Patent ID: 8378598

Claim:
A motor control apparatus for a polyphase electric motor that includes a rotor, which has a plurality of permanent magnets, and a stator core, which has a plurality of teeth and a plurality of windings, wherein each of the plurality of windings is provided for a corresponding one of a plurality of phases and is wound around each corresponding one of the plurality of teeth, the motor control apparatus comprising: a voltage applying device that sequentially applies a voltage to the plurality of windings on a phase-by-phase basis; a rotational speed sensing device that senses a rotational speed of the rotor, which is rotated by a rotating magnetic field that is generated by sequentially flowing an electric current in the plurality of windings on the phase-by-phase basis upon application of the voltage from the voltage applying device to the plurality of windings; and a controller that corrects the voltage, which is applied to the plurality of windings from the voltage applying device, to control the rotational speed of the rotor in a manner that reduces mechanical resonance generated in the polyphase electric motor when the controller determines that an oscillation frequency of periodic vibrations of the polyphase electric motor, which is obtained by the controller based on the rotational speed of the rotor sensed with the rotational speed sensing device, is a predetermined resonance frequency, wherein the controller corrects the voltage, which is applied to the plurality of windings from the voltage applying device, when the controller determines that the oscillation frequency of the periodic vibrations of the polyphase electric motor coincides with the predetermined resonance frequency, which is one of a plurality of predetermined resonance frequencies that are preset to be compared with the oscillation frequency of the periodic vibrations of the polyphase electric motor at the controller.