Optimization, Evaluation and Comparison of Stator Topologies for Magnetically Levitated Fractional-Horsepower High-Speed PMSMs

High-speed electric drives are increasingly utilized in applications such as turbochargers, mechanical transmitters, and printed-circuit-board (PCB) drills due to their compactness and efficiency. This study focuses on the optimization and experimental validation of four different stator topologies for high-speed motors operating at speeds up to 200,000 rpm with a two-pole permanent magnet rotor. A multi-objective optimization process, based on finite element (FE) simulations and a genetic algorithm (NSGA-II), was conducted to minimize copper and iron losses, end winding length, material costs, and passive radial stiffness while maximizing efficiency. The optimized designs were subsequently validated through prototype construction and testing. The investigated stator topologies include slot-less designs with distributed and toroidal windings, as well as slotted designs with toroidal and concentric windings. Magnetic bearings are employed to reduce friction and extend service life, while constraints such as mechanical air gap and outer stator diameter are kept constant across all designs. The study also consider the influence of rotor magnet strength and material properties on efficiency and costs. Experimental validation involved run-down tests in a vacuum chamber to isolate stator iron losses from air friction and other losses. The results demonstrate good agreement between simulations and measurements. The findings provide valuable insights into trade-offs between efficiency, cost, and performance in high-speed motor design, offering practical guidelines for selecting suitable stator topologies for specific applications.