Model for the evaluation of no-load losses of three-phase transformers with distorted fluxes

This paper considers the influence of the winding connection and the distortion in the supply voltage on the no-load loss in three-phase core-type transformers. With sinusoidal supply voltage, this analysis shows that the no-load loss is greater in delta connection than in star connection of the supplied side and that, in the latter case, it depends on the connection of the secondary side: the loss is greater if the secondary is delta-connected than star-connected. The differences might be even of the order of 5-6%. The distortion of the supply voltage increases the previous figures, i.e., the no-load loss is greater than that with sinusoidal voltage if the winding is delta-connected. The paper also discusses the formula of the Standard for the correction of the measured no-load loss to the sine wave basis and proposes a circuit model for computing the effect of the distortion of the supply voltage.