Speaker
Description
Fully turbo-electric propulsion systems for e-aircrafts need fully superconducting generators and motors with lightweight, compactness and high efficiency. High stability and reliability are also required for safety. That forces us to utilize HTS tapes which can operate in liquid nitrogen. The most important issue to realize them is the AC loss reduction of the armature windings. In our previous study, it was demonstrated that the AC loss of superconducting transformers with REBCO tapes was reduced by scribing the tapes into a multifilamentary structure. In this study, it was first verified that this AC loss reduction technique was applicable to the armature windings of rotating machines. Branch current of each filament was observed with Rogowski coils and the uniform current distribution among the filaments was confirmed. It suggests that no coupling current among the filaments was induced and then the produced AC loss is only hysteresis loss inside the filaments. Next the conceptual design of various kinds of fully superconducting 10 MW generators and 2 MW motors were carried out with magnetic field at the gap, rotaing speed and so on as a parameter by taking into account of the Ic-B-T characteristics of REBCO superconducting tapes. The armature winding was cooled with subcooled LN2 at 65 to 70 K. The superconducting rotor was cooled by He gas which was enclosed in the casing and cooled through the inner wall of the armature vessel. The electromagnetic properties of the generators and motors were investigated and compared with each other by making a numerical simulation by using JMAG. By using the calculated magnetic field distribution and the observed AC losses of short sample tapes, the AC losses in the armature and also field windings were evaluated. In addition, a small test fully superconducting motot was fabricated and tested. We will report the details.
