MOTOR DRIVING DEVICE

PROBLEM TO BE SOLVED: To minimize iron loss of a motor with no use of complicated control mechanism and calculation circuit at the time when driving the motor by supplying an AC power to the motor by PWM control.SOLUTION: The carrier frequency within such range as corresponds to the iron loss between a minimum value and 1.04 times the value (1.02 times is preferred), in the relationship between iron loss of a motor M and carrier frequency, is taken as a carrier frequency of triangular wave generated by a triangular wave generating part 72. Based on a PWM signal S which corresponds to the result of comparison between a voltage command signal and triangular wave of the carrier frequency, the operation of an inverter 50 (IGBT) that supplies AC power to the motor M is controlled.