Design of High-Efficiency Ultra-High-Speed Motor for Fuel-cell Air Compressor Using an Amorphous Stator with Multiphase Winding

This paper proposes the design of a high-efficiency ultra-high-speed motor (UHSM) for fuel-cell air compressor applications. The UHSM experiences an exponential increase in stator core loss and rotor eddy current loss as the operating frequency increases. These high-frequency losses drastically reduce motor efficiency and affect thermal integrity. To overcome this critical problem, a new amorphous stator with multiphase winding is developed in this study for high-power UHSM. First, an ultra-low loss amorphous metal is used for the stator to reduce the high-frequency core loss. Since the amorphous metal is harder to process into conventional stator geometry, the proposed stator has a separated hollow-cylinder yoke and a fully opened rectangular stator tooth. Second, a multiphase stator winding configuration is adopted to decrease the magnet eddy current loss by reducing the airgap MMF harmonics. To verify the effectiveness of the proposed stator, a 15 kW 110,000 rpm UHSM is designed using Multiphysics finite element analysis (FEA). The electromagnetic performances are evaluated extensively and compared with the benchmark design. It is observed that the proposed stator increases UHSM efficiency by around 3.2%. In addition, the multiphase winding decreases the torque ripple of the proposed motor by 22.2% and enables the fault-tolerant capability. The proposed motor can be used in UHSM where portability and reliability are critical, for example, fuel-cell system, electric turbo-compressor system, micro gas-turbine.