Newnes
An imprint of Elsevier Science
Linacre House, Jordan Hill, Oxford OX2 8DP
200 Wheeler Road, Burlington, MA 01803
First published by George Newnes Ltd 1937
Twenty-second edition 1995
Twenty-third edition 2003
Copyright
©
2003 E.A. Reeves and Martin J. Heathcote. All rights reserved
The right of E.A. Reeves and Martin J. Heathcote to be identified as the authors 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
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
ISBN 0 7506 4758 2
For information on all Newnes publications
visit our website at www.newnespress.com
Typeset by Laserwords Private Limited, Chennai, India.
Printed and bound in Great Britain
Contents
PREFACE ix
ACKNOWLEDGEMENTS xi
INTRODUCTION 1
1 FUNDAMENTALS AND THEORY 2
Fundamentals; Electrostatics; Capacitors; The magnetic circuit;
A.C. theory
2 PROPERTIES OF MATERIALS 21
Magnetic materials; Copper and its alloys; Aluminium and its
alloys; Insulating materials; Superconductivity
3 PLASTICS AND RUBBER IN ELECTRICAL ENGINEERING 54
Properties of moulding materials; Thermosetting materials;
Thermoplastics materials; Rubber in electrical engineering
4 SEMICONDUCTORS AND SEMICONDUCTOR DEVICES 66
Semiconductors; Applications of power semiconductors;
Thermionic devices; Photoelectric devices
5 RECTIFIERS AND CONVERTERS 94
Introduction; Metal rectifiers; Rectifier equipments; Converting
machines
6 COMPUTERS AND PROGRAMMABLE CONTROLLERS 105
Office and home computers; Security; Industrial computing;
Microprocessor-based devices
7 ELECTRICITY GENERATION 112
Synchronous generator theory; Types of generator; Generator
construction; Testing; Generator protection and synchronization;
Connection to electrical network; Operation of generators;
Excitation systems; Automatic voltage regulators; Power
generation for public electricity supply; Industrial generation;
High integrity power supplies; Solutions to power problems;
The on line double conversion; General requirements for UPS;
Rectifier/battery charger; IGBT inverter; Static switch;
Monitoring and controls; Parallel configurations; Typical
installation; Diesel no break systems; Solar energy
8 TRANSMISSION AND DISTRIBUTION 159
British regulations for overhead lines; Efficiency of transmission
and distribution systems
9 CABLES 166
Underground cables; Underground cable constants; Wiring
cables
v
vi
10 TRANSFORMERS AND TAPCHANGERS 181
Transformers; Tapchanging in transformers
11 TARIFFS AND POWER FACTOR 202
Tariffs; Power factor correction
12 REQUIREMENTS FOR ELECTRICAL INSTALLATIONS
(BS 7671) 210
IEE Wiring Regulations (Sixteenth Edition); Changes introduced
by the 2001 edition; BS 7671 : 2001 Details of Regulations;
Part 1. Scope, object and fundamental principles; Part 2.
Definitions; Part 3. Assessment of general characteristics;
Part 4. Protection for safety; Part 5. Selection and erection of
equipment; Part 6. Special installations or locations; Part 7.
