• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.228-232
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• 2002

In this paper, In order to solve the problem is proposed using a new type of electronic ballast that the traditional magnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight which is composed of rectifier, active power corrector, series resonant half bridge inverter, micro-controller and piezoelectric transformer for driving for driving T5 fluorescent lamp were manufactured. The proposed electronic ballast operated at high frequency (about 75kHz) shows a input power factor of more than 0.995, total harmonic distortion of less than $12\%$ and lamp current crest factor of less than 1.5, respectively. Output power and efficiency showed 28w and $85\%$, respectively. Accordingly, it is considered that the ballast using piezoelectric transformer can replace the typical electronic ballast.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.919-922
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• 2006

Comparing with the conventional transformer without the air gap, a contact-less transformer with the large air-gap (4.8cm) between the long primary winding and the secondary winding has the increased leakage inductance and the reduced magnetizing inductance. By the increased leakage inductance and the reduced magnetizing inductance on the primary of the contact-less transformer, a good deal of the primary current circulates through magnetizing inductance, which results in a massive loss in contact-less power supply (CPS). In this paper, the efficiency characteristics of the contact-less power supply using a series resonant converter is analyzed and simulated. The results are verified on the simulation based on the theoretical analysis and the 1.8kW experimental prototype.

• 조명전기설비학회논문지
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• 제24권11호
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• pp.9-16
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• 2010

This paper examines the temperature characteristics of an Optical CT (optical current transformer) using the Faraday effect for measuring high current in a super high voltage-power apparatus. It is performed as follows by the sensor for embodying Faraday effect. $\cdot$ A single-mode optical fiber capable of maintaining a polarization state is used. $\cdot$ A light source is applied at 1310[nm] to a Laser Diode. $\cdot$ The Linear of Faraday effect to a large current is evaluated and $\cdot$ A possible application using an Optical CT was shown. An Influence of Faraday effect to the surrounding temperature measured -40~50[$^{\circ}C$], and the characteristic of the current sensitivity was reported. An application using the results of the temperature compensation system was used in order to compensate for surrounding temperatures. A possibility of applying Optical CT for electric power apparatus was advanced further. We were able to confirm that this temperature calibration method can minimize the fluctuation of the output signal depending on the temperature conditions.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.681-684
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• 2005

본 논문은 (3$^{n-1}$+2) 레벨 형성법에 기반한 멀티레벨 인버터를 제안한다. PWM 인버터, LEVEL 인버터와 다단 변압기로 구성되는 이 회로는 양질의 출력전압을 형성하기 위해서 이차측이 직렬로 결합된 다단 변압기를 이용하게 된다. 변압기 권선비의 적절한 선택을 통해 입력전압의 정수비 형태로 주어지는 출력전압레벨을 형성할 수 있다. 제안된 방식으로 11레벨, 29레벨 시작품을 제작하여 실험을 통해 타당성을 검증한다.

• 전력전자학회논문지
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• 제18권5호
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• pp.492-500
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• 2013

A balanced forward-flyback converter for high efficiency and high power factor using a foward and flyback converter topologies is proposed in this paper. The conventional AC/DC flyback converter can achieve a good power factor but it has the high offset current through the transformer magnetizing inductor, which results in a large core loss and low power conversion efficiency. And, the conventional forward converter can achieve the good power conversion efficiency with the aid of the low core loss but the input current dead zone near zero cross AC input voltage deteriorates the power factor. On the other hand, since the proposed converter can operate as the forward and flyback converters during switch turn-on and turn-off periods, respectively, it cannot only perform the power transfer during an entire switching period but also achieve the high power factor due to the flyback operation. Moreover, since the current balanced capacitor can minimize the offset current through the transformer magnetizing inductor regardless of the AC input voltage, the core loss and volume of the transformer can be minimized. Therefore, the proposed converter features a high efficiency and high power factor. To confirm the validity of the proposed converter, theoretical analysis and experimental results from a prototype of 24W LED driver are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.262-265
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• 2003

