Copyright © 1947, 1955

John Wilp:y & Sons, Inc.

All Rights Reserved

This book or any part thereof must not be reproduced in any form without the written permission of the publisher.

Library of Congress Catalog Card Number: 55-10001

peinted in the -united states op america

PREFACE TO SECOND EDITION

In the years since the first edition of tliis book was published, several new developments have taken place. This second edition encompasses such new material as will afford acquaintance with advances in the art. Some old topics which were inadequately presented have received fuller treatment. Several sections, especially those on electronic amplifiers and \vave filters, have been deleted because more thorough treatments of these subjects are available in current literature. Thus the original objectives of a useful book on electronic transformers and related devices, with a minimum of unnecessary material, have been pursued in the second edition. Wherever the old material appeared adequate, it has been left unchanged, and the general arrangement is still the same, except for the addition of new Chapters 9 and 11. More information in chart form, but few mathematical proofs, are included.

In a book of general coverage, there is room only for a brief treatment of any phase of the subject. Thus the new chapter on magnetic amplifiers is a condensed outline of the more common components and circuits of this rapidly growing field. It is hoped that this chapter will be helpful as a general introduction to circuit and transformer designers alike. Recent circuit developments are reported in the AIEE Transactions.

In response to inquiry it should be stated that, where a mathematical basis is given, graphical performance is always calculated. There has been good general correspondence between the graphs and experunental tests. This correspondence is quite close in all cases except pulse transformers; for these, the graphs presented in this book predict wave shape with fair accuracy, but to predict exactly all the superposed ripples would be impracticable. This is pointed out in Chapter 10.

Although technical words usually have the same meaning as in the first edition, there are several new magnetic terms in the second edition. These terms conform with ASTM Standard A127-48.

Pascal said that an author should always use the word our rather than my in referring to his work, because there is in it usually more of other peoples than his own. Never was this more true than of the present volume. Acknowledgment is due many Westinghouse engineers, especially R. M. Baker, L. F. Deise, H. L. Jessup, J. W. Ogden, G. F. Pittman, R. A. Ramey, T. F. Saffold, and D. S. Stephens, all of whom

vi PREFACE TO SECOND EDITION

assisted immeasurably by their constructive comments on the manuscript. D. G. Littles continued interest was most encouraging.

Helpful comment has been received from men outside Westinghouse. Mr. P. Fenoglio of the General Electric Co. kindly pointed out an omission in the first edition. Output wave shapes given for the front or leading edge of a pulse transformer were accurate for a hard-tube modulator, but not for a line-type modulator. The missing information is included in the second edition.

Finally, to my wife Margaret, my heartfelt thanks not only for her understanding of the long disruption of normal social hfe but also for her patience in checking proofs.

Reuben Lee

Baltimore, Maryland August, 1955

ACKNOWLEDGMENTS

Figures 23 and 24 were furnished through the courtesy of the Armco Steel Corp. Figures 50, 51, 52, 53, and 86 first appeared in a paper by O. H. Schade, Proc. LR.E., July, 1943, p. 341. Figure 150 is reprinted from Proc. LR.E., April, 1945. Figure 63 first appeared in the LR.E. Transactions on Component Parts, April, 1955.

Figure 71 is reprinted from Electronics, March, 1955. Figures 89, 90, and 91 are reprinted from, and Section 52 (p. 123) is based on, Solving a Rectifier Problem, Electronics, April, 1938. Figures 100 and 101 are reprinted from Electronics for September, 1949. Figure 180 and Section 97 (p. 232) are based on A Study of R-F Chokes, which appeared in Electronics in April, 1934. Sections 123, 124, 125, and 127 (p. 294 et seq) are based on Iron-Core Components in Pulse Amplifiers, Electronics, August, 1943. Figures 73, 258, and 259 are reprinted from this article.

Figure 88 is reprinted from Tele-Tech and Electronic Industries, October, 1953 (copyright Caldwell-Clements, 480 Lexington Avenue, New York).

Figures 107 and 110, and part of Section 67 (p. 153), first appeared in Radio Engineering, June, 1937.

Figure 142 is reprinted from the General Radio Experimenter, November, 1936.

Figures 163, 164, and 165 are reprinted from Magnetic Ferrites- Core Materials for High Frequencies, by C. L. Snyder, E. Albers-Schoenberg, and H. A. Goldsmith, Electrical Manufacturing, December, 1949. Figure 191 is reprinted from Electrical Manufacturing for September, 1954.

The magnetic amplifier analysis on p. 276 is based on an unpublished paper by D. Lebell and B. Bussell, presented at the LR.E. Convention, New York, March, 1952.

