Classical eddy current losses in Soft Magnetic Composites

1 a Corresponding author: [email protected] 2 This paper deals with the problem of loss evaluation in Soft Magnetic Composites (SMC), focusing 2 on the classical loss component. It is known that eddy currents can flow in these granular materials at 3 two different scales, that of the single particle (microscopic eddy currents) and that of the specimen 4 cross-section (macroscopic eddy currents), the latter ensuing from imperfect insulation between 5 particles. It is often argued that this macroscopic loss component can be calculated considering an 6 equivalent homogeneous material of same bulk resistivity. This assumption has not found so far clear 7 and general experimental validation. In this paper, we discuss energy loss experiments in two different 8 SMC materials, obtained using different binder types, and we verify that a classical macroscopic loss 9 component, the sole size-dependent term, can be separately identified. It is also put in evidence that, 10 depending on the material, the measured sample resistivity and the equivalent resistivity entering the 11 calculation of the macroscopic eddy currents may not be the same. A corrective coefficient is therefore 12 introduced and experimentally identified. This coefficient appears to depend on the material type only, 13 the role of sample shape and/or cross-sectional area being irrelevant. An efficient way to calculate the 14 macroscopic classical loss in these materials, based on a minimum set of preliminary experimental 15 results, is thus provided. In this way, a reliable procedure for loss separation, whatever the sample size, 16 can be implemented. 17 18