11 Magnetic Circuits and Transformers
11.1 Magnetic Materials
11.2 Magnetic Circuits
11.3 Transformer Equivalent Circuits
11.4 Transformer Performance
11.5 Three-Phase Transformers
11.6 Autotransformers
11.7 Learning Objectives
11.8 Practical Application: A Case Study—Magnetic Bearings for Space Technology
Problems
A basic understanding of electromagnetism is essential to the study of electrical engineering
because it is the key to the operation of many electric apparatus found in industry and at home.
Electric systems that generate, convert, or control huge amounts of energy almost always involve
devices whose operation depends on magnetic phenomena. Thus, we focus our attention here
on magnetic aspects as related to electric-power engineering. In this chapter we shall proceed
from introductory magnetic-circuit concepts to relatively simple magnetic structures and then to
a consideration of transformers.
The magnetic material determines the size of the equipment, its capabilities, and the lim-
itations on its performance. The transformer, although not an energy-conversion device, is an
important auxiliary in the transfer and conversion of electric energy. Practically all transformers
and electric machinery utilize magnetic material for shaping the magnetic fields which act as the
medium for transferring and converting energy. Transformers are found in various applications,
such as radio, television, and electric power transmission and distribution circuits. Other devices,
such as circuit breakers, automatic switches, and relays, also require the presence of a confined
magnetic field for their proper operation.
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