Medium Voltage Solid-state Soft Starter Control System Research And Design

Asynchronous motors are widely used in industry and transportation area because of its simplicity of structure and reliability of running. But it will give impulsion to the electric grid when it's started directly. To the pump-load, the sudden-stop will cause water hammer effects, even crack the pipe-line. In China, the solid-state soft-starters are diffusely used in low-voltage motor area. But our country imported all the mid-voltage soft-starter before. This paper studied the control system of the mid-voltage soft-starter, which based on the thyristor. The paper also introduces the starting, running and stopping methods of the asynchronous motors. The protection, man-machine conversation and application are also included. Whereafter, the theory of adjusted AC voltage is discussed. The control principle and the hardware resource are described, too. Analyzing the arithmetic of the limited current soft-starter and real power closed-loop soft stop, the paper presents the flow chart which based on DSP, the CPLD design and dependability of the software. In the end, this paper introduces the EMI, EMC test and the load experimentation. The correctness of the control system is demonstrated on the 6 kV and 10kV motor with pump-load.