To make parts exchange according to various supply voltages unneces sary, by finding a controlled state corresponding to a voltage value obtained from data outputted by a DC voltage detecting means, and controlling an invert er section and a motor so as to be in this controlled state.

A CPU 10 generates a control signal CL at each specified sampling timing, and gives it to an analog-to-digital converter 91 through a photocopier 92. The analog-to-digital converter 91 compares a voltage VDH obtained by dividing the converted output voltage of a converter section 2 by a voltage dividing resistor 4 with a reference voltage VS given separately, and converts it into a serial signal VOUT. This serial signal VOUT is set to the CPU 10. The CPU 10 reads this, computes the output voltage VDC of the converter section 2, and controls a regenerative power absorbing part 5, an inverter section 6, and a motor 8 so as to correspond to the level of a DC voltage to be given to the inverter section 6 from the converter section 2.