Niobium-tin persistent-current switch for the superconducting magnet of Maglev

We designed and manufactured a persistent-current switch consisting of Nb/sub 3/Sn superconductive wire with an on-state current capacity of 600 A and an off-state resistance of 52 /spl Omega/ for the superconducting magnet of Maglev. To design a persistent current switch, it is important to suppress the instability such as degradation and training. Nb/sub 3/Sn has a higher critical temperature than that of NbTi which is commonly used for conventional persistent-current switches. Nb/sub 3/Sn wire is considered, therefore, to have higher stability to disturbance than NbTi wire. We reduced the volume and weight of the Nb/sub 3/Sn persistent-current switch to around 0.6 times and 0.7 times, respectively, that of the conventional NbTi persistent-current switch. Current-carrying capacity was tested both under the static and vibrating states. Test results of switching performance were compared with a computer simulation of temperature distribution in heating and cooling.