Vacuum fault current limiter

Claim 1

A fast acting current limiting vacuum device which is operable to limit high voltage, high current line faults comprising: an insulated evacuated enclosure; a pair of contacts disposed within said insulating evacuating enclosure, movable between a closed position completing an electric connection path through the enclosure and an open position wherein the contacts are spaced apart forming an arcing gap therebetween across which an arc is formed; means for rapidly separating the pair of contacts to a spacing sufficient to permit an applied transverse magnetic field to produce an arc current zero and to prevent restriking of the arc across the separated contacts; impedance means connected external to the enclosure in parallel across the contacts whereby the shunted fault current can be limited; magnetic field means disposed to produce a magnetic field transverse to the arc formed between the separated contacts, which transverse magnetic field is generated after the contacts are separated a distance which permits the arc between the contacts to be rapidly extinguished, and which magnetic field rapidly increases the potential across the contacts to cause the fault current to be shunted to the parallel current limiting impedance path.