Patent ID: 8129931

Claim:
A motor control device which controls a permanent magnet motor including a rotor provided with a permanent magnet having such a low coercive force that a magnet flux content is changeable, the device comprising: a drive unit which drives the motor by energization of a winding of the motor; a magnetization control unit which energizes the motor winding via the drive unit, thereby changing a flux content of the permanent magnet motor; a current detector which detects current supplied to the motor; a vector control unit including a speed/position estimation unit which carries out an operation based on the motor current, an output voltage of the drive unit and a motor constant thereby to estimate a rotational speed and rotational position of the motor, the vector control unit carrying out a vector control of the motor via the drive unit; an induced voltage detector which detects an induced voltage of the motor based on the rotational speed, motor currents obtained by the vector control unit, output voltages of the drive unit, a winding inductance that is the motor constant and a winding resistance; an induced voltage command determining unit which determines an induced voltage command based on the rotational speed and an output torque of the motor; and a magnetization current determining unit which determines an amount of energization based on the induced voltage of the motor and the induced voltage command.