A two-phase cooling system for superconducting A-C generator rotors

An analytical study of a two-phase cooling system for rotors of superconducting A-C generators is presented. The system employs a two-phase, irreversible flow process to deliver the helium to the superconducting winding such that the liquid is separated from the vapor by the rotation and forms a pool. The free surface of the pool is maintained at subatmospheric pressure and the winding, which is partially immersed in the liquid, is cooled by pool boiling at temperatures below 4.2 K. The essential feature of the process is the ability to externally control the level of liquid in the rotor, and to regulate the mass flow rate through the rotor to meet its steady state and transient requirements, irrespective of the rotationalspeed.