US3803523A

US3803523A - Transformer bushing

Info

Publication number: US3803523A
Application number: US00338596A
Authority: US
Inventors: D Farmer; C Carlson
Original assignee: Central Moloney Inc
Current assignee: Central Moloney Inc
Priority date: 1973-03-06
Filing date: 1973-03-06
Publication date: 1974-04-09
Anticipated expiration: 1991-04-09

Abstract

A transformer bushing extends through an opening in the transformer housing and is movable between a mounted position releasably engaged with said housing and a displaced position disengaged from said housing and retracted from said opening. A coil lead of substantially dead soft material is releasably connected with the bushing, and said coil lead is concertedly movable with said bushing toward the displaced position remaining substantially in said displaced position for subsequent releasable connection with a replacement bushing.

Description

0 Tinned States Patent 1 1 1111 3.8%,523 Farmer et a1. Apr. 9', T974 1 TRANSFORMER BUSHING 1,041,123 10/1958 Germany 174/152 75] Inventors: Donald J. Farmer; Charles .B.

Carlson, both of Pine Bluff, Ark. Primary Examiner-Thomas l Kozma [73] Assignee: Central Moloney Inc., Pine Bluff, Attorney, Agent, or Firml(oenig, Senniger, Power Ark. and Leavitt [22] Filed: Mar. 6, 1973 [21] Appl. No.: 338,596

[ ABSTRACT [52] Cl gi gj A transformer bushing extends through an opening in [51] i Cl the transformer housing and is movable between a [58] meld of Search 36/90 2 1 mounted position releasably engaged with said hous- 174/152 R ing and a displaced position disengaged from said housing and retracted from said opening. A coil lead [56] References Cited of substantially dead soft material is releasably'con- UNITED STATES PATENTS nected with the bushing, and said coil lead is concert- 3,617,968 11/1971 Wakeam 336/223 edly movable with said bushing toward the displaced 825,882 7/l906 Harper 174/18 position remaining substantially in said displaced posi- 2,676,I98 4/1954 Picard [74/152 R tion for subsequent releasable connection a re- 3,369,166 2/1968 Lake 174/152 R x placement bushing FOREIGN PATENTS OR APPLICATIONS 1,383,979 11/1964 France 174 152 R 13 Claims, 6 Drawing Figures J TENTEBAPR 91974 3803523 mm 1 OF 2 TRANSFORMER BUSHING BACKGROUND OF THE INVENTION This invention relates generally to transformers and in particular to bushings used therewith and also to a method of replacing said bushings.

Transformer bushings provided with terminals for connection to an electrical distribution system have always been susceptible to damage during handling, shipping, installation and maintenance operations. In order to minimize this and to provide an economical and satisfactory secondary or low voltage bushing, molded synthetic resin bushings with a radially extending mounting flange have been widely used for several years. These have been secured by welding to the transformer tank or housing to provide a sealed feedthrough connection interconnecting the external low voltage cables to the transformer core-andcoil unit sealed within the tank. While this arrangement has improved breakage characteristics over typical porcelain low voltage bushings, the breakage and damage problem is still a substantial one. Breakage or damage typically occurs in the field during installation, particularly during installation of transformers on pads and underground in vaults or the like. These damaged bushings cannot be replaced without cutting the welded flange of the damaged bushing from the transformer tank wall. As this cannot be done properly in the field, the entire unit must be returned to the repair shop or manufacturer for removal of the damaged bushing and replacement thereof. Moreover, even if the damaged bushing could be cut off in the field, the interior terminal could not be disconnected from the coil lead and a new bushing connected thereto without access to the interior of the transformer tank for the manual operations required.

SUMMARY OF THE INVENTION Among the several objects of the invention are the provision of a secondary bushing which is secured to the tank wall of the transformer without welding and may be conveniently replaced in the field without having to gain accessto the interior of the transformer housing or tank; the provision of a method for conveniently replacing a damaged transformer'secondary bushing in the field without the need of access to the interior of the tank; and the provision of a transformer which is rugged in construction, economical to produce, and reliable in operation. Other objects and features will be in part apparent and in part pointed out hereinafter.

Briefly, the present invention comprises a transformer having a housing with an opening therein, a bushing releasably engaged with said housing and extending through said opening, and a transformer coil lead of substantially dead soft material releasably connected with said bushing, said coil lead being concertedly movable with said bushing through said opening and being adapted to remain substantially in the displaced position for subsequent connection with a replacement bushing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a portion of a transformer tank shown in section and to which is secured a secondary bushing interconnecting an internal coil lead with an external terminal in accordance with the present inventron;

FIG. 2 is a view similar to FIG. II, but with the bhshing shown disengaged from the tank and in a displaced position for bushing replacement;

FIG. 3 is a plan view of the bushing of FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is an enlarged fragmentary view of the transformer coil lead and connecting means of FIG. l; and

FIG. 6 is an enlarged fragmentary view showing the connecting means of FIG. 6 partially in cross section.

