When the secondary winding of a transformer is completely shorted, what happens to the primary current?

When the secondary winding of a transformer is completely shorted, it creates a very low resistance path for the current. This situation significantly increases the current flowing in the primary winding due to the principle of electromagnetic induction. The transformer operates on the principles governed by Ohm's Law and the relationship between voltage, current, and impedance.

In a normal operating circumstance, the current in the primary winding is determined by the load connected to the secondary and the turns ratio of the transformer. However, with a short circuit on the secondary, the secondary voltage drops to almost zero, while the impedance tends to approach zero as well, leading to the primary experiencing a high current draw.

This high current can potentially reach levels much higher than normal operational levels, causing overheating and possibly damaging the transformer if not adequately protected by a circuit breaker or fuse. Hence, it is appropriate to say that the primary current becomes high under these conditions.