Power conversion apparatus for converting direct current to polyphase alternating current

A motor system comprising:

• an input pin connected to a direct current power source;
• a plurality of phase coils corresponding to each phase of a polyphase alternating current;
• a plurality of legs disposed between the input pin and the phase coils;
• a smoothing capacitor disposed between the input pin and the legs;
• a plurality of carrier signal generators configured and arranged to independently generate and transmit a plurality of carrier signals, respectively, the carrier signals having mutually different frequencies, with the carrier signal generators configured and arranged to set a lowest frequency of each of the carrier signals above an audible band;
• and
• a gate signal generator unit configured and arranged to generate and transmit an on/off signal obtained by comparing corresponding one of the carrier signals transmitted from the carrier signal generators and a command value of each phase of the polyphase alternating current.

A power conversion apparatus for converting direct current from a power source to polyphase alternating current, the power conversion apparatus comprising:

• carrier signal generating means for independently generating and transmiting a plurality of carrier signals, the carrier signals having mutually different frequencies, with the carrier signal generating means configured and arranged to set a lowest frequency of each of the carrier signals above an audible band;
• gate signal generating means for generating a plurality of on/off signals by comparing a command value of each phase of the polyphase alternating current and corresponding one of the carrier signals received from the carrier signal generating means;
• and
• switching means for converting the direct current to each phase of the polyphase alternating current based on the on/off signals transmitted from the gate signal generating means.