US3916259A

US3916259A - Fuse holder assembly

Info

Publication number: US3916259A
Application number: US459173A
Authority: US
Inventors: William H Russell; Peter Mayer
Original assignee: Kuhlman Corp
Current assignee: Kuhlman Corp
Priority date: 1974-04-08
Filing date: 1974-04-08
Publication date: 1975-10-28
Anticipated expiration: 1992-10-28
Also published as: DE2514887A1; JPS5116423A; CA1035832A

Abstract

A fuse holder assembly which is particularly adapted to be utilized in conjunction with the protection system for the primary side of an oil-filled transformer assembly, wherein the fuse holder is mounted on a plate, the plate being supported on the face of the transformer casing. The fuse holder extends from the plate through an aperture in the transformer housing to support the fusing elements below the level of the cooling liquid within the transformer housing. The fusing elements are a current limiting fuse and a weaklink fuse which are mechanically supported by the fuseholder and which can both be withdrawn from the transformer casing with the fuseholder, to permit inspection and replacement.

Description

United States Patent [191 Russell et al.

[ Oct. 28, 1975 1 FUSE HOLDER ASSEMBLY [75] Inventors: William H. Russell, Forest Park,

Ga.; Peter Mayer, Versailles, Ky.

[52] US. Cl. 317/15; 317/14 H; 337/202;

' 337/257 [51] Int. Cl. H0211 7/04 [58] Field of Search 317/15, 14 R, 14 C, 14 H, 317/40 A; 337/144, 145, 162, 186, 193, 202, 207, 208, 229, 231, 412, 414

3,701,926 10/1972 Risk 317/15 3,721,942 3/1973 Conway 339/75 R 3,798,583 3/1974 Charbonneau et al. 337/202 Primary Examiner-J. D. Miller Assistant ExaminerPatrick R. Salce Attorney, Agent, or Firm-Everett R. Casey [5 7] ABSTRACT A fuse holder assembly which is particularly adapted to be utilized in conjunction with the protection system for the primary side of an oil-filled transformer assembly, wherein the fuse holder is mounted on a plate, the plate being supported on the face of the transformer casing. The fuse holder extends from the plate through an aperture in the transformer housing to support the fusing elements below the level of the cooling liquid within the transformer housing. The fusing elements are a current limiting fuse and a weaklink fuse which are mechanically supported by the fuseholder and which can both be withdrawn from the transformer casing with the fuseholder, to permit inspection and replacement.

7 Claims, 4 Drawing Figures U.S. Patent Oct 28, 1 9 75 Sheet 1 of2 3,916,259

-U.S. Patent Oct. 28, 1975 Sheet 2 of2 FUSE HOLDER ASSEMBLY CROSS REFERENCE This invention is related to those of US. Pat. No. 3,699,490 granted Oct. 17, 1972, and of US. Pat. No. 3,701,926 granted Oct. 31, 1972, and is further related to those in the United States patent application of Ar- BRIEF SUMMARY OF THE INVENTION This invention relates to an improved mechanism for electrically fusing liquid cooled electrical induction equipment such as power and distribution transfomers. The invention is of particular usefulness in protecting pole type, pad mounted and underground oil-filled dis tribution transformers. For protection under a broad range of fault conditions, the combination of an oil immersible current limiting fuse and on oil irnmersible weaklink fuse, of commercially available types, is supported internally of the transformer housing and immersed in liquid coolant within that housing, and in the preferred use, the fuses are serially connected with the primary windings of the transformer. Since the weaklink fuse responds to oil temperature, it reacts to secondary loads and faults, and as a result the oilirnmersed combination can provide secondary fault control, high-energy internal fault control, high current internal fault control, overload control, tank temperature control, and oil temperature control.

