Design of a cost effective IPM machine minimizing the use of rare earth magnets

Many industries, including the automotive one, heavily rely on the use of rare earth materials for their applications. In particular, elements such as neodymium and dysprosium are used for realizing motors with high efficiency and torque density. However, although these materials are abundant, their extraction process has a non negligible impact on the environment. Moreover, the majority of their manufacturing is controlled by a few countries, influencing the stability of the supply chain. Hence, in this thesis, which was carried out with the collaboration of Volvo Cars Corporation in Sweden, a hybrid permanent magnet synchronous motor design is proposed. The solution combines the advantages of a new rare-earth-free iron nitride permanent magnet with standard NdFeB ones. Particular attention is given to prevent the total irreversible demagnetization of the magnets while reaching the required performance. Different tools were used, including the open-source software SyR-e for estimating the peak transient short circuit, the JMAG Designer for the optimization, and Ansys Maxwell for the performance evaluation. The aim was to design a motor which achieves the performance requirement even after an active short circuit. This was done by not only minimizing the cost and environmental impact of the permanent magnet, but also by reducing the average losses in the WLTC. Finally, the design was compared to the benchmark motor that only uses rare earth magnets, highlighting the differences between the two and the advantages and disadvantages of the design.