Overview and Evaluation of Electric Machines for Electric Regional Aircraft Propulsion Systems

Kurzfassung

Limiting the impact of global climate change can be achieved by reducing CO2 emissions, as set out in the Paris Agreement and the European Commission's Flightpath 2050 publication. Air transport plays an important role in this, even emphasized through the increase in traffic volume [1]. The architecture of the powertrain in current aviation has to be rethought and further developed. Electrified propulsion systems could serve as a solution. These require electric motors, which have already proven their effectiveness as drive units in other sectors, such as the automotive, marine and railway industries, due to their efficiency and performance maps. As the development stages of the individual motor types are at different stages and they have generally not yet been used as a drive unit in a commercial aircraft, it is essential to identify potentially suitable topologies to focus research and further development on these. Previous studies have already shown a tendency towards the selection of a motor topology [2–5], whereby the weighting of the individual criteria has been neglected. The importance of this weighting is emphasized in Sadraey [6], which is why special attention is paid to it in the following publication. This paper identifies potential engine topologies as drive units for the propulsor of regional aircraft using an evaluation method with weighted criteria from aviation-specific requirements. Firstly, the state of the art of the considered engine topologies, their potentials and challenges are presented. The evaluation method and the identified requirements for electric machines in aviation as well as the evaluation and exclusion criteria derived from them are introduced. The exclusion criteria are used for a pre-selection of machine types and the remaining types are then evaluated in detail. Concluding, the most suitable topologies are identified. The core results of the investigation highlight that, in addition to reducing weight and thus increasing the power density of motors, the reliability and the safety of the system play decisive roles. Initial analyses highlight the great potential of permanently excited machines due to their high-power density. Nevertheless, there is a risk of demagnetization in the event of a short circuit and a strong dependency on procurement. The paper evaluates alternatives in this regard, such as the reluctance machine, as well as new concepts such as the superconducting machine. Examples of investigated machines are shown in FIG 1. The investigations also emphasize that the fundamental question regarding the necessity of a gearbox still exists and that further considerations are required.