The fuse combination is mounted on a fuse holder member which controls its immersed position relative to the other components of the transformer. The fuse holder and fuse combination can be withdrawn through a normally covered access opening in the transformer housing for field inspection and replacement of one or both of the fuses.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a transformer assembly illustrating the use of the fuse holder assembly embodying the principles of the present invention;

FIG. 2 is an elevational view of the fuse holder assembly used in the transformer of FIG. 1;

FIG. 3' is a sectional view taken substantially along the line 3-3 of FIG. 2; with the view being tilted on the sheet; and

FIG. 4 is an end view taken in the direction of the labeled arrow in FIG. 2.

DESCRIPTION The transformer of FIG. 1 includes a housing including a casing closed by a cover 12 bolted or otherwise secured thereon. The transformer, which is conventional, includes internal components including primary and secondary windings (not shown) immersed in a suitable dielectric coolant such as oil 14. The casing 10 is assumed to be approximately square in cross section, having a front wall or plate 16 and side walls 18. A fuse holder assembly 20 is majorly immersed in the coolant 14 and projects into a throat assembly 22 formed on the exterior of the wall 16 of the casing 10. Throat assembly 22 comprises a weldment welded or otherwise secured to the front plate 16 to form a liquid-tight throat or cavity surrounding an opening 24 (FIG. 2) in the wall 16. Throat assembly 22 is itself open on its outer face, as at 26, with that opening being selectively closable by a gasketed cover plate 28 which may be secured to the throat assembly 22 by means such as a stud and nut assembly 30. If the dielectric liquid level is above that of the bottom portion of the opening 24, it should be lower than the opening 26.

A fuse holder tube or support and guide member 32 is disposed within the casing 10 and projects through opening 24 to a position proximate opening 26. Tube 32 which is of insulative material such as glass fiber reinforced epoxy. It can be formed of other insulative materials and may be molded, extruded or otherwise formed. In the illustrated arrangement, tube 32 is generally square in cross section, tubular, and open at both ends. In one face, tube 32 is provided with an elongated slotted opening 34 extending from its outermost end to a point 33 essentially midway of its length for a purpose to be noted.

Tube 32 is rigidly supported with respect to the transformer casing. In the illustrated embodiment of the invention, this is accomplished by providing both forward and aft supports. The forward support includes a screw 36 (FIG. 3) threaded through the wall of tube 32 into a support lug 38 which is welded or otherwise secured to the front plate 16, to the throat assembly 22, or to both. The aft support comprises a support bracket 40, which may be of glass fiber reinforced epoxy or otherwise, and which is bolted or otherwise secured both to the side wall 18 and to the fuse holder tube 32. Tube 32 constitutes a support and guide member to support the withdrawable elements essentially over the entirety of their path of withdrawal and insertion movements as well as in their fully inserted positions.

A fuse holder or fuse attachment device is removably disposed within the tube 32. Fuse holder 42, which may be molded or otherwise formed of plastic or other dielectric material, includes a neck portion 44 the end of which threadedly accepts a pull-out eye 46. At its lower (rightward) end, neck 44 terminates in a flanged shoulder portion 48. The body portion 50 of the fuse holder extends rightwardly from the shoulder 48 and is hollow from the shoulder 48 rearwardly, to accept a current limiting fuse 52. At its innermost or forward end, the cavity 51 within body 50 is provided with integral position defining stops 54 (FIG. 3) for locating the end of fuse 52 at its point of maximum insertion.

A metallic end bracket 56, of folded T-shape, has a cross-arm portion which is secured to the fuse holder 42 such as by screws 58 (FIG. 2) which threadedly engage body portion 50. The apertures in end bracket 56, which are engaged by screws 58 are preferably elongated to permit adjustment during assembly.

End bracket 56 is further provided with a depending leg portion to which a nut 60 (FIG. 3) is welded or otherwise secured. Nut 60 threadedly accepts the threaded stud 62 which is formed on commercially available forms of current limiting fuses 52. When a fuse 52 is replaced, the new fuse is simply inserted into the cavity within body 50 of the fuse holder 42 (from the right) until stud 62 engages nut 60, and is then rotated, by hand, to thread stud 62 into nut 60, the right-hand end of the current limiting fuse 52 projecting from the fuse holder 42 to facilitate that assembly.

