Finite element modeling of thermal stability and quench propagation in a pancake coil of PbBi2223 tapes

The initiation and propagation of quench events in a high temperature superconducting (HTS) pancake coil were modeled using finite element software package ANSYS. The nonlinear temperature dependent heat generation in HTS composite over a wide current sharing range is calculated based on power-law E-J characteristics with temperature dependence of the n-value and critical current density. Thermal properties of the HTS composite and coil sections were measured and compared with estimated values based on data for individual coil components and the fill factor of the coil construct. The effect of replacing the complex coil winding structure with an effective continuum was investigated by examining the normal zone temperature profiles and minimum quench energy (MQE). With reducing operating temperature from 77 K to 30 K, MQE reduces correspondingly from 30 J to 15 J. Simulation results are found in satisfactory agreement with experimental results from a test coil wound with PbBi2223 tape.