• KEPCO Journal on Electric Power and Energy
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• 제8권2호
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• pp.93-96
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• 2022

The boiler tubes of thermal power plants are exposed to harsh environment of high temperature and high pressure, and the deterioration state of materials rapidly increases. In particular, parent material and welds of the materials used are subjected to a temperature change and various constraints, resulting in deformation and its growth, resulting in frequent leakage accidents caused by tube failure. The power plant checks the integrity of boiler tubes through non-destructive testing as it may act as huge costs loss and limitation of power supply during power station shutdown period due to boiler tube leakage. However, the current non-destructive testing is extremely limited in the field to detect micro cracks. In this study, the ability of metal magnetic memory technique to detect flaws of size that are difficult to inspect by the visual or general non-destructive methods was verified in the early stage of their occurrence.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.67-73
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• 1997

A magnet for urban transit Maglev is designed, analyzed and experimented to evaluate and to improve its characteristic. FEM is also used to calculate magnetic field density, magnetic force, leakage flux and losses. Seven cases of magnets are analyzed and tested for verifying the calculated characteristics and for optimizing the shape. Using the results, an improved levitation magnet is proposed for the vehicle.

• 전자공학회논문지
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• 제54권7호
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• pp.49-54
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• 2017

본 연구에서 페라이트를 이용한 자기장 무선전력전송 안테나를 제안하였다. 기존에 추가접지가 있어야 자기장 무선전력전송이 가능하였던 점을 페라이트의 특성을 이용하여 추가접지 없이 자기장 무선전력전송이 가능하게 하였다. 페라이트는 자기장의 차폐효과가 있고 누설전력을 줄여주어 전송효율을 높여준다. 페라이트를 이용하여 자기장 무선전력전송을 위한 안테나를 제안하였고 실험을 통해 5W 자기장 무선전력전송 되는 것을 확인하였다. 본 논문에서 제안한 무선전력전송은 금속을 매개로하는 자기장 무선전력전송으로 사물인터넷 분야에 다양하게 응용 될 수 있다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.81-84
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• 1999

The purpose of this paper is to find the magnetic field distribution inside the motor in order to find out if the high-Tc superconducting tapes operate stably in actual motor operation. With this gola, magnetic field distribution in a detailed model of the actual motor was analyzed through F.E.M. (Finite Element Method). As a result, it has been proved that the high-Tc superconducting tapes can withstand 4 A of current with stability. 4 A was the amount of current needed to achieve 600 A ·turns which is required by the previous simulation aimed at developing this motor. Also, it has been observed that the flux damper reduces armature reactance during the motor operation and during load changes, helping the stable motor operation. But, it was observed that the flux damper generates loss by means of leakage flux and this decreases the output of the motor by about 5%.

• 한국정밀공학회지
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• 제22권3호
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• pp.29-37
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• 2005

In this study, the control of the free surface deformation of a magnetic fluid for the change in electromagnetic force is discussed. The free surface of magnetic fluid is formed by the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body force. Magnetic fluid in characteristics of fluid adjusted to the opposite direction of the gravity direction. Thus, the device of a magnetic fluid proposed the complete zero-leakage sealing, oscillator for surface control, boundary layer control, MHD, flow control, flow using magnetic levitation system and surface actuator. This study show the deformation of surface rise due to the intensity of the magnetic field and possibility of two-dimensional control of magnetic fluid through the feedback data of hall sensor.

• 전기학회논문지
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• 제61권4호
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• pp.606-611
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• 2012

The similarity, analogy and equivalence between the phenomenon due to electric and magnetic dipoles have been discussed in the open literature for different situations. Here we are presenting the numerical proof of the trajectory of leakage electric field due to a semi-infinite electric dipole layer in the external periphery and the electric field in the space between oppositely charged surfaces. The result is also valid for the fringing electric field of a parallel plate capacitor. The result is also proved to be a dual of Amp$\grave{e}$re's law in the electrostatics due to a semi-infinite electric dipole layer.

• 전기의세계
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• 제29권4호
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• pp.247-255
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• 1980

In this study, an application of Finite Element Method which, in principle, based on variational calculus has been presented for the two-dimensional analysis of magnetic flux distribution in the shell type core of single phase transformer. The necessary stationarity condition of energy functional and boundary conditions were determined under the assumptions that the electromagnetic field considered is stationary and that the effect of eddy current is negligible. In the process of application the domain of magnetic field was divided into triangle subsectional elements and then the matrix equations were constructed for the respective triangular element and for those of all after the manipulation of minimization process to the vector potential of magnetic field at the each vertex of the element. Furthermore the numerical computation for the equations was guided by the Gaussian Elimination Methods. As the results obtained, it is found that the aspect of magnetic flux distribution inside the core as well as the leakage flux profile at the vicinity of the inner leg of the core is not much different from the well-known distribution profile of magnetic flux, however, the procedure shows to possess the merit of the uniquely deterministic nature for the flux distribution at the desired points.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권4호
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• pp.152-160
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• 1999

A high speed motor has been generating a lot of attention due to its performance-more light, thin, short, compact than ordinary motors. But they have low efficiency with high frequency power source because of the iron losses which may produce too much heat as well as the copper losses occurred in the rotor windings. The Halbach array can generate the strong magnetic field systems without additional magnetic materials, therefore the iron losses can be removed. In this paper, the Halbach array is applied to the field system for the high speed motor, and three dimensional FEM is used to analyze the field of the Halbach array considering with the leakage flux. The measured values of flux density are also compared with the FEM analysis. And the magnetic characteristics of the Halbach array field system are compared with those of the conventional field systems such as slot-iron type, PM-iron type. Consequently, it is confirmed that the Halbach array field system is more suitable to the high speed motor because it has high flux density, sinusoidal flux distribution than others.

• 비파괴검사학회지
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• 제30권3호
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• pp.212-224
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• 2010

The usefulness of the magnetic camera for non-destructive testing of aging aircraft is discussed in this paper. The magnetic camera can be used f magnetic particle testing(MT), magnetic flux leakage testing(MFLT), eddy current testing(ECT) and penetration testing(PT). It measures the distribution of a magnetic field and visualizes the magnetic pattern. Near and far side cracks, fatigue, thickness degradation, and cracks under rivets have been detected. The possibility of quantitative evaluation was also examined. Using indirect experiments, we verified the detection ability of the sensor for cracks in titanium and advanced composite materials.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.170-172
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• 2000

This paper deals with the characteristic analysis of the flux damper with respect to the load, and the stability of Ag/Bi-2223 tapes in a high-Tc superconducting (HTS) synchronous motor. To find out the magnetic field distribution in a detailed model of the actual motor, the experimentally measured currents of the armature and the field windings are used as input parameters. The simulation results show that the flux damper shields the time varying field up to 10%, reduces armature reactance during the motor operation and during load changes, improving the stable motor operation. And it was observed that the flux damper generates loss by means of leakage flux, but this is not significant and it doesn't degrade the performance of the TS synchronous motor.