AC Loss Reduction in HTS Coil Windings Coupled With an Iron Core Using Flux Diverters

Abstract

Iron cores are widely employed in high temperature superconducting (HTS) power devices to enhance the magnetic field and improve the power density. In spite of these benefits, the presence of iron cores leads to a substantial increase in AC loss within HTS coil windings. Therefore, it is necessary to estimate the AC loss of HTS coil windings coupled with iron cores to propose methods for loss reduction. An effective way to reduce AC loss is to apply flux diverters (FDs) near the HTS coil windings. In this work, the 3D T -A homogenization method is used to calculate AC losses of the 1DPC (double pancake coil)-, 2DPC-, 4DPC-, and 8DPC assemblies at different currents with four ferromagnetic combinations: with an iron core (IC), with an iron core and FDs (IC_FDs), with an air core (AirC), and with air core and FDs (AirC_FDs). To weaken the impact of the iron core, the enlarged distance between the iron core and coil assemblies is considered to investigate AC loss dependence on this distance. In addition, the influence of the positions of FDs on AC loss reduction is also analyzed. The simulation results demonstrate that FDs can reduce the AC loss in coil assemblies, even when the iron core is present, owing to the reduction of the perpendicular magnetic field component in the end discs. For the 4DPC and 8DPC assemblies with IC, increasing the distance while using FDs, or decreasing the vertical gap between the coil assemblies and FDs, are effective in reducing AC loss.INDEX TERMS AC loss, superconducting coils, iron core, flux diverters, finite element method (FEM), 3D T-A homogenization method.YUE WU received the B.Eng. degree in electrical engineering and automation from the

Experimental AC loss study on REBCO coil assemblies coupled with an iron cylinder

“…Several numerical and experimental studies on the influence of ferromagnetic materials in AC loss of HTS tapes, stacks, and coil windings have been conducted [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. Previous numerical works based on the finite element method (FEM) have shown that iron cores influence the AC loss of HTS coil assemblies [26][27][28][29][30][31][32]. For single pancake coils coupled with iron cylinders, AC loss simulations have implied that the incorporation of iron cores slightly increased coil AC losses [29,30].…”

“…For single pancake coils coupled with iron cylinders, AC loss simulations have implied that the incorporation of iron cores slightly increased coil AC losses [29,30]. On the other hand, the simulated AC loss value of a coil winding comprised of a stack of 8 DPCs coupled with an iron core is one order of magnitude greater than that without the iron core [31,32].…”