The width of the stator slot openings near the air gap has a large influence on the power loss in the stator core and in the permanent magnets of axial flux permanent magnet synchronous machines. On the one hand, the increase in stator slot openings results in lower power loss in the stator iron. On the other hand, it also results in increased loss in the permanent magnets. Also the torque is reduced for large but also for very small slot openings. This paper deals with axial flux machines of the YASA type: yokeless and segmented armature. It is shown that the slot openings contribute to an unequal flux density level over the different laminations in the stator core. The effect on the power loss and the flux distribution is shown
