Prediction for Hysteresis Loops and Losses of Nanocrystalline Under Asymmetric Duty-Cycle Square-Wave Voltage Excitation

Nanocrystalline soft magnetic cores are promising for medium-frequency transformers. However, accurate prediction of their hysteresis behavior under asymmetric duty-cycle square-wave excitation remains hard because positive and negative magnetization processes are different. This study proposes a dynamic hysteresis and loss prediction method that uses only sinusoidal measurements. Hysteresis loops under square-wave excitation with different duty cycles were first measured. Based on the consistency between loss separation and field separation, the total magnetic field was decomposed into hysteresis, classical eddy current, and excess loss field. The quasi-static hysteresis field was determined using the inverse Preisach model, and the classical eddy-current field was calculated considering the skin effect. An equivalent-frequency method was then developed to calculate the excess loss field during the positive and negative voltage stages. Validation was performed on a nanocrystalline ring core at 2 kHz and 5 kHz over a duty-cycle range of 20–80%. The maximum loss error and normalized dynamic time warping error were 4.767% and 6.113%, respectively. The proposed method accurately predicts asymmetric hysteresis loops and losses without requiring square-wave measurements, thus providing an efficient approach for magnetic material evaluation in medium-frequency transformer design.