• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.200-202
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• 2004

Characteristics of the break down current of HTS tape with different insulator are described. The various insulators are utilized for enduring the high voltage in superconducting power devices. The break down current of HTS tape largely depends on insulators wound round HTS tape. In this research, The break down currents of Bi-2223 tape, which is widely used for superconducting power devices are tested and discussed. It is expected that results from this study can be utilized as basic data in designing superconducting power devices.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.735-737
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• 2003

A superconducting motor consisting of high temperature superconducting (HTS) rotor and air-core stator is under development in Korea Electrotechnology Research Institute. HTS motor was designed for having the rated power of 100hp at 1800 rpm. HTS field winding is composed of sixteen HTS race track shaped coils wound with stainless steel-reinforced Bi-2223 tape conductor by react and wind fabrication method. Nomex Paper was used for electrical insulation. Each of four magnet pole assemblies was constructed with four double pancake sub-coils, mechanically stacked and electrically in series. Four magnet assemblies were fixed on an aluminum support structure to make effective heat transfer. Critical current (Ic) of HTS field winding was 41A but minimum Ic of sub-coils was 35A at 77K and self field. Joule heat generated in HTS field winding was 2.11W at 77K and 35A.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.900-902
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• 2003

Critical current($I_c$) degradation of HTS tapes after bending is one of the holiest issues in HTS development and application studies. Many people are measuring $I_c$ degradations for effect of tending radius. However even if the bending radius is larger than the breaking radius a HTS tapes can be damaged by repetitive bending, which is unavoidable in the winding processes. Therefore, We studied the $I_c$ degradation after repetitive bending, at 77K with self-field, of Bi-2223 tapes processed by "Powder-in-Tube" technique, which was made by America Superconductor Corporation(AMSC), Innova Superconductor Technology(InnoST) and Korea Electro-technology Research Institute(KERI). For each specimen $I_c$ degradation was measured various bending radius as function of repetitive bending number.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.52-57
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• 2002

High temperature superconductors can only be applied against an engineering specification that has to be determined for each particular application form the design requirements for economic viability and for operation margins in service. However, in order to realize the HTS transformer, it is necessary to establish the high voltage insulation technique in cryogenic temperature. Therefore, the composite insulation of double pancake coil type transformer are described and ac breakdown voltage characteristics of liquid nitrogen($LN_{2}$) under HITS pancake coil electrode made by Bi-2223/Ag are studied. Breakdown in $LN_{2}$ is dominated electrode shape and distance. And we investigated AC breakdown properties of $LN_{2}$ and complex conition of cryogenic gaseous nitrogen($CGN_{2}$) obove a $LN_{2}$ surface. Also, the surface voltage of GFRP was measured as a function of thickness and electrode distance in $LN_{2}$ and complex condition of $CGN_{2}$ above a $LN_{2}$ surface. This research presented information of electrical insulation design for double pancake coil type HTS transformer.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.32-36
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• 2007

On the contrary of a conventional motor with very narrow air-gap. it is difficult to calculate the accurate magnetic field distribution and the performance of an air-cored superconducting motor by 2 dimensional analysis. which does not use high permeability material except outer machine shield. This paper aims to do analysis of magnetic field and force distribution from the 3 dimensional modelling of a 1MW class superconducting synchronous motor. Especially. the field coil composed of Bi-2223 high-temperature superconductor and the outer machine shield are modelled by finite element analysis software according to their structures and the self-inductance and Lorentz force are calculated based on the 3 dimensional magnetic field calculation. Moreover. the influence of an important parameter, synchronous reactance, has been analyzed on the machine performances such as voltage variation and output power.

