Torque Ripple Reduction of Yokeless and Segmented Armature (YASA) Motors by Novel Asymmetric Armature

This paper presents a novel torque ripple minimization technique for yokeless and segmented armature (YASA) axial flux machines by proposing asymmetric armature. Unlike conventional stator core segment in YASA machines, the proposed asymmetric armature utilizes a U-shaped stator core, and the stator windings are wound around two axial ends of the U-shaped stator core. The effectiveness of the proposed asymmetric armature is evaluated by a comparison study with the conventional armature YASA motor on a 76-kW application. Two motors are compared in terms of winding design, torque ripple, and cogging torque with the help of finite element analysis. The results showed that the proposed asymmetric armature can reduce torque ripple at rated operation and cogging torque by 87% and 45%, respectively, when compared with the conventional YASA motor armature.