• 제목/요약/키워드: a.c field

검색결과 7,152건 처리시간 0.03초

종자 결정 성장법으로 제조된 $GdBa_2Cu_3O_{7-y}$ 벌크 초전도체의 자기적 특성 (Magnetic Properties of $GdBa_2Cu_3O_{7-y}$ Bulk Superconductors Fabricated by a Top-seeded Melt Growth Process)

  • 김광모;박순동;전병혁;고태국;김찬중
    • Progress in Superconductivity
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    • 제14권1호
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    • pp.39-44
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    • 2012
  • The fabrications condition and superconducting properties of top-seeded melt growth (TSMG) processed $GdBa_2Cu_3O_{7-y}$ (Gd123) bulk superconductors were studied. Processing parameters (a maximum temperature ($T_{max}$), a temperature for crystal growth ($T_G$) and a cooling rate ($R_G$) through a peritectic temperature ($T_P$) for the fabrication of single grain Gd123 superconductors were optimized. The magnetic levitation forces, trapped magnetic fields, superconducting transition temperature ($T_c$) and critical current density ($J_c$) of the Gd123 bulks superconductors were estimated. Single grain Gd123 bulk superconductors were successfully fabricated at the optimized processing condition. The $T_c$ of a TSMG processed Gd123 sample was 92.5 K and the $J_c$ at 77 K and 0 T was approximately $50kA/cm^2$. The trapped magnetic field contour and magnetic levitation forces were dependent on the top surface morphology of TSMG processed Gd123 samples. The single grain Gd123 samples, field-cooled at 77 K using a Nd-B-Fe permanent magnet with 5.27 kG and 30 mm dia., showed the trapped magnetic field contour of a single grain with a maximum of 4 kG at the sample center. The maximum magnetic levitation forces of the single grain Gd123 sample, field-cooled or zero field-cooled, were 40 N and 107 N, respectively.

초고압 XLPE 전력케이블에 대한 설치후 교류내전압시험 현장적용 (Field Application of AC High Voltage Test after Installation for EHV XLPE Power Cables)

  • 김영;권병일;성정규;한창석
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2001년도 하계학술대회 논문집 C
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    • pp.1768-1770
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    • 2001
  • EHV power cables can take any damage during shipping, transportation, handling, storage and installation. As the damage influences a reliability of the power cable system in the short and long periods, field tests have been required, for installers, to confirm the reliability of an installed system and, for utilities, to make sure the compatibility of an installed system. Of field tests, a HV withstand test for the cable insulation has been performed to check the soundness of the insulation. For EHV XLPE power cables, the test has been done by applying a specified d.c voltage till lately. But as some problems with the d.c test is emphasized and the equipment for the a.c test is improved, the a.c test is considered positively as an after-installation test. This paper describes the recent trends of the a and its recent application in the field.

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VDF/TrFE 공중합체의 히스테리시스 및 온도특성 (A study on hysteresis and temperature properties of VDF/TrFe copolymer)

  • 방태찬;김종경;강대하
    • E2M - 전기 전자와 첨단 소재
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    • 제10권2호
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    • pp.156-165
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    • 1997
  • D-E hysteresis loops have been measured for the 65/35 mole % copolymer of vinylidene fluoride and trifluoroethylene over wide temperature range. The remanent polarization and the coercive field at room temperature were estimated to be 75 mC/m$^{2}$ and 55 MV/m respectively. D-E hysteresis loops were observed even below the glass transition temperature(-20.deg. C) and the remanent polarization and the coercive field were larger, as the temperature lower. It seems that the remanent polarization and the coercive field depend on the amorphous region as well as crystalline region in this copolymer. And the ferroelectric-to-paraelectric phase transition was observed at 90.deg. C on heating and 80'C on cooling. Double hysteresis loops were observed at the temperature(85.deg. C) of paraelectric phase.

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운전전류를 고려한 고온초전도 모터용 계자코일의 설계 (Design of Field Coil for High Temperature Superconducting motor considering Operating Current)

  • 조영식;서무교;백승규;김석환;손명환;권영길;홍정표
    • 한국초전도저온공학회:학술대회논문집
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    • 한국초전도저온공학회 2002년도 학술대회 논문집
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    • pp.315-317
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    • 2002
  • The value of I$_{c}$(critical current) in HTS (High Temperature Superconducting) tape has a great influence on B(equation omitted) (magnetic field amplitude applied perpendicular to the tape surface). Therefore, I$_{c}$ of HTS magnet is determined by not only operating temperature but also the B(equation omitted). In shape design of field coil for the HTS motor, a method to reduce the B(equation omitted) and to determine operating current should be considered in order to optimal design. On the basis of the magnetic field analysis, this paper deals with various field coil shape to obtain operating current of HTS motor by using analytical method. And also this paper discusses the operating current of 100hp class HTS motor by using I$_{c}$-B(equation omitted) curve.curve.

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REAL HYPERSURFACES IN A NONFLAT COMPLEX SPACE FORM WITH SPECIAL STRUCTURE TENSOR FIELD

  • Lim, Dong Ho;Kim, Hoonjoo
    • 한국수학교육학회지시리즈B:순수및응용수학
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    • 제28권3호
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    • pp.247-252
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    • 2021
  • Let M be a real hypersurface in a complex space form Mn(c), c ≠ 0. In this paper, we prove that if (∇Xϕ)Y + (∇Yϕ)X = 0 holds on M, then M is a Hopf hypersurface, where ϕ is the tangential projection of the complex structure of Mn(c). We characterize such Hopf hypersurfaces of Mn(c).

