On the Use of Magnetic Wedges in Axial Flux Permanent Magnet Machines

Axial flux permanent magnet (AFPM) machines are being increasingly used in a variety of industrial direct drive applications which benefit from their extreme axial compactness. In particular, slotted AFPM machines are of great interest since they allow to achieve high torque densities together with an acceptable constant power speed range. This paper analyzes a particular aspect related to the design of such machines, i.e., the use of soft-magnetic-composite wedges to close stator slots. This paper is the continuation of a previous investigation dedicated to the analysis of the no-load performance variation introduced by the magnetic wedges. Here, the attention is focused on the load performance by studying the effect of the wedges on d-q-axis stator flux linkages, torque production, and losses. The 2-D and 3-D finite element analyses are performed on a 10-kW AFPM machine, various magnetic wedge configurations are studied, and the load performance is compared with that of the same machine using nonmagnetic wedges, in terms of stator flux linkage, average and ripple torque, and magnetic losses. Finally, experimental tests and results on a full scale prototype machine mounting magnetic wedges are reported.