This paper presents numerical study on magnetization characteristics of conductor on round core (CORC) cable. Numerical models introduced in this paper are based on finite-element method (FEM) with simplified structure, optimized assumptions and settings. Magnetization performance of CORC cables is represented by both full coupled model and isolated model. These numerical models are verified by experiments on CORC cables made of commercial HTS tapes. On basis of this, two topics are discussed in this paper: one is the magnetic shielding effect of superconducting layers in CORC cables; the other one is the end effect of magnetization loss in short CORC cables. Conclusions obtained in this paper will be helpful to understand the working mechanism of CORC cable and also useful in design of large-scale magnets based on CORC cables.

High-temperature superconductors from the RE BCO ( RE = rare earth) family have attained industrial production and their performance is continuously being enhanced. However, cabling technology for high-current (kA range) cables for magnet technology is still challenging and there are only few cable concepts available (CORC ^® , Roebel cable, twisted stack cable). Each of them exhibits different characteristics. In this paper we experimentally investigate CORC ^® cable produced in-house utilizing a copper tube former. Such a former offers a central cooling channel for partial or complete cable cooling by forced flow of coolant. We focus mainly on AC loss due to transporting AC current, an external applied AC magnetic field and their simultaneous action. In the case of transporting AC current we found indications that a large part of the total loss has its origin in eddy currents due to an axial magnetic field. For the investigation of magnetization AC loss, we prepared several samples with different configurations. In this case we found direct evidence for increasing AC loss due to losses in the metallic former. However, we also found that at low field amplitudes the magnetization AC loss of the complete cable is lower than the loss in the bare former. This is caused by shielding of the magnetic field by a superconductor, which was also confirmed by numerical simulations.

Alternative concept for winding of coils from high-temperature superconducting tapes has been investigated. Conductor-On-Round-Tube (CORT) conductors with tapes helically wound on a metallic tube have been manufactured and used to wind single layer coils with the bore diameters between 116 and 325 mm wound and tested in the dc regime. Results were analyzed with the help of numerical calculations considering the critical current density dependence on magnetic field derived from the short sample measurement. We have also modified the standard approach by including the fluctuations of critical current along the tape length into the calculations. Results have shown that the uniformity of critical current is essential for achieving predictable cable and coil performance.