The Swedish development of turbogenerators with directly water-cooled rotors

Large steam turbine-driven generators rated at a few hundred MW and higher constitute, in many respects, a big engineering challenge. The Swedish manufacturer of heavy electrical equipment, Asea was faced with this challenge in the late sixties, when the company started to develop such generators for nuclear power plants. Due to the company´s background, it was necessary to choose new design concepts, and Asea decided on a very unique concept, turbogenerators with directly water-cooled rotors. The development led to difficult teething problems before the generators could be delivered and operate satisfactory; a process, which took around a decade to complete. Since then, the operation records have been very good. These turbogenerators constitute the only existing group with a significant number of two-pole, directly water-cooled rotors. The background, the development and results are summarized in this paper.