The Characteristics of the Normal-Zone Propagation of the HTS Coils With Inserted Cu Tape Instead of Electrical Insulation

In the case of motors and generators, the benefits of using superconductors could be represented by the reduction of 50% in both losses and sizes compared to the conventional machines of the same rating. The high temperature superconducting (HTS) coils wound with HTS conductors have very low normal zone propagation velocity (NZPV) and complicated quench behaviors because the conductors have a low thermal conductivity and large specific heat. According to these reasons, in case of HTS coils and magnets, it is difficult to expect the self-protection like as low temperature superconducting (LTS) coils. In this paper, we suggest a method which inserts the Cu tape between turn-turn winding in the HTS coil instead of electrical insulation to improve the self-protection ability of HTS coils. Because the thermal and electrical contacts along the transverse direction are enhanced by inserted Cu tape instead of insulator and the whole thermal stability of HTS coils would be increased. To clarify the quench behavior of this suggested coil, we investigate the normal-zone propagation properties of the fabricated HTS pancake coils wound with 2G conductor and Cu tape under the cryocooled operation using GM cryocooler. The effects of inserted Cu tape and the improved the self-protection ability for the suggested HTS coil will be discussed.