Retractable Modular Machines - Driving Aerospace Electrification Revolution

The civil aviation sector has been one of the fastest growing sources of carbon emissions as ever-growing numbers of people travel by plane.

Therefore, accelerating aerospace electrification is timely and pivotal for reducing the carbon footprint and meeting government's CO2 emission target by 2050. As one of the key components in aircraft propulsion systems, electrical machines have long been the centre of research.

Permanent magnet (PM) machines can achieve high efficiency (>96%) and excellent specific power density (>13kW/kg), are therefore very suitable for aerospace applications. However, due to the use of rare earth PMs, the machine's fault tolerant capability could be undermined.

This is particularly the case for inter-turn short-circuit faults, which are the most difficult to detect, and the amplitude of the associated short-circuit current can be many times larger than the rated current.

Such a large inter-turn short-circuit current, if left unattended, could lead to winding overheating and increase the risk of fire which can compromise the safety of the aircraft.

We aim to develop a novel class of modular permanent magnet (PM) machines with retractable stator segments that can significantly reduce the short-circuit current and hence can improve their suitability for aerospace application. The retractability of the stator segments is achieved through completely passive means, and hence avoiding complexity.

Such a system will be compact, robust, and more importantly acts automatically when a short-circuit fault (one of the most severe faults in electrical machines) occurs in a stator coil.