Patent ID: 7830106

Claim:
A controller for a motor that controls the operation of a permanent magnet field type rotary motor that has a first rotor and a second rotor having a plurality of fields constituted by permanent magnets and disposed around a rotating shaft, the controller comprising: a rotor phase difference changing means that changes a rotor phase difference between said first rotor and said second rotor; an inverter that converts a direct-current voltage supplied from a direct-current power supply into a polyphase alternating-current voltage and applies the polyphase alternating-current voltage to an armature of said motor; and an energization controlling means that controls a phase current, which is a vector sum of currents flowing through armatures of the respective phases of said motor via said inverter, according to a predetermined torque command, wherein the controller further comprises: a number-of-revolutions detecting means that detects the number of revolutions of said motor; and a rotor phase difference controlling means that makes said rotor phase difference changing means change said rotor phase difference based on the output voltage of said direct-current power supply, the number of revolutions of said motor, and said torque command in such a manner that the phase current required to produce a torque according to said torque command is minimized.