• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.8
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• pp.32-39
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• 2014

In general, non-directional LED lamps including high transmittance cover are more advantageous than directional LED lamps, which are efficient enough to improve luminous efficacy and obtain certification, allowing wide manufacture, sale, and distribution. Although KS C 7651(Self-ballasted LED lamps-Safety and performance requirements) was revised in July 2013, however, many companies are having a lot of difficulties in keeping the certification and product development for the lack of the photometric analysis for non-directional LED lamps. In this paper, through the measurement of the angular distribution of luminous flux of incandescent lamp and non-directional LED lamps, we examined the reasonability of non-directional LED lamps' standards as suggested in KS C 7651. According to the results, even if non-directional LED lamps satisfy KS C 7651, when compared to an incandescent lamp, they showed less diffusive than the incandescent lamp and the distribution of the luminous flux depending on the angle fluctuated greatly even among LED lamps. Judging by the result, the current standard of the non-directional LED lamps, KS C 7651, has been comprehended that the angular distribution of the luminous flux needs to be presented after being much more thoroughly standardized.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.22-33
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• 2011

An induction motor operated with a conventional direct self controller(DSC) shows a sluggish response during startup and under changes of torque command. Fuzzy logic controller(FLC) is used in conjection with DSC to minimize these problems. A FLC chooses the switching states based on a set of fuzzy variables. Flux position, error in flux magnitude and error in torque are used as fuzzy state variables. Fuzzy rules are determinated by observing the vector diagram of flux and currents. This paper proposes hybrid fuzzy controller for direct torque control(DTC) of induction motor drives. The speed controller is based on adaptive fuzzy learning controller(AFLC), which provide high dynamics performances both in transient and steady state response. Flux position, error in flux magnitude and error in torque are used as FLC state variables. The speed is estimated with model reference adaptive system(MRAS) based on artificial neural network(ANN) trained on-line by a back-propagation algorithm. This paper is controlled speed using hybrid fuzzy controller(HFC) and estimation of speed using ANN. The performance of the proposed induction motor drive with HFC controller and ANN is verified by analysis results at various operation conditions.

• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.1-7
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• 2019

Electromagnetic measurements of the power cable tunnel were conducted from August 10 to 20, 2018, in the ${\bigcirc}{\bigcirc}$ city underground utility tunnel. During this period, the average temperature was $31.89^{\circ}C$ and the humidity was 67.56% in power cable tunnel. As a result of the electromagnetic measurement, the highest electric field was 25.3 V/m and the magnetic flux density was $42.6{\mu}T$. The average electric field was 18.56 V/m and the magnetic flux density was $29.32{\mu}T$ in the power cable tunnel. As a result of comparison with the electric equipment technical standard, the electric field in the power cable tunnel was 0.5% of the electric equipment standard and 35.2% of the magnetic flux density. It's similar value that electric field is about robotic vacuum(15.53 V/m), and magnetic flux density is similar value about capsule- type coffee machine ($23.07{\mu}T$). The number of cable lines and the size of the electromagnetic waves were not proportional to each other through comparison of cable lines in the power cable tunnel. It was confirmed that 154 kV, rather than 22.9 kV, could have a greater influence on occupational.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.615-620
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• 2006

The reduction behavior of $TiO_{2}$ in Al and Al/CaSi containing self-reducing $TiO_{2}$ briquettes(SRTB) was investigated. The maximum yield of Ti was expected with the slag composition of 45-55%CaO in the $CaO-Al_{2}O_{3}$ system. When $CaCO_{3}$ was used as a flux, the oxidation loss of reducing agent by $CO_{2}$ should be compensated, and therefore it leads to excessive requirement of the reducing agent. By using Al and CaSi mixture as a reducing agent of $TiO_{2}$, the reaction products both oxide and metal could be liquefied, and separated effectively with each other. As a result, the yield of Ti increases remarkably. The optimum mixing ratio of CaSi to Al is 78%CaSi-22%Al.

