Page 46 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

TRANSFORMERS

TRANSFORMERS 3.3

i (t) i (t)
S
P

v (t) N P N S v S (t)
P

(a)

i (t) N P N S i (t)
S
P
(t) v (t)
v P S

i (t) N P N S i (t)
P
S
v P (t) v (t)
S
(b)
FIGURE 3.2 (a) Sketch of an ideal transformer. (b) Schematic symbols of a transformer.

I 1
P
I S a

The phase of angle V is the same as the angle of V , and the phase angle of I is the same
P S P
as the phase angle of I .
S
Power in an Ideal Transformer

The power given to the transformer by the primary circuit is

P V I cos
in P P P
where is the angle between the primary voltage and current. The power supplied by the
P
secondary side of the transformer to its loads is
P V I cos
out S S S

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