Spectroscopic Analysis of Anode Surface Thermal Emission With Single and Dual Vacuum Arc Columns

The objective of this article is to determine the anode surface temperature during and after current zero (CZ) with single and dual vacuum arc columns. Both the alternating current (ac) and pulsed direct current (dc) waveforms were applied with a peak value of 5-16 kA. A butt-type electrode and a horseshoe-type electrode were utilized to generate single and dual vacuum arcs. In the draw arc experiment, three spectrometers with working wavelengths of: 1) 200-1000 nm; 2) 880-1700 nm; and 3) 1600-2400 nm, a fast thermography camera, and two high-speed cameras were used for optical analysis. Based on the experimental results, it was certified that spectroscopic analysis with the Planck fitting procedure is an effective method to determine the anode surface temperature after CZ. The most preferable wavelength of the spectrometer in anode temperature determination was 800-1900 nm. The temperatures of anode spot 1, anode spot type 2, and footpoint mode were 3200-3300, 3800-4000, and 3000-3100 K, respectively. Two kinks appeared in the anode temperature cooling curve. The corresponding temperature was the liquidus temperature of the electrode material and the melting point of copper. Besides, two hot areas on the anode surface were observed for the horseshoe-type electrode. The anode temperature tended to be homogeneous at about 0.8 ms after CZ.

I. Introduction

The anode thermal process is a complex physical interaction between the energetic input, electrode material, and arc plasma. It is crucial for the performance of vacuum interrupters (VIs) such as the withstand voltage capability, current interruption capability, and electrical lifetime of VIs [1]–[3]. Strong energetic input to the anode would result in a large amount of metallic vapor evaporation into the electrode gap. This will lower the dielectric strength recovery process after current zero (CZ). Besides, the anode surface is further deformed due to inhomogeneous local overheating and material loss of the electrode. Severe anode surface deformation not only lowers the withstand voltage level but also decreases the electrical lifetime of VIs. Therefore, anode thermal process observation is of great significance.