The Research Of Soft Starter About Asynchronous Motor Based On The On-off Transformer

Asynchronous motor is largely used in the fields of industry, transportation and others. In these fields, middle-voltage asynchronous motor has big requirements. Buts, it will produce big current when starting directly; usually the current can reach 5-7 times of nominal, sometimes the current even reach 15 times. In this paper, the soft-starter is based on the transformer so that it can work under the middle voltage. In order to avoid the high voltage and reduce the starting current, a pair of anti-parallel SCR is to be connected with the second winding of the transformer and the primary winding is directly connected with the motor's stator.The appliance which is researched in this paper can work at the range of voltage which is 6kv-10kv.In this paper, the development of the soft-starter is introduced in detail, especially for the middle-voltage one. Besides the introduction of the theory of the on-off transformer and the characteristic of middle-voltage starter, the method of control according to the fuzzy is pointed out. As for the problem the high current and the vibration of the torque, the double closed loops which include the current and power factor angle are worked out. With the using of the loop of the current, the current of starting can be controlled efficiently. At the same time, the problem of vibration is reduced more or less under the working of the power factor angle loop.Based on the understanding of the starter, the associated software and hardware are designed. Meanwhile, the function of these can satisfy the requirements of the working situation after the experiment. In order to improve these, there are many pictures put in the paper which are taken in the lab and the working station.At the beginning of this paper, the theory of the on-off transformer is discussed and the mathematic model of it is gotten. On the basis of these fruits, the...