• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.57 no.4
• /
• pp.437-443
• /
• 2008

We have developed an evaluation technique for both ratio error and phase displacement of current transformer (CT) comparator by using the precise standard capacitors and resistors. By applying this technique to equivalent circuit of CT comparator evaluation system, we can obtain the calculated and measured ratio errors (or phase displacements) in the CT comparator. Thus we can evaluate ratio errors and phase displacement of CT comparator by comparing the calculated and measured ratio errors (or phase displacements). The method was applied to CT comparator under test with the ratio errors and phase displacement ranges of $0{\sim}{\pm}10%$ and $0{\sim}{\pm}7.5$ crad, respectively. Finally we have compared the ratio error and phase displacement of the CT comparator obtained in this method with specifications of two companies.

• Korean Journal of Construction Engineering and Management
• /
• v.15 no.6
• /
• pp.105-112
• /
• 2014

The objective of this study is to examine the relationship between the degree of business diversification of a construction company and two of the indicators that represent financial stability, namely, a current ratio and a debt ratio, in order to draw policy implications. The current ratio and the debt ratio were used as variables that represent financial stability of a construction company. Berry-Herfindahl Index was used to measure the degree of business portfolio diversification of a construction company. For the analysis, quarterly time series data were retrieved from the financial information disclosure system of Korea's Financial Supervisory Service for the period between the first quarter of 2001 and the third quarter of 2013. The analysis results showed that a higher current ratio and a debt ratio led to a greater extent of business diversification. A higher level of business diversification led to a higher current ratio and a lower debt ratio. It was also shown that the impact of business diversification on the current ratio and the debt ratio outweighed the impact of changes in the current ratio and the debt ratio on business diversification. Meanwhile, an increase in the level of business diversification showed a quite positive effect as it raised the current ratio and lowered the debt ratio of a construction company. These findings suggest that diversification of business portfolio is essential for construction companies to strengthen their financial stability.

• Journal of the Korean Society for Railway
• /
• v.14 no.5
• /
• pp.404-410
• /
• 2011

In AC feeding system, the fault location is calculated by using ratio of current absorbed in the neutral point of AT(Automatic Transformer) or by measuring reactance. In this way, however, an estimation error can be happened due to the many reasons. In addition, for measuring currents in the neutral point of AT, other measuring devices and communication equipments are additionally required. In order to solve the disadvantages, this paper suggests a novel technique using the distribution ratio of catenary current. The proposed technique uses existing protective relays and measures catenary current. With the measured data, we can calculate the distribution ratio of catenary current and determine fault location. Through the simulated results, we derived the correlation between current ratio and fault location. Using this technique, additional equipments and expenses can be reduced. Besides, fault location can be determined more correctly.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.33 no.1
• /
• pp.31-36
• /
• 2020

An investigation was conducted to determine whether the ratio of the fluid to the charged particles affects the panel reflexibility rate and the drifting current flowing in the panel, in electrophoretic-based electronic paper. In this regard, three panels were produced in this study with the ratio of the charged particles to the fluid set as 1:5, 1:1, and 5:1. Each sample was driven using an identical input pulse, for which the current flowing in the panel and the output voltage of the photodiode were measured for the panel reflexibility rate. Consequently, the drifting current initially exhibited a peak value and a saturated value at a later point. This value was proportional to the ratio of the charged particles, and it was similar to this ratio when it is higher than 1:1. The output voltage of the photodiode due to the panel reflexibility rate was proportional to the ratio of the charged particles. However, the response speed decreased if the ratio was higher than 1:1. It is expected that the results of this study will contribute to the analysis of the charging of charged particles in electrophoretic-based electronic paper, and the selection of an appropriate concentration.

• Journal of the Korean Solar Energy Society
• /
• v.29 no.5
• /
• pp.73-80
• /
• 2009

A tidal current turbine is designed and analyzed numerically by using blade element momentum theory. The rated power has a limitation because the diameter of the tidal current turbine cannot exceed the depth of sea water. This study investigates a horizontal axis tidal-current turbine with a rated power of 500 kW. NACA-6 series laminar foil shape is used for basic airfoil along the blade span. The distributions of chord length and twist angle along the blade span are obtained from the hydrodynamic optimization procedure. Prandtl's tip loss correction and angle of attack correction considering the three-dimensional effect are applied for this study. The power coefficient curve shows maximum peak at the rated tip speed ratio of 6.0, and the maximum torque coefficient is developed at the tip speed ratio of 4. The drag coefficient reaches about 0.85 at the design tip speed ratio.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.9 no.2
• /
• pp.110-116
• /
• 2009

