Research On Discrete Frequency-Control Soft Starting Integrated Application System Of Induction Motor Based On DSP

Induction motor soft starters can reduce the current impact on the power supply through regulating voltage. But the reduction in voltage produces a considerable drop in electromagnetic torque, because the starting torque is proportional to the square of voltage, which makes it not suit for starting with high load. Discrete frequency-control technology without changing the main circuit of conventional motor soft starter, controls the thyristors conduct, selects the half cycles pass, then we get a discrete frequency voltage which is lower than the power supply voltage frequency and the starting torque can be increased.Power wastage increases, but efficiency and power factor greatly reduces when induction motors carry with light load. The consuming of energy is very huge. Soft starter has the ability of controlling voltage, when motors run with light load, it can reduce the voltage to increase the efficiency and save the energy. So the novel soft starter should be an integrative application system with the function of soft start and saving energy. It can reduce the start current and the impact on power supply, have enough start torque and fit for overloading starting, improve the efficiency when running with light load and save energy.This paper does some research on integrative application system with the function of discrete frequency-control soft starting and saving energy based on DSP. First, analyze the discrete frequency-control technology, study the condition of generating a balanced system and positive sequences, select the best frequency switch step, and the control method of discrete variable voltage variable frequency control and fuzzy constant current control is proposed. Simulation verifies the advantages of the method in over-loading starting area. Secondly, the expression of load ratio and the best coefficient of reducing voltage when running with light load is got after the analysis of running characteristics of motor and study on influence on motor performance when changing of load ratio. The control scheme for saving energy through regulating voltage is designed using fuzzy control. The simulation verifies the feasibility of this control strategy. Finally, design the discrete frequency-control soft starting and saving energy application system based on TMS320F2812 including the hardware and software design of the system. Study the method of discrete frequency-control soft starting with DSP. The hardware performance of the system can be improved in the use of DSP, and the function of integrative application enhances the applicability of system.