• Journal of the Korean Society for Precision Engineering
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• v.20 no.4
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• pp.92-102
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• 2003

To detect electrical faults of a TFT (Thin Film Transistor) panel for the LCD (Liquid Crystal Display), techniques of converting electric field to an image are used One of them is the PDLC (polymer-dispersed liquid crystal) modulator which changes light transmittance under electric field. The advantage of PDLC modulator in the electric field detection is that it can be used without physically contacting the TFT panel surface. Specific pattern signals are applied to the data and gate electrodes of the panel to charge the pixel electrodes and the image sensor detects the change of transmittance of PDLC positioned in proximity distance above the pixel electrodes. The image represents the status of electric field reflected on the PDLC so that the characteristic of the PDLC itself plays an important role to accurately quantify the defects of TFT panel. In this paper, the image of the PDLC modulator caused by the change of electric field of the pixel electrodes on the TFT panel is acquired and how the characteristics of PDLC reflect the change of electric field to the image is analyzed. When the holding time of PDLC is short, better contrast of electric field image can be obtained by changing the instance of applying the driving voltage to the PDLC.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.265-269
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• 2008

Output voltage value of AC high voltage source has usually been obtained by measuring the low arm voltage of high voltage divider or the secondary voltage of high voltage transformer. In this study, we have fabricated the AC 400 kV high voltage divider using high voltage electrode and electric field measurement sensor. The dividing ratio of the fabricated 400 kV high voltage divider was evaluated using reference 400 kV capacitive divider. The dividing ratio of 400 kV high voltage divider is found to be 12,322 and has the good linearity within 0.63 % against AC high voltage up to 400 kV. Therefore, the developed 400 kV high voltage divider could evaluate 400 kV high voltage supply and voltage divider used in industry.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2114-2116
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• 1999

The shorted-turn sensor for synchronous generator's field winding has been developed. The sensor, installed in the generator air-gap, senses the slot leakage flux of field winding and produces a voltage waveform proportional to the rate of change of the flux. For identification of reliability for sensor, a shorted-turn test was performed at the Seoinchon combined cycle power plant on gas turbine generator. This sensor will be used as a detecting of shorted-turn for synchronous generator's field winding.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.6
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• pp.1-7
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• 2002

The use of an asymmetric Mach-Zehnder interferometric amplitude modulator to measure a relatively low frequency electric field strength is described. The sensitivity of an electric field sensor using a Ti:LiNbO$_3$ optical modulator is strongly affected by the shape of a electrode(probe antenna). To measure the low frequency electric field, a probe antenna of wide effective area is more useful than the usual dipole antenna. As a proof of this, the optical modulator was fabricated with a plate-type probe antenna and the usefulness of this antenna tested for measuring low frequency electric field strength. Measurements were performed in the range 0.1V/cm to 60V/cm at 60Hz through 100KHz. Using a probe antenna of 10mm$\times$10mm, the output voltage of 10㎷ was measured with respect to the electric field strength of 0.1V/cm at 60Hz. By increasing the effective area of the probe antenna, better sensitivity is obtainable over the measured range.

• Journal of Power Electronics
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• v.9 no.1
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• pp.68-73
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• 2009

Automotive inverters may require current sensors for motor torque control, especially, in applications of hybrid electric vehicles or fuel cell vehicles. In this paper, to achieve a compact, integrated and low cost current sensor, a hall current sensor without magnetic core is introduced for integrating an automotive inverter. The compactness of the current sensor is possible by using integrated magnetic concentrators based on the Hall effect. Magnetic fields caused by three-phase currents are analyzed and a magnetic shield design is proposed for decoupling the cross-coupled field. It offers galvanic isolation, wide bandwidth (>100kHz), and accuracy(< 1%). Using 2D FEM analysis, its performance is demonstrated with design parameters at a U-shaped magnetic shield. The proposed coreless current sensor is tested with rated current to validate the linearity and accuracy.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.2
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• pp.106-112
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• 2006

A new model for the continuous-magnetic interferences has been proposed in this paper to remove external interferes of magnetic field to the dual electric compass. By this removal, the dual electric compass can be used for proving the azimuth angle in an automobile navigation system instead of the rate gyroscope. In the navigation system with a GPS receiver, a DR sensor such as a rate gyroscope is needed to overcome the shielded areas, which is relatively expensive and requires frequent calibrations. However the dual electric compass designed by this research is cheap and provides absolute azimuth angle precisely, which is beneficiary to be used as a DR sensor. The main contribution of this paper is that the long-lasting magnetic interferences have been removed out by using the proposed model, which never be studied before. With a hybrid navigation system using a DR sensor, we demonstrated that dual electric compass is better than a rate gyroscope in terms of both economics and performances.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2135-2137
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• 2005

This paper describes the features of electric and magnetic fields produced by lightning discharges. The measuring system consists of fast electric field sensor, crossed-loop magnetic field sensors, signal processing circuit, A/D converter and data acquisition equipment with a 12bit resolution and 10[MS/s] sampling rate. The frequency bandwidth and responsitivity of the electric field measuring system were 40[Hz]${\sim}$2.6 [MHz] and 2.08 (V/m/mV) and those of the magnetic field measuring system were 400[Hz]${\sim}$1[MHz] and 2.78[nT/mV], respectively. The electric and magnetic fields produced by lightning discharges were observed, and the features and parameters of the waveforms were analyzed.

• Macromolecular Research
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• v.12 no.6
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• pp.564-572
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• 2004

Modem applications could benefit from multifunctional materials having anisotropic optical, electrical, thermal, or mechanical properties, especially when coupled with locally controlled distribution of the directional response. Such materials are difficult to engineer by conventional methods, but the electric field-aided technology presented herein is able to locally tailor electroactive composites. Applying an electric field to a polymer in its liquid state allows the orientation of chain- or fiber-like inclusions or phases from what was originally an isotropic material. Such composites can be formed from liquid solutions, melts, or mixtures of pre-polymers and cross-linking agents. Upon curing, a 'created composite' results; it consists of these 'pseudofibers' embedded in a matrix. One can also create oriented composites from embedded spheres, flakes, or fiber-like shapes in a liquid plastic. Orientation of the externally applied electric field defines the orientation of the field-aided self-assembled composites. The strength and duration of exposure of the electric field control the degree of anisotropy created. Results of electromechanical testing of these modified materials, which are relevant to sensing and actuation applications, are presented. The materials' micro/nanostructures were analyzed using microscopy and X-ray diffraction techniques.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.160-164
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• 2000

This paper describes oil water separator using difference of electrical resistor. Oil is a non-conductive element and water is a relatively high conductive element. It is possible to detect water included in oil. Electric sensor is formed 8mm iron stick. Valve is operated With controller inputting signal of electric sensor. A experiment was done for necessary voltage in making program of controller. Oil water separator which was tested in field conditions was saved 7% of whole oil and was drained over 150% water than manual valve.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.163-164
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• 2007

In this study, we developed intelligent spacer built in the internal type UHF PD sensors. 3-Dimensional electro-magnetic simulations were performed to analyze electric-field distribution of the single-phase GIS and three-phase GIS. After considering the spacer's specification, Sensor structures were designed and analyzed using the 3-D EM Simulator. As a result of the simulation the internal type UHF PD sensors were built in. Performance of the sensor built into real scale GIS spacer was measured in terms of return loss and detected Max voltage. And we identified a character of the intelligent spacer by using 5pC partial discharge ceil.