Persistent Current HTS Magnet for Maglev Applications

Abstract

This paper describes a persistent current HTS magnet that has been developed for Maglev applications. The HTS coil for the magnet consists of 12 single-pancake coils wound with four parallel Ag-sheathed Bi2223 wires. The HTS coil is connected with a persistent current switch (PCS) made of YBCO films and cooled below 20 K by a two-stage GM pulse-tube cryocooler. Detachable current leads are used to reduce heat leakage to the 1st stage of the cryocooler. The initial target for the current decay rate of the magnet was 10 %/day. In order to achieve the target, wires with n-value of more than 14 in a range of 10^-9-10^-6 V/cm at 77 K, 0 T were selected and coil winding processes were improved. As the result, a current decay rate of 0.44 %/day was obtained under persistent current operation of the HTS magnet. To observe the mechanical capability of the magnet, mechanical vibration tests up to ±15 G and electromagnetic vibration tests were carried out.