Dynamic resistance in high- T c superconductors is an electrical resistance that arises when superconductors carrying a DC current are simultaneously exposed to an alternating magnetic field1. This resistance arises once the AC field amplitude exceeds a threshold value and interactions between the transport current and screening current occurs. Quantitative analysis of this resistance is important when designing superconducting devices as this mechanism can lead to heat generation. This phenomenon can also be harnessed to act as a localized switching element in superconducting power electronics 2 3. Examples of these situations include high- T c flux pumps, magnets, and motors.
In the following calculated values from 2D models of dynamic resistance in hollow-strip geometries, fabricated from coated conductor ReBCO tapes is presented. The model is based on the T-A formulation which allows for computation of the local current density, electric and magnetic fields in a time-efficient manner and uses measurements of a commercial tapes Jc(B,q) data as an input. The computed values are compared with modelling data of a monolithic strip which has already been demonstrated to be quantitatively and qualitatively aligned with experiments4. A modelling approach for hollow strips is used due to the difficulty in fabricating hollow-strips from coated conductors with equal performance between each branch of the loop. The results demonstrate that the resistance of a hollow strip is significantly larger than that of a monolithic strip for the same applied current and magnetic field.
1. Mikitik, G.P. and Brandt, E.H., 2001. Generation of a dc voltage by an ac magnetic field in type-II superconductors. Physical Review B, 64(9), p.092502.
2. Geng, J., Brooks, J.M., Bumby, C.W. and Badcock, R.A., 2022. Time-varying magnetic field induced electric field across a current-transporting type-II superconducting loop: beyond dynamic resistance effect. Superconductor Science and Technology, 35(2), p.025018.
3. Geng, J., Matsuda, K., Fu, L., Shen, B., Zhang, X. and Coombs, T.A., 2016. Operational research on a high-Tc rectifier-type superconducting flux pump. Superconductor Science and Technology, 29(3), p.035015.
4. Brooks, J.M., Ainslie, M.D., Jiang, Z., Pantoja, A.E., Badcock, R.A. and Bumby, C.W., 2020. The transient voltage response of ReBCO coated conductors exhibiting dynamic resistance. Superconductor Science and Technology, 33(3), p.035007.
This work was supported by the Ministry of Business, Innovation and Employment, New Zealand under the Advanced Energy Technology Platform program “High power electric motors for large scale transport” contract number RTVU2004.