Multi-objective Design Optimization of a Blended Permanent Magnet Assisted Synchronous Reluctance Machine

In this paper, the design and optimization process of a novel PM-assisted synchronous reluctance machine (PMASynRM) made of a blend of permanent magnets (Ferrite and NdFeB) will be presented. The design is targeting traction application and will be compared to a double-layer v-shaped IPM made of NdFeB magnets. The proposed design as well as the baseline design have the same stator and same thermal management approach. The main goal is to reduce rare-earth material content. The main challenges when it comes to reducing the rare-earth content are: (1) Maintaining the same rated torque as the baseline design (2) Eliminating the risk of demagnetization due to the lower coercivity of ferrites especially at low temperatures. The paper will focus on the optimization process with emphasis on evaluating the permanent demagnetization risk as well as design modifications considered to minimize/eliminate risk. The paper will also present a comprehensive comparison between the optimized design and the baseline design. It will be shown that around 40% reduction of rare-earth material can be achieved while maintaining the same average torque as the baseline design while minimizing/eliminating the demagnetization risk at the extreme low operating temperature of -20 °C. The paper includes details of the optimization process including sample results, evaluation of demagnetization risk and comparison of promising designs vs. the baseline design.