Kaoru NEMOTO, Suzuki Lab.(Cryogenic Technology), Maglev System Development Dept., RTRI
Takashi YAZAWA, Shunji NOMURA, Toshiba R&D Center
Seiichi MIYAKE, Showa Electric Wire and Cable Co. Ltd.
Kazumi SUGAWARA, Ship & Ocean Foundation

We designed and manufactured a 1000A-20Ħ class persistent current switch consisting of Nb3Sn superconductive wire for Magnetohydrodynamic Propulsion Ship(MHDS). In designing the persistent current switch, it is important to suppress the instability such as degradation and training. Nb3Sn has higher Tc than NbTi which is commonly used for the conventional persistent current switch. Therefore, Nb3Sn wire is considered to have higher stability to disturbance than NbTi wire. The 1000A-20Ħ class persistent current switch is used for the first stage in research of current carrying performance and switching performance of the switch with Nb3Sn wire before completing the MHDS's persistent current switch which in future is expected to carry 10kA stably. Fig.1 shows an appearance of the 1000A-20Ħ class persistent current switch. Main properties of the Nb3Sn wire are listed in Table 1.

Current carrying capacity was tested under both static state and vibrating state, and sufficiently stable performance was confirmed. The currents at which the persistent current switch has changed from superconducting state to normal resistive state are described in Fig.2. Table 2 shows the vibrations suffered. Switching performance was tested too, electrical resistance off-state attained 20Ħ on account of heating power of 10W, and switching time was held under 1 minute, as shown in Table 3.

These successful results prove the stable performance of the persistent current switch with Nb3Sn wire, and promise the realization of a high current carrying performance persistent current switches intended not only for MHDS but also for Maglev, SMES and the like.

This work was supported financially by The Nippon Foudation.

Table 1
1) M.Urata, et.al. :"Stabilization of a Nb3Sn persistent current switch", Fusion Engineering and Design, 20, pp409-414, 1993