Analysis on the Performances of a Rotor Screen for a 12 MW Superconducting Direct-Drive Wind Generator

A rotor screen, usually called the damper and made of magnetic or conductive materials, is located in a superconducting (SC) wind generator between SC field coils in a rotor and copper windings in a stator. The detailed analysis of the rotor screen is needed for the growing interest in SC wind generators. The rotor screen can isolate the SC field coils from ac magnetic fields produced by the stator. As the outer closure of the rotor, it should withstand the maximum forces in fault conditions. Moreover, its thickness should not be too large. Otherwise, it would increase the effective electromagnetic gap of the generator, resulting in more SC wires. In this paper, the rotor screen of a 12 MW SC direct-drive wind generator with an air-cored rotor is analyzed based on the 2-D finite element (2D FE) method. Electromagnetic performances of rotor screens with different thicknesses under the rated load state are studied after the short-circuit analysis. Then mechanical performances are analyzed under the maximum forces of fault condition.