3-D Eddy Current and Fringing-Flux Distribution in an Axial-Flux Permanent-Magnet Synchronous Machine With Stator in Laminated Iron or SMC

This paper compares the iron losses generated by the concentrated excitation windings of an axial-flux permanent-magnet synchronous machine (AFPMSM) in the stator core elements constructed with laminated silicon steel sheets (LSSS) or with soft magnetic composite (SMC). As the flux mainly flows in one direction, we use grain-oriented LSSS. In order to provide a very accurate comparison, individual laminations are modeled in the 3-D finite-element model, including the coating layer. The model accounts for the magnetic stray field (fringing field) that causes eddy currents in the plane of the sheets, in addition to the main flux causing the classical eddy-current loss. The losses caused by the 3-D eddy-current pattern, as well as hysteresis and excess losses, are computed and measured for a test setup. A comparison of losses is made for the SMC mounted in the same setup. SMC does not suffer from eddy currents due to fringing flux. Although SMC has a 16 times higher loss than the LSSS at 1 T and 50 Hz as measured with an Epstein frame, it was shown that the iron losses in the SMC in the AFPMSM setup are only 1.5 times higher than for the LSSS.