Addressing the Challenges of Lightweight Aircraft Electric Propulsion through Electrical Machines with Air-gap Windings

The development of power dense electrical drives for aircraft propulsion is likely to require radical changes to the way electrical machines are manufactured. The flux carrying limitations and weight of soft magnetic materials are becoming a major barrier to further improvements in power density. The replacement of conventional toothed stator designs with air-gap winding topologies have been shown to have weight advantages. However, the implementation of an air-gap winding imposes new design challenges and requirements. The paper reviews these requirements and proposes a novel multi-functional material solution based on a glass reinforced aluminum conductor composite. Using electrical and thermal properties measured from a sample of this new winding layer material the weight saving potential is assessed against an existing aircraft electric propulsion motor developed for a rotorcraft application. The findings suggest that it may be possible to reduce the weight of the stator active components by as much as 60%, although these benefits are partly offset by an increase in the weight of the permanent magnet rotor.