An experimental study on a superconducting generator with dual machine shield system

The authors have studied an optimal machine shield system through two experiments on a 20-kVA superconducting generator. The first experiment was carried out on a fully iron-less aluminum-shield machine which has only an aluminum eddy-current machine shield in the stator. The second experiment was carried out on a generator with a dual-shield system which was both an aluminum eddy-current shield and an iron magnetic shield. The result of the first experiment showed that the aluminum-shield machine exhibits so large an eddy-current loss in the shield that it would be difficult to operate the machine continuously. However, the second experiment shows that the dual-shield machine exhibits much smaller loss in the shielding system, and that it has higher output power than the aluminum-shield machine. From these experiments, it was concluded that insertion of a very thin iron shield between the armature winding and the eddy-current shield can improve the machine performance even if the iron shield were saturated.