• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.5
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• pp.410-415
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• 2011

In this paper, we investigated the fault current limiting and the load voltage sag suppressing characteristics of the flux-lock type SFCL, designed with the additive polarity winding, according to the variations of turn number's ratio and the comparative analysis between the resistive type and the flux-lock type SFCLs were performed as well. From the analysis for the short-circuit tests, the flux-lock type SFCL designed with the larger turn number's ratio was shown to perform more effective fault current limiting and load voltage sag suppressing operations compared to the flux-lock type SFCL designed with the lower turn number's ratio through the fast quench occurrence of the high-$T_C$ superconducting (HTSC) element comprising the flux-lock type SFCL. In addition, the recovery time of the flux-lock type SFCL after the fault removed could be confirmed to be shorter in case of the flux-lock type SFCL designed with the lower turn number ratio.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.10
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• pp.524-530
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• 2000

This paper presents a transformer protective relaying algorithm using the ratio of induced voltages. The proposed algorithm calculates primary and secondary voltage from currents and voltages of primary and secondary windings. The ratio of primary and secondary induced voltages is equal to the turn ratio in case of the steady state and magnetic inrush. On the other hand, the ratio is different form the turn ratio in case of internal winding faults. The algorithm does not require B-H curve and can reduce the relay's operating time.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.34-38
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• 2013

According to the increase of electric consumption nowadays, power system becomes complicated. Due to this, the size of single line-to-ground fault from power system also increases to have many problems. In order to resolve these problems effectively, an Superconducting Fault Current Limiter(SFCL) was proposed and continuous study has been done. In this paper, an SFCL was combined to the neutral line of a transformer. An superconductivity has the characteristics of zero resistance below critical temperature. because of this, SFCL has nearly zero resistance. so we connecting SFCL to neutral line will not only have any loss in the normal operation but also have the less burden of electric power because of only limiting the initial fault current. We analyzed the characteristics of current, voltage according to the changes of turn ratio of 3 phase system in case of combinations of an SFCL to the neutral line. It was confirmed that the limiting rate of initial fault current by the increase of turn ratio was reduced.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.305-311
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• 2017

In this paper, the LLC resonant converter battery charger, using adaptive turn ratio scheme, is proposed to achieve high efficiency and wide range output voltage. The LLC converter high frequency transformer has an adaptively changed turn ratio by the auxiliary control circuitry. As a result, the optimal converter design with a large magnetizing inductance is easily achieved to minimize the conduction and the turn-off losses while providing widely regulated voltage gain capability to properly charge the Li-ion battery. The proposed converter operational principle and the optimal design considerations are illustrated in detail. Finally, several simulation results verify the proposed LLC resonant converter's effectiveness.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.124-132
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• 2018

This paper proposes an LLC resonant converter based battery charger which utilizes an adaptive turn ratio scheme to achieve a wide output voltage range and high efficiency. The high frequency transformer of the LLC converter of the proposed strategy has an adaptively changed turn ratio through the auxiliary control circuit. As a result, an optimized converter design with high magnetizing inductance is possible, while minimizing conduction and turn-off losses and providing a regulated voltage gain to properly charge the lithium ion battery. For a step-by-step explanation, operational principle and optimal design considerations of the proposed converter are illustrated in detail. Finally, the effectiveness of the proposed strategy is verified through various experimental results and efficiency analysis based on prototype 300W Li-ion battery charger and battery pack.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.57-64
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• 2002

This paper describes the results of a series of experiments executed by using two pilot-scale oxv-fuel burners are designed for maximum capacity of 50,000 kacl/hr, 300,000 kcal/hr and installed in the test furnace. The effects of turn-down ratio, excess oxygen ratio, nozzle exit velocity, injection angle, swirl vane angle and inlet oxygen temperature on the combustion characteristic are investigated. Temperature distributions are measured using R-type and Molybdenum sheathed C-type thermocouple. The results showed that maximum temperature and mean temperature increase with the increase of turn-down ratio and inlet oxygen temperature. The maximum flame temperature was increased about 35% compared to the case of equivalent air operated condition. In addition, Optimum excess oxygen ratio and nozzle characteristics are obtained for this oxy-fuel glass melting furnace.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.160-163
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• 2008

In this paper, an auto-diagnosis method of the stator winding fault for small induction motor is suggested. 3-phase stator currents are sampled, filtered, and transformed with Park's vector transformation. After then Park's vector patterns are obtained. To detect the stator winding fault automatically, a distortion ratio is newly defined and compared with the one of healthy motor, and the threshold levels of distortion ratio are suggested. The 2-turn, 4-turn, 8-turn winding fault are tested with no load, 25%, 50%, 75%, and 100% rated load. The distortion ratio of the Park's vector patterns are increased as the increase of the faulted turns, but are same as the increase of the load.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.414-417
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• 2014

At present, the demand for electric power increases, the electric power system is complicated. The size of the line-to-ground fault and the line-to-line fault occurred with complication of electric power system continue to increase, therefore several issues are raised. To address these issues effectively, the superconducting fault current limiter (SFCL) has been proposed, this study is ongoing. In this paper, we applied the SFCL in three-phase transformer and comparative analysis of the electric power burden to the SFCL. The superconductor is combined to the third winding of transformers in connection structure. In case of a third line-to-line fault, we did comparative analysis of the electric power burden to the SFCL based on the turn ratio of transformer third winding. In this case, we could confirm as the third turn ratio increased, electric power impressed to the superconducting element increased.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.4
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• pp.54-67
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• 2016

All roundabouts are designed based on "Roundabout Design Guideline, Ministry of Land and Transportation, 2014" in Korea. The guideline also provides the traffic volume criteria to convert from signalized intersections to roundabouts. While the criteria are based on capacity of roundabouts, left-turn ratio and the number of lane on approaches are not considered to calculate the capacity of roundabouts. Therefore it is difficult to apply the traffic volume criteria in the real world. In this study, we studied the impact of left-turn ratio and the number of lane on approaches into capacity of roundabouts using micro-simulation. It was found that the capacity of roundabouts is changed according to left-turn ratio and the number of lane on approaches.

• Journal of Korean Society of Transportation
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• v.21 no.4
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• pp.67-77
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• 2003

The purpose of this study is to provide the criteria for implementing unprotected left turn at intersections with variation of traffic volume on a cross road approach. Using Transyt-7F model, the delays calculated from permissive and protected left turn signal system were compared by gradually increasing the left turn volume for a certain opposing through volume up to the volume limits to which permissive left turn is more effective, Average stopped delay of the intersection was used as the measure of effectiveness in this study. The major conclusions are (1) the lighter the traffic gets in a cross road, the more the allowable left turn volume increases. The allowable left turn volume when the ratio of cross traffic to the concerned approach traffic is 0.6 appears about 50% more than the volume when the ratio is 1.0. (2) Comparing to the criteria of the manual of traffic safety facility, the results when the traffic ratio is 0.6 seem to be most similar the criteria of manual and the results when the traffic ratio are 0.8 and 1.0 appears to be lower than the criteria of manual. (3) The possible amount of making a left turn that is inversely proportional to the opposing through traffic, decreases as the number of opposing through lanes increases. The products of volume need to be used as the criteria of permissive left turn with considerable cautions because of its low consistency.