Corresponding reference characters indicate corre sponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings and in particular to FIGS. l and 2, a transformer, indicated generally at l, is provided with an enclosed tank or housing 2 having a wall or side portion 3 in which a terminal or bushingreceiving aperture or opening 4 is provided, and a plurality of threaded mounting studs or bolts 5 are fixedly connected by suitable means, such as welding, to the exterior side or portion of said housing. wall about said opening. Referring now also to FIGS. 3 and 4, a molded or cast low voltage or secondary bushing 6 is provided with a metallic conductor or rod member or stud 7 having threaded exterior and interior end or connecting

portions

8, 9 with the midportion of said stud bonded to a body portion 10 of a suitable synthetic resin material, such as an epoxy resin. A typical secondary terminal 8, shown in phantom is threadedly engaged on the extension end of conductor 7. The body portion 10 of the bushing 6 is provided with a radially extending mounting flange 11 in which mounting holes or apertures 12 are respectively provided for receiving the housing mounting bolts 5.

When the bushing 6 is secured to the housing wall 3, as shown in FIG. I, the mounting bolts 5 are received in the bushing apertures 12, and'a plurality of nuts 13 are threadedly received on said mounting bolts in displacement preventing engagement with the bushing mounting flange llll urging it toward a mounted sealed position in engagement with the housing wall 3. Asuitable resilient gasket or sealing member 14 of buna or the like is sealably engaged between the bushing flange Ill and the housing side wall 3, while a coil lead or strap member H5 is connected between the interior end of conductor 7 and the low voltage winding of a transformer core and coil unit ll6,ll7 disposed within the housing 2 in a manner well known in the art.

The coil lead 15, as also shown in FIGS. 5 and 6, is preferably formed of one or more leads or laminated strips or layers 18 of aluminum of BC. (electrical conductor) grade which has a physical characteristic of being substantially dead soft thereby affording sufficient rigidity to remain substantially in the static position in which it is placed and yet having sufficient flexibility to be movable to another static position. As previously mentioned, one end of the lead is connected to the transformer coil 17, and a block-shaped terminal 19 is fixedly connected by suitable means, such as the weld 20, to the other end of said coil lead. Terminal 19 is provided with a threaded blind bore 21 therein in which the internal end 9 of the bushing 6 is threadedly received, and in order to maintain such threaded engagement between said bushing internal end terminal block bore, a locking member, such as a jam or lock nut 22, is threadedly received on said bushing interior end in locking engagement with the terminal 19. It should be noted that the terminal 19 is predeterminately sized for movement through the opening 4 in the housing side wall 3, as discussed fully hereinafter.

In the event the bushing 6 is damaged, it can easily be disassembled from said transformer and a replacement bushing assembled thereto without returning said transformer to the manufacturer and without disassembling the transformer 2 to gain access to the interior thereof. For instance, if the bushing 6 is damaged, the nuts 13 are manually threadedly disengaged from the housing studs 5, and the bushing 6 isthen manually moved from its mounted position in engagement with the housing wall 3 toward a displaced or retracted position, as shown in FIG. 2, wherein the bushing mounting holes 12 are displaced from said housing studs and at least a portion of the interior end portion 9 of said bushing is retracted or moved outwardly through the housing opening 4. When the bushing 6 is moved toward its displaced position, the coil lead 15 and block terminal 19 are'concertedly movable'therewit h so that at least a portion of said block terminal extends through the housing opening 4. With the bushing 6 and terminal 19 in their displaced positions, as described above, tools or wrenches (now shown) may be manually inserted into driving engagement with the block terminal 19 and lock nut 22 to move said lock nut toward a position disengaged from said block terminal, i.e., out of locking engagement therewith. Thereafter, the bushing 6 is manually rotated to effect the threaded disengagement of the bushing interior end 9 from the block terminal bore 21 and the displacement of said bushing from the coil lead 15. However, while it is preferred to retain a grip on the block terminal 19 manually or with a wrench etc., until the replacement bushing stud is threaded into the jam nut and block terminal, even if the coil lead end is released the coil lead and block terminal will remain substantially in the displaced position thereof for subsequent assembly with a replacement bushing due to the dead soft physical characteristic of the aluminum coil lead 15.

