Comparison of Vacuum Arc Behaviors for Slot-Type Axial Magnetic Field Contacts With and Without Iron Plates

In order to investigate the influence of ferromagnetic-material-enhanced axial magnetic field (AMF) on high-current vacuum arc behaviors for a slot-type AMF contact, we experimentally compared the following vacuum arc behaviors between slot-type AMF contact with iron plates and that without iron plates, which include diffuse mode interval before current zero, arc modes at current peaks, and arc energy. The contact diameters were 48, 58, and 66 mm, and the contact gaps were 8 and 14 mm, respectively. The AMF contacts were fixed in a demountable vacuum chamber, and the vacuum arcs were initiated by a trigger electrode. The experimental current peak values ranged from 2.5 to 21.8 kA. The experimental results show that, with a high contact diameter of 66 mm, a stronger AMF contributes to keep the diffuse mode interval before current zero longer, and it contributes to keep the vacuum arcs at current peaks in diffuse modes until higher current values. However, with the low contact diameter of 48 mm and contact gap of 14 mm, the enhanced AMF constricts the vacuum arcs. Based on the results, an AMF window is suggested. Within the AMF window, the vacuum arcs are considered to keep longer diffuse mode interval before current zero, and the arcs have higher transition current value to high-current modes. The arc energy decreases with the enhanced AMF, significantly in the high-current range. Furthermore, it is suggested to apply iron plates in the high diameter slot-type AMF contacts. However, it does not recommend applying iron plates in the low contact diameter contacts.