13 research outputs found
Self-consistent Modeling of the of HTS Devices: How Accurate do Models Really Need to Be?
Numerical models for computing the effective critical current of devices made
of HTS tapes require the knowledge of the Jc(B,theta) dependence, i.e. of the
way the critical current density Jc depends on the magnetic flux density B and
its orientation theta with respect to the tape. In this paper we present a
numerical model based on the critical state with angular field dependence of Jc
to extract the Jc(B,theta) relation from experimental data. The model takes
into account the self-field created by the tape, which gives an important
contribution when the field applied in the experiments is low. The same model
can also be used to compute the effective critical current of devices composed
of electromagnetically interacting tapes. Three examples are considered here:
two differently current rated Roebel cables composed of REBCO coated conductors
and a power cable prototype composed of Bi-2223 tapes. The critical currents
computed with the numerical model show good agreement with the measured ones.
The simulations reveal also that several parameter sets in the Jc(B,theta) give
an equally good representation of the experimental characterization of the
tapes and that the measured Ic values of cables are subjected to the influence
of experimental conditions, such as Ic degradation due to the manufacturing and
assembling process and non-uniformity of the tape properties. These two aspects
make the determination of a very precise Jc(B,theta) expression probably
unnecessary, as long as that expression is able to reproduce the main features
of the angular dependence. The easiness of use of this model, which can be
straightforwardly implemented in finite-element programs able to solve static
electromagnetic problems, is very attractive both for researchers and devices
manufactures who want to characterize superconducting tapes and calculate the
effective critical current of superconducting devices
Numerical Study on Magnetization Characteristics of Superconducting Conductor on Round Core Cables
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
Design and Testing of Coils Wound Using the Conductor-On-Round-Tube (CORT) Cable
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