Tap changer

mechanism to change turn ratios in transformers

A tap changer is a component of a transformer. It controls the transformer's output voltage by adjusting its winding ratio within some range of step levels. The tap changer can be done manually or automatically and either when the transformer is energized (On Load Tap Changer; OLTC) or when it is off (Off Circuit Tap Changer; OCTC).

Tap changer