Intermediate-frequency vacuum arc movement on TMF contacts

In this paper, the morphological changes at intermediate frequency (400Hz~800Hz) were investigated under transverse magnetic field (TMF). The experiment was performed on a cup-type TMF contact with a contact diameter of 66mm and a contact gap of 4mm in single-frequency circuit. With high-speed photography, three different arc modes were identified: arc column expansion, arc column movement and diffuse arc. At the arc column expansion mode, the arc column is immobility and the diameter of arc column increases with the increasing current. At the arc column movement mode, arc velocity between 10m/s - 100m/s was observed. The arc column expansion mode plays an important role in the anode erosion in the intermediate-frequency vacuum arc. Furthermore, the arc velocity increases almost linearly with the total current at the same frequency. As the current frequency increase, the arc velocity also increases at the same current.