520 / 2017-05-11 12:46:01

Fractal Features of Contact Surface Ruptured from Arc Welding by High Frequency Inrush Current in Vacuum Interrupters

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A prestrike high frequency inrush current arc will cause a local contact surface melting and welding in capacitive making of vacuum interrupters. The contact surfaces may be seriously damaged from a rupture of the contact welding during the next breaking operation, which has a negative effect on restrike. A fractal characteristic can be used to describe such irregular ruptures. A 3D laser microscopy was used to obtain the images of the contacts’ rupture surfaces after subjected to different amplitudes inrush current. Two different contact materials (CuCr50/50 and CuW10/90) were used in the experiment. Then box-counting method is used to evaluate the images’ fractal dimension. It revealed the morphological features and formation regularity of the contact ruptures. The results can reveal the contact erosion patterns for the two contact materials.