Upon the disassembly of the damaged bushing, as above described, the lock nut 22 is threaded onto the end 9 of a replacement-bushing, and the threaded interior end 9 of the replacement bushing then is manually threaded into engagement with the bore 21 of block terminal 19 in its displaced position and the lock nut 22 is retightened. The replacement bushing, terminal 19, and coil lead 15 are concertedly inwardly moved toward their mounted positions aligning the bushing mounting holes 12 with the housing studs 5 to position the replacement bushing in mounting engagement with the housing wall 3. The nuts 13 are then again threadedly re-engaged with the housing studs 5 in displacement preventing engagement with the mounting flange 11.

The block terminal 19, preferably formed from a relatively hard and high tensile strength aluminum, such as alloy 606], used in conjunction with the aluminum coil lead 15 has certain distinct advantages. Hitherto, particularly if the bushing stud were of bronze or brass, a copper coil lead would have to be used to interconnect the interior bushing stud end 9 to the low voltage coil. Aluminum coil leads, because of cold flow characteristics tend to develop a relatively high resistance connection at the junction where the coil lead end is conventionally secured by a nut and washer to the bushing stud end 9, if the latter is formed of bronze or brass. This could result in a thermal runaway condition and failure of the unit. The use of the block terminal 19 of this harder type aluminum permits the use of the more economical aluminum coil leads without regard to the metal used for the bushing stud and avoids cold flow and possible thermal runaway problems. The electrical resistance of the threaded connection of block terminal 19 and stud end 9 is advantageously low and cold flow is avoided. Moreover, the mass and surface area of the block terminal 19 has advantageous heat flow and dissipation characteristics.

From the foregoing, it is now apparent that a novel transformer 1 and bushing 6 construction and a novel method of assembly thereof meeting the objects and advantageous features set forth hereinabove, as well as others, are disclosed.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A transformer comprising an-assembled housing having an opening therein, a core and coil assembly disposed within said housing, a bushing extending through said opening and movable between a mounted position releasably engaged with said housing and a dipslaced position disengaged from said housing and retracted from said opening, and a coil lead of substantially dead soft conductor material releasably connected with said bushing, said coil lead being concertedly movable with said bushing through said opening toward the displaced position and adapted to remain substantially in said displaced position for subsequent releasable connection with a replacement bushing in the event said firstnamed bushing is damaged.

2. A transformer according to claim 1, wherein said coil lead is aluminum.

3. A transformer according to claim 1, wherein said coil lead includes a plurality of laminated strip members, one end of said strip members being conductively connected with said coil and the other end thereof being releasably connected with said bushing.

4. A transformer according to claim 1, wherein said coil lead includes terminal means releasably connected with said bushing and sized for movement therewith through said opening.

5. A transformer according to claim 1, wherein said coil lead includes a plurality of laminated strip members having one end thereof conductively connected with said coil, and terminal means conductively connected with the other end of said strip members and relasably connected with said bushing, said terminal means being sized for movement through said opening.

6. A transformer according to claim 1, wherein said bushing includes an insulating portion extending substantially coaxially through said opening and releasably connected with said housing, and a conductive stud extending through said insulating portion and having an end portion interiorly of said housing and releasably engaged with said coil lead.

7. A transformer according to claim 6, wherein said insulating portion includes a radially extending mounting flange connected in releasable engagement with said housing exteriorly thereof and about said opening.

8. A transformer according to claim 1, comprising a plurality of mounting studs secured to said housing exteriorly thereof about said opening, said bushing including a mounting flange for engagement with said housing about said opening, a plurality of mounting holes in said mounting flange and received on said studs, and a plurality of nuts threadedlyreceived on said studs and engaged with said mounting flange urging it into engagement with said housing.

9. A transformer according to claim 1, wherein said bushing includes an insulating portion extending through said opening, a mounting flange integral with said insulating portion and extending substantially radially thereof for engagement with said housing about said opening, a plurality of mounting holes in said mounting flange, and a conductive rod member extending through said insulating portion and having opposed end portions interiorly and exteriorly of said housing, respectively, said interior end portion being releasably connected with said coil lead, a plurality of threaded studs engaged with said housing about said opening and received in said mounting holes, and a plurality of nuts threadedly received on said studs and engaged with said mounting flange urging it toward engagement with said housing about said opening.

10. A transformer according to claim 6, wherein said coil lead includes terminal means releasably connected with said interior end portion of said bushing stud, said terminal means being predeterminately sized for movement through said opening.

