Abstract
The conductor on round core (CORC) cable wound with second-generation high-temperature superconducting (HTS) tapes is a promising cable candidate with superiority in current capacity and mechanical strength. The composing superconductors and the former are tightly assembled, resulting in a strong electro-magnetic interaction between them. Correspondingly, the AC loss is influenced by the cable structure. In this paper, a 3D finite-element model of the CORC cable is first built, and it includes the complex geometry, the angular dependence of critical current and the periodic settings. The modelling is verified by the measurements conducted for the transport loss of a two-layer CORC cable. Subsequently, the simulated results show that the primary transport loss shifts from the former to the superconductors as the current increases. Meanwhile, the loss exhibited in the outer layer is larger than that of the inner layer, which is caused by the shielding effect among layers and the former. This also leads to the current inhomogeneity in CORC cables. In contrast with the two-layer case, the simulated single-layer structure indicates stronger frequency dependence because the eddy current loss in the copper former is always dominant without the cancellation of the opposite-wound layers. The core eddy current of the single structure is denser on the outer surface. Finally, the AC transport losses among a straight HTS tape, a two-layer cable and a single-layer cable are compared. The two-layer structure is confirmed to minimise the loss, meaning an even-numbered arrangement makes better use of the cable space and superconducting materials. Having illustrated the electro-magnetic behaviour inside the CORC cable, this work is an essential reference for the structure design of CORC cables.
Highlights
Second-generation high-temperature superconducting (HTS) tapes, known as REBCO coated conductors (REBCO-CCs), have advantages of high critical magnetic field and strong current-carrying capacity
In order to validate the developed model, the measurement on the AC transport loss of the sample shown in Fig. 1 is carried out
The transport loss can be calculated by electrical method, which is expressed as the following, Q = Irms ⋅ Vrms f where Irms is the RMS value of the AC current flowing through the cable, and Vrms is the RMS value of the voltage measured on the sample; f is the frequency of the AC current
Summary
Second-generation high-temperature superconducting (HTS) tapes, known as REBCO coated conductors (REBCO-CCs), have advantages of high critical magnetic field and strong current-carrying capacity. It is not practical to gain a high magnetic field or high transport current with a single HTS tape. Wang et al [4] and Sheng et al [5] investigated the cable’s magnetisation in TA formulation and H formulation, respectively. They explored the effects of magnetic shielding, winding direction and multi-layer layout. Šouc et al [6] and Vojenčiak et al [7] found that CORC cables wound with striated superconducting tapes could reduce the magnetisation loss at a high magnetic field, and the filaments in superconductors proved to be useful.
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