Invited talk by winner of IFAAMAS Victor Lesser Distinguished Dissertation Award

A pair of switching elements are provided between a source of direct current and a bridge type inverter for commutating together. A commutating circuit having a capacitor is connected in parallel with the bridge type inverter to rapidly commutate the bridge type inverter. The commutating circuit operates so as to apply a voltage of inverse polarity to the thyristor of the inverter when a switching element operates.