Electrical measurements of AC losses in high temperature superconducting coils at variable temperatures

Nguyen, Doan N.; Kim, C H; Kim, J H; Pamidi, Sastry; Ashworth, S.P.

doi:10.1088/0953-2048/26/9/095001

Cited by 26 publications

(10 citation statements)

References 20 publications

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“…Previous studies have shown that AC loss in HTS windings with AC transport current of amplitude It and coil critical current Ic follows a power law ∝ ( ⁄ ) where the exponent n is between 2 and 4 [2][3][4][5][6][7][8][9][10]. By fitting our experimental data, we find that the loss varies with current according to a power law with exponent approximately 2.3 to 2.6 which is in accordance with previously reported values [2][3][4][5][6][7][8][9][10][11].…”

Section: B Coil Assembly Ac Loss Measurementsupporting

confidence: 91%

“…On the other hand, by using REBCO wire rather than BSCCO in a coil winding, there is the potential to reduce the AC loss in the coil winding. As a result, the literature is replete with reports of experimental and modelling studies on windings using either BSCCO or REBCO wire [2][3][4][5][6][7][8][9][10]. However, there are far fewer reports of hybrid coil assemblies employing either mixed wire types, or separate wires with different critical current, that are deliberately apportioned within the winding assembly.…”

Section: Introductionmentioning

confidence: 99%

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AC Loss Measurements in a Hybrid REBCO/BSCCO Coil Assembly

Jiang¹,

Staines²,

Long³

et al. 2021

Preprint

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Wire cost and ac loss are paramount issues for the future uptake of high-temperature superconductor (HTS) ac machines. In particular, new approaches which reduce the total manufacturing cost of HTS coils are critical to the future commercial uptake of HTS technology. Here, we present the results of ac loss measurements of a hybrid HTS coil assembly comprising end windings (EWs) wound with BSCCO wire and a central winding (CW) wound with REBCO wire. As a cost mitigation measure, we have chosen to use REBCO wire which possesses a relatively low self-field Ic at 77 K, equating to approximately half that of the BSCCO wire. Transport ac loss measurements were made on the total coil assembly at both 77 K and 65 K, using a recently developed lockin amplifier approach. We show the ac losses in the assembly at these temperatures scale with the overall transport critical current threshold of the hybrid coil assembly. The results are then compared with a reference coil assembly having similar geometrical dimensions, and in which both the EWs and CW were wound with identical BSCCO wire. Surprisingly, we observe that the ac loss of the hybrid coil is lower than that of the BSCCO coil, despite the CW of the hybrid coil employing wire a lower overall average Ic. We attribute this effect to the lower ac loss of coated conductor REBCO wire under parallel field, which is the dominant field orientation in the CW region. Based on this observation, we conclude that the hybrid assembly design is a good design strategy for HTS coil assemblies, enabling both wire cost and ac loss to be balanced. © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

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Section: B Coil Assembly Ac Loss Measurementsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

AC Loss Measurements in a Hybrid REBCO/BSCCO Coil Assembly

Jiang¹,

Staines²,

Long³

et al. 2021

Preprint

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show abstract

Section: Introductionmentioning

confidence: 99%

AC Loss Measurements in a Hybrid REBCO/BSCCO Coil Assembly

Jiang

Staines

Long

et al. 2017

IEEE Trans. Appl. Supercond.

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Wire cost and AC loss are paramount issues for the future uptake of HTS AC machines. In particular, new approaches which reduce the total manufacturing cost of HTS coils are critical to the future commercial uptake of HTS technology. Here, we present the results of AC loss measurements s of a hybrid HTS coil assembly comprising end windings (EWs) wound with BSCCO wire and a central winding (CW) wound with REBCO wire. As a cost mitigation measure, we have chosen to use REBCO wire which possesses a relatively low self-field Ic at 77 K, equating to approximately half that of the BSCCO wire.Transport AC loss measurements were made on the total coil assembly at both 77 K and 65 K, using a recently developed lockin amplifier approach. We show the AC losses in the assembly at these temperatures scale with the overall transport critical current threshold of the hybrid coil assembly. The results are then compared with a reference coil assembly having similar geometrical dimensions, and in which both the EWs and CW were wound with identical BSCCO wire. Surprisingly we observe that the AC loss of the hybrid coil is lower than that of the BSCCO coil, despite the CW of the hybrid coil employing wire a lower overall average Ic. We attribute this effect to the lower AC loss of coated conductor REBCO wire under parallel field, which is the dominant field orientation in the CW region.Based on this observation we conclude that hybrid assembly design is a good design strategy for HTS coil assemblies, enabling both wire cost and AC loss to be balanced.

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“…Furthermore, intensive AC loss analysis of HTS coils has been carried out both experimentally and numerically [14][15][16][17][18][19][20]. However, there has been no report to date on the influence of asymmetric wire critical current on coil AC loss.…”

Section: Introductionmentioning

confidence: 99%

Exploiting asymmetric wire critical current for the reduction of AC loss in HTS coil windings

et al. 2019

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Critical current and AC loss in coil windings are two important factors for various HTS applications. Many coated conductors exhibit asymmetry in the variation of the critical current with magnetic field angle. This asymmetry results in different coil critical current values depending on the orientation of the conductors in the coil windings. We report critical current and AC loss results at 77 K and 65 K for three hybrid coil assemblies which have a common central winding and different arrangements of the end windings. We found a difference greater than 13% in both the critical current and the AC loss results for the different arrangements. The results imply that if we wind coil assemblies smartly even using the same materials and the same design, we can not only improve critical current but also reduce AC loss significantly.

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Electrical measurements of AC losses in high temperature superconducting coils at variable temperatures

Cited by 26 publications

References 20 publications

AC Loss Measurements in a Hybrid REBCO/BSCCO Coil Assembly

AC Loss Measurements in a Hybrid REBCO/BSCCO Coil Assembly

AC Loss Measurements in a Hybrid REBCO/BSCCO Coil Assembly

Exploiting asymmetric wire critical current for the reduction of AC loss in HTS coil windings

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