• Electrical & Electronic Materials
• /
• v.11 no.11
• /
• pp.17-21
• /
• 1998

The surface potential distribution on insulating polymers was measured by scanning of the probe of an electrostatic voltmeter. The measurements were done for two measured by scanning of the probe of an electrostatis voltmeter. The measurements were done for two cases. In the first case, it was measured on the free surface of insulating films which had been inserted between plane electodes after the removal of the upper brass disk electrode. In the second case, we measured the charging region between a circular and its opposing concentric ring electrodes after the removal of dc ramp voltage in air and nitrogen gas.

• Proceedings of the KIEE Conference
• /
• 1997.07e
• /
• pp.1776-1778
• /
• 1997

WIPS is a plasma device which has a wire anode, a coaxially-set cylindrical cathode, and aperture electrodes located in both ends of the cylinder. This electrode configuration forces the potential between the anode and the cathode to change logarithmically with radial direction. Since electrons are confined this logarithmic potential, the high-density plasma is produced even at a rather low anode voltage. In this paper we investigate characteristics of dc and pulse discharges, in which

• Journal of Power Electronics
• /
• v.11 no.4
• /
• pp.408-417
• /
• 2011

The plug-in hybrid electric vehicles (PHEVs) are specialized hybrid electric vehicles that have the potential to obtain enough energy for average daily commuting from batteries. The PHEV battery would be recharged from the power grid at home or at work and would thus allow for a reduction in the overall fuel consumption. This paper proposes an integrated power electronics interface for PHEVs, which consists of a novel Eight-Switch Inverter (ESI) and an interleaved DC/DC converter, in order to reduce the cost, the mass and the size of the power electronics unit (PEU) with high performance at any operating mode. In the proposed configuration, a novel Eight-Switch Inverter (ESI) is able to function as a bidirectional single-phase AC/DC battery charger/ vehicle to grid (V2G) and to transfer electrical energy between the DC-link (connected to the battery) and the electric traction system as DC/AC inverter. In addition, a bidirectional-interleaved DC/DC converter with dual-loop controller is proposed for interfacing the ESI to a low-voltage battery pack in order to minimize the ripple of the battery current and to improve the efficiency of the DC system with lower inductor size. To validate the performance of the proposed configuration, the indirect field-oriented control (IFOC) based on particle swarm optimization (PSO) is proposed to optimize the efficiency of the AC drive system in PHEVs. The maximum efficiency of the motor is obtained by the evaluation of optimal rotor flux at any operating point, where the PSO is applied to evaluate the optimal flux. Moreover, an improved AC/DC controller based Proportional-Resonant Control (PRC) is proposed in order to reduce the THD of the input current in charger/V2G modes. The proposed configuration is analyzed and its performance is validated using simulated results obtained in MATLAB/ SIMULINK. Furthermore, it is experimentally validated with results obtained from the prototypes that have been developed and built in the laboratory based on TMS320F2808 DSP.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.21 no.1
• /
• pp.28-34
• /
• 2007

In this research, the characteristics of the DC discharge that was the logical gate input of discharge logic gate PDP newly proposed was considered. The logical output is induced by controlling the potential difference of inter-electrode according to the discharge path in the discharge logic gate. From the experimental result the discharge time lag was shortened to 1/3 and the voltage has decreased to 1/2 in the case to apply priming discharge for improving stability of these DC discharges compared with the case when it is not applied. Moreover, after the priming discharge ends, the space charge generated by this discharge influences it up to about $30[{\mu}s]$. And, as a measured result of the influence that the space charge exerts on the DC discharge with the change in time and spatial distance, it has been understood that there is a possibility that going away spatially can slip out the influence of the discharge easily as for going away from the discharge time-wise. Therefore the conclusion that the discharge logic gates of each scanning electrode can be operated independently is obtained.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.4 no.2
• /
• pp.67-74
• /
• 2008

Entering the 21st century, the primary influence leading world economy have been shifting. U.S. economy has seemed to slow down, Japan and EU are also in same situation. But China have started to lead Asia economy and expended to the World. According to Goldman Sachs Group, "The 21st century will be a era of Brics because of their enormous territory, a large population and abundant natural resources." We have to more focus on China because China have directly effect on Korean market and have a great potential market opportunity for our industries. However, this report mentioned above didn't carefully deal with a field of information and technology(from here IT), Digital contents consumption wasn't mentioned at all. Now Digital Contents (from here 'DC') emerge as new value creator and actually Korea has been a dominant in IT industries and is leading Digital contents market in China. This phenomenon is called as 'Korean wave (Han-Ryu)'. Many researchers have studied about 'Korean wave(Han-Ryu)' focusing on the economic effect but Korean DC industries need to build specifical strategies for exporting Korean DC to China market. Therefore, purpose of this study is following : Firstly, to analyze environment of DC in China and competitive advantages of it. Secondly, to compare ICAI (Industrial Comparative Advantage Index) according to a kind of DC. Finally, to make an analysis of China consumer's attitude to DC. This study will give much implication for Korean DC industries to enter China market.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.55 no.12
• /
• pp.529-535
• /
• 2006

