• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.204-209
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• 2002

A PDP(Plasma Display Panel) module consists of a discharge panel, a SMPS(Switched Mode Power Supply) for power supply, driving boards for panel control, and a logic board. Driving boards supply high voltage pulses to induce glow discharge in the PDP panel. The electrical pulses excite the circuit elements and subsequently generate acoustic noises. The main sources of the noise in the circuit are the transformer of SMPS and the power MOSFET(Metal Oxide Semiconductor Field Effect Transistor) of driving boards, and the heat sinks often amplify the noise level. The reduction of the acoustic noises was achieved by modifying both the structural and circuit elements. The structural method was executed by the improvement of heat sinks. The optimization of SMPS and condensers was carried out for the circuit elements.

• Fire Science and Engineering
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• v.11 no.4
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• pp.25-31
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• 1997

In this study, EMTP(Electromagnetic Transients Program) which is one of the most well-known computer simulation methods is used to collect the data for a power plant fault. EMTP is the program for an interpretation of the phenomena of electric transients, and is designed to manifest the data of the electric current and voltage etc. at the time of a power plant fault. By EMTP, I analyze the properties of the heat energy which are transferred from the electrics when a power plant fault brings out. In terms of the results of this study, it is able to measure the heat energy at a power plant fault (power transformer) and to be acquired of the related data. And moreover, these data are expected to be used as a standard for the protection of the fire owing to a high voltage power transformer fault.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.4
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• pp.285-292
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• 1985

A computer program for thermal design analysis has been developed to predict the performance of an absorption heat transformer. The effects of temperature boost, cooling water temperature and effectiveness of components on the performance were investigated. Not only the detailed thermodynamic states such as temperatures, concentration of the solution, and mass flow rate at each point of the process but also the heat transfer rate in each component could be easily determined with given input parameters. The system's coefficient of performance (COP) was seen to increase with increased effectiveness of components, decreased temperature boost of hot water, and decreased cooling water temperature. Even though the COP increases with increased effectiveness of the components, the variation in the COP is not substantial above certain values of the effectiveness. A reference design point can be selected on this basis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1154-1159
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• 2006

The mold transformers have been widely used in underground substations of large building and have some advantages when compared with oil-transformer. Those advantages are low fire risk, environmental compatibility, compact size and high reliability. The mold transformer is generally known to have cooling duct between low voltage and high voltage coil. To achieve better compact structure and low loss, mold transformers made by one body molding method has been developed. Nevertheless, such kinds of transformer need better cooling method because heat radiation between each winding is still of problem. The life of transformer is significantly dependent on the thermal behavior in windings. Many designers have calculated temperature distribution in transformers and hot spot point by finite element method(FEM) to analyze winding temperature rise. In this paper, the temperature distribution analysis of 100 kVA pole mold transformer for power distribution were investigated by FEM program and the thermal analysis results were compared with temperature rise test.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.7
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• pp.48-57
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• 2021

The main research content of this paper is to evaluate the structural integrity and the cooling performance of 4250 kVA power transformer with ONAN(Oil Natural and Air Natural) mode. The dynamic analysis is used to verify the structural safety of the transformer by seismic loading. The transformer structure is simplified and NX software is used to build a three-dimensional model, and ANSYS commercial software is used to calculate the stress and deformation by applying corresponding load. The analysis result was evaluated whether it satisfies the design requirements according to the IEEE Std 693 standard. In terms of thermal analysis to evaluate the cooling performance, the thermal physical model is used to calculate the heat exchange between the radiator and the tank in the steady state, and the result is input into the Fluent software to calculate the internal temperature field of the transformer tank, which reduces the calculation cost of thermal fluid. Comparing the simulated hot spot temperature and top oil temperature of the transformer with the calculation results of the IEC60076 classic model, it is found that the error is only 1.9%.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.4
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• pp.340-349
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• 1987

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.1
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• pp.54-65
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• 1994

Performance of naturally circulating cooling system of $SF_6$ gas charged transformer was simulated and the variations of gas flow rate, maximum coil temperature, gas temperature and cooling air temperature were investigated with respect to the height of radiator, interplates distance and heat generation rate at core. The results show that the height of radiator most significantly affects the performance of natural circulating cooling system of transformer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.2
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• pp.106-115
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• 1992

Numerical analysis of the laminar natural convection in an enclosure of the 20KVA oil-immeresed transformer is presented. The core in the transformer is modelled as a rectangular cylinder and calculation is carried out for $Ra=10^3-10^6$. The correlating equation between the inner cylinder mean Nusselt numbers and Rayleigh numbers can be obtained. The conduction and convection regimes for the variation of Rayleigh numbers are well represented in the temperature distributions along the side wall of the inner cylinder. For high Rayleigh numbers, it is found that the recirculating flow in the enclosure above the inner cylinder is divided into two recirculation regions.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.114-120
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• 2014

In this paper, a method for multi-physics analysis of the temperature-dependent properties of an oil-immersed transformer is discussed. To couple thermal fields with electromagnetic and fluid fields, an algorithm employing a user defined function (UDF) is proposed. Using electromagnetic analysis, electric power loss dependent on temperature rise is calculated; these are used as input data for multi-physics analysis in order to predict the temperature rise. A heat transfer coefficient is applied only at the outermost boundary between transformer and the atmosphere in order to reduce the analysis region. To verify the validity of the proposed method, the predicted temperature rises in high-voltage (HV) and low-voltage (LV) windings and radiators were compared with the experimental values.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.151-152
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• 2005

Both $Al_2O_3$ and AlN nanopowders with diameters from ${\mu}m$ to mm were bead-milled and surface-modified by stabilizing agent. The size of bead-milled nanoparticles compared with the primary powder was effectively decreased and was dependent on milling time and bead size. The results of dispersion stability analysis indicated that chemical bonding between nanoparticles and surfactant is more effective than chemical adsorption to prepare the stable transformer oils containing nanoparticles. In this study, the thermal conductivity of the transformer oils containing nanoparticles was measured by transient hot-wire and laser flash methods.