Inspection and testing; Conventional circuit arrangements;
Limitation of earth fault loop impedance; Cable current-carrying
capacities; Methods of cable support; Methods of testing
13 LIGHTING 261
Electric lamps; Interior lighting techniques; Floodlighting
techniques
14 MOTORS AND CONTROL GEAR 291
D.C. motors; A.C. motors; Induction motors; Synchronous
motors; Single-phase motors; Speed variation of a.c. motors;
Motor dimensions; Motor control gear
15 SWITCHGEAR AND PROTECTION 342
Switchgear; Overload and fault protection; Relays and
protective gear
16 HEATING AND REFRIGERATION 364
Water heating; Space heating; Thermostatic temperature control;
Electric cookers; High frequency heating; Electric steam boilers;
Electric hot water boilers; Lamp ovens for industry;
Refrigeration and air conditioning; Air conditioning and
ventilation
17 BUILDING AUTOMATION SYSTEMS 396
Realizing the potential of building management systems
18 INSTRUMENTS AND METERS 405
Ammeters and voltmeters; Wattmeters; Valve voltmeters; Shunts
and series resistances; Current and voltage transformers; Energy
meters; Testing of meters; Transducer systems; Multifunction
instruments
19 ELECTRIC WELDING 427
Flux-shielded arc welding; Gas-shielded arc welding;
Unshielded and short-time processes; Resistance welding;
Radiation welding
vii
20 BATTERY ELECTRIC VEHICLES 438
Battery-driven light cars; Hybrid vehicles; Fuel cell drives;
Industrial vehicles
21 BATTERY SYSTEMS 445
Applications; Lead-acid batteries; Nickel-cadmium alkaline
cells; Battery charging; Reference documents
22 CABLE MANAGEMENT SYSTEMS 457
Integrated systems
23 HAZARDOUS AREA ELECTRICAL WORK 471
ATEX directives; Hazardous areas; Electrical equipment;
Installation, inspection and maintenance practice; Sources of
further information
INDEX 495
This Page Intentionally Left Blank
Preface
It is now seven years since the twenty-second edition of the Pocket Book
was published, a rather longer interval than might be desirable in the rapidly
moving and rapidly developing world of electrical technology. We now have
a new editor and, as a result, the possibility of some differing emphasis.
Eric Reeves’ name has become synonymous with the Pocket Book. He
has been editor for over forty years covering some ten or more editions. He is
now enjoying his ‘retirement’. He has left a pocket reference work that is in
good shape, but inevitably as the industry moves on, the detail is constantly
subject to change.
In the UK, privatization of electricity supply was some six years consigned
to history at the time of publication of the twenty-second edition. But much
of the transformation of the industry, which now sees electricity traded as
any other commodity like oil or coffee beans, has taken place over the last
five or six years. Many of the companies that the Government set up in 1989
have now disappeared and the structure of the industry has changed beyond
recognition. Changes now occur so rapidly that the details of the UK utilities
as given in the previous edition have been dropped. The reader must now keep
up with these developments by closely watching the business pages of his or
her newspaper.
Now, if it is more profitable to sell gas than to use it to generate electricity
and sell that, utilities are happy to do this. Now, the generators, transmission
lines and transformers are ‘assets’ which assist the owners in making a profit,
and the staff entrusted with the care and supervision of these are ‘asset man-
agers’. They may be more skilled in risk assessment and knowledgeable about
failure rates and downtimes than their predecessors, but it is still necessary
to retain a workforce who know about the plant and are able to ensure it can
remain in safe and reliable operation.
Privatization of the UK electricity supply has also led to many utilities
procuring equipment overseas, particularly from Europe. This has resulted in
the adoption within the UK of new approaches to many aspects of electrical
equipment design and specification. In a wider context this has probably pro-
vided added impetus to harmonization of standards and the acceptance of IEC
and CENELEC documentation.
Today’s technicians face a challenging task to keep abreast of develop-
ments even within quite narrow fields and ‘continuing professional develop-
ment’ is a task to be pursued by all, not simply those who wish to gain
advancement in their chosen field.
This is where it is hoped that this little book will remain of assistance.
The danger is that it will get larger at each new edition. If it is to remain a
handy pocket reference size, then to include new material it is necessary to
leave out some information which has proved useful in the past. The hope is
that the balance will remain about right and what Eric Reeves has achieved
so successfully for many years will continue.
One chapter which might have been left out is Chapter 6 which deals
with computers. These are no longer specialist tools to be used by the few;
even children in primary schools are being given computing skills. There are
ix
x
weekly and monthly magazines by the score which can provide an introduction
to computing, so its need in a work such as this might be superfluous. However,
the chapter has been retained because of its relevance to electrical engineering,
but it has been shortened and made less specific, hopefully in a form which
will provide some useful background for those working in other branches of
electrical engineering.
