Question 2014.S3.36: An open circuit test is performed on 50 Hz transformer, usin......

Wiley Acing The Gate Electrical Engineering [1079382]

An open circuit test is performed on 50 Hz transformer, using variable frequency source and keeping V/f ratio constant, to separate its eddy current and hysteresis losses. The variation of core loss/ frequency as function of frequency is shown in the figure below.

The hysteresis and eddy current losses of the transformer at 25 Hz, respectively, are

(a) 250 W and 2.5 W
(b) 250 W and 62.5 W
(c) 312.5 W and 62.5 W
(d) 312.5 W and 250 W

Step-by-Step

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From the given frequency function

We have $W_{ h }=A f \text { and } W_{ e }=B \times f^2 \text { where } A=10$

and B $=\tan \theta=\frac{5}{50}=0.1$

Therefore at 25 Hz,

$\begin{aligned}& W_{ h }=10 \times 25=250 W \\ & W_{ e }=0.1 \times 25^2=62.5 W \end{aligned}$

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