Simulation of Pulsed-Magnetization of HTS Jointless Loops With J-A Formulation With Circuit Coupling and Thermal Modeling

Abstract

The J-A formulation has been investigated as an easy and fast way to model superconducting systems in finite-element software. It is based on the common A-formulation, but two equations are applied. One to compute the magnetic field, which is the A-formulation equation, and one to compute the current density directly. By doing this, it is possible to use resistivity instead of conductivity to represent the superconductor, thereby eliminating a circular variable problem. This formulation has been investigated in both 2D and 3D, for thin-film approximations and homogenization methods, and the method to couple it with electric circuits has been recently proposed. This work explores it further by using the J-A formulation with circuit coupling and electro-thermal model to compute the thermal behavior of superconducting systems. It is applied to the pulsed-magnetization of HTS jointless loops, a system which has been investigated experimentally in previous works. The system is composed of a transformer with a common copper primary coil and the HTS jointless loop as secondary coil. The HTS loop placed in a nitrogen bath, modeled by the electro-thermal analogy method. An electric circuit is used to model the current continuity of the HTS loop. The J-A formulation computes the current density and the magnetic field. The pulses are investigated with a fixed pulse length and several pulse magnitudes, each in a different simulation. The induced persistent current is compared for all magnitudes, as well as the temperature rise for all layers of the HTS tape.