Novel approach to reducing the inrush current of a power transformer

An inrush current is a transient current that results from a sudden change in the exciting voltage across a transformer´s windings. It may cause inadvertent operation of the protective relay system and necessitate strengthening of the transformer´s mechanical structure. A novel approach to reducing the inrush current of power transformer, by increasing the transient inductance of the primary coil by changing the distribution of the coil winding is presented. During the period of this study, 30 patterns of 220 V/110-220 V 5 kVA-power transformers with three-layer and four-layer winding structures were developed as demonstrations of the approach. According to field tests and theory, the proposed method successfully limits the inrush current.