Electrical apparatus including an improved high voltage current limiting protective device

Claim 2

A high voltage current limiting electrical bushing comprising a generally hollow cylindrical, electrically insulating member having an axially extending inner bore, first and second terminal means mounted on said insulating member adjacent to the opposite ends of said electrically insulating member, a fuse link disposed in said inner bore and laterally spaced from said inner bore, said fuse link being electrically connected between said first and second terminal means and including a plurality of axially spaced restricted cross-sectional areas, a pulverulent, arc quenching material substantially filling the space between said fuse link and the inner bore of said electrically insulating member and being disposed in heat transferring relation with both said fuse link and the inner bore of said insulating member to provide a heat flow path from said fuse link to said insulating member through said pulverulent arc quenching material, said electrically insulating member including a predetermined portion along its outer periphery axially spaced from both ends of said electrically insulating member and adapted to receive a metallic supporting means for said bushing, the portion of said electrically insulating member between said first terminal member and said predetermined portion of said electrically insulating member including a plurality of axially spaced, outwardly projecting portions which increase the heat radiating surface of said insulating member which is effective when heat flows from said fuse link to said insulating member through said pulverulent arc quenching material.

Claim 3

The combination as claimed in claim 1, wherein the portion of said electrically insulating member between said first terminal means and said predetermined portion of said electrically insulating member is sufficient to withstand a predetermined potential applied between said first terminal means and the supporting means associated with said bushing.

Claim 4

The combination as claimed in claim 1, wherein an insulating support is disposed in and spaced from said inner bore to extend axially between said terminal means, said fuse link being mounted on said insulating support, and said pulverulent material substantially filling the space between said inner bore and the combination which includes said fuse link and said insulating support.

Claim 5

The combination as claimed in claim 1, wherein a means is disposed adjacent to the terminal means at one end of said bushing for sealing off at least one end of said inner bore and said pulverulent, arc quenching material comprises silica sand.

Claim 6

The combination as claimed in claim 1, wherein said fuse link is composed of silver, and said pulverulent arc quenching material comprises silica sand which forms a fulgurite during an interrupting operation.

Claim 7

A current limiting protective device for an electrical apparatus comprising a hollow, generally cylindrical, electrically insulating bushing having an axially extending inner bore, terminal means disposed adjacent to each end of said bushing, a fuse element disposed in and spaced from said inner bore, said fuse element being electrically connected between said terminal means and including a plurality of axially spaced restricted cross-sectional area, a pulverulent, arc quenching material substantially filling the space between said fuse element and said inner bore and being disposed in heat transferring relation with both said fuse element and the inner bore of said bushing to provide a heat flow path from said fuse element to said bushing through said pulverulent arc quenching material, and means on the outer periphery and axially intermediate the ends of said bushing for mounting said bushing on a supporting barrier at least the portion of said insulating bushing between the last-mentioned mounting means and said terminal means at one end of said bushing including a plurality of axially spaced, outwardly projecting portions which increase the heat radiating surface of said insulating bushing which is effective when heat flows from said fuse element to said bushing through said pulverulent arc quenching material.

Claim 8

A current limiting protective device for an electrical apparatus comprising a hollow, generally cylindrical, electrically insulating bushing having an axially extending inner bore, terminal means disposed adjacent to each end of said bushing, a fuse element disposed in and spaced from said inner bore, said fuse element being electrically connected between said terminal means and including a plurality of axially spaced restricted cross-sectional area, a pulverulent, arc quenching material substantially filling the space between said fuse element and said inner bore and being disposed in heat transferring relation with both said fuse element and the inner bore of said bushing to provide a heat flow path from said fuse element to said bushing through said pulverulent arc quenching material, and means on the outer periphery and axially intermediate the ends of said bushing for mounting said bushing on a supporting barrier at least the portion of said insulating bushing between the last-mentioned mounting means and said terminal means at one end of said bushing including a plurality of axially spaced, outwardly projecting portions which increase the heat radiating surface of said insulating bushing which is effective when heat flows from said fuse element to said bushing through said pulverulent arc quenching material.

