Fully turboelectric propulsion systems with lightweight and high power density are one of the solutions to realize future electric aircrafts. Our research group started to develop 10 MW fully superconducting synchronous generators and 2 MW motors. In this system, we designed so that the generators supply electric power at the voltage of 6.9 kV, however, the motors operate at the low voltage of a few kV. Therefore, a 6.9 kV-10 MVA step-down transformers with lightweight are required for this system. In our previous studies, a 66/6.9 kV-20 MVA superconducting transformer with REBCO superconducting tapes was developed. The low AC loss was realized by using multifilamentary REBCO tapes which were made by laser-scribing technique and parallel conductors in which REBCO tapes were stacked and transposed. The target of this study is to realize superconducting transformers with a power density over 20 kW/kg. Firstly, the structure of the superconducting transformer was assumed as an inner iron double concentric windings type. When one-turn voltage is 23 V/turn, the three-phase superconducting transformer becomes the most lightweight design of around 200 kg. Next, the optimum transposition patterns for parallel conductors which were applied to the windings were investigated to realize uniform current distribution among the tapes and low AC loss. The AC loss was calculated by using JMAG (electric instrument analysis software of JSOL). The detailed properties and design specifications of superconducting transformers will be reported in this conference.
This research was partially supported by the New Energy and Industrial
Technology Development Organization (NEDO), the Japan Science and
Technology Agency (JST): Advanced Low Carbon Technology Research and
Development Program (JPMJAL1405) and the Japan Society for the Promotion
of Science (JSPS): Grant-in-Aid-for Scientific Research (JP18H03783 and