• Progress in Superconductivity and Cryogenics
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• v.10 no.3
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• pp.23-26
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• 2008

Constructions of coated conductor which is differently from Bi-2223 is comprised multiple coatings on a base material or substrate and designed to achieve the highest degree of alignment possibility of the atoms in the superconductor material. In this study, we are measured and analyzed degradations of critical current according to diameter. In addition to study the effects of bending strain, we observed the AC loss of coated conductor and carried out analytical study for relation between Ic degradation and AC loss as well. The measurement of AC loss and numerical calculation was carried out based on Norris theory to compare with experimental results. The relationship between critical current and AC loss of HTS tapes with partial deformation by mechanical stress was studied. These results will amount the most important basis data in the of HTS cable, magnet, etc that winding work is required.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.342-343
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• 2009

Paper factories use a large amount of water and same amount of wastewater is generated. It is important to purity and recycle the wastewater because of water shortages and water pollution. The existing water treatment facilities like precipitation process need large-scale equipment and wide space to purity the wastewater of paper factory. High gradient magnetic separation (HGMS) system has the merits to purity rapidly because of large voids at filter and to occupy small space. In this paper, two types of superconducting magnets were used for HGMS systems. Cryo-cooled Bi-2223 superconducting magnet system with 70 mm room temperature bore and 200 mm of height was prepared. Cryo-cooled Nb-Ti superconducting magnet with 100 mm room temperature bore and 600 mm of height was used for magnetic separator. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets. The various magnetic seeding reactions were investigated to increase the reactivity of coagulation. The effects of magnetic separation of wastewater were investigated as variation of magnetic field strength and flow rate of wastewater.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.27-31
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• 2004

This paper describes the development and fabrication of a high temperature superconducting motor which consists of HTS rotor and air-core stator. The machine was designed for the rated power of 100hp at 1800 rpm. The HTS field windings are composed of the double-pancake coils wound with AMSC's SUS-reinforced Bi-2223 tape conductor. These were assembled on the support structure and fixed by a bandage of glass-fiber composite. The cooling system is based on the heat transfer mechanism of the thermosyphon by using GM cryocooler as cooling source. The cold head is in contact with the condenser of a Ne-filled thermosyphon. The rotor assembly was tested independently at the stationary state and combined with stator. Characteristic parameters such as reactances, inductances, and time constants were determined to obtain a consistent overview of the machine operation properties. This motor has met all design parameters by demonstrating HTS field winding, cryogenic refrigeration systems and an air-core armature winding cooled with air. The HTS field winding could be cooled down below 30K. No-load test of open-circuit characteristics(OCC) and short-circuit characteristics(SCC) and load test with resistive load bank were conducted in generator mode. Maximum operating current of field winding at 30K was 120A. From OCC and SCC test results synchronous inductance and synchronous reactance were 2.4mH, 0.49pu, respectively. Efficiency of this HTS machine was 93.3% in full load(100hp) test. This paper will present design, construction, and basic experimental test results of the 100hp HTS machine.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.3-5
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• 2001

Racetrack coils are used in many areas of superconductivity applications such as generators, motors, maglev, wiggler magnets and so on. The fabrication and characteristics of race-track type High Tc Superconducting (HTS) magnets were carried out. The Magnet is composed of 3 pancake coils wound by 37-filamental Bi-2223/ Ag-alloy tapes. Quench current ($I_q$) of both whole magnet and 3 pancake coils were measured. At 77K under the self-field, $I_q$ of magnet was 12A, while in the case of middle pancake coil, $I_q$ was 15A. The upper pancake coils of racetrack magnet with iron plates, magnet having optimized current distribution and initial magnet are compared with each other through 3D FEA, manufacturing and testing these magnets. The measured performance of the upper pancake coil #3 with iron plates improved by 50% on the basis of initial pancake coil #3. Quench current ($I_q$) of field winding was 12A. In addition, the fabrication processes and the characteristics of HTS magnet are described.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.05a
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• pp.4-4
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• 2009

Paper factories use a large amount of water and same amount of wastewater is generated. It is important to recycle the wastewater because of water shortages and water pollution. The existing water treatment facilities like precipitation process need large-scale equipment and wide space to purify the wastewater of paper factory. High gradient magnetic separation (HGMS) system has the merits to purify rapidly because of large voids at filter and to occupy small space. In this paper, two types of superconducting magnets were used for HGMS systems. Cryo-cooled Bi-2223 superconducting magnet system with 70 mm room temperature bore and 200 mm of height was prepared. Cryo-cooled Nb-Ti superconducting magnet with 100 mm room temperature bore and 600 mm of height was used for magnetic separator. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets. The various magnetic seeding reactions were investigated to increase the reactivity of coagulation. The effects of magnetic separation of wastewater were investigated as variation of magnetic field strength and flow rate of wastewater.