Analysis and Simulation Research on the Transition Frequency of Discrete Frequency Control Soft Starting

In order to improve the starting performance of the motor, based on motor soft starting, this paper introduces the principle of discrete frequency-control soft starting and selects the switching steps of discrete frequency-control. At first, the specific factors which affect the starting torque of 16.7Hz are discussed and the most positive sequence of 16.7Hz is decided. Then the control strategy of constant ratio between voltage and frequency is proposed to make the starting torque smooth. At last, we simulate the process of discrete frequency-control soft starting, and the starting performance with or without 25Hz is compared, the results verify the analysis conclusion.