Asynchronous Motor Soft-start Control Study

To reduce the high starting current as asynchronous motors start up directly and eliminate the negative influence that brought about by switching of contact when it starts up with reduced-voltage means, two new methods based on power electronics technology for improving the starting characteristics of three-phase induction motor are presented. One is alternative voltage regulator, the other is alternative voltage chopper. The three-phase regulating circuit- asynchronous motors system and the three phase chopper circuit- asynchronous motors system are analyzed and simulated with MATLAB. The simulation results are excellent. And then the harmonic wave comparison, power factor comparison and circuit comparison between these two methods are described. These comparisons show that alternative voltage chopper is more excellent than alternative voltage regulator. Thus,an open loop control scheme and a closed loop control scheme based on chopper system are introduced. Lastly, a hardware and software design based on micro-controller is presented.