Effect of segmentation on eddy-current loss in permanent-magnets of axial-flux PM machines using a multilayer-2D — 2D coupled model

On the rotors of an axial-flux PM machine, NdFeB permanent-magnets are very often placed because of their high energy density. As the NdFeB-magnets are good electric conductive, electric currents are induced in the magnets when they are exposed to a varying magnetic field. This varying magnetic field has two causes: variation of the airgap reluctance due to the effect of stator-slots, and armature reaction due to the stator currents. As axial-flux PM machines have an inherent 3D-geometry, full 3D-finite element modeling seems necessary to calculate the eddy currents in the permanent-magnets and to evaluate their corresponding losses. In this paper, however, the 1D airgap magnetic fields of multiple multilayer 2D finite element simulations are combined to a 2D airgap magnetic field using static simulations. In a subsequent step, this 2D airgap magnetic field is imposed to a 2D finite element model of the permanent-magnet to calculate the eddy currents and eddy current losses. Afterwards, the introduced multilayer-2D - 2D coupled model is used to study the effect of segmentation on the eddy-current loss in the permanent magnets of an axial-flux PM machine simulating different segmentation grades.