• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.116-125
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• 2015

This paper presents experimental results obtained from actual installation conditions of surge protective devices (SPDs), with the aim of understanding the coordination of cascaded Class I and Class II SPDs. This paper also proposes effective methods for selecting and installing coordinating cascaded SPDs. The residual voltage of each SPD and the energy sharing of an upstream Class I tested SPD and a downstream Class II tested SPD were measured using a $10/350{\mu}s$ current wave. In coordinating a cascaded voltage-limiting SPD system, it was found that energy coordination can be achieved as long as the downstream SPD is a metal oxide varistor with a higher maximum continuous operating voltage than the upstream SPD; however, it is not the optimal condition for the voltage protection level. If the varistor voltage of the downstream SPD is equal to or lower than that of the upstream SPD, the precise voltage protection level is obtained. However, this may cause serious problems with regard to energy sharing. The coordination for energy sharing and voltage protection level is fairly achieved when the cascaded SPD system consists of two voltage-limiting SPDs separated by 3 m and with the same varistor voltage.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.5
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• pp.63-72
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• 2020

Solar-sharing, which is an agricultural photovoltaic system installing solar panels on the upper part of crop growing field, has especially drawn attention. Because paddy fields for cultivating crops are large flat areas, there have been various attempts to utilize solar energy for solar photovoltaic as well as growth of crops in agriculture. Solar-sharing was first proposed in Japan, and has been actively studied for optimization and practical uses. The domestic climate differs from the climate conditions in which the solar-sharing has been widely studied, therefore, it is required to develop the solar-sharing technology suitable for the domestic climate. In this study, a simulation model was developed to analyze the change of solar radiation resulted from the solar-sharing installation. Monthly solar illumination intensity and the change of illumination intensity according to the various conditions of solar panel installation were simulated. The results of monthly illumination analysis differed by altitude of the sun, which was related to season. In addition, it was analyzed that the monthly illumination decreased by up to 42% due to solar-sharing. Accordingly, it is recommended that solar-sharing should be installed as a way to maximize the efficiency of solar photovoltaic system while minimizing the decrease in solar radiation reaching the crops.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.65-70
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• 2005

In this study, the large scale model tests were executed to estimate the Load Sharing Ratio(LSR) of raft in a piled footing under various conditions. The conditions such as the subsoil type, pile length, pile spacing, array type and pile installation method etc. were varied in the pile loading tests about the free-standing group piles and a piled footing. As the results of this study, it was found that there were no differences of the load-settlement curves, along with the pile installation method and subsoil type. The piles supported most of the external load until a yielding load of the piled footing, but the raft supported a considerable load after a yielding load. And it was also found that the LSR didn't be affected by the pile installation method and the subsoil type. As the relative density of sands increased, the LSR decreased. As the pile spacing was wider and the pile length increased, there was a tendancy for the LSR to increase.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.31-39
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• 2013

Proper installation of Flexible AC Transmission Systems (FACTS) devices in existing transmission networks can enable power systems to accommodate more power transfer with less network expansion cost. The problem to maximize transmission system loadability by determining optimal locations and settings for installations of two types of FACTS devices, namely static var compensator (SVC) and thyristor controlled series compensator (TCSC), is formulated as a mixed discrete-continuous nonlinear optimization problem (MDCP). For solving the MDCP, in the paper, the proposed method with fitness sharing technique involved in the updating process of the particle swarm optimization (PSO) algorithm, can diversify the particles over the search regions as much as possible, making it possible to achieve the optimal solution with a big probability. The modified IEEE-14 bus network and a practical power system are used to validate the proposed method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.9
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• pp.73-82
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• 2014

