Approximation and Prediction of AC Magnetization Curves for Power Transformer Core Analysis

Based on the latest experimental results of two different modern graded grain-oriented electrical steels measured up to 2 T under ac, the existing 10 popular analytical approximation functions for ac magnetization curves are critically evaluated. None of them are capable of making a satisfactory approximation over the full useful range (0-2 T). Therefore, a new simple explicit empirical function is proposed that is simple to use (six parameters) and sufficiently accurate (adjusted R² ≥ 0.9992) to represent the ac magnetization curve. The empirical function is also shown to be suitable (adjusted R² ≥ 0.9913) for extrapolating the ac magnetization curve into the high-flux-density region (1.80-2 T) when only using the available experimental data in the region 0-1.80 T from steel manufacturers.