Distributed electric propulsion aircraft have been proposed by leading players in the aviation industry as a disruptive technology to address the environmental impact of air travel. Electric propulsion offers flexibility to distribute the electric power within the aircraft and better integration of distributed propulsion with airframe, leading to significant fuel saving, emission and noise reduction. The NASA N3-X concept aircraft for example has great potential to deliver 70% fuel saving relative to 2000 baseline. Superconducting fault current limiters (SFCLs) are critically required to achieve reliability and safety of the distributed electric propulsion power system under different fault conditions. Resistive superconducting fault current limiter (SFCL) is the simplest and most compact design making use of the intrinsic superconductor material behaviour of quenching at high current levels and transitioning from negligible resistance to a high resistance to limit the fault current.
Previous and ongoing SFCL research have been undertaken mainly for land-based power system. Resistive SFCLs have been successfully developed and demonstrated reliable operation in AC live-grids. Straight samples and small coils of 2G HTS conductors have been investigated for DC application. However, up to now there is no SFCL specially designed for aeroplane application. Compared with the land-based power system, the key challenges to design SFCL for aeroplane application is efficiency improvement and weight reduction in order to deliver minimum weight penalty. Therefore, there is a timely requirement to develop high efficiency and lightweight AC and DC SFCLs using both numerical and experimental methods to enable future development of large-scale electric propulsion aircraft.
This project will meet this requirement by delivering 1) an AC SFCL with minimised AC losses, and 2) a DC SFCL with minimised HTS materials required. This will be achieved by determining the optimum combination of novel winding strategy and candidate HTS lamination material. Firstly, we will develop a new multi-physics finite element model coupling analysis of electromagnetic and thermal behaviour of the 2G HTS SFCL coil. The combination of novel winding strategies and HTS lamination materials which deliver optimum AC and DC SFCL coils will be investigated using the finite element model. Secondly, we will construct and characterise representative small helical coil for the AC SFCL. A 1 kA demonstration AC SFCL coil will also be built using the optimum combination identified and characterised in a wide range of operation temperature between 50 K and 77 K. Thirdly, we will construct and characterise a 1 kA DC SFCL demonstration coil and determine the optimum operating temperature in terms of minimum overall system weight. And finally, we will validate the multi-physics SFCL model and examine fundamental physics limitation based on the experimental results. We will also determine the pathway to scale up laboratory demonstrators to industry prototype. This will provide a vital step towards the realisation of high efficiency and lightweight SFCLs for aeroplane application. This work will be carried out in close collaboration with Airbus and Oxford Instruments, and will provide specific recommendations to scale up laboratory demonstrators to industry prototype.