A Study on the Efficiency Matching of Energy-Weighted Regions in IPMSM Through Loading Ratio and Stator-Rotor Diameter Ratio Adjustment

This study proposes an electromagnetic design strategy to improve the energy efficiency of electric-vehicle (EV) traction motors by defining an operating region with high energy contribution using Urban Dynamometer Driving Schedule (UDDS) data and targeting efficiency improvement within that region. For distributed-winding (DW) and concentrated-winding (CW) IPMSM models, the stator-to-rotor diameter ratio varied, and the resulting change in the loading ratio was used as an indicator to evaluate loss and efficiency variations in the energy-weighted region of the efficiency map via two-dimensional finite element analysis (2D FEA). The results show that the losses within the weighted region decreased by up to 16.64% compared with the reference model, and the UDDS-cycle-based overall energy efficiency improved by up to 0.423%. These findings demonstrate that combining electromagnetic geometric design with driving-cycle data can serve as a practical metric for improving EV energy efficiency.