Emulating Full-Load Testing of Air-Cooled Nanocrystalline IHT at Zero Power

Abstract

High-power high-frequency air-cooled induction heating transformers, mostly used as current multiplier and isolation purposes, are custom designed. For their reliable performance and long life, the thermal evaluation at rated load is necessary. Creating an equivalent load as a test facility for reliability testing of such type of transformer is difficult. Characteristics of such loads drastically change after Curie temperature. Moreover, prolonged heating could increase the nearby ambient temperature and, more importantly, the traditional heat run test wastes large amount of energy. Whenever the coil is energized, windings of transformer draw respective rated current; even at no-load condition, the copper loss is at rated value. While both windings drawing rated current at a desired frequency, using the concept of localized eddy current loss as well as excess eddy current loss, this article proposes a novel method to inject requisite core loss to the magnetic circuit to emulate the characteristics of full-load condition but the power drawn from the transformer would be zero. The proposed idea would be validated where only a 200-W resonant inverter would be used to inject power loss equivalent to full-load condition of 30-kW transformer to emulate the heat run test.