Calculation of eddy current in the damper of a superconducting generator

FEM (finite-element method) calculations were performed for the eddy current in the damper of a superconducting generator (SCG). The method employed is the formulation proposed by C.R.I. Emson and J. Simkin (1983) which uses a modified magnetic vector potential inside conducting regions and a magnetic scalar potential in nonconducting regions. The calculated structure consists of the armature and two cocylindrical dampers (inner and outer dampers), where the inner damper is a metal sandwich of stainless steel/copper/stainless steel. The screening effect of the damper calculated for two- and three-dimensional conditions agreed very well with other calculations and experiment. The present method is difficult to apply for a frequency below 0.02 Hz due to the slower convergence, while the current-sheet T (current vector potential) method seems inappropriate above 200 Hz due to the increase of subdivided elements