Chapter 4 of the twenty-second edition dealt with semiconductors as
devices which have superseded valves in electronic equipment. Although many
older engineers may have been introduced to semiconductors in this way,
valves are no longer taught in colleges and universities. Hence the emphasis
has been reversed with semiconductors introduced in their own right and some
descriptions of valve devices retained because these might be encountered in
special applications.
Chapter 7 has been extensively revised to include some description and
theory of a.c. generators. Although few will find themselves coming into close
practical contact with these, some understanding of the design and workings
of the main source of electrical power is perhaps desirable for those who earn
or seek to earn their livelihood in the electrical industry.
Likewise the chapter on transformers, Chapter 10, has been expanded a
little to include some detail of their construction, connections, phase shifts
and losses, although few in the electrical industry will encounter any but the
smaller end of the size range. The section dealing with magnetic materials in
Chapter 2 has also been expanded since in large transformers and generators
magnetic steel is just as important a material as copper.
Since the publication of the twenty-second edition there has been a revi-
sion of BS 7671 which has brought about significant changes. A section has
therefore been added to Chapter 12 detailing the changes and discussing the
implications of these.
Building automatic management systems, which were highlighted in the
preface to the twenty-second edition as being subject to rapid change, has seen
even further development in view of the advances in computing capability.
The result is that Chapter 17 has been largely rewritten to identify these
developments.
Chapter 20, dealing with battery electric vehicles has been expanded a
little to reflect the growth of interest in clean vehicles and particularly to
describe recent developments relating to hybrid vehicles.
There have been significant changes in requirements relating to electrical
equipment for use in hazardous areas in recent years as a result of two EU
Directives, 94/9 relating to explosion protected equipment, and 99/92 relating
to certification of the equipment. Chapter 23, which was newly written for the
twenty-second edition, has, as a result, been extensively revised.
Despite what may appear a lengthy list of changes, much of what was
written by Eric Reeves in the twenty-second edition remains. The hope is that
readers will find both the older material that has been retained, and that which
is new, of value, and that no one will feel that any vital aspect which has made
Eric’s formula such a successful one over so many years has been cast aside.
M.J.H.
Acknowledgements
Inevitably when aiming to cover as wide a spectrum of electrical engineering
as does the Pocket Book, it is necessary to go to many sources in order to
obtain authoritative information which can be committed to print for the benefit
of readers. Many people have assisted in the preparation of the twenty-third
edition, either by writing complete chapters or sections, or simply by providing
constructive criticism of the editor’s efforts.
The editor wishes to express grateful thanks to all those friends and col-
leagues, individuals and organizations who have provided assistance in this
revision. In particular to my good friend W.J. (Jim) Stevens who has read most
of what has been written and provided invaluable criticism and comment; to
my good friend, Mike Barber, who rewrote much of Chapter 7 relating to elec-
tricity generation and the theory and practice of a.c. generators; to colleagues
Bob Dodd, for the descriptions of AVRs and John Rhodes, for paragraphs on
wind energy in this chapter; to Neil Pascoe for his contribution on metering
transducer systems and Dan Brown for Chapter 6 on computers; Mike Row-
bottom for a description of NETA, the New Electricity Trading Arrangements,
in Chapter 11; to other friends and colleagues who have read and commented
on specific sections and to those who have provided written contributions; Bob
Bradley, TCM Tamini, on high integrity and UPS power supplies included in
Chapter 7; Ian Harrison, Chloride Industrial Batteries, for much of the mate-
rial for Chapter 21; Tony Martin on aluminium busbars; Terry Journeaux,
Pirelli Cables, for information for Chapter 9; Paul John, Marconi Applied
Technologies, for data on valves and related Marconi products. Thanks are
also due to Ray Lewington of BEAMA for permission to make use of his
lecture material covering the 2001 revision of BS 7671; Hugh King, Thorn
Lighting, for updating Chapter 13; Steve Dalton, Johnson Industrial Control
Systems, for updating Chapter 17; Simon Howard, Crompton Instruments for
additions to and updating of Chapter 18; Dick Martin, CEAG Crouse Hinds,
for Chapter 23. My thanks to the Institution of Electrical Engineers for permis-
sion to reproduce extracts from BS 7671, and to the many organizations who
have provided the many photographs and illustrations to whom attribution is
given in the text.
