Analyzing full electromagnetic behaviors of no-insulation, high-temperature superconducting coils with turn-to-turn bypass currents and persistent screening currents

Li, Yi

doi:10.1088/1361-6668/ab9d8d

Cited by 7 publications

(1 citation statement)

References 35 publications

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“…In these applications, although the NI HTS coil is always energized by DC transport current, it is inevitably exposed to external AC fields [11,[23][24][25]. Due to the absence of the insulation layer, a closed-circuit is formed between the superconducting layer and the turn-to-turn contacts in the NI HTS coil, and an eddy current is generated by the AC axial applied magnetic fields [26,27]. On the one hand, this eddy current adds an extra AC transport current to the DC operating current, which may significantly reduce the maximum operating current of the NI HTS coil.…”

Section: Introductionmentioning

confidence: 99%

Maximum DC operating current degradation and magnetization loss of no-insulation (RE)Ba₂Cu₃O _x coil under AC axial background magnetic fields

Xue¹,

Fu²,

Lu³

et al. 2022

Supercond. Sci. Technol.

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No-insulation (NI) high temperature superconductor (HTS) coil shows a great advantage on enhanced thermal stability during quenches. It is inevitably exposed to ripple AC magnetic fields in some applications, such as synchronous machines, tokamak magnets and maglev trains. The AC applied fields can induce an eddy current in NI coils due to the absence of turn-to-turn insulation. This eddy current may cause considerable maximum DC operating current degradation and additional magnetization loss in NI coils, which are still unclear. This paper is to study this issue by both experiments and simulations. An experimental platform is built to measure the maximum operating current of HTS coils exposed to AC axial applied fields, and the results show that the axial AC applied fields can lead to a significant maximum operating current degradation (22.9 % in this study) on the NI HTS coil due to the eddy current induced even though the field is parallel to tape’s ab-plane and has a very low amplitude and frequency (26.88 mT/50 Hz). Meanwhile, this low applied field has little effect on the critical current of insulated HTS coils. A numerical model is applied to elucidate the underlying physical mechanism of this phenomenon, and the magnetization loss induced by additional transport current is analyzed using this model. The influence of grading turn-to-turn resistivity technique is also investigated, and the results show that this technique can effectively prevent the maximum operating current degradation and reduce the magnetization loss of NI HTS coils exposed to AC axial applied fields.

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Section: Introductionmentioning

confidence: 99%

Maximum DC operating current degradation and magnetization loss of no-insulation (RE)Ba₂Cu₃O _x coil under AC axial background magnetic fields

Xue¹,

Fu²,

Lu³

et al. 2022

Supercond. Sci. Technol.

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Modeling HTS non-insulated coils: A comparison between finite-element and distributed network models

et al. 2023

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High-temperature superconducting (HTS) non-insulated (NI) coils have the unique capability to bypass current through conductive turn-to-turn contacts, mitigating the possibility of a catastrophic failure in the event of a quench. However, this turn-to-turn conductivity leads to a significant increase in the coil decay/charging time constant. To understand this phenomenon, several modeling techniques have been proposed, including the lumped and distributed network (DN) circuit models, and more recently the finite-element (FE) models. In this paper, the decay results obtained from modeling HTS NI pancake coils using both a DN model and a 2D FE model approach are evaluated and compared. Steady-state fields, and transient charging and decay behaviors are calculated with each model and the results compared. Key differences are highlighted, including the computation speed and the capturing of various physical phenomena. Both models exhibit non-exponential decay during initial coil discharge due to current redistribution between the inner and outer turns. In addition, the FE model exhibits other effects arising from current redistribution in both the radial and axial directions, including remanent magnetization, and variation of the “apparent total inductance” during charging. Simulations of sudden discharge have also been analyzed using the common “lumped circuit” formula. This shows that extracted values for the apparent surface contact resistance between coil windings can differ by more than a factor of 5 from the initial input value. Our results confirms the optimal choice of architecture for future NI coil models and emphasize that caution should be exercised when interpreting experimental results using the lumped circuit approach.

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3D electromagnetic assessment of bended CORC® cables

Clegg,

Ruiz

2024

Journal of Applied Physics

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Conductor on round core (CORC®) cables have emerged as a leading contender in high-temperature superconducting (HTS) cable designs, offering exceptional performance with current densities surpassing 300 A/mm2 and the ability to withstand high axial tensile and compressive strain. Despite their remarkable properties, optimizing CORC® cables remains a challenge, particularly in accurately estimating their AC losses under real-world conditions, which necessitates advanced numerical modeling techniques. Building upon recent advancements in simulating straight CORC® cables, where Bean’s-like current profiles were observed across the actual thickness of wound superconducting tapes, we introduce a tailored computational approach to enhance the processing speed of three-dimensional (3D) finite element models of wound HTS tapes. This tailored approach is specifically designed to address the complexities of bent CORC® cables, which exhibit helicoidal winding and are subjected to varying mechanical strain. We focus on analyzing their electromagnetic performance by transitioning from idealized straight-former designs to more realistic scenarios where cable-formers are bent to accommodate flexible cable routing or coil configurations. Our simulations consider a typical cable design comprising three 4 mm-wide SuperPower tapes (SCS4050) with a twist pitch of 40 mm. We demonstrate the capability to accurately model the full electromagnetic behavior of bent CORC® cables without the reduction of degrees of freedom, providing valuable insights into their performance under bending conditions. Our findings contribute to the ongoing optimization of CORC® cable designs for a wide range of practical applications in high-current and high-magnetic field environments.

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Analyzing full electromagnetic behaviors of no-insulation, high-temperature superconducting coils with turn-to-turn bypass currents and persistent screening currents

Cited by 7 publications

References 35 publications

Maximum DC operating current degradation and magnetization loss of no-insulation (RE)Ba₂Cu₃O _x coil under AC axial background magnetic fields

Maximum DC operating current degradation and magnetization loss of no-insulation (RE)Ba₂Cu₃O _x coil under AC axial background magnetic fields

Modeling HTS non-insulated coils: A comparison between finite-element and distributed network models

3D electromagnetic assessment of bended CORC® cables

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Analyzing full electromagnetic behaviors of no-insulation, high-temperature superconducting coils with turn-to-turn bypass currents and persistent screening currents

Cited by 7 publications

References 35 publications

Maximum DC operating current degradation and magnetization loss of no-insulation (RE)Ba2Cu3O x coil under AC axial background magnetic fields

Maximum DC operating current degradation and magnetization loss of no-insulation (RE)Ba2Cu3O x coil under AC axial background magnetic fields

Modeling HTS non-insulated coils: A comparison between finite-element and distributed network models

3D electromagnetic assessment of bended CORC® cables

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Product

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Maximum DC operating current degradation and magnetization loss of no-insulation (RE)Ba₂Cu₃O _x coil under AC axial background magnetic fields

Maximum DC operating current degradation and magnetization loss of no-insulation (RE)Ba₂Cu₃O _x coil under AC axial background magnetic fields