Development of a 50 A-fast response, magnetically controlled persistent current switch

We have developed a 50 A-fast response, magnetically controlled persistent current switch (Magnetic PCS), which is thought to be necessary also for a small to medium scale superconducting magnetic energy storage (SMES) system. A 10 m-long, 55 core, in-situ processed CuNb composite wire (0.3 mm /spl phi/, B/sub c2//spl sim/0.6 T, I/sub c//spl sim/136 A at 4.2 K and 0 T) with high resistivity CuNi alloy matrix was noninductively wound on a FRP bobbin and set into a control magnet which can be swept up to the maximum 1.2 T within 2 sec. The magnetic PCS was combined with a small superconducting magnet (0.5 H, 50 A, 5.5 T) and realized a persistent current mode at 50 A. The fast response was checked with a combination of an outer resistance load and by a switching-off of the magnetic PCS in a persistent current mode. The switching-off time of the magnetic PCS was shorter than 0.3 sec. An energy retaining test for about 50 min. was also performed. >