CORC Cables Research Articles

Effect of different core diameters on the current-carrying performance of CORC cables with REBCO multi-filamentary tapes

The second generation of high temperature superconductivity (HTS) is one of the candidate materials for future superconducting cables (such as CORC), CICC conductors and high field magnets due to its high current carrying performance and excellent mechanical strength. Currently, it has been demonstrated that the utilization of REBCO multi-filamentary tapes in the fabrication of CORC cables can further reduce AC losses. This study involved the preparation of various types of REBCO multi-filamentary tapes through reel-to-reel ultraviolet picosecond laser cutting technology, as well as the manual winding of multiple single-layer CORC cable samples. This work focused on the impact of core diameter on the current-carrying performance of REBCO multi-filamentary tapes under self-field conditions at 77 K. The results indicate that the critical current (IC) of REBCO multi-filamentary tapes decreases as the core diameter decreases. Furthermore, the decrease in IC becomes more significant with an increasing number of cores. When the cable core diameter is 4.6 mm, the critical current of the 3-filament tape is 180.49 A with an n-value of 24.84, which is only a 3.1 % recession compared to the critical current of the commercialized tape. The conclusion of this paper will provide a certain data reference for the subsequent selection of CORC cable core size prepared by REBCO multi-filamentary tapes.

Mechanical Performance Tests of Customized CORC Cable

Mechanical Performance Tests of Customized CORC Cable

CORC Cables: Numerical Characterization of the Critical Current After Bending

CORC Cables: Numerical Characterization of the Critical Current After Bending

An Electromagnetic-Thermal Modeling Method for the Joint Resistance of the CORC Cable

An Electromagnetic-Thermal Modeling Method for the Joint Resistance of the CORC Cable

Experimental and Numerical Study on the Transport AC Loss of Bent CORC Cables

Experimental and Numerical Study on the Transport AC Loss of Bent CORC Cables

Modeling of contact resistivity and simplification of 3D homogenization strategy for the H formulation

The finite element method (FEM) provides a powerful support for the calculations of superconducting electromagnetic responses. It enables the analysis of large-scale high-temperature superconducting (HTS) systems by the popular H formulation. Nonetheless, modeling of contact resistivity in three-dimensional (3D) FEM is still a matter of interest. The difficulty stems from the large aspect ratio of the contact layer in numerical modeling. Nowadays, an available solution is to model the contact layer with zero thickness but requires the discontinuity conditions of the magnetic field. In this paper, the energy variational method is utilized to incorporate the contribution of contact resistivity into the H formulation. From the perspective of energy transfer, the contact resistivity is related to the energy dissipation of the radial current flowing through the contact interface. In terms of applications, this method can be employed to calculate the charging delay of no-insulation coils and the current sharing behaviors of CORC cables. One advantage of this model is that the magnetic field is continuous and hence can be easily implemented in FEM. Additionally, it requires fewer degrees of freedom and hence presents advantages in computational efficiency. Moreover, this method can be employed to simplify the 3D H homogeneous model for insulated coils. The above discussions demonstrate that the proposed model is a promising tool for the modeling of contact resistivity.

AC Loss Modeling of a CORC Cable via an Analytical Equation and Finite Elements

AC Loss Modeling of a CORC Cable via an Analytical Equation and Finite Elements

Quench Performance of the HTS Insert Solenoid With REBCO CORC Cable at 4.2 K 18.5 T Background Magnetic Field

Quench Performance of the HTS Insert Solenoid With REBCO CORC Cable at 4.2 K 18.5 T Background Magnetic Field

Calculation and Measurement of Transport AC Loss of ReBCO CORC Cables for Electric Aircraft

Calculation and Measurement of Transport AC Loss of <i>Re</i>BCO CORC Cables for Electric Aircraft

Influence of HTS tape arrangement on the transverse compression performance of copper former CORC cables

CORC cables are subject to large transverse compression electromagnetic forces in fusion projects. Unfortunately, the electromagnetic force exceeding its critical transverse compression load will cause an irreversible decrease in its critical current. Therefore, it is particularly important to enhance the critical transverse compression load to ensure that the critical current does not decrease during operation. The winding method of high temperature superconducting (HTS) tape on the central former is variable. So the experimental study on how to increase the critical transverse compression load of CORC cable by changing the winding method of HTS tape is carried out in this paper. Firstly, the influence law of parameters of the number of HTS tapes per layer and the number of HTS tape layers on their transverse compression performance are analysed independently. The results indicate that increasing the number of HTS tapes per layer and the number of HTS tape layers can both improve the transverse compression performance of CORC cables. Whereas, in the case of a cable with a certain critical current demand (the same total number of HTS tapes), increasing the number of HTS tape layers necessarily reduces the number of HTS tapes per layer. Therefore, in order to compare the degree of influence of the above two parameters, we conducted transverse compression experiments on multiple groups of CORC cables with different winding methods (more layers with few tapes per layer or few layers with more tapes per layer) under the same critical current demand. The results show that under the same critical current demand, choosing the winding method that reduces the number of HTS tape layers and increases the number HTS tapes per layer can effectively improve the transverse compression performance of CORC cables. A 3D multilayer CORC cable transverse compression finite element model is also established to explain the inherent reasons for the differences in transverse compression performance of CORC cables under different HTS tape winding methods.

