SAE EPR2021012

Electric vehicle (EV) transmission technology--crucial for battery electric vehicles (BEVs) and hybrid electric vehicles (HEVs)--is developing quickly and customers want good performance at a low cost. Single-speed gearboxes are popular in electric drive systems due to their simple and cost-effective configuration. However, multispeed gearboxes are being taken to market due to their higher low-speed torque, dynamic performance, and energy efficiency.

Unsettled Technology Areas in Electric Propulsion Systems reviews the economic drivers, existing techniques, and current challenges of EV transmission technology--including torque interruption during shifting; thermal and sealing issues; and noise, vibration, and harshness (NVH). This report discusses the pros and cons for both single-speed and multispeed gearboxes with numerical analysis.