A Study on the No Insulation Winding Method of the HTS Coil

This paper reports a study on BSCCO and ReBCO HTS (high temperature superconducting) test coils, layer-wound and double-pancake, with and without turn-to-turn insulation. Over current tests were performed in a bath of liquid nitrogen to compare stabilities of the test coils at 77 K. Saturation of magnetic fields from the NI (no insulation) coils, both BSCCO and ReBCO, was observed owing to current bypassing through turn-to-turn contacts in local quenches at operating currents higher than their critical currents. In the NI ReBCO coils, global quenches occurred at operating currents higher than the coil critical currents and quench recoveries were observed during discharge of the coils. The experimental results, obtained to date, demonstrate that the NI winding method enables remarkable improvement of thermal stability of the HTS coils.