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960 ⏐⏐⏐ TRANSFORMERS
Primary
(a) Core type
+
I1 = — 1 A
20
+
I2 = 1 A
+ +
+
I1 = 1— 1 A
20
— 1 A
20
Es = 6 V
–
+
VR = 120 V Ep Es VL = 6 V Vg = 120 V Ep = 120 V
–
–
Laminated sheets
Secondary
–
–
(b) Shell type
FIG. 21.37
Types of ferromagnetic core construction.
(a) (b)
Primary
Secondary
height of only 0.65 in.) applications in power, control, and instrumentation
applications. There are actually two transformers on the same core,
with the primary and secondary of each wound side by side. The
schematic representation appears in the same figure. Each set of terminals
on the left can accept 115 V at 50 or 60 Hz, whereas each side of
the output will provide 230 V at the same frequency. Note the dot convention,
as described earlier in the chapter.
The autotransformer [Fig. 21.39(b)] is a type of power transformer
that, instead of employing the two-circuit principle (complete isolation
between coils), has one winding common to both the input and the output
circuits. The induced voltages are related to the turns ratio in the
same manner as that described for the two-circuit transformer. If the
proper connection is used, a two-circuit power transformer can be
FIG. 21.39
(a) Two-circuit transformer; (b) autotransformer.
–
FIG. 21.38
Split bobbin, low-profile power transformer.
(Courtesy of Microtran
Company, Inc.)
+
–
I 2 = 1 A
+
V L = 126 V
–