• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.117-122
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• 2005

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency converter bridge, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter bridge, and an AC filter. The high frequency converter bridge switching at 20kHz is used to generate bipolar PWM pulse, and the high frequency transformer raise its voltage twice, which is subsequently rectified by diode bridge rectifiers to result in a full-wave rectified sine wave. Finally, it is unfolded by a low frequency inverter bridge to result in a 60Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than the other systems due to elimination of 60Hz transformer.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.3
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• pp.182-188
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• 2006

Contactless power system is base on power transmission by magnetic force. The transformer loss is large because it separated with the gap. Also the system has unstable factor, since the parameters in the secondary can vary with the system movement. This paper proposes light train power transmission system using contactless transformer with multiple primary winding. To increase the system efficiency and to obtain the stable power transmission to the dynamic load, a resonant inverter is adopted. The proposed system was verified by the simulation using Spice and Maxwell. The designed contactless power transmission system is implemented for 5[kW] class and experimental results are discussed.

• Journal of Sensor Science and Technology
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• v.32 no.1
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• pp.55-61
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• 2023

The objective of this study is to determine the concentrations of mixed gases by establishing a diagnosis method of a transformer using tunable-wavelength optical infrared sensors. Absorption of infrared light by methane, acetylene, and ethylene gases injected is measured from the outputs of the infrared sensors. Regression analysis equations of the gas concentrations are acquired from their respective measured absorption. The obtained concentrations are as follows: -3-9 % errors above 600 ppm(methane), 3 % errors above 1200 ppm(acetylene), and 10 % errors above 500 ppm(ethylene). The concentration inference equations obtained using the individual gases are applicable when the absorption wavelength bands do not overlap. The results of the fault analysis of a transformer using the Duval triangle method and the tunable infrared gas sensors are as follows: temperature faults with -1-1% errors and energy faults with -7-7 % errors.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.6
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• pp.563-569
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• 2002

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency DC-DC converter, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter, and an AC filter. The 20kHz switched high frequency converter is used to generate bipolar PWM pulse, and the high frequency transformer transforms its voltage twice, which is subsequently rectified by diode bridge rectifiers for a full-wave rectified 60 Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than other power conditioning systems due to elimination of 60Hz transformer.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.2 s.31
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• pp.37-41
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• 2004

Parallel combination of cold chathode fluorescent lamps (CCFL) are widely used as the light sources of LCD TV backlight. Brightness uniformity is safisfied by using one transformer per one CCFL. Instead of using one transformer per oneCCFL, one transformer is used to drive 8 CCFLs by using differential driving method. A differential driving inverter with two transformers is developed to drive 16 CCFLs of 26' backlight for LCD TV. The brightness uniformity of $88\%$ was obtained by driving 26' backlight with the developed differential driving inverter successfully.

• KIEAE Journal
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• v.2 no.1
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• pp.49-54
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• 2002

Solar daylighting system provides free and comfort lighting, but its cost has been key issue due to difficult design and control of the heavy light collecting system. One of the solutions for the heavy design issues would be using a light framed film such fresnel and prism lens. Prism light guide luminaires have for some time been used to distribute light when it is desirable to have remote light sources. These systems are helpful when it is desirable to have fewer light sources, and/or to position light sources in places where lamp maintenance is easier, or electrical hazard is reduced. This proposed prototype system consists of light collector, light transformer and light pipe.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.97-101
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• 2002

The optical current transformer using Faraday effect is the sensor to measure current that flows in any conductor. This sensor doesn't undergo the magnetic saturation and effect of adjacent conductors. But this senor using bulk-glass sensing element has crucial drawback. It is impossible that the sensor is mounted to conductor without breaking the closed-loop of light or conductor. So we developed the clamp-type optical current transformer and made an experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.26-32
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• 2013

The LED has the proportional characteristic between the flux of light and its current and has caused voltage-current deviation on production process. Thus the unbalancing of each LED strings current occurred by its characteristic deviation. This unbalancing reduce a uniformity of the flux of light. Therefore, we researched to design method the LED driver based on DSP and the balancing transformer for a LED current balancing. These are applied to 50W LED module consist of 4 parallel strings. We analyzed the reduction of LED currents unbalance by experimental result from each method.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.9
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• pp.407-413
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• 2005

The optical current transformer was developed for 170 kV GIS using optical fiber. The sensor optimized on the optical CT was wound 3 turns and twisted 4 times per a turn at the pipe with a diameter of 130 m. To optimize the optical CT, the output signal was measured according to the setting angle of polarizer and analyzer, The asymmetry and distortion of the output signals were improved when the parallel polarized light was incident to the fiber sensor and under the angle of analyzer was $45^{o}$. The measurement error for the linearity was only $\pm{0.42}\;\%$ to 1,000 A in the case of reflection type.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.60-65
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• 2003

In this paper, we analyzed theoretically design requirement of a clamp-type optical current transformer(COCT)head, and manufactured a COCT head based on design requirement. Also, we measured and analyzed the current of conductor, and change of optical power and sensitivity with incidence angle of light using COCT head, and demonstrated the feasibility of manufactured COCT through those experiments.