Influence of Magnetic Fields on Inrush Current Prestrike Arc Behaviors of Vacuum Interrupters

In the case of back-to-back capacitor banks switching, the inrush current arcs can locally melt the contact surfaces of interrupters during prestrike processes. The magnetic field of the contact would influence the behaviors of the inrush current prestrike arcs. The objective of this paper is to determine the influences of cup-type transverse magnetic field (TMF) and cup-type axial magnetic field (AMF) contacts on prestrike arc behaviors of vacuum interrupters (VIs) during capacitive making processes. The inrush current arc behaviors were observed by a high-speed camera. The contact diameter of the VIs was 48 mm. The insulating envelope of the VIs was transparent and there was no metal vapor shield inside the VIs for observation of prestrike arcs. Two types of cup-type vacuum interrupter contacts with different magnetic field structures (TMF and AMF) were used. The prestrike arc observations indicate that the cup-type AMF contacts are superior than the cup-type TMF contacts because of less damages of the prestrike arcs to the contact surfaces.