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강대하,노일수,Kang, Dae-Ha,Roh, Il-Soo 한국마린엔지니어링학회 2006 한국마린엔지니어링학회지 Vol.30 No.8
In this study capacitance and dielectric loss factor were measured with low-voltage signal and the simulation of equivalent circuits for the data was conducted. As the result it was shown that the equivalent circuit model considered the grain-boundary structure with semiconducting layer, dielectric layer and depletion layer was well approximated with the observed data. Various parameters were determined by a optimum curve-fitting method and could be used to analyze the characteristics of varistor. It also seems that the proposed equivalent circuit model will be adopted for other BL type varistors.
강대하(Dae-Ha Kang),김원희(Won-Hee Kim),이영식(Yuong-Sik Lee),손정대(Jung-Dae Son),박윤동(Yoon-Dong Park),박상호(Sang-Ho Park) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
In this study reduction effects of magnetic field were analyzed using multi-conductor method in analysis of shield. The method can be effective in the analysis because of reducing the amount of allocated memory and computing time. And also the method can be applicable to analysis of the induced current distributions and skin effect in shield. The results of the analysis are presented.
도전성 및 자성 차폐체의 차폐효과 해석과 차폐인수 산정
강대하(Dae-Ha Kang) 한국조명·전기설비학회 2013 조명·전기설비학회논문지 Vol.27 No.10
In this study the method based on flux linkage in cell was introduced in calculation of eddy currents by cell method. According to this method eddy current distribution and the loss can be evaluated and since the shielding effectiveness by flux cancelation of eddy current can be analyzed, this method is applicable to design of conductive shield. And also the formula of shielding factor were so deduced as to be applicable to finite-width infinite-length shielding sheets and infinite-length underground cable shield. These formula are adaptable to magnetic materials as well as conductive materials. As the results of calculation in model shields are follows.. In case of finite-width infinite-length shielding sheet, shielding effectiveness increases with increasing of conductivity. In case of infinite-length underground cable shield, the effectiveness become higher with increasing of permeability. Especially the effectiveness is very high in materials with both high conductivity and permeability in underground cable shield.
강대하(Dae-Ha Kang),박상호(Sang-Ho Park),노일수(Il-Soo Rho),최필수(Phil-Soo Choi),심재구(Jae-Gu Sim) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
In this study dielectric and piezoelectric properties of fluoro-rubber/PZT composite were measured and analyzed by composite's laws. As the results the Rayleigh's equation was well consistent with experimental results qualitatively and the Bruggeman's equation was more well consistent with the experimental results for volume fraction of PZT quantitatively.
강대하(Dae-Ha Kang),이영식(Yong-Sik Lee),김부규(Bu-Gyu Kim) 한국조명·전기설비학회 2009 조명·전기설비학회논문지 Vol.23 No.5
본 연구에서는 임의의 각도로 분기되어 있는 전력선로 근방의 자계를 유도하여 정식화 하였으며 이 공식을 이용함으로써 그 자계 계산을 쉽게 할 수 있다. 이 공식들은 분기선로가 있는 배전선로의 설계 시 검토자료로서 활용할 수 있을 것으로 생각된다. 예로서 자계요소에 관한 공식들을 분기선로가 있는 3상 배전선로 모델에 적용하여 메틀랩 프로그램에 의해 계산하였으며 그 결과를 제시하였다. 그 분석결과를 요약하면 다음과 같다. 합성자계는 분기각이 작고 관측점의 높이 z가 낮으면 전 y-축상에 걸쳐 By 요소가 지배적이다. 이 합성자계는 분기각 α=π/2[rad]의 경우 Bx의 영향을 크게 받는다. 또한 이 합성자계는 전력선 높이와 같은 전선로 근방에서 Bz요소가 지배적이며 분기각이 α?π/2[rad]의 경우에는 y축의 분기전선 위치에서 매우 큰 값을 나타낸다. In this study magnetic fields near electric power lines with branch lines which have a arbitrary angle were derived and formulated by dipole antenna theory and could be calculated easily using the formula. It seems that those formula could be applicable to the consideration of magnetic fields during the design of distribution lines with branch lines .As an example those formulated equations on elements of magnetic fields were applied to a model of 3 phase distribution lines with branch lines and calculated by Matlab programs and the results were presented. The analyzed results are follows. The resultant magnetic field is dominated by the componant By all over y-axis in the case of the smaller branched angle and the lower observed point z. In case of α=π/2[rad], the resultant field is affected by the componant Bx . The resultant field is dominated by the componant Bz at the vicinity of the power lines and it shows very large value at the bramch line position of y-axis in case of α?π/2.
강대하(Dae-Ha Kang),김원희(Won-Hi Kim),이영식(Young-Sik Lee),심재구(Jae-Gu Shim),김휘칠(Hui-Chil Kim) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
In this study multi-conductor method was introduced as a method to analyze the shielding effects of shields and the calculation algorithm of magnetic fields was presented. For applying this method the correct formulation of mutual inductance between 2 parallel line-conductors with any length was deduced and the calculation method of magnetic field for applying to multi-conductors with any direction was presented. The magnetic fields and induced currents in shield were calculated by Matlab programs.
4륜구동 차량의 구동토크 배분이 조종 안정성에 미치는 영향
강대하(Dae Ha Kang),이진화(Jin Hwa Lee),김상섭(Sang Sup Kim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
This paper presents a vehicle dynamics model with detailed drive train model to analyse handling performance of 4WD Vehicle vehicle with varying torque distribution. The functional suspension model was used to derive a full vehicle dynamics model with kinematic and compliance characteristics of suspensions. The drive train is modeled with front, rear and center differential gears and soft flexibility. A wheel dynamics model with tire relaxation effects was used for more realistic simulation. Several simulation results of 4WD vehicles demonstrate the effectiveness of current model to evaluate torque distribution effects on handling performance.
강대하(Dae-Ha Kang) 한국조명·전기설비학회 2011 조명·전기설비학회논문지 Vol.25 No.6
Purpose of this study is to find the mitigation method of magnetic field by finite length multi-conductors such as indoor distribution lines and to be applicable to design of the distribution lines. For this purpose, exact formula about the components B<SUB>x</SUB>, B<SUB>y</SUB>, B<SUB>z</SUB> of magnetic field need in case of straight line-conductor with finite length forward any direction. In this study simple formula of the components were deduced and by using these formula magnetic fields for various models of line-configurations were calculated. And also a calculation method of induced currents in conductive shield was presented and using this method, programing of calculation is relatively easy and calculation time is short. The magnetic field after cancellation by these induced currents was calculated. All of calculations were performed by Matlab 7.0 programs. Through the calculation results it could be obtained followings for the mitigation of magnetic fields. The separation between conductors ought to be smaller than smaller as possible. In case of 3-phase, delta configuration is more effective than flat configuration. In case of 3-phase, unbalanced currents ought to be reduced as possible.. In case of more than two circuits of 3-phase, adequate locations of each phase-conductor such as rotating configuration of 3-phase conductors are more effective. The magnetic shielding effect of the conductive shielding sheet is very high.