Dynamic resistance refers to the emergence of a DC electrical resistance in a superconductor carrying a DC transport current that is exposed to an oscillating AC magnetic field1,2. This phenomenon arises due to the interaction between the transport current and moving fluxons in the superconductor. Quantitatively predicting the magnitude of this effect is important when designing and utilising superconducting components for power system applications, in order to appropriately manage the associated AC losses. Examples of such superconducting components include: rotor coils for high power-density motors/generators and HTS flux pumps.
Here we present 2D numerical calculations of the dynamic resistance which occurs in parallel-connected stacks of ReBCO tapes. These calculations are performed using an H-formulation finite-element model¬3. The Jc(B,θ) dependence of the tape is described by interpolating experimental data obtained across the full range of field orientation for a wide range of field amplitudes. The modelling allows investigation of parallel connected tapes in a way that is problematic experimentally due to contact resistance variability in short length stacks.
Our results indicate that the outer tapes act to shield the inner regions of the stack, with this effect becoming less pronounced as the transport current approaches the stack critical current. Current is redistributed between the tapes such that dynamic resistance is zero at applied field amplitudes less than a threshold field. Above this threshold field dynamic resistance appears simultaneously in all tapes.
1. Mikitik G P and Brandt E H 2001 Phys. Rev. B 64, 092502
2. Oomen M P, Rieger J, Leghissa M, ten Haken B and ten Kate H H J 1999 Supercond. Sci. Technol. 12, 382
3. Mark D Ainslie et al 2018 Supercond. Sci. Technol. 31, 074003