• 한국주조공학회지
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• 제21권4호
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• pp.232-238
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• 2001

Experimental study on the twin roll strip casting of BCuP-5(Cu-15wt%Ag-wt5%P) alloy was carried out using laboratory scale horizontal type twin roll caster. In this study, among the various operating parameters, such as tundish angle, contact angle, pouring temperature, roll speed, presetting gap of the rolls and kinds of roll and tundish materials, effect of pouring temperature for strip casting of BCuP-5 alloy which has long freezing range of about $170^{\circ}C$ was mainly investigated. BCuP-5 alloy strip was successfully produced when pouring molten metal at lower temperature than its liquidus temperature. Microstructure of the cast strip consists of primary Cu and eutectic. Especially the size of primary Cu phase increased with decreasing of pouring temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.320-323
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• 2001

A ZVZCS(Zero-Voltage and Zero-Current-Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. A secondary auxiliary circuit, which consists of one small capacitor and two small diode, is added in the secondary to provides ZVZCS conditions to primary switches, and aids to clamp secondary rectifier voltage. The auxiliary circuit Includes neither lossy component nor addition active switch, which makes the proposed converter efficient and effective. The principle of operation, feature, and design considerations are illustrated and verified through the experiment with a 500W 50kHz prototype converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.683-684
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• 2006

It is necessary to modify the state-of-the-art of speed control theory because of the phase asymmetry in the Linear Induction Motor (LIM)and for the constant speed control of mover using single vector control inverter system, it is important that primary stack is located in appropriated intervals in the 3D conveyer system using LIM. The dynamic characteristic analysis method of the vector controlled LIM using coupled FEM and control algorithm taking into account the movement is proposed. The focus of this paper is the analysis relative to selecting primary stack intervals in order to constant speed control in the 3D conveyer system using LIM.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 추계학술대회 논문집
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• pp.45-48
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• 2004

To improve the efficiency characteristics in the resonant converter using the contact-less power supply with the large air-gap and the long primary winding, this paper suggests the three-level series-parallel resonant converter(SPRC). The voltage gain characteristics of the proposed converter have the unit gain in a resonance frequency point of the series and parallel, and input voltage and current in the primary of SPRC are always In phase for the all equivalent load resistance because of the parallel resonant tank of the high impedance. The results are verified on the simulation based on the theoretical analysis and the 4kW experimental prototype.

• 한국안전학회지
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• 제14권1호
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• pp.25-32
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• 1999

The objective of this paper is to evaluate the fracture resistance characteristics of SA508 CL.1a carbon steel, TP347 stainless steel and their associated welds manufactured for primary coolant system of Ulchin 3,4 nuclear power plants. The effect of various parameters such as pipe size, welding method, chemical composition, crack plane orientation, metallography and fractography on the material properties were discussed. Test results showed that the effect of pipe size on fracture toughness is negligible while the effect of welding method on fracture toughness is significant. In addition, the drop of fracture toughness in the field fabrication weld of TP347 stainless steel is probably due to the large amount of $\sigma$-phase precipitated on the $\delta$-ferrite boundary and the large size dimples.

• 대한전기학회논문지:전력기술부문A
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• 제52권12호
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• pp.722-730
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• 2003

Current differential relay is commonly used to protect power transformer. However, current differential relay will be tripod by judging like internal fault during inrush occurring in transformer. To resolve such problem, this paper proposes a new protective relaying algorithm using Neuro-Fuzzy Inference. A variety of transformer transition states are simulated by BCTRAN and HYSDT of EMTP. Primary phase voltage and differential current are obtained from simulation. The target data which are used in Neuro-Fuzzy algorithm are obtained from transformed primary voltage and current. Then, these are trained by Neuro-Fuzzy algorithm. The trained Neuro-Fuzzy algorithm correctly distinguishes whether internal fault occurs or not, within 1/2 cycle after fault. Accordingly, it is evaluated that the proposed algorithm has good relaying characteristics.

• Advances in materials Research
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• 제1권1호
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• pp.13-29
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• 2012

In order to simultaneously enhance the strength and plasticity in nanostructured / ultrafine-grained alloys, a strategy of introducing multiple length scales into microstructure (or called bimodal composite microstructure) has been developed recently. This paper presents a brief overview of the alloy developement and the mechanical behavior of ultrafine-grained Ti-Fe-based alloys with different length-scale phases, i.e., micrometer-sized primary phases (dendrites or eutectic) embedded in an ultrafine-grained eutectic matrix. These ultrafine-grained titanium bimodal composites could be directly obtained through a simple single-step solidification process. The as-prepared composites exhibit superior mechanical properties, including high strength of 2000-2700 MPa, large plasticity up to 15-20% and high specific strength. Plastic deformation of the ultrafine-grained titanium bimodal composites occurs through a combination of dislocation-based slip in the nano-/ultrafine scale matrix and constraint multiple shear banding around the micrometer-sized primary phase. The microstructural charactersitcs associated to the mechanical behaivor have been detailed discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.200-204
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• 2001

A ZVZCS(Zero Voltage and Zero Current Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The new converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. A secondary auxiliary circuit, which consists of one small capacitor two small diode and one coupled inductor is added in the secondary to provides ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages including simple circuit topology high efficiency, and low cost make the new converter attractive for high power applications. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1kW 50kHz IGBT based experimental circuit.

• Transactions on Electrical and Electronic Materials
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• 제15권1호
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• pp.12-15
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• 2014

At the moment of transformer energization by the supply voltage, a high current called transient inrush current, which may rise to ten times the transformer full load current, could be drawn by the primary winding. This paper discusses a microcontroller circuit with the intention of controlling and limiting the inrush current for a transformer, by the method of ramping up the supply voltage feeding to the transformer primary. Simulations and the experimental results show a significant reduction of inrush current, when the ramping up voltage is applied to the three-phase transformer load. The inrush current could be almost eliminated if the correct switching step rate is chosen.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.161-164
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• 2009

This paper presents the ZVZCS(Zero Voltage and Zero-Current-Switching) Three-Level converter using the secondary coupled inductor and auxiliary capacitor. The converter with phase-shift control is proposed to reduce the circulating loss in primary and the voltage stress in secondary side. Using a coupled winding of the output inductor, two auxiliary capacitors are generated to reset the primary current at circulating interval.