Experimental Study of Squirrel Caged Damper Structure of Superconducting Generator

Abstract

We are developing a double layer damper which will consist of a squirrel-caged warm damper and a cylindrical cold damper as a part of our 70MW superconducting generator development project. To evaluate the characteristics of unbalance current capability, magnetic shielding and damping for rotor swing, we have constructed a 1/2 scale rotor model and conducted an experimental study. From analysis of the experimental results, we have developed design guidelines and refined our FEM magnetic field analysis technique.
The main results are summerized below:
(1) The squirrel-caged warm damper has sufficient capability against negative sequence current.
(2) Damping characteristics can be designed to be effective near the rotor swing frequency.
(3) Flux shielding at low frequencies corresponding to quick response excitation is sufficiently small so as not to prevent field flux change.
(4) Magnetic field can be analyzed by the refined FEM field analysis technique which now takes into account the effects of the rotor end region by estimating the end resistance based on eddy current flow path.