Coil Manufacturing Process Research Articles

Frequency response analysis of a toroidal field coil of the divertor tokamak test facility

The magnet system of the Divertor Tokamak Test (DTT) facility is mainly made up with superconducting coils. During the operation of the DTT machine, high voltages will appear across each Toroidal Field Coil (TFC) when fast current will ramp down; the reason why, a reliable electrical insulation is required for the operation of the TFC system. With the aim of checking the correct sizing and implementation of the electrical insulation, different DC and AC electrical tests will be performed during all the coil manufacturing process. Among these, the impedance spectrum test, or rather the complex impedance measurement over several decades of frequency range, can be used to analyze the frequency response of the coil. The variations of the resonance frequency (f0), during its electrical acceptance test, can be useful to make predictions about the detectability of internal failure conditions in a coil. This paper focuses on analysis of the frequency response of a TFC, using a numerical simulation approach. The goal is to assess the impedance spectrum of a TFC within a fixed frequency band by a frequency-dependent lumped network. Starting from the TFC layout, a WP with the casing has been modeled by a complex network of lumped parameters in Ansys 2021/R2 environment. The data (amplitude and phase angle vs frequency) obtained have been used to study the f0 variation during the different manufacturing stage of the WP. This model will be able to make predictions about the detectability of internal short-circuit in a TFC.

CFETR Nb3Sn coil in heat treatment deformation analysis and fixture designing

According to the research, it is found that the Hybrid Magnet coils, JT-60SA, ITER and CSMC coils are fixed by coils during heat treatment in order to prevent the coils deforming due to the release of residual stress. Since the penultimate process step of CFETR CSMC Nb3Sn coil manufacturing process is the final assembly of the coil, the theoretical value of the initial unilateral gap between Nb3Sn inner and outer coils is 27.4mm, and the theoretical value of the initial unilateral gap between Nb3Sn outer coil and NbTi coil is 50mm. This gap will be reduced in each process of coil manufacturing process. In order to successfully assemble the coil, it is of great significance to analyze and develop a set of tooling to reduce coil deformation in heat treatment process.

The CFETR CSMC Nb3Sn Coil Heat Treatment Process Research

The CSMC are major components of CFETR to generate the magnetic field for Simulating the Central Solenoid coil manufacturing process. The heat treatment process of Nb3Sn coil is an important process in the manufacturing process of CSMC. It is of great significance to design a reasonable heat treatment process for CSMC manufacturing. Several trials were performed to qualify and optimize the heat treatment procedure of the Central Solenoid coil. In the trials, 1) Designed the heat treatment process parameters of the coil; 2) Adjusted the heat treatment equipment and tested the process; 3) Evaluated the rationality of heat treatment process according to the Ic sample test results.Now, the heat treatment trials of Nb3Sn inner coil and outer coil have been finished. The inner coil have been described in this paper.

Coil Manufacturing Process of the First 1-m-Long Canted–Cosine–Theta (CCT) Model Magnet at PSI

At the Paul Scherrer Institute (PSI), the Canted-Cosine-Theta (CCT) magnet program aims at demonstrating that CCT technology is a viable candidate for the development of 16-T dipole magnets, required for future circular colliders. The first step in this direction is the implementation of a Nb3Sn 1-m-long, two-layer CCT single-aperture dipole, referred to as Canted Dipole One (CD1), which is designed to achieve a peak field in the bore of ~11 T. The in-house manufacturing and assembly of CD1 requires the infrastructure for a number of fabrication steps to be set up at PSI. In this paper, the authors review the coil manufacturing process of Nb3Sn CCT model magnets at PSI and describe the related commissioning phase.

Performance verification tests of JT-60SA CS model coil

As a final check of the coil manufacturing method of the JT-60 Super Advanced (JT-60SA) central solenoid (CS), we verified the performance of a CS model coil. The model coil comprised a quad-pancake wound with a Nb3Sn cable-in-conduit conductor. Measurements of the critical current, joint resistance, pressure drop, and magnetic field were conducted in the verification tests. In the critical-current measurement, the critical current of the model coil coincided with the estimation derived from a strain of −0.62% for the Nb3Sn strands. As a result, critical-current degradation caused by the coil manufacturing process was not observed. The results of the performance verification tests indicate that the model coil met the design requirements. Consequently, the manufacturing process of the JT-60SA CS was established.

Test Coil for the Development of a Compact 3 T ${\rm MgB}_{2}$ Magnet

An test coil was manufactured and tested as the first step in the development of a 3 T MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> magnet system. Due to the fact that MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has a higher critical temperature, replacing conventional NbTi superconductor with MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , higher temperature operation will be possible. It will make the cryogenic design much simpler and less expensive. Furthermore, operating the magnet at higher temperature results in larger heat capacity of the materials and surrounding structures. Higher heat capacity, therefore, results in increased thermal stability of the magnet against quench initiation. The 3 T magnet design consists of several coils. One of the center coils was manufactured for testing the performance at higher temperatures. The test coil was conduction cooled and the quench performance of the coil was good, which means there were no critical issues during the coil manufacturing process. However, AC loss heating, as well as a small resistance of the coil was found, both of which might result from wire design, manufacture, and quality.

