Novel Hybrid Magnet Asymmetric Rotors for Electric Vehicles

This paper proposes two novel hybrid magnet rotor topologies, spoke-V and spoke-delta, for interior permanent magnet synchronous machines (IPMSMs) for reducing rare-earth magnet usage while maintaining high electromagnetic performance in electric vehicles. Using the Tesla Model 3 IPMSM as a reference, the models are parametrized and multi-objective optimization is performed. The proposed spoke-V and spoke-delta configurations achieve NdFeB volume reductions of 19.4% and 25.8%, respectively, while matching the torque performance of the reference machine. This results in a 20.5% and 35.1% improvement in torque per unit volume of rare-earth material. Detailed electromagnetic analyses are conducted under open-circuit, peak-load, and torque-speed characteristic analysis under full operating conditions, demonstrating the feasibility of the proposed topologies for high-speed electric vehicle applications. A small-scale prototype is manufactured and tested to verify the accuracy of the calculations. These findings highlight the potential of asymmetric hybrid magnet rotor designs to deliver less rare-earth and high-performance IPMSMs, contributing to the development of more sustainable and cost-effective electric drive solutions.