Optimum Rotor Design for Rare-Earth Free High Performance Traction Applications Interior Permanent Magnet Motors Enabled by Iron Nitride Permanent Magnet

Interior Permanent Magnet (IPM) motors are widely employed for traction applications such as electric vehicles due to the increased torque/power density, efficiency, and more rigid rotor retention. These advantages are enabled by rare-earth PMs that contain Dysprosium (Dy) (heavy rare-earth) and Neodymium (Nd) (light rare-earth) elements. While this has posed several challenges in terms of sustainable supply and prices volatility, research efforts have been focused on developing rare-earth free IPM motor designs to mitigate the use of heavy rare-earth elements. In this paper, the use of a novel PM rare-earth free material in different rotor topologies will be investigated. Several rare-earth free designs equipped with Iron Nitride (FeN) and FeN blended with high performance Ferrite PM will be presented, analyzed, and optimized to demonstrate the design performance and optimum rotor geometry. The optimization criteria is dependent on surviving permanent demagnetization under demanding temperatures and operating conditions, as well as delivering similar torque-speed profile in comparison to Chevrolet Bolt motor that uses Dy-NdFeB which is used as the baseline design. Moreover, detailed analysis of demagnetization under different temperatures, efficiency maps, and rotor stress mechanical analysis are provided.