This type of tap-changer has two kinds of products, they are of vertical type and horizontal type. It is usually used in three-phase and single -phase oil-immersed power transformer with frequency of 50，60Hz，highest voltage for equipment 12~ 72.5kV, rated current from 63A to 1000A, it can be regulated on middle or neutral terminal. It can be equipped directly on transformer tank or transformer tank wall working under non-energized condition.