• Progress in Superconductivity
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• 제3권2호
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• pp.229-234
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• 2002

In this paper, we analyzed the fault current performance in a $high-T_{c}$ superconductor(HTS) which was installed on flux-lock reactor with an external magnetic field coil covering the HTS. In this HTS fault current limiter using flux-lock concepts, the initial limiting current level can be controlled by adjusting the inductance of the coils. Furthermore, the current limiting characteristics of $high-T_{c}$ superconducting FCL can be improved by applying the external magnetic field into the $high-T_{c}$ superconductor. This paper discusses current limiting performance according to the inductance of the coil 1 in two cases with ac magnetic field coil or not and suggests the methods to improve the current limiting factor $P_{limit}$, which is defined as the ratio of the limited current $I_{FCL}$ at the current limiting phase to the prospective short -circuit current $I_{PSC}$.TEX> PSC/.

• 한국초전도ㆍ저온공학회논문지
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• 제19권1호
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• pp.30-35
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• 2017

The effects of the crystallographic orientation and sample thickness on the magnetic levitation forces (F) and trapped magnetic field (B) of single grain YBCO bulk superconductors were examined. Single grain YBCO samples with a (001), (110) or (100) surface were used as the test samples. The samples used for the force-distance (F-d) measurement were cooled at 77 K without a magnetic field (zero field cooling, ZFC), whereas the samples used for the B measurement were cooled under the external magnetic field of a Nd-B-Fe permanent magnet (field cooling, FC). It was found that F and B of the (001) surface were higher than those of the (110) or (100) surface, which is attributed to the higher critical current density ($J_c$) of the (001) surface. For the (001) samples with t=5-18 mm, the maximum magnetic levitation forces ($F_{max}s$) of the ZFC samples were larger than 40 N. About 80% of the applied magnetic field was trapped in the FC samples. However, the F and B decreased rapidly as t decreased below 5 mm. There exists a critical sample thickness (t=5 mm for the experimental condition of this study) for maintaining the large levitation/trapping properties, which is dependent on the material properties and magnitude of the external magnetic fields.

• 전기의세계
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• 제21권3호
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• pp.53-56
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• 1972

Electron paramagnetic resonance is one of the concrete forms of magnetic resonance and the superposition of an external magnetic field causes an orientation of the magnetic moment of an atom. On the assumption that both pumped levels be saturated and all relaxation times equal the inversion ratio for a push-pull paramagnetic maser is obtained and compared with those of three-level paramagnetic masers and the magnetic field intensities for 9 and 10 Gc push-pull ruby maser oriented with an angle of 54.deg.44' between the caxis and the magnetic field are, also, obtained.

• 한국전기전자재료학회논문지
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• 제21권1호
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• pp.79-84
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• 2008

We are developing a small-sized high temperature superconducting magnetic energy storage (HTS-SMES) magnet with the nominal storage capacity of 600 kJ, which provides electric power with high quality to sensitive electric loads. Critical current and N-value of a high temperature superconductor with large current, which was selected for the development of the 600 kJ HTS-SMES magnet, were investigated in various oblique external magnetic fields. Based on the critical current and N-value measured for the short sample conductor, we discussed the DC V - I characteristic of a model coil fabricated with the same conductor of 500 m. The results show that the measured critical current and N-value of the conductor for parallel field are constant in external magnetic fields less than about 0.2 T. However, for oblique fields, its critical current and N -value abruptly decrease in all external magnetic fields. Moreover, the measured critical current of the model coil well agrees with the numerically calculated one based on the DC V - I characteristic measured for the short sample conductor. This suggest that losses and critical currents for an HTS-SMES magnet made up of a high temperature superconductor with anisotropic characteristic are predictable from the data of a short sample conductor.

• 한국군사과학기술학회지
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• 제21권4호
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• pp.456-463
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• 2018

With the development of weapon systems by mounting various sensors, it makes important to analyze the precise functioning of sensor to external environment. In the case of small arms with magnetic sensor, the malfunction of small arms might be caused by strong external magnetic fields. In this study, the effects of magnetic sensor on external magnetic fields were analyzed, and optimal magnetic shield and shield structure were designed through M&S. In addition, the magnetic-shielding effectiveness of magnetic sensor in small arms was verified with commercial shielding materials. As a result, it was demonstrated that the Fe-Cu-Si-Nd-B with the structure of multi-layer metallic shields was shown the magnetic-shielding effectiveness of 83 % for an external permanent magnet and 19 % for an alternating magnetic field of 180 dBpT at 60 Hz, respectively.

• 한국세라믹학회지
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• 제43권12호
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• pp.829-832
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• 2006

In this study, the influence of the magnetic field on ferrite slurry's injection time during the slurry forming process was investigated. The evaluation system of the slurry's injection time under the strong magnetic field was designed with FEM and manufactured. Studied parameters were the applied magnetic field, the input pressure of the slurry, and the supplying tube materials. As the results, the injection time was increased with the external magnetic field strength and rapidly decreased with increasing the input pressure of the slurry. Also the injection time was decreased when the supplying tube was manufactured with the magnetic material having the higher magnetic permeability than the ferrite.

• 한국초전도ㆍ저온공학회논문지
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• 제19권1호
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• pp.26-29
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• 2017

We studied the distribution of the current density and its magnetic-field dependence in GdBCO coated conductors with AC bias currents using low temperature scanning Hall probe microscopy. We selectively measured magnetic field profiles from AC signal obtained by Lock-in technique and calculated current distributions by inversion calculation. In order to confirm the AC measurement results, we applied DC current corresponding to RMS value of AC current and compared distribution of AC and DC transport current. We carried out the same measurements at various external DC magnetic fields, and investigated field dependence of AC current distribution. We notice that the AC current distribution unaffected by external magnetic fields and preserved their own path on the contrary to DC current.

• 대한전자공학회논문지
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• 제6권1호
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• pp.12-18
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• 1969

도피관내 프라즈마상태를 발생시켜 외부자계를 마이크로파 전계에 수평 및 수직되게 가하여 그 때 일어나는 마이크로파 반사전력 및 투과전계를 측정하였다. 마이크로파 전계와 외부자계가 수평인 경우 외부자속밀도가 증가할 수록 감쇠만 일어났으나 서로 수직인 경우에는 3120가우스에서 반사전력이 최대로 되어 공진현상이 일어났다.

• 한국기계가공학회지
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• 제7권2호
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• pp.38-44
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• 2008

In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, apparent viscosity as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter.

• 전기학회논문지
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• 제56권2호
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• pp.282-288
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• 2007

Magnetization loss of high temperature superconductoring BSCCO tape and YBCO coated conductor(YBCOCC) is most important issue in the development of superconducting power devices. In this paper, the measured results of magnetization losses under various angles of external magnetic field in BSCCO tape stacked conductors and YBCO CC stacked conductors are presented and compared with each other. Also, we present the compared results of magnetization losses measured at arbitrary reaction magnetic fields and analyzed with perpendicular magnetic field components of those. The results show that magnetization losses of YBCO CC single and stacked conductors agree well with the analyzed value by it's perpendicular magnetic field component, but BSCCO single and stacked conductors are not.