HTS Pancake Coils Without Turn-to-Turn Insulation

TLDR

The study investigates high‑temperature superconductor pancake coils fabricated without turn‑to‑turn insulation. The authors wound three no‑insulation pancake coils—two Bi2223 (single and double) and one ReBCO single—and validated an equivalent electrical circuit model through charge‑discharge, sudden‑discharge, and overcurrent tests. The NI winding improves overall current density, thermal stability, and mechanical integrity compared to insulated coils.

Abstract

This paper reports a study of HTS pancake coils without turn-to-turn insulation. Three no-insulation (NI) pancake coils were wound: each single and double pancake coil of Bi2223 conductor and one single pancake of ReBCO conductor. An equivalent electrical circuit for modeling NI coils was verified by two sets of test: 1) charge-discharge; and 2) sudden discharge. Also, an overcurrent test in which a current exceeding a coil's critical current by 2.3 times was performed, and analysed, to demonstrate that in terms of stability NI HTS coils outperform their counterparts. The new NI winding offers HTS coils enhanced performance in three key parameters: overall current density; thermal stability; and mechanical integrity.