Guide to Transformers -- Article Index


1. Transformer Magnetics

2. Basics of Iron-Core Transformers

3. Power Transformers

4. Audio Transformers

5. High-Frequency Transformers

6. Special Transformers and Applications

The ease with which transformers transfer energy from one circuit to another by electromagnetic induction allows their common usage in all aspects of electrical and electronic technology. The absence of moving parts, the transfer of energy without change of frequency, high efficiency, and the relatively little care required for maintenance because of a transformer's simple and durable construction, indicate increasing roles for these devices in communications and power work. Thus, it is necessary for those working with electronics to understand the essential relationships of transformer theory.

This guide discusses and evaluates transformer theory and the varied types of transformer operations and applications. Transformer theory is presented with simple mathematical treatment, which permits sufficiently extensive analysis and allows the interested technician or student to develop full comprehension. Adequate information is given relating to broad concepts and information designed for ready use. Detailed descriptions of a small number of selected major topics are presented and, through presentation of practical situations, equipment, and problems, the reader is afforded an opportunity to apply the principles he has learned.

Specific attention is given to transformer magnetics, flux density, magnetic intensity, a review of magnetic units, permeability of free space, and relative permeability. Magnetization curves, hysteresis loop, core losses and their measurement are also discussed.

In addition, current and voltage waveforms in transformer primaries, transformer shielding, design, and construction are analyzed. The theory of basic operation efficiency, coil currents, coup ling and mutual inductance, leakage inductance, and distributed capacitance receive particular attention. Transformer size and efficiency, core materials, power transformers, pertinencies of filter systems, filament transformer ratings, transformer primary control, distribution systems are evaluated. Special emphasis is placed on voltage and current relationships in three-phase systems, audio transformer types, equivalent circuits, the impedance ratio of audio transformers, parallel-feed coupling method, and considerations of high-frequency transformers. The varied uses of under coupling, critical coupling, transitional coupling, and overcoupling are dwelt upon. Gain-bandwidth factors, special transformers and their applications, saturable reactors, self-saturating saturable reactors, voltage-regulating transformers, and balancing transformers are also discussed. Special emphasis is devoted to problems relating to the pertinent areas of transformer theory.

Mastery of the material presented herein will insure the student an adequate basis to undertake work requiring a pre-requisite knowledge of transformers.

Grateful acknowledgment is made to the staff of New York Institute of Technology for its assistance in the preparation of the manuscript of this guide.

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