Induction Heating Handbook

Induction Heating Handbook John Davies University of Aston in Birmingham Peter Simpson ... 1.2 Induction-heating principles 2 1.3 Applications 5 1.4 P...

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Induction Heating Handbook John Davies University of Aston in Birmingham

Peter Simpson Ministry of Defence

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Contents Preface

xi

Chapter 1

Introduction to Induction Heating 1 1.1 The background to induction heating 1 1.2 Induction-heating principles 2 1.3 Applications 5 1.4 Power Systems 5 1.5 Economics, safety, and environment 8

Chapter 2

Through-heating by Induction 10 2.1 Introduction to applications of through-heating 10 2.2 Temperature effects 17 2.3 Heat radiation and convection 24 2.4 Temperature distribution in induction through-heating 2.5 Effects of current depth and radiated heat 27 2.6 Temperature distributions in a heating cycle 28 2.7 Selection of frequencies for induction through-heating 2.8 Application specifications for coil design 33 2.9 Equivalent circuit coil-design method 43 2.10 Approximate coil-design method 49 2.11 Mechanical construction of coils 55 2.12 Slab reheating 58 2.13 Travelling-wave induction heating 59 2.14 Multi-layer coils 63 2.15 Tapered heating for extrusion 64 2.16 Scale-model analogue methods 65

Chapter 3

Surface Heating by Induction 67 3.1 Metallurgical principles of heat treatment 71 3.2 Quenches and quenching . 77 3.3 Selection of frequency in induction heat treatment 81 3.4 Temperature distribution in induction surface hardening 3.5 Application specifications for coil design 89 3.6 Mechanical construction of coils 91 vii

26

30

87

Chapter 4

Other Applications of Induction Heating 96 4.1 Soldering and brazing 96 4.2 Tube welding 109 4.3 Heating of resin kettles and other vessels 118 4.4 Paintdrying 120 4.5 Induction heating in plastic working 121 4.6 Annealmg and stress relieving 122 4.7 Longitudinal flux induction heating 124 4.8 Transverse flux heating 124 4.9 Semiconductor processing 126 4.10 Miscellaneous uses of induction heating

Chapter 5

Chapter 6

Chapter?

Induction Melting 135 5.1 Principles of induction meiters 135 5.2 The coreless induction furnace 142 5.3 The Channel furnace 148 5.4 Comparisonof coreless and Channel furnaces 5.5 Special features in melting furnaces 155 Supply-frequency Heating Systems 163 6.1 Advantages and limitations 163 6.2 Load matching 165 6.3 Control and switchgear 168 6.4 Solid-state power regulators 172 6.5 Measurements at supply frequencies 0.0 Workhandling equipment 174 6.7 Melting furnace System 177 6.8 Frequency multipliers 178 6.9 Dual-frequency Systems 180

152

173

Medium-frequency motor^mator Systems 181 /-l Introduction 181 7.2 Principles ofthemedium^requencygenerator 181 7.3 Mechan.cal features ofinductor-alternators 187 7.4 Electncal behaviour of the generator 190 7.5 Load matching and tuning 194 7.6 Control Systems 198 7.7

Chapter 8

131

Automatic voltage regulators

200

Medium-frequency Solid-state Systems

8 2

'

I t r T ^

v * * * * * ^ >

a r S S * "

°f

m e d l U m

202 solid-state

'fr^—y

con-

induction-heating

8.3 8.4 ».:>

Requirements of the static inverter 203 Sibcon-controlledrectifiercharacteristics 204 tSasic inverter Systems 205

8.6 8.7

Swept-frequency Systems 207 Load-resonant System 210 vm

static

8.8 8.9 8.10 8.11 8.12 Chapter9

Comparative efficiencies and impedance characteristics 212 Control and protection 214 Construction and layout 216 Capital and running costs 218 Comparison between inverters and motor-alternators 219

Radio-frequency Systems 221 9.1 The basis of the radio-frequency generator 221 9.2 Industrial RF heating osciilator valves 229 9.3 The ideal industrial valve characteristics 230 9.4 Construction of industrial triode valves 231 9.5 Magnetically-focused triode 235 9.6 Class C osciilator design 237 9.7 Anode HT power supplies 245 9.8 Control circuits 248 9.9 Power control Systems 249 9.10 Load-matching Output circuits 254 9.11 Radio-frequency metering 260 9.12 Generator reliability 261

Chapter 10 Ancillary Equipment 263 10.1 Measurement technlques 263 10.2 Supply-frequency measurements 263 10.3 Medium-frequency measurements 263 10.4 Radio-frequency measurements 266 10.5 Integrated measurement and control 268 10.6 Temperature measurements 270 10.7 Miscellaneous measurements 272 10.8 Temperature control Systems 273 10.9 Power control and regulation 275 10.10 Cables and busbars 275 10.11 Workhandiing equipment 280 Chapter 11 Economics 292 11.1 Economics and thermal efficiencies of power sources 11.2 Cost analysis in hardening and welding 296 11.3 Heating for forging comparisons 298 11.4 Costs of melting furnaces 304 11.5 Miscellaneous economic factors 306 Chapter 12 Theory of Induction Heating 307 12.1 Introduction 307 12.2 Skin effect for semi-infinite siab 307 12.3 Power and flux for semi-infinite slab 314 12.4 Power and flux induced in a wide rectangular slab 12.5 Power and flux in a solid cylinder 322 12.6 Power induced in a hollow cylinder 329 12.7 Non-linear theory 335 12.8 Proximity heating 337 ix

292

318

Chapter 13 Heat Transfer 341 13.1 Introduction 341 13.2 Reiationship between power m M n t » m

8

34

g fe^SF- " J.J.7 Rectanguiar slab 351 13.8 Radiation 352 13.9 g surfacp h ^ • 11 1ft Heat ftau» transfer •„ . . durine . »uriace nardemng 356

ChapKrU Safelyand Environment Conditio« 373 sibilities

374

'

employees'

respon-

U 4 f^ rna f tionaJ s a f «ty regulations 375 14.4 I E C safety recommendations 375 14.5 Environment and terminology 377 Appendix 1

Eiectroheating Terminology 379 ALI

C ^ o n

of electroheat e.uipment according to f r e i e n -

AI.2

Terminology 379

Appendix 2 W ^ D B - ^ i n a a b

383

A2 2

f^ b t heate ^

A2-4

SoakingofsIabprevious]yheatedfrombothsides

from one side only 383 ^

Appendix 3 A ^ I ^ ^ ^ ^ ^ ^ A3.2 A3.3

A34

3 9 4

Power plant-quahtyofengineering 394 C h c c e o f power plant for induct.on furnace 397

- prxs&z^'-zrZ-

A3.5 A3.6 Appendix 4

Unit Conversion Tables 407

Appendix 5

Re-stivity, Specific Heat, and Thermal ConH , !U Temperature 410 d e r m a l Conductivity as Functions of

References 412 Index 419

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