• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.7
• /
• pp.694-701
• /
• 2013

The gear-reduction units of Korean high-speed trains consist of a motor reduction unit, an axle gear box reduction unit, and a tripod joint shaft. A reduction gear unit is a gearbox used to reduce the rotational speed of the input shaft to a slower rotational speed on the output shaft. This reduction in output speed helps to increase torque. Defective reduction gear units in high-speed trains are caused by damage to the gear or by gear fatigue. To diagnose potential problems, it is important to know the vibration characteristics of the reduction gear units. In this study, we analyzed the vibration characteristics of reduction gears under various conditions. The test setup included a full-scale test rig to evaluate reduction gear under both normal and extreme operating conditions.

• Proceedings of the KIEE Conference
• /
• 2008.11a
• /
• pp.264-266
• /
• 2008

DC transit system has been adopted in the metropolitan area, Korea since 1974. EMU in this system always reiterates that acceleration and retardation. When EMU decelerates using electric breaking, regenerative power occurs. Regenerative power can be consumed in vicinity EMU on the same line or in resistor. If DC transit system has inverter for reusing regenerative power, Energy efficiency in DC transit system will be increased. This paper present a scheme to set up the starting voltage for the developed inverter and its field test result.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.2200-2201
• /
• 2011

DC railway systems have been adopted in the urban rail train. When EMU decelerates using electric breaking, regenerative power occurs. extra power is forcibly wasted by resisterIf DC transit system has inverter for reusing regenerative power, energy efficiency in DC transit system will be increased. in this paper present developed regenerative power inverter and its field test result.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.1044-1045
• /
• 2008

DC transit system has been adopted in the metropolitan area, Korea since 1974. EMU in this system always reiterates that acceleration and retardation. When EMU decelerates using electric breaking, regenerative power occurs. Regenerative power can be consumed in vicinity EMU on the same line or in resistor. If DC transit system has inverter for reusing regenerative power, Energy efficiency in DC transit system will be increased. This paper present the adoption of developed inverter in commercial railway line and the test result procedure of developed inverter is presented.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.1079-1080
• /
• 2006

This paper presents the methods to save energy by using load consumption pattern analysis. Base on the substation annual power usage data, the characteristic of the substation power consumption have investigated. With this investigation effective electrical billing condition and the control target load has been determined. Most of power usage comes from the motor car, so power system and load table of motor car were reviewed. And in the metropolitan area the peak power consumption occurs at summer or winter rush hours because of its typical characteristics. From this data control point of time are determined. Through the whole study the methode to control the power Peak consumption are proposed and prototype was designed.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.9
• /
• pp.1577-1582
• /
• 2016

Now we are facing severe environmental issues such as global warming. Due to these, the concerns about eco-friendly energy have been increased. Kyoto protocol and Copenhagen climate change conference are circumstantial evidence of it. With these trends, the interests for the Electric Vehicles(EVs) which do not emit any harmful gases have gradually been raised. Unfortunately, however, massive connection of EVs to the power system could cause negative impacts such as voltage variations, frequency variations and increase of demand power. To prevent the mentioned issues, KEPCO adopts Time-of-Use(ToU) price for EVs charging. Nevertheless, it is important to verify the propriety of the charging system. In this paper, therefore, we used pre-introduced price elasticity concept to predict possible Demand Response(DR) on charging of EVs. And analyzed possible demand power increase according to various price elasticities. Simulation results show that given ToU based charging system would not enough to control the increase of demand power by EVs on the power system. It is concluded, therefore, additional methods and/or algorithms are required.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.64 no.6
• /
• pp.948-953
• /
• 2015

In this paper, we studied the environmental requirements for the railway transponder system. The transponder system is comprised of a reader installed beneath the train, a tag installed on the track, and a portable programmer. Among them, the transponder tag should be designed to withstand harsh environments, such as wide operating temperature range, mechanical shock and vibration, etc. To validate stable and reliable service under railway conditions, we carried out environmental test for transponder tag. We then installed the tags on the Honam high-speed test line.

• Journal of Electrical Engineering and Technology
• /
• v.11 no.2
• /
• pp.329-337
• /
• 2016

With the increasing deployment of distributed generators in the distribution system, a very large search space is required when dynamic programming (DP) is applied for the optimized dispatch schedules of voltage and reactive power controllers such as on-load tap changers, distributed generators, and shunt capacitors. This study proposes a new optimal voltage and reactive power scheduling method based on dynamic programming with a heuristic searching space reduction approach to reduce the computational burden. This algorithm is designed to determine optimum dispatch schedules based on power system day-ahead scheduling, with new control objectives that consider the reduction of active power losses and maintain the receiving power factor. In this work, to reduce the computational burden, an advanced voltage sensitivity index (AVSI) is adopted to reduce the number of load-flow calculations by estimating bus voltages. Moreover, the accumulated switching operation number up to the current stage is applied prior to the load-flow calculation module. The computational burden can be greatly reduced by using dynamic programming. Case studies were conducted using the IEEE 30-bus test systems and the simulation results indicate that the proposed method is more effective in terms of saving electric charges and improving the voltage profile than loss minimization.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.11
• /
• pp.5305-5321
• /
• 2016

In wireless communication, the multiple-input multiple-output (MIMO) system is a well-known approach to improve the reliability as well as the data rate. In MIMO systems, channel state information (CSI) is typically required at the receiver to detect transmitted signals; however, in practical systems, the CSI is imperfect and contains errors, which affect the overall system performance. In this paper, we propose a novel maximum likelihood (ML) scheme for MIMO systems that is robust to the CSI errors. We apply an optimization method to estimate an instantaneous covariance matrix of the CSI errors in order to improve the detection performance. Furthermore, we propose the employment of the list sphere decoding (LSD) scheme to reduce the computational complexity, which is capable of efficiently finding a reduced set of the candidate symbol vectors for the computation of the covariance matrix of the CSI errors. An iterative detection scheme is also proposed to further improve the detection performance.

• Journal of the Korea Safety Management & Science
• /
• v.10 no.4
• /
• pp.267-273
• /
• 2008

Many people transfer from the automobile to the subway because of increasing in oil price and improvement of mass transit system of Seoul Metropolitan City. But Seoul Metropolitan Subway have brought out passengers discomfort because it is more crowded over the appropriateness because of very high utilization though it is highly technically facilitated. This study deals with the development and simulation study of subway train simulator. We performed the validity simulation study for the simulator for the interval from Sindorim station to Samsung station in Seoul Subway Line 2. We analyzed the simulation results considering crowdedness after we defined the concept of crowdedness. Also we accomplished the analysis of simulation results after simulation under the assumption that the crowdedness is alleviated by controlling the passengers using RFID technology.