Design of Electric Machine for Electric Aircraft: A Case Study of Rotor-stator Configurations and Magnet Arrangements

Recent research on aircraft propulsion systems has looked at saving fuel and reducing carbon emissions. In particular, for electric machines used in electric aircraft, high specific density, efficiency, and power factor are needed. We studied suitable rotor-stator configurations and magnet arrangements for a 250 kW electric machine to be used in small electric aircraft by focusing on specific density. We determined that a double rotor electric machine with a polar anisotropic magnet can improve power factor by 14% as compared with a conventional inner rotor, and it can also achieve a higher efficiency and power factor. In addition, we demonstrated a novel high-efficiency heat transfer method suitable for a double rotor electric machine, designed a 5.0 kW/kg electric machine, and manufactured a prototype double rotor motor to assess the possibility of retaining teeth.