The harmonics of the power supply are greatly reduced by polyphase rectifier at the same time of high efficiency/high force rate. A single frequency converter passes the Ministry of Economy, Trade and Industry's harmonics benchmark. In addition, through the original PWM mode, it can effectively restrain the surge voltage which has a bad effect on the motor, so that the standard motor has been set to run safely. Vector control by its own speed sensor (option), can not be misled by load changes to provide very stable operation.