When a transformer steps up voltage, current is stepped down. A step-up transformer at the power station steps up the voltage and consequently steps down the current.

Step-up transformers increase the voltage of the incoming current, while step-down transformers decrease the incoming current’s voltage.

In a step-up transformer, the turns of primary winding constitute a percentage of the windings in the secondary, and vice versa for step-down units. Some autotransformers are of variable action.

Step-Down Transformer Application Power-generation plants produce electricity at 20 kV, which is then stepped up to 440 kV for long-distance distribution.