• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.44-47
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• 2019

This paper is a study of recovery under load process of superconducting fault current limiter (SFCL). SFCL consists of five parallel-connected high-temperature superconductor (HTS) tapes additionally stabilized by stainless tape. Previously, HTS was heated by current pulse to simulate a short circuit in a power grid. During the cooling period, the current amplitude decreased to 23% or less of HTS critical current value, which is the simulation of network re-switching. When HTS with a polymer coating is cooled, temperature gradient on thermal insulation layer occurs, that prevents a boiling crisis and improves the heat sink into liquid nitrogen. Two samples are coated with a 30 ㎛ and 50 ㎛ polylactide (PLA) layers, reference sample has no polymer coating on it. Samples with a polymer coating show 3-5 times faster cooling than the reference one.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2839-2844
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• 2008

A PEMFC(proton exchange membrane fuel cell) is a good candidate for residential power generation to be cope with the shortage of fossil fuel and green house gas emission. The attractive benefit of the PEMFC is to produce electric power as well as hot water for home usage. Typically, thermal management of vehicular PEMFC is to reject the heat from the PEMFC to the ambient air. Different from that, the thermal management of PEMFC for RPG is to utilize the heat of PEMFC so that the PEMFC can be operated at its optimal efficiency. In this study, dynamic thermal management system is modeled to understand the response of the thermal management system during dynamic operation. The thermal management system of PEMFC for RPGFC is composed of two cooling circuits, one for controling the fuel cell temperature and the other for heating up the water for home usage. Dynamic responses and operating strategies of the PEMFC system are investigated during load changes.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.2
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• pp.76-87
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• 1992

Flow and heat transfer characteristics in a horizontal electronic circuit board are studied numerically. The board has the arrays of heated blocks and the spaces between the plates and blocks are changed. Air in used as cooling fluid, of which prandt1 number is 0.7. The velocity distributions, temperature distributions, Nusselt numbers and dimensionless friction factors are obtained on the spaces between the plates and the blocks, for the cases of Rayleigh number, 0 and 10$^{5}$ . When Rayleigh number is so large, such as 10$^{5}$ , that the effect of bouyancy is not negligible, fluid friction and heat transfer is increased more than those of forced convection. This may be caused by the generation of secondary flow on the cross section of primary flow. The effect of bouyancy is of the most efficient, when the space of blocks is about block-width and the space of plates is about 1.7 times of block-height.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.101-106
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• 2011

The failure of cooling system in Superconducting Fault Current Limiter(SFCL) increases the impedance of superconducting device, and due to malfunction of inner switches the SFCL opens the distribution system inadvertently when required to do so. In this paper, the ground fault and short circuit fault were classified as active failure and the open circuit fault was passive failure. A reliability model of SFCL considers the passive failure as well as active failure, and in the case study the reliability indices of distribution system are evaluated. It is possible that the reliability evaluation excluded passive failure makes the customers reliability seem so worse than it really was. Therefore, the reliability models of SFCL must include the active failure and passive failure together to evaluate the reliability of distribution system connected SFCL.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.1-13
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• 1998

The basic heat transfer process that occurs in a building can best be illustrated by an electrical circuit network. Present paper reports the dynamic simulation of annual energy consumption in an office building by the thermal resistance capacitance network method. Unsteady thermal behaviors and annual energy consumption in an office building were examined in detail by solving the simultaneous circuit equations of thermal network. The results are used to evaluate the accuracy of the modified BIN method for the energy consumption analysis of a large building. Present thermal resistance-capacitance method predicts annual energy consumption of an office building with the same accuracy as that of response factor method. However, the modified BIN method gives 15% lower annual heating load and 25% lower cooling load than those from the present method. Equipment annual energy consumptions for fan, boiler and chiller in the HVAC system are also calculated for various control systems as CAV, VAV, FCU+VAV and FCU+CAV. FCU+CAV system appears to consume minimum annual energy among them.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1431-1434
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• 1994

The annular induction electromagnetic pump with maximum flowrate of $60{\ell}/min$ for the sodium coolant system of liquid metal fast breeder reacters has been designed using the equivalent circuit method. The final optimum values of geometrical and electromagnetic parameters were obtained for an annular induction pump from the relation of the electrical variables giving the developing force to the fluid and the pressure drops between both sides of the pump. The physical properties of the core, coil condoctor materials in the high temperature and pump cooling systems under operation have been taken into account in the design of the pump. The structural material were also selected considering the reaction with sodium and the magnetic field distortion.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.555-557
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• 2003

As electric power transmission systems grow to supply the increasing electric power demand, transmission capacity is larger. but that's really difficult to secure the location for power transmission and distribution to user. The high temperature superconducting(HTS) cable is a method to solve this problem. But for applying to real systems, it needs to investigate the effect of HTS cable. The most important things is the investigation of fault condition. the fault on HTS cable include the quench state. When a fault occur in a circuit, three critical parameters(temperature, current density, magnetic field) exist. when one of these parameters exceeds the critical value, the superconducting becomes normal-conducting. f the cooling power is insufficient to recover the superconducting state, the normal-conducting zone expands. In order to solve these problem, this paper present simulate the quench state considering the over-current and over-voltage in the informal circuit and analyze the quench state.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1558-1563
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• 2015

In this paper, temperature characteristic analysis was performed by using a thermal equivalent circuit. To suppress the temperature rising, the cooling fan was installed in rotor. The temperature of permanent magnet was reduced from 66[$^{\circ}C$] to 55[$^{\circ}C$] by installing the fan. The temperature of the permanent magnets is difficult to measure. Therefore the temperature of end winding was measured directly by the thermo couple. The validity of this study was demonstrated as compared the calculated results with experimental ones.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.97-100
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• 1999

AC to DC single phase PWM converter for traction application requires rated high power and voltage. Therefor, series or parallel operation converters are necessary with considering the limitation of the power device specification. This paper compares the characteristic between two parallel operation of conventional PWM converter and Single phase three level converter about comparison of power circuit, cooling system control method and harmonic current by computer simulation.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.135-139
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• 2002

Most of all the mechanical devices are becoming more high-speed and high-power as well as their used condition being more polluted. So, it is necessary for these devices to equip cooling system to overcome that kind of severe using condition. In this study, corrosion test was carried out in distilled and tap water for the investigation on the corrosion characteristics of Al-alloy that is using as material for radiator.