AC Loss Estimation Method for REBCO Superconducting Tapes in AC+DC Fields for Field Windings in Fully Superconducting Synchronous Machine for Electric Aircraft

The estimation of AC loss in REBa2Cu3Oy (REBCO; RE = rare earth, such as Y, Eu, and Gd) superconducting tapes within superconducting synchronous motors and generators for electric aircraft is imperative during the design stage phase to optimize efficiency and cooling considerations. Our previous studies clarified the AC loss characteristics, focusing on estimating the AC loss in armature windings. While the magnetic field applied to the armature windings is exclusively as an AC field, the field windings are subject to a composite field comprising both AC and DC components. Notably, the amplitude of the AC component is markedly smaller than the magnitude of DC component. This study experimentally investigated to consider the AC loss properties in field windings. The experimental results were as follows: When subjected to operational conditions of field windings within synchronous motor and generator, the AC loss increased with the DC field strength. This property is attributed to a reduction in the critical current induced by the external field. Hence, we modified the method for estimating AC loss. Subsequently, we validated the effectiveness of the modified method.