An AC motor control circuit particularly suitable for motors having permanent magnet rotors, and stators which are supplied with AC current from an inverter. A current detection (33) detects the DC current input to the inverter (29) and produces an output signal which is supplied to a power factor calculation circuit (36). The output from this circuit is supplied to a voltage and frequency calculation circuit (38) whose output is in turn supplied to a drive circuit (38) which produces pulse-width-modulated drive signals for the transistors of the inverter (29).
