An Overcurrent Controlled HTS Persistent Current Switch Without Any Additional Switching Triggers

A superconducting magnet, which operates in a persistent current mode (PCM), is able to reduce heat loss on current leads, therefore, gradually become promising and important in many industrial usages. To realize the PCM, a persistent current switch (PCS) is an indispensable part, which also greatly influences final charging quality, and PCS has been designed extending to many kinds. In this paper, another kind of PCS is proposed, which is made by a section of tape in a coil. The PCS is triggered by over-current directly from the current source without any additional switching triggers. Performance of the PCS in two different winding conditions (i.e., in an insulated (INS) coil and a no-insulation (NI) coil) are tested. Each coil tails is soldered together as a joint to form a closed current loop. Thus, four experimental cases can be investigated with regards to the four conditions: INS or NI coil with the section (i.e., the PCS) selected including the joint, which is used to form a closed loop or not. Results show that in certain conditions, 95% of source current ultimately flows into the coil, and the PCS is switched off at an optimal threshold value of successfully charging the coil and generating the least heat. Besides, the absence of additional switching triggers can reduce the weight and size of the magnet. Meanwhile, four equivalent electrical circuit models corresponding to the four experimental cases are established and verified.