• Journal of Advanced Marine Engineering and Technology
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• 제39권1호
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• pp.68-74
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• 2015

본 논문은 정격속도 이상의 고속 영역에서 운전되는 스위치드 릴럭턴스 발전기의 효율 개선에 대하여 기술한다. 전류 형상은 발전기 손실에 큰 영향을 미치기 때문에 전류 모양을 조정함으로서 시스템 효율이 개선될 수 있다. 풍력 또는 소수력 발전과 같이 속도 범위가 넓은 경우 정격속도 이상에서도 최적의 전류 형상을 얻을 수 있도록 스위칭각 조정 방법이 제시된다. 제시된 방법을 검증하기 위해 실험장치가 구성되고, 이론의 가능성이 시뮬레이션과 실험결과에 의해 검증된다.

• 한국정밀공학회지
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• 제20권1호
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• pp.43-49
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• 2003

In this study, micro electrochemical machining method was introduced for accomplishment the fabrication technology of functional parts and smart structures using the Ni-Ti shape memory alloy. From the experimental result, the micro part which has very fine surface could be achieved by use of micro electrochemical process with point electrode method. Concretely, the optimal performance of micro electrochemical process in Ni-Ti SMA was obtained at the condition of approximately 100% of current efficiency and high frequency pulse current. That is, much finer surface integrity and shape memory effect can be obtained at the same condition mentioned above.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권1호
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• pp.59-63
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• 2000

For the Mo-tip field emitter array, the method by which the geometrical structure of the gate insulator wall could be modified in order to improve field emission properties(turn-on voltage and gate leakage current). The device having a gate insulator of complex shape, which means the combined geometrical structure with round shape made by wet etching and vertical shape made by dry etching processes, was fabricated and the field emission properties of the three kinds of devices were compared. As a result, the electric field applied to tip apex could be increased and gate leakage current could be decreased by employing the gate insulator having geometrical wall structure of mixed shape. Finally, the obtained empirical results were analyzed by simulation of electric field distribution at/near the tip apex and gate insulator using SNU-FEAT simulator.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.529-532
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• 2003

Quench behavior of resistive superconducting fault current limiters (SFCLs) with various pattern shapes was investigated. The pattern shapes employed were meander, bi-spiral, and spiral shapes of identical line width, gap and margin. SFCLs were fabricated from YBCO thin films grown on two-inch diameter $Al_2O_3$ substrates under the same conditions. Resistance rise of current limiting elements was low at a spiral shape before the whole quench completion, which may act as a disadvantage for simultaneous quench in serial connection between current limiting elements, but the temperature tended to have similar values at higher voltages. On the other hand, bi-spiral shape was severe at insulation level between current limiting lines. When these aspects were considered, we concluded that a meander shape was appropriate to design for a resistive SFCL based on thin films except the concentration of electric field at edge areas of strip lines.

• 비파괴검사학회지
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• 제23권6호
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• pp.622-634
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• 2003

This paper is concerned with a computational method for recovering a crack shape of steam generator tubes of nuclear plants. Problems on the shape identification are discussed arising in the characterization of a structural defect in a conductor using data of eddy current inspection. A surface defect on the generator tube ran be detected as a probe impedance trajectory by scanning a pancake type coil. First, a mathematical model of the inspection process is derived from the Maxwell's equation. Second, the input and output relation is given by the approximate model by virtue of the hybrid use of the finite element and boundary element method. In that model, the crack shape is characterized by the unknown coefficients of the B-spline function which approximates the crack shape geometry. Finally, a parameter estimation technique is proposed for recovering the crack shape using data from the probe coil. The computational experiments were successfully tested with the laboratory data.

• 한국전기전자재료학회논문지
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• 제28권8호
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• pp.539-543
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• 2015

At present, the development of a detection device in order to prevent accidents due to wire deterioration in the distribution lines is required. Distribution line is not possible to check the internal state in a normal way because it is covered with the coating. Accordingly, various eddy current techniques that is the non-destructive test (NDT) techniques have been applied to solve this problem. In this paper, we have seen examining the characteristic change of the eddy current sensor according to the simplified shape of the sensor in order to solve the problems for the simplified shape that is generated when the simulation for the shape of the eddy current sensor.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 추계학술대회논문집 - 한국공작기계학회
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• pp.320-325
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• 2000

This study was performed to investigate the electro-chemical-machining (ECM) characteristic of Ni-Ti Shape Memory Alloy (SMA). From the experimental results, we could gain optimal electro-chemical conditions to bound with lesser machining effect and better surface roughness than any other machining methods to workpiece at the same time. At these conditions, current efficiency was, for especially ECM working of Ni-Ti SMA, approximately 100% and high frequency pulse current was detected.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1142-1147
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• 2002

For the evaluation of the DC motor noise and vibration, usually it is rely on human feeling because some kinds of noise are not definitely represented by measurement Instrument such as sound meter. But when we consider time signal of the noise and vibration. It is possible to represent them. And in this paper. it is suggested to study output current shape of the motor because it Is the source to make speed and torque variation of the motor. If the current shape is not stable. it makes operating state of the motor unstable and produces noise and vibration. By analyzing signal at time and frequency of noise and vibration and current shape. it is possible to automation of the noise and vibration measurement in the Production line.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1994년도 춘계학술대회 논문집
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• pp.42-45
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• 1994

In this paper, we will report on the effect of the pointed end shape of an electrode, discharge energy, pulse width and discharge current on machining characteristics. The results obtained are as tollows: 1)As the discharge Energy increases, the diameter and the depth of the discharged crater becomes larger and deeper. 2) The discharge energy is not constant during discharge but varies depending on the pointed end shape of th8 electrode. 3) The shape of crater depends on the pulse width and discharge current.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.185-189
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• 2003

The purpose of this study is to obtain the optimal operating condition of conduction cooled taper shape high-temperature superconductor (HTS) current lead operated in current sharing mode. In our previous study, we discovered that the optimal operating condition of constant cross-section area HTS current lead is in the current sharing state, and in optimal condition, the temperature gradient at warm end is not zero. The analysis result of taper HTS current lead is quiet similar to the constant area HTS current lead. The minimum dissipation of taper HTS current lead is not influenced by taper angle, however the optimal operation condition is varied with taper angle.