Fault diagnosis and comparing risk for the steel coil manufacturing process using statistical models for binary data

Advanced statistical models can help industry to design more economical and rational investment plans. Fault detection and diagnosis is an important problem in continuous hot dip galvanizing. Increasingly stringent quality requirements in the automotive industry also require ongoing efforts in process control to make processes more robust. Robust methods for estimating the quality of galvanized steel coils are an important tool for the comprehensive monitoring of the performance of the manufacturing process. This study applies different statistical regression models: generalized linear models, generalized additive models and classification trees to estimate the quality of galvanized steel coils on the basis of short time histories. The data, consisting of 48 galvanized steel coils, was divided into sets of conforming and nonconforming coils. Five variables were selected for monitoring the process: steel strip velocity and four bath temperatures.The present paper reports a comparative evaluation of statistical models for binary data using Receiver Operating Characteristic (ROC) curves. A ROC curve is a graph or a technique for visualizing, organizing and selecting classifiers based on their performance. The purpose of this paper is to examine their use in research to obtain the best model to predict defective steel coil probability. In relation to the work of other authors who only propose goodness of fit statistics, we should highlight one distinctive feature of the methodology presented here, which is the possibility of comparing the different models with ROC graphs which are based on model classification performance. Finally, the results are validated by bootstrap procedures.

Coil Development using YBCO Tape Coated Conductor for Power Applications

Each superconducting coil manufacturing process using YBCO tape coated conductor was evaluated, and double pancake type copper stabilized coils were verified, in order to develop base technologies of a YBCO coil for power applications. Cost of YBCO tape including a stabilization process needs to be low in order for it to be a practical use wire for power application coils. Conduction cooling is also needed below the 50K temperature range, which is optimal for high magnetic field coils using YBCO tape. Therefore, we developed technology for each process for manufacturing of a conduction cooling type coil. Techniques for winding, stabilization, electrode formation, and impregnation were developed, considering YBCO tape configuration and a conduction cooling method. Several wire coils were then manufactured and verified using a conduction cooling system, and the high performances of thermal stability, low electrical joint resistance, etc. were achieved without degradation.

An Innovating Insulation for&lt;tex&gt;$rm Nb_3rm Sn$&lt;/tex&gt;Wind &amp; React Coils: Electrical Tests

If Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn is the best superconductor candidate for the realization of high field magnets (for 10-11 Tesla), its implementation remains delicate because of the great brittleness of material after the heat treatment necessary for the formation of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn compounds. The conventional insulation for Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Wind & React coils requires performing, after the heat treatment, a vacuum resin impregnation, which adds to the cost and raises failure risk. We have proposed a one-step innovating ceramic insulation deposited directly on the un-reacted cable. After the heat treatment, we obtain a coil having a mechanical cohesion, while maintaining a proper conductor positioning and a suitable electric insulation. We have shown that using this insulation in a coil manufacturing process does not affect the electrical properties of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires. A solenoid of small dimensions (9 * 20 turns on an internal diameter of 22 mm) has produced a magnetic field of 3.8 T at 740 A. It was tested with success in high external magnetic fields: the quench limits have been imposed by the strand and the insulation was not damaged

Mechanical performance of magnet insulation materials fabricated by the “Insulate-Wind-and-React” technique

Superconducting magnet coils are usually fabricated according to the “Wind-React-Insulate-and-Transfer” technique. However, the alternative “Insulate-Wind-and-React” technique could simplify the coil manufacturing process considerably. An insulation system designed for this process has been investigated. It consists of a R-glass fiber reinforcement heat treated at 650 °C and impregnated afterwards with epoxy. For the mechanical material characterization, tensile, short-beam shear (SBS) and tension–tension fatigue tests were employed at 77 K. In addition, half of the SBS samples were reactor irradiated to a neutron fluence of 1 × 10 22 m −2 ( E > 0.1 MeV) to check for radiation induced material degradation.

Manufacture, assembly and QA of the ITER toroidal field Model Coil

The conceptual design of the ITER TF Model Coil (TFMC) was produced by the European Home Team based on the ITER TF coil design. The test configuration in the TOSKA facility of FZK comprises the TFMC coupled with the existing European LCT coil by an intercoil structure (ICS). The elements of the TFMC are being constructed by European industry under the supervision of ITER European Home Team and are currently nearing completion. The primary objectives of the TFMC program are to gain experience of all aspects of the coil manufacturing process (including QA methods) and to establish realistic manufacturing tolerances for the actual ITER TF coils. At the current state of the project many of these objectives have already been achieved. The various technical problems encountered during engineering design and manufacture have been solved and have produced very useful information which can be applied in the ITER procurement documents for the TF coil system. This paper presents a description of the manufacturing process and related QA procedures.