Analyse And Design Of AC Motor Softstarter

The soft-starter is a new product in the field of power electronics . It is mainly used to start in the mode of voltage slope, limited current amplitude, but also used to soft-stop. It has an outstanding performance in the protection of the start current impact to the electric motor the power grid and the transmission system.This paper theoretically analyzed the thyristor three-pulse-trigger method of the three-phase asynchronous electric motor softstarter on the base of the six-narrow-pulse trigger method. Furthermore it also simulated the six-narrow-pulse and the three-pulse trigger method using the simpowersystem module in MATLAB. On the foundation of the research this paper designed the hardware and software of the electric motor softstarter. The design of the hardware is including the power circuit, the control circuit, the input circuit, the output circuit, the indicator circuit, the reset circuit and the debug circuit. On the basis of the hardware design, the paper edited the timer interrupt program, the High Speed Input interrupt program, the voltage slope program, the limited current amplitude program and the display program. At the same time, this paper made a research of the harmonics appeared during the course of the starting stage.The research of the three-pulse -trigger method is the creative point of this paper. It proved the rightness of the theoretical analysis and the feasibility of the design through practical.