Design of a cost-effective hybrid-magnet multi-flux barrier IPM motor for rare-earth usage reduction in electric vehicles

This paper introduces a cost-effective hybrid-magnet multi-flux barrier interior permanent magnet motor for electric vehicle applications. The design combines partial ferrite PM substitution with a multi-flux barrier rotor to compensate for the magnetic flux reduction that occurs when reducing rare-earth permanent magnet (REPM) usage, while keeping the total magnet volume unchanged. Rotor design variables are optimized using a multi-objective genetic algorithm with sensitivity-based constraints. Compared with the benchmark design, the optimized motor maintains back-electromotive force and electromagnetic torque levels, with a slight reduction in torque ripple. An approximately 11% reduction in REPM usage, together with a 7.14% reduction in total material cost, yields a corresponding 7.43% improvement in torque per cost performance, reflecting the cost advantage enabled by the hybrid-magnet multi-flux barrier configuration. Furthermore, efficiency map evaluation shows that the proposed motor sustains efficiency comparable to the benchmark. Mechanical stress analysis confirms that rotor stress remains below the elastic limit, and demagnetization analysis verifies the magnetic robustness of both REPM and ferrite PM segments. The findings highlight the feasibility of combining hybrid-magnet and multi-flux barrier configurations for further advancements in cost-effective IPM motors.