Experimental Study on the Effects of Different Contact Structures on Cathode Spots in Vacuum Arcs

The relationship between magnetic contact configuration and vacuum-arc morphology was investigated using high-speed imaging. Three configurations were compared at a fixed gap of 6 mm and a peak current of 6 kA: a wan-type transverse-magnetic-field (TMF) configuration, an oblique-slot TMF configuration, and a hybrid oblique-slot TMF cathode/coil-type axial-magnetic-field (AMF) anode. The oblique-slot configuration showed more pronounced directional motion and local luminous concentration than the wan-type configuration. The hybrid configuration exhibited a more dispersed multispot distribution in the images at 3–7 ms. Separate gap and peak-current comparisons were then conducted only for the wan-type TMF configuration. At 6 kA and t = 5.0 ms, increasing the gap from 6 to 12 mm reduced the identifiable luminous-region number and total luminous area by 43.8% and 63.1%, respectively. At a 6 mm gap and the same instant, increasing the peak current from 4 to 10 kA increased these quantities by 83.1% and 65.1%, respectively; however, the total area at 10 kA was smaller than at 8 kA. The results characterize resolvable luminous spots and spot groups in fixed-gap, triggered discharges and provide comparative information for contact design. They do not directly quantify microscopic emission sites, surface erosion, or interruption performance.