Design Study of Double-Sided Axial-Flux Magnetically-Geared Motors for Electric Aircraft Applications

Electric aircraft require advances in electric drivetrain efficiency, specific power, and reliability. In terms of mass and efficiency, mechanically-geared electric drivetrains will significantly outperform a direct drive configuration in most applications. NASA is exploring magnetically-geared drivetrains as a potential way to achieve mass and efficiency benefits over direct drive systems without the maintenance and reliability penalties of mechanical gears. In this paper, one possible topology of magnetically-geared motor, the double-sided axial-flux magnetically-geared motor (DSAMGM), is studied to quantify its achievable performance. A design tool is presented that uses a genetic algorithm to optimizes the DSAMGM’s efficiency and specific torque based on electromagnetic, thermal, and mechanical calculations and simulations. To verify the tool, one example output design is refined to a preliminary design level using an independent set of high fidelity finite element simulations. The high fidelity electromagnetic, thermal, and structural results are used to verify or revise the design tool’s assumptions and margins. The refined design tool is then exercised to explore the performance limits of 25 kW to 200 kW DSAMGMs. The results suggest that the topology can achieve greater than 20 Nm/kg specific torque and 97% efficiency at a 100 kW output power.