High power motors and generators with compactness and lightweight are required for turboelectric propulsion system for future electric aircrafts. Fully superconducting rotating machines have the potential to realize high power density. In this study, we aim to design high-power-density synchronous motors composed of superconducting field windings and superconducting armature windings, especially power density over 20 kW/kg. Note that, the voltage of the armature windings should be a few kV or less due to a low withstand voltage at a height of over 8000 m in the sky. The introduction of transposed parallel conductors can realize a large current capacity in the armature windings, which also lead to low voltage. Firstly MW-class fully superconducting motors were designed as follows. The superconducting wires were BaHfO3-doped EuBa2Cu3Oy coated conductors fabricated by IBAD-PLD technique. The operating temperatures were assumed as 20 or 65 K. The magnetic flux density at the air gap was assumed 1, 1.5 and 2 T. The motor properties were investigated by making a numerical simulation with JMAG. AC losses were actually observed by a pickup coil method and partially estimated by using theoretical expressions such as a temperature scaling law. For a total model of 6 patterns, the influences of the operating temperature and the magnetic flux density at the gap on the power density and the AC losses of the field and armature windings were investigated and compared. As a result, it was shown that the power density attained to 21.2 kW/kg in the case of the operating temperature of 20 K and gap flux density of 1.5 T for the 5 MW-class superconducting motor.
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 (ALCA) and the Japan Society for the Promotion of Science (JSPS): Grant-in-Aid-for Scientific Research (JP18H03783 and JP17H06931).