• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.61-64
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• 2001

Demand for development of 154kV Less-Flammable Power transformer is now increasing greatly instead of a oil-immersed transformer for preventing disasters and Less-flammability of substations. The most important point in developing Less-flammable transformer is cooling system. This paper describes the study on cooling characteristic of Less-flammable transformer.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.371-376
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• 2009

The Power Conditioning System is Power Transfer System which make array DC current to the Grid sinusoidal current. These are Low Frequency Transformer Inverter Type, High Frequency Transformer Inverter Type and Transformer-less Type. Low Frequency Transformer Type has a Excellent Isolation property, but doesn't have competitiveness in Size and Cost. Also High Frequency Transformer Type has a good Isolation property but there are many steps in Power transfer Switching. Nowadays, Transformer-less Type inverter change a transformer to DC/DC Converter which is small and cost effective. In this paper shown the DC/DC Converter Transformer-less Type multi-string inverter design and simulation. The Control Algorithm will be introduced and Simulation was accomplished.

• Journal of Power Electronics
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• 제14권6호
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• pp.1233-1242
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• 2014

A new inverter topology for single-phase photovoltaic (PV) systems is proposed in this study. The proposed inverter offers a four-level voltage in its output terminals. This feature results in easier filtering in comparison with other conventional two-level or three-level inverters. In addition, the proposed four-level inverter (PFLI) has a transformer-less topology, which decreases the size, weight, and cost of the entire system and increases the overall efficiency of the system. Although the inverter is transformer-less, it produces a negligible leakage ground current (LGC), which makes this inverter suitable for PV grid-connected applications. The performance of the proposed inverter is compared with that of a four-level neutral point clamped inverter (FLNPCI). Theoretical analysis and computer simulations verify that the PFLI topology is superior to FLNPCI in terms of efficiency and suitability for use in PV transformer-less systems.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.81-83
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• 2006

The conventional cold cathode fluorescent lamp (CCFL) driver for LCD TV has a transformer for each lamp to step up the high sinusoidal waveform from the low input voltage. The transformer used in the conventional topology causes the driver to have bulky size and high cost. This paper proposes a new transformer-less CCFL driver for LCD backlight that is based on the parallel-loaded resonant inverter topology. This resonant topology enables the circuit to supply enough high voltage for CCFL without a transformer. Also, with current-balancing technique, this transformer-less inverter drives 16 CCFL lamps.

• 전기학회논문지
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• 제61권7호
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• pp.992-997
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• 2012

In this paper, we were analyzed the vibration characteristics of the three-phase cast resin transformer using less than 50% of load in the field. Most of the cast resin transformer is less than 50% in the domestic field is used for load conditions. Consisting of a solid insulator cast resin transformer is generating lots of noise and vibration. In addition, because it is affected by Joule 's heat is used in light load conditions. As a results, the transformer vibrations at frequencies below about from 200Hz to 500Hz were detected. Vibration velocity depends on the load variations were found. Load up to approximately 20-30% in most cases the vibration velocity was found at 4,000 ${\mu}m/s$ or less, 8,000 ${\mu}m/s$ or more. Vibration frequency at light load conditions were generated at the 120Hz, 240Hz, 360Hz and 480Hz. At the load condition of from 10% to 20%, vibration velocity is higher than another. Most of the vibration velocity were identified at the 1,000 ${\mu}m/s$ or less. Using the vibration frequency and velocity measurements data, the load on the cast resin transformer analyzed the correlation of the burden. Therefore, this data could be found in the vibration characteristics of the light-load conditions. If the field measurements using the data perform diagnostics on the transformer, it's expected to be very effective.

• 전력전자학회논문지
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• 제17권6호
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• pp.539-545
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• 2012

Due to merits cost and efficiency, the transformer-less type photovoltaic (PV) inverters have been popularized in the solar market. However, the leakage current flowing through a parasitic capacitor between PV array and ground can cause adverse effect in the transformer-less PV system. In this paper, a bi-directional PV inverter with high efficiency and low noise is proposed for the PV system with an energy storage device. The proposed inverter is a transformer-less type and performs the bi-directional power control between dc sources and grid with high efficiency. In addition, the proposed inverter can suppress the leakage current and obtain low noise characteristic. Finally, 3-kW prototype was implemented to confirm validity of the proposed inverter.

• 전기학회논문지
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• 제56권5호
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• pp.884-891
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• 2007

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 and the high voltage gain characteristics for load variations in contact-less power supply (CPS). To consider these characteristics, in this paper, the efficiency characteristics of the contact-less power supply using a series resonant converter is presented, described and verified through theoretical analysis, computer simulation and experimental test of 2.5kW prototype.

• 전력전자학회논문지
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• 제7권6호
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• pp.563-569
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• 2002

본 연구는 60Hz 절연변압기가 없는 형태의 고주파링크방식의 계통연계형 PCS(Power Conditioning System)를 개발하였다. 본 시스템은 고주파 DC-DC 컨버터, 고주파 절연변압기, 풀브리지 다이오드 정류기, DC filter, 저주파 인버터, LC 필터로 구성되어 있다. 고주파 DC-DC 컨버터는 20kHz의 bipolar PWM 펄스를 발생시키며, 이 펄스는 고주파 절연변압기를 통해 승압되고, 풀브리지 다이오드를 통해 정류된다. 마지막으로 저주파 인버터를 통해 정현파 전류가 계통에 유입되게 된다. 제안한 고주파링크방식의 시스템은 기존의 60Hz 절연변압기를 사용하는 시스템 보다 많은 스위칭 소자가 사용되지만, 60Hz 절연변압기를 생략함으로서 시스템의 소형경량화 및 저가화를 이룰 수 있었다.

• 대한전기학회논문지:전력기술부문A
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• 제51권11호
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• pp.559-567
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• 2002

This paper presents the general recommendations for the overload criterions of mineral-oil-immersed distribution transformers rated 100kVA and less. For this purpose, we analyze the characteristics of top-oil temperature rising for mineral-oil-immersed power distribution transformer rated 100kVA and less, manufactured in Korea, In order to analyze the characteristics of top-oil temperature rising due to the distribution transformer loading, we performed experiments at KERI (Korea Electrical Research Institute) from December 2000 to May 2001. The restraint of ambient temperatures for the experiment results is solved using the results of foreign standards. Finally, we present the overload criterions of distribution transformer for summer and winter season, respectively.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.524-527
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• 2003

This paper describes control of the grid connected transformer-less type photovoltaic(PV) power conditioning system. which is simpler and more efficient than conventional transformer type systems. With modeling and analysis of PV system, the validity of the control strategy was verified by simulations and experimental results.