Experimental research on the influence of HTS tape width and former type on the transverse compression performance of CORC cables

The huge transverse Lorentz force experienced by CORC cable during the operation of fusion projects may cause irreversible degradation of its current-carrying capacity. Therefore, it is particularly important to study the influence of cable parameters on their transverse compression performance, and use these influence laws to adjust cable parameters to improve the critical value of transverse compression load that CORC cables can withstand. Solid copper bar former CORC cables with a former diameter of 5.57 mm are produced using HTS (high temperature superconducting) tapes (manufactured by Shanghai Superconductor) of 4 mm and 5 mm width respectively. The experimental results show that the CORC cable wound with 5 mm wide HTS tape has a greater critical transverse compression load than the cable wound with 4 mm wide HTS tape. This indicates that using wider HTS tapes to wind CORC cables can effectively improve their transverse compression performance. A solid copper bar former CORC cable and a stainless steel spiral tube former CORC cable are also produced. Through transverse compression experiments, it is found that the critical transverse compression load of the solid copper bar former and the stainless steel spiral tube former CORC cable are 130 kN/m and 89 kN/m, respectively. This indicates that the solid copper bar former CORC cable has better transverse compression performance. In addition, we also compared the influences of flat and arc pressure blocks on the transverse compression performance of CORC cables, and this experimental results provided a basis for the selection of the bobbin structure when using CORC cables to make coils.

Performance study of REBCO multi-filament tapes/CORC cables prepared by reel-to-reel mechanical incision

REBCO high-temperature superconductor (HTS) has widely used in high magnetic field applications, because of the excellent critical current properties and high critical temperature. However, REBCO tape has an extremely large width-to-thickness ratio (typically in the range of 1000–10000) to cause too high power dissipation in the applications. In order to reduce the shielding current effect and AC loss generated during the application of REBCO HTS tapes, a roll-to-roll mechanical incision device was developed for the preparation of REBCO multi-filaments tapes. The microscopic morphology, critical current IC, and hysteresis loss of the tapes before and after incision were comparatively characterized using optical microscope, standard four-probe method, and physical property measurement system (PPMS) and other equipment and methods. The results show that the developed device prepares multi-filaments tapes with incision grooves depths of ∼ 30 μm and grooves widths of ∼ 20 μm on the superconducting layer, and the hysteresis loss of the 3-filaments is reduced by up to 48.6 % compared to that of the non-striated tapes under different temperature conditions. In addition, the IC of the short samples of the 3-filaments tapes was reduced by ∼ 18 % compared with that of the non-striated tapes under 77 K and self-field test conditions, whereas the samples of the 3-filaments tapes and the non-striated tapes were hand-wound respectively onto a metal core with a diameter of 5.25 mm to make a single-layer CORC cable, and there was no significant reduction in the IC of either of them.

The Impacts of Winding Direction on the Electromagnetic Characteristics of CORC Cables

The Impacts of Winding Direction on the Electromagnetic Characteristics of CORC Cables

Strain analysis of the superconductor REBCO tape of CORC cables under winding, bending and twist deformations

Strain analysis of the superconductor REBCO tape of CORC cables under winding, bending and twist deformations

Numerical calculations of high temperature superconductors with the J-A formulation

One of the main challenges in superconductivity modeling stems from the strong nonlinearity of the E-J power law relationship. To overcome this difficulty, various numerical models have been developed by the superconductivity community, such as the H formulation and the T-A formulation. These models are implemented based on different state variables in Maxwell’s equations and have the advantage of efficiency and versatility. In this study, a finite element model based on the J-A formulation is further developed to enhance its accuracy and versatility. The discontinuous Lagrange shape function is employed in the J formulation to stabilize the numerical results. Meanwhile, the Lagrange multiplier method is applied to impose the transport current on the superconductors. In terms of applications, the J-A formulation can efficiently simulate the electromagnetic responses not only of superconducting films but also of superconducting bulks. Moreover, homogeneous and multi-scale strategies are introduced to simplify the model and reduce the computation cost, allowing efficient simulation of large-scale HTS systems. Finally, the three-dimensional (3D) J-A formulation is proposed to incorporate the 3D structure of HTS systems, examples including the CORC cables as well as the racetrack coils. These results reveal that the J-A formulation is an efficient and versatile numerical method for calculating the electromagnetic behavior of high temperature superconductors.

