Arc Transformation Characteristics of High Current Vacuum Arcs with Fixed Contacts under Combined Magnetic Fields

The objective of this work is to determine the arc transformation characteristics of the high current vacuum arcs with fixed contacts under combined magnetic fields. A novel TMF-AMF combined contact consisted of a pair of outer fixed cup-shaped AMF contact and a pair of inner moving cup-shaped TMF contact. The vacuum arc characteristics include the arc transformation characteristics, vacuum arcing behavior and the arc voltage. The arc current in the tests varied over a range from 0 to 30 kA at 50 Hz. The contact material was CuCr25 (25% Cr). A high-speed charge coupled device video camera was used to record the vacuum arc appearance. The experimental results show that the vacuum arc can transform from inner TMF contacts to the outer fixed AMF contacts successfully, which can reveal the effective function of the inner TMF contacts and the outer fixed AMF contacts, respectively. Moreover, the experimental results reveal that the current flew through the outer fixed contact was limited. The arc current mainly flew through the inner contact. When the fixed lower contact was cathode, the current transformed to the fixed contact more early, due to the moving characteristic of the cathode spot. This results will promote the application of the combined magnetic fields contacts.