Mechanism of notable difference in the field delay times of no-insulation layer-wound and pancake-wound REBCO coils

Suetomi, Yu; Yanagisawa, Kyoko; Nakagome, Hideki; Hamada, Mamoru; Maeda, Hideaki; Yanagisawa, Yoshinori

doi:10.1088/0953-2048/29/10/105002

Cited by 32 publications

(42 citation statements)

References 10 publications

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“…Insulated coils -in which the coil is either co-wound with an electrical insulator or the conductor itself has an insulator coating -suffer from stability issues and are prone to damage due to local defects. Non-insulated (NI) coils [4], where the HTS tapes are wound without turn-to-turn insulation, are also actively researched [5][6][7][8][9][10][11] as an alternative. One of the main benefits of such coils is their proven selfprotecting behavior [4,12,13] due alternative current paths via the turn-to-turn resistances.…”

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confidence: 99%

Fluorescent thermal imaging of a non-insulated pancake coil wound from high temperature superconductor tape

Gyuráki

Benkel

Schreiner

et al. 2019

Supercond. Sci. Technol.

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We have wound a 157-turn, non-insulated pancake coil with an outer diameter of 85 mm and we cooled it down to 77 K with a combination of conduction and gas cooling. Using high-speed fluorescent thermal imaging in combination with electrical measurements we have investigated the coil under load, including various ramping tests and over-current experiments. We have found found that the coil does not heat up measurably when being ramped to below its critical current. Two over-current experiments are presented, where in one case the coil recovered by itself and in another case a thermal runaway occurred. We have recorded heating in the bulk of the windings due to local defects, however the coil remained cryostable even during some over-critical conditions and heated only to about 82-85 K at certain positions. A thermal runaway was observed at the center, where the highest magnetic field and a resistive joint create a natural defect. The maximum temperature, ∼100 K, was reached only in the few innermost windings around the coil former.

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confidence: 99%

Fluorescent thermal imaging of a non-insulated pancake coil wound from high temperature superconductor tape

Gyuráki

Benkel

Schreiner

et al. 2019

Supercond. Sci. Technol.

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“…In comparison to the NI pancake-wound coil, the NI layerwound coil has a longer magnetic field delay time, which has been validated in previous publications [15,16]. 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].…”

Section: Introductionmentioning

confidence: 81%

“…The current in each turn is calculated by an equivalent axisymmetrical circuit model [16,20,40,42], as shown in Figure 1(c) and (d). For the layer-wound coil, the current of each turn can flow into adjacent turns through the contact surface.…”

Section: Equivalent Circuit Modelmentioning

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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“…It has been demonstrated that at steady-state conditions current sharing is determined by the terminal resistances for cables with insulation between tapes [19]- [22]. Different numerical methods and software have been implemented to analyze the electrical behavior of HTS cables [23]- [26].…”

Section: Introductionmentioning

confidence: 99%

An Electric-Circuit Model on the Inter-Tape Contact Resistance and Current Sharing for REBCO Cable and Magnet Applications

Martínez

Prestemon

et al. 2020

IEEE Trans. Appl. Supercond.

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Mechanism of notable difference in the field delay times of no-insulation layer-wound and pancake-wound REBCO coils

Cited by 32 publications

References 10 publications

Fluorescent thermal imaging of a non-insulated pancake coil wound from high temperature superconductor tape

Fluorescent thermal imaging of a non-insulated pancake coil wound from high temperature superconductor tape

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

An Electric-Circuit Model on the Inter-Tape Contact Resistance and Current Sharing for REBCO Cable and Magnet Applications

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