In DC tracking power supply system, ground faults are currently detected by the potential relay, 64P. Though 64P relay detects ground fault, it cannot identify the faulted region which causes long traffic delays and safety problem to passengers. A new ground fault protective relay scheme, ${\Delta}I$ ground fault protective relay, that can identify the faulted region is presented in this paper. In ${\Delta}I$ ground fault protective relaying scheme, ground fault is detected by 59, overvoltage relay, which operates ground switch installed between the negative bus and the ground. It preliminarily chooses the faulted feeder after comparing the current increases among feeders and trips the corresponding feeder breaker. After some time delay, it then recloses the breaker if it finds the preselected feeder is not the actual faulted feeder. Whether or not the preselected feeder is the actual faulted feeder is determined by checking the breaker trip status in the neighboring substation in the direction of the tripped breaker. If the corresponding breaker in the neighboring substation is also tripped, it finally judges the preselected feeder is actually a faulted feeder. Otherwise it recloses the tripped breaker. Its algorithms is presented and verified by EMTP simulation.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.12
• /
• pp.1964-1969
• /
• 2012

This paper presents to verify the selective grounding fault protective relaying technique for the ungrounded DC traction power supply system. This system selectively blocks fault section when grounding fault occurred. In order to perform this verification, field test facilities have been installed on Oesam substation and Worldcup-Stadium substation, and field test process has been suggested. Also, selective grounding fault protective relaying components and rail voltage reduction device have been tested with the various trial examinations. In order to compare and evaluate performance of the selective grounding fault protective relaying function, field test system was modeled and the system fault simulation results were compared and evaluated with the field test result. Performance of selective grounding fault protective relaying function was evaluated with the above-mentioned process, and the fact that the system recognizes fault section irrespective of insulation between rail and ground and fault resistance from grounding fault.

• Journal of the Korean Society for Railway
• /
• v.7 no.4
• /
• pp.412-417
• /
• 2004

In urban rail transit systems, ground faults in the DC traction power supply system are currently detected by the potential relay, 64P. Though it detects the fault it cannot identify the faulted region and therefore the faulted region could not be isolated properly. Therefore it could cause a power loss of the trains running on the healthy regions and the safety of the passengers in the trains could be affected adversely. Two new ground fault protective relay schemes that can identify the faulted region are presented in this paper. A current limiting device, called Device X, is newly introduced in both system, which enables large amount of ground fault current flow upon the positive line to ground fault. One type of the relaying schemes is called directional and differential ground fault protective relay which uses the current differential scheme in detecting the fault and uses the permissive signal from neighboring substation to identify the faulted region correctly. The other is called ground over current protective relay. It is similar to the ordinary over current relay but it measures the ground current at the device X not at the power feeding line, and it compares the current variation value to the ground current in Device X to identify the correct faulted line. Though both type of the relays have pros and cons and can identify the faulted region correctly, the ground over current protective relaying scheme has more advantages than the other.

• Journal of Electrical Engineering and Technology
• /
• v.11 no.4
• /
• pp.905-914
• /
• 2016

This paper proposes a new phase current reconstruction technique for interleaved three-phase bidirectional dc-dc converters using a single current sensor. In the proposed current reconstruction algorithm, a single current sensor is employed at the dc-link, and the dc-link current information is sampled at either the peak or valley point of the pulse-width modulation (PWM) carriers regularly. From the obtained current information, all phase currents are reconstructed in a single PWM cycle. After that, the digital current controller is applied to achieve current balancing in each phase. Compare to the previous multiple current sensor method, the proposed strategy reduces the number of the current sensors in the interleaved three-phase bidirectional converter as well as reducing potential current sensing error caused by non-ideal characteristics of the multiple current sensors. The effectiveness of the proposed method is verified from the experiments based on a 3kW three-phase bidirectional converter prototype for the automotive battery charging application.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.465-465
• /
• 2010

Cut off probe, the efficient method, can measure the plasma parameters like the plasma electron density and the electron temperature. Plasma potential is also one of the important parameters in plasma processing but cannot be measured by cut off probe yet. Thus we developed method to measure plasma potential by focusing on relation between bias on a tip and sheath around tip. The system consist of a ICP(Inductive Coupled Plasma) source, a Network analyzer and a bias tee that can be bridge apply DC voltage on the cut off probe tip. Plasma potential is identified by using this system. The results corresponded well with the measured results by single langmuir probe(SLP).