Cryogenic Rotary Joints Applied to the Cooling of Superconducting Rotating Machinery

The cooling of high-temperature superconducting (HTS) rotating machinery is essential in many ways: enhancing the properties of the HTS material, ensuring safe and stable rotation, nullifying the effects of heat invasion from the outside or of a possible generation during operation, etc. It presents, however, a challenge, in the presence of the necessary cryogenic moving connection allowing the flow of cryogen into the rotor. Our laboratory has been developing cryogenic rotary joints applied to the flow of cryogenic condensed gases for many years, coupled to the thermosyphon technology at the liquid neon temperature. This paper deals with the evolution of the models through the years, to eventually emphasize the new-born model adapted to the 100-kW class marine propulsion HTS motors. The results were the absence of leak of the cryogen and a small heat invasion, even during a rotation test conducted at 90 rpm. The design of the cooling system of a 20-MW class propulsion motor is the final target of this national project.