• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.2
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• pp.101-107
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• 2016

The main target in this paper is the localization of VME Type EPSM in Generator Exciter(EX2100) System. Developed EPSM has the compatibility with the existing product in the structure and shape and electrical feature and so on, but it has a much improved capacity and reliability in comparison with origin company product. this paper, to improve these functions, put emphasis on protection, monitoring, power capacity increase(over 120%), an enlarged scale of input voltage supply, AC/DC dual voltage use and so on. After manufacturing product localization, it was carried out several tests for the performance and reliability verification of developed product. These tests were performed in Authorized Inspection Agency(KTL) and field application test and maker self-test were additionally performed. Finally, the results of all tests were "success".

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.731-734
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• 2005

Generally, characteristics of electromechanical actuators are coupled with the mechanical and the electrical properties. Important mechanical parameters of these actuators are the achievable force and displacement in the presence of electric field. These mechanical parameters are related to the stress and strain of the materials and the actuator geometry. This paper presents how to measure the blocked force by using the micro-balance. The blocked force is defined as the force produced by the transducer under an applied voltage when the tip is constrained to zero motion. Also, a theoretical force by using the cantilever beam model is calculated under elastic domain. From the sample of 4 cm $\times$ 1 cm $\times$ 20 $\mu$m, the blocked farce measured from the equipment is 20.3 $\mu$N at 8 V$_{DC}$. By comparing it with the theoretical value, 24.9 $\mu$N, the blocked force measurement is acceptable. The furce measurement is also investigated with different AC electric fields and the frequency.

• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.78-83
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• 2012

The electrophoretic deposition(EPD) of ZnO nano-sized colloids is investigated by changing the colloid number concentration, applied force, and deposition time. The change of the colloid size in a suspension was examined by the different colloid number concentrations (N = $3.98{\times}10^{15}$, N = $3.98{\times}10^{14}$, and N = $3.98{\times}10^{13}$) with an increase of the deposition time and applied forces. Deposition behavior was investigated by changing the applied fields (from DC 5 V to 50 V) and the deposition time (5 min to 25 min). The surface microstructures of the as-deposited films were investigated by SEM. The dried films were sintered from $850^{\circ}C$ to $1,050^{\circ}C$ for 2 h and then the microstructures were also explored by SEM. The agglomeration rate was enhanced by increasing the colloid number concentration of colloids. Colloid number concentration in a suspension must be rapidly decreased at higher values of the electric field. ZnO nano-sized colloids had the highest zeta potential value of over -28 mV in methanol. A homogeneous microstructure was obtained at colloid number concentration of N = $3.98{\times}10^{13}$, applied DC field of 5 V/cm and 15 min of deposition time at an electrode distance of 1.5 cm. Under these conditions, the deposited films were sintered at $850^{\circ}C$ and $1,050^{\circ}C$ for 2 h. The results show a typical pore-free surface morphology of a uniform thickness of 400 nm under these experimental conditions.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.551-555
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• 1999

The deposition condition to obtain stoichiometric $Ta_2$O\ulcorner films, which is still controversial, using magnetron reactive sputtering was studied. The films were deposited by varying $O_2$gas flow rate with sputtering power and Ar gas flow rate of 200W and 60 sccm fixed. At the conditions of $O_2$ gas flow rate over 20 sccm, amorphous Tantalum oxide films with the refractive index of 2.1 and dielectric constant of 25 were deposited. Among those films, the capacitors dielectric properties of the film deposited at the condition of $O_2$ gas flow rate 50 sccm was best, the leakage current was 1$\times$10\ulcornerA/$\textrm{cm}^2$ at the electric field strength of 0.5 MC/cm and the breakdown field strength was over 2.0 MV/cm. This result could be explained from the analysis comparing with a standard sample using RBS because the composition of the film deposited at this condition was closest to the stoichiometric $Ta_2$O\ulcorner. The result of XPS analysis convinced that this film was stoichiometric $Ta_2$O\ulcorner film. A maximum cathode voltage was observed when $O_2$gas flow rate was 30 sccm. This shows that the Schiller's proposition that one can obtain stoichiometric films at the condition of maximum cathode voltage is not correct and more oxygen than that of the maximum voltage condition is necessary to deposit the stoichiometric Ta$_2$O\ulcorner films.

