A Novel Stator Tooth Shape of Axial Flux Permanent Magnet Motors Based on Soft Magnetic Composite for Torque Density Enhancement

This paper proposes a pyriform stator tooth body shape of axial flux permanent magnet motors (AFPMMs) based on soft magnetic composite (SMC) to enhance torque density. For the AFPMM with the conventional trapezoidal and proposed pyriform tooth body designs, the difference only lies in tooth body shape and slot area. Under the same tooth cross-sectional area and other motor geometric parameters, the proposed pyriform tooth body shape minimizes the coil length of the concentrated winding compared to the traditional tooth body shape. The electromagnetic performance of the 10-poles and 12-slots AFPMM with the conventional and proposed tooth body shapes is compared under the same copper loss by using 3-D finite element analysis (FEA). Compared to the traditional design, the investigated AFPMM with the proposed pyriform tooth body shape has a 10.02% lower phase resistance and, thus, a 5.54% higher torque density. Besides, the influence of geometric ratios and pole-slot combinations on the electromagnetic performance of the AFPMM with the proposed pyriform tooth body is investigated. It shows that the AFPMM has a significant increase in torque density by replacing the conventional design with the proposed pyriform stator tooth body. Adopting the proposed pyriform tooth body shape is a simple and viable method for higher torque density of the AFPMM under certain constraints. Finally, a prototype with traditional trapezoidal teeth was manufactured using the wire-cutting process to verify the effectiveness of FEA. The impact of wire-cutting processing on the motor performance can be equivalent to incorporating an eddy current layer into the finite element model.