Harmonic performance of single phase transformer with DC biased

Abstract

Direct current (DC) flowing through the earthed neutrals of transformer windings causes a DC component in magnetizing current. Owing to nonlinearity, the waveform of this current is strongly distorted. A high enough DC component in the current on the secondary side of a transformer causes distortion of the primary side current. Prediction of such distortion relies on the availability of magnetization curves that extended deep enough into saturation. DC bias of transformers will also generate some important effects on power transformers. The paper presents harmonic characteristics of transformer excitation current resulting from DC offset currents on the load side of single phase transformer. The results of this study are useful in understanding transformers as harmonic sources and the even harmonics are significant in case of DC biased rather than in normal AC supply. Keywords: Transformer, harmonics, dc bias, magnetizing current