Patent ID: 8749184

Claim:
A control apparatus for an electric motor provided with a rotator having a permanent magnet and with a stator for generating a rotating magnetic field by an applied voltage and revolving the rotator, the control apparatus comprising: a rectangular wave inverter that applies a rectangular wave voltage onto the stator of the electric motor to drive the electric motor; a voltage converting section that raises or lowers an output voltage of a direct-current power supply and applies the voltage onto the rectangular wave inverter; an electrical angle acquiring section that acquires an electrical angle of the rotator of the electric motor; and an output voltage command generating section that generates a command for instructing the voltage converting section to output an electrical-angle synchronized voltage whose amplitude ripples in synchronization with a change of the electrical angle of the rotator acquired by the electrical angle acquiring section, wherein, in response to the command generated by the output voltage command generating section, the voltage converting section raises or lowers the output voltage of the direct-current power supply to a voltage indicated by the command and applies the voltage onto the rectangular wave inverter, and wherein an average of the electrical-angle synchronized voltage is a value acquired in correspondence to a difference between a required output power derived based on a torque required for the electric motor and an angular velocity of the rotator and an actual output power derived based on the output voltage and the output current of the voltage converting section.