Screening current-induced field in non-insulated GdBCO pancake coil

Abstract

In this study, empirical and numerical analyses on the screening current-induced field (SCIF) characteristics of a non-insulated (NI) GdBCO-coated conductor single-pancake coil were conducted. Charge and discharge tests were carried out to induce an SCIF in the NI test coil. The SCIF in the NI coil was identified by comparison between the measured and calculated magnetic fields. The experimental results exhibit an increase of the SCIF with increasing an operating current, as well as a logarithmic decay of the SCIF as a function of time. Moreover, the SCIF was not affected by the slow discharge of the NI coil. The estimation of the SCIF based on the critical-state model in a thin film using the finite element method was in fairly good agreement with the experimental results.

Analysis of Current Distribution in Bi-2223/Ag Insert Pancake Coil

“…At the center of field invariant region p t1 , the self radial magnetic field induced by the discrete current densities all over the tape cross section, is equal to B rt (i). The self radial magnetic field at a point is calculated by (19). So, we can get a field equation with two unknowns, which is given in (20).…”

“…The current distribution in HTS coil is different from that of the low temperature superconducting (LTS) coil: Firstly, a certain tape in the coil is exposed to a transverse magnetic field generated by the other turns after the coil is charged, the transport current distribution will be nonuniform and asymmetrical to the tape conductor's center due to the combine effects of transport current and transverse magnetic field [2], [10]. Secondly, a screening current will flow in the superconducting tape after the coil is discharged [5], [19] or put into a transverse background magnetic field.…”

“…The model in [1], [3] obtained the magnetic field drift by calculating the screening current after the coil is charged. Yang et al [19] calculated the screening current on the basis of symmetrical transport current distribution after the coil is discharged. However, there is not a real screening current in the conductor after it is charged, and the actual transport current distribution will be non-uniform and asymmetrical to the center of conductor.…”

Finite-element modelling of no-insulation HTS coils using rotated anisotropic resistivity

“…However, a full resolution model of such NI coils is practically difficult to implement due to the high aspect ratio of the superconductor and the need to consider the currents flowing normal to the conductor's surface. While progress has been made using circuit grid models (CGM) [18,[24][25][26][27], these models lose axial fidelity and cannot simulate the associated shielding currents, and associated stress [28], within the HTS windings [23,[29][30][31].…”

Electromagnetic modelling using T‐A formulation for high‐temperature superconductor (RE)Ba 2 Cu 3 O x high field magnets

“…REBCO high field magnet often consists of thousands of turns, which makes the modelling much more difficult because of the huge computation. Some analytical methods have been developed to calculate the screen current in superconductor, which is simple and fast [26][27][28][29]. However, these methods cannot do a comprehensive electromagnetic analysis on the HTS, and are also not suitable for complex electromagnetic environments and operations.…”