Light PMSM Direct Drive for Small Electric Aircraft: Preliminary Design with Key FEM Validation

Small electric aircrafts for short range with Li-ion battery (200 Wh/kg) has been investigated aggressively lately for local transport or for pilots training. Quite a few types of permanent magnet motor drives have been proposed for the scope with speeds from 1500 to 5000 rpm, powers of 30-380 kW, with specific calculated weights of 7 to 25 Nm/kg active weight. This paper presents a preliminary design of a pilot-training small aircraft at 20 kW cruising respectively, 80 kW max. at take-off, max. speed of 2000 rpm (direct-drive) at max. 6 kW/kg for a 80 kWh (330 kg) Li-ion battery for an 864 [kg] total aircraft weight. An easy to build single bearing pancake shape interior rotor surface PMSM of 24 slots/20 poles is chosen to perform in cruising at 96 + [%] efficiency. Preliminary design is followed by Key FEM validations of no-load and on load airgap flux density, torque, torque waveform and demagnetization avoidance.