The lower or right-hand end of the current limiting fuse 52 is provided with the customary terminal stud 64 upon which is threaded a metallic male contact 66. Contact 66 engages a tulip contact finger assembly 68, the projecting fingers of which are-compelled into a good electrical engagement with contact 66 by means of a garter-spring 70.

Spring assembly 68 is secured to an end bracket 72 by means of a machine screw 74 which also serves as the line side connector. End bracket 72 (FIGS. 2 and 3) is provided with projecting side arms 76 which embrace and areriveted or otherwise secured to the tube disengaged from the contact assembly 68, and the entire assembly translated out of the housing. It will be observed that the slot 34 in the tube 32 permits the weaklink fuse 80, with its brackets 82 and 84 and with its male contact element 92, to be freely moved out of the tube and through the openings 24 and 26 (FIG. 2).

32. It will be observed that the end bracket 72 does not fully close the lower .end of tube 32 or impede the effective flow of coolant thereinto.

A leaf spring assembly, comprising a plurality of leaf springs 78, is secured to the lower end of tube 32 in a position to engage and guide the lower or leading end of the current limiting fuse 52.

A weaklink fuse 80 is provided with integral angled support brackets 82 and 84. Support bracket 82 is screwed or otherwise detachably connected to end bracket 56 and that end of weaklink fuse 80 is electrically connected to bracket 56, and hence to stud 62, and hence. to one end of the current limiting fuse 52.

weaklink fuse support bracket 84 (FIG. 2) is screwed or otherwise detachably connected to a plate 86 which is in turn screwed or otherwise attached to the body portion 50 of the fuse holder 42. Plate 86 is provided with an upstanding leg 88 (FIG. 3) to constitute a contact. Leg 88 is apertured to accept a screw 90 threadedly engaging a male contact member 92. Male contact member 92 engages a tulip spring contact assembly 94 similar to that previously described, and that contact assembly is in turn fastened to a support bracket 96 by means of a screw and nut assembly 98 which also serves as the load side connection. Bracket 96 is riveted or otherwise secured to the fuse holder tube 32.

As a result of the noted connections, power connected to the line side connection 74 by means of a suitable conductor is conducted through current limiting fuse 52, stud 62, bracket 56, weaklink fuse 80, bracket 84, bracket88, male contact 92, contact assembly 94, load side connecting stud 98 and, through a suitable conductor, to the primary winding of the transformer.

Current limiting fuse 52 and weaklink fuse 80 may be of any suitable, appropriately rated, commercially available types such as those manufactured by Kearney-National, Inc. In general, current limiting fuses tended-duration low-current fault conditions, to the possible point of blowing up. The weaklink fuses, on the other hand, are less satisfactory on high fault currents, perform well under low-current fault conditions. Accordingly, a coordinated series combination of the two can provide highly improved full-range fault protection. In the present utilization, the weaklink fuse senses, ormay sense, oil temperature.

To inspect or replace either of the fuses, the cover plate 28 is removed by unscrewing nuts 30. The pullout eye may then be engaged with a hotstick (shotgun stick or hookstick) and a force exerted to translate the fuse assembly outwardly along its longitudinal axis. The male contact 92 will thereupon be disengaged from the contact assembly 94 and the male contact 66 will be The current limiting fuse may be replaced, if necessary, in the manner above noted, with the addition of transferring'the male contact 66 to the replacement fuse. The weaklink fuse may be replaced, if necessary, by unscrewing its brackets 82 and 84 and replacing it with a replacement fuse.

