• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.2
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• pp.361-370
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• 2024

In this paper, a method was studied for applying a series resonant type fault current limiter that can be manufactured at low cost to the smart grid distribution system. First, the impact of the harmonic components of the short-circuit fault current injected into the series resonance circuit of the fault current limiter on the peak value of the transient response was analyzed, and a methodology for determining the steady-state response was studied using percent impedance-based fault current computation method. Next, the effectiveness of the method was verified by applying it to a test distribution line. The test distribution system using the designed current limiter was modeled using EMTP_RV, and a three-phase short-circuit fault was simulated. In the fault simulation results, it was confirmed that the steady-state response of the fault current accurately followed the design target value after applying the fault current limiter. In addition, by comparing the fault current waveform before and after applying the fault current limiter, it was confirmed that the fault current was greatly suppressed, confirming the effect of applying the series resonance type current limiter to the distribution system.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.378-386
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• 2014

In this study, the characteristics of the current and wind forces acting on two floating bodies were numerically investigated using a commercial CFD software, STAR-CCM+. In the numerical analyses, LNGC was located right behind FSRU under uniform current or wind conditions. Steady calculations were carried out using a Reynolds averaged Navier-Stokes (RANS) solver and the realized k-epsilon model. First, the current coefficients of FSRU based only the CFD were compared with the model test data. Through this comparison, the present numerical models and mesh systems were indirectly verified. Next, computations for FSRU and LNGC in a uniform current were performed using different relative positions. It was found that the current coefficients were great affected by the longitudinal positions. Finally, the wind forces acting on FSRU and LNGC in tandem configurations were studied. The focus was on the shielding effects due to the aerodynamic interactions between FSRU and LNGC.

• Transactions on Electrical and Electronic Materials
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• v.18 no.2
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• pp.97-102
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• 2017

A current transformer (CT) is a type of sensor that consists of a combination of electric and magnetic circuits, and it measures large ac currents. When a large amount of current flows into the primary winding, the alternating magnetic flux in the iron core induces an electromotive force in the secondary winding. The characteristics of a CT are determined by the iron core design because the iron core is saturated above a certain magnetic flux density. In particular, when a large current, such as a current surge, is input into a CT, the iron core becomes saturated and the induced electromotive force in the secondary winding fluctuates severely. Under these conditions, the CT no longer functions as a sensor. In this study, the characteristics of the secondary winding were investigated using the time-difference finite element method when a current surge was provided as an input. The CT was modeled as a two-dimensional analysis object using constraints, and the saturation characteristics of the iron core were evaluated using the Newton-Rhapson method. The results of the calculation were compared with the experimental data. The results of this study will prove useful in the designs of the iron core and the windings of CTs.

• Journal of The Korean Society of Integrative Medicine
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• v.3 no.2
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• pp.9-16
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• 2015

Purpose: The purpose of this research was to ascertain the effect of Micro-current on a pain, balance, of knee joint in the patients with degenerative arthritis. Method: The 30 subjects who had micro-current in this research and randomly assigned into two group, an experiment group and a control group. micro-current was applied to 15 subject in the experiment group after general physical therapy. experiment group was applies general therapies and micro-current stimulation. The measurement were analyzed by using SPSS(V.20). In order to compare the post to the amount of pre-changes and post-changes of each group, the paired t-test was used. The difference between the experiment group and the control group was analyzed by using the analysis of convariance. Results: The results of this study were as follows; 1) In VAS measures, the pain point was significantly decreased in both the experimental and the control group. 2) Mc Gill Pain Questionnaire(MPQ), the pain point was significantly decreased in both the experimental and the control group. 3) TUG measures, the second was significantly decreased in both the experimental and the control group. 4) Weight distribution measures, the authority was significantly decreased in both the experimental and the control group. Conclusion: The micro-current is considered a degenerative knee arthritis that can be presented as an effective physical therapy intervention.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1257-1262
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• 2008

A long-distance remote sensing of temperature and current based on a fiber Bragg grating (FBG) is proposed and demonstrated. The thermal expanding effect of the epoxy and the Er-doped fiber ring laser (EFRL) are applied to the sensor system to enhance the temperature and current sensitivity. An EFRL with a 5 km-single-mode fiber and a FBG shows a high extinction ratio of more than 60 dB and a low power fluctuation of less than 1 dB. The metal wires are used to supply the current to the sensors. When the NOA65 puts on the FBG as a thermal expanding material, the temperature and current sensitivity of the lasing wavelength shift are about $30\;pm/^{\circ}C$ and 3pm/mA, respectively. The proposed sensing scheme is useful for measurement of current or temperature at a distant object of more than several km.

