Effects of copper former on the DC and AC transmission losses for conductor on round core cables.

This article focuses on the investigation of conductor on round core (CORC) cables, a promising type of superconducting cable for power applications, specifically examining the effects of copper formers with varying wall thicknesses on critical current (Ic) measurements and alternating current (AC) transition losses. The study found that in originally made CORC cables, a voltage arises on the copper former even when the applied current is below the cable’s Ic, causing direct current (DC) loss, which can be mitigated by a secondary-soldering technique that reduces contact resistance and improves current transfer from the former to the superconducting coated conductors (CCs). Experimental results demonstrate that AC losses in CORC cables with copper formers are frequency dependent and influenced by the former’s geometry, with copper tubes showing lower AC loss than copper bars at low frequencies but higher loss at high frequencies due to the skin effect. The work highlights the importance of optimizing copper former design and soldering methods to reduce AC and DC losses, thereby improving the efficiency and cryogenic maintenance costs of CORC cables in practical superconducting power applications.