Iron loss comparison of standard SiFe and nanocrystalline materials for power transformers in a dual active bridge converter

This paper presents an analysis of different structured ferromagnetic materials for medium frequency applications. Metrological characteristics are performed at standardized instruments made by Brockhaus, i.e., Epstein frames and ring coil testing module. The final application is a transformer core used in a galvanically isolated phase-shifted dc-dc converter. The efficiency of a dual-active-bridge (DAB3) DC-DC converter is influenced, among others, by the iron losses of the medium frequency transformer. The iron losses of grain-oriented SiFe, non-oriented SiFe and nanocrystalline materials are measured at medium frequencies up to several kilohertz under sinusoidal excitation. The IEM-5-Parameter iron loss formula, which is based on semi-physical parameters, is used to evaluate the material characteristics. In addition, the excitation signal is adapted to the DAB3 application. The signal is examined by using a fast Fourier transform. The semi-physical iron loss separation model is adapted to consider the occurring harmonics in polarization.