Safety Torque Generation in HTS Propulsion Motor for General Aviation Aircraft

As part of the development of all-electrical transportation systems, superconducting technology is strongly considered in propulsion systems as it enables implementation of very compact and efficient motors. However, superconductors bring a new type of possible failure mode, as they have to operate at cryogenic temperature and be stable against quench. While a failure of the cooling system or a quench may not be a critical issue in many ground-based applications, it could be fatal in airborne applications. We designed a high temperature superconducting motor to drive a general aviation aircraft and developed an auxiliary torque generation system ensuring thirty percent of the nominal torque needed for safe landing in case of quench or failure of the cooling system. The motor uses magnetized bulk superconducting plates and field coils to generate excitation field and provides 150 kW at 2700 RPM to drive a propeller. Safety torque is generated either from the electromagnetic shield or permanent magnets located in the inductor. The armature design has also been modified in order to accommodate the current increase needed to generate the required safety torque. This paper describes the design modifications done to the HTS motor in order to generate safety torque based on the minimum power needed for the aircraft to land safely.