Mechanical power outputting apparatus and inverter

摘要

A direct-current power supply 530 connecting the negative pole bus 528 of an inverter circuit 524 and the neutral point of a motor 522 and a capacitor connecting the positive pole bus 526 of the inverter circuit and the neutral point of the motor are provided for performing the switching control of the transistors T1-T6 of the inverter circuit on the basis of a phase voltage command value formed by the addition of a direct-current component and an alternating-current component. The voltage between the terminals of the capacitor is controlled on the direct-current component, and the driving control of the motor is performed on the alternating-current component. The supply voltage of the direct-current power supply can be made to be lower than a voltage necessary to drive the motor. Moreover, the withstand voltage of the capacitor can be made to be smaller and the relay circuit can be simplified in comparison with an apparatus equipped with a capacitor connected between the positive pole bus and the negative pole bus of an inverter circuit. As a result, downsizing of an apparatus and reduction in costs can be achieved, and the durability and the reliability of the apparatus can be improved.