Comparative Analysis of Motors with Inner and Outer Reluctance Rotors and PM Stators

This paper presents a comparison of special outer and inner reluctance rotor motor topologies with permanent magnet (PM) stators having toroidal AC windings. A systematic approach is taken to study and discuss the design geometries, the respective impact on performance, and adoption of technological advancements such as stator-only cooling and hair-pin winding for high slot fill factor. Parametric FEA models are developed for both topologies, and design of experiments (DoE)-based sensitivity analysis is used to study the effect of independent variables on specific performance metrics such as torque, motor loss, torque ripple, and power factor. Inner and outer rotor topologies are compared using the resulting Pareto fronts from multi-objective optimization. Optimized outer rotor designs using both non-rare earth PMs and ferrites are also investigated over selected drive cycles. The efficiency per cycle is evaluated at seven of the most representative points of the drive cycle obtained using a k-means clustering algorithm for the world harmonized light vehicle test procedure (WLTP), Orange County, and parcel truck (Baltimore) drive cycles.