Development of testing apparatus for 10 kA class AC superconductors

R&D on NbTi and Nb/sub 3/Sn superconductors has been carried out for application to AC power apparatus in the Super-GM project. 5 kA class NbTi stranded cables have already been tested and then the R&D aiming at the final target of 10 kA class conductors is in progress. However there is no testing apparatus which makes it possible to measure over 5 kArms AC quench current (Iq) and AC loss in AC magnetic field (50-60 Hz). The testing apparatus was developed under the specifications required for evaluating the AC characteristics of 10 kA class conductors. The AC magnet generating the maximum magnetic field of 1 Tpeak in the bore of 150 mm was manufactured. For the Iq measurement, the AC current is directly applied to the specimen in the field of 0.5 Tpeak (50-60 Hz), 10 kArms AC quench current was obtained for the developed large NbTi conductors. As regards the AC loss measurement, the magnetization method using pick-up coils was adopted and its sensitivity has been improved by reducing unnecessary output signal.