Influence of the voltage taps position on the self-field DC and AC transport characterization of HTS superconducting tapes

Vojenčiak, M.; Grilli, Francesco; Stenvall, Antti; Kling, A.; Goldacker, W.

doi:10.1016/j.cryogenics.2013.08.001

Cited by 6 publications

(5 citation statements)

References 17 publications

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“…In order to measure the critical current, voltage taps were placed on each tape outside the current contacts, on the superconductor side of each single meander tape. For comparison, voltage contacts were also placed inside the coil on two tapes, which resulted in the same I c , in agreement with the findings of experiments conducted on single tapes [12]. The transport AC losses were measured with the standard lock-in technique.…”

Section: Coil Preparation and Experimental Methodssupporting

confidence: 76%

“…This has an important influence on the AC loss as well, which increases with respect to that of the straight cable: in the case of the loosely wound coil (spacer 20 mm) only slightly, while in case of densely packed coil by more than 50 times. As discussed in [15] and confirmed by measurements in a dedicated study conducted on single tapes [12], the measured loss value is also influenced by the dissipation in the copper contact. As seen from the results reported above, the coil with the thinnest spacer has the highest loss.…”

Section: Coil Preparation and Experimental Methodssupporting

confidence: 64%

See 1 more Smart Citation

DC and AC Characterization of Pancake Coils Made From Roebel-Assembled Coated Conductor Cable

Kario¹,

Vojenčiak²,

Grilli³

et al. 2015

IEEE Trans. Appl. Supercond.

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Abstract-Roebel cables made of HTS coated conductors cancarry high currents with a compact design and reduced AC losses. They are therefore good candidates for manufacturing coils for HTS applications such as motors and generators. In this paper we present the experimental DC and AC characterization of several coils assembled from a 5 meter long Roebel cable built at KIT, which differ in the number of turns and turn-to-turn spacing. Our experiments, supported by finiteelement method (FEM) calculations, show that a more tightly wound Roebel coil, despite having a lower critical (and therefore operating) current, can produce a higher magnetic field than a loosely wound one. For a given magnetic field produced at the coil's center, all the coils have similar AC losses, with the exception of the most loosely wound one, which has much higher losses due to the relatively large current needed to produce the desired field. The experiments presented in this paper are carried out on the geometry of pancake coils made of Roebel cables, but they are exemplary of a more general strategy that, coupling experiments and numerical simulations, can be used to optimize the coil design with respect to different parameters, such as tape quantity, size, or AC loss -the relative importance of which is dictated by the specific application.

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Section: Coil Preparation and Experimental Methodssupporting

confidence: 76%

Section: Coil Preparation and Experimental Methodssupporting

confidence: 64%

DC and AC Characterization of Pancake Coils Made From Roebel-Assembled Coated Conductor Cable

Kario¹,

Vojenčiak²,

Grilli³

et al. 2015

IEEE Trans. Appl. Supercond.

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“…The best way is to measure all strands in parallel, which gives more information about the scattering of the properties of the strands. This can be done by placing voltage taps in different positions on the cable or behind the current leads [27]. An indirect way is to monitor the current sharing with a parallel applied copper shunt that gives an image of the V(I) graph of the whole cable [18].…”

Section: Current and Voltage Contactsmentioning

confidence: 99%

Roebel cables from REBCO coated conductors: a one-century-old concept for the superconductivity of the future

Goldacker

Grilli

Pardo

et al. 2014

Supercond. Sci. Technol.

264

139

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Energy applications employing high-temperature superconductors (HTS), such as motors/generators, transformers, transmission lines and fault current limiters, are usually operated in the alternate current (AC) regime. In order to be efficient, the HTS devices need to have a sufficiently low value of AC loss, in addition to the necessary current-carrying capacity. Most applications are operated with currents beyond the current capacity of single conductors and consequently require cabled conductor solutions with much higher current carrying capacity, from a few kA to up to 20-30 kA for large hydro-generators.A century ago, in 1914, Ludwig Roebel invented a low-loss cable design for copper cables, which was successively named after him. The main idea behind Roebel cables is to separate the current in different strands and to provide a full transposition of the strands along the cable direction. Nowadays, these cables are commonly used in the stator of large generators. Based on the same design concept of their conventional material counterparts, HTS Roebel cables from REBCO coated conductors were first manufactured at the Karlsruhe Institute of Technology (KIT) and have been successively developed in a number of varieties that provide all the required technical features such as fully transposed strands, high transport currents and low AC losses, yet retaining enough flexibility for a specific cable design. In the past few years a large number of scientific papers have been published on the concept, manufacturing and characterization of such cables. Times are therefore mature for a review of those results. The goal is to provide an overview and a succinct and easy-to-consult guide for users, developers, and manufacturers of this kind of HTS cables.

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“…Hence, all ten voltage taps are connected outside the terminations, where the RACC tapes are fanned out. As already proven, such measurement technique does not impair the I c measurement [14] but provides extra space for voltage taps. The current, however, is not measured for each single tape, but for the entire cable at the shunt of the power supply.…”

Section: Experimental Set-upmentioning

confidence: 73%

Mechanical reinforcement for RACC cables in high magnetic background fields

Bayer

Barth

Preuss

et al. 2015

Supercond. Sci. Technol.

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Operable in liquid helium, liquid hydrogen or liquid nitrogen, high temperature superconductor (HTS) cables are investigated as future alternatives to low temperature superconductor (LTS) cables in magnet applications. Different high current HTS cable concepts have been developed and optimized in the last years—each coming with its own benefits and challenges. As the Roebel assembled coated conductor (RACC) is the only fully transposed HTS cable investigated so far, it is attractive for large scale magnet and accelerator magnet applications when field quality and alternating current (AC) losses are of highest importance. However, due to its filamentary character, the RACC is very sensitive to Lorentz forces. In order to increase the mechanical strength of the RACC, each of the HTS strands was covered by an additional copper tape. After investigating the maximum applicable transverse pressure on the strand composition, the cable was clamped into a stainless steel structure to reinforce it against Lorentz forces. A comprehensive test has been carried out in the FBI facility at 4.2 K in a magnetic field of up to 12 T. This publication discusses the maximum applicable pressure as well as the behaviour of the RACC cable as a function of an external magnetic field.

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Influence of the voltage taps position on the self-field DC and AC transport characterization of HTS superconducting tapes

Cited by 6 publications

References 17 publications

DC and AC Characterization of Pancake Coils Made From Roebel-Assembled Coated Conductor Cable

DC and AC Characterization of Pancake Coils Made From Roebel-Assembled Coated Conductor Cable

Roebel cables from REBCO coated conductors: a one-century-old concept for the superconductivity of the future

Mechanical reinforcement for RACC cables in high magnetic background fields

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