• E2M - 전기 전자와 첨단 소재
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• 제9권6호
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• pp.600-604
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• 1996

High-T$_{c}$, superconducting wire is very important element for the application of electrical power systems. But it is very difficult to develope the long high T, wire with excellent properties. BiSrCaCuO multi-layer tapes are fabricated by a rolling method and pressing method sintered for several step at 840.deg. C. The critical current densities of 637 filament multi-layer tapes sintering 100 hours fabricated by the rolling method and pressing method are 1.3*10$^{4}$ A/cm$^{2}$ and 5.5*10$^{3}$ A/cm$^{2}$. The critical cur-rent densites of multi-layer tapes made by rolling method are found to be better than those fabricated by the powder-in-tube method and pressing process. As result, the rolling method is the best way to fabricated the multi-layer filament.t.

• 한국정밀공학회지
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• 제17권9호
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• pp.174-180
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• 2000

A reliable analytic model that determines the cross sectional shape of a workpiece(material) in round-oval(or oval-round) pass sequence has been developed. the cross sectional shape of an outgoing workpiece is predicted by using the linear interpolation of the radius of curvature of an incoming workpiece and that of roll groove to the roll axis direction. The requirements we placed on the choice of the weighting function were to ensure boundary conditions specified. The validity of the analytic model has been examined by hot rod rolling experiment with the roll gap and specimen size changed. The cross sectional shape and area of a workpiece predicted by the proposed analytic model were good agreement with those obtained experimentally. It was found that the analytic model has not only simplicity and accuracy for practical usage but also save a large amount of computational time compared with finite element method.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.172-179
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• 1999

As the martensite structure cause fracture failure during drawing from 5.5mm rod to 3.05mm dia. wire without additional heat treatment, the optium cooling condition to inhibit the occurrence of martensite was investigated. In order to get SAE9254+V quality, the effects of alloying element, vanadium on the mechanical properties were investigated. Based upon CCT and TTT curves and the results form cooling test in mill, optimun cooling was found in the condition of the laying head temp of 780$^{\circ}C$ and of the conveyor speed at 0.15m/sec with the whole cover closed. The wire rods produced under the condition showed the best mechanical properties of 120kg/$\textrm{mm}^2$ in TS and 50% in RA, having an excellent drawability. In vanadium added steels, tensile strength was improved without degrading elongation and charpy impact value. That means the strengthening by vanadium is mainly due to the grain refinement by the fine precipitates during tempering process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1116-1117
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• 2015

최근에 개발되고 있는 2세대 고온초전도 선재는 77.3 K의 액화질소보다 높은 임계온도를 가진다. 응용기기의 특성에 따라 액화질소 온도 이하의 다양한 온도 범위에서 운전되고 있다. 이러한 운전 온도의 차이는 초전도 선재의 임계전류 차이를 가져오고, 높아진 임계전류는 시스템의 안정도 측면에서 장점을 가지는 것으로 알려져 있다. 본 논문에서는 다양한 운전 온도 조건에 따른 임계전류에 의한 교류손실 측면의 연구를 진행하였다. 다양한 초전도 권선 형태에서의 임계온도에 따른 교류손실 특성을 수치해석을 통해 확인하고, 시스템의 안정성 향상에 필요한 운전온도에 대한 기본적인 특성 연구를 수행하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1118-1119
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• 2015

본 논문에서는 2세대 고온초전도 선재를 이용하여 영구전류 모드 운전이 가능한 상전도 접합부가 없는 초전도 모델 코일을 제작하고, 영구전류 인가를 위해 플럭스 펌프형태의 소규모 초전도 전원장치를 제작 77 K 운전 온도에서 영구전류 충전 시험을 진행하였다. 플럭스 펌프는 영구자석을 이용한 회전 자속형으로 제작되었고, 2세대 고온초전도 선재를 이용한 영구전류 마그넷의 적용에 필요한 초전도 전원장치의 기초 특성연구를 수행하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.821-825
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• 2000

Drawing is one of the oldest metal forming operations and has major industrial significance. This process allows excellent surface finishes and closely controlled dimensions to be obtained in long products that have constant cross sections. In drawing of the high carbon steel wire, exit speeds of several hundreds meters per minute are very common. Drawing is usually conducted at room temperature using a number of passes or reductions through consequently located dies. In multi-stage drawing process like this, temperature rise in each pass affects the mechanical properties of final product such as bend, twist and tensile strength. In this paper, therefore, to estimate the wire temperature in multi-stage wire drawing process, wire temperature prediction method was mathematically proposed. Using this method, temperature rise at deformation zone as well as temperature drop between die exit and the next die inlet were calculated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.89-92
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• 2004

This paper is concerned with the drawing process of Al-Si wire. In this study, the finite-element model established in previous work was used to analyze the effects of various forming parameters, which included the reduction in area, the semi-die angle, the aspect ratio and the inter-particle spacing of the Si in drawing processes. The finite-element results gave the consolidation condition. From the results of analysis, the effects of each forming parameter were determined. It is possible to obtain the important basic data which can be guaranteed in the fracture prevention of Al-Si wire by using FEM simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.845-846
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• 2006

Reduce AC loss is very important in superconductor power machine. And HTS power application are needed an increment of current capacity. in this paper estimate AC loss effect and increase of current according tocomposition stack with 1G wire and 2G wire by measurement. A Method of composition stack are YBCO-BSCCO, YBCO-BSCCO-BSCCO-YBCO and BSCCO-YBCO-YBCO-BSCCO. also, test result compared analytic equation by Norries

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.699-700
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• 2006

고온 초전도 전력케이블의 통전용량 산정은 먼저 고온 초전도 전력케이블의 임계전류를 먼저 알아야 한다. 선재의 임계전류를 알고자 하는 경우, 전압-전류를 측정하거나 온도를 측정하는 방법을 통해 임계전류를 알아내지만, 고온 초전도 전력케이블의 경우 이러한 방법으로 임계전류를 알아내는 것이 불가능하다. 본 논문에서는 고온 초전도 케이블에 사용되는 선재에 대한 임계전류를 측정하고, 전자장 해석을 한 후, 실험결과와 해석 결과를 토대로 고온 초전도 전력케이블의 임계전류를 계산하였다. 이렇게 계산된 임계전류를 이용하여 고온 초전도 전력케이블의 통전용량의 기초자료로 활용토록 하였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권11호
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• pp.658-663
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• 2004

According to the improvement of the HTS wires performance, several tapes of HTS superconducting machines are being developed. Stacked HTS tapes are used as conductor that can flow high current for the HTS power machines. To develop the HTS power machines, the critical current characteristics of a stacked HTS tapes in external filed and AC losses should be examined. In this paper, we present characteristic of the stacked HTS tapes and AC losses of HTS pancake windings with stacked tapes. AC loss of the pancake winding were measured and compared with the calculated loss by using AC loss data of the stacked samples and the magnetic flux density in the HTS winding under operating conditions. We can see that measured results generally agree well with the calculated results by using AC loss data of 4-stacked sample.