Outer Stator Magnetically-Geared Motors for Electrified Urban Air Mobility Vehicles

Electrified urban air mobility vehicles require advances in the specific power, efficiency, and reliability of electric motor drivetrains. Gearing an electrified aircraft’s drivetrain generally leads to a lighter weight and/or more efficient drivetrain overall. Mechanical gears, however, due to their use of mechanical contact to transmit torque between gear bodies, have numerous wear and failure modes that lead to significant reliability and maintenance penalties. Magnetic gears, on the other hand, use magnetic fields instead of mechanical contact to transmit torque between gear bodies, and therefore have the potential to achieve the benefits of a geared drive system without reliability and maintenance penalties. Magnetic gears cannot match the specific torque of mechanical gears. Therefore simply trading a mechanical gear for a magnetic gear in a drive train will add mass. To make a magnetically-geared drive competitive with a mechanically geared drive in terms of mass, the magnetic gear and the electric motor in the drive train have to be integrated to share magnetic and mechanical components. One way of integrating a magnetic gear and a motor is called an outer stator magnetically-geared motor. In this paper, the outer stator magnetically-geared motor is assessed for its potential in urban air mobility vehicles. A design tool for outer stator magnetically-geared motors is developed. The tool is used to create a preliminary design of a 100 kW outer stator magnetically-geared motor. High fidelity analysis of that design is used to finalize it and update the design tool. Additional design tool results are produced to estimate the potential of the outer stator magnetically-geared motor for a 100 kW urban air mobility drive.