Sustainability optimization of the NdFeB magnet system of PMSMs by linking electromagnetic calculation and life cycle assessment

Abstract:
In electromobility the environmental impact gains relevance. Unlike energy consumption during use, resource use and greenhouse gas emissions in production are not comprehensively considered in the present technical development. Due to the high impact on climate change of heavy rare earths in permanent magnets, a novel method for optimizing the rotor of permanent magnet synchronous machines (PMSM) in terms of production emissions and performance is investigated. A dynamically adjustable life cycle assessment (LCA) model is linked to the electromagnetic calculation and determines the production emissions depending on the design. The LCA model accounts particularly for the impact of the chemical composition of various NdFeB magnet grades. Based on an existing PMSM, a multi-objective optimization of the magnet system is performed using data-driven surrogate models, to investigate the conflict between production emissions and the maximum operating temperature of the magnet. By means of the optimization result three design rules are proposed for more sustainable magnet systems: The reduction of maximum operating temperature of the magnets, the avoidance of magnets with high energy products and the increase of magnet mass at high intrinsic coercivity to maintain a low heavy rare earth content.