
74 7
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Transformers and Reactors
7.1. Transformer Basics
A review of coupled circuit equations is a good starting point for a
discussion of transformers, because it is wise to keep them in mind
when examining transformer characteristics. First, we examine a sim-
ple pair of coupled coils. Figure 7.1 shows two coils in proximity with
instantaneous voltages and currents as indicated.
The magnetic fields of these two coils have common regions, and
the coils are therefore said to be
coupled
, and a coefficient of cou-
pling,
k
, defines the degree of coupling. If the coils have induc-
tances
L
1
and
L
2
, then a mutual inductance can be defined such ...