• Resources Recycling
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• v.11 no.5
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• pp.30-33
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• 2002

Recently in the progress of electronic equipment, power transformer was considered an important part. To make power transformer with miniaturization, lightening, low Power, we need a high efficiency core material. In this paper, we added $V_2$$O_{5}$ and $CaCo_3$ to Mn-Zn Ferrite to make a high efficiency, low loss core material. The compositions are MnO : ZnO : $Fe_2$$O_3$=37 : 11 : 52 mol%. They were sintered at 1250 for Three hours. Initial permeability was measured at 0.1 MHz. At 200 mT, Power loss was measured by temperature changing at 25 KHz, 50 KHz, 100 KHz. When we added $V_2$$O_{5}$ and $CaCo_3$, 0.08 wt%, 0.05 wt% respectively, we get 415 ㎾/㎥ at 200 mT, 100 KHz, $60^{\circ}C$. We can reduce eddy current loss as a main loss of high frequency by addition of a little mount of $V_2$$O_{5}$ $CaCo_3$. So we can decrease the power transformer's power loss.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.34-38
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• 2006

There are many parameters that should be considered from the viewpoint of real power system operation and planning in designing HTS power devices. Especially, in the power system with HTS-FCL(fault current limiter) and TR(transformer), there is close correlation between parameters of the HTS power devices. This paper describes some considerations in determining parameters of HTS power devices, which are related to technical and economical aspects. The main parameters in this study are the quench resistance of HTS-FCL and the % impedance of HTS-TR. The results may give basic information for developing the devices.

• Analytical Science and Technology
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• v.18 no.5
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• pp.410-418
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• 2005

PCBs had numerous uses such as hydraulic fluid, heat exchange fluid, sealant, lubricant, and carbonless copy paper. They are most likely found in electric utilities, power stations, industrial facilities, electronic manufacturing plants, petrochemical plants, railroad systems, electric equipment repair facilities, mining sites (active or abandoned), and military camps. Due to its outstanding chemical and thermal stabilities and electrical insulation properties, the commercial and industrial products of PCBs, such as Aroclors, Kaneclors, Clophens, Phenaclors etc., had been widely used as thermal oil and transformer oil from 1930s until the 1970s. The transformer oils were analyzed as a main source of polychlorinated biphenyls (PCBs) emission into the environment. Qualitative estimation of oil extracts as carried out with Aroclor 1242, 1248, 1254, 1260. The transformer oils contained the pure and mixed of Aroclor 1242, Aroclor 1254, and Aroclor 1260. Also, commercial screening kit of 20 ppm and 50 ppm were applied to the transformer oil samples.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1305-1309
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• 2013

The application of the superconducting fault current limiter (SFCL) in a power distribution system is expected to contribute the voltage-sag suppression of the bus line as well as the fault-current reduction of the fault line. However, the application effects of the SFCL on the voltage sag of the bus line including the fault current are dependent on its application location in a power distribution system. In this paper, we investigated the fault current limiting and the voltage sag suppressing characteristics of the SFCL due to its application location such as the outgoing point of the feeder, the bus line, the neutral line and the 2nd side of the main transformer in a power distribution system, and analyzed the trace variations of the bus-voltage and fault-feeder current. The simulated power distribution system, which was composed of the universal power source, two transformers with the parallel connection and the impedance load banks connected with the 2nd side of the transformer through the power transmission lines, was constructed and the short-circuit tests for the constructed system were carried out. Through the analysis on the short-circuit tests for the simulated power distribution system with the SFCLs applied into its representative locations, the effects from the SFCL's application on the power distribution system were discussed from the viewpoints of both the suppression of the bus-voltage sag and the reduction of the fault current.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.3
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• pp.56-61
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• 1996

In this paper, new buck converter of a TV power system is presented. First, we devised a revised driving circuit for an emitter-coupled type buck converter, by which it is possible to reduce the material cost of transformers and voltage stress of power device. Secondly, we adopted a hybrid oscillation technique. When TV system is in off-stage, initial standby power which is necessary for remote controllable TV system is supplied by self-oscillating mode. Main power which is necessry in TV system bing on state is provided by an externally triggered oscillating mode. The switching frequency is synchronized to the oscillating frequency of horizontal deflection in TV, by which we can reduce picture noises and the size of power transformer. Thirdly, a simple error amplifier is inserted to the feed-back loop to keep the output voltage constant which means pulse width modulatio mode is added in driving part of power device. Finally, we showed by experiments that our proposed converter performs well enough to be close to the theoretically predicted values.

• Journal of the Korean Society of Safety
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• v.31 no.5
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• pp.16-21
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• 2016

The purpose of this paper is to conduct ETA on 15 components of power installations: the DS/LBS, LA, MOF, CT, PT, A/V meter, VCB, OCR, COS, PF, Transformer, Condenser(C), Grounding, Cable and Connector. To achieve that, power installations work flow and its components are categorized. Based on performance, human, environmental, management, and safety, this paper drew Initiation events (IE) and End states (ES). ETA is applied to the main functions of each component, and the end states that may occur in one initiation event are suggested. In addition, detailed classification was performed to induce various end states on the basis of the suggested initiation events. If the suggested IEs and ESs are applied on the basis of power installations event cases, it is expected to prevent the same kinds of accident and operate power installations safely.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.858-863
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• 2007

With increase of load power the case it will not be able to supply the power which is necessary to the vehicle, it establishes dosage increase of main transformer of substation or power compensation equipment, and must supply the power which is necessary. But like this method the expense and the hour when it is considerable are necessary. As an alternative plan, if neighborhood substation can supply power through parallel feeding then it can supply power applying the equipment of existing. So we investigate the possibility of parallel feeding method between neighboring substations through measuring results of voltage phase difference and analysing feeding circuit,

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1885-1887
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• 2000

In this paper we introduce preventative and diagnostic systems developed to prevent substations from accidental fault of electric power transmitting apparatus. We propose monitoring and diagnostic system for ultra high voltage GIS and main transformer of 765kV substations as an example of preventative and diagnostic techniques being applied in Korea. We also present a guideline to construct and manage an expert system for this purpose. Finally, an engineering solution as a substation management support system is proposed.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.948-953
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• 2011

In AC railway feeding system, three phase received from the network is changed to two phase power sources with different phases. The main circuit breaker installed train is automatically open by track signal when the train passes the neutral section. In order to continuously supply power source to train, the changeover system was used in Japan. Therefore, the train is able to operate under powering condition when it was passing through the neutral section. We investigated the control method to reduce the inrush current flowing main transformer in train. To examine the inrush current and operate the static semiconductor switch such as thyristor, we manufactured the small scale the changeover system and carried out performance tests.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.370-373
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• 2002

A new phase shift full bridge converter(PSFB) with serially connected two transformers is proposed. It is well suited for applications in the communication equipment of a few hundred watts. The main features of the proposed converter are a wide input voltage range, an easiness to meet the requirement for zero voltage switching (ZVS) condition at a light load, and a small output voltage ripple. Furthermore, it features high power density since serially connected two transformers can replace both a main transformer and an output inductor. A mode analysis and experimental results are presented to verify the validity of the proposed converter.