A Novel Concentric Winding Axial-Flux Permanent Magnet Machine with High Winding Factor

Axial-flux permanent magnet (AFPM) machines are welcomed widely in many applications thanks to the high torque density and compactness. In the AFPM machine, the concentrated winding and distributed winding have different characteristics. In order to increase the winding factor and reduce the winding ends, a novel concentric winding AFPM machine is proposed in the paper. The stator of the proposed machine is divided into three circles from the inner side to the outer side. Then, the three-phase windings are arranged on the three circles, respectively. The phase angle difference is achieved through the mechanical offset between the teeth of three circles. Thus, the winding factor can be kept as 1 with a few winding ends by adjusting the pole-slot combination. In addition, the staggered teeth between the three circles can also reduce the cogging torque. In the optimization, the back EMFs of the three phases are nearly balanced. 3D finite element analysis also shows that the machine has a strong overload capability.