Impact of Rotor Losses in a 12-Slot 10-Pole Axial Flux PM Machine

In spite of their several advantages, the fractional-slot PM machines suffer high contents of space harmonics in the air-gap MMF distribution. The MMF space harmonic amplitude and frequency depend on the particular combination of number of slots and poles. The main consequence of such harmonic contents is the induced losses in the rotor. Moreover the slot opening can produce considerable rotor losses due the variation of permeance corresponding to the stator slots. This paper presents the impact of the rotor losses on the performance of a 12-slot 10-pole axial flux PM machine. The influence of both MMF harmonics and slot harmonics is considered. Comparisons between prediction and experimental results are included in the paper.