상용 주파수 (60Hz) Plasma Jet Torch의 동작특성에 관한 연구 (A Study on the Operating Characteristics of Commercial Frequency Plasma Jet Torch)

  • 전춘생;정재웅
    • 전기의세계
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    • 제24권1호
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    • pp.75-85
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    • 1975
  • In order to develop the commercial frequency (60Hz) plasma torch of small capacity for material cutting, welding and other industrial heating, the A.C plasma jet generator of non-transfered type is made domestically and the electrode configurations of plasma torch are composed of two kinds of electrodes W-C and W-Cu, combined by thermal emission and field emission electrode materials. In this paper, the characteristics of input power, thermal efficiency, electrode consumption, the flame and forms of arc voltage and arc current for A.C plasma torch are investigated in relation to such variables as arc current, argon flow and magnetic field intensity to obtain the basic design data necessary to A.C plasma jet generator. The result are as follows; (1)The input power, thermal efficiency and electrode consumption are influenced greatly by argon flow, magnetic field intensity and nozzle materials. (2)A.C arc voltage and current are non-symmetrial, involving D.C Component. Due to this current of D.C Component, transformer core is saturated and a large abnormal current flows into the primary winding coil. In order to prevent this abnormal current flow, a condenser must be connected in series to the main discharge circuit. (3)The stability and sharpness of jet flame are improved more in the torch of W-C electrode configuration than in the torch of W-Cu electrode configuration.

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Fabrication of Textured $Al_2O_3-Mullite-SiC$ Nano-composite by Slip Casting in a High Magnetic Field and Reaction Sintering

  • Sakka, Yoshio;Saito, Sho;Honda, Atsushi;Suzuki, Tohru S.;Moriyoshi, Yusuke
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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    • pp.327-328
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    • 2006
  • We have demonstrated that textured $Al_2O_3-mullite-SiC$ nanocomposites can be fabricated by slip casting followed by partial oxidation - reaction sintering of mixed suspensions of $Al_2O_3$ and SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at 1200C and 1300C. The degree of orientation of alumina in the nanocomposite was examined on the basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that alumina-oriented nanocomposites were fabricated. The three-point bending strength at room temperature was observed for the nanocomposites.

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Fabrication of Textured $Al_2O_3-Mullite-SiC$ Nano-composite by Slip Casting in a High Magnetic Field and Reaction Sintering

  • Sakka, Yoshio;Saito, Sho;Honda, Atsushi;Suzuki, Tohru S.;Moriyoshi, Yusuke
    • 한국분말야금학회:학술대회논문집
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    • 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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    • pp.455-456
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    • 2006
  • We have demonstrated that textured $Al_2O_3-mullite-SiC$ nanocomposites can be fabricated by slip casting followed by partial oxidation. reaction sintering of mixed suspensions of $Al_2O_3$ and SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at 1200C and 1300C. The degree of orientation of alumina in the nanocomposite was examined on the basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that aluminaoriented nanocomposites were fabricated. The three-point bending strength at room temperature was observed for the nanocomposites.

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Lorentz Force Density Distribution of a Current Carrying Superconducting Tape in a Perpendicular Magnetic Field

  • Yoo, J.;Kwak, K.;Rhee, J.;Park, C.;Youm, D.;Park, B.J.;Han, Y.H.
    • 한국초전도ㆍ저온공학회논문지
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    • 제12권4호
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    • pp.13-16
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    • 2010
  • The Lorentz force distribution of a high $T_c$ superconducting tape with increasing transport currents in magnetic field ($H_a$) was visualized. The external magnetic field was applied normally to the coated conductor tape surface after zero-field cooling, and the transport current ($I_a$) was increased stepwise from 0 to 90 % of the values of the critical current ($I_c$ ($H_a$)) at applied filed, Ha. The field distribution (H(x)) near the sample surface across the tape width (2w) was measured using the scanning Hall probe method. Applying an inversion to the measured field distribution, we obtained the underlying current distribution (J(x)), from which the magnetic induction, B(x) was calculated with Biot-Savart law. Then Lorentz force per unit length was calculated using F(x)=J(x)${\times}$B(x), which appears to be very inhomogeneous along the tape width due to the complicated distributions of J(x) and B(x).

Atomic Force Microscopy을 이용한 4H-SiC의 Local Oxidation (Local oxidation of 4H-SiC using an atomic force microscopy)

  • 조영득;방욱;김상철;김남균;구상모
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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    • pp.79-80
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    • 2009
  • The local oxidation using an atomic force microscopy (AFM) is useful for Si-base fabrication of nanoscale structures and devices. SiC is a wide band-gap material that has advantages such as high-power, high-temperature and high-frequency in applications, and among several SiC poly types, 4H-SiC is the most attractive poly type due to the high electron mobility. However, the AFM local oxidation of 4H-SiC for fabrication is still difficult, mainly due to the physical hardness and chemical inactivity of SiC. In this paper, we investigated the local oxidation of 4H-SiC surface using an AFM. We fabricated oxide patterns using a contact mode AFM with a Pt/Ir-coated Si tip (N-type, $0.01{\sim}0.025\;{\Omega}cm$) at room temperature, and the relative humidity ranged from 40 to 50%. The height of the fabricated oxide pattern ($1{\sim}3\;nm$) on SiC is similar to that of typically obtained on Si ($10^{15}{\sim}10^{17}\;cm^{-3}$). We perform the 2-D simulation to further analyze the electric field between the tip and the surface. Whereas the simulated electric field on Si surface is constant ($5\;{\times}\;10^7\;V/m$), the electric field on SiC surface increases with increasing the doping concentration from ${\sim}10^{15}$ to ${\sim}10^{17}\;cm^{-3}$. We demonstrated that a specific electric field ($4\;{\times}\;10^7\;V/m$) and a doping concentration (${\sim}10^{17}\;cm^{-3}$) is sufficient to switch on/off the growth of the local oxide on SiC.

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