Research On High-voltage Asynchronous Motor Soft-starter Based On Variable Reactor

The direct-on-line start of high voltage asynchronous motors can generate great impact current, which will cause the damage to motor itself and contamination of the power supply system. Therefore, reduced-voltage motor starter is usually employed to suppress this current impact. While, the traditional approach of whose voltage regulation is discontinuous, and this will result in secondary current impact during the state process. Electronic soft starter based on the silicon controlled voltage stabilized AC adjuster can resolve the start problems of low-voltage motors excellently. However, because of the voltage-limit of thyristor, it can't used in the condition of high-voltage.This paper introduced a high-voltage motor soft starter based on variable reactor, which is used to isolate low-voltage control loop from high-voltage working loop. Thus the problem of voltage-limit is resolved skillfully. The mathematics model of the variable reactor is introduced. When the motor is starting, the transformer can be look as a varying reactance along with the turn-on and turn-off condition of thyristor. The paper also analyzes the influence that power factor angle to the motor starting, proposed that the current oscillation, during the soft-start of three-phase induction motor under light-load, can restrain by a closed-loop power factor control method.The paper summarized the application status of electronic soft-starter, point out its limitations in the high-voltage situation, and then analyzed the basis of adding soft-starter quantitatively. On the base of analyzing to high-voltage motor based on series-connected thyristors, the paper discussed the structure, principle and the advantage used in high-voltage motors of soft-starter based on variable reactor. The better soft start method is adopted which is voltage-ramping combing current-limit.At last, a simulation model of high-voltage motor soft-starter based on variable reactor is built, the simulation results show the feasibility of proposed scheme. This soft-start approach can resolve the voltage limitation of thyristor and optimize the starting performance of high-voltage motor.