Current Behaviors of NI REBCO Pancake Coil Wound With Multi-Bundled Conductors During Charging and Against Local Normal-State Transition

No-insulation(NI) Rare-Earth Barium Copper Oxide (REBCO) pancake coils can generate high magnetic fields and have the thermal stability against normal-state transition due to allowing currents radially bypass a local region through turn-to-turn contacts. Despite these merits, no insulation causes charging delay. To solve this delay problem, an NI REBCO coil wound with multi-bundled (MB) conductors was proposed. As experimental result, improved because inductance per tape of MB is smaller than that single-tape coil. Meanwhile, current behaviors are complicated has not been clarified. We investigated during transition, comparing without insulation. it shown be operated stably, pessimistic temperature rise observed. However, operating may concentrate on one when occurs. Therefore, seems desirable.