Ferromagnetic-core design and application handbook

274 Pages·1981·32.003 MB·English

by  DeMaw, M. F.

FERROMAGNETIC-CORE DESIGN
AND APPLICATION HANDBOOK
•
FERROMAGNETIC-CORE
DESIGN
AND APPLICATION
HANDBOOK
M.F. " Doug" DeMaw
Member, IEEE, Graduate Engineer
Prentice-Hall, Inc. . Englewood Cliffs, NewJersey07632
Library of Congress Cataloging in Publication Data
DEMAIY, DOUG
Fcrromagnclk·corc design 2nd appliauion
hondbook.
Bibliogruph): p.
Includes inde~.
1. Ma gnctk: cores. 2. Magnetic dc..,ices.
I. Ti1le.
TK n72.M25D4S 621.34 80· 16136
ISBN Q.13·314088·1
Editori:il/production supervision and interior design: Nancy Moskowitz
Manufocturing buyer: Joyce Levatino
© 1981 by Prentice-Hall, Inc., Englewood Cliffs, N.J. 07632
All rights reserved. No part of this book
may be reproduced in any form or
by any means without permission in writing
from the publisher.
Printed in the United States of America
10 9 ~ 7 6 5 4 J
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CONTENTS
PREFACE ix
CHAPTER 1 THE BASICS OF MAGNETIC MATERIALS
1.1 Classifying Magnetic Materials 1
1.2 Physical and Electrical Traits 2
1.2. I Powdered irons 5
1.2.2 Ferrites 6
1.3 Calculating the Coil Turns 9
1.3. I Determining inductance II
1.3.2 Cirwit Q 12
1.4 Power Capability 14
1.4. I Flux densily versus ue 15
1.4.2 Sample calculation 18
1.4.3 Varia1ions in the equations 21
1.5 Volt-Ampere Ratings 22
1.5.1 A sample K1 core selection 23
1.5.2 Power rating 30
1.6 Inductance versus AC/DC Excitation 30
1.6.I Employment of the Hanna curve 31
1.6.2 C 011st ructing a Hanna curve 33
1.6.3 Actual air gap 36
CHAPTER 2 APPLICATION OF RODS, BARS, AND SLUGS 39
2. 1 Rods and Bars 39
2.1. I Characteristics of rods and bars 40
2.1.2 Q and L versus coil placement 42
2.1.3 Frequency versus core material 48
v
vi Contents
2.2 Rods and Bars as Antennas 49
2.2.l Loop patlern symmetry 52
2.2.2 Noise immunity 53
2.3 Practical Loop Circuits 54
2.3. l Loop-to-mixer circuits 56
2.3.2 Loop to RF amplifier 57
2.3.3 Loop with sense antenna 59
2.3.4 Loop variations 61
2.4 Rod-Core Transformers 62
2.5 Slug Applications 63
2.5. I Performance considerations 65
2.5.2 Practical circuits 68
2.6 RF Chokes 73
2.6. I Choke applications 73
CHAPTER 3 APPLYING TOROIDAL CORES 79
3.1 Low-Level Circuits 79
3. I. I RF amplifiers 80
3.1.2 Capacitive-divider marching 83
3.1.3 Interstage coupling 85
3.1.4 Toroids in filters 87
3.1.5 Toroids in instruments 93
3.1.6 Other low-level applications 96
3.2 Broadband Transformers 99
3.2.l Bifilar-wound transformers JOO
3.2.2 Quadrifilar transformers IOI
3.2.3 Broadband conrentional transformers 102
3.2.4 Variable impedance matching 109
3.3 Antenna Loading 112
3.4 Toroidal Distributed Capacitance 113
3.5 Power Supplies 114
3.5. I Using poll'er FETs as swi1ches 116
3.6 Core Doping 11 7
3.6. I Simple doping methods 118
3.6.2 Potting technique 120
CHAPTER 4 BEADS. SLEEVES. AND POT CORES 123
4.1 Properties of Beads 124
4.1. l Shield-bead allenuation 126
4.1.2 Practical applications for beads 130
4.1.3 Beadsas Qkillers 133
4.1.4 Beads for decoupling 135
4.1.5 Reducing incidental radit11ion 136
4.2 Ferrite Sleeves 137
4.3 Ferrite Balun Cores 141
Contents vii
4.4 Pot Cores 143
4.4. l Pol-core hardware 144
4.4.2 Design co11sideratio11s 146
4.4.3 POI-core designs 153
4.4.4 Tone encoder with pot core 154
4.4.5 Pot cores in filters 157
CHAPTER 5 PERMANENT-MAGNET DATA 159
5.1 The Nature of Permanent-Magnet Materials 159
5.2 Elementary Permanent-Magnet Relationships 165
5.2.1 The B-H curve 165
5.2.2 Recoil loops 166
5.2.3 Working point of a magnet (static
applications) 167
5.2.4 The magnetic circuit 167
5.2.5 The permanent magnet in an external
field 169
5.3 Magnetization 1 70
5.3. I Conditions for comp/ere sa111ra1ion 171
5.3.2 Magnetizing equipme111 172
5.4 Demagnetization 176
5.4. l De111agnetiza1ion techniques 176
5.5 Stability and Stabilization 177
5.5.1 M eta/lurgica/ changes 178
5.5.2 Time 178
5.5.3 Temperature 178
5.5.4 Reluctance changes 180
5.5.5 A cfrerse fields 180
5.5.6 Shock. stresss. and vibrarion 180
5.6 Measurements and Calibration 180
5.7 Handling of Permanent Magnets 181
5. 7.1 U11111agne1ized magners 182
5.8 Glossary of Terms 182
APPENDIX A REFERENCES 189
APPENDIX B MISCELLANEOUS DATA 195
APPENDIX C POT-CORE AND BOBBIN DATA 207
APPENDIX D CYLINDRICAL-CORE ANO COIL DATA 215
APPENDIX E TORROID-CORE DATA 229
INDEX 251