Comparative Study of Yokeless and Segmented Armature Machines With Different Stator Cores for Electric Vehicle In-Wheel Applications

The yokeless and segmented armature (YASA) machine's compact structure, high efficiency, and high torque density make it an ideal choice for electric vehicle in-wheel applications. The stator cores of YASA machines are available in different materials and geometries. This paper presents a comparative study of YASA machines with different stator cores to determine their advantages and disadvantages for electric vehicle in-wheel applications. First, YASA machines with radial lamination silicon steel (RLSS) stator cores and soft magnetic composite (SMC) stator cores are introduced. A new combined lamination silicon steel (CLSS) stator core, consisting of two tangential laminated shoes and a radial laminated bar, is also proposed. The main parameters of YASA machines with different stator cores for electric vehicle in-wheel applications are listed. Then, the electromagnetic performance, including efficiency, torque density, flux weakening capability, and torque/power characteristics, are comprehensively compared based on 3D finite element analysis (FEA). Finally, the guideline for the stator core selection of YASA machines for electric vehicle in-wheel applications is given.