• 조명전기설비학회논문지
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• 제21권1호
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• pp.104-110
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• 2007

본 논문은 권선내부에 온도계가 설치된 지상변압기를 제작하여 부하운전에 따른 배전용 변압기의 온도상승 특성과 절연유의 유전특성 변화를 관찰하였다. 관찰결과 배전용변압기의 경우 과열점은 세 권선 중 두개의 권선이 접하고 권선의 약 2/3 높이에 위치하고 있으며, 과열점과 절연유 상부 간에 약 $17[^{\circ}C]$의 일정한 온도차를 확인할 수 있었다. 또한 절연유의 정전용량특성은 온도와 선형적인 관계로 감소하는 특성을 보이며, 그 기울기는 열화율과 무관하게 -0.0106의 일정한 값을 관찰할 수 있었다. 이 결과는 수명손실의 정확한 계산과 열화진단을 위한 기구로 활용할 수 있을 것이다.

• 농업과학연구
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• 제42권3호
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• pp.231-235
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• 2015

This study was performed to investigate the change of the body surface temperature during socialization of weaning pigs. A total of 108 piglets (Landrace 60 and Yorkshire 48) aged 31 (${\pm}1.1$) day was used for this study. Experiment was designed as follows; familiar group (T1), randomly mixed with unfamiliar piglets (T2), mixed based on weight of unfamiliar piglet (T3). The transport and mixing of pigs were performed at 10:00, and then body surface temperature was taken by thermo-graphic camera after 4 hours (14:00). Average surface temperature and hot-spot-temperature, which is the hottest spot of the body surface, were analyzed using Testo IRsoft 3.1 software. Average temperature of body surface were 36.0, 38.2, and 37.5 in T1, T2, and T3, respectively. Average of body surface temperature in T2 and T3 were higher (p<0.001) than T1, and average temperature of body surface of T3 was greater (p<0.001) than that of T2. The hot-spot-temperature of T1, T2, and T3 were 38.7, 39.5, and 39.6, respectively. The hot-spot-temperature of T2 (p<0.01) and T3 (p<0.001) were significantly higher than that of T1. Above results demonstrate that grouping unfamiliar pigs leads to increase in the body temperature possibly by pigs aggressive behavior during social conflict. By the result on average body temperature, this study suggests that the mixing with similar body weight would increase the struggle time and frequency.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.402-405
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• 2002

This paper presented the characteristic of Heat-transfer on the winding composed with Epoxy-resin in a 50 kVA cast-resin dry type transformer The resin cast transformer is used widely in supplying electricity systems. However, to know the thermal characteristics of that is very useful in designing, manufacturing, and maintaining, there is no pertinent method to calculate this. In this paper, Based on the results of the physical characteristics and the simulation by commercial software using FEM method, we established the Prototype Model for this. According to that Model, an analysis on a variation of the hottest spot temperature was discussed as a function of thermal conductivity for the individual windings composed with Epoxy-resin. The thermal conductivity of the individual windings with reference to upper way was discussed.

• Tribology and Lubricants
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• 제35권1호
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• pp.77-86
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• 2019

The present study focuses on the effect of staggered integration factor (SIF) on Morton effect simulation results. The Morton effect is a synchronous rotordynamic instability problem caused by the temperature differential across the journal in fluid film bearings. Convection and conduction of heat in the thin film displaces the hot spot, which is the hottest circumferential position in the thin film, from -20 to 40 degrees ahead of the high spot, where the minimum film clearance is experienced. The temperature differential across the journal causes a bending moment and the corresponding thermal bow in the rotating frame acts like a distributed synchronous excitation in the fixed frame. This thermal bow may cause increased vibrations and continued growth of the synchronous orbit into a limit cycle. The SIF is developed assuming that the response of the rotor-lubricant-bearing dynamic system is much quicker than that of the bearing-journal thermal system, and it is defined as the ratio between the simulation time of the thermal system and the rotor-spinning period. The use of the SIF is unavoidable for efficient computing. The value of the SIF is chosen empirically by the software users as a value between 100 and 400. However, the effect of the SIF on Morton effect simulation results has not been investigated. This research produces simulation results with different values of SIF.

• 대한기계학회논문집B
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• 제21권3호
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• pp.457-472
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• 1997

We studied the temperature distribution and heat transfer characteristics of TEFC induction motor with thermal network program for more efficient design and better cooling performance of it. We knew the characteristics and the windage loss of outer cooling fan from fan test experiments. Frame axial and peripheral heat transfer coefficients and endwinding heat transfer coefficient were measured by various model experiments and then, compared with other experimental results. Frame was the main heat transfer surface, load-side and fan-side surface were not thermally symmetric from the heat flux distribution analysis. Steady and unsteady temperature distributions were measured by real motor experiments. From the results, we knew that rotor surface temperature was higher than coil temperature and the hottest spot in the coil was loadside endwinding outside surface. We compared the simulation results with those of real motor test and the two results showed a good agreement.

• 전기학회논문지
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• 제61권8호
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• pp.1148-1152
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• 2012

The vegetable-based insulating oils are substitutes for mineral oils in oil-filled transformer. The important properties of vegetable insulating oil is their higher flash/fire point and biodegradability than conventional mineral oils. The large oil-filled transformer eliminate the risk of explosion and fire should the transformer fail and oil ignite owing to high flash/fire point of vegetable insulating oil. In addition, higher biodegradability of vegetable insulating oils can let the oil spill damage reduced. In this experiment, the real oil-filled transformers using mineral oil and vegetable oil have accelerated aging. After working on the 100% accelerated aging experiment were conducted comparing the transformer. The hottest-spot temperature using thermal coefficients were calculated to determin the degree of accelerated aging. As a result, apply mineral oil transformer in accordance with the accelerated aging life come to an end. In contrast, vegetable insulating oils showed the opposite characteristics. Vegetable insulating oil compared to the mineral oil are found to be an long life. As a result, the vegetable oil has a long-term stability.

• 한국표면공학회지
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• 제49권2호
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• pp.218-224
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• 2016

Thermal radiation pastes were prepared by dispersing carbon materials as fillers with a content of 1 weight percent in an acrylic resin. The kind of fillers was as follows; $25{\mu}m$ graphite, $45{\mu}m$ graphite, $15{\mu}m$ carbon nanotube(CNT), a 1:1 mixture of $25{\mu}m$ graphite and $15{\mu}m$ CNT, and a 1:1 mixture of $45{\mu}m$ graphite and $15{\mu}m$ CNT. Thermal emissivity was measured as 0.890 for the samples with graphite only, 0.893 for that with CNT only, and 0.892 for those containing both. After coating prepared pastes on a side of 0.4 mm thick aluminium plate and placing the plate over an opening of a box maintained at $92^{\circ}C$ with the coated side out, the temperatures on the uncoated side of the plates were measured. The samples containing graphite and CNT showed the lowest temperatures. The paste with mixed fillers was coated on the back side of the PCB of an LED module and thermal analysis was carried out using Thermal Transient Tester (T3ster) in a still air box. The thermal resistance of the module with coated PCB was measured as 14.34 K/W whereas that with uncoated PCB was 15.02 K/W. The structure function analysis of T3ster data revealed that the difference between junction and ambient temperatures was $13.8^{\circ}C$ for the coated case and $18.0^{\circ}C$ for the uncoated. From the infrared images of heated LED modules, the hottest-spot temperature of the module with coated PCB was lower than that of the uncoated one for a given period of LED operation.