Magnetization and dynamic losses in full-scale twisted-stacked tape cables for HTS fusion applications

Abstract

AC loss is a key factor in the design of twisted-stacked tape cables (TSTCs) for high temperature superconductor (HTS) fusion applications. Until recently, numerical analysis of AC loss in full-scale TSTCs has been limited by the computational demands of 3D models, which severely restrict tape number and mesh density. In this work, a 2D scanning method, assessed against 3D models and experimental measurements, is used to simulate the magnetization and dynamic losses in full-scale TSTCs. A simplified PIT-VIPER geometry with four stacks, each containing 20–100 tapes, is modelled under alternating external magnetic fields of up to 20 T, at a temperature of 20 K, with and without 50 kA DC transport current. The influence of field-dependent critical current on magnetization loss is examined by comparing tapes from different manufacturers. The critical currents of the cables are also simulated. Results show that, for low transport currents, reducing tape number can reduce AC losses, roughly in proportion with tape number. Furthermore, it is shown that the widely used $2/\pi$ scaling of loss in flat stacks introduces moderate error until relatively high fields for practical tape numbers.