Finally, despite the quite extensive revision involved in the production of
the twenty-third edition, the greater part of the book remains the work of Eric
Reeves from the twenty-second edition, and for this due acknowledgement
must be given.
xi
Introduction
The chief function of any engineer’s pocket book is the presentation in con-
venient form of facts, tables and formulae relating to the particular branch of
engineering concerned.
In the case of electrical engineering, it is essential that the engineer should
have a clear understanding of the methods by which the various formulae
are derived in order that he can be quite certain that any particular formula
is applicable to the conditions which he is considering. This applies with
particular force in the case of alternating current work.
The first section of the Pocket Book is, therefore, devoted to the theoretical
groundwork upon which all the practical applications are based. This covers
symbols, fundamentals, electrostatics and magnetism.
When an engineer is called upon to deal with any particular type of
electrical apparatus, for example a protective relay system, a thermostatically
controlled heating system, or industrial switchgear and control gear, the first
requirement is that he shall understand the principles upon which these systems
operate. In order to provide this information, much space has been devoted in
the various sections to clear descriptions of the circuits and principles which
are used in the different types of electrical apparatus.
The inclusion of technical descriptions, together with the essential data
embodied in the tables, will be found to provide the ideal combination for those
engineers engaged on the utilization side of the industry, where many different
types of equipment and electrical appliances, ranging from semiconductor
rectifiers to electrode steam boilers, may have to be specified, installed and
maintained in safe and efficient operation.
An extensive summary of the sixteenth edition of the ‘IEE Regulations
for Electrical Installations’ (now BS 7671) is contained in Chapter 12. In 1992
when this was first issued as a British Standard, the layout and content were
markedly different to the previous editions and for those personnel working
in electrical contracting it is important that they obtain their own up-to-date
copy of the Regulations. One of the most important changes in 1992 was
the exclusion of many of the Appendices which were published as separate
Guidance Notes (see page 260). Another change was the inclusion of a new
Part 6, ‘Special installations or locations’. Section 6 has been added to in
the 2001 edition, and, in addition, in an extended Part 7, there is increased
emphasis on periodic inspection and testing. More is said about these in the
Preface and in Chapter 12.
1
1 Fundamentals and theory
Fundamentals
Current. The term ‘current’ is used to denote the rate at which electricity
flows. In the case of a steady flow the current is given by the quantity of
electricity which passes a given point in one second. (Although since 1948
the unit of current has been officially defined in terms of the electromagnetic
force that it produces, see below – since this force can be most conveniently
measured.) The magnitude of the current depends not only upon the electro-
motive force but also upon the nature and dimensions of the path through
which it circulates.
Ohm’s law. Ohm’s law states that the current in a direct current (d.c.)
circuit varies in direct proportion to the voltage and is inversely proportional to
the resistance of the circuit. By choosing suitable units this law may be written
Current =
Electromotive force
Resistance
The commercial units for these quantities are
Current – the ampere (A)
Electromotive force – the volt (V)
Resistance – the ohm ()
Using the symbols I, V and R to represent the above quantities in the
order given, Ohm’s law can be written
I =
V
R
or V = I × R
The law not only holds for a complete circuit, but can be applied to any part
of a circuit provided care is taken to use the correct values for that part of
the circuit.
Resistivity. The resistivity of any material is the resistance of a piece
of the material having unit length and unit sectional area. The symbol is ρ
and the unit is the ohm metre. The resistivity of a material is not usually
constant but depends on its temperature. Table 1.1 shows the resistivity (with
its reciprocal, conductivity) of the more usual metals and alloys.
Resistance of a conductor. The resistance of a uniform conductor with
sectional area A and length l is given by
R = ρ
l
A
The units used must be millimetres and square millimetres if ρ is in ohm
millimetre units.
2
Không có nhận xét nào:
Đăng nhận xét