CONTROL DEVICE AND CONTROL METHOD FOR ALTERNATING CURRENT MOTOR

A control device (30) for performing PWM control of an inverter (14) includes a synchronous PWM control circuit (304) for generating a control command for the inverter (14) by performing PWM control based on a comparison between a sinusoidal voltage command signal for operating the AC motor (M1) according to an operation command and a carrier signal, and a carrier generating unit (306) for keeping an integer as a synchronization number being a frequency ratio between the voltage command signal and the carrier signal, and producing the carrier signal by switching the synchronization number according to an operation state of the AC motor (M1). The carrier generating unit (306) adjusts a phase relationship between the voltage command signal and the carrier signal according to the synchronization number such that an AC current transmitted between the inverter (14) and the AC motor (M1) according to the control command provided from the synchronous PWM control circuit (304) is symmetrical with respect to a boundary between positive and negative portions.