Influence of Insulation Requirement on PMSM Design and Performance Driven by a Multi-Level Inverter

Permanent magnet synchronous machines (PMSMs) offer high efficiency, power density, and controllability, making them attractive for electric vehicle (EV) propulsion application. However, insulation paper thickness and copper winding insulation thickness occupy valuable real estate within the slots of the stator and limit the slot fill factor. This limitation negatively impacts the machine's performance and cost enhancement. Insulation thickness requirement is significantly influenced by the type of excitation, temperature rating and DC bus voltage. Keeping the DC bus voltage and temperature rating constant, this paper discusses findings that provide machine designers and researchers with valuable insights to optimize PMSM designs with lower insulation thickness requirements driven by multilevel inverter excitation. High speed traction motor designed for EV propulsion is used as a baseline motor. Finite element simulations are carried out to optimize the baseline motor design with reduced insulation thickness in the stator. It was found that reduced insulation thickness can be used to obtain benefits such as improved heat transfer, reduced use of rare-earth permanent magnets, reduced cost, high specific torque and power density.