Patent ID: 7615948

Claim:
A controller for a motor comprising: a plurality of drive circuits for driving a plurality of permanent magnet type rotary motors; a DC power source for supplying DC power to the drive circuits; an output voltage changing means for changing an output voltage of the DC power source; a motor loss estimating means for determining, on each of the motors, an estimated value of a loss, which is incurred when driving a motor, on the basis of at least one of a loss in the drive circuit and a loss in the motor driven by the drive circuit; and a voltage difference reduction controlling means which carries out, when driving the plurality of motors by the plurality of drive circuits, supply voltage changing processing to change the voltage of DC power supplied to the drive circuit for driving a motor that has a largest estimated value of loss by the output voltage changing means so as to reduce a difference between a phase voltage, which is a resultant vector of the voltage between the terminals of an armature of each phase of the motor and a first target voltage, which is set on the basis of an output voltage of the DC power source.