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Local electromagnetic properties and hysteresis losses in uniformly and non-uniformly wound superconducting racetrack coils

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journal contribution
posted on 21.04.2020, 14:38 by BC Robert, MU Fareed, HS Ruiz

A noteworthy physical dependence of the hysteresis losses with the axial winding misalignment of superconducting racetrack coils made

with commercial second generation high temperature superconducting (2G-HTS) tapes is reported. A comprehensive study on the influence

of the turn-to-turn misalignment factor on the local electromagnetic properties of individual turns is presented by considering six different

coil arrangements and ten amplitudes for the applied alternating transport current, Ia, together with an experimentally determined function

for the magneto-angular anisotropy properties of the critical current density, Jc(B, θ), across the superconducting tape. It has been found

that for moderate to low applied currents Ia 0:6 Ic0, with Ic0 the self-field critical current of individual tapes, the resulting hysteretic losses

under extreme winding deformations can lead to an increase in the energy losses of up to 25% the losses generated by a perfectly wound

coil. High-level meshing considerations have been applied in order to get a realistic account of the local and global electromagnetic properties of racetrack coils, including a mapping of the flux front dynamics with well defined zones for the occurrence of magnetization currents,

transport currents, and flux-free cores, which simultaneously has enabled an adequate resolution for determining the experimental conditions when turn-to-turn misalignments of the order of 20–100 μm in a 20 turns 4 mm wide racetrack coil can lead not only to the increment

of the AC losses but also to its reduction. In this sense, we have shown that for transport current amplitudes Ia . 0:7 Ic0, a slight reduction

in the hysteresis losses can be achieved as a consequence of the winding displacement, which is at the same time connected with the size

reduction of the flux-free core at the coil central turns. Our findings can be used as a practical benchmark to determine the relative losses

for any 2G-HTS racetrack coil application, unveiling the physical fingerprints that possible coil winding misalignments could infer.

Funding

The authors acknowledge the use of the High Performance Computing Cluster Facilities (ALICE) provided by the University of Leicester. This work has been supported by the EPSRC (Grant No. EP/S025707/1). H.S.R. has led the team and contributed toward the analysis and writing of the paper. B.C.R. acknowledges the Niger Delta Development Commission for their funding support and has contributed toward the model’s development, analysis and plotting of results, and writing of the paper. M.U.F. acknowledges the College of Science and Engineering Scholarship Unit of the University of Leicester and has contributed toward some of the computational tasks derived from this paper.

History

Citation

Journal of Applied Physics 126, 123902 (2019); https://doi.org/10.1063/1.5100223

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Engineering

Version

VoR (Version of Record)

Published in

Journal of Applied Physics

Volume

126

Pagination

123902

Publisher

AIP Publishing

issn

0021-8979

Acceptance date

02/09/2019

Copyright date

2019

Available date

24/09/2019

Publisher version

https://aip.scitation.org/doi/full/10.1063/1.5100223

Language

en

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