Performance of Epoxy-Impregnated Intra-Layer No-Insulation (LNI) REBCO Coils at 77 K

Yoshida, T; Suetomi, Yu; Takahashi, Keisuke; Takao, T.; Yanagisawa, Yoshinori; Maeda, Hideaki; Ueda, Hiroshi

doi:10.1109/tasc.2021.3065875

Cited by 5 publications

(3 citation statements)

References 18 publications

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“…6). It is known that an epoxy-impregnated REBCO coil shows degradation in its performance due to delamination of a conductor from thermal contraction stresses during cooling [21,22]. An RC-LNI-REBCO coil, as proposed in the present work, does not show such degradation since each layer is mechanically decoupled by the interlayer sheet although the turns in each layer are bonded by epoxy resin.…”

mentioning

confidence: 75%

Development of an Intra-Layer No-Insulation (LNI) REBCO Coil Implemented With a Resistance-Controlled (RC) Interface

Tanaka,

Suetomi,

Kawahata

et al. 2024

IEEE Trans. Appl. Supercond.

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The intra-Layer No-Insulation (LNI) method achieves self-protection characteristics against quenching in a layerwound REBCO coil, owing to a current bypass function associated with the copper sheet inserted in each layer. The selfprotection is strongly influenced by the electrical contact resistivity (ρct) of the interface between conductors and copper sheets. In particular, a coil requires a high ρct value, typically of the 100 mΩcm 2 -class. However, the ρct value of a coil substantially changes due to external disturbances such as thermal cycles and electromagnetic forces. Therefore, it is vital to develop a technology to form an interface that provides a desired ρct value and that is stable against external disturbances. In the present work, we developed a basic method to form a resistancecontrolled (RC) interface with a layer thickness as thin as ~30 µm, using epoxy resin mixed with conductive and insulating fillers, which respectively act as current bypassing paths and spacers. A certain value of the mixing ratio of the conductive fillers provides a target ρct value from a wide range from 1 mΩcm 2 to 1,000 mΩcm 2 . An RC interface-implemented LNI-REBCO coil exhibits a stable ρct value under thermal cycles and selfprotection against an overcurrent quench in liquid nitrogen.

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confidence: 75%

Development of an Intra-Layer No-Insulation (LNI) REBCO Coil Implemented With a Resistance-Controlled (RC) Interface

Tanaka,

Suetomi,

Kawahata

et al. 2024

IEEE Trans. Appl. Supercond.

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“…For the NI REBCO coil, the deformation and separation between adjacent turns may have an effect on contact resistance in external fields. Many studis have calculated the mechanical deformations or stresses in REBCO conductors and NI coils numerically [34][35][36][37][38]. However, few works have focused attention on the effect of separation between adjacent turns on the contact resistance of NI coils.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of the contact resistance in a no-insulation layer-wound coil with a simplified electromagnetic–mechanical model

Li¹,

Tang²,

Liu³

et al. 2022

Supercond. Sci. Technol.

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The increase in contact resistance of no-insulation (NI) high-temperature superconducting (HTS) coil was observed in the high-field test, which may be related to the mechanical deformation and the separation between adjacent turns in the coil. The large electromagnetic force generated in the high magnetic field can cause the separation between adjacent turns of the NI coil, which can affect the contact resistance of the magnet. An electromagnetic-mechanical model is built to study the effect of separation on the contact resistance and field delay time of an NI layer-wound coil. The numerical results show that the large electromagnetic force generated in the high field leads to the local separation between adjacent turns and the increase of contact resistance of the NI layer-wound coil. Moreover, a higher external field or target current can result in a larger area of separation region, a higher contact resistance and a shorter characteristic field delay time. The overband can restraint the mechanical deformation and separation between turns of the NI coil in the high field, which suppresses the increase of turn-to-turn contact resistance.

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“…However, the layer-wound coil can provide better spatial homogeneity of the magnetic field, which is popular in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) [16][17][18][19]. To mitigate long magnetic field delay time, a new winding method has been proposed, named 'intra-layer noinsulation (LNI)' coil [20,21]. Specifically, a polyimide sheet and a copper sheet are both inserted between different layers of the layer-wound coil.…”

Section: Introductionmentioning

confidence: 99%

Ramping loss and mechanical response in a no-insulation high-temperature superconducting layer-wound coil and intra-layers no-insulation coil

Liu

Yong

2021

Sci. China Technol. Sci.

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The layer-wound coil has a great potential in nuclear magnetic resonance and magnetic resonance imaging owing to the better spatial homogeneity of the magnetic field. However, high-temperature superconducting (HTS) coil wound by no-insulation (NI) layer-wound technique has been verified with a long field delay time. A new method named the intra-layer no-insulation (LNI) winding technique has been proposed to reduce the charging delay time of the coil. This paper is mainly to study and compare the ramping loss and mechanical characteristics of the layer-wound coil and LNI coil. The results indicate that the total ramping loss can be significantly reduced by using the LNI winding method. The effects of the ramping rate of power supply current and the contact resistivity on the ramping loss are also discussed in the paper. Furthermore, the stress distributions in the layer-wound coil and LNI coil are compared, where the cooling process and Lorentz force are both considered. It can be found that the copper sheet of the LNI coil experiences relatively higher stress than its (RE)Ba 2 Cu 3 O x (REBCO) conductor layer. Meanwhile, the magnitude of stress generated in the REBCO conductor of the LNI coil is slightly different from that of the layer-wound coil.

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Performance of Epoxy-Impregnated Intra-Layer No-Insulation (LNI) REBCO Coils at 77 K

Cited by 5 publications

References 18 publications

Development of an Intra-Layer No-Insulation (LNI) REBCO Coil Implemented With a Resistance-Controlled (RC) Interface

Development of an Intra-Layer No-Insulation (LNI) REBCO Coil Implemented With a Resistance-Controlled (RC) Interface

Numerical analysis of the contact resistance in a no-insulation layer-wound coil with a simplified electromagnetic–mechanical model

Ramping loss and mechanical response in a no-insulation high-temperature superconducting layer-wound coil and intra-layers no-insulation coil

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