Equivalent Regulation Mechanism of Electron Density Distribution in Vacuum Arcs by Transverse Magnetic Fields and Contact Gaps

Abstract

Taking single-break dc vacuum circuit breakers as the research object, an experimental platform for collecting characteristic information of dc vacuum arcs was established. High-speed cameras were used to capture images of the zero-zone process of vacuum arcs under transverse magnetic fields (TMFs), flat contacts, and different commutation gaps. Spectrometers were employed to collect characteristic spectral lines at Cu I 521.8 nm, from which electron temperature and electron density were calculated and analyzed. The study found that under the same operating condition with a commutation gap of 6 mm, the swastika-shaped TMF contacts can effectively regulate the spatial distribution of arc plasma. Compared with the case without magnetic field, the radial distribution uniformity of electron density is significantly improved, and the ratio of electron density between the center and the edge on the cathode contact surface decreases from 7:1 to 1.6:1. Increasing the contact gap can improve the spatial distribution uniformity of electron density. The TMF gap (6 mm) and increasing the contact gap (10 mm) under no magnetic field conditions have equivalent regulatory effects on the radial/axial distribution of electron density. Both increasing the gap and enhancing the magnetic field improve the uniformity of plasma spatial distribution and reduce the difference in electron density between the center and edge of the contact surface. The TMF can equivalently replace increasing the gap to achieve stable arc control.