Use of power electronic converters to suppress transformer inrush current

Abstract

Magnetizing inrush current in transformer results from any abrupt changes of the magnetizing voltage. When a transformer is first energized, a transient current up to 10 to 50 times larger than the rated transformer current can flow for several cycles. This current is called as magnetizing inrush current. Magnitude of this current is dependent on number of parameters like switching instant of supply voltage, residual flux, the hysteresis characteristics of the transformer core, impedance of the primary circuit, etc. This magnetizing inrush current causes system disturbances and damages the transformer windings. To improve this situation inrush current is required to be reduced. This paper discusses inrush current limiters that reduce inrush current at the time of switching of the transformer. Here, inrush current limiters using power electronic converters like diode bridge with DC reactor and voltage source PWM converter are used. Simulations using MATLAB are carried out and results are tabulated. Experiment using DC reactor type inrush current limiter are carried out and results are given in the paper.