Patent ID: 7688604

Claim:
An AC voltage output apparatus, comprising: a first polyphase AC motor including a star-connected first polyphase winding as a stator winding; a second polyphase AC motor including a star-connected second polyphase winding as a stator winding; first and second inverters connected to said first and second polyphase windings respectively; and a control device controlling said first and second inverters such that an AC voltage having a prescribed frequency is generated across a neutral point of said first polyphase winding and a neutral point of said second polyphase winding when a rotor of said second polyphase AC motor is stopped; wherein said control device includes a harmonic generation unit generating a harmonic voltage instruction having a phase opposite to a harmonic of counter-electromotive force generated at the neutral point of said first polyphase winding, based on number of revolutions of said first polyphase AC motor when a rotor of said first polyphase AC motor revolves, and a signal generation unit generating a control signal for controlling said first inverter based on a voltage instruction obtained by superposing said harmonic voltage instruction onto a voltage instruction of each phase of said first polyphase AC motor and outputting the generated control signal to said first inverter.