• The Transactions of the Korean Institute of Power Electronics
• /
• v.16 no.6
• /
• pp.627-637
• /
• 2011

To cope with the high power density and low cost in switching power supply, this paper presents a novel planar transformer, which can regulate the leakage inductance of planar transformer used for LLC resonant converter. Modeling and analysis of a novel planar transformer are discussed in detail and a prototype 200W LLC resonant converter is tested to verify.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.165-168
• /
• 1999

The chaotic characteristics of partial discharge(PD), may seems to be stochastic and merely random, were investigated using the method to discern between chaos and random signal, e.g. correlation integral, Lyapunov characteristic exponents and etc. For the purpose of obtaining experimental data, computer aided partial discharge detecting system was used. While this method is very different from typical statistical analysis from the point of view of a nonlinear analysis, it can provide better interpretable criterion according to the time evolution with a degradation process in the same type insulating system.

• Proceedings of the KIEE Conference
• /
• 1998.07a
• /
• pp.250-253
• /
• 1998

This paper has proposed a method to analyze a 30 KVA superconducting generator using 3-dimensional FEM program. 3 kinds of 3D formulation methods are employed such as scalar potential in core region, reduced scalar potential in air region and T-${\omega}$ formulation in stator coil region. As results of the simulation, various parameters of the generator have been analyzed like air gap flux density, induced voltage, inductance, etc.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.2
• /
• pp.459-463
• /
• 2011

In this paper we reported the characteristics of 1 line, 2 lines and 3 lines-to-ground fault of matrix-type SFCLs (MFCLs) and the electromagnetic field distribution of reactors for MFCLs under the same cases of ground faults. To do this, we fabricated MFCLs with 6 reactors for 3 phases. Each reactor had the length of 270 mm and diameter of 80 mm. 6 reactors were made by Bakelite. We reported experimental results, including fault currents, fault voltages and magnetic field distribution according to phase differences between each phase. We confirmed that experimental results will be useful in next future plan for real power grid.

• The Journal of the Korea Contents Association
• /
• v.7 no.1
• /
• pp.124-130
• /
• 2007

A rectangular coaxial line is mainly utilized as a transition structure from a coaxial line to a rectangular waveguide. A TEM cell is also widely used to measure the EMC characteristics of a DUT. In order to understand the operations of a rectangular coaxial line and a TEM cell, it is essential to analyze the dispersion relations of a rectangular coaxial line and a TEM cell. In this paper, we present simple yet accurate dispersion relations of the TE and TM higher modes based on the TEM mode. Manipulating a mode-matching technique and a Green's function approach allows us to obtain the analytic dispersion equations of a rectangular coaxial line and a TEM cell. In our approach, a rectangular coaxial line is divided into four L-blocks and its electromagnetic fields representations are easily obtained with a superposition. To verify the convergence of our dispersion relations, we perform numerical computations and compare our results with those of FDTD.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.2
• /
• pp.179-185
• /
• 2015

The main objective of thermal design for a space-borne FPA(Focal Plane Assembly) is to provide stable thermal environment during imaging operation and thus maintain the image quality. An FPA must be maintained within its operating temperature range and cooled down to its initial temperature soon enough for the next imaging operation. This paper describes the study result on performing trade-off studies for FPA thermal design by using simplified thermal node analysis about FPA preliminary design. It also describes the verification results of the study by comparing thermal analysis results and trade-off study results. According to results, we can conclude that this approach is useful for simple and quick trade-off studies without thermal analysis based on thermal math models.

• Journal of Advanced Navigation Technology
• /
• v.26 no.4
• /
• pp.185-194
• /
• 2022

Avionics equipment requires various environmental conditions and performance during development, and as a countermeasure against such development risk, the worst-case circuit analysis(WCCA) is applied to predict perform preliminary performance analysis. WCCA calculates the maximum and minimum values by combining the parameter values of the relevant circuit after deriving the parameter values in consideration of the aging of the temperature and operating period at the component level. In this paper, the necessary matters for WCCA application are described. Chapter 2 describes the differences and characteristics of the WCCA techniques EVA, RSS, and Monte Carlo.Chapter 3 introduces the analysis process through the example circuit to introduce the actual analysis procedure. Chapter 4 describes the method of selecting an analysis technique for each condition of the analysis target. As a result of applying the procedures and analysis methods introduced in this paper when open, it was confirmed that preliminary performance analysis and part optimization design verification are possible.

• Journal of the Korean Vacuum Society
• /
• v.17 no.3
• /
• pp.189-194
• /
• 2008

Measurements with a Langmuir probe, which are the most often used procedures of plasma diagnostics, can disturb plasma flows and change its characteristics quite a little because the probe should be inserted into thermal flowing plasmas. In this study, we calculated the characteristics of thermal plasmas with and without the probe into an atmospheric argon free-burning arc numerically, and investigated aerodynamic and thermal disturbances with temperature and axial velocity distributions. For the modelling of thermal plasmas, we have made two governing equations, which are on the thermal-flow and electromagnetic fields, coupled together with a commercial CFD package and user-coded subroutines. It was found that thermal disturbances happened to both sides of the probe, before and behind, seriously. Due to the aerodynamic disturbance, we could find that there were the stagnation point in front of the probe and the wake behind it. Therefore, aerodynamic and thermal disturbances caused by the probe insertion should be considered to increase the reliability of the probe diagnostics.

• Geophysics and Geophysical Exploration
• /
• v.22 no.4
• /
• pp.186-194
• /
• 2019

Deterministic optimization, commonly used to find the geophysical inverse solutions, have its limitation that it cannot find the proper solution since it might converge into the local minimum. One of the solutions to this problem is to use global optimization based on a stochastic approach, among which a large number of particle swarm optimization (PSO) applications have been introduced. In this paper, I developed a geophysical inversion algorithm applying PSO method for the layered-earth resistivity inversion of the small-loop electromagnetic (EM) survey data and carried out numerical inversion experiments on synthetic datasets. From the results, it is confirmed that the PSO inversion algorithm could increase the inversion success rate even when attempting the inversion of small-loop EM survey data from which it might be difficult to find a best solution by applying the Gauss-Newton inversion algorithm.

• Journal of the Korean Geophysical Society
• /
• v.1 no.1
• /
• pp.41-50
• /
• 1998

Schlumberger soundings, dipole-dipole survey and electrical conductivity mappings were carried out inside and in front of the entrance of the Okmyung waste landfill in August, 1997 and January, 1998. Inside and in front of the landfill, 11 and 4 electrical soundings and 1 dipole-dipole survey were carried out, respectively. Electrical conductivities were measured at 164 points along the 4 lines in front of the entrance of the landfill. Interpretations of survey data show that low resistivity zones of 0.3∼3 Ωm extend down to 65 m depth from the surface in the 6th landfill, which indicates subsurface contamination by leachate and leachate level at 3∼6 m depth from the surface. In the 9th landfill, low resistivity zones below 2 Ωm appear at 11∼15 m depth from the surface, which indicates a very slim chance of subsurface contamination. On the other hand, electrical surveys and electrical conductivity mappings reveal low resistivities at shallow depths in front of the entrance of the landfill, indicating a high possibility of contamination of weathered zone in this area. It appears that southern part of this area close to the 6th landfill is more contaminated by leachate.