Claim 9

The combination as claimed in claim 6, wherein an insulating support is disposed in and spaced from said inner bore to extend axially between said terminal means, said fuse element being mounted on said insulating support.

Claim 10

The combination as claimed in claim 6 wherein a means is disposed adjacent to the terminal means at one end of said bushing for sealing off one end of said inner bore.

Claim 11

The combination as claimed in claim 6, wherein the portion of said electrically insulating member between said first terminal means and said predetermined portion of said electrically insulating member is sufficient to withstand a predetermined potential applied between said first terminal means and the supporting means associated with said bushing.

Claim 12

The combination as claimed in claim 6 wherein said fuse element is composed of silver, and said pulverulent arc quenching comprises silica sand.

Claim 13

An electrical apparatus comprising a metallic housing, means disposed in said housing for normally carrying electric current, a generally hollow cylindrical, electrically insulating bushing having an axially extending inner bore, said bushing being disposed to pass through and to be supported by said housing at a location axially intermediate the ends of said bushing, said bushing including a first portion which projects outside of said housing and a second portion which projects inside said housing, said first portion of said bushing including a plurality of axially spaced, outwardly projecting portions which increase the heat radiating surface of said bushing which is effective when heat flows to said bushing, first and second terminals mounted on said bushing adjacent to the opposite ends of said bushing outside and inside, respectively, of said housing, a fuse element disposed in the inner bore of said bushing and laterally spaced from said inner bore, said fuse element being electrically connected between said first and second terminal means and including a plurality of axially spaced, restricted cross-sectional areas, a pulverulent, arc quenching material substantially filling the space between said fuse element and the inner bore of said bushing and being disposed in heat transferring relation with both said fuse element and the inner bore of said bushing to provide a heat floW path from said fuse element to said bushing through said pulverulent arc quenching material, and electrical leads connected between said second terminal means and said first-mentioned means for carrying electric current to and from said first-mentioned means.

Claim 14

An electrical apparatus comprising a metallic housing, means disposed in said housing for normally carrying electric current, a generally hollow cylindrical, electrically insulating bushing having an axially extending inner bore, said bushing being disposed to pass through and to be supported by said housing at a location axially intermediate the ends of said bushing, said bushing including a first portion which projects outside of said housing and a second portion which projects inside said housing, said first portion of said bushing including a plurality of axially spaced, outwardly projecting portions which increase the heat radiating surface of said bushing which is effective when heat flows to said bushing, first and second terminals mounted on said bushing adjacent to the opposite ends of said bushing outside and inside, respectively, of said housing, a fuse element disposed in the inner bore of said bushing and laterally spaced from said inner bore, said fuse element being electrically connected between said first and second terminal means and including a plurality of axially spaced, restricted cross-sectional areas, a pulverulent, arc quenching material substantially filling the space between said fuse element and the inner bore of said bushing and being disposed in heat transferring relation with both said fuse element and the inner bore of said bushing to provide a heat floW path from said fuse element to said bushing through said pulverulent arc quenching material, and electrical leads connected between said second terminal means and said first-mentioned means for carrying electric current to and from said first-mentioned means.

Claim 15

The combination as claimed in claim 11, wherein said fuse element is composed of silver and said pulverulent arc quenching material comprises silica sand.

Claim 16

The combination as claimed in claim 11, wherein the first-mentioned means comprises an electrical winding.

Claim 17

The combination as claimed in claim 11, wherein said housing is at least partially filled with a dielectric fluid, said bushing including a portion which is immersed in said dielectric fluid adjacent to said second terminal means, and means is disposed adjacent to said second terminal means to substantially seal the inner bore of said bushing to thereby substantially prevent the entrance of said dielectric fluid into said inner bore.