The Design And Realization Of Soft Starter For 3-phase Asynchronous Motor Based On DSP

Three-phase Asynchronous is most used in every field of industry and agriculture, because its simple structure , stable running. With rhe quickly development of machine in production area, the more excellent start performance is desired. In order to reduce the high starting current as Asynchronous motors start up directly and eliminate the negative influence that brought about by switching of contact when it starts up with reduced-voltage. A new method based on DSP technology for improving the starting characteristics of 3-phase Asynchronous motors is presented.A voltage adjusting model with SCR is used in this soft starter. By regulating the amplitude of asynchronous motor's voltage, it realizes the function of the voltage-slope start,the current-limit start, the soft-stop and so on.A soft-starter based on DSP is implemented in this paper. The paper analyses its key circuit and software program structure. The hardware part includes the examining module of voltage and current,the protecting module, LCD module, design and type selection of correlative circuit;the software part includes design of the main program module,LCD subprogram module,the proportional and integral control subprogram module,single neuron control algorithm is adopted to design software which fit for voltage-slope start mode. The model of the soft start system is set up and simulated by MATLAB/SIMULIK, the feasibility of the controller is proved by the simulation results.The mode of discrete frequency is a new method in the control area of soft start,so the theory of discrete frequency method is analyzed. The simulation test has been done with MATLAB in this thesis.The simulation results indicate that the application of discrete frequency method can not only reduce the current impact,but also increase the starting torque.