• Journal of Power System Engineering
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• v.5 no.3
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• pp.88-94
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• 2001

Stellite 12 alloy-powders were overlaid on 410 stainless steel valve seat using plasma transferred arc(PTA) process. Variation of the microstructure, hardness, wear and corrosion of overlaid deposit with current change was investigated. The deposit showed hypoeutectic microstructure, which was consisted of primary cobalt dendrite and networked $M_7C_3$ type eutectic carbides. As current increased, the amount of eutectic carbide decreased and its dendritic secondary arm spacing increased. Hardness of the deposit was decreased with increase of current. Stress relief heat treatment at $600^{\circ}C$ for two hours resulted in slight increase of hardness in the deposit and showed uniform hardness distribution in base metal without any hardened layer in HAZ. Specific wear decreased with increase of sliding distance. The deposit of high hardness with a lot of eutectic carbide showed relatively low specific wear. Initial corrosion current density of the deposit in 0.1N sulfuric acid was lower than those of 410 stainless steel, and showed a little variation with PTA current.

• Transactions on Electrical and Electronic Materials
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• v.17 no.5
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• pp.302-305
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• 2016

In this paper, a low on-resistance and high current driving capability trench gate power metal-oxide-semiconductor field-effect transistor (MOSFET) incorporating a current sensing feature is proposed and evaluated. In order to realize higher cell density, higher current driving capability, cost-effective production, and higher reliability, self-aligned trench etching and hydrogen annealing techniques are developed. While maintaining low threshold voltage and simultaneously improving gate oxide integrity, the double-layer gate oxide technology was adapted. The trench gate power MOSFET was designed with a 0.6 μm trench width and 3.0 μm cell pitch. The evaluated on-resistance and breakdown voltage of the device were less than 24 mΩ and 105 V, respectively. The measured sensing ratio was approximately 70:1. Sensing ratio variations depending on the gate applied voltage of 4 V ~ 10 V were less than 5.6%.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.3
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• pp.499-505
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• 2010

This paper analyzed that the coordination of recloser-fuse when a superconducting fault current limiter (SFCL) is installed to a power distribution system linked small scale cogeneration system. As a rule, the recloser to properly protect against both permanent and temporary fault is installed to upstream of fuse. Therefore, in a power distribution system linked small scale cogeneration system, the fault current is increased by adding fault current of small scale Cogeneration system when a permanent fault occurs, and the fuse could melt during the first fast operation of the recloser because of more sufficient heat from the increased current. However, when SFCLs are applied into a power distribution system linked small scale cogeneration system, the coordination of recloser-fuse could be accomplished due to decreased fault current as the effect of the impedance value of the SFCL. Therefore, to solve these problems, we analysed the operation of recloser-fuse coordination in a power distribution system linked small scale cogeneration system with SFCL using PSCAD/EMTDC.

• The Journal of Korean Medicine
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• v.24 no.4
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• pp.34-42
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• 2003

This study was designed to investigate the modulation of the Corydalis tuber on glycine-activated ion current in rat periaqueductal gray (PAG) neurons. Aqueous extract from Corydalis tuber has been widely used for pain control such as dysmenorrhea, irregular menstruation or amenorrhea with abdominal cramping, neuralgia, headache and gastrointestinal spasm. The PAG region of the brain is known to be involved heavily with nociception. Modulation of the Corydalis tuber on glycine-induced ion current in rat periaqueductal gray (PAG) neurons was studied by a nystatin-perforated patch-clamp technique. High concentrations of Corydalis tuber elicited ion current, which was suppressed by strychnine application. Low concentrations of Corydalis tuber reduced glycine-induced ion currents in the PAG neurons. Inhibitory action of Corydalis tuber on glycine-activated ion current was reduced by treatment with naltrexone, a non- selective opioid antagonist. Application of N-methylmalemide (NEM), a sulfhydryl alkylating agent, also reduced the inhibitory action of Corydalis tuber on glycine-activated ion current in the PAG neurons. These results suggest that the inhibitory effect of Corydalis tuber on glycine-activated ion current in the PAG neurons is one of the analgesic mechanisms of the Corydalis tuber, which may activate descending pain control system in PAG neurons.

• Journal of Satellite, Information and Communications
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• v.8 no.3
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• pp.10-14
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• 2013

In this paper, when applying current-mode circuit design technique showing constant power dissipation none the less operation frequency, to the low power design of dynamic voltage frequency scaling, we introduce the low power current-mode circuit design technique applying MOSFET in sub-threshold region, in order to solve the problem that has large power dissipation especially on the condition of low operating frequency. BSIM 3, was used as a MOSFET model in circuit simulation. From the simulation result, the power dissipation of the current memory circuit with sub-threshold MOSFET showed $18.98{\mu}W$, which means the consumption reduction effect of 98%, compared with $900{\mu}W$ in that with strong inversion. It is confirmed that the proposed circuit design technique will be available in DVFS using a current-mode circuit design.