High Efficiency Hybrid Synchronous Motor Design With Loss and Thermal Analysis for Integrated Two-Speed e-Powertrain System in Electric Vehicles

With high efficiency and high flux-weakening capability, hybrid synchronous motor (HSM) is a competitive alternative as a cost-effective solution for traction applications. This paper presents a cascaded and systematic method to define specifications of target motor and design a high efficiency 172 kW, 18000 rpm HSM for an integrated two-speed e-Powertrain system. Vehicle-level specifications and gear ratio combinations are taken into consideration to determine motor requirements. Four concept rotor typologies are investigated to obtain efficiency maps for comparisons in simulation models. Detailed loss analyses are done at both base speed and maximum speed for a selected HSM. Steady-state and transient thermal analyses are completed to identify potential overheating and demagnetization risks. 0.2 mm stator lamination and 4 segmented magnets in each magnet slot have been applied to further improve motor maximum efficiency. Performance tests are completed in the dyne bay to show that 97.5% maximum efficiency is achieved.