Estimation Model of Core Loss Under DC Bias

The current and loss of a transformer increase significantly under DC bias, which cause overheating and insulation aging. Depended on the Jiles-Atherton (JA) hysteresis theory, an estimation model of the core loss under DC bias is proposed in this paper. First, based on the iron loss separate theory, the origin JA model without DC bias is extended to JA dynamic hysteresis model considering the frequency-dependent eddy current loss and the anomalous loss. Second, a DC bias experiment is built by using Epstein frame, from which the hysteresis loss and the dynamic loss coefficients of the core are obtained. Finally, the relationship between DC bias and the dynamic loss coefficient is analyzed. The dynamic loss coefficient is normalized and fitted, and JA dynamic hysteresis model is revised by using the fitted results. The calculation results are compared with the measurement from the Epstein frame, which demonstrates the effectiveness of the method.