Reduction of three-phase transformer magnetizing inrush current by use of point on wave switching

At the time of transformer energization, a high current will be drawn by the transformer. The mentioned current is called transient inrush current and it may rise to ten times the nominal full load current of transformer during operation. Energization transients can produce mechanical stress to the transformer, causes protection system malfunction and it often affect the power system quality and may disrupt the operation of sensitive electrical loads such as computers and medical equipment connected to the system. Reduction and the way to control of energization transients currents have become important concerns to the power industry for engineers. One of the methods to reduce inrush current is use of point on wave switching at the time transformer is initially connected to supply. This paper discusses the simulations and the experimental results on a three-phase transformer for reduction of inrush currents. An electronic three-phase switching controller has been designed and some thyristors were used for switching power to the transformers.