This research proposes a new type of flyback converter topology based on magnetic circuit sharing. The proposed flyback topology uses a transformer involving shared magnetic flux, and its characteristic is magnetic flux cancelation by cross magnetic flux in the magnetic flux-sharing part of the core. The new topology aims to reduce the volume of transformer by reducing the cross section of the core. Compared to conventional converters using only 1 transformer, its circuit configuration involving the serial input and parallel output of 2 flyback coils allowed increased converter insulation strength. In addition, the adoption of interleaved switching method achieved the improvement of output voltage ripple, while magnetic circuit sharing reduced by 50% the cross section of core where magnetic circuit was shared.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.74-80
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• 2004

If the withdrawal force of strand driven roll which is controlled with predetermined speed isn't distributed regularly in continuous casting process, mold level is changed cyclically and slab quality is not good. In this paper, both casting speed control and load sharing control algorithm of strand driven roll according to ratio which is set up by operator at same time is proposed. The proposed algorithm is to share the withdrawal force by following torque current of each driven roll as average torque current by changing speed reference of each driven roll motor. The load sharing control with anti-wind up for improvement transient state is adopted and the proposed algorithm is implemented in POSCO pilot caster.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.95-103
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• 2013

Protection of the electrical and electronic equipment against surges in low voltage AC power distribution systems is based on wide applications of surge protective devices(SPDs). Cascade application of SPDs located at the service entrance of a building and near sensitive equipment is intended to ensure the optimal voltage protection level and energy sharing among cascade SPDs. In this paper, when surges impinge at the service entrance of the building of interest, the protection characteristics of two-stage cascade SPD systems were investigated. The influence of the distance between the upstream and downstream SPDs on the voltage protection level and energy sharing of the two-stage cascade SPD systems were analyzed experimentally. It was found that the energy sharing of two-stage cascade SPD systems strongly depends on the distance between the two SPDs and the component of SPD. As the distance between the two SPDs increases, the energy absorbed by the upstream SPD increases while the energy absorbed by the downstream SPD decreases. Consequently, it is desirable to select the upstream and downstream SPDs having the proper energy capability with due consideration of the distance between the two SPDs.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.6
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• pp.91-98
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• 2014

For the purpose of designing and applying the optimum surge protection scheme, multi-stage coordinated surge protective device(SPD) system is suitable to successfully fulfill its tasks; first, to divert a large amount of the transient energy, second, to clamp the overvoltage to the level below the withstand impulse voltage of the equipment to be protected. The length of SPD connecting leads shall be as short as possible. Long connecting leads will degrade the protection effect of SPDs. In this paper, the influences of the length of connecting leads on the energy sharing in a coordinated SPD system were investigated experimentally, and the simulation of determining the energy sharing and protection voltage level of each SPD depending on the length of connecting leads was carried out by using P-spice program. It was confirmed that the protection voltage level and energy sharing in coordinated SPD systems are strongly influenced by the length of connecting leads.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.29-35
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• 2013

For the purpose of designing and applying optimum surge protection, one of the essential points is to take into account the energy coordination between cascaded surge protective devices(SPDs) and it is important to obtain an acceptable sharing of the energy stress between two cascaded SPDs. In this paper, in case of two voltage-limiting SPDs connected in parallel, the amount of splitting impulse current and energy that flow through each SPDs is investigated as a function of the protective distance. As a result, the energetic coordination between cascaded SPDs is strongly dependent on the voltage protection level of SPDs and the protective distance. It was confirmed that the sharing of the energy between two cascaded SPDs and the limited voltage levels are appropriate when the voltage protection levels of both upstream and downstream SPDs are the same.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2000.11a
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• pp.173-178
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• 2000

The time sharing type high frequency inverter using serial-parallel resonant to give VVVF function in the inverter used as power source of induction heating at high frequency is presented in this paper. This proposed inverter can reduce distribution of the switching current because of using the current of serial resonant circuit to the input current of the parallel one. The analysis of the proposed circuit is generally described by using the normalized parameters. Also, according to the calculated characteristics value, a method of the circuit design and operating characteristics of the inverter is proposed. In addition, this paper proves the validity of theoretical analysis through Simulation. This proposed inverter show that it can be practically used in future as power source system for induction heating application, DC-DC converter etc.