• 한국산학기술학회논문지
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• 제12권5호
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• pp.2249-2253
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• 2011

본 논문에서는 저전력 u-IT 기기의 기술 기준에 대한 현재 각국의 동향과 그 기준치를 분석 및 비교를 통하여 해당 대역의 국내기준의 문제점을 분석하였다. 전자파 적합 등록에서 제시하고 있는 각국의 출력기준 기준치와 연계하여 이에 적합한 국내의 u-IT 기기의 실질적인 도입 가능한 출력 기준의 기준치를 제시함을 목적으로 한다. 본 논문에서 제시한 출력 기준 허용치를 바탕으로 국내 기준을 상향하면 저전력 u-IT 기기의 보급과 발전에 기여할 것으로 예상되며 국내 통신 시장은 물론 국제 통신 시장에서 경쟁력을 갖출 수 있을 것으로 예상된다.

• 전기학회논문지
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• 제60권6호
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• pp.1146-1151
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• 2011

There are two methods for train control in information transmission by using track circuit system and installing wayside transmitter. Information signal is transmitted to the on-board antenna by using rails. Continuous information about train intervals, speed and route is received by on-board antenna in AF track circuit system. The information signal is included with carrier wave and received by magnetic coupling in the on-board antenna. Therefore, it is important to define standard current level in the AF track circuit system. When current flowed to rails is low, magnetic sensors are not operated by decreasing magnetic field intensity. Hence, SNR is decreased because electric field intensity is decreased. When the SNR is decreased, there is the serious influence of noise upon demodulation. So, the frequency of information signal is not extracted in frequency response. Thus, it is possible to happen to train accident and delay as the information signal is not analyzed in the on-board antenna. In this paper, standard energy density is calculated by using Parseval's theory in UM71c track circuit. Hence, detection time of information signal is presented.

• 전기학회논문지
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• 제62권10호
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• pp.1465-1469
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• 2013

The resent developed high speed train called HEMU-430X (Highspeed Electric Multiple Unit - 430km/h eXperiment) recorded a 421.4 km/h in Kyoungbu high speed line in Korea. A verity of measurement systems are used to check the performance between pantograph and catenary system. An innovative measurement system is adopted to check the current of catenary wire in the track side during HEMU-430X test running. This paper presents the measurement results of catenary current in kyoungbu high-speed line and describe its utilizing technology in the experimental results of catenary current. In order to analyze field testing results, the current ratio between contact and catenary current have been analyzed by means of Carson-Pollaczek equation. And the current wave forms between catenary and contact wire are presented based on the simulation results.

• Journal of Information Display
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• 제12권3호
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• pp.115-119
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• 2011

Optically isotropic liquid crystal (LC) mixture such as blue-phase LC and nanostructured LC composites exhibit the advantages of fast response time, high contrast ratio and wide-viewing angle due to the induced birefringence along the horizontal electric field. Utilizing this mixture, a novel single cell gap in-plane switching-type polymer-stabilized blue-phase transflective liquid crystal display by embedding the nanowire grid polarizer as a polarization-dependent reflective polarizer in the R region is proposed. This device can be used as a normal black mode without any quarter-wave plate or patterned in-cell phase retarder. Moreover, the transmittance is identical to the reflectance so that it will be suitable for single gamma driving. Detailed electro-optic performances, such as voltage-dependent light efficiency and viewing angle of the proposed device configuration, are investigated.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2009년도 정기총회 및 추계학술대회 논문집
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• pp.179-181
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• 2009

고압 방전 램프는 점등 후부터 정상상태에 이르기까지 방전관 내부의 온도 및 압력이 광범위하게 변화하는 복잡한 동작 특성으로 모델링이 어렵다. 이러한 특성은 램프를 구동하는 안정기의 설계에 어려움이 따른다. 램프의 구동에는 초기 점화 시 높은 점화용 전압 펄스를 필요로 한다. 점화 후에 정상상태에 다다르면 램프 전극의 소모를 줄이기 위해 교류로 구동되어야 한다. 하지만 램프를 교류로 구동하게 되면 음향 공진 현상이 발생할 수 있다. 음향 공진 현상은 램프 구동 전류의 맥동성분이 큰 경우에도 발생을 할 수 있으므로 구동 전류의 맥동 성분의 크기는 최소화 돼야 한다. 램프의 수명시간을 길게 하려면, 안정기는 램프를 정격전력으로 구동하여야 한다. 따라서 안정기에서는 정전력 제어가 필요하게 된다. 램프 전류의 극성이 변화할 때, 램프 전류는 spike전류와 중첩이 된다. 본 논문에서는 spike 전류를 저주파구형파 램프 전류의 포락범위 안에 유지하고, 고주파 스위칭시손실을 줄이기 위해 소프트 스위칭 기법을 이용한 회로 설계를 제안했다. 제안된 방법은 시뮬레이션 및 이론적 수식적 방법으로 검증 했다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.65-67
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• 2003

