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.