Simulation of Current Profile and AC Loss of HTS Winding Wound by Parallel-Connected Tapes

Abstract

Field penetration and ac loss of high-temperature superconductor (HTS) windings wound by parallel-connected (PC) tapes are simulated and calculated. The simulation is given to a winding with six tapes, which are connected to produce either n = 1, 2, 3, or 6 PC current turns. The PC turns are basically organized as two main types according to whether the turn end is soldered or not. The soldering state is controlled by shunt resistances between HTS tapes. Therefore, six independent PC structures are used for simulation. In addition to the HTS tapes, normal conductors, representing the possible reinforcement layers or stabilizer layers, are also built in the finite-element analysis (FEA) model. The simulation is carried out using the FEA software ANSYS, which is combined with the self-developed resistivity-adaption algorithm, a code that can cope with arbitrary FEA software to simulate field penetration into HTS. More importantly, we used the circuit-field analysis, so that we can adjust n values and the shunt resistance independently while we are simulating the field penetration process. AC loss contributed from different parts of the winding is separately studied as QHTS, which is hysteresis loss generated in HTS; Qnor, which is eddy current loss generated in normal conductors; and Qcc, which is coupling loss generated in shunt resistances. The current profiles and QHTS in each tape of the winding are very sensitive to the specific n value. However, the total QHTS for different PC structures does not significantly change. Even under overestimation, Qnor can only be comparable with QHTS when the frequency exceeds 1000 Hz. Qcc is prominent at low transport currents but is naturally restrained at high transport currents.