The Research Of Motor Soft Starter Base On Switching Transformer

In the thesis, adverse effect on the grid and motor itself could be caused by the higher starting current when the AC motor starting. By the discussion of the traditional motor starting mode, the switching transformer soft starting mode is determined. The solution is more novel soft starting method, for the switching transformer concept is introduced; the problem of power electronic components voltage inadequate is solved. In the higher power motor starting process, by the control of thyristor firing angle, the motor starting current is smoothed, the starting torque impact is reduced and the effect of motor fast smooth is achieved.The switching transformer soft starter is analyzed and modeled in the thesis, the relations of thyristor firing angle and switching transformer impedance are given, the theoretical basis of soft starting is provided. On the basis of it, the Simulink package in the Matlab is used for building the soft starter model which including controller section, over-zero sampling and current sampling section. The relevant simulation contrast experiments are putted up; the results show that the motor starting current is reduced effectively and the torque impact is lowered with this soft starting control system. Based on the above model established and control principle, a fuzzy PID algorithm of adjust system control volume is introduced, which is used in the motor soft starting process, the simulation experiments show that it has better adaptability and robustness.According to the switching transformer soft starter working principle, the relevant software and hardware of soft starting controller are designed. The synchronous over-zero testing circuit, current feedback testing circuit and thyristor trigger unit circuit are included in the hardware section; the process flow chart of specific control thought and part of program are given. Finally, the controller is corresponding tested. The result is meet the design effect.