• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.327-329
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• 1999

본 논문은 3차원 유한요소 프로그램을 이용한 농형 유도전동기의 정자장을 해석한 것이다. 2차원영역에서 해석하기 어려운 누설 인덕턴스를 3차원으로 해석하여 설계 파라미터 선정에 도움을 주고자 하였다. 유도전동기의 공극 자속밀도 분포와 누설 자속밀도 분포를 고찰하고 1[turn]의 coil에 의해 발생하는 자속의 량과 전동기 내부로 통과하는 자속의 량을 비교하여 누설 인덕턴스를 계산할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4381-4387
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• 2015

Ship hull is a compound curved shape and most of shipyards have been using gas heating method for the surface forming of steel plate. This traditional forming process have problems such as difficulties in heat input control and poor working conditions due to loud noise and air contamination. Recently, researches on automatic hull forming system have been conducted using high frequency induction heating method which have good control ability and favorable working environment. In this study, the induction heating simulation system for curved surface forming of steel plate was developed and induction heating experiments were performed. Based on the results of this study, efficient induction heating coil design and optimal heating conditions for the automatic hull forming system can be obtained.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.219-226
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• 2022

In this experimental study, the effect of continuously changing the position of electromagnetic force using several coils and a relay switch on fracture energy was investigated. Normal mortar and steel slag mortar specimens in which 50 % and 100 % of sand was replaced with steel slag were cast and exposed to electromagnetic field. The electric field was induced by one coil without a relay switch as an existing method and by partitioning the coil and continuously changing the position using a relay switch. The fracture energy was calculated from the load-vertical displacement curve obtained from the experiment and compared with each other. As a result of the experiment, it was confirmed that the method of partitioning the coil and changing the position of electromagnetic force by using a relay switch is effective in increasing the fracture energy even if the same amount of power is used.

• Journal of the Korean Society of Safety
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• v.38 no.1
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• pp.25-33
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• 2023

In this study, we determined the failure rate and fire status of electric motors widely used in domestic and industrial devices and analyzed the associated fire risks by identifying the electrical and temperature characteristics of electric motors under the normal and restrained operation modes in industrial sites and laboratories. A 2.2kW motor used for driving a conveyor during the vulcanization process in a rubber product manufacturing plant was employed as the study object and was exposed to a high- temperature environment as this motor is widely used in industrial sites. The current amplitude was 4.45-4.50 A during normal operation and 38.2-41.5 A during restrained operation due to the pinching of products and semi-finished products (i.e., 8.5 times higher than that during normal operation). The leakage current amplitude was 0.33 mA during both operation modes. The temperature of the workplace in summer was 42.38℃, indicating a poor environment for the installed motor. In the laboratory, the current and temperature of the coil inside a 3.7kW motor were measured under the restrained operation mode as performing measurements of the coil inside the motor in industrial sites is challenging. The current amplitude during normal operation was 3.5 A, whereas that during restrained operation for 30 s was 51.7-58.6 A, which is 14.8-16.7 times higher than that of normal operation. Moreover, the temperature of the motor coil increased from 22.9℃ to 101℃. Based on the experimental data, we derived the temperature increase formula according to the restrained operation time by performing a regression analysis and verified the time at which the temperature exceeded the stipulated limit for the insulation grade. The findings presented in this paper can be utilized to establish fire-prevention measures and perform safety management of motors of the same type or with a similar capacity.

• Journal of Microbiology and Biotechnology
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• v.18 no.3
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• pp.434-442
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• 2008

We observed that an inclusion body (IB) of recombinant ${\beta}$-galactosidase that was produced by the araBAD promoter system in Escherichia coli (E. coil) showed enzyme activity. In order to improve its activity, the lowering of the transcription rate of the ${\beta}$-galactosidase structural gene was attempted through competition between an inducer (L-arabinose) and an inducer analog (D-fucose). In the deep-well microtiter plate culture and lab-scale fermentor culture, it was demonstrated that the addition of D-fucose caused an improvement in specific ${\beta}$-galactosidase production, although ${\beta}$-galactosidase was produced as an IB. In particular, the addition of D-fucose after induction led to an increase in the specific activity of ${\beta}$-galactosidase IB. Finally, we confirmed that the addition of D-fucose after induction caused changes in the structure of ${\beta}$-galactosidase IB, with higher enzyme activity. Based on these results, we expect that an improved enzyme IB will be used as a biocatalyst of the enzyme bioprocess, because an enzyme IB can be purified easily and has physical durability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.6
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• pp.849-859
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• 1998

