Design of Rare-Earth-Free PM-assisted Synchronous Reluctance Machine for Heavy-duty Automotive Application

Electrical machines designed for automotive applications are characterised by high torque density, wide speed range and low cost. The use of NdFeB magnets in such machines can achieve the required high torque density and wide speed range, however, it fails to meet the low-cost requirements. As a result, this paper explores the capability of rare-earth-free design through a PM-assisted synchronous reluctance motor (PM-SynRel). A PM-SynRel design with NdFeB has been used in this study where the NdFeB magnets have been replaced with ferrite magnets. Following, mechanical analysis has been conducted on the rotor to ensure the stress level in the rotor does not exceed the material limit. Therefore, several mechanical methods have been studied to evaluate their mechanical capability and electromagnetic performance degradation. Thermal analysis has been conducted last to evaluate the temperatures in the different machine parts to avoid exceeding the required limits. Detailed numerical thermal analyses were also performed to assess the thermal behaviour of the design developed. Finally, a prototype has been made and tested to validate the simulation results.