Current Flow Simulation of Assembled Conductors for Field Coils of Liquid Hydrogen-Cooled High-Temperature Superconducting Generator

High-temperature superconducting (HTS) generators that functions in combination with a hydrogen gas turbine have the potential to reduce CO2 emissions in Japan. The system can realize zero-emission power generation, and it requires no refrigerator and has almost no cooling costs by fully using the cold energy of liquid hydrogen. The ultimate goal is to commercialize a 600 MW-class liquid hydrogen-cooled HTS generator that requires a 6 kA-class assembled conductor with an outer diameter of approximately 6 mm that can conduct 6 kA at 20 K and 5 T. A technical challenge in applying assembled conductors to the field coils of generators is realizing the interlayer current distribution during steady-state operation and quick-response excitation. A conductor with four layers of 12 wires wound on a 5 mm-diameter former was experimentally and numerically studied, and the current distribution was examined. Similar waveforms were numerically obtained when the terminal resistance of each layer was set to 5/90/60/40 nΩ/m. Such variations in the terminal resistance have a slight effect on the transport characteristics of long conductors.