Study of second generation, high-temperature superconducting coils: Determination of critical current

Abstract

This paper presents the modeling of second generation (2 G) high-temperature superconducting (HTS) pancake coils using finite element method. The axial symmetric model can be used to calculate current and magnetic field distribution inside the coil. The anisotropic characteristics of 2 G tapes are included in the model by direct interpolation. The model is validated by comparing to experimental results. We use the model to study critical currents of 2 G coils and find that 100 μV/m is too high a criterion to determine long-term operating current of the coils, because the innermost turns of a coil will, due to the effect of local magnetic field, reach their critical current much earlier than outer turns. Our modeling shows that an average voltage criterion of 20 μV/m over the coil corresponds to the point at which the innermost turns’ electric field exceeds 100 μV/m. So 20 μV/m is suggested to be the critical current criterion of the HTS coil. The influence of background field on the coil critical current is also studied in the paper.

Vortex shaking study of REBCO tape with consideration of anisotropic characteristics

“…where Si is the cross-section area of the i-th tape and Ii is the total current in the i-th tape [37,38].…”

Numerical simulations of electromagnetic behavior and AC loss in rectangular bulk superconductor with an elliptical flaw under AC magnetic fields

“…In the past ten years, the finite element method (FEM) has become the dominated method to solve the electromagnetic behavior and AC loss in HTSs due to the necessity of considering highly nonlinear E-J relationship, complex geometries and complicated electromagnetic circumstances [9][10][11][12][13][14]. Recently, the FEM models based on the H-formulation have been intensively developed to solve a variety of geometries for practical applications, such as bulk superconductors, coated conductors, Roebel cables and coils [4,[15][16][17][18][19][20][21]. The simulations results agree well with the analytical and experimental results.…”

Modeling and Experiment of the Current Limiting Performance of a Resistive Superconducting Fault Current Limiter in the Experimental System

“…The increase of the thickness of each layer of superconductor, aiming to speed up calculation, might result in inaccuracy of calculation result. Similarly, a 2D axisymmetric model using H formulation was proposed to calculate the quench propagation of superconducting coils in the case of heat pulses [4,5]. In the model, a simplified superconductor model was used by deleting the Ag and buffer layers to enable fast calculation.…”