During magnetic inrush or over-excitation saturation of the core in a transformer draws a large exciting current. This can cause mal-operation of a differential relay. This paper proposes a modified current differential relay for transformer protection. In order to cope with the remanent flux at the beginning. the start of saturation of the core is detected and the core flux at the instant is estimated by inserting the differential current into a magnetization curve. Then, this core flux value can be used to calculate the core flux. The proposed relay calculates the core-loss current from the induced voltage and the core-loss resistance; the relay calculates the magnetizing current from the core flux and the magnetization curve. Finally, the relay obtains the modified differential current by subtracting the core-loss current and the magnetizing current from the conventional differential current. The proposed technique not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the speed of the conventional relay.

• 전력전자학회논문지
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• 제12권3호
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• pp.199-204
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• 2007

본 논문에서는 멀티램프 구동이 유리하여 인버터 개수를 줄일 수 있는 장점을 가지고 있는 EEFL을 사용하였으며, 변압기의 자체 손실을 줄이고 소형화가 가능하며, 높은 승압비를 갖는 압전 변압기를 병렬로 연결하여 멀티램프 구동이 가능하도록 하였다. 최적의 EEFL 구동회로를 구성하기 위해서 Push-Pull 타입의 압전 인버터를 설계하였으며, 설계된 인버터 회로에 대한 시뮬레이션 분석을 통하여 타당성을 검증하였다. 향후 본 논문에서 제안하는 구동 방식을 대화면 LCD 백라이트에 적용할 수 있을 것으로 기대된다.

• 한국음향학회지
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• 제40권5호
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• pp.515-522
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• 2021

음성감정인식을 위한 훈련 데이터는 감정 레이블링의 어려움으로 인해 충분히 확보하기 어렵다. 본 논문에서는 음성감정인식의 성능 개선을 위해 트랜스포머 기반 모델에 대규모 음성인식용 훈련 데이터를 통한 전이학습을 적용한다. 또한 음성인식과의 다중작업학습을 통해 별도의 디코딩 없이 문맥 정보를 활용하는 방법을 제안한다. IEMOCAP 데이터 셋을 이용한 음성감정인식 실험을 통해, 가중정확도 70.6 % 및 비가중정확도 71.6 %를 달성하여, 제안된 방법이 음성감정인식 성능 향상에 효과가 있음을 보여준다.

• KEPCO Journal on Electric Power and Energy
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• 제8권2호
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• pp.79-86
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• 2022

Recently, the amount of maintenance is increasing due to the aging of power facilities, but the budget is constrained. Therefore, the importance of asset management that selects replacement priorities based on the failure probability and enhances investment effects is increasing. Because the number of distribution transformers is very large, the proportion of investment cost is very high. Therefore, it is important to select the investment priority by evaluating the reliable remaining life based on the failure probability. This paper evaluates the statistical expected life using the failure data of distribution transformers for the last 11 years and the current operation data. The hazard rate of distribution transformer and MV cable was compared with each other and the adequacy of early failure removal was reviewed and the statistical expected life corresponding to the cumulative failure probability B3% was calculated.

• 한국산업융합학회 논문집
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• 제25권3호
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• pp.451-459
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• 2022

Recently, in accordance with the demand for a large capacity of a secondary battery according to an increase in the demand for energy storage devices, a modular series battery configuration is essential. Accordingly, various cell balancing techniques have been proposed to prevent high efficiency and performance degradation of the battery. In this paper, propose a battery voltage balancing topology consisting of a flyback DC/DC converter type of a SIMO (Single-Input-Multiple Output) two-switch configuration for a series battery configuration. The proposed topology shows a structure in which a DC/DC converter connected to each module and a battery cell share one transformer. The topology cell balancing operation is a principle in which the voltage balancing converter of the battery converges to the same value through a transformer that shares a magnetic flux with the cells constituting the module through a single high-frequency transformer. In this paper, the dynamic characteristics analysis of the proposed circuit using PSIM was based and it was verified through experiments on one module.