Helium-Neon Gas Mixture Thermosyphon Cooling and Stability for Large Scale HTS Synchronous Motors

Commercial high-temperature superconducting (HTS) wires restrain us to an operation temperature ranging from 20 to 40 K for field-pole magnets applied to rotating machinery. We have proposed to employ a mixture of helium and neon gas in a closed-cycle thermosyphon based on a GM cryo-refrigerator. In this paper, we discuss the temperature stability of the evaporator created by a helium-neon mixture cooling coupled with a closed-cycle thermosyphon, upon an external heat load on a 100-kW-grade HTS synchronous machine. A home-made cooling system, including the condenser, was designed. The evaporator was assembled within the motor in accordance with thermal and mechanical analysis. The cooling of the evaporator with the 100-kW-grade HTS synchronous motor was applied against a variable heat load equivalent with the actual HTS rotor field poles. We report these results and propose its potential application to a large-scale ship propulsion motor.