• Proceedings of the KSME Conference
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• 2000.04b
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• pp.379-384
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• 2000

High-Tc superconducting current leads with multi-step and continually varied cross-sectional area are studied to reduce heat leak into cryostat and material use. Assuming conduction-cooled lead the cross-sectional area is reduced along the heat flow direction according to the increase of critical current density which increases with decreasing temperature. In this study, we also analyze the multi-step cross-sectional area High-Tc current leads. The multi-st데 current leads changes the cross-sectional area to have constant safety-factor at changed section. The heat leak into cryostat, total voume, safety-factor and the temperature profiles are compared to those of the constant safety-factor current leads. The developed methods are applied to the Bi-2223 superconductor sheathed with Ag-Au alloy.

• Journal of Power Electronics
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• v.13 no.3
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• pp.497-506
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• 2013

This paper proposes a new method to improve the available battery capacity in electric vehicles by connecting lead-acid batteries with lithium-ion battery in parallel to supply power. In addition, this method combines the discharge characteristics of batteries to improve their efficiency and lower their cost for electric vehicles. A lithium-ion battery set is used to connect with N sets of lead-acid batteries in parallel. The lead-acid battery supplies the initial power. When the lead-acid battery is discharged by the load current until its output voltage drops to the cut-off voltage, the power management unit controls the lead-acid battery and changes it to discharge continuously with a small current. This discharge can be achieved by connecting the lead-acid battery to a lithium-ion battery in parallel to supply the load power or to discharge its current to another lead-acid or lithium-ion battery. Experimental results demonstrates that the available capacity can be improved by up to 30% of the rated capacity of the lead-acid batteries.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.219-220
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• 2002

In this paper, we propose non-soldered current lead was introduced which has low contact resistivity for fault current limiters of YBCO film. Carbon/Cu has good thermal conductivity, electrical conductivity and chemically stable, and so forth. Therefore it seems to be suitable material of current lead for current limiters of YBCO film. We have investigated electric field-current in field of 0-130 mT and quench characteristics of a YBCO film. Experimental results show that characteristics of transport is all right using Carbon/Cu-current lead.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.226-229
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• 2000

Long lengths (<100m) of BSCCO 2223 tapes were fabricated of optimal process. We have I$_c$${\sim}$22A, J$_c$${\sim}$22,000A/cm$^2$(77K, 0T) at last heat treatment, and then prototype 1000A class current lead (length ${\sim}$50cm) fur HTS applications was fabricated using these tapes. Surface of current lead except both end part (${\sim}$1cm) was clothing with fiber glass. Also the transportation properties and thermal loss was studied on prototype 1000A class current lead.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.1
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• pp.20-26
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• 2009

In this paper, the switching mode conversion type pulse charger by fly-back converter method for lead battery of the solar cell generator equipment is proposed. And we propose the control circuit and design method of insulated switching mode convert type pulse charger by fly-back convert method in the lead battery. The proposed system can minimize the current consumption by digital pulse. Also the proposed system can generate the constant 10[KHz] frequency, transmit the signal with main control system in the power control system. And it supervises the state of lead battery using one chip micro processor. The proposed the switching mode conversion type pulse charger by the fly-back converter method can charge fast and stabilize lead battery with nominal value 12[V], 20[AH]. Also we propose the design procedure of the power control circuit for turn ratio of fly-back inductor and determining method of values such as the charging current, bulk current, partial current, over current value and fixed charging voltage. The experiment results for the voltage and current wave for partial, bulk, over and fixed charging period show the good charging effect and performance. And the PCB and internal coupling diagram of the switching mode conversion type pulse charger by fly-back converter method is presented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.26-34
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• 1998

In this paper, we confirm that the instanteneous phase current of the bifilar-wound hybrid stepping motor is dependent of lead angle by the experimental results. The variation of phase current with lead angle gives informations about the rotor position at the moment when phase winding coil is excited. We show that the rotor position of the bifilar-wound hybrid stepping motor for the closed-loop drives can be detected by using the instantaneous phase current measurement. We propose an instantaneous phase current equation as the function of electrical lead angle by the modeling of the bifilar-wound hybrid stepping motor. We also analyze the relationship between instantaneous phase current and rotor position by the computer simulation results. By the experimental results, we also confirm that the information about the rotor position can be obtained from the instantaneous phase current values at the instance of $\pi/2$ electrical angle of excitation pulse. pulse.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.84-88
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• 2001

The optimum cross-sectional area Profile of gas-cooled high-temperature superconductor (HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant safety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-step HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-step current leads are discussed.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.275-279
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• 1999

It is well known that HTS current lead minimizes helium vaporizations much less than the conventional current lead. To estimate the helium vaporizations in the design step, we need to compute the exact the temperature distributions on the lead. Unfortunately, the thermal parameters such as thermal conductivity and electrical resistivity depend strongly on the temperature. That is, heat equation itself has a nonlinear characteristics in the current lead. Furthermore, the uncertainties of helium vaporizations make it more difficult to estimate the boundary values. So far, numerical analyses using constant parameters in finite intervals have been used. In this paper, we calculate the temperature distribution in the current lead in considerations of temperature dependent parameters. The results showed self consistencies.

• Journal of the Korean Applied Science and Technology
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• v.23 no.4
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• pp.347-354
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• 2006

Generally, it has been known that positive plate efficiency is the most influential effect on the initial current capacity of lead acid battery. Thus, in this study, we have investigated the curing effect of the positive plate, which is one of the important lead acid battery processes. The curing process of the positive plate is performed either with the separation of each plate with 1mm gap or with no gap of plate. As a result, when there is no interval between each plate, the higher temperature current happened than expected, resulting in the changes in the initial current efficiency of the lead acid battery. The chemical composition and crystal structure of a material coated on the positive plate were identified with XRD and SEM. It was resulted that were only there not a lot of 4BS (tetrabasic-lead sulfate, $4PbO{\cdot}PbSO_4)$ on the plate in case of curing of plates without interval, but a large quantity of $Pb_3O_4$ also formed on the surface. On the other hand, it was observed that 3BS (tribasic-lead sulface, $3PbO{\cdot}PbSO_4{\cdot}H_2O)$ was the main product on the plate in case of typical curing process with some interval. From the initial current capacity test, the positive plate having 3BS was approximately 40% higher in initial current capacity than that having 4BS. It was concluded that 4BS and $Pb_3O_4$ on the plate surface were harmful to the initial current capacity of lead acid battery.

• Progress in Superconductivity
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• v.14 no.2
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• pp.122-127
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• 2012

Current leads are one of the important components for carrying the current to the coil in the superconducting magnet system. Heat leakage through the current lead is the major factor of entire heat load in the cryogenic system because current leads carry the current from room temperature to near 4 K, connecting thermally each other. Therefore, minimization heat load through current lead can reduce the operating temperature of superconducting magnet. The semi-retractable current lead, composed of multi-contact connector and HTS element, is one of good options. Comprehension of Multi-contact connector's structure, contact resistance and heat generation is essential for estimating heat generation in current leads. Multi-contact connector has several louvers inside of socket and the shape, number, size of louvers are different with the size of connector. Therefore contact area, current path and contact resistance are also different. In this study, the contact resistance in multi-contact connector is measured using the electrical power as a function of connector's size and temperature. Also, the unique correlation of electrical contact resistance is derived and heat generation is estimated for superconducting magnet application.