Simulation of Dynamic Resistance and Total Loss of HTS CORC Cables

In some high temperature superconducting (HTS) applications, HTS coated conductors carry DC current under external AC magnetic fields. Dynamic resistance occurs when the amplitude of the magnetic field is greater than the threshold magnetic field of the coated conductors. The resulting AC loss, termed as total loss, consists of dynamic loss due to dynamic resistance and magnetization loss due to the shielding currents caused by the AC magnetic field. Conductor on round core (CORC) cables wound with HTS coated conductors have attracted broad attention due to their large current-carrying capability and mechanical flexibility for coil applications. However, there has been no report on dynamic resistance and total loss in CORC cables. In this work, we present 3D FEM simulation results on the dynamic resistance and total loss of a spiral tape and three CORC cables, based on the T-A formulation. The number of layers of the CORC cables, the amplitude of the AC magnetic field and transport DC current levels have been varied to study the impact of those parameters on dynamic resistance and total loss of the three CORC cables. The simulation results show that magnetization loss without current in a spiral tape can be analytically estimated by Brandt and Indenbom's theoretical equation for a superconducting strip under perpendicular AC magnetic field with a geometric coefficient 2/pi . Furthermore, dynamic resistance of the spiral tape and each tape in a single-layer cable can be predicted by the analytical equation for a strip carrying DC current under perpendicular AC magnetic field, also taking into account the geometric coefficient 2/pi. The simulation results also show that the difference of total loss values in the three CORC cables depends on the shielding effect: the more layers of CORC cables, the lower each loss component. The two-layer Cable with each tape in the outer layer sitting on top of the tape in the inner layer has the lowest loss and the highest threshold magnetic field.

Automated summary

In some high temperature superconducting (HTS) applications, HTS coated conductors carrying DC current under external AC magnetic field exhibit dynamic resistance. This resistance leads to AC losses, which include dynamic loss and magnetization loss. Conductor on round core (CORC) cables, made up of HTS coated conductors, are attractive for coil applications due to their large current-carrying capability and mechanical flexibility. However, there is no report on dynamic resistance and total loss in CORC cables. In this study, 3D FEM simulations are used to analyze the dynamic resistance and total loss of a spiral tape and three CORC cables, taking into account various parameters such as the number of layers, the amplitude of the AC magnetic field, and the transport DC current levels. The simulation results show that the total loss values in the CORC cables depend on the shielding effect, with the two-layer cable having the lowest loss and highest threshold magnetic field.