• Journal of Drive and Control
• /
• v.15 no.4
• /
• pp.1-10
• /
• 2018

Spool displacement of a direction control valve is the standard signal to measure the bandwidth frequency of the direction control valve. When the spool displacement signal is not available, it is suggested in this study to use the metering hydraulic line as an alternative way to measure - 90 degree phase bandwidth frequency of the hydraulic direction control valve. Dynamics of the hydraulic line is composed of inertia, capacitance, and friction effects. The effect of oil inertia is dominant in common hydraulic line dynamics and the line dynamics is close to a derivative action in a range of high frequency; such as a range of bandwidth frequency of common directional control valves. Phase difference between spool displacement and line load pressure is nearly constant as a valve close to 90 degree. If phase difference is compensated from the phase between valve input and pressure, compensated phase may be almost same as the phase of spool displacement that is a standard signal to measure phase bandwidth frequency of the directional control valve. A series of experiments were conducted to examine the possibility of using line pressure in to measure phase bandwidth frequency of a directional control valve. Phase bandwidth frequency could be measured with relatively high precision based on metering hydraulic line technique and it reveals consistent results even when valve input, oil temperature, and supply pressure change.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.185.1-185.1
• /
• 2016

Cutoff probe, diagnostics instrument for plasma density, have been received an extensive attention due to simple, robust and lowest assumption. Although the cutoff probe has a long history, physical model is limited in low density plasma. For that reason, we propose a novel transmission line model of cutoff probe for precise measurement of high density plasma. In addition simplified circuit model can be obtained from transmission line model. It can explain simply physics of cutoff probe in high density plasma.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.4
• /
• pp.763-769
• /
• 2009

A series voltage compensation(SVC) system is a power-electronics controller that can protect sensitive loads from disturbance in the supply system. Especially, voltage sags are considered the dominant disturbances affecting the power quality. This paper dealt with a system of off-line type voltage sag compensation by using a bi-directional DC/DC converter of environmentally friendly ultra-capacitor. This capacitor is attached to the DC link of SVC through the high-efficiency DC/DC converter in order to compensate the DC link voltage drop during short-term power interruption as voltage sags. Therefore, in this paper, a DC/DC converter to control high-efficiency energy of ultra-capacitor and voltage sag detection algorithm of off-line type SVC systems are newly introduced. According to the results of experimental of prototype system, it is verified that the proposed system has effectiveness of voltage sag compensation using an ultra-capacitor.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.9
• /
• pp.1727-1732
• /
• 2011

In order to realize a high performance(low loss, high isolation) microwave power divider/combiner, we have designed the power combiner/divider precisely in accordance with the different hight of central part. In the case of the high central part of the hight of $h_r$=10.2, a compensating part of the conical line is inserted in the conical conversion transmission line, and in the case of low central part of the hight of $h_r$=5.0, the conical conversion transmission line is remodeled into the 2-stage bend structure. In both case, the reflection characteristics are improved to 30dB over the operating frequency range of 5GHz bandwidth. A resistance is inserted between the peripheral ports so as to try to improve the isolation characteristics of the device. For the 16-divider/combiner, the isolation characteristics are improved to 10dB over the operating frequency range of 5GHz bandwidth.

• Proceedings of the KSR Conference
• /
• 2003.10b
• /
• pp.27-34
• /
• 2003

This Study is about adoption of slab track on the new high speed railway line between Daegu and Busan. While ballast track currently used is easy to construct with low investment, the error margin of rail track occurs in the track due to the repetition load of the train. Therefore, repairs should be carried out all the time to put the railway track at the repair level or less. In addition, noise caused by such repairs has become a new social problem at night. Construction costs for slab track are about 1.3-1.5 times higher than those for ballast track. However, slab track will save labor costs by solving various problems of ballast track. In this regard, it is feasible to adopt slab track on the new high speed railway line between Daegu and Busan.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.41 no.4
• /
• pp.369-378
• /
• 1992

This paper proposes a utility parallel processing inverter system, which consists of a voltage source PWM inverter, isolation transformer and a reactor linking the inverter to utility line. This system realizes following functions : (1) voltage phase frequency and amplitude synchronization between inverter and utility line at stand-alone mode. (2) current phase synchronization between inverter and load at parallel mode. Therefore, despite sudden increase in load current over setting point at stand-alone mode, inverter system can be transferred into parallel mode immediately without transient current. Furthermore, high frequency(18KHz) PWM control and sinusoidal filtering improve the inverter output waveform by eliminating high order harmonic components as well as low order. As a switching device, IGBT is used for high frequency switching and large current capacity.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.1
• /
• pp.1-6
• /
• 2011

This paper describes the high speed PLC-based remote control system that can monitor and control textile machineries bi-directionally through Internet. There are many textile machineries without network functions in the factory. We apply the PLC technology in order to give a network function to them in which the existing electric power line is used with network communication lines without separate wiring constructions. In order to realize this system, we have implemented a protocol for network communication of system, high-speed PLC modules, and Ethernet-to-UART modules. Finally we confirmed the effectiveness of system by applying actual test environments.

• Proceedings of the Korea Contents Association Conference
• /
• 2010.05a
• /
• pp.31-33
• /
• 2010

The image communication system based on power line communication(PLC) that manages the status of workers in deteriorated. work environments such as high temperature and pressures as realtime is designed and implemented in this paper. The major design considerations for system design are such that the adaptation of simple architecture, simplicity of installation and movement, tolerances about high temperature and pressures, transmission of high quality image under various noise environments.

• Proceedings of the KSR Conference
• /
• 2003.10a
• /
• pp.156-161
• /
• 2003

Korean High Speed Train (KHST) has been tested on high speed line in JungBu site since it was developed in 2002. The data acquisition system was used to test successfully the on-line test for proving the dynamic performance of KHST. The recognition of system vibration mode for railway vehicle is essential to understand the characteristics of design for dynamic system and diagnose the dynamic problems of vehicle system during test and operation. But, up to now, there are the efforts to know the system vibration mode within limit of theoretical field only, not experimental approach with systematic method. The theoretical results are too reliable to apply to real design problem, because it is theoretically based on the homogeneous linear system although the real system have the nonlinear characteristics and vary the environmental conditions. Therefor, in this paper, it is proposed the efficient method of vibration analysis for rail vehicle system and this method apply to KHST to recognize the vibration mode characteristics of it. The results show that this method is able to make the system vibration modes for KHST clear.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.947-953
• /
• 2010

The KTX-Sancheon has been commercially operating on the high-speed line since March. 2. In order to verify the performance of high-speed train and core equipments such as current collection system, sophisticated tests and evaluating procedures should have been considering. In this paper, the load cell with a built-in strain-gauge which developed to improve measuring method of contact force between the pantograph and catenary system is introduced. The static test results of the load cell shows that its design is very suitable and applicable for the dynamic test and on-line test. After the test and evaluation of load cell's dynamic calibration with pantograph, we will be applied to test interaction characteristics between the pantograph and catenary system on the high-speed line.