compromise. In the following examples, such adjustments will be brought to your attention. 1.3 Unit of turning moment or If a force F, in newtons, is acting at right angles to a radius r, in metres, from torque a point, the turning moment or torque about that point is Fr newton metres Torque Symbol: T (or M) Unit: newton metre (N m) If the perpendicular distance from the line of action to the axis of rotation is r, then T = Fr [1.3] The symbol M is reserved for the torque of a rotating electrical machine. ELEA_C01_Q4.qxd 5/13/08 9:43 Page 7 CHAPTER 1 INTERNATIONAL SYSTEM OF MEASUREMENT 7 1.4 Unit of work or energy The SI unit of energy is the joule (after the English physicist, James P. Joule, 1818–89). The joule is the work done when a force of 1 N acts through a distance of 1 m in the direction of the force. Hence, if a force F acts through distance l in its own direction Work done = F [newtons] × l [metres] = Fl joules Work or energy Symbol: W Unit: joule (J) W = Fl [1.4] Note that energy is the capacity for doing work. Both energy and work are therefore measured in similar terms. If a body having mass m, in kilograms, is moving with velocity u, in metres per second Kinetic energy = 12 mu2 joules ∴ W = 12 mu2 [1.5] If a body having mass m, in kilograms, is lifted vertically through height h, in metres, and if g is the gravitational acceleration, in metres per second squared, in that region, the potential energy acquired by the body is Work done in lifting the body = mgh joules W  9.81mh [1.6] Example 1.3 A body having a mass of 30 kg is supported 50 m above the earth’s surface. What is its potential energy relative to the ground? If the body is allowed to fall freely, calculate its kinetic energy just before it touches the ground. Assume gravitational acceleration to be 9.81 m/s2. Weight of body = 30 [kg] × 9.81 [N/kg] = 294.3 N ∴ Potential energy = 294.3 [N] × 50 [m] = 14 700 J Note: here we carried a false accuracy in the figure for the weight and rounded the final answer to three figures. If u is the velocity of the body after it has fallen a distance l with an acceleration g u = √(2gl) = √(2 × 9.81 × 50) = 31.32 m/s and Kinetic energy = 1 2 × 30 [kg] × (31.32)2 [m/s]2 = 14 700 J Hence the whole of the initial potential energy has been converted into kinetic energy. When the body is finally brought to rest by impact with the ground, practically the whole of this kinetic energy is converted into heat. ELEA_C01_Q4.qxd 5/13/08 9:43 Page 8 8 SECTION 1 ELECTRICAL PRINCIPLES 1.5 Unit of power Since power is the rate of doing work, it follows that the SI unit of power is the joule per second, or watt (after the Scottish engineer James Watt, 1736– 1819). In practice, the watt is often found to be inconveniently small and so the kilowatt is frequently used. Power Symbol: P Unit: watt (W) W F ⋅l l P= = =F ⋅ t t t P = Fu [1.7] In the case of a rotating electrical machine: 2πNr M P = Mω = [1.8] 60 where Nr is measured in revolutions per minute. Rotational speed Symbol: Nr Unit: revolution per minute (r/min) In the SI, the rotational speed ought to be given in revolutions per second but this often leads to rather small numbers, hence it is convenient to give rotational speed in revolutions per minute. The old abbreviation was rev/min and this is still found to be widely in use. Rotational speed Symbol: nr Unit: revolution per second (r/s) There is another unit of energy which is used commercially: the kilowatt hour (kW h). It represents the work done by working at the rate of one kilowatt for a period of one hour. Once known as the Board of Trade Unit, it is still widely referred to, especially by electricity suppliers, as the unit. 1 kW h = 1000 watt hours = 1000 × 3600 watt seconds or joules = 3 600 000 J = 3.6 MJ Example 1.4 A stone block, having a mass of 120 kg, is hauled 100 m in 2 min along a horizontal floor. The coefficient of friction is 0.3. Calculate (a) the horizontal force required; (b) the work done; (c) the power. (a) Weight of stone  120 [kg] × 9.81 [N/kg] = 1177.2 N ∴ Force required = 0.3 × 1177.2 [N] = 353.16 N = 353 N (b) Work done = 353.16 [N] × 100 [m] = 35 316 J = 35.3 kJ 35 316 [ J ] (c) Power = = 294 W (2 × 60) [s ] ELEA_C01_Q4.qxd 5/13/08 9:43 Page 9 CHAPTER 1 INTERNATIONAL SYSTEM OF MEASUREMENT 9 Example 1.5 An electric motor is developing 10 kW at a speed of 900 r/min. Calculate the torque available at the shaft. 900 [r/min] Speed = = 15 r/s 60 [s/min] Substituting in expression [1.8], we have 10 000 [W] = T × 2π × 15 [r/s] ∴ T = 106 N m 1.6 Efficiency It should be noted that when a device converts or transforms energy, some of the input energy is consumed to make the device operate. The efficiency of this operation is defined as energy output in a given time W Efficiency = = o energy input in the same time Win power output Po = = power input Pin Efficiency Symbol: η Unit: none Po ∴