Development of a submerged winding induction generator for cryogenic applications

This paper discusses the development of a series of one-megawatt, 3.3 kV variable speed input, constant frequency output induction generators to be used while totally submerged in liquid methane at -161/spl deg/C. The specific purpose and application of these induction generators was to increase the overall efficiency of a gas liquefaction plant by replacing all inline Joule-Thomson expansion valves with cryogenic turbine generators and, as a by-product of this replacement, the cogeneration of electric power. Areas of concern during the development of the generators included optimization of the generator's voltage to maximize system life and efficiency, the impact of high-speed switching IGBTs on wire and ground insulation, the magnitude and effects of partial discharge in a cryogenic liquid environment and the compatibility of insulation materials to hydrocarbon based fluids at cryogenic temperatures.