A 110 V AC input is supplied to a transformer. The output circuit draws a current of 3 A at 220 V. I

Question

A 110 V AC input is supplied to a transformer. The output circuit draws a current of 3 A at 220 V. If the operational efficiency of the transformer is exactly 75%, the current drawn by the primary windings is

Professor PC Thomas Classes · Answer

(b) : The output power $P_{out} = V_s I_s = 220 	imes 3 = 660$ W. Since the efficiency is $\eta = 75\% = 0.75$, the input power required is $P_{in} = P_{out} / \eta = 660 / 0.75 = 880$ W. We know that input power $P_{in} = V_p I_p$. Therefore, the primary current is $I_p = P_{in} / V_p = 880 / 110 = 8$ A.