Research And Implement Onasynchronous Motor Soft Starter Based On Chopper Regulator

With the quick development of the modern society, as the three-phase asynchronous motor has a simple structure, strong and reliable, dynamic performance, low cost, it has been widely used in industrial and agricultural production, transportation, defense companies and people in many areas of daily life. So, the starting problem of induction motor is rather important. How to properly select the main circuit topology and the hardware and software design is the core of this article.Conventional thyristor regulator soft-starters there has a defect of large harmonic content and low power factor; three-phase full-controlled PWM inverter soft starter costs are relatively high, but compared to the thyristor which has higher pressure endurance, its system capacity is relatively small. Therefore, this paper chooses chopper regulator soft start. Chopper regulator soft starter is used in self-turn-off device IGBT, the trigger signal is not synchronized with the main circuit, the dynamic response is faster. Therefore, we can eliminate the low frequency harmonics by increasing the switch turns on the way, and we can also facilitate the design of the filter to filter out high frequency harmonics, so that the output waveform is very closed to sinusoidal. And the new topology can greatly improve the power factor of the induction motor.The main innovation of the hardware circuit is proposed a double-CPU architecture: the lower computer is seemed as the main control unit, responsible for the signal detection, to protect the main circuit, triggering IGBT turn-on, and so on; the upper computer is primarily a monitoring unit, timely communicates with the main control unit, mainly to complete the soft-start function of some parameters and display settings and failure, and so on, very good working with the lower computer.Finally, MATLAB simulation verified the feasibility of this vision, and we built an experimental platform. Through the experiments, we can verify the correctness of the following theory: compared to the direct starting mode of the asynchronous motor, chopper regulator soft-start can successfully limit starting current of the stator in about three times the rated value, speed to rise slowly, reaching a steady the purpose of the soft start; compared to traditional thyristor soft-start, chopper regulator soft-start can eliminate a large number of harmonic components of the current in the stator side, and improve the power factor of induction motor.