The prominent advantages of Dual Material Surrounding Gate (DMSG) MOSFETs are higher speed, higher current drive, lower power consumption, enhanced short channel immunity and increased packing density, thus promising new opportunities for scaling and advanced design. In this Paper, we present Transconductance-to-drain current ratio and electric field distribution model for dual material surrounding gate (DMSGTs) MOSFETs. Transconductance-to-drain current ratio is a better criterion to access the performance of a device than the transconductance. This proposed model offers the basic designing guidance for dual material surrounding gate MOSFETs.

• Progress in Superconductivity and Cryogenics
• /
• v.15 no.4
• /
• pp.34-38
• /
• 2013

According to the increase of electric consumption nowadays, power system becomes complicated. Due to this, the size of single line-to-ground fault from power system also increases to have many problems. In order to resolve these problems effectively, an Superconducting Fault Current Limiter(SFCL) was proposed and continuous study has been done. In this paper, an SFCL was combined to the neutral line of a transformer. An superconductivity has the characteristics of zero resistance below critical temperature. because of this, SFCL has nearly zero resistance. so we connecting SFCL to neutral line will not only have any loss in the normal operation but also have the less burden of electric power because of only limiting the initial fault current. We analyzed the characteristics of current, voltage according to the changes of turn ratio of 3 phase system in case of combinations of an SFCL to the neutral line. It was confirmed that the limiting rate of initial fault current by the increase of turn ratio was reduced.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.5
• /
• pp.992-997
• /
• 2016

This paper analyzes the deviation of tunneling current for the ratio of top and bottom gate oxide thickness of short channel asymmetric double gate(DG) MOSFET. The ratio of tunneling current for off current significantly increases if channel length reduces to 5 nm. This short channel effect occurs for asymmetric DGMOSFET having different top and bottom gate oxide structure. The ratio of tunneling current in off current with parameters of channel length and thickness, doping concentration, and top/bottom gate voltages is calculated in this study, and the influence of tunneling current to occur in short channel is investigated. The analytical potential distribution is obtained using Poisson equation and tunneling current using WKB(Wentzel-Kramers-Brillouin). As a result, tunneling current is greatly changed for the ratio of top and bottom gate oxide thickness in short channel asymmetric DGMOSFET, specially according to channel length, channel thickness, doping concentration, and top/bottom gate voltages.

• Journal of the Korean Electrochemical Society
• /
• v.12 no.4
• /
• pp.317-323
• /
• 2009

Theoretical calculations for the secondary current distributions for the electrode with a projection part in electroplating were performed. Two kinds of electrodes were considered. One is a electrode with the overall conducting surfaces(Case 1) and the other is an electrode in which only a projection part has a conducting surface(Case 2). The effects of applied potential, the ratio of ion exchange current to conductivity, $\xi$ and the aspect ratio on the current distribution were examined. The increase of applied current or the value of $\xi$ decreased the uniformity of current distribution. The small value of aspect ratio resulted the more uniform current distribution and Case 2 showed the better uniformity than Case 2. When this model was applied into an electrode with various projection parts, the local current distribution along the electrode surface were obtained successfully. In this case, the decrease of $\xi$ also increase the uniformity of current distribution as seen previously.

• Journal of Welding and Joining
• /
• v.21 no.1
• /
• pp.48-53
• /
• 2003

The object of this study is to examine the effect of short circuit time ratio (SCTR) and current rise delay time (Td) on the spatter generation at low and medium current range in $CO_2$ welding. The spatter was evaluated by the weight generated in the welding of bead-on-plate for 30 seconds (3 times). Td was varied by order of 0, 0.4, 0.8 and 1.2 msec. At each Td, the short circuit time ratio was varied by the output voltage of the welding power source. In the low current range, it was found that the optimum SCTR was 20~25%, and the minimum spatter generation weight was obtained in the case of Td=0.4msec and SCTR=22% even though the remarkable difference was not showed by the application of Td. In the medium current range, it was confirmed that the arc was stable though the SCTR was increased from 20% to 40% by the control of current wave. Spatter generation weight depended on the variation of Td, and the lowest value of spatter generation weight occurred at Td=0.8~1.2msec.