Performance of a Vacuum Arc Commutating Switch for a Fault-Current Limiter

A vacuum arc device with a hollow cylindrical anode and a button cathode located axially at the bottom of the anode has been evaluated theoretically and experimentally for use in a fault-current limiter as a commutating switch with an applied axial magnetic field. An optimally designed commutating switch of this type should meet the following conditions: 1) inductance of the parallel capacitor should be minimized, 2) time rate of increase for the applied magnetic field should be within an optimum range, 3) a slot in the anode is needed to provide for fast penetration of the magnetic field into the interelectrode region, and 4) anode size (radius and height) should be large enough to give a particle density and a commutation voltage of suitable magnitude for the duty expected.