Patent ID: 7548038

Claim:
A controller for a motor adapted to control an operation of a permanent magnet field type rotary motor having a first rotor and a second rotor, which have a plurality of fields made of permanent magnets and which are disposed around a rotating shaft, by field control carried out by changing a rotor phase difference as a phase difference between the first rotor and the second rotor, the controller comprising: an inverter circuit for converting DC power supplied from a DC power source into multiphase AC power to be supplied to an armature of the motor; a rotor phase difference command value determining means for determining a command value of the rotor phase difference in a direction in which a magnetic flux of a field of the motor increases in the case where the magnitude of a resultant vector of the voltages between the terminals of armatures of individual phases of the motor is smaller than a predetermined voltage that has been set to be not more than an output voltage of the DC power source; and a rotor phase difference changing means for changing the rotor phase difference on the basis of a command value of the rotor phase difference.