A Study on Electrical Characteristics of Multilayered Metallic-Insulation Coils

This paper presents results, both experimental and analytical, on the electrical characteristics of GdBCO single-pancake coils co-wound with a number of copper tapes as metallic insulation [multilayered metallic insulated (MMI) coil] through charge-discharge, dc pulse, and overcurrent tests. The charge-discharge and dc pulse test results for the coils demonstrated that MMI coils can be charged and discharged significantly faster than noninsulated (NI) or metallic-insulated (MI) coils. In overcurrent tests at 130 A (∼1.3I_c ), the MMI coils exhibited better electrical behavior than its counterpart co-wound with Kapton tape as turn-to-turn insulation. The charging-discharging delay times for the MMI coils decreased with an increasing number of metal tapes within the coils. Moreover, the experimental and analytical results are in good agreement, which demonstrates the validity of a concise equivalent parallel-RL circuit model for the MMI coil. Overall, the MMI winding technique is highly promising and can provide the development of compact, mechanically robust, and self-protecting REBCO magnets with enhanced thermal/electrical stability.