A simple protection evaluation method for no-insulation REBCO pancake coils during local normal-state transition

So Noguchi, Seungyong Hahn, Atsushi Ishiyama, Yukikazu Iwasa

Research output: Contribution to journalArticle

Abstract

No-insulation (NI) and metal-insulation (MI) winding techniques are promising for enhancing the thermal stability of REBCO pancake coils, toward the practical use of nuclear magnetic resonance and magnetic resonance imaging systems. The NI and MI REBCO pancake coils showed high thermal stability in many over-current tests. However, a disadvantage is a charging delay due to low turn-to-turn contact resistance. Therefore, many researchers have tried to increase turn-to-turn contact resistance to overcome the charging delay problem. Meanwhile, a partial element equivalent circuit (PEEC) model can accurately simulate the over-current and charging/discharging tests of NI REBCO pancake coils in detail. Using the PEEC model coupling with thermal finite element analysis (FEA), the thermal stability was evaluated during a local normal-state transition. From the simulation results, it was found that a best range of turn-to-turn contact resistance existed to keep a high thermal stability during a local normal-state transition. However, the PEEC and thermal FEA method requires a substantial amount of time with complicated simulation approach. In this paper, we propose a simple mathematical formulation to obtain an appropriate range of turn-to-turn contact resistance during a local normal-state transition, supposing a worst cooling condition. The simple computation is easy to use and timesaving to roughly estimate the operation reliability of NI REBCO pancake coils.

Original languageEnglish
Article number045001
JournalSuperconductor Science and Technology
Volume32
Issue number4
DOIs
Publication statusPublished - 2019 Feb 15

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Keywords

  • no-insulation winding technique
  • quench protection
  • superconducting magnet

ASJC Scopus subject areas

  • Ceramics and Composites
  • Condensed Matter Physics
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry

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