Abstract: Aiming at the problems of large starting current and bus voltage drop when three-phase asynchronous motor starts, a soft starting control system for heavy-load starting is designed. First of all, based on the motor control theory, the pulse generation module, three-phase voltage regulation module and PID ( Proportional- Integral-Derivative) control closed loop are built, and the soft start control system is designed to control the terminal current and voltage of the asynchronous motor. Secondly, based on the Simulink software, according to the actual data of the feed pump motor of a coal-fired unit in Heilongjiang Province, the soft start control model is built and simulated. Finally, the field test is carried out, and the test results are similar to the simulation results. The results show that the model can effectively limit the starting current of asynchronous motor and reduce the influence of water pump motor start-up on other equipments at the busbar under the condition of heavy load starting. It provides a reference for the heavy-load start-up of the asynchronous motor. 

Key words: soft start, feed water pump, proportional-integral-derivative (PID) control, control method