Arc Voltage as a Source of Information About Arc Burning on AMF Contacts

The aim of the work is analysis of current-voltage characteristics (CVCs) of vacuum arc for the high-current pulse. The arc was ignited by the opening of the electrodes and was fed with half-sine current pulse of 10-ms duration. CuCr axial magnetic field (AMF) contacts were used. Investigations for each contact system were performed in the range of arc currents up to the levels of guaranteed failure when transient recovery voltage (TRV) applied. Oscillograms of current and arc voltage were compared with the results of high-speed video. We propose a method for compact presentation of video filming in the form of Xt-diagrams. It is shown that analysis of CVCs allows determining the ignition character and duration of arc development stage. Correlation between durations of arc development and magnetic field setting has been found. We have found out that the nature of the ignition does not affect the state of the developed arc in the investigated contact systems. We conclude that neither voltage oscillograms nor CVCs can determine the onset of evaporation from anode, and the very presence of evaporation from anode is observed also at currents that are significantly below failure ones and is not a failure criterion.