• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1035-1038
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• 2007

We designed and manufactured a 1.8T high temperature superconducting(HTS) insert coil for a NMR magnet operated at 4.2 K. Suitable HTS superconductor and HTS coil were carefully designed and developed. We have selected multi-filamentary Bi2223 conductor fabricated by American Superconductor Corporation(AMSC). The selected conductor consists of Bi2223 filaments of 55, silver stabilizer and stainless steel reinforcement tapes. Therefore, it shows good hoop strength as well as compression tolerance. The conductor has a tape cross-section of 0.31mm x 4.8mm. the Bi2223 conductor shows large anisotropy of critical current. The critical current of conductor in magnetic field parallel to the flat surface are much higher than that in magnetic field perpendicular. The HTS coil has an inner diameter of 78 mm, an outer diameter of 127 mm and a coil length of 600 mm. In this paper, the detailed design, fabrication and test results on the HTS insert coil are presented.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.284-287
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• 2003

Quench characteristics of HTS cable conductor due to external magnetic field were investigated. Firstly, the influence of critical characteristics of HTS tape on locally applied magnetic field was examined. Secondly, critical current of HTS tapes, which are wound on surface of former, were measured respectively, before the experiment for quench characteristics, Finally, 50mT and 100mT were applied to HTS cable conductor and quench characteristics were investigated through V-I curves. As the results, same as the result of HTS tape, HTS cable conductor showed strong dependence on external magnetic field with direction and magnitude.

• Progress in Superconductivity and Cryogenics
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• v.10 no.3
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• pp.36-42
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• 2008

The superconducting motor shows several advantages such as smaller size and higher efficiency against conventional motor especially utilized in ship propulsion application. However, this size reduction merit appears in large capacity more than several MW. We are going to develop a 5MW class synchronous motor with rotating High-Temperature Superconducting (HTS) coil. that is aimed to be utilized for ship propulsion so it has very low-speed, The ship propulsion motor must generate very high electromagnetic torque instead of low-speed. Therefore. the rotor (field) coils need very large magnetic flux that results in large amount of expensive HTS conductor for the field coil. In this paper a 5MW HTS motor for ship propulsion is considered to be designed with construction cost reduced via HTS field coil cost reduction because HTS conductor cost is critical factor in the construction cost of HTS motor. In order to reduce the HTS conductor amount. iron-cored rotor types are considered. so several cases with iron-core are compared one another and with an air-core case.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.27-34
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• 2000

HTS wires processed by PIT method are now available for magnet applications. But, those wires can not be used over 40 K due to weak link. This leads to necessity of development of coated conductor which can retain high $J_c$ at high field in liquid nitrogen. In this paper, various technical issues and the R&D status for both PIT wires and coated conductor were discussed. The difference of coated conductor's processes were also investigated and summarized. Various requirements for a design of HTS magnets were discussed. Anisostropic $J_c$ property with respect to magnetic field was considered to determine the coil's critical current. Low n value is a critical parameter to degrade a field stability with respect to time for a persistent mode HTS magnet. The relation between the margin of operation current and n value was investigated. Prototype HTS magnets with PIT wires are being developed for various applications such as crystal growth, MRI, magnetic separator and etc. HTS magnets will come into wide use in various fields of industries if the HTS wires with a low performance cost is developed.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.32-36
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• 2008

An HTS conductor with parallel HTS tapes is essential for a large power HTS device to flow a large current. One of the most important factor for this conductor is a current distribution. Non-uniform current distribution in parallel tapes makes the critical current of the conductor low and the AC losses high. In this paper we proposed a non-contact method which measured each current in parallel tapes by using an array of Hall sensors. A matrix can be derived from this array for calibration. The current distributions of 4 and 6 parallel tapes were measured.

• Progress in Superconductivity
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• v.5 no.2
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• pp.144-148
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• 2004

Uniform current distribution among conductor layers in HTS cables using IPTs (inter-phase transformers) was investigated. Conventional methods for current distribution, in which resistors are inserted to conductor layers, causes additional loss. In contrast, IPTs, which use magnetic coupling, make it possible that the current in parallel circuits is distributed uniformly with any load, and minimize the loss. In this study, IPTs were designed and fabricated for examination of uniform current distribution in the conductor layers of HTS cables. The ITP was designed through calculation of its impedance that can cancel the inductance of the conduction layers. The experimental setup consisted of four IPTs and four inductors that simulate the conductor layer inductance. Each layer was designed to feed 10 A. We examined the behavior of current distribution with IPTs for various layer inductances.

• Progress in Superconductivity and Cryogenics
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• v.14 no.2
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• pp.20-23
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• 2012

With continuous development of the 2nd generation HTS conductor, the critical current of the conductor is also increasing. However, many applications require more than 2 conductors in parallel to transport large current. Applications such as HTS power cables and some HTS current leads usually need much larger transport current than that provided by a single conductor and they require more than several tens of HTS conductors. In the case of parallel connection of multiple HTS conductors, the current distribution depends on the contact resistance of each conductor at the terminals for DC operation. The non-uniform distribution of the terminal resistances results in a non-uniform distribution of the current. The resultant current non-uniformity affects on the measurement of the I-V curve and the thermal performance of the multiple conductors. This paper describes the I-V curves obtained from multiply connected HTS conductors with different terminal contact resistances to investigate the relationship between the distorted I-V curve and heat generation.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.52-56
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• 2008

According to the improvement of HTS conductor, HTS tapes which have the high current capacity have been recently researched in several nations. For large power application, AC loss is the most important issue in the development of AC superconducting power devices because it is closely related to the system operation efficiency. In 1st generation wire of HTS conductor, BSCCO, AC loss is too large to use for power application. Also, It is well known in recently years that YBCO CC, the 2nd generation wire, has also too much AC loss to apply to AC power devices. There are many trials to develop the new HTS wire having the low AC loss around the world. In this research, we present the measurment result of magnetization losses in SmBCO coated conductors. We measured the magnetization loss generated by perpendicularly exposed external magnetic field and compared with the analytic value of the strip model. Also, we presented the results compared with measured magnetization loss of an YBCO coated conductor.

• Progress in Superconductivity and Cryogenics
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• v.12 no.4
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• pp.8-12
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• 2010

The properties of the conductor.mechanical, thermal, and electrical-are the key information in the design and optimization of superconducting coils. Particularly, in devices using second generation (2G) high temperature superconductors (HTS), whose base materials (for example, the substrate or stabilizer) and dimensions are adjustable, a design process for conductor optimization is one of the most important factors to enhance the electrical and thermal performance of the superconducting system while reducing the cost of the conductor. Recently, we developed a numerical program that can be used for 2G HTS conductor optimization. Focusing on the five major properties, viz. the electrical resistivity, heat capacity, thermal conductivity, Z-value, and enthalpy, the program includes an electronic database of the major base materials and calculates the equivalent properties of the 2G HTS conductors using the dimensions of the base materials as the input values. In this study, the developed program is introduced and its validity is verified by comparing the experimental and simulated results obtained with several 2G HTS conductors.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.269-271
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• 2003

A typical HTS power transmission cable has multi-layer conductor structure to increase the current capacity. The tapes of the innermost layer are wound on a round former, and adjacent tapes of another layer are separated by a thin insulating film. In steady state, the total current flows in the conductor layer, and consequently there is magnetic field between the inner and outer layer. This paper describes a magnetic field amplitude around the conductor layer and the HTS tape by a transport current. Also, this paper will help for future cable conductor prototypes.