To achieve an inverter apparatus for enabling a stable operation of a synchronous motor by a simple control.
A microcomputer B controls an inverter circuit 2 for outputting a variable voltage and a variable frequency and variably controlling a speed of the synchronous motor, detects information on a phase difference between a motor voltage and a motor current, and calculates a duty reference corresponding to an error between the detected phase difference information and target phase difference information. Alternately, the microcomputer B estimates an acceleration of the motor 1 in response to the detected phase difference information, and configures a rotational speed instruction value based on the estimated acceleration. A PWM waveform signal is created, and outputted to the inverter circuit 2 based on sinusoidal wave data corresponding to the calculated duty reference and the configured rotational speed instruction value.
Shuzo Hinode
Seiji Goto
Junko Ohara