The inspection of transformer inrush currents

The reason of inrush current which is formed when power transformer is energised was searched and the mathematical equation of inrush current was given. By using the relationship between the waveform of voltage and flux, the connection between the instant of switching and inrush current was explained. The technics, which can mitigate this current was represented. Three phase star ? delta connected and three phase star ? star connected transformers were modelled and by using pspice program and simultaneous closing strategy and delayed close among phases was tried. For both situation the waveform of primer current was examined and the results were compared. Keywords: Transformer, Inrush current, power quality