open access

https://hdl.handle.net/2115/92378

Contact Resistance Change Due to Air Gap Generation Between Turns of NI REBCO Pancake Coils

英語

turn-to-turn contact resistance

2024-08

IEEE (Institute of Electrical and Electronics Engineers)

IEEE transactions on applied superconductivity

34(5)

6601905

Rare-earth barium copper oxide (REBCO) magnets with excellent current characteristics under high temperature and high magnetic field has been developed for various applications worldwide. No-insulation (NI) REBCO coils allow currents to avoid flowing into normal-state transition regions due to turn-to-turn direct contacts, improving the thermal stability on the NI REBCO coils. The turn-to-turn contact resistances on NI REBCO coils are very important for thermal stability; but they change according to the turn-to-turn contact surface conditions. The contact condition is severely deteriorated when REBCO tape surfaces are not in contact. Our previous research pointed out that deformations on small-bore NI insert coils derived from strong stresses make some air gaps under high external magnetic field and high operating current, resulting in increase in the turn-to-turn contact resistances. In this paper, to investigate the air gap behaviors, an electromagnetic and stress simulation considering individual turn movements is conducted. A contact area ratio and a whole contact resistance of an NI REBCO pancake coil is computed. As the result, under the operating current of 50 A, the turn-to-turn contact conditions deteriorate by air gap generation between turns with the increase of the background fields. However, under 10 T, the turn-to-turn contact conditions improve as the operating current increases beyond 50 A. The air gap related with the distribution pattern of BJR stress, but not the strength of BJR stress.

学術雑誌論文

Accepted Manuscript

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