In many high temperature superconducting (HTS) applications, HTS coated conductors carry a DC current under an external AC magnetic field. In such operating conditions, dynamic resistance will occur when the amplitude of the AC magnetic field exceeds the threshold magnetic field due to the traversing magnetic field across the HTS conductors. Consequently, AC loss within the superconductors is composed of the dynamic loss component arising from dynamic resistance and the magnetization loss component caused by the shielding current due to the AC external magnetic field. We define the overall AC loss in the process as total loss which is one of critical issues for relevent HTS applications, such as persistent current switches, flux pumps and rotating machine field windings.

In this study, we investigate the dynamic resistance and  the total loss behaviour of a three-tape HTS stack under a perpendicular AC magnetic field at 77 K. The stack is assembled from three serial-connected 4mm-wide SuperPower REBCO coated conductors. The transport DC current level, the magnetic field amplitude and the frequency of the AC magnetic field have been varied to study the influence of these parameters on the dynamic resistance and the total loss. The experimental results were compared with 2D H-formulation finite element modelling (FEM) results for a single HTS conductor and the stack.

Keywords: Dynamic resistance, Magnetization loss, Total loss, REBCO stack