The Research On High Start Torque Softstarter With Speed Sensorless

The three phase squirrel cage induction machine is most used in industry, agriculture, traffic area and etc because of its simple structure, stable running, convenient maintaining, and small inertia. With the development of machines in production area, the more excellent start performance is desired. Conventional start methods include direct start and reduced-voltage start can't fit the request for production because they have some localization such as huge current impact, bad adaptive faculty for load, uncontinuous start current, heavy maintaining work. For good start performance, electronic formula soft starter has been used well which uses GTO as main circuit. A high torque soft starter based on speed sensorless is studied in this paper. First, discrete frequency theory is used to improve start torque so that the soft starter can be used in more areas. Second, no speed sensor is used to measure speed which is worked as control parameter so that it will make motor start as preset curve and satisfy those objects that have high speed requires. This paper introduces in detail the soft starter's principle, use MATLAB to simulate the start process, prove the feasibility. It has four start mode: the ramp voltage start, the limit current start, the ramp speed start and the discrete frequency start. The soft starter employs high performance microprocessor 80C196KC to realize digitization, which improve the technology of soft starter, have good foreground, accumulated a lot of experience for the research of high torque soft starter and soft starter for large voltage machines. The experiment results are given in the end. It proves that this soft starter has advantages such as simple structure, high start torque, speed closed loop control etc., develop the technology of soft start, has wide application foreground.