Time/current characteristics and breaking capacity of experimental vacuum fuses

Conventional HV fuses, which are filled with quartz sand, have an excellent current-limiting capability, but they have a zone of uncertain operation in the low overcurrent range. To overcome this disadvantage, substituting of the quartz sand by a vacuum was considered. In particular, a vacuum fuse can be designed by inserting a fusible element between the fixed butt contacts (electrodes) of a vacuum chamber. Melting curves and the arc quenching capability at current zero are investigated for a simply designed vacuum fuse with flat contacts. Variables are the current amplitude, the electrode material, the diameter of the fuse wire, and the distance between the electrodes. These results show that it is possible to design an operable vacuum fuse with a simplified electrode configuration. The time/current characteristic is strongly influenced by the length of the fuse wire