This paper describes the comparison of electromagnetic characteristics of two different superconducting-motor structures for electrified aircraft propulsion systems. Future electrified aircraft demand higher output (over 16 kW/kg) and higher efficiency (> 98%) for their motors in comparison with current ones. To satisfy the demands, two kinds of superconducting motors are dealt in this study: one is partially superconducting motors (PSCMs), made of superconducting field coils and copper armature windings; the other is the fully superconducting motors (FSCMs) made of superconducting field/armature windings. They are cooled at 20 K with liquid hydrogen. We designed these two motors with finite element method to obtain the output density of 16-20 kW/kg for future electrified propulsion systems. We selected 3.0- and 5.0 MW superconducting motors, considering the application to aircraft for almost 180 passengers and 44 MW rated power for take-off. Also, we evaluated the motor weight using two kinds of cryostat materials: stainless steel (SUS) and fiber-reinforced plastic (FRP). The results show that the 5.0 MW PSCM using FRP achieved the output density of 16.9 kW/kg and the FSCMs with FRP of 23.5 kW/kg, respectively. The values of their output density are over three times higher than those of synchronous motors using permanent magnets, whose maximum output density value is 5 kW/kg, so far. We also evaluated the motor losses and efficiency; their results described that the efficiency of the PSCM achieved around 98%, while the 5.0 MW FSCM over 99%. The obtained data shows the superconducting motors are one of the key solutions to realize future electrified aircraft propulsion systems.
