Study of Analysis and Experiment for Ability to Withstand DC Bias in Power Transformers

DC bias in power transformers leads to strong core saturation and thus nonlinearly inferior operation. This paper analyzes the ability of power transformers to withstand the dc bias by novel analytical criteria. The proposed criteria are obtained from the nonlinear equivalent circuit, which considers the effects of nonlinear inductances. The validity of the proposed analytical criteria is verified by the finite-element analysis results and experimental results, which indicates that the proposed analytical criteria are effective to evaluate the ability to withstand the dc bias of power transformers.