Application research of PWM inverter in the cascade speed control system of inner-feedback motor

With the development of power electric technology, the performance of the cascade speed-regulation technology have improved, especially the chopping cascade system of inner feedback motor. The cascade speed motor has high harmonic and low power factor when the motor running in low speed station. However, the power factor and harmonic can improve by adopting three-phase voltage-source PWM inverter, because the three-phase voltage-source PWM inverter can be controlled to obtain unit power factor. In this paper, the principle of cascade speed system adopting PWM inverter is analyzed, and some simulation results show that the power factor can be improved, especially in low speed.