AC Loss Simulation in HTS Coil Windings Coupled With an Iron Core

AC loss generated in Superferric magnets composed of high temperature superconducting (HTS) coil windings and iron cores is one of critical issues for rapid-cycling synchrotrons (RCSs) application. In this work, we carried out 3D FEM AC loss simulations in HTS coil assemblies coupled with an iron core using the T-A homogenization method. The HTS coil assemblies consist of a stack of double pancake coils (DPCs) wound with 4 mm - wide Shanghai Superconductor wires with an average self-field critical current of 192.6 A. The numerical and experimental AC loss results of a DPC (1 DPC) without the iron core were compared to validate the 3D T-A homogenization method. Then, 3D AC loss simulations were carried out on the DPC assemblies with different number of DPCs with/without the iron core to investigate the influence of the iron core and the coil number on AC loss. The iron core causes increase in AC loss values of the DPC assemblies. AC loss increases by a factor of five in the 4 DPC assembly with the iron core compared with that without the iron core. The simulation result in the 4 DPC assembly with the iron core reveals that strong perpendicular magnetic field penetration occurs even in the center DPCs and this explains the substantial AC loss increase in the 4 DPC assembly.