EFFECT OF DC VOLTAGE ON AC MAGNETISATION OF TRANSFORMER CORE STEEL

Philip Marketos – Anthony J. Moses – Jeremy P. Hall

   Primary windings of transformers are fed with alternating sinusoidal voltage, but often this voltage contains small DC offset due to unsymmetrical voltage levels. To emulate such working conditions in a controlled environment (Epstein frame) the excitation waveforms were emulated as a DC voltage superimposed on an AC waveform. This resulted in non symmetrical excitation of the core steel. The harmful effects of this type of excitation on magnetising current, power loss and the B-H characteristics of the steel are shown.

Keywords: electrical steel, power loss, DC bias

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