The Characteristics of Vacuum Arc in the Process of DC Interruption Using Butt Contacts and TMF Contacts

The application of vacuum interrupters in dc current interruption highlights the interdependence of the contact design and the arc behavior. In this investigation, the characteristics of drawn vacuum arc in the process of dc load current interruption using butt contacts and a commercial transverse magnetic field (TMF) contacts were recorded with a high-speed camera. In a drawn vacuum arc, the arc sequence began with one or two bridge arc columns formed after the rupture of the molten metal bridge. Parallel columns in the butt contact were observed for not more than half of the trials, whereas an intermediate stage of two parallel columns was always found in the TMF contact. The interruption tests indicated that the arc in two columns mode occupied more surface had higher interrupt capability. The role of the slots on TMF contact to the arc appearance was discussed. It can be concluded that, for dc load current interruptions below 5 kA, if a short break time (<;1 ms) is required, a TMF contact is preferred; if there is no special break time required then a butt contact is preferred.