Influence of Stator Topologies on Average Torque and Torque Ripple of Fractional-Slot SPM Machines with Fully Closed Slots

摘要

This paper investigates the influence of concentrated\udwinding configurations and stator core structures on torque\udperformance of fractional-slot surface-mounted PM (SPM)\udmachines. From analyzing the separated torque components of\udprototype SPM machines with 12-slots/10-poles (12S/10P)\udcombination by frozen permeability (FP) method, it can be found\udthat the torque ripple is closely related with local saturation in\udfully closed slot (FCS) machines. Besides, the heavier local\udsaturation will also jeopardize the merit of using alternate teeth\udwound windings, such as obtaining higher average torque than\udelectrical machines with all teeth wound windings. The further\udanalysis of stator tooth relative permeability variation over one\udelectrical period demonstrates that the major reason for torque\udripple difference among these electrical machines with different\udstator topologies is the asymmetric saturation between the\udadjacent teeth. Both the subharmonic due to armature reaction\ud(determined by winding connection and current value) and the\udasymmetry of stator core structure contribute to such asymmetric\udsaturation. In order to more clearly verify this, the\udcomplementary slot/pole number combination (12S/14P) is also\udanalyzed. The conclusion is effective for electrical machines with\udother slot/pole number combinations as well. Experiments have\udbeen carried out to validate the predictions.