Electrical installation work: 4th

Preface xi 1 Basic information and calculations 1 Units 1 Indices 5 Simple algebra 6 Formulae or equations 7 Manipulation or transposition of formulae 8 The theorem of Pythagoras 12 Basic trigonometry 13 Areas and volumes 15 2 Electricity 16 Molecules and atoms 16 Potential difference 19 Electron flow and conventional current flow 19 Conductors and insulators 19 Electrical quantities 19 Ohm’s law 27 Electricity and the human body 28 Types and sources of supply 29 Voltage bands 29 Measuring current and voltage 30 Components of a circuit 31 Self-assessment questions 31 3 Resistance, current and voltage, power and energy 33 Resistance 33 Voltage drop 35 Power 45 Electrical energy 51 Tariffs 52 Measuring power and energy 52 Water heating 53 Efficiency 54 Self-assessment questions 55 vi Contents 4 Electromagnetism 58 Magnetism 58 Electromagnetism 59 Application of magnetic effects 63 Drawing the waveform of an alternating quantity 68 Addition of waveforms 69 Root-mean-square (r.m.s.) value 70 Average value 71 Three-phase a.c. generator 71 Inductance 72 Induced e.m.f. due to change in flux 73 Self-inductance 74 Mutual inductance 74 Time constant: symbol, T 76 Graphical derivation of current growth curve 76 Energy stored in a magnetic field 78 Inductance in a.c. circuits 78 Resistance and inductance in series (R–L circuits) 81 Impedance 81 Resistance and inductance in parallel 83 Power in a.c. circuits 84 Transformers 87 Self-assessment questions 92 5 Capacitors and capacitance 94 Capacitors 94 Capacitance 95 Dimensions of capacitors 95 Capacitors in series 96 Capacitors in parallel 97 Capacitors in d.c. circuits 98 Capacitance in a.c. circuits 99 Capacitive reactance 99 Resistance and capacitance in series 100 Resistance and capacitance in parallel 101 Working voltage 101 Applications of capacitors 101 Self-assessment questions 101 6 Resistance, inductance and capacitance in installation work 103 Power factor improvement 108 Self-assessment questions 117 7 Three-phase circuits 118 Star and delta connections 118 The neutral conductor 118 Current and voltage distribution 119 Measurement of power in three-phase systems 123 Self-assessment questions 124 Contents vii 8 Motors 126 Direct-current motors 126 Alternating-current motors 136 Starters 145 Installing a motor 149 Fault location and repairs to a.c. machines 152 Power factor of a.c. motors 156 Motor ratings 158 Self-assessment questions 161 9 Cells and batteries 162 General background 162 The primary cell 162 The secondary cell 163 Cell and battery circuits 168 Self-assessment questions 171 10 Lighting and illumination 172 Light sources 172 Calculation of lighting requirements 182 Self-assessment questions 192 11 Electricity, the environment and the community 194 Environmental effects of the generation of electricity 194 New developments 198 The purpose and function of the National Grid 198 Generation, transmission and distribution systems 199 The aesthetic effects of the siting of generation and 200 transmission plant 12 Health and safety 202 The Health and Safety at Work Act 1974 203 Electricity at Work Regulations 1989 205 General safety 208 The mechanics of lifting and handling 209 Work, load and effort 213 Access equipment 214 The joining of materials 218 Fire safety 220 Electrical safety 221 First aid 223 13 The electrical contracting industry 225 Sample specification 229 Cost of materials and systems 234 14 Installation materials and tools 239 Cables 239 Jointing and terminations 243 viii Contents Plastics 248 Conduit 249 Trunking 255 Traywork 260 Fixing and tools 260 Comparison of systems 265 Self-assessment questions 266 15 Installation circuits and systems 268 Lighting circuits 268 Lighting layouts 270 Power circuits 271 Space heating systems 274 Thermostats 276 Installation systems 278 Industrial installations 278 Multi-storey commercial or domestic installations 282 Off-peak supplies 284 Alarm and emergency systems 286 Call systems 290 Emergency lighting systems 291 Central heating systems 292 Extra-low-voltage lighting 294 Choice of system 295 16 Earthing 304 Earth: what it is, and why and how we connect to it 304 Earth electrode resistance 307 Earthing systems 309 Earth fault loop impedence 312 Residual current devices 315 Supplementary bonding 316 Points to note 318 Self-assessment questions 319 17 Protection and control 320 Protection 320 Control 335 Points to note (IEE Reglations) 339 18 Installation design 341 Design procedure 341 Design current 341 Nominal setting of protection 342 Correction factors 342 Current-carrying capacity 345 Choice of cable size 346 Voltage drop 346 Shock risk 347 Contents ix Thermal constraints 347 Example of circuit design 351 Design problem 357 19 Testing 358 Measurement of electrical quantities 358 Measurement of current 360 Measurement of voltage 362 Instruments in general 363 Selection of test instruments 365 Approved test lamps and indicators 366 Accidental RCD operation 367 Calibration, zeroing and care of instruments 367 Initial inspection 368 Testing continuity of protective conductors 370 Testing continuity of ring final circuit conductors 372 Testing insulation resistance 375 Special tests 377 Testing polarity 378 Testing earth fault loop impedance 379 External loop impedance Ze 381 Prospective fault current 381 Testing earth electrode resistance 382 Functional testing 384 Periodic inspection 386 Certification 388 20 Basic electronics technology 392 Electronics components 392 Semi-conductors 394 Rectification 397 Electronics diagrams 402 Electronics assembly 403 Self-assessment questions 404 Answers to self-assessment questions 406 Index 413