Multilayer concentrated windings for axial flux PM machines

Abstract

Coreless axial flux machines with airgap concentrated windings are of interest due to their high torque density. One of the main challenges with such a winding is that the torque producing MMF component that corresponds to the fundamental of the permanent magnet excitation is accompanied by harmonics. At least one of them is of substantial amplitude. The other harmonics are asynchronous and cause losses in the rotor core and magnets. The lower order harmonics, due to their higher magnitude, are of especial harm. This paper proposes a new multilayer winding arrangement to reduce the non torque producing MMF harmonics. This winding is applied to a 12 coil 16 pole coreless axial flux machine. The efficacy of the winding is established by 3D finite element analysis.