A New Yokeless Stator Structure With Low Loss and High Mechanical Strength for AFPM Motor: Design, Analysis and Experimental Verification

In terms of the yokeless and segmented armature (YASA) axial flux permanent magnet (AFPM) motor, it is always a challenge to secure the strength and stiffness of sandwiched stator while considering low loss and high stiffness, as well as excellent cooling ability. In this article, a new yokeless stator structure with low loss and high mechanical strength is presented for YASA AFPM motor. First, the stator is made of coiled silicon steel with negligible stiffener yoke. In order to overcome the unbalanced axial electromagnetic force, the stator assembly is fixed and installed by means of fixing pin with the aluminum cabinet. Then, the additional loss of stator fixed structural components is analyzed and suppressed with the half of material selection and insulation treatment. Furthermore, the fixed structural strength of stator is analyzed by the mechanical finite element analysis (FEA) to determine an effective scheme of fixing pins. Finally, the proposed yokeless stator structure is developed and manufactured. The deformation of the assembled stator is tested as the axial force variation. Combing the FEA results of electromagnetic force and the loss test results of the final prototype, it can be concluded that the new yokeless stator structure absolutely meets the strength requirement and maintain low loss feature. This article provides a low manufacturing-cost, high performance and high reliability stator solution for YASA AFPM motor.