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Kinzan, South Korea

Park J.-J.,Joongbu University
Transactions on Electrical and Electronic Materials | Year: 2013

The effects of electric field frequency on the AC electrical treeing phenomena in an epoxy/layered silicate (1.5 wt%) were investigated in a needle-plate electrode arrangement. A layered silicate was exfoliated in an epoxy-base resin with AC electric field apparatus. To measure the treeing initiation and propagationand the breakdown rate, a constant alternating current (AC) of 10 kV with three different electric field frequencies (60, 500, and 1,000 Hz) was applied to the specimen in the needle-plate electrode specimen in an insulating oil bath at130°. At 60 Hz, the treeing initiation time was 12 min, the propagation rate was 0.24 × 10-3 mm/min, and the morphology was a dense branch type. As the electric field frequency increased, the treeing initiation time decreased and the propagation rate increased. At 1,000 Hz, the treeing initiation time was 5 min, the propagation rate was 0.30 × 10-3 mm/min, and the morphology was a dense bush type. © 2013 KIEEME. All rights reserved.


Park J.-J.,Joongbu University
Transactions on Electrical and Electronic Materials | Year: 2013

The effects of particle size on the mechanical and electrical properties of epoxy/spherical silica composites were studied. The silica particle sizes were varied from 5 to 30 μm and the filler content was fixed to 60 wt%. Tensile and flexural tests were carried out and the interfacial morphology was observed by scanning electron microscopy (SEM). The electrical insulation breakdown strength was estimated using sphere-sphere electrodes with different insulation thicknesses of 1, 2 and 3 mm. The tensile strength and flexural strength increased with decreasing particle size, while electrical insulation breakdown strength increased with increasing particle size. Copyright © 2013 KIEEME. All rights reserved.


Park J.-J.,Joongbu University
Transactions on Electrical and Electronic Materials | Year: 2013

In order to develop high voltage (HV) insulation materials, epoxy/spherical alumina composites with two different particle sizes (in μm) were prepared and a dynamic mechanical analysis (DMA) and electrical insulation breakdown strength test were carried out in sphere-sphere electrodes and the data were estimated using Weibull statistical analysis. Alumina content varied from 50 to 70 wt%. The electrical insulation breakdown strength for epoxy/alumina (50 wt%) was 44.0 kV/1 mm and this value decreased with increasing alumina content. The effects of insulation thickness and alumina particle size on the insulation breakdown strength were also studied. The insulation thickness varied from 1 mm to 3 mm, and the particle sizes were 7.3 or 40.3 μm. © 2013 KIEEME. All rights reserved.


Park J.-J.,Joongbu University
Transactions on Electrical and Electronic Materials | Year: 2013

The effect of the mixing ratio of spherical silica on the electrical insulation breakdown strength in an epoxy/silica composite was studied. Spherical silicas with two average particle sizes of 5 μm and 20 μm were mixed in different mixing ratios, and their total filling content was fixed at 60 wt%. In order to observe the dispersion of the silicas and the interfacial morphology between silica and epoxy matrix, scanning electron microscopy (SEM) was used. The electrical insulation breakdown strength was estimated in sphere-sphere electrodes with different insulation thicknesses of 1, 2, and 3 mm. Electrical insulation breakdown strength decreased with increasing mixing ratio of 5/20 μm and the thickness dependence of the breakdown strength was also observed. © 2013 KIEEME. All rights reserved.


Park J.-J.,Joongbu University
Transactions on Electrical and Electronic Materials | Year: 2013

In order to develop electrical insulation material, organically modified layered silicate was incorporated into an epoxy matrix to prepare nanocomposite. Transmission electron microscopy (TEM) observation showed that organophillic clay was in an exfoliated state, while hydrophilic clay was not dispersed into nanolayers within the epoxy matrix. Epoxy/organophilic clay (2.8 wt%) nanocomposite was mixed and cured at 150°C for 4.5 hr. I-V characteristics, volume resistance and dielectric properties for the cured nanocomposite were estimated. Current density increased with increasing temperature, and volume resistance decreased with increasing temperature, in neat epoxy and epoxy/ organophilic clay (2.8 wt%) nanocomposite. As frequency increased, the dielectric loss value decreased in the two systems. Copyright © 2013 KIEEME. All rights reserved.

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