An open circuit test is performed on 50 H z transformer,

An open circuit test is performed on 50 H z 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

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

1. 250 W and 2.5 W
2. 250 W and 62.5 W
3. 312.5 W and 62.5 W
4. 312.5 W and 250 W

Given 50 Hz transformer

Here	– v	ratio maintains constant .
	f

∴ W_n = Af;
W_e = B – f²
where, A = 10

and B = tan θ =	5	= 0.1
	50

∴ W_n at 25 Hz = 10 × 25 = 250 W
W_e at 25 Hz = 0.1 × (25)² = 62.5 W