A transformer is designed to convert an AC voltage of 220 V to an AC voltage of 12 V. If the input terminals are connected to a DC voltage of 220 V, the transformer usually burns. Explain.

Question

Philoid · Accepted Answer

Ideally, we can consider a transformer to be a purely inductive circuit with inductance L.

Hence, the voltage in this case is given by , where i = current, t = time, L = inductance.

⇒

Integrating on both sides, we get

⇒

For a DC source, the current across the inductor increases with time and after a certain amount of time, can reach a very large value. This burns the transformer. (Ans)