Numerical investigation on decreasing radial stress in epoxy impregnated REBCO pancake coils by overband

Abstract

Rare-earth-barium-copper-oxide (REBCO) coated conductors are promising conductors for high energy and high field superconducting applications. In the case of epoxy impregnated REBCO superconducting pancake coils, however, excessive radial tensile stress generated in the winding when the coils are cooled from room temperature to 77 K or less can cause delamination, resulting in irreversibly degradation in the coils. To ensure the stable operation of superconducting coils, it is important to decrease radial tensile stress in epoxy impregnated REBCO pancake coils. In this study, the fabrication method of overband radial build in epoxy impregnated REBCO pancake coils is presented and numerically analyzed. A two-dimensional axisymmetric finite element model (FEM) with the equivalent homogeneous coil properties is built and validated to analyze the effect of overband on the stress distribution in epoxy impregnated REBCO coils. Furthermore, a series of parametric studies on overband radial build effects on radial stress in an epoxy impregnated coil are carried out based on the proposed FEM. Finally, the predictions of radial stresses in epoxy impregnated REBCO coils with overbands made of different engineered materials are presented and evaluated. The results show that the fabrication method of constructing overband radial build in epoxy impregnated REBCO pancake coils can effectively reduce the radial tensile stress in the windings.