Loss Analysis of Nanocrystalline Cores for High Frequency Transformer in Power Electronics Circuits

Nanocrystalline cores have a superior higher permeability, which makes them smaller size and weight compared to conventional cores. This makes nanocrystalline more suitable to many applications, such as electrical vehicles, EMI filters, so on. This paper compares power-conversion performance between nanocrystalline and conventional ferrite cores of similar volume. A 1 kW dual-active bridge converter is used for testing the transformers at 50–80 kHz. Theoretical losses are calculated from datasheets and compared with the experimental losses for both the nanocrystalline and ferrite. Results reveal that the theoretical and experimental losses match for ferrite transformer but there exists a significant difference in case of the nanocrystalline transformers. Further investigation is needed to explain this mismatch. Therefore, FEM analysis using COMSOL Multiphysics is performed. Due to the nonlinearity of the material, a homogenized anisotropic configuration is adopted. The experimental and FEM results suggest that the mismatch is possibly because of the circulating eddy currents between the ribbons, which must be taken into consideration during the modeling of the losses for nanocrystalline cores.