A comparison of axial field topologies employing SMC for traction applications

This paper compares three high aspect ratio axial field topologies for traction applications employing soft magnetic composite (SMC). The paper examines the following topologies using finite element (FE) method: a torus, a yokeless and segmented armature (YASA), and a single-sided configuration. All the machines are designed to the same specification for a light electric vehicle, and the FE simulations are benchmarked against prototype motors tested in the laboratory. The topologies are compared in terms of torque density, efficiency, manufacturability, and cost, and benchmarked against a traditional laminated radial flux machine. The paper discusses several important aspects of designing axial flux machines using SMC, and shows that the YASA topology has the best overall performance due to its shorter iron circuit. The YASA machine is significantly more compact than rival designs and due to the lower material usage, is also cheaper to manufacture despite the higher cost of SMC compared to laminations.