Abstract: A controller that performs pulse width modulation control of a three-phase inverter circuit includes a three-phase modulation voltage command value generation unit, a two-phase modulation voltage command value generation unit, a voltage command switching unit, and a PWM signal output unit. The voltage command switching unit switches a voltage command value to a two-phase modulation voltage command value when a determination value becomes larger than or equal to a first threshold value, and switches the voltage command value to a three-phase modulation voltage command value when the determination value becomes smaller than a second threshold value, which is smaller than the first threshold value.

Abstract: A controller that performs pulse width modulation control of a three-phase inverter circuit includes a three-phase modulation voltage command value generation unit, a two-phase modulation voltage command value generation unit, a voltage command switching unit, and a PWM signal output unit. The voltage command switching unit switches a voltage command value to a two-phase modulation voltage command value when a determination value becomes larger than or equal to a first threshold value, and switches the voltage command value to a three-phase modulation voltage command value when the determination value becomes smaller than a second threshold value, which is smaller than the first threshold value.

Abstract: The command signal processing unit outputs, when a first PWM frequency command signal is received, a high-PWM frequency command signal such that an asynchronous PWM control is performed at a PWM frequency of a predetermined constant frequency. The command signal processing unit outputs, when a second PWM frequency command signal is received, a low-PWM frequency command signal such that an asynchronous or synchronous PWM control is performed at a frequency lower than the above-described frequency. The PWM frequency control unit controls the PWM frequency such that an asynchronous PWM control is performed if a motor has a rotational speed less than a predetermined rotational speed and that a synchronous PWM control is performed if the motor has a rotational speed greater than or equal to the predetermined rotational speed, when a low-PWM frequency command signal is input.

Abstract: The command signal processing unit outputs, when a first PWM frequency command signal is received, a high-PWM frequency command signal such that an asynchronous PWM control is performed at a PWM frequency of a predetermined constant frequency. The command signal processing unit outputs, when a second PWM frequency command signal is received, a low-PWM frequency command signal such that an asynchronous or synchronous PWM control is performed at a frequency lower than the above-described frequency. The PWM frequency control unit controls the PWM frequency such that an asynchronous PWM control is performed if a motor has a rotational speed less than a predetermined rotational speed and that a synchronous PWM control is performed if the motor has a rotational speed greater than or equal to the predetermined rotational speed, when a low-PWM frequency command signal is input.