Computation of Eddy Current Losses in Soft Magnetic Composites

We compute the classical eddy current losses in soft magnetic composite (SMC) materials, taking into account the eddy current paths appearing at the scale of the sample cross-section because of random contacts between the grains. The prediction of this loss contribution is a challenging task, because of the stochastic nature of the associated conduction process. We start our study from an identification of the statistical properties of the contacts between grains, starting from resistivity measurements. We then develop a numerical loss model for random grain-to-grain conduction, by which we demonstrate that the classical loss in SMCs can be decomposed into a contribution deriving from the eddy currents circulating inside the grains and a contribution due to the macroscopic eddy currents flowing from grain to grain via random contacts. An experimental validation of this model is proposed for a representative SMC material, where the magnetic losses are measured in ring samples with a range of cross-sectional areas.