• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.897-907
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• 2022

The purpose of this study is to develop a self-propelled underground crop harvester and its performance was evaluated by measuring the load during actual potato harvesting operations. This study was conducted at a constant working speed of 1 km·h^-1. A load measurement system was installed to measure the actual load and the required working power was analyzed. A hydraulic pressure sensor was also installed to measure the hydraulic pressure. The required hydraulic power was calculated using the hydraulic pressure and flow rate. The results showed that the engine speed, torque, and power during harvesting operation were in the range of 845 - 1,423 rpm, 95 - 228 Nm, and 9 - 31 kW, respectively. Traction power, excluding the hydraulic pump of the tractor and power take-off (PTO) output, was in the range of 9 - 28 kW, and it was confirmed that it occupies a ratio of 16.2 to 50% of the engine rated output. The engine can supply the minimum required traction power to move the vehicle. This means that the engine used in this study could be down-sized to be suitable for an underground crop harvester. In this study, the gear stages of the tractor were not considered. This research thus shows the possibility of developing a self-propelled underground crop harvester.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.3
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• pp.29-36
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• 2002

Recently, power quality problems in AC high-Speed Railway system have been raised, because heavy train and its higher speed are required in addition to new control system by using the Electronic devices. The installation/operation of the Series Capacitor(SC) has been only a device far voltage drop in power system up to now. However, the sufficient effectiveness of compensating In voltage drop has not been proved yet because of technical limitationf SC, and harmonic resonance is attracting a attention as one of new issues. Several problems are expected such as vocational problems of a traction substation, and overloading caused by a new construction of electric railway and the in transport. Therefore, extension of power feeding the fault in the traction substation should be also considered. So this paper represents the application of TSC-SVC on the electric railway power feeding system as a device of voltage compensation, and the simulations are executed through PSCAD/EMTDC.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1461-1467
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• 2009

The electric railway is a clean and energy saving system, because it requires relatively less energy than automobiles by transporting the same passengers or goods. Six thousands of vehicles are operated on Korean urban transit system. This system is 95% of regeneration system. Especially, the VVVF-Inverter vehicle has a merit of the highest regeneration rate. Energy consumption is 90% for traction and 10% for auxiliary supply. Braking energy is about 40% of energy consumption. Up to 40% of the tractive power of vehicles capable of returning energy to the power supply can be regenerated during braking and that this energy can be used to feed vehicles which are accelerating at the same time. The energy generated by braking vehicle would simply be converted into waste heat by its braking resistors if no other vehicle is accelerating at exactly the same time. Such synchronized braking and accelerating can not be coordinated, the ESS(energy storage system) stores the energy generated during braking and discharges it again when a vehicle accelerates. This paper presents field tests about the energy saving rate of the developed ESS. when the ESS is on/off, energy saving rate of the ESS is tested. The verification test in the field focused on energy saving.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.409-414
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• 2003

In this study we examined the method to select the size of the conductor rail for light rail system. Study results shows that using the conductor rail with lower resistivity requires fewer power substation, which results in lower construction cost. It also produces less copper loss. Therefore first choose the conductor rail with lowest resistivity and select the substation location, Next conduct computer simulation study to confirm it meets voltage requirement. if the minimum voltage is well above the required minimum voltage, substation number can probably be further reduced.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.640-645
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• 2003

최근의 도시철도 추진시스템은 VVVF 인버터로 제어되기 때문에 대부분 회생제동의 기능을 갖추고 있다. 회생제동 시 발생되는 전력은 그 때의 동일 노선에서 역행하고 있는 열차에 추진에너지로 사용되는 것이 가장 효율적이나 그것이 가능하지 않을 경우 혹은 그렇게 사용하고도 남는 잉여회생에너지가 발생할 경우 변전소의 회생용 인버터를 통해 역사 내에서 소비되는 방법도 많이 응용되고 있다. 이를 위해서는 회생용 인버터가 변전소 내에 설치되어야 한다. 본 논문에서는 경량전철시스템의 급전 시스템에서 이러한 회생용 인버터의 경제성분석과 적정용량 및 위치에 관에 논의된다.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.398-401
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• 2000