Canted Cosine Theta Dipole Magnet Wound Using REBCO CORC Cables–The Effect of Magnetization on Magnetic Field Quality

This paper presents the results of FEM analysis of the effect of REBCO CORC cable magnetization on the field quality of a canted cosine theta (CCT) dipole magnet. The magnetic properties of the CORC cable were the results of our measurements of its <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> ) curves at 4.2 K and magnetic fields up to 8 T. This magnetization data was used to calculate the field error for a CCT experimental magnet developed by LBNL. The results of analysis and experiment were compared. To make the computation less “expensive”, we modelled only a section of 10 or 8 turns of the magnet central part and calculated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b₁</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b₃</i> fields on a circle 2/3 of the innermost layer center line. Calculated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b₃</i> fields were compared with experimentally obtained values on the dipole operating in self-field mode. Reasonable agreement of the numerical and experiment values was achieved. The work continued with calculating of field errors for a 7 double layer version of that design.

Simulation for the Fault Current Limiting Operation of REBCO CORC Superconducting Cables With Different Core Materials

With high power density and low loss, CORC superconducting cables composed of RE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> Ba <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> Cu <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula> O <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{7-\delta }$</tex-math></inline-formula> (REBCO)-coated conductors are of great interest for power transmission applications. They can also effectively be designed to serve as fault current limiters, thanks to their sharp superconducting-to-normal transition. Coupled electromagnetic-thermal finite-element simulations implemented in COMSOL Multiphysics were developed and validated against the published results for the fault current limiting (FCL) performance of two CORC cables of REBCO-coasted conductors wound on either copper or stainless steel cores. For improved accuracy, temperature dependencies of electrical and thermal properties of all component materials were considered in the simulations. The simulations were performed in the cross sections of the cables for every individual layer of each REBCO tape to deliver comprehensive understanding of the evolution of the current distribution and temperature rise in those layers. The studies can suggest approaches to optimize cable design for FCL applications by assessing the role of individual components. In the article, possible computational errors, challenges, and improvements are also discussed.

Simulation of Current Distribution and Energy Losses in a Superconducting CORC Cable

Simulation of Current Distribution and Energy Losses in a Superconducting CORC Cable

Influence of Mechanical Deformations of HTSC Tapes on the Current-Carrying Characteristics in the Creation of a CORC Cable

Influence of Mechanical Deformations of HTSC Tapes on the Current-Carrying Characteristics in the Creation of a CORC Cable

Investigating the effect of transverse compressive loads on the electromagnetic performance of superconducting CORC® cables

High-temperature superconductor (Re)Ba2Cu3O x (ReBCO) conductor on round core cable (CORC®) has a large current carrying capacity for high field magnets. Lorentz forces acting on CORC conductors, cause a reduction of the critical current, or even permanent degradation of their performance when exceeding critical values. Transverse compressive stress is one of the principal mechanical stresses when CORC cables are bundled to cable-in-conduit conductors (CICC) conductors capable of operating at currents up to 100 kA in magnetic fields of up to 20 T. In this research, a mechanical-electromagnetic model is developed to study the effect of transverse compressive loads on the electromagnetic performance of CORC cables. A mechanical transverse load on the cable is implemented to simulate the electromagnetic force. A comparison of numerical simulations with experiments for a three-layer CORC cable is first performed to validate the model’s reliability, with particular attention to critical current reduction during the transverse compression process. A novel feature of this paper is that the model developed can analyze both mechanical response under transverse compressive loads and electromagnetic performance under applied AC magnetic fields with low amplitudes. On this basis, the model investigates the effects of winding parameters on the axial strain and critical current reduction of the ReBCO layer in a single-layer CORC cable. The numerical analysis shows that increasing the winding angle can reduce the axial strain and critical current reduction of the ReBCO layer in the contact area. Subsequently, a detailed comparative study is carried out studying the axial strain of the ReBCO layer in the non-contact area with and without taking the winding core into account. In addition, a sudden increase in the magnetization loss is explained when the transverse compressive load reaches a certain level. Finally, a six-layer CORC cable’s electromagnetic analysis is performed, and each tape layer’s critical current reduction is investigated and discussed. The comparison of magnetization loss and current density between six- and single-layer CORC cables in the no-strain case is also given. This finite element model can guide optimizing a cable design for specific application conditions.