Mechanical analysis of LIQHYSMES magnet during cooling and current-carrying process

As the important electromagnetic energy storage magnet unit of Liquid Hydrogen and Superconducting Magnetic Energy Storage (LIQHYSMES) system, the mechanical stability of toroidal D-shaped high temperature superconducting (HTS) energy storage magnet is crucial to the safe and stable operation of the system. In this paper, to analyze the mechanical behavior of the D-shaped coil during the cooling and current-carrying process, RVE model is first established to obtain the thermo-mechanical parameters of the stacked tapes. Subsequently, the three-dimensional homogenized mechanical model is developed to investigate the distribution characteristics of thermal and electromagnetic stresses. Furthermore, the influence of coil structural parameters and support material properties is explored. Finally, the multi-step finite element analysis method is employed to investigate the influence of the cooling process. The results imply that hoop stress dominates during both the cooling and current-carrying process, and thermal stress is the primary component of the total stress. For the 33 MJ/5 MW LIQHYSMES magnet, the current-carrying process further increases the hoop stress by 2.1%, while it alleviates the radial stress by 6.3%. In addition, increasing the stiffness of the inner support structure can effectively reduce hoop stress, but it exacerbates radial stress. Therefore, a trade-off between hoop strength and radial strength of the D-shaped coil must be considered in the design of the support structure.