Multiphysics modeling of no-insulation HTS energy storage coils: Enhanced T-A formulation for electromagnetic-mechanical coupling under sequential excitation

Abstract

Numerical calculation method has become a key tool to study the electric-magnetic-mechanical coupling characteristics of high temperature superconducting (HTS) Energy Storage Coils, especially in the multi-physics field coupling environment. In this paper, the T-A formulation of Maxwell's equations is used due to its high computational efficiency, strong adaptability and low resource requirement. The mechanical-electromagnetic coupling behavior of a 32T fully superconducting magnet in three typical excitation modes is analyzed in depth. Aiming at the limitation of the azimuthal shunt problem of no-insulation (NI) coils on the application of the algorithm, this study adopts the weak form equations to weaken Faraday's electromagnetic induction law which characterizes the relationship between the electric field and the magnetic field. The coupling solution method of current vector potential T and magnetic vector potential A is innovatively adopted. And the Lagrange multipliers and global equations are introduced to improve the conventional Neumann boundary conditions, thus effectively modeling the complex current distribution in HTS NI coils. In addition, based on the discrete coupling model, the COMSOL Multiphysics sub-region coupling modeling method is utilized combining the tilt angle of the tape and the strain-dependent characteristics of the critical current. The accurate quantitative analysis of the hoop stress-strain and tilt angle distribution characteristics of the NI coil is realized. The research results provide an important theoretical basis and technical support for the design and optimization of high-performance NI superconducting magnets.