Modeling and Simulating of Frequency Conversion Soft Start System Based on SPWM

Abstract

Since over large starting current makes an instant giant grid voltage drop and contacting with current spark can damage the starting device when three phase asynchronous motor is directly started, in order to reduce the impact on the grid and the motor caused by the over large starting current, the present disclosure provides a frequency conversion soft start system based on SPWN. Control system generates IGBT controlled by SPWM pulse control using the regular sampling II method, thus achieving an AC infinitely approaching to a sine wave to open-loop control the motor and implement soft start. The method of frequency conversion soft start based on SPWM may implement a smooth start of the motor with lesser starting current and larger starting torque, thereby largely reducing the impact on the grid voltage and the motor. The experimental results showed that the method of frequency conversion soft start based on SPWM effectively reduces the starting current and implements the motor’s smooth start.