11. A transformer according to claim 10, wherein said coil lead includes a plurality of interconnected strip members, one end of said strip members being conductively connected with said coil and the other end of said strip members being connected with said terminal means.

12. A transformer according to claim 11, wherein said interior end of said conductive stud si threaded, said coil lead is formed of substantially dead soft aluminum and said terminal means comprises a block of relatively high tensile strength aluminum having a threaded bore therein for threaded engagement with said stud interior end.

13. A transformer comprising an enclosed housing having a wall portion, an opening in said wall portion, a plurality of threaded studs secured to said wall portion about said opening, a bushing including an insulating portion extending substantially through said opening, a flange integral with said insulating portion and extending substantially radially thereof for engagement with said housing about said opening, a plurality of mounting apertures in said flange in which said studs are respectively received, and a conductive rod member extending through said insulating portion and having threaded ends interiorly and exteriorly of said housing, a plurality of nuts respectively threadedly received on said studs and engaged with said flange urging it toward a mounting position in engagement with said wall portion about said opening, said bushing being movable toward a displaced position disengaged from said housing and retracted from said opening upon the removal of said nuts from engagement with said studs and said flange, a core and coil assembly disposed within said housing, a coil lead including a plurality of laminated interconnected strips of a conductive metal having a substantially dead soft physical characteristic and opposite end portions, one of said end portions being conductively connected with said coil, a terminal conductively connected with the other of said end portions, a threaded bore in said terminal threadedly engaged with the interior end of said rod member, and a lock nut threadedly received on said interior end of said rod member in locking engagementwith said terminal, said terminal, and lead being concertedly mov able with said bushing toward the displaced position wherein at least a portion of said terminal protrudes through said opening exteriorly of said housing and remains substantially in the displaced position due to the substantially dead soft physical characteristic of said coil lead for subsequent threaded engagement with a replacement bushing upon the threaded disengagement of said interior end of said rod member from said terminal bore in the event said first-named bushing is damaged.

Claims

1. A transformer comprising an assembled housing having an opening therein, a core and coil assembly disposed within said housing, a bushing extending through said opening and movable between a mounted position releasably engaged with said housing and a displaced position disengaged from said housing and retracted from said opening, and a coil lead of substantially dead soft conductor material releasably connected with said bushing, said coil lead being concertedly movable with said bushing through said opening toward the displaced position and adapted to remain substantially in said displaced position for subsequent releasable connection with a replacement bushing in the event said first-named bushing is damaged.

2. A transformer according to claim 1, wherein said coil lead is aluminum.

5. A transformer according to claim 1, wherein said coil lead includes a plurality of laminated strip members having one end thereof conductively connected with said coil, and terminal means conductively connected with the other end of said strip members and releasably connected with said bushing, said terminal means being sized for movement through said opening.

8. A transformer according to claim 1, comprising a plurality of mounting studs secured to said housing exteriorly thereof about said opening, said bushing including a mounting flange for engagement with said housing about said opening, a plurality of mounting holes in said mounting flange and received on said studs, and a plurality of nuts threadedly received on said studs and engaged with said mounting flange urging it into engagement with said housing.

13. A transformer comprising an enclosed housing having a wall portion, an opening in said wall portion, a plurality of threaded studs secured to said wall portion about said opening, a bushing including an insulating portion extending substantially through said opening, a flange integral with said insulating portion and extending substantially radially thereof for engagement with said housing about said opening, a plurality of mounting apertures in said flange in which said studs are respectively received, and a conductive rod member extending through said insulating portion and having threaded ends interiorly and exteriorly of said housing, a plurality of nuts respectively threadedly received on said studs and engaged with said flange urging it toward a mounting position in engagement with said wall portion about said opening, said bushing being movable toward a displaced position disengaged from said housing and retracted from said opening upon the removal of said nuts from engagement with said studs and said flange, a core and coil assembly disposed within said housing, a coil lead including a plurality of laminated interconnected strips of a conductive metal having a substantially dead soft physical characteristic and opposite end portions, one of said end portions being conductively connected with said coil, a terminal conductively connected with the other of said end portions, a threaded bore in said terminal threadedly engaged with the interior end of said rod member, and a lock nut threadedly received on said interior end of said rod member in locking engagement with said terminal, said terminal and lead being concertedly movable with said bushing toward the displaced position wherein at least a portion of said terminal protrudes through said opening exteriorly of said housing and remains substantially in the displaced position due to the substantially dead soft physical characteristic of said coil lead for subsequent threaded engagement with a replacement bushing upon the threaded disengagement of said interior end of said rod member from said terminal bore in the event said first-named bushing is damaged.