Prestrike Characteristics of Single-Break Vacuum Circuit Breakers With Cup-Type AMF Contacts and Spiral-Type TMF Contacts Under Inrush Current Conditions

Switching shunt capacitor banks is a challenging task for vacuum circuit breakers (VCBs). The objective of this article is to experimentally investigate the prestrike characteristics of single-break VCBs with cup-type axial magnetic field (AMF) contacts and spiral-type transverse magnetic field (TMF) contacts under inrush current conditions in four ways. These four aspects are: the prestrike gap probability distributions, the inrush current interruption phenomena, the prestrike electric field, and the contact erosion. The contact erosion is represented by the field enhancement factor
$\beta $
, which is obtained by the field emission current. The experimental results show that compared with the cup-type AMF VCB, the spiral-type TMF VCB is more effective since it can reduce 47.4% of the 50% prestrike gap,
$d_{50}$
, and 28.6% of the scatter in prestrike gaps, which is mainly because the spiral-type TMF VCB can effectively reduce the contact erosion caused by inrush current. The spiral-type TMF VCB can significantly reduce the occurrence probabilities of inrush current interruption. The spiral-type TMF VCB can reduce 48.6% of the 50% prestrike arc time,
$t_{a50}$
. The 50% prestrike electric field,
$E_{\mathrm {pre50}}$
, of the spiral-type TMF VCB is 125% higher than that of the cup-type AMF VCB. For the controlled switching of capacitor banks, the spiral-type TMF VCB is superior to the cup-type AMF VCB.