Propulsion System Design Considerations for HEV versus EV Applications

The design and development of EVs and HEVs has become a growing issue recently due to concerns about pollution and dependence on non-renewable fossil fuels. Accordingly, General Motors (GM) has an evolving vehicle electrification plan over the past several decades and into the future to deliver low-cost and efficient EVs and HEVs. Propulsion system requirements for the applications of EV and HEVs are quite different and therefore, the design principles and directions are also distinct between these cases. From micro-hybrid and full plug-in hybrid applications to full EV applications, design requirements, strategies and outcomes can widely vary. Continuous and peak duty are substantially different depending on the application of the vehicle. Motor operational duty is significantly higher for EV compared to the electric motor of a hybrid electric vehicle. Motor torque, power and efficiency requirements are also higher for EV motors, which greatly influences the choice of motor type and its thermal and electromagnetic design. Issues like NVH and thermal can be less significant in designing motors for HEV because of engine masking and lower duty cycle of operation. Motor design requirements, optimization process and results for two different motors intended to be used in EV versus HEV applications are discussed in this paper. Moreover, traction inverter requirements differ significantly across electric vehicles and various hybrid architectures. Each configuration presents distinct challenges, ranging from packaging and thermal management to vibration and electrical constraints. Despite these differences, the design and requirements are harmonized to reduce complexity and ensure seamless performance. This paper outlines the design strategies employed to achieve these objectives.