This paper describes the design of optimal location and capacity of DC substation for Mass Transit System. Three factors are considered for the design i.e. substation arrangements, line configuration and substation power capacity. In this study, we considered all of them for capacity calculation of power supply system for MTS. At first, DC-fed-traction system is introduced on an outline, a characteristics of train and fed network, and design method of substation arrangements. Optimal design procedures are described, and program for capacity calculation of the system is presented. In addition, the computer simulated results are compared with the conventional simple calculation method.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.717-722
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• 2007

Most of DC 1500V electric railway substations have adopted diode rectifiers to supply stable DC power. However, the diode rectifiers operate in the first quadrant of the voltage-current plane and thus need regenerative inverters which transfer the surplus regenerative power caused by regenerative braking of electric train sets into the grid. In order to select the proper capacity and installation position of regenerative inverter, it needs to investigate the consumed and regenerative energy of the electric traction substations in advance. This paper presents an analysis of regenerative energy in two substations operating in Seoul Seolleung and Kwangju Yangdong substations. DC line voltage and feeder currents are measured for a day to calculate consumed and regenerative power far four feeders. We calculated an amount of regenerative energy consumed in other feeders and estimated the cost reduction in energy consumption due to the reuse of regenerative energy

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.27-33
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• 2005

Constant load model is generally used for an electric train to perform the static analysis of AT feeding systems. In this model, the train will be considered as a constant load model when it drives or as a constant source model when it applies regenerative brake. However there must be some voltage constraints on the catenary in actual operations. These constraints are established for the reason of protecting the feeding facilities from excessive rise of regenerative braking voltage or guaranteeing the minimum traction power of train. In normal operating situation, the pantagraph voltage of the train should be maintained within these limits. Keeping these facts in minds, we suggest new methods of analyzing AT feeding systems using the constant power models with the conditions of voltage constraints. The simulation results from a sample system using the proposed method illustrate both the states of system variables and the supply-demand relation of power among the trains and the systems very clearly, so it is believed that the proposed method yields more accurate results than conventional methods do. The proposed methods are believed to contribute to the assessment of TCR-TSC for compensating reactive powers too.

• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.652-656
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• 2006

Constant load model is widely used for an electric train to perform the static analysis of AT (Auto Transformer) feeding systems. In this model, the train will be considered as a constant load model when it drives or as a constant source model when it applies regenerative brake. However there must be some constraints imposed on the pantagraph voltage in actual operations. These constraints are established for the reason of protecting the feeding facilities from excessive rise of regenerative braking voltage or guaranteeing the minimum traction power of train. In normal operating situation, the pantagraph voltage of the train should be maintained within these limits. Keeping these facts in minds, we suggest new methods or analyzing AT feeding systems using the constant power models with the conditions of voltage constraints. The simulation results from a sample system using the proposed method illustrate both the states of system variables and the supply-demand relation of power among the trains and the systems very clearly, so it is believed that the proposed method yields more accurate results than conventional methods do. The proposed methods are believed to contribute to the assessment of TCR-TSC for compensating reactive powers too.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1886-1891
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• 1998

Traction battery chargers are an integral part of the required charging infrastructure. EV charging systems are continuing to improve in design. The newer types are affecting power quality to a much lesser extent. High efficiency battery chargers are being designed and produced which form little or no harmonic distortion. In addition chargers are becoming smaller and lighter. This is due mainly to the fact that there are improvements in the power electronics industry, especially with respected to IGBTs. Lower costs are achieved by the reduction in price of the IGBTs, standard magnetic material and small cores for inductors and transformers. But electric vehicles occupy a relatively small market niche at present. Therefore with already existing power supply networks, establishment of EV infrastructure can safeguard the service value of present vehicle as well as ensure the ability to charge a significant number of such vehicle. In this paper, we surveyed the update charging technologies according to the conductive charging, inductive charging and fast charging. Then we suggested cost-optimized charging infrastructure in consideration of the economical, political and technical standpoint.