• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.92-95
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• 2001

The dielectric breakdown of epoxy composites used for transformers was experimented and then its data were simulated by Weibull distribution probability. First of all, speaking of dielectric breakdown properties, the more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical. The breakdown strength of specimens with filler was lower than it of non-filler specimens because it is believed that the adding filler forms interface and charge is accumulated in it, therefore the molecular motility is raised and the electric field is concentrated. In the case of filled specimens with treating silane, the breakdown strength become much higher Finally, from the analysis of weibull distribution, it was confirmed that as the allowed breakdown probability was given by 0.1[%], the applied field value needed to be under 21.5 [Mv/cm].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.159-163
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• 2003

In this study, the DC dielectric breakdown of epoxy composites used for PCB material was experimented and then its data were simulated by Weibull distribution equation. The more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical, and the breakdown strength of specimens with filler was lower than it of non-filler specimens because it is believed that the adding filler forms interface and charge is accumulated in it, therefore the molecular motility is raised, the electric field is concentrated, and the acceleration of electron and the growth of electron avalanche are early accomplished. From the analysis of Weibull distribution, it was confirmed that as the allowed breakdown probability was given by 0.1[%], the applied field value needed to be under 21.5[kV/mm].

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.3
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• pp.305-310
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• 2010

DC electricity feeder system operating in the urban railway is typically a feedback circuit consisted of the contact wire and electric railway vehicle via rail. But stray current is flowed on a structure that is not part of the intended electrical circuit with respect to a given structure. This paper presents comparison analysis of field test cases based on criteria of electrolytic corrosion protection of buried metallic structures adjacent to DC traction systems. As a result of it, we confirmed that measurement methods are different from each other about the same tests. Therefore measurement methods to prevent electrolytic corrosion need to establish electrical facilities standards to be applied domestic.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.142-147
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• 2018

Private electrical facilities are judged whether it is suitable for the insulation aging condition of their incoming underground cables using DC leakage current test method. In the case where the service point of utility is the secondary side of cut out switch installed in the electric pole, there is a problem that it is difficult to separate the lightning arresters(LA) because of their high position of the pole. Therefore, the field test voltage is applied at value lower than DC 30 kV, which are stated in the inspection guideline. However, this test could reduced the insulation performance of the LA by accelerating the electrical stress of the metal oxide varistor element in the pre-breakdown region. In this study, we analyzed the relationship between the DC test voltage and the leakage current using the non-destructive DC high voltage equipment with leakage current measurement function. The results show that the leakage current increases sharply above the specified test voltage. As a consequence, it could be contributed to improve insulation aging inspection method by selecting the possible test area on the VI characteristic curve of the pre-breakdown area of the LA.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.3
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• pp.222-226
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• 2021

To comply with CE marking requirements, the electromagnetic compatibility (EMC) and low-voltage directive (LVD) tests are conducted on the sub-racks of International Thermonuclear Experimental Reactor (ITER) AC/DC converters and bypass switches. The EMC tests consist of a series of tests, including the electromagnetic interference test, the electromagnetic field immunity test, and the rapid transient burst immunity test. In the LVD test, the electric shock protection test, the xcessive temperature limit and heat resistance of equipment tests, and the fire spread prevention test are performed. This work presents and reviews the European Directive for EMC/LVD and introduces the methods of EMC and LVD tests for the sub-racks of AC/DC converters and bypass switches. It also evaluates the test method and results to meet the European Directive requirements for CE marking. The sub-racks of ITER AC/DC converters and bypass switches successfully pass the EMC and LVD tests.

• Journal of Plant Biology
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• v.29 no.1
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• pp.1-10
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• 1986

Intra- and inter-specific protoplast fusion of tobacco (Nicotiana tabacum cv. Virginia 115) and pea (Pisum sativum cv. Sparkle) were carried out in highly inhomogeneous alternating electric fields. Under the electric field of alternating current (AC, sine wave), 600 V/cm and 800 kHz for tobacco protoplast, and 600 V/cm and 700 kHz for pea protoplasts, the protoplasts were aggregated in pearl chains. Intra-specific protoplast fusions were most effectively induced within the aggregates of tobacco and pea, respectively, by the additional application of a single high field pulse of direct current (DC, square wave) at 1 kV/cm for 50 $mutextrm{s}$. Inter-specific fusions between protoplasts of the two plants were most effectively induced in the electric field of 600 V/cm and 700 kHz, and square wave pulse at 1 kV/cm for 50 $mutextrm{s}$. The duration of the pulse over the electrical breakdown voltages was simulated from 1 to 100 $mutextrm{s}$ in both tobacco and pea protoplast. The yield of the electrofusion products was significantly high (above 60%), compared with that (20%) of the standard fusion method by polyethylene glycol (PEG) 4,000, and the viability of electrofused protoplasts was above 70%, but that of PEG-fused protoplasts 8~16%, when determined by Evan's blue staining method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.442-450
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• 2001

Experiments were carried out on agglomeration of bipolarly charged particles in an alternating current electric field. Laboratory-scale setup was built and experiments were conducted at atmospheric condition. DOS(Di-octyl Sebacate) particles with 100% purity were generated by an atomizer. The particles were branched into two, each of which passed through a wire-to-plate type charging section where a positive or a negative DC high voltage was applied and was charged positively or negatively. These bipolarly charged particles together passed through an agglomeration section where an $\pm$20kV AC power was applied between two plates. The resident time in the agglomeration section was adjusted as l sec. Particle sampling was made by a cascade impactor (MOUDI). The effect of agglomeration system on the reduction ratio of particles below l ㎛ was 42∼45%. Effect of AC frequency on the particle size distribution was found insignificant.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.264-266
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• 2008

DC transit system has been adopted in the metropolitan area, Korea since 1974. EMU in this system always reiterates that acceleration and retardation. When EMU decelerates using electric breaking, regenerative power occurs. Regenerative power can be consumed in vicinity EMU on the same line or in resistor. If DC transit system has inverter for reusing regenerative power, Energy efficiency in DC transit system will be increased. This paper present a scheme to set up the starting voltage for the developed inverter and its field test result.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.306-311
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• 2005

In this paper, the electromagnetic force acting in the arc column of 3 different extinction units is compared with using the FEM (Finite Element Method) and the arc velocity is calculated by the drag force of the fluid mechanics. The experiment for breaking the arc current was performed in each model at 100 volts in order to measure the arcing time. The outcome was compared with the computing value. As a result, this paper proposes that the divided U-shaped grid is able to shorten arcing time and improve the electric performance. It also suggests a methodology for comparing and analyzing the result obtained by simulation and experiment.

• Korean Journal of Veterinary Research
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• v.35 no.1
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• pp.179-185
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• 1995

The fusion rates of nuclear transplant embryos with various DC voltage were 55.6-79.2%. The significantly higher fusion rates of nuclear transplant embryos were achieved at the electric field strenght of DC 1.0-2.0kV/cm(72.0-79.2%) than DC 0.75kV/cm(55.6%, P<0.05). No significant differences in the percentage of embryos that cleaved(48.1, 55.4 and 42.6% respectively) and the percentage of cleaved embryos that developed to morulae/blastocyst(1.9, 5.3 and 1.9% respectively) could be found among the three types of in vitro culture system (Granulosa cell, BOEC co-culture and SOF, P>0.01). The age of the recipient cytoplast(30 vs 40hr) had no effect on the fusion rates and the rates of cleavage development(36.9 vs 44.1%, P>0.01).