A step-down transformer is one whose secondary voltage is fewer than its primary voltage. The step down transformer is planned to decrease the voltage from the primary winding to the secondary winding. This type of transformer "steps down" the voltage apply to it.

A power transformer is a electrical mechanism with one winding of wire positioned close to one or more other windings, use to connect two or more alternating-current (AC) circuits jointly by employing the induction among the windings. The winding associated to the power source is known as the primary winding, and the other windings are known as secondary. A transformer in which the secondary voltage is superior than the primary is call a step-up transformer.

The result of current times voltage is stable in each set of windings, so that in a step-up transformer, the voltage increase in the secondary is accompanied by a consequent decrease in the current.

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