Tile fuse assembly including the fuse holder 42 with the fuses in place, is then reinserted through the opening 26 into the fuse holder tube 32 and shoved downwardly into the illustrated seated position, the engagement between the portion 50 of the fuse holder (FIG. 4) and the inner wall of the tube 32 insuring proper orientation of the parts. In view of the magnitude of the currents which are carried, forcible engagement should be made between the male contacts 92 and 66 and their respective contact assemblies 94 and 68. However, if the requisite seating is not achieved during such reinsertion, provision is made, in the preferred arrangement, for insuring an adequate degree of seating. This is accomplished by establishing the dimensions such that upon the replacement of cover plate 28, and the tightening of nuts 30, the engagement between that cover plate and an improperly extending pull out eye 46 will exert a force on the assembly to drive the male contacts 92 and 96 into proper electrical engagement with their respective contact assemblies.

What is claimed is:

1. In a transformer assembly having a housing having a line terminal, a winding assembly supported in the housing and having a primary winding terminal, and a cooling liquid within the housing for cooling the winding, the combination of means defining-a separate fuse assembly accepting opening in said housing above the level of the cooling liquid spaced from "the line terminal, means removably attachable to said housing for closing said opening, a fuse holder member, first securing means on said fuse holder for detachably securing thereon a current limiting fuse, second i securing means for removably supporting a separate weaklink fuse on the combination of said fuse holder. member and the current limiting fuse, said first and second. securing means permitting separate replacement of the current limiting fuse and of the weaklink. fuse, support and guide means rigidly supported in said housing in a fixed position and adjacent said opening, said fuse holder member and said support and guide means supporting the current limiting and the weaklink fuses below the level of and immersed in the cooling liquid, means for detachably electrically interconnecting the current limiting and the weaklink fuses, means for permitting the withdrawal of said fuse holder member including the current limiting and weaklink fuses from the housing through the opening therein, and means including said support and guide means for guiding said fuse holder member including the separate current limiting and weaklink fuses during the withdrawal, reinsertion and use thereof, saidrneans for permitting the withdrawal of said fuse holder member comprising an eye on said fuse holder engageable by a hotstick only after said means for closing said opening has been removed.

means for automatically effecting detachment when said fuse holder member is withdrawn from said support .and guide means.

3. The combination of claim 2 further including means for insuring re-engagement of said quick detachable connector means upon the replacing of said fuse holder member in said support and guide means.

4. The combination of claim 3 in which said means for insuring re-engagement includes said eye and said means for closing said opening.

5. In a transformer assembly having a housing having a line terminal, a winding assembly supported in the housing and having a primary winding terminal, and a cooling liquid within the housing for cooling the winding, the combination of means defining a separate fuse assembly accepting opening in said housing above the level of the cooling liquid spaced from the line terminal, means removably attachable to said housing for closing said opening, a fuse holder member, first securing means on said fuse holder for detachably securing thereon a currect limiting fuse, second securing means for removably supporting a separate weaklink fuse on the combination of said fuse holder member and the current limiting fuse, said first and second securing means permitting separate replacement of the current limiting fuse and of the weaklink fuse, support and guide means rigidly supported in said housing in a fixed position, said fuse holder member and said support and guide means supporting the current limiting and the weaklink fuses below the level of and immersed in the cooling liquid, means for detachably electrically interconnecting the current limiting and the weaklink fuses, means for permitting the withdrawal of said fuse holder member including the separate current limiting and weaklink fuses from the housing through the opening therein, and means including said support and guide means-for guiding said fuse holder member including the current limiting and weaklink fuses during the withdrawal, reinsertion and use thereof, said support and guide means comprising a rigid tubular insulative member supported by the housing, and said fuse holder being insertable in said tubular member.

6. The combination of claim 5 in which said fuse holder has a tubular portion for sheathing a portion of the current limiting fuse and contact means within said tubular portion for removably securing one of the fuses within said tubular portion.

