Prediction of resistive and hysteretic losses in a multi-layer high-T_csuperconducting cable

Abstract

In this work, a model of a multi-layer high-Tc superconducting (HTS) cable that computes the current distribution across layers as well as the AC loss is presented. The case of a four-layer cable is analysed, but the method developed can be applied to a cable with an arbitrary number of layers. The cable is modelled by an equivalent circuit consisting of the following elements: nonlinear resistances, linear self- and mutual inductances, as well as nonlinear, hysteretic inductances. The first element takes into account the typical current–voltage relation for superconductors, the second introduces coupling among the layers and depends on the geometrical parameters of the cable, while the third describes the hysteretic behaviour of superconductors. In the analysis presented, the geometrical dimensions of the cable are fixed, except for the pitch length and the winding orientation of the layers. These free parameters are varied in order to partition the current across the layers such that the AC loss in the superconductor is minimized. The model presented allows us to evaluate rapidly the current distribution across the different layers and to compute the corresponding AC loss. The rapidity of the computation allows us to calculate the losses for many different configurations within a reasonable time. The model has first been used for finding the pitch lengths giving an optimal current distribution across the layers and for computing the corresponding AC loss. Second, the model has been refined, taking into account the effects of the magnetic self-field which, especially at high currents, can sensibly reduce the transport capacity of the cable, in particular in the outer layers.

Computation of Losses in HTS Under the Action of Varying Magnetic Fields and Currents

“…The error of this approximation is negligible for singlelayer cables. Moreover, thanks to symmetry, the cross-section in the computations can be reduced to a single circular sector [142], [143], [144]. Simulations for tapes with a ferromagnetic substrate show that its presence always increases the ac losses [145], [146].…”

Numerical minimization of AC losses in coaxial coated conductor cables

“…In optimization, the total losses are computed with fast evaluating circuit analysis model [13,14], which has been successfully applied to BSCCO cables [15][16][17] and to a short sample YBCO cable [18]. Here the losses of the individual tapes are computed based on Norris's strip model [19], which have aligned well with the recent measurements from the multilayer cables [9,20], whereas the widely used monoblock model [21] has shown to be too optimistic [9].…”

Current distribution analysis for high temperature superconducting cable considering hysteresis characteristics

“…In order to verify the correction of simplified Preisach model, the superconducting cable prototypes, which is simulated in [1], is employed. Table I lists the structural parameters of these prototypes.…”

“…The Preisach model has been used to describe the hysteresis in superconducting cable [1]. J. G. Zhu, et al proposed the circuit model for magnetic core by using simplified hysteresis Preisach model [2].…”

“…The circuit equations are solved by using Back-Eular method and Newton-Raphson iteration. In Section IV, comparison between the simulated results in [1] is conducted and discussed.…”