• KIEE International Transactions on Power Engineering
• /
• v.3A no.4
• /
• pp.222-230
• /
• 2003

This paper presents reference designs for vapor-cooled HTS/Copper leads rated at 25 kA and 40 kA and that satisfy a protection criterion. Each HTS section is cooled by the effluent helium vapor boiling from a 4.2-K bath. Each HTS section is based on a design concept in which a short portion of its warm end (77.3 K) operates in the current-sharing mode; such operation results in a considerable saving for HTS materials required in the HTS section. Two designs of "fully superconducting" vapor-cooled HTS sections, one rated at 25 kA and the other at 40 kA are also presented as comparison bases for the new HTS sections. Each warm end of HTS sections is coupled to an optimal vapor-cooled copper lead rated at the same current as that for the HTS section. The extra coolant required at 77.3 K at the coupling station, an optimal length of the copper section will be shorter than that optimized for helium-vapor cooling between 4.2 K and room temperature.mperature.

• Progress in Superconductivity and Cryogenics
• /
• v.15 no.4
• /
• pp.21-25
• /
• 2013

In power grid, in order to level out the generation with demand, up-gradation of the system is occasionally required. This will lead to more fault current levels. However, upgrading all the protection instruments of the system is both costly and extravagant. This issue could be dominated by using Smart Fault Current Controller (SFCC). While the impact of Fault current Limiters (FCL) in various locations has been studied in different situations for years, the performance of SFCC has not been investigated extensively. In this research, SFCC which has adopted the characteristics of a full bridge thyristor rectifier with a superconducting coil is applied to three main locations such as load feeder, Bus-tie position and main feeder location and its behavior is investigated through simulation in presence and absence of small Distributed Generation unit (DG). The results show a huge difference in limiting the fault current when using SFCC.

• 한국초전도학회:학술대회논문집
• /
• v.10
• /
• pp.236-240
• /
• 2000

Bi-2223 HTS current leads for a superconducting magnetic energy storage(SMES) magnet were designed and manufactured. The HTS leads composed of Bi-2223/AgAu tapes and stainless steel former were connected to conventional vapor-cooled copper leads. The heat input to the liquid helium through the HTS lead was 0.39 W/lead when the warm end part's temperature is 65 K. And, the critical current of the HTS leads was about 1.6 kA when the warm end part's temperature is 80 K. The measured those values are well consistent with computed values.

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.835-837
• /
• 1998

Current lead plays the part of connector between ambient temperature and liquid helium superconducting magnet. Having zero resistance characteristic, it is expected that HTS has very low thermal conductivity and generate no joule heat when fabricated to current lead. In particular, among the HTS meterials, HTS tape has high Jc and Ag-sheath of tape plays the part of stabilizer, but it has too poor mechanical strength to be applied and when fabricated as long length tape, it has tendency to decline Jc seriously. In this study, we fabricated Bi-2223 multifilamentary tapes and then made current lead with stacking type using them. Through this work, we conclude that the defect of HTS long length tape is decreased by addition the number of stacking tape and that current lead is able to operate more stably by minimizing the gap of tapes.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2002.02a
• /
• pp.50-55
• /
• 2002

The transient numerical analysis was performed for vapor cooled current leads. The present numerical modeling considered that there is temperature difference between the copper lead and the helium vapor flow. This numerical modeling was compensated and validated by the experiment with commercially available 100 A current leads. The numerical modeling in this paper described thermal characteristics of overloaded current leads more accurately than the conventional steady state analysis. Proper design of overloaded current leads was suggested by indicating the appropriate overloading factor in the pulse mode operation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.4
• /
• pp.552-560
• /
• 1997

