Design studies of superconducting generators

An Electric Power Research Institute sponsored study of superconducting, central-station turbine-generators of 300 and 1200 MVA rating has been completed at General Electric. A unique construction concept is used for the superconducting field winding. The goal of this construction is to ensure that the winding can be energized to the current and flux density predicted by the superconductor short-sample data, without the "training" instabilities frequently encountered in large coils. The remainder of the rotor components includes an aluminum radiation shield and a compound, steel-aluminum electromagnetic shield, designed to withstand short circuit electromagnetic forces. The study was focused on generator model configurations which were proportioned to have a low transient reactance, approximately 0.2 per unit. The critical clearing times calculated for these configurations were comparable to those of conventional units, the low reactance offsetting an inherently lower rotor inertia. These generator configurations are estimated to have about half the size and weight, and about half the losses of conventional units of the same rating. Transient characteristics are described, including the effect of the rotor shielding configuration on rotor damping.