Cryogenic isolating torque tubes for a superconducting generator-detailed model and performance analysis

Because of a suspected cryogenic insufficiency in the rotor of the 10 MVA superconducting generator a detailed analysis of the torque tubes was carried out and, to the extent possible with limited instrumentation, verified by actual experiment. The method used was a one-dimensional finite-element analysis with fixed end conditions. Nonlinear heat transfer was considered. The prediction of this analysis was that heat leak into the cold space would be small, confirming the initial design analyses. It also demonstrated that the initial analyses were robust to the major uncertainties, including steel-to-gas heat transfer. A brief description of the torque-tube system and a somewhat more detailed description of the thermal model developed for that system are given. A comparison with experimental data is shown.<>