• Progress in Superconductivity and Cryogenics
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• v.23 no.2
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• pp.24-27
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• 2021

This paper presents a design methodology of high-temperature superconducting (HTS) magnets. The magnet consists of several double pancake coils with a variety of wire width. This technique, named Multi-Width, is well known to make efficient use of the superconducting wire. It is common for design of high-temperature superconducting magnets to not only reduce wire consumption used, but also consider the homogeneity of the magnetic field. In this paper, we study a design method that efficiently reduces wire usage while considering magnetic field homogeneity. The design is carried out by calculating the critical current and the critical magnetic field according to the configuration of arranging the thickness of the wire to determine the number of windings. The width of wire comprising the magnet was set to 4 - 12 mm, and the number of double pancake coils was set to an even number to consist of top-down symmetry. To verify the validity of the design, we compared the progress of the design code with a complete enumeration survey. As a case study, we designed a magnet that generates a central magnetic field of 3 T or more in a 240 mm bore in diameter. Optimality can be evaluated by weighing wire consumption and field homogeneity according to the magnet's use or user preference.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.6
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• pp.57-62
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• 2011

This paper proposed a method which is the three types of magnet model for improving field inhomogeneity of superconducting magnet. The length of coil wire was compared for the optimized current pattern using minimum power methods and field inhomogeneity under the specific simulation condition in case of same magnet field strength about each magnet type field inhomogeneity. Length of wire and field inhomogeneity were compared under the same condition(18 target points, 20cm DSV). According to the simulation results, the smaller target points can reduce the wire length but it can not improve the field inhomogeneity. Length of wire and low field inhomogeneity can not improve in same time. However, small DSV and reducing target points can overcome the these problem. And to conclude, if it processes shimming as reducing target points in case of magnet model which is open to space, about the size of same imaging region it needs a lot of current values(or the length of wire) and decreases field homogeneity but it is useful to get small ROI.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.1
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• pp.1-4
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• 2003

This paper presents an attempt to develop probabilistic multistress life models to evaluate the lifetime characteristics of epoxy-encapsulated magnet wire with heavy build polyurethane enamel. A set of accelerated life tests were conducted over a wide range of pulsating voltages, temperatures, and frequencies. Samples of fine gauge twisted pairs of the encapsulated magnet wire were tested us-ing a pulse endurance dielectric test system. An electrical-thermal lifetime function was combined with the Weibull distribution of lifetimes. The parameters of the combined Weibull-electrical-thermal model were estimated using maximum likelihood estimation. Likewise, a generalized electrical-thermal-frequency life model was also developed. The parameters of this new model were estimated using multiple linear regression technique. It was found in this paper that lifetime estimates of the two proposed probabilistic multistress life models are good enough. This suggests the suitability of using the general electrical-thermal-frequency model to estimate the lifetime of the encapsulated magnet wire over a wide range of voltages, temperatures and pulsating frequencies.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1798-1800
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• 1997

Object of this paper is to find the best shape of cylinder, flowing velocity of gas and state of pole with the cylinder wire magnet type. Also it is to analysis phenomena arising in the cylinder. So that general program FLUX2D has used for magnetic and electric field analysis at the cylinder wire magnet type. General program PHOENICS has used for cold or hot gases flowing analysis at the cylinder wire type with magnet.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.210-211
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• 2006

This study presents the technology and application of hybrid insulation film for electric magnet wire. In order to make the high efficient motor with high space factor, it is necessary to develop a self-lubrication heat-resistant insulation film that can be used when the space factor 70% or more. A key to achieving high windability is to increase the lubricity and bonding strength of vanish, which for a magnet wire generally determines the mechanical scratches characteristics. Effective ways to reduce scratches include improving insulation film prepared by organic and inorganic hybrid synthesis methods.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1134-1139
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• 2011

When the aspect ratio of a magnet varies, the magnetic field in the magnet also varies. The critical current of a tape-shaped HTS wire varies with the direction and magnitude of applied magnetic field. Consequently when the aspect ration of a HTS magnet varies, the critical current of a HTS magnet varies. This paper shows the relation between the aspect ratio of a magnet and the energy and inductance of a HTS magnet. The critical current is also shown at various aspect ratio of the magnet. The length of the HTS wire, inner diameter of the magnet, and number of pancake are chosen to be variables which varies the shape of the magnet. For a HTS magnet consisting of pancake windings, calculation results show the number of pancake windings are the prime factor which varied the energy and inductance of the magnet. The inner diameter of the magnet varies the energy and inductance of the magnet a little.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.10
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• pp.641-646
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• 2016

Coil specimen was prepared by coating a copper wire with two varnish thin layers: the first was polyamideimide (PAI)/nanosilica (5 wt%) varnish and the second was anti-corona PAI/nanosilica (15 wt%) varnish. Insulation breakdown voltage was investigated under inverter surge condition at $20^{\circ}C$, $70^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$, $250^{\circ}C$, respectively. The insulation lifetime of the two layered coil was tens of times longer than that of original PAI coil. And the insulation lifetime decreased with increasing ambient temperature because there was weak binding strength between copper and varnish layer.

• Progress in Superconductivity and Cryogenics
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• v.11 no.4
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• pp.33-36
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• 2009

An air gap between the pancake windings was provided in this paper to increase the central magnetic field of a high temperature superconducting (HTS) magnet consisting of pancake windings. Unlike the LTS magnet, providing an air gap between the pancake windings increases the central magnetic field of a HTS magnet. Furthermore, the uniformity of the magnetic field near the center of the magnet increased because the pancake windings spread out in wider area. Effects of the air gap on the central magnetic field of an HTS magnet was described in this paper, Calculation of the critical current was carried out by using E-J relation of the HTS wire and the optimization technique was adopted to obtain the appropriate critical current which could maximize the central magnetic field. Pancake windings with BSCCO-2223 HTS wire were wound on glass epoxy bobbin. 6 double pancake windings with 200 turns were used to construct a HTS magnet. Characteristics of the HTS magnet including the central magnetic field and the uniformity of the magnetic field were measured and compared with the results of calculation.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.24-27
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• 2023

Until now, many research activities have been conducted to commercialize high-temperature superconducting (HTS) wires for electric applications. Most of all researchers have focused on enhancing the piece length, critical current density, mechanical strength, and throughput of HTS wires. Recently, HTS magnet for generating high magnetic field shows degraded performance due to the deformation of HTS wire by high electro-magnetic force. The deformation can be derived from widthwise thickness non-uniformity of HTS wire mainly caused by wet processes such as electro-polishing of metal substrate and electro-plating of copper. Gradient sputtering process is designed to improve the thickness uniformity of HTS wire along the width direction. Copper stabilizing layer is deposited on HTS wire covered with specially designed mask. In order to evaluate the thickness uniformity of HTS wire after gradient sputtering process, the thickness distribution across the width is measured by using the optical microscope. The results show that the gradient deposition process is an effective method for improving the thickness uniformity of HTS wire.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.681-682
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• 2006

This paper deals with the preliminary study on the HTSC levitation magnet for MAGLEV operating in persistent current mode (PCM). The high temperature superconducting (HTSC) levitation magnet consists of two single-pancake type coils wound with Bi-2223 wire and a persistent current switch (PCS). The levitation magnet was designed by using 3-D finite element analysis. The suspension system for high-speed electrodynamic suspension (EDS) maglev should operated in persistent current mode. It is important to develop a technology to minimize the joint resistance of splice between two HTSC wires. The PCS was observed with respect to various magnitude of charging current. Based on these results, the levitation system using HTSC wire will be further studied.