Two-wire preionizer for surge voltage arresters

Claim 2

An overvoltage protective device comprising a pair of spaced main electrodes, mounting means for supporting said main electrodes in a predetermined spaced-apart relationship thereby to define a surge voltage discharge sparkgap between the main electrodes, a preionizer for ionizing said discharge sparkgap, means for supporting said preionizer adjacent the discharge sparkgap in operating relationship thereto, said preionizer comprising two electrically conductive wires, at least one of said wires having an insulating coating on the outer surface thereof, said wires being twisted together adjacent a first one of the respective ends thereof thereby to hold said first ends of the wires in close proximity to one another, the first ends of said wires that are held in close proximity to one another being uninsulated and separated by said insulating coating so that an ionizing gap is formed therebetween, and electric circuit means for electrically connecting said two wires in series with said ionizing gap and for connecting the ionizing gap in parallel circuit relationship with said discharge sparkgap, whereby an overvoltage applied to said circuit means causes said ionizing gap to sparkover and preionize said discharge sparkgap to facilitate its sparkover and resultant discharge of the overvoltage.

Claim 3

An overvoltage protective device as defined in claim 1 wherein the length of said ionizing gap is substantially equal to the thickness of the insulating coating on said insulated wire.

Claim 4

An overvoltage protective device as defined in claim 2 wherein the sparkover voltage of said ionizing gap is in the range between 200 and 1,000 volts.

Claim 5

An overvoltage protective device as defined in claim 3 wherein the thickness of said insulating coating is in the range of 1 to 5 mils.

Claim 6

An overvoltage protective device as defined in claim 1 wherein both of said wires have insulating coatings thereon, said coatings each being less than 5 mils in thickness over substantially their entire surface areas.

Claim 7

An overvoltage protective device as defined in claim 5 wherein said mounting means for said main electrodes includes wall members of a sparkgap assembly in which the electrodes are mounted to define a discharge sparkgap, and wherein said means for supporting the preionizer adjacent the discharge sparkgap includes a bead of glue that substantially encases the twisted portion of the twisted wires and is bonded to the insulating housing of said sparkgap assembly.

Claim 8

An overvoltage protective device as defined in claim 6 wherein said glue comprises an epoxy resin.

Claim 9

An overvoltage protective device as defined in claim 5 wherein the uninsulated ends of the pair of twisted wires are exposed only at the terminal ends of the wires, the insulation coatings on said wires being coextensive with the remaining outside diameters of the wires.

Claim 10

A sparkgap assembly as defined in claim 2 wherein said twisted wires are less than 30 mils in diameter and the insulation coating on the outer surface of said insulated wire is less than 3 mils in thickness.

Claim 11

An overvoltage protective device as defined in claim 2 including a resistor electrically connected in shunt relationship with said ionizing gap.

Claim 12

An overvoltage protective device comprising a pair of main electrodes, mounting means for supporting said main electrodes in a predetermined spaced-apart relationship thereby to define a surge voltage discharge sparkgap between the main electrodes, means defining a trigger gap for ionizing said discharge sparkgap, second mounting means for supporting said trigger gap adjacent the discharge sparkgap in operating relationship theReto, a preionizer for ionizing said trigger gap, means for supporting said preionizer in operating relationship adjacent said trigger gap, said preionizer comprising two electrically conductive wires, at least one of said wires having an insulating coating on the outer surface thereof, said wires being twisted together adjacent a first one of the respective ends thereof thereby to hold said first ends of the wires in close proximity to one another, the first ends of said wires that are held in close proximity to one another being uninsulated so that an ionizing gap is formed therebetween, and electric circuit means for electrically connecting said two wires in series with said ionizing gap and for connecting the ionizing gap in parallel circuit relationship with said trigger gap and said discharge sparkgap, whereby an overvoltage applied to said circuit means causes said ionizing gap to radiate photons into the trigger gap to ionize it and lower its sparkover resistance thereby causing it to sparkover and preionize the discharge sparkgap so it sparks over consistently within a relatively narrow range of voltages applied to said circuit means.

Claim 13

An overvoltage protective device comprising a pair of main electrodes, mounting means for supporting said main electrodes in a predetermined spaced-apart relationship thereby to define a surge voltage discharge sparkgap between the main electrodes, means defining a trigger gap for ionizing said discharge sparkgap, second mounting means for supporting said trigger gap adjacent the discharge sparkgap in operating relationship theReto, a preionizer for ionizing said trigger gap, means for supporting said preionizer in operating relationship adjacent said trigger gap, said preionizer comprising two electrically conductive wires, at least one of said wires having an insulating coating on the outer surface thereof, said wires being twisted together adjacent a first one of the respective ends thereof thereby to hold said first ends of the wires in close proximity to one another, the first ends of said wires that are held in close proximity to one another being uninsulated so that an ionizing gap is formed therebetween, and electric circuit means for electrically connecting said two wires in series with said ionizing gap and for connecting the ionizing gap in parallel circuit relationship with said trigger gap and said discharge sparkgap, whereby an overvoltage applied to said circuit means causes said ionizing gap to radiate photons into the trigger gap to ionize it and lower its sparkover resistance thereby causing it to sparkover and preionize the discharge sparkgap so it sparks over consistently within a relatively narrow range of voltages applied to said circuit means.