Studies on Nb3Sn field coils for superconducting machine

This paper describes the experimental studies on several coils wound with multifilamentary (MF) Nb3Sn cables with reinforcing strip for superconducting rotating machine application. To apply Nb3Sn superconductor to field winding of a rotating machine, we investigated several coil performances of pre-reacted, bronze processed and stranded MF Nb3sn cables mainly in relation to stress effect. Bending strain up to 0.64% in strand and winding stress of 5 Kg/mm²have resulted non-degradation in coil performance. A pair of impregnated race-track coils designed for application to a 30 MVA synchronous condenser was energized successfully up to 80% of critical current without quench. The test results have demonstrated that the cable type Nb3Sn conductors provide adequate flexibility and tensile strength to meet our requirement for use in a rotating machine.