To solve the problem that the conventional three-phase on-load voltage-phase regulating transformer is composed of a main transformer and a separate phase shifter, and needs an area for installing both the main transformer and the phase shifter to result in a factor of raising the transformer station total cost.

A voltage regulating tap winding is added to the main transformer, and two phase shifting tap windings are provided per phase. The phase shifting tape windings of other phases are electrically connected at a phase of 120° through a phase shifting two-phase on-load tape change to generate a voltage at a phase of 90° to these phases, so that the voltage and phase are adjustable at the main transformer.