Anisotropic Characterization of Nanocrystalline Alloys for Inductive Power Transfer

Abstract

Nanocrystalline alloys are of interest in inductive power transfer (IPT) due to their higher saturation limits, permeability, and thermal conductivity compared to conventional Mn–Zn ferrites. However, due to the higher electrical conductivity of nanocrystalline alloys, they have significant eddy current losses. This article demonstrates a core loss measurement method that considers the anisotropic behavior of fractured and laminated nanocrystalline ribbons. The proposed method uses a Maxwell coil to generate a uniform magnetic field, while samples of nanocrystalline ribbon are mechanically rotated within the magnetic field. Core loss is then measured using a hybrid calorimetric method that combines steady-state and transient measurements, enabling quick and accurate acquisition. The measured core loss of three different nanocrystalline ribbon samples is compared at $85 \,\rm{k}\rm{Hz}$ for IPT applications. Finally, a modified Steinmetz equation dependent on the magnetic flux angle is proposed.