TY - JOUR
T1 - Numerical Modelling of Dynamic Resistance in a Parallel-Connected Stack of HTS Coated-Conductor Tapes
AU - Brooks, Justin M.
AU - Ainslie, Mark D.
AU - Jiang, Zhenan
AU - Wimbush, Stuart C.
AU - Badcock, Rodney A.
AU - Bumby, Chris W.
N1 - Funding Information:
The author J. M. Brooks acknowledges financial support from the Victoria Doctoral Scholarship Scheme, and the Te Ati¯ Hau Trust.
Funding Information:
The author M. D. Ainslie acknowledges financial support from an EPSRC Early Career Fellowship EP/P020313/1. All data are provided in full in the results section of this article.
Funding Information:
Manuscript received September 24, 2019; accepted January 22, 2020. Date of publication February 25, 2020; date of current version March 13, 2020. This work was supported in part by the New Zealand MBIE Endeavour under Grant RTVU1707, and in part by the NZ Royal Society Marsden under Grant MFP-VUW1806. (Corresponding author: Justin M. Brooks.) Justin M. Brooks, Zhenan Jiang, Stuart C. Wimbush, Rodney A. Badcock, and Chris W. Bumby are with the Robinson Research Institute, Victoria University of Wellington, Lower Hutt 5046, New Zealand (e-mail: [email protected]).
Publisher Copyright:
© 2002-2011 IEEE.
PY - 2020/2/25
Y1 - 2020/2/25
N2 - Dynamic resistance is observed in type-II superconductors carrying a DC transport current while simultaneously exposed to an alternating magnetic field. The appearance of a non-zero resistance is attributed to the interaction between the transport current and moving fluxons. This effect is relevant to many superconductor applications such as high-Temperature-superconductor (HTS) flux pumps, DC/AC magnets, synchronous machines, and persistent current switches. Here, we present a finite element method (FEM) analysis of both the time averaged dynamic resistance and the instantaneous current sharing behaviour in a cable comprised of a stack of four YBCO thin films connected in parallel. Numerical modelling was performed using the H-formulation method implemented in the commercial software COMSOL. The model employs experimentally measured values of the angular dependence of the critical current Ic(B, θ) and the flux creep exponent n(B, θ). A single threshold field is observed, above which a finite dynamic resistance is observed in all tapes simultaneously. The time-Averaged dynamic resistance of individual tapes tends to be larger for the exterior tapes than the interior tapes, but this difference decreases as the total transport current in the cable increases. We attribute this to shielding currents flowing in the exterior tapes during the majority of the cycle, which displace net DC current into the interior tapes. However, the relative proportion of DC transport current flowing in the exterior and interior tapes is also observed to vary periodically once per half cycle of the applied field. This is due to the periodic trapping of return screening currents in the interior tapes.
AB - Dynamic resistance is observed in type-II superconductors carrying a DC transport current while simultaneously exposed to an alternating magnetic field. The appearance of a non-zero resistance is attributed to the interaction between the transport current and moving fluxons. This effect is relevant to many superconductor applications such as high-Temperature-superconductor (HTS) flux pumps, DC/AC magnets, synchronous machines, and persistent current switches. Here, we present a finite element method (FEM) analysis of both the time averaged dynamic resistance and the instantaneous current sharing behaviour in a cable comprised of a stack of four YBCO thin films connected in parallel. Numerical modelling was performed using the H-formulation method implemented in the commercial software COMSOL. The model employs experimentally measured values of the angular dependence of the critical current Ic(B, θ) and the flux creep exponent n(B, θ). A single threshold field is observed, above which a finite dynamic resistance is observed in all tapes simultaneously. The time-Averaged dynamic resistance of individual tapes tends to be larger for the exterior tapes than the interior tapes, but this difference decreases as the total transport current in the cable increases. We attribute this to shielding currents flowing in the exterior tapes during the majority of the cycle, which displace net DC current into the interior tapes. However, the relative proportion of DC transport current flowing in the exterior and interior tapes is also observed to vary periodically once per half cycle of the applied field. This is due to the periodic trapping of return screening currents in the interior tapes.
KW - Dynamic resistance
KW - H-formulation
KW - HTS cable
KW - HTS modelling
KW - parallel stack
UR - http://www.scopus.com/inward/record.url?scp=85082392728&partnerID=8YFLogxK
U2 - 10.1109/TASC.2020.2974860
DO - 10.1109/TASC.2020.2974860
M3 - Article
AN - SCOPUS:85082392728
SN - 1051-8223
VL - 30
JO - IEEE Transactions on Applied Superconductivity
JF - IEEE Transactions on Applied Superconductivity
IS - 4
M1 - 4702208
ER -