Design of an Axial-Type Magnetic Gear for the Contact-Less Recharging of a Heavy-Duty Bus Flywheel Storage System

This paper presents the electromagnetic design and performance assessment of an axial flux magnetic gear (AMG) for the contact-less energy transfer to an on-board flywheel energy storage system (FESS) to supply heavy-duty electric buses. The AMG electromagnetic configuration is designed to cope with the system torque/speed requirements according to the FESS specifications for a typical driving cycle of an urban bus. Starting from a preliminary sizing by analytical formulations, the torque performance is improved by more accurate finite element analyses based on simplified models. Different parameters also affecting the AMG size are considered to identify an optimized feasible configuration. Finally, the evaluation of the core losses for a full recharge operation enables one to choose the more convenient ferromagnetic material.