• Journal of the Korean Magnetics Society
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• v.27 no.2
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• pp.70-75
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• 2017

Single-phase SRM is cost competitive because it can reduce the number of switches for small, low-cost applications. However, since the single-phase SRM is difficult to start itself, methods for realizing self-starting by using auxiliary magnet or auxiliary pole have been studied. Recently, a method of self-starting by changing the shape of the rotor with a saturable area has been proposed. The purpose of this paper is to analyze the magnetic structure of single phase 6/6 SRM with a saturable rotor and to improve the magnetic structure of rotor with a saturable area. For this magnetic analysis, FLUX2D, a finite element method analysis program, was used.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.13-19
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• 2002

Design and implementation methodologies on the performance evaluation system of two-channel ring-core Flux-Gate Compass (FG-Compass) are described, with evaluation procedures and methods based on the polynomial regression models. Performance evaluation system is consists of a step motor driving unit, a bearing transmitting unit and, evaluation programs using polynomial regression formulae. Through performance evaluation tests, total residual deviation tests, total residual deviation of $\pm$4$^{\circ}$ and eigen residual deviation of $\pm$2$^{\circ}$ are obtained from the FG-Compass. The result is more accurate values than the typical FG-Compass with eigen residual deviation of $\pm$4$^{\circ}$ and is provide a possibility to develop a high performance FG-Compass. In addition, the design methodology of a smart FG-Compass with the self estimation and correction of residual deviations is also discussed.

• Journal of Navigation and Port Research
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• v.26 no.5
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• pp.529-535
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• 2002

Design and implementation methodologies on the performance evaluation system of Two-Channel Ring-Core Flux-Gate Compass (TCRC FG-Compass) are described, with evaluation procedures and methods based on the polynomial regression models. Performance evaluation system consists of a step motor driving unit, a bearing transmitting unit and evaluation programs derived from polynomial regression formulae. Newly designed performance evaluation system enabled the accuracy of TCRC FG-Compass to be ascertained. It was confirmed that the size of residual deviation of TCRC FG-Compass is $2^{\circ}$, while that of the conventional one is $4^{\circ}$. In addition, the design methodology to the self estimation and correction of residual deviations is also discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.415-420
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• 2006

This paper introduces a new self-bearing motor which combines a homopolar step motor and a passive magnetic bearing. Compared with conventional self-bearing motors which are mostly based on the theory of active magnetic bearings and therefore have some difficulties in design of the complicated flux distribution and control of the levitation force and the torque independently, the proposed self-bearing motor has a very simple and novel structure and operating principle. for the levitation, it works just like passive magnetic bearings which use the repulsive force between permanent magnets. On the other hand, its rotation principle is quite similar to that of a conventional homopolar step motor. In this paper, we introduce the basic structure and the operating principle in detail, and show some results of FEM analysis to predict the performance of the proposed self-bearing motor and further, to get the optimal design parameters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.122-128
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• 2005

A feasibility study on the application of self?shielded flux cored arc welding to the on-site SM520 steel bridge box fabrication for express trains and high way construction instead of gas-shield flux cored arc welding was conducted in terms of weld soundness, mechanical properties, toughness and microstructures. All welded specimens made with the self?shielded FCAW process were tested by magnetic particle and ultrasonic techniques and they were found to be sound. All multipass weld specimens made with both self-shielded and gas-shielded FCAW processes showed yield and tensile strengths of $462{\sim}549\;MPa$ and $548{\sim}640\;MPa$, respectively. The impact values of Charpy V-Notch weld specimens also met with the required value of 40J at $-20^{\circ}C$. The hardness values of the top area of weldments were higher than those of the bottom area because of higher residual stresses in the near surface. It was found that welding characteristics of SM520 steel by the on-site welding conditions with self-shielded FCAW showed almost equivalent to those by gas-shielded FCAW in terms of sound welds, mechanical properties and microstructure.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.63.2-63.2
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• 2015

Solar flare is one of the energetic phenomena observed on the Sun, and it is often accompanied with eruptions such as global-scale eruption of a flux rope (filament/prominence eruption) and small-scale eruption of a plasmoid. A flare itself is a dissipative phenomenon where accumulated electric current representing free magnetic energy is dissipated quickly at a special location called a current sheet formed in a generally highly conductive solar corona. Previous studies have demonstrated how a solar magnetic field placed on the Sun forms a current sheet when magnetic shear is added to the field. Our study is focused on a self-consistent process of how a subsurface magnetic field emerges into the solar atmosphere and forms a current sheet in the corona. This study also gives light to a relation among a flare and two types of flare-associated eruptions; flux-rope eruption and plasmoid eruption.