How core losses affect operating costs for transformers delivering non-sinusoidal loads

Abstract

This paper shows that: the presence of harmonic currents flowing in power transformer windings does increase the core loss significantly and that these extra costs do affect the final transformer operating costs; and that in the absence of a factor, such as the well known 'K-factor' that can be applied to core losses, calculations must be made for losses produced by each harmonic current present. Costs of core losses and load losses are developed for a specific set of three phase coils having cores made from several commonly used core materials. Using a transformer design program that is equipped to calculate core losses for all harmonic currents present, design information is developed for each of the selected core materials. The paper compares the results obtained.