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This paper presents some results of the investigations carries out in the frame of the IMOTHEP project (Investigation and Maturation of Technologies for Hybrid Electric Propulsion). This European project aims to study the potential of hybrid and electric propulsion on different aircraft concepts, from Regional to Short Medium Range aircrafts, to reduce the fuel consumption and CO2 emissions. For each concept, two approaches are defined: a conservative (close to conventional aircraft) and a radical (to take into account disruptive options). The focus is done on the disruptive aircraft configuration illustrated below. For such concept, the range of mechanical power for the electrical propulsion unit (EPU) is in the megawatt-class and above. Alternatively, to the conventional technologies, the superconducting and cryogenic technologies seem to be a good challenger in order to provide high specific power, high power density and highly efficient electrical components. In this paper, a basic review of switches performance has been done to estimate the most suitable device. IGBT\'s were found most suitable due to their good performance at cryogenic temperature and their availability at the required rating for the inverter. Then a quick comparison has been done between different inverter topologies, where it was shown that the NPC has the best performance as it is the most efficient and most suitable for the motor application. Then, a comparison between NPC and ANPC has shown that by replacing the diodes with IGBTs, better performance can be obtained. Then, in the end, a technique for calculation of the converter losses and initial weight estimation has been done. It is possible with a fully superconducting machine to achieve a very high power density. The role of the input is not decisive, and it can therefore be easily adapted to the technical choices that will be made. Torque oscillations are low, less than 10% for all configurations. The main remaining problem is that of optimization, taking into account the losses in the superconductors and the non-active elements of the machine. The power obtained for the two machines is higher than that required, and the adjustments needed to place the non-active elements will most certainly decrease this power (not only the specific power). Furthermore, as the operating times of the engine are not yet fixed, thermal studies have not been carried out. This implies that the power ratings of the motors are oversized. The given power ratings, therefore, correspond to steady state operation. In an optimized design, a distinction is made between transient operation, even for a few minutes, and steady state operation. The next step will be to optimize the machine, considering all the thermal constraints associated with cryogenics. The next step will determine the extent of the gains we can expect |
