PURPOSE: To reduce circulating currents by superposing a Δ winding and a Y winding in the axial direction of windings, connecting the Δ winding and one winding disposed opposed in the radial direction of the windings and the Y winding and another winding of the windings in parallel and forming a primary winding.

CONSTITUTION: When different currents flow in a Δ winding 2 and a Y winding 3, currents corresponding to the ampere turn of the Δ winding flow through an upper primary winding 11 oppositely faced to the Δ winding, and currents corresponding to the ampere turn of the Y winding flow through a lower primary winding 12 oppositely faced to the Y winding. Consequently, ampere turns are balanced among the primary windings and secondary windings respectively independently in an upper section and a lower section, thus reducing eddy currents generated in the windings. The magnitude of circulating currents flowing back to the Δ winding and the Y winding is diminished to approximately several % to the utmost in consideration of the main body of the sextuple harmonic of power frequency and proportion to frequency of reactance in circulating currents generated by the difference VS of pulsating voltage between the Δconnection and the Y connection, thus displaying a practically sufficient reduction effect.