Figures 235, 252, 254, and 255, and Table XVII, are reprinted from Proc. I.R.E., August, 1954.

PREFACE TO FIRST EDITION

The purpose of this book is twofold: first, to provide a reference book on the design of transformers for electronic apparatus and, second, to furnish electronic equipment engineers with an understanding of the effects of transformer characteristics on electronic circuits. Familiarity with basic circuit theory and transformer principles is assumed. Conventional transformer design is treated adequately in existing books, so only such phases of it as are pertinent to electronic transformers are included here. The same can be said of circuit theory; only that which is necessary to an understanding of transformer operation is given. It is intended that in this way the book will be encumbered with a minimum of unnecessary material. Mathematical proofs as such are kept to a minimum, but the bases for quantitative results are indicated. The A.I.E.E. American Standard Definitions of Electrical Terms gives the meaning of technical words used. Circuit symbols conform to A.S.A. Standards Z32.5-1944 and Z32.10-1944.

Chapter headings, except for the first two, are related to general types of apparatus. This arrangement should make the book more useful. Design data are included which would make tedious reading if grouped together. For instance, the design of an inductor depends on whether it is for power or wave filter work, and the factors peculiar to each are best studied in connection with their respective apparatus.

Parts of the book are based on material already published in the Proceedings of the Institute of Radio Engineers, Electronics, and Communications. Much of it leans heavily upon work done by fellow engineers of the Westinghouse Electric Corporation, the warmth of whose friendship I am privileged to enjoy. To list all their names would be a difficult and inadequate expression of gratitude, but I should be guilty of a gross omission if I did not mention the encouragement given me by Mr. D. G. Little, at whose suggestion this book was written.

R. L.

July 1947

CONTENTS

List of Symbols........... xiii

1. Introduction........... 1

2. Transformer Construction, Materials, and Ratings . . . 17

3. Rectifier Transformers and Reactors...... 61

4. Rectifier Performance......... Ill

5. Amplifier Transformers......... 140

6. Amplifier Circuits.......... 178

7. Higher-Frequency Transformers....... 214

8. Electronic Control Transformers....... 237

9. Magnetic Amplifiers......... 259

10. Pulse and Video Transformers....... 292

11. Pulse Circuits........... 329

Bibliography............ 347

Index............. 351

LIST OF SYMBOLS

Page numbers are those on which the corresponding symbol first appears. A symbol formed from one of the tabulated letters, with a subscript or prime added, is not listed unless it is frequently and prominently used in the book. Sometimes the same symbol denotes more than one property; the meaning is then determined by the context. Units are given wherever symbols are used. Small letters indicate instantaneous or varying electrical quantities, and capital letters indicate steady, effective, or scalar values.

Coil radius, 228 Coil winding height, 75

147 Area, 172 Core area, 10 Ripple amplitude, 114 Winding traverse, 76 Xc/Ri at frequency/г, 150 Core flux density, 10 Втях Maximum operating flux density, 23, 97 Residual flux density, 23 Insulation thickness, 75 Specific heat, 57 Capacitance, 64 Cp Primary capacitance, 147

Cs Secondary capacitance, 147

Effective capacitance, 172 Capacitance of winding to ground, 245 ,w Capacitance across winding, 245

Core tongue width, 38 Toroid diameter, 288 Winding height, 38 Xc/R2 at frequency fr, 159 Voltage (instantaneous value), 5 Alternating grid voltage, 141 Alternating plate voltage, 141

xiii

Short-circuit inductance, 76 Mutual inductance, 224 Decrement, 104 Order of harmonic, 114 Modulation factor, 16 Mean turn length, 38 Number (e.g., of anodes), 76 Turns, 5

Primary turns, 5 Secondary turns, 5

Number of layers (of wire in coil), 173 Open-circuit inductance, 106 Density, 26

Ratio of voltages (in autotransformer), 250 Rectifier ripple frequency/line frequency (number of

phases), 113 Volt-amperes per pound, 26 Core loss, 26

Ripple amplitude/Edc (in rectifier), 114

Ripple amplitude/jc (across load), 114

Pulse forming network, 332

Pulse repetition frequency, 338

coL/R = coil reactance/coil a-c resistance, 106

Radius, 38

Equivalent radius, 57 Plate resistance, 144 Resistance, 6 Source resistance, 146 Load resistance, 146 Load resistance, 8

Equivalent core-loss (shunt) resistance, 8 Secondary winding, 71 Core window width, 102 Time (independent \ariable), 5 Thickness of insulation, 172 Period of a wave, 15

27r\/LaC2 (undamped period of oscifiatory wave), 295

Commutation voltage, 120

Volume (of core), 91

Core-stacking dimension, 38

Gap loss, 191

Core loss 82