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한정호(J H Han),정한진(H J Jung),장민영(M Y Jang),권영안(Y A Kwon) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.10
Speed and torque controls of induction motors are usually attained by the application of position and speed sensors. However, speed and position sensors require the additional mounting space, reduce the reliability in harsh environments and increase the cost of a motor. Therefore, many studies have been performed for the elimination of speed and position sensors. This paper investigates an improved sensorless control of an induction motor. The proposed control strategy utilizes the reactive power for estimating the speed of a sensorless induction motor. The proposed algorithm is verified through the simulation and experimentation.
가공열처리에 의한 Alloy 600 재료의 결정립계특성 변화와 입계부식 및 1차측 응력부식균열 거동
김진,한정호,이덕현,김영식,노희숙,김근홍,김정수,Kim, J.,Han, J.H.,Lee, D.H.,Kim, Y.S.,Roh, H.S.,Kim, G.H.,Kim, J.S. 한국재료학회 1999 한국재료학회지 Vol.9 No.9
가공열처리에 의한 결정립계조절 개념을 이용하여 Alloy 600 재료의 결정립계특성과 부식특성을 조사하였다. 가공열 처리에 따른 결정립계특성 변화를 EBSP로 분석하였으며, 결정립계특성 변화가 입계부식 및 응력부식균열 거동에 미치는 영향을 평가하였다. 가공열처리 반복에 따른 각 단계에서의 CSL 입계의 분율 변화가 두드러지지는 않았으나, 상용재료에 비하여 CSL 분율이 약 10% 이상 향상된 결과를 얻었다. 결정립계특성 변화에 따라 입계부식 저항성이 현저하게 증가하였으나, 1차측 응력부식균열 특성에 있어서는 가공열처리를 반복할수록 파단시간과 최대하중이 감소하고 평균 균열성장속도가 증가하였으며 2차 균열이 억제되는 결과를 얻었다. 결정립계의 \`fine tuning\` 기구가 이러한 부식거동변화에 작용한 것으로 해석할 수 있었다. Grain boundary characteristics and corrosion behavior of Alloy 600 material were investigated using the concept of grain boundary control by thermomechanical treatment(TMT). The grain boundary character distribution (GBCD) was analyzed by electron backscattered diffraction pattern. The effects of GBeD variation on intergranular at tack(JGA) and primary water stress corrosion cracking(PWSeC) were also evaluated. Changes in the fraction of coinci dence site lattice(CSL) boundaries in each cycle of TMT process were not distinguishable, but the total eSL boundary frequencies for TMT specimens increased about 10% compared with those of the commercial Alloy 600 material. It was found from IGA tests that the resistance to IGA was improved by TMT process. However, it was found from PWSCC test that repeating of TMT cycles resulted in the gradual decrease of the time to failure and the maximum load due to change in grain boundary characteristics, while the average crack propagation rate of primary crack increased mainly due to suppression of secondary crack propagation. It is considered that these corrosion characteristics in TMT specimens is attributed to 'fine tuning of grain boundary' mechanism.
레이저 표면열처리가 Zircaloy-4 합금의 산화에 미치는 영향
한정호,임갑순,석호천,정용환,이덕현 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.8
The effect of heat treatment on the oxidation behavior of Zircaloy-4 plates was investigated in 400 to 600℃ steam for alpha-annealed, beta-quenched, and laser surface beta-treated samples. It was observed that the laser treatment resulted in the formation of surface layer of 40∼50㎛ thick beta-treated structure on the mass of alpha-annealed plates, and the microstructure of laser treated layer was much finer than those of alpha-annealed and beta-quenched samples. The corrosion resistance of laser treated Zircaloy was found to be superior to other two samples in a1l the temperatures. At 600 ℃, the corrosion rate was changed from cubic (W=kt^(1/3)) to linear rate(W=kt) after about 7 hour exposures. The marked improvement in corrosion resistance of laser treated samplers is thought to be due to the change of the second phase particle distribution. The coarse and discrete particles in the alpha-annealed structure changed to the fine and chain-like particles in the laser heat treated samples. In this study, the structure of oxide layer was observed to be only one type of monoclinic ZrO₂.