Analysis is performed to determine the optimal lengths or cross-sectional areas of refrigerator-cooled current leads that can be applied to the conduction-cooled superconducting systems. The binary current lead is composed of the series combination of a normal metal at the upper(warm) part and a high $T_c$ superconductor(HTS) at the lower(cold) part. The heat conduction toward the cold end of HTS part constitutes a major refrigeration load. In addition, the joint between the parts should be cooled by a refrigerator in order to reduce the load at the low end and maintain the HTS part in a superconducting state. The sum of the work inputs required for the two refrigeration loads needs to be minimized for an optimal operation. In this design, three simple models that depict the refrigeration performance as functions of cooling temperature are developed based on some of the existing refrigerators. By solving one-dimensional conduction equation that take into account the temperature-dependent properties of the materials, the refrigeration works are numerically calculated for various values of the joint temperature and the sizes of two parts. The results show that for given size of HTS, there exist the optimal values for the joint temperature and the size of the normal metal. It is also found that the refrigeration work decreases as the length of HTS increases and that the optimal size of normal metal is quite independent of the size of HTS. For a given length of HTS, there is an optimal cross-sectional area and it increases as the length increases. The dependence of the optimal sizes on the refrigerator models employed are presented for 1kA leads.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2002.02a
• /
• pp.374-377
• /
• 2002

Magnetic field is necessary to control the convection of melted silicon and to improve the quality of the wafer in the 12inch silicon wafer growing process. Nowadays, superconducting magnet is used in this process. We fabricated and tested a saddle shaped superconducting magnet for 8inch silicon wafer growing system. And the protection circuits for HTS current lead and superconducting coil are designed and manufactured. In this paper, their manufacturing process and test results are introduced.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2001.02a
• /
• pp.48-49
• /
• 2001

Cryogenic technology is one of the key technologies for fusion reactor equipped with superconducting coil for plasma confinement. The KSTAR(Korea Superconducting Tokamak Advanced Research)Project is in progress since 1996. Major parameters of the KSTAR tokamak are : major radius 1.8m, minor radius 0.5m, toroidal field 3.5 Tesla and plasma current 2MA with a strongly shaped plasma cross-section and double -null diverter. Considering practical engineering constraints, the KSTAR device is designed for a pulse length of 300 sec in up-graded operation mode but in the initial configuration would provide a pulse length of 20 sec provided by the poloidal coil system in base-line operation mode. The cryogenic system is composed as follows : cold box, helium compressor system, distribution box, helium gas buffer tank, helium gas purifying system, gas recovery system, liquid helium storage dewar, current lead box, current bus line and liquid nitrogen storage tank.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.5
• /
• pp.418-423
• /
• 2003

AC loss is an important issue in the design of high-T$\sub$c/ superconducting power cables which consist of a number of Bi-2223 tapes wound on a former. In the cables, the tapes have different critical currents intrinsically. And they are electrically connected to each other and current leads. These make loss measurements considerably complex, especially for short samples of laboratory size. So special cautions are required in the positioning of voltage leads for measuring the true loss voltage. In this work we have prepared a conductor composed of three Bi-2223 tapes with different critical currents. The critical current and AC loss characteristics in the conductor have experimentally investigated. The results show that for uniform current distributions the conductor's critical current is proportional to the critical current of the Bi-2223 tape to which a voltage lead is attached. However it depends on the current non-uniformity parameter in the conductor rather than the tape's critical currents for nonuniform current distributions. The loss tests indicate that the AC loss is dependent on arrangements of voltage leads but not on their contact positions. The measured losses in the conductor also agree well with the sum of the transport losses measured in each Bi-2223 tape.

• Progress in Superconductivity and Cryogenics
• /
• v.19 no.2
• /
• pp.38-43
• /
• 2017

The role of current lead in high-temperature superconducting synchronous machine (HTSSM) is to function as a power supply by connecting the power supply unit at room temperature with the HTS field coils at cryogenic temperature. Such physical and electrical connection causes conduction and Joule-heating losses, which are major thermal losses of HTSSM rotors. To ensure definite stability and economic feasibility of HTS field coils, quickly and smoothly cooling down the current lead is a key design technology. Therefore, in this paper, we introduce a novel concept of a cooling anchor to enhance the cooling performance of a metal current lead. The technical concept of this technology is the simultaneously chilling and supporting the current lead. First, the structure of the current lead and cooling anchor were conceptually designed for field coils for a 1.5 MW-class HTSSM. Then, the effect of this installation on the thermal characteristics of HTS coils was investigated by 3D finite element analysis.