PURPOSE:To reduce noise of a motor and to suppress a loss by controlling a carrier frequency in cooperation with an output frequency of an inverter or temperature, load current of a controllable element. CONSTITUTION:An essential section is composed of a DC power source 100, an inverter 200, a motor 300, a reference voltage generator 400, a carrier generator 500, a PWM circuit 600, a driver 700, a temperature detector 800, an output frequency setter 900, etc. The generator 500 determines a carrier frequency in cooperation with temperature of a controllable element of the inverter, the output frequency or output current of the inverter. When a detected temperature or rotating speed of a motor is low or an output is small, the carrier frequency is raised to suppress generating noise. When the detected temperature is raised and the output current becomes large, the carrier frequency is reduced. Thus, noise, loss can be suppressed to low values.
展开▼
