Effect of Full and Half Load on the Copper Losses in Transformer

 Statement: The copper losses of a Transformer at Full load is 200 watt, At Half Load, the losses will be:

Correct answer: d) 50 Watt.

Explanation: The copper losses in Transformer depends on current and resistance by the relationship:
Copper Losses ∝ I² R

Now if we assume input voltages as 220 V, then I = P/V = 0.909 A which is the load current.
and Resistance = V/I = 220/0.909A = 242 ohm.

Now for half load the current will also be halved which is 0.454. Now copper losses are:
Copper Losses = I² R = (0.454)² (242 ohm) = 50 A.

So d) is the correct answer.

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