| Abstract: | In this paper a double-layer damper is developed which will consist of a squirrelcaged warm damper and a cylindrical cold damper as a part of a 70-MW superconducting generator development project. To evaluate the characteristics of unbalance current capability, magnetic shielding and damping for rotor swing, a one-half scale rotor model is constructed and an experimental study is made. From analysis of the experimental results, design guidelines have been developed and the FEM magnetic field analysis technique is refined. The main results are summarized as follows: - 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; and
- 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 the eddy current flow path.
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