Preface to Second Edition

In the years since the first edition of this 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 wave 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 Magnetic Amplifiers and Pulse Circuits. 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 experimental 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 Pulse and Video Transformers.

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 people's 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 assisted immeasurably by their constructive comments on the manuscript. D. G. Little's 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 life but also for her patience in checking proofs.

Reuben Lee

Baltimore, Maryland August, 1955