This paper describes a design of power supply for electrodeless lamp system to be easy to control electric power widely keeping the high power factor. Proposed system is composed of power factor correction(PFC) circuit, half bridge(HB) inverter, high voltage transformer, full wave rectifier to supply dc number kV's magnetron(MGT) anode voltage in the second of high voltage transformer and magnetron. It was confirmed that the proposed circuits can correct the 99.8[%] power factor and control input power of the magnetron up to 33.3[%] linearly by adjusting of pulse frequency of the inverter through the experiment.

• 전기학회논문지
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• 제56권5호
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• pp.834-840
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• 2007

A generator plays an important role in transferring an electric power to power system networks. The generator protection systems in Korea have been imported and operated through a tum-key from overseas entirely. Therefore, a study of the generator protection field has in urgent need for a stable operation of the imported goods, and for preparation of next generation protection system. The paper describes the fault detection algorithm using WT(Wave!et Transform) of currents for a generator protection. The fault current signals after executing a terminal fault modeling collect using a MA TLAB package, and calculate the wavelet coefficients through the process of a multi -level decomposition (MLD). The proposed algorithm for a fault detection using the Daubechies WT (wavelet transform) was executed with a C language for the command line function and for the real time realization after analyzing MATLAB's graphical interface. The advanced technique had complemented the defects of a DFT by applying a Daubechies WT. and had improved faster a speed and more accurate of fault discriminant than a conventional DFR.

• 한국안전학회지
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• 제13권4호
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• pp.162-171
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• 1998

This paper presents the harmonics obstacle analysis and countermeasure of electrical consumption a place. Harmonics that can be cosidered as a environmental pollution of the power systems become the cause of the accidents and damages. The responsibility of eliminating the harmonics firstly lies on the generating side. But the original characteristics of the system sush as the harmonic transfer characteristics and the impedance of the system affect each other in the process of the generation and transmission of the harmonic. Therefore it is very difficult to specify clearly the harmonic controlling responsibility, because electric machinery generating harmonics are various in the industrial fields. The output of a inverter has a high harmonic content. There are several ways of minimizing the output harmonic content. One way is to use pulse width modulation techniques within inverter. An alternative method is to combine a number of square-wave inverters. In this research, we measure the harmonic of the countermeasure of electrical consumption a place. The paper present the problem of new harmonic elimination method of PWM inverter fed induction motor system using W-FT series. In the future, the proposed PWM pattern by W-FT series is effective not only to the induction motor but also to the electromagnetic machine such as voltage reglator, UPS.

• 한국전기전자재료학회논문지
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• 제18권10호
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• pp.960-964
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• 2005

In this paper, we dealt with a partial discharge(PD) measurement method that has been accepted as an effective and non-destructive technique to estimate insulation performance of low-voltage electric and electronic devices. The PD measurement system Is composed of a coupling network, a low noise amplifier, and associated electronics. h shielded box Is adopted to make a better measurement environment against around noise. A low cut-off frequency of the coupling network estimated by a sinusoidal wave input was 125 kHz (-3 dB). Calibration tests on laboratory set-up have shown that the PD measurement system has a stable sensitivity of 10 mV/pC. In an application test oil a low-voltage three phase Induction motor (5 HP), we could detect 0.53 pC level of partial discharge at the applied voltage of AC 650 $V_{peak}$.

• Transactions on Electrical and Electronic Materials
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• 제10권5호
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• pp.173-176
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• 2009

In the stator windings of a 6.6 kV rotating machine, internal discharges, slot discharges, and surface discharges are mainly caused by internal voids and insulation degradation. If a partial discharge(PD) occurs in an inner-part of the stator windings, it will cause electromagnetic pulses with wide frequency ranges. Discharge sparks and electromagnetic pulses generated from a discharge source, can be detected using various RF resonators like an EM sensor. In order to detect these types of electromagnetic sources, a planar patch sensor was designed and fabricated using a CST-MWS simulation, and PD signals from an artificially defected stator winding were also measured by the sensor proposed in this study. Furthermore, an HFCT was used as a reference sensor and compared with the proposed new planar patch sensor. In the results of the experiment, the planar patch sensor showed a similar performance to the HFCT sensor.