• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.4
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• pp.111-116
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• 2011

This paper deals with the electromagnetic clutch which stop the generator at emergency by using the engine power of generator. The electromagnetic field was analyzed using Flux-2d program with different conditions : voltage, air gap, coil locations. As a result, the maximum magnetic flux density of electromagnetic clutch occurred between the coil and wheel : 0.27[T], 0.41[T] at 12[V], 24[V]. The maximum flux density was at the center location of the coil.

• Progress in Superconductivity and Cryogenics
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• v.2 no.1
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• pp.14-18
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• 2000

This paper describes a series of experiments to investigate the operational characteristics of a superconducting power supply with superconducting excitation coil. In this experiment, the superconducting excitation coil is introduced to control the pole-flex in the air gap of the machine. The operating current of the superconducting powder supply is designed to have the value of 300 [A] for the rotational speed of 600 rpm. Sensors installed on the Nb sheet yield the information on the spatial and temporal behaviors of the magnetic field in spot and on the characteristics of the superconducting power supply.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.260-263
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• 1997

In this paper, we describe the mechanical strain effects on the critical current density of HTS (BSCCO) pancake-type-magnet. Firstly the strain of pancake coil is calculated in terms of coil length, which is also a function of angle, and then the critical current density degradation due to strain is calculated along the coil. We assumed that the critical current density degradation pattern is same with that of $Nb_{3}Sn$. We also modelled the effects of magnetic field on the critical curent degradation, and the results are compared with those with null magnetic field.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.590-593
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• 2000

The analysis of current distribution in a solidly modeled coil is very important for accurate analysis of electric machines such as deflection yoke(DY). In general, Modeling every coils is impossible for analyzing magnetic field using the 3-D FEM, so solidly modeled coil is usually used. Some methods have been developed for analyzing current distribution, but these methods have fatal disadvantage that they cannot be applied to an arbitrary shaped coil and that they yield numerical errors. In this paper. a novel method for resolving the problems mentioned above is proposed. The new method is verified by the application to a DY and it shows improved results.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.232-235
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• 2004

Linear GMR isolator which is profitable for transmitting analog signal was modeled and the output voltage and current in relation to the input current were investigated. GMR isolator modeling was divided into two parts, namely magnetic and electric parts. The flow chart of the modeling was drawn in which the MR curve of the spin valves were incorporated to obtain the electrical voltage output. For magnetic modeling, 3-dimensional model of planar coil was analyzed by FEM method to obtain the magnetic field strength corresponding to the input current. Coil efficiency of the planar coil having magnetic core layer was shown to have about 1.5 times larger than that of the coil without the magnetic core layer. The feedback coil current(output current) corresponding to the input coil current was calculated to be within ${\pm}$0.25 mA of the linear fitting function of I$\_$out/= I$\_$in/-5 mA. Also, the response time and output waveforms were obtained when the coil current was a rectangular waveform. The rise time and fall time was 6 ${\mu}\textrm{s}$, respectively when the slew rate of the op-amp was 0.3 V/${\mu}\textrm{s}$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.380-384
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• 2010

A micromirror for a laser display system actuated by the electromagnetic force induced by the surface coil and the permanent magnet was designed and analyzed through the coupled physics analyses incorporating the electromagnetics, mechanics, and electrothermal analysis because the mechanical rotation of the micromirror is driven by the electromagnetic driving force. The proposed micromirror has two torsion beams to sustain the mirror plate which has surface coils on the top and the two permanent magnets exists on both sides of the micromirror for an external magnetic field source. The designed micromirror has the resonant frequency of 3.82kHz. When the magnetic field of the permanent magnet is 0.4T, the coil has 4 turns, and the current density of coil is 3.6A/$mm^2$, the estimated z axis displacement of the mirror plate edge is 0.23mm which corresponds to the rotation angle of $14.2^{\circ}$. When considering the joule heating in the current-carrying coil, the maximum temperature of the mirror plate is obtained as 300.045K, which induces the negligible changes in the rotation angle and the resistance of the coil.

• Journal of Welding and Joining
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• v.19 no.4
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• pp.391-398
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• 2001

MIAB welding method uses a rotating arc as its heat source and is known to be efficient in pipe butt welding. The arc is rotated around the weld line by the electro-magnetic force resulting from the interaction of arc current and magnetic field. This paper is concerned with the experiment of initial stage for process control, monitoring for weld quality, and the design of coil system which is efficient of flux generation and concentration. A coil system for the generation of magnetic flux was designed and constructed. Magnetic flux density and arc rotating behavior are important factors in MIAB welding, so the relations between these factors and process parameters were investigated. Various experiments were performed for the steel pipes(48.1mm O.D and 2.0mm thickness). The magnetic flux density is increased by increasing exciting current and decreasing gap size. The maximum of arc rotating frequency is affected by exciting current and gap size. However, the variations of arc rotating frequency during welding and then the melting process are mainly influenced by welding current. Thus, it is considered that the results of this study can be used as important data on the monitoring for weld quality and the design of efficient coil system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.872-873
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• 2011

This paper presents a multi-domain topology optimization using the harmonically excited coil and the iron in order to focus pulsed magnetic field (PMF). The design sensitivity of the harmonic magnetic field is derived by adjoint variable method. As a result of the optimization, PMF is considerably concentrated on the objective domain with much less leakage than the initial model.

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.53-53
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• 2004

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.5
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• pp.42-47
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• 1998

Bridcage RF coil is one of the most widely used RF coils in MRI. In order to use birdcage RF coils in open MRI systems, an open tructured birdcage RF coil has been investigated. By opening the ring structure of an original birdcage RF coil and driving the coil at two opening ends, the original birdcage RF coil can be modified to an open structured coil. In order to improve magnetic field uniformity of the open birdcage RF coil, driving voltage phases at the two opening ends can be controlled to be in-phase or out-of-phase each other. Operating frequency of the open birdcage RF coil has been theoretically derived, and the theoretical derivation has been verified by experiments.