• Progress in Superconductivity and Cryogenics
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• v.1 no.2
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• pp.37-42
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• 1999

The stability of high-temperature superconducting current leads for cryogenic devices are investigated. By assuming full transition from superconducting state to normal state at a transition temperature, the HTS current at a transition temperature, the HTS current lead shows bifurcation phenomenon. There is a bifurcation shape-factor, HTS leads have three steady state. Below the bifurcation shape-factor, the superconducting current lead is unconditionally stable, because there exists only one steady-factor HTS current lead is conditionally stable depending on the shape and intensity of disturbance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.244-245
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• 2007

Specially, High Temperature Superconducting power-transmission cable(HTS cable), 3-phase 100m long, 22.9kV class HTS power transmission cable system have been developed by Korea Electrotechnology Research Institute (KERI) and LS cable Ltd. that is one of 21st century frontier project in Korea. This cable was installed in KEPCO(Go-chang) testing site. In case of manufacturing HTS cable, superconducting joint is very important because they need very long tapes. Therefore, this paper gives some investigation of AC Loss in joined HTS tape by using several joint methods. Finally, this paper was shown background data for the form of HTS cable joint.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.48-52
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• 2013

This paper compares the features of second generation (2G) High Temperature Superconducting (HTS) field coil with those of magnesium diboride ($MgB_2$) field coil for a 10 MW class superconducting generator. Both coils can function effectively in their respective magnetic flux density range: 10-12 T for 2G HTS field coil, 2 T for $MgB_2$ superconducting field coil. Even though some leading researchers have been developing 10 MW class superconducting generator with 2G HTS field coil, other research groups have begun to focus on $MgB_2$ wire, which is more economical and suitable for mass production. However 2G HTS wire is still appealing in functions such as in-field property and critical temperature, it shows higher in-field property and critical temperature than $MgB_2$ wire.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.931-932
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• 2007

Specially, High Temperature Superconducting power-transmission cable(HTS cable), 3-phase 100m long, 22.9kV class HTS power transmission cable system have been developed by Korea Electrotechnology Research Institute (KERI) and LS cable Ltd. that is one of 21st century frontier project in Korea. This cable was installed in KEPCO(Go-chang) testing site. In case of manufacturing HTS cable, superconducting joint is very important because they need very long tapes. Therefore, this paper gives some investigation of AC Loss in joined HTS tape by using several joint methods. Finally, this paper was shown background data for the form of HTS cable joint.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.35-38
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• 2021

Conventional direct current (DC) rotating machines are usually used for crane and press machine using high torque in metal and steel industries, because of a constant output power along variable rotating speed. A general DC motor with permanent field magnets could not increase a magnetic flux density at a gap between armature coils and field magnets. However, a superconducting DC motor has field magnets composed with high temperature superconducting (HTS) coils and it could increase the magnetic flux density at the gap to over 10 times than those of a general DC motor by control the excitation current into HTS coils. The superconducting DC motor could be operated with extremely high torque and constant output power at a low rotational speed. In this paper, a 500 W superconducting DC rotating machine was conceptually designed with a LN₂ (Liquid Nitrogen) cooling method and the operation characteristics results of HTS field magnets were presented. The two no-insulation HTS magnets for a 500 W superconducting DC rotating machine were fabricated. The excitation current for the HTS magnets could be controlled from 0 to 40 A. This test results will be available to design large-sized HTS magnets for a number of hundred kW class superconducting DC rotating machine under LN₂ cooling system.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.50-54
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• 2018

We analyzed the temperature dependency of the AC losses in high temperature superconducting (HTS) coils. In the case of a short sample of an HTS tape, the magnetization loss at 4.2 K could be higher than the one at 77 K for a same transport current. It happens when the perpendicular magnetic field is above a certain magnitude. The AC loss characteristics of solenoidal coils have been analyzed at the temperatures of 65 K and 77 K. They were categorized by the aspect ratios. The operating current of a solenoid was normally set about 70 % of the critical current. An HTS solenoid with the same operating current of 77 K causes larger AC losses at 65 K in the most cases of the HTS solenoids. We also analyzed the AC loss characteristics due to the temperature variations for three types of superconducting magnetic energy storages. Two of them were solenoidal types and the other was toroidal type. The results showed the tendency for the coils to have higher AC losses at lower temperature with the same operating currents and scenarios.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.42-46
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• 2002

This research is conducted with the object of Piling up the foundation of design technologies for high temperature superconducting (HTS) power transformer which is thought to be as a powerful power transformer of next generation. In this study, not only the theoretical design of high temperature superconducting (HTS) transformer but also the arrangements of superconducting tape and the cooling method have been conducted. Moreover, electromagnetic analyses using finite element method (FEM) were conducted to confirm the efficiency of the designed transformer.

• Progress in Superconductivity and Cryogenics
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• v.6 no.1
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• pp.33-38
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• 2004

This paper presents an effective simulation method for the high temperature superconducting (HTS) transformer using PSCAD/ EMTDC. Although researches and developments are performed for the HTS technologies, problems such as AC loss and quench phenomenon need to be solved for efficient design of HTS transformer. In addition, pre-study on the HTS transformer is a sort of time and cost consuming work, thus it is very worthy or being analyzing the characteristics of the HTS transformer in advance through a proper simulation method. It is very important to analyze the HTS devices by the simulation for seeking suitable and reasonable parameters for the practical application of those apparatuses in advance. A software- based component is suggested for- the simulation of the HTS transformer using PSCAD/ EMTDC and the numerical results are analyzed in detail in this paper.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.51-54
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• 2013

This paper deals with harmonic components of the voltage on high temperature superconducting wire carrying an alternating current. HTS wire is used to manufacture superconducting power applications carrying an alternating current. Typically, international standard, IEC 61788-3 is used for critical current measurement. Thus, it is not ideal that critical current criteria in dc are adapted to superconducting power devices to decide the operating current of the devices. In this paper, we confirmed odd harmonic voltage on HTS wires carrying an AC. The ratio between harmonic components and fundamental component can be significant clues to decide the critical current criteria for HTS wire and its power applications in AC circumstance.

• KIEE International Transactions on Power Engineering
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• v.3A no.2
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• pp.100-108
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• 2003

This paper presents the design and performance results of a pair of 6-kA high-temperature superconducting (HTS)-copper current leads, in which, over a short length at the warm end (e.g.,77K) of each HTS section, comprised of paralleled Bi-2223/Ag-Au tapes, is operated in the current-sharing mode. Because of their reliance on vapor cooling, the leads are applicable only to liquid helium cooled superconducting magnets such as those used in high-energy Physics accelerators and fusion machines. The experimental measurements have demonstrated that key performance data of the new 6-kA HTS-Copper leads agree reasonably well with those expected from design.