The heat generated in an induction motor is mostly dissipated through the frame. The study on the heat transfer characteristics of a newly manufactured finless TEFC(Totally Enclosed Fan Cooled) induction motor showed/that it had an unsuitable structure in view of the heat transfer. The angle of the cooling air flow was very large and the ribs disturbed the air flow and partially generated the wake region on the frame. In the wake region the temperature was very high. Thus the heat transfer coefficients were lower than those of the frame with fins. Also was investigated the heat transfer characteristics of the motor frame by installing various guide vanes in the fan-side end cap. An optimum heat transfer case was found and the average heat transfer coefficient of the frame was 70% higher and the average coil temperature measured by the resistance method was 9 deg. C lower than that of the frame which had no guide vanes.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.226-228
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• 2006

This paper presents the two lossless auxiliary inducors-assisted voltage source type half bridge(single ended push pull:SEPP) series resonant high frequency inverter for induction heated fixing roller in copy and printing machines. The simple high-frequency inverter treated here can completely achieve stable zero current soft switching (ZCS) commutation forwide its output power regulation ranges and load variations under constant high frequency pulse density modulation (PDM) scheme. Its transient and steady state operatprinciple is originally described and discussed for a constant high-frequency PDM control strategy under a stable ZCS operation commutation, together with its output effective power regulation charactertics-based on the high frequency PDM strategy. The experimenoperating performances of this voltage source SEPP ZCS-PDM series resonant high frequency inverter using IGBTs are illustrated as compared with computer simulation results and experimenones. Its power losses analysis and actual efficiency are evaluated and discussed on the basis of simulation and experimental results. The feasible effectiveness of this high frequency inverter appliimplemented here is proved from the practical point of view.

• Smart Structures and Systems
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• v.3 no.3
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• pp.385-403
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• 2007

The effectiveness of the newly developed smart passive control system employing a magnetorheological (MR) damper and an electromagnetic induction (EMI) part for seismic protection of base isolated structures is numerically investigated. An EMI part in the system consists of a permanent magnet and a coil, which changes the kinetic energy of the deformation of an MR damper into the electric energy (i.e. the induced current) according to the Faraday's law of electromagnetic induction. In the smart passive control system, the damping characteristics of an MR damper are varied with the current input generated from an EMI part. Hence, it does not need any control system consisting of sensors, a controller and an external power source. This makes the system much simpler as well as more economic. To verify the efficacy of the smart passive control system, a series of numerical simulations are carried out by considering the benchmark base isolated structure control problems. The numerical simulation results show that the smart passive control system has the comparable control performance to the conventional MR damper-based semiactive control system. Therefore, the smart passive control system could be considered as one of the promising control devices for seismic protection of seismically excited base isolated structures.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.241-248
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• 2005

The induction heating is more efficient for a plate bending because of its easy operation and control of working parameters compared with the heating by torch. In this study, a more efficient method was proposed for the prediction of plate bending. The existing analysis method using the axi-symmetric coil model could not handle the varying temperature during the heating and the forming process for curved plates like a saddle or a concave type curvature. The proposed method using some discrete steps in this study could overcome these difficulties and show more accurate, reasonable results in temperatures and deflections of fiat or curved plates. This method is composed of multi-disciplinary analyses such as an electro-magnetic analysis, a heat transfer analysis and a deformation analysis based on inherent strain approach.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.288-294
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• 2013

The diagnosis of motor failures using an on-line method has been the aim of many researchers and studies. Several spectral analysis techniques have been developed and are used to facilitate on-line diagnosis methods in industry. This paper discusses the first application of a motor flux spectral analysis to the identification of broken rotor bar (BRB) faults in induction motors using a multiple signal classification (MUSIC) technique as an on-line diagnosis method. The proposed method measures the leakage flux in the radial direction using a radial flux sensor which is designed as a search coil and is installed between stator slots. The MUSIC technique, which requires fewer number of data samples and has a higher detection accuracy than the traditional fast Fourier transform (FFT) method, then calculates the motor load condition and extracts any abnormal signals related to motor failures in order to identify BRB faults. Experimental results clearly demonstrate that the proposed method is a promising candidate for an on-line diagnosis method to detect motor failures.