Code Development and Validation Towards Modeling and Diagnosing Current Redistribution in an ITER-Type Superconducting Cable Subject to Current Imbalance

Zani, L.; Gille, P.; Gonzales, C. E. Carrejo; Kuppel, Sylvain; Torre, A.

doi:10.13182/fst09-a8989

Cited by 5 publications

(1 citation statement)

References 10 publications

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“…For special cases (e.g. study of uneven current distribution), they can be seen as adjustable parameters of the model [23], but generally they are chosen equal and of high values in order to impose a uniform distribution of the current, relevant to an infinite length of strand or cable. However, in the length of interest of our strand, the current is not equally shared (since bending creates a non-uniform strain map), whereas equal and high values of the end-resistances artificially produce an even current distribution.…”

Section: Solution For the Electric Fieldmentioning

confidence: 99%

Analytical formulae for computing the critical current of an Nb₃Sn strand under bending

Ciazynski¹,

Torre²

2010

Supercond. Sci. Technol.

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Works on bending strain in Nb 3 Sn wires were initiated in support of the 'react-and-wind' technique used to manufacture superconducting coils. More recently, the bending strains of Nb 3 Sn strands in cable-in-conduit conductors (CICC) under high Lorentz forces have been thought to be partly responsible for the degradation of the conductor performance in terms of critical current and n index, particularly for the international thermonuclear experimental reactor (ITER) conductors. This has led to a new wave of experiments and modelling on this subject. The computation of the current transport capability in an Nb 3 Sn wire under uniform bending used to be carried out through the so-called Ekin's models, and more recently through numerical simulations with electric networks. The flaws of Ekin's models are that they consider only two extreme cases or limits, namely the so-called long twist pitch (LTP) or short twist pitch (STP) cases, and that these models only allow computation of a value for the critical current without reference to the n index of the superconducting filaments (i.e. this index is implicitly assumed to be infinite). Although the numerical models allow a fine description of the wire under operation and can take into account the filament's n index, they need a refined meshing to be accurate enough and their results may be sensitive to boundary conditions (i.e. current injection in the wire), also general intrinsic parameters cannot be easily identified. In this paper, we propose clearly to go further than Ekin's models by developing, from a homogeneous model and Maxwell's equations, an analytical model to establish the general equation governing the evolution of the electric field inside an Nb 3 Sn strand under uniform bending (with possible longitudinal strain). Within the usual strand fabrication limits, this equation allows the definition of one single parameter to discriminate the STP and LTP cases. It is also shown that whereas Ekin's LTP model corresponds well to a limiting solution of the problem when the transverse resistivity tends toward zero (or the twist pitch tends towards infinity), Ekin's STP model must be modified (improved) when the filament's n index is finite. Since the general equation cannot be solved analytically, we start from the LTP model and develop a first order correction to be applied when the transverse resistivity, the twist pitch and the filament's n index are finite. Using a simple but realistic law for depicting the strain dependence of the critical current density in the Nb 3 Sn filaments, we can fully compute the corrected expression and give the result under a general analytical formula for a strand submitted to both bending and compressive/tensile strains. The results are then compared in two different cases with those obtained with the numerical code CARMEN (based on an electrical network) developed at CEA. Last, a semi-empirical formula has been developed to evolve continuously from the LTP limit to the improved STP limit when the transverse resistivity evolves ...

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Section: Solution For the Electric Fieldmentioning

confidence: 99%

Analytical formulae for computing the critical current of an Nb₃Sn strand under bending

Ciazynski¹,

Torre²

2010

Supercond. Sci. Technol.

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show abstract

Mechanical-Electrical Modeling of Stretching Experiment on 45 ${\rm Nb}_{3}{\rm Sn}$ Strands CICCs

Torre

Bajas

Ciazynski

et al. 2011

IEEE Trans. Appl. Supercond.

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Mechanical and Electrical Modeling of Strands in Two ITER CS Cable Designs

Torre

Bajas

Ciazynski

2014

IEEE Trans. Appl. Supercond.

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Code Development and Validation Towards Modeling and Diagnosing Current Redistribution in an ITER-Type Superconducting Cable Subject to Current Imbalance

Cited by 5 publications

References 10 publications

Analytical formulae for computing the critical current of an Nb₃Sn strand under bending

Analytical formulae for computing the critical current of an Nb₃Sn strand under bending

Mechanical-Electrical Modeling of Stretching Experiment on 45 ${\rm Nb}_{3}{\rm Sn}$ Strands CICCs

Mechanical and Electrical Modeling of Strands in Two ITER CS Cable Designs

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Code Development and Validation Towards Modeling and Diagnosing Current Redistribution in an ITER-Type Superconducting Cable Subject to Current Imbalance

Cited by 5 publications

References 10 publications

Analytical formulae for computing the critical current of an Nb3Sn strand under bending

Analytical formulae for computing the critical current of an Nb3Sn strand under bending

Mechanical-Electrical Modeling of Stretching Experiment on 45 ${\rm Nb}_{3}{\rm Sn}$ Strands CICCs

Mechanical and Electrical Modeling of Strands in Two ITER CS Cable Designs

Contact Info

Product

Resources

About

Analytical formulae for computing the critical current of an Nb₃Sn strand under bending

Analytical formulae for computing the critical current of an Nb₃Sn strand under bending