• The Journal of the Korea Contents Association
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• v.17 no.11
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• pp.9-17
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• 2017

In this paper, we propose a method to develop a multimeter which is used for measuring electric signals in industrial field by using battery and display of smart phone. Most of the multimeters that are linked to existing smartphones are connected to Bluetooth, which is inconvenient for battery use and low in measurement accuracy. To improve this, we developed smart multimeter that can supply power and data at the same time by USB OTG method which can be used by sharing the power of smartphone. We also developed a smart multimeter that can measure resistance, DC voltage, current, AC voltage and current. Developed an Android app with a button that displays measurement data and can select the type of electric signal to be measured, and tests whether the manufactured system is operating normally or not. Respectively.The results of this study confirm that it is possible to fabricate a smart meter that has equal or better performance compared to existing instruments and does not require a separate power source or display, and it is expected to be a reference for the development of various smart instruments in the future.

• Progress in Superconductivity
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• v.8 no.1
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• pp.81-86
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• 2006

We investigated resistance development in $Au/YBa_2Cu_3O_7(YBCO)$ thin film meander lines during high-power faults. The meander lines were fabricated by patterning 300 nm thick YBCO films coated with 200 nm thick gold layers into meander lines. A gold film grown on the back side of the substrate was also patterned into a meander line. The front meander line was connected to a high-power fault-test circuit and the back line to a DC power supply. Resistance of both lines was measured during the fault. They were immersed in liquid nitrogen during the experiment. Behavior of the resistance development prior to quench completion could be understood better by comparing resistance of the front meander lines with that of the back. Quench completion point could be determined clearly. Resistance and temperature at the quench completion point were not affected by applied field strength. The experimental results were analyzed quantitatively with the concept of heat transfer within the meander lines/substrate and to the surrounding liquid nitrogen. In analysis, the fault period was divided into three regions: flux-flow region, region prior to quench completion, and region after quench completion. Resistance was calculated for each region, reflecting the observation for quench completion. The calculated resistance in three regions was joined seamlessly and agreed well with data.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1925-1927
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• 1999

At the study, it has fabricated Al/AlN/GaAs MIS capacitor using DC reactive sputtering method. To applicate GaAs semiconductor in a MIS devices, investigated capability of AIN thin film by the insulator layer. Also it has investigated inversion of C-V characteristics by addition of the hydrogen(hydrogen concentration: 5%) and it has investigated that leakage current has $10^{-8}A/cm^2$ for 1 MV/cm breakdown electric field of I-V characteristics.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.235-239
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• 2006

Charge dynamics in polymeric materials after aged under ac electric field using the pulsed electroacoustic (PEA) technique is reported. The emphasis is placed on charge decay. The charge dynamics of the ac aged additive free low density polyethylene (LDPE) samples under dc bias differ from the sample without ac ageing, indicating changes brought in by ac ageing. It is believed that a slow decay rate of charge in the ac aged sample is related to the formation of deep traps in the material. However, chemical analysis by infrared spectroscope (FTIR) and Raman microscope reveals no significant chemical changes taken place in the bulk of the material after ac ageing. Further experiments on irradiated LDPE have revealed a similar behaviour, i.e. the charge decay is slower in irradiated samples than that of fresh sample. The findings presented clearly indicate that space charge measurement can be used as a diagnostic tool to monitor ageing in polymeric materials.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.283-289
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• 2009

In level set method, material properties are made to change smoothly across an interface of two materials with different properties by introducing an interpolation or smoothing scheme. So far, the weighted arithmetic mean (WAM) method has been exclusively adopted in level set method, without complete assessment for its validity. We showed here that the weighted harmonic mean (WHM) method for rate constants of various rate processes, including viscosity, thermal conductivity, electrical conductivity, and permittivity, gives much more accurate results than the WAM method. The selection of interpolation scheme is particularly important in multi-phase electrohydrodynamic problems in which driving force for fluid flow is electrical force exerted on the phase interface. Our analysis also showed that WHM method for both electrical conductivity and permittivity gives not only more accurate, but also more physically realistic distribution of electrical force at the interface. Our arguments are confirmed by numerical simulations of drop deformation under DC electric field.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.956-958
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• 1998

In this study, a relationship between partial discharge and the radiated electromagnetic waves is investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The patterns of frequency spectrum of radiated electromagnetic waves measured at the atmospheric pressure in Liquid Nitrogen($LN_2$) during the partial discharges in nonuniform electric field depend on positive DC power. From these points of view. it is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on the equipments of superconducting and cryogenic applications.