3D Simulations of Dynamic Resistance and Total Loss on HTS CORC Cables at Various Temperatures

Abstract

Conductor on round core (CORC) cables carry a dc current under ac magnetic fields when applied onto the field windings of rotating machines, high-field magnets, and maglev systems. The resulting total loss, consisting of magnetization loss from external ac field and dynamic loss due to the interactions between the dc current and the ac field, will cause power dissipations in the cryogenic system. In this work, the dynamic resistance ($R_{\text{dyn}}$) and total loss in a spiral tape and two CORC cables assembled with 4-mm wide REBCO coated conductors are numerically obtained under ac field amplitudes up to 500 mT and temperatures ranging from 30 K to 77.5 K, with dc current levels i ($I_{\text{dc}}$/$I_{c0}$) from 0.05 to 0.9 where $I_{\text{dc}}$ is the transport current value and $I_{c0}$ is the self-field critical current at each temperature. Simulation results show the effective penetration field $B_{\text{eff}}$, where the peaks of the normalized magnetization loss without current, $Q_{m,0}$/$B_{\mathrm{m}^{2}}$, of the spiral tape, one-layer Cable A, and two-layer Cable B, shifts to a large value with decreasing temperatures due to the increase of critical currents. In addition, the threshold field $B_{\text{th}}$ together with the normalized $B_{\text{th}}$/$I_{c0}$ at three temperatures of the spiral tape and Cable A can be estimated using the equation for a superconducting strip, while that of values for Cable B are higher than the analytical curves due to the shielding effect. A finite dynamic loss $Q_{\text{dyn}}$ below $B_{\text{th}}$ for three models at all temperatures is observed and this is due to a nonzero electric field caused by flux creep. The total loss at higher fields increases as temperature decreases from 77.5 K to 30 K except for i ≥ 0.5 at 77.5 K and i = 0.9 at 50 K where the occurrence of flux flow loss leads to a surge in total loss.