7. In a transformer assembly having a housing having a line terminal, a winding assembly supported in the housing and having a primary winding terminal, and a cooling liquid within the housing for cooling the winding, the combination of means defining a separate fuse assembly accepting opening in said housing above the level of the cooling liquid spaced from the line terminal, means removably attachable to said housing for closing said opening, a current limiting fuse, a fuse holder member, first securing means on said fuse holder for detachably securing thereon said current limiting fuse, a weaklink fuse, second securing means for removably supporting said separate weaklink fuse on the combination of said fuse holder member and said current limiting fuse, said first and second securing means permitting separate replacement of said current limiting fuse and of said weaklink fuse, support and guide means rigidly supported in said housing in a fixed position, said fuse holder member and said support and guide means supporting said current limiting and said weaklink fuses below the level of and immersed in the cooling liquid, means for detachably electrically interconnecting said current limiting and said weaklink fuses, means for permitting the withdrawal of said fuse holder member including said separate current limiting and weaklink fuses from the housing through the opening therein, and means including said support and guide means for guiding said fuse holder member including said current limiting and weaklink fuses during the withdrawal, reinsertion and use thereof, said support and guide means comprising a rigid tubular insulative member supported by the housing, and said fuse holder being insertable in said tubular member.

Claims

1. In a transformer assembly having a housing having a line terminal, a winding assembly supported in the housing and having a primary winding terminal, and a cooling liquid within the housing for cooling the winding, the combination of means defining a separate fuse assembly accepting opening in said housing above the level of the cooling liquid spaced from the line terminal, means removably attachable to said housing for closing said opening, a fuse holder member, first securing means on said fuse holder for detachably securing thereon a current limiting fuse, second securing means for removably supporting a separate weaklink fuse on the combination of said fuse holder member and the current limiting fuse, said first and second securing means permitting separate replacement of the current limiting fuse and of the weaklink fuse, support and guide means rigidly supported in said housing in a fixed position and adjacent said opening, said fuse holder member and said support and guide means supporting the current limiting and the weaklink fuses below the level of and immersed in the cooling liquid, means for detachably electrically interconnecting the current limiting and the weaklink fuses, means for permitting the withdrawal of said fuse holder member including the current limiting and weaklink fuses from the housing through the opening therein, and means including said support and guide means for guiding said fuse holder member including the separate current limiting and weaklink fuses during the withdrawal, reinsertion and use thereof, said means for permitting the withdrawal of said fuse holder member comprising an eye on said fuse holder engageable by a hotstick only after said means for closing said opening has been removed.

2. The combination of claim 1 further including connector means for connecting the current limiting fuse to one of the transformer terminals, and connector means for connecting the weaklink fuse to the other one of the transformer terminals, and in which both of said connector means are quick detachable connector means for automatically effecting detachment when said fuse holder member is withdrawn from said support and guide means.

5. In a transformer assembly having a housing having a line terMinal, a winding assembly supported in the housing and having a primary winding terminal, and a cooling liquid within the housing for cooling the winding, the combination of means defining a separate fuse assembly accepting opening in said housing above the level of the cooling liquid spaced from the line terminal, means removably attachable to said housing for closing said opening, a fuse holder member, first securing means on said fuse holder for detachably securing thereon a currect limiting fuse, second securing means for removably supporting a separate weaklink fuse on the combination of said fuse holder member and the current limiting fuse, said first and second securing means permitting separate replacement of the current limiting fuse and of the weaklink fuse, support and guide means rigidly supported in said housing in a fixed position, said fuse holder member and said support and guide means supporting the current limiting and the weaklink fuses below the level of and immersed in the cooling liquid, means for detachably electrically interconnecting the current limiting and the weaklink fuses, means for permitting the withdrawal of said fuse holder member including the separate current limiting and weaklink fuses from the housing through the opening therein, and means including said support and guide means for guiding said fuse holder member including the current limiting and weaklink fuses during the withdrawal, reinsertion and use thereof, said support and guide means comprising a rigid tubular insulative member supported by the housing, and said fuse holder being insertable in said tubular member.