• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.7
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• pp.20-28
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• 2009

This paper presents the design of zero current switching ZCS pulse frequency modulation type DC-DC converter for magnetron power supply. A magnetron serving as the microwave source in a microwave oven is driven by a switch mode power supply (SMPS). SMPSs have the advantages of improved efficiency, reduced size and weight, regulation and the ability to operate directly from the converter DC bus. The demands of the load system and the design of the power supply required to produce constant power at 4[kV]. A magnetron power supply requires the ability to limit the load current under short circuit conditions. The current source series resonant converter is a circuit configuration which can achieve this. The main features of the proposed converter are an inherent protection against a short circuit at the output, a high voltage gain and zero current switching over a large range of output power. These characteristics make it a viable choice for the implementation of a high voltage magnetron power supply.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.115-116
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• 2006

Since the discovery of the high-temperature superconductors, many researches have been performed for the practical applications of superconductivity technologies in various fields. As results, significant progress has been achieved. Especially, Superconducting Fault Current Limiter (SFCL) offers an attractive means to limit fault current in power systems. The SFCLS, in contrast to current limiting reactors or high impedance transformers, are capable of limiting short circuit currents without adding considerable voltage drop and energy loss to power systems during normal operation. Under fault conditions, a resistance is automatically inserted into the power grid to limit the peak short-circuit current by transition from the superconducting state to the normal state, the quench. The advantages, like fail safe operation and quick recovery, make SFCL very attractive, especially for rapidly growing power systems with higher short-circuit capacities. In order to verify the effectiveness of the SFCL, in this paper, the analysis of fault current and voltage stability assessment in a sample distribution system and a transmission system are performed by the PSCAD/EMTDC based simulation method. Through the simulation, the advantage of SFCL application is shown, and the effective parameters of the SFCL are also recommended for both distribution and transmission systems. A resistive type component of SFCL is adopted in the analysis. The simulation results demonstrate not only the effectiveness of the proposed simulation scheme but also SFCL parameter assessment technique.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.147-150
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• 2004

Maximum power point tracking for PV systems traditionally uses either perturbation and observation method or incremental conductance method. Both methods require modulation of the output voltage and this leads to significant power loss. In this paper, a method, which senses output circuit voltage and short circuit current and use the above two parameters for optimum control with a fuzzy controller, is introduced. The short circuit current of PV cell represents illumination, and the output circuit voltage carry on information about the temperature. PCS(power conditioning system) is controlled not only feed to inverter for stability voltage variation despite of variety external environment, but also operate in order to feeding voltage and current at maximum power point by boost type chopper.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.38-40
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• 2002

A study on the test method and the test facilities of synthetic capacitive current tests have been very slight and the direct test method with the short-circuit generator and power transformer only used up to now. However, according to the development of analysis technique of power system and design and manufacture technique we are realized that direct testing method is not satisfactory to evaluate the performance of circuit-breaker because it is difficult to simulate precisely the conditions of power system. Therefore, in order to solve these problem this paper deals with the tests methods and the design technique of the tests facilities of the synthetic capacitive current based on the same theory with the synthetic short-circuit tests.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.873-879
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• 2016

A charge pump circuit with very short turn-on time is presented for minimizing reference spurs in CMOS PLL frequency synthesizers. In the source switching charge pump circuit, applying proper voltages to the source nodes of the current source FETs can significantly reduce the unwanted glitch at the output current while not degrading the rising time, thus resulting in low spur at the synthesizer output spectrum. A 1.1-1.6 GHz PLL synthesizer employing the proposed charge pump circuit is fabricated in 65 nm CMOS. The current consumption of the charge pump is $490{\mu}A$ from 1 V supply. Compared to the conventional charge pump, it is shown that the reference spur is improved by dB through minimizing the turn-on time. Theoretical analysis is described to show that the measured results agree well with the theory.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.39-43
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• 2019

The breaking of a circuit in DC grid could pose a challenge because of the absence of zero-crossing instant for both current and voltage when a fault occurs. An additional fault current limiting function will be very helpful for reducing the burden of the DC circuit breaker by limiting the fault current to a reasonable value. In this paper, we studied the overcurrent characteristics of several HTS conductors so that we could use the selected conductors for the basic design work of a resistive type fault current limiting module as a part of the circuit breaking system. According to the short-circuit test results, we suggested and compared two different basic design parameters of the HTS fault current limiting module, which will be connected in series to the DC circuit breaker.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.20-28
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• 2007

This paper describes an analytical method to determine the short-term ratings to reliably operate the overhead transmission lines with double-circuit lines when faulting one circuit of the two. As linearizing the thermal equilibrium equation that represents the temperature characteristic of conductors, we show that the linear equation can be easily represented the over-current and it's temperature property during overloading the one line. Generally, it is well hewn that the short-term line ratings should be determined by considering both conductor life and dip. However, most power companies have their own different guides for the short-term ratings. Using the suggested method in this paper, it can be re-accessed the short-term ratings given in Kepco's overhead transmission lines constructed during the past three different periods. As a result, it is verified that the short-term ratings could be increased mil efficiently. Furthermore, it would be directly applied the given method to determine the short-term dynamic line ratings when occurring faults in one of the double-circuit lines, without doing my other actions for the current lines.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.3
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• pp.255-260
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• 2002

Recently, the occurrences of electrical fire have been suppressed by an earth leakage breaker(ELB), a no fuse breaker(NFB) and a fuse in case of an earth leakage, a short circuit and an over current. But it is impossible for the ELB to break the circuit in the case of the failure of pressure contacts on connecting points and the momentary short circuit. Therefore, it is require to study the constructive problem of the ELB. In this paper, we have developed the auxiliary control device, electrical fire prevention control device(EFPCD), of the ELB. And we have tested the operation characteristics of the ELB according to the load(R, L) As a result of this experiment, we could prevent the electrical fire due to the spark and the overheat occurring in the failure of pressure contacts on connecting points and the momentary short circuit.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.90-95
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• 2009

The application of a large power transformer into a power distribution system was inevitable due to the increase of power demand and distributed generation. However, the decrease of the power transformer‘s impedance causes the short-circuit current of the power distribution system to increase and thus, the higher short-circuit current exceeds the cut-off ratings of the protective devices such as a circuit breaker. To solve these problems, several countermeasures have been proposed to protect the power system effectively from the higher fault current and the superconducting fault current limiter (SFCL) has been expected to be the promising countermeasure. However, the current limiting effect of SFCL including its bus voltage drop compensation depends on SFCL's application location in a distributed power system. In this paper, the current limiting and the bus-voltage drop compensating characteristics of the SFCL applied into a power distribution system were studied. In addition, the quench and the recovery characteristics of the SFCLs in each location of the power distribution system were compared each other.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.6
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• pp.287-292
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• 2001

This paper deals with the configuration, operating principles, systematic calculation method of parameter and optimization method of test circuit for parallel current injection method, series voltage injection method and hybrid synthetic test method as the method for performance test of circuit breaker with extra high interrupting capacity. The test method depicted above is applied to short-circuit making and breaking test (operating sequence :Os CdOs, Od-CdOs) and out-of-phase tests(operating sequence :Os, CdOs) for performance test of the newly-developed 420kV, 50kA and 800kV 50kV puffer-type gas circuit-breaker according to IEC 60056 and IEC 60427. The testing results, evaluation of equivalence for test and analyzed results are also presented in this paper.