Research on Dynamic Resistance and Magnetization Loss of CORC Windings for Superconducting AC Homopolar Machines

In the application of the superconducting ac homopolar machines (SAHMs), high temperature superconductor (HTS) exciting windings carry dc currents under external ac magnetic fields and generally cause dynamic loss and magnetization loss, which will deteriorate the stable operation of SAHM. The conductor on round core (CORC) cables is a promising choice for HTS exciting windings because of its high current-carrying capacity with low ac losses and excellent mechanical stability. In this study, the dynamic resistance and magnetization losses of CORC cables carrying a dc current under an ac magnetic field were studied using numerical and experimental methods at 77 K. The numerical methods [three-dimensional (3-D) H homogenization model, 3-D T-A full model, 3-D T-A homogenization model] were compared with experimental data to validate them. Subsequently, the current distribution of CORC cables was studied under different working conditions. The effect of weak anisotropy and the shielding effect of CORC cables on dynamic resistance was researched. In addition, the dependence of CORC structure parameters on dynamic resistance and magnetization losses was analyzed, which is very helpful for the engineering applications of CORC cables as the exciting windings in homopolar machines. Besides, the results provide a reference for dynamic loss behaviors in CORC superconductor.