In order to overcome the problems that discrete variable frequency soft start technology has a defect in frequency switching, a discrete variable frequency high torque soft start technology based on multi-mode control is researched. Without changing main circuit of the conventional soft starters, the strategy defines triggering instants of thyristors to include or exclude half cycles of the AC power supply. Therefore, the variations about voltage and frequency applied to the motor are obtained. Using the motor speed as feedback, the intelligent switching control modes of each divider combined ...
