US3742122A

US3742122A - Electrical connector

Info

Publication number: US3742122A
Application number: US00188301A
Authority: US
Inventors: N Blavos; K Lin; L Dobson
Original assignee: Westinghouse Electric Corp
Current assignee: ABB Inc USA
Priority date: 1971-10-12
Filing date: 1971-10-12
Publication date: 1973-06-26
Anticipated expiration: 1990-06-26

Abstract

Fixture means for connecting conductor straps to each other or to a bus bar. Partitions of the fixture means form channels into which the conductor straps are placed, with the ends of the straps being flush with the front faces of the partitions. A conducting material is welded across the partition faces and the conductor strap ends to provide a current path from the conductor straps to the partitions. The fixture means is welded to the bus bar to provide a low resistance current path between the bus bar and the fixture means.

Description

United States Patent Blavos et al.

[4 1 June 26, 1973 ELECTRICAL CONNECTOR Inventors: Nicholas G. BIIVOS; Kou Chi Lin,

both of Sharon; LeRoy E. Dobson, Jamestown, all of Pa.

Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: Oct. 12, 1971 Appl. No.: 188,301

US. Cl. 174/94 R, 29/628, 174/88 R, 336/192, 339/275 R Int. Cl H02g 15/08 Field of Search 174/94 R, 84 R; 339/275 R; 336/192; 29/628 References Cited UNlTED STATES PATENTS Maclnnes 174/94 R 3,020,333 2/1962 Bangert et a1 174/84 R X Primary Examiner-Darrell L. Clay A ttorney A. T. Stratton and F. E. Browder [57] ABSTRACT Fixture means for connecting conductor straps to each other or to a bus bar. Partitions of the fixture means form channels into which the conductor straps are placed, with the ends of the straps being flush with the front faces of the partitions. A conducting material is welded across the partition faces and the conductor strap ends to provide a current path from the conductor straps to the partitions. The fixture means is welded to the bus bar to provide a low resistance current path between the bus bar and the fixture means.

8 Claims, 5 Drawing Figures ELECTRICAL CONNECTOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates, in general, to electrical connectors and, more specifically, to conductor strap connectors for power transformers.

2. Description of the Prior Art It is standard practice in high current transformers to connect the straps of the coil conductor to a bus bar. The connection must provide sufficient mechanical strength while providing adequate electrical performance. To avoid a high resistance region in the current path, the cross-sectional area of the connection must be at least equal to the cross-sectional area of the coil conductor.

Connections made in high current transformers having copper conductors and bus bars are usually made by brazing the conductors to the bus bar. This method forms an excellent connection because the brazing material flows between the conductor straps as well as between the bottom straps and the bus bar. The connection is completely solid. This method does not involve special temperature control requirements since the melting point of copper is substantially above the melting point of the brazing material.

Connections made in high current transformers having aluminum conductors and bus bars are substantially more complicated to make than connections in copper transformers. Brazing aluminum requires precise temperature control since the melting point of aluminum is only 100 to l50F above the melting point of the brazing material. The allowable tolerance of the temperature is too low to permit satisfactory results in a production shop.

Brazing aluminum also requires the use of flux materials. Unfortunately, suitable fluxes are corrosive to the aluminum. Thus, any residual flux remaining on the conductors will cause corrosion of the connection and degrade its electrical performance.

It has been found that arc welding by either the MIG (Metallic Inert Gas) or TIG (Tungsten Inert Gas) method provides a satisfactory electrical and mechanical connection for the aluminum members. When the number of conductor straps and the size of the conductor are sufficiently small, arc welding may be used. However, when the size of the conductor increases due to the number and/or size increase of the straps, the arc welding method of connecting the straps to the bus bar becomes impractical. As a general rule, the weld material should have a current carrying cross-section area equal to or greater than the cross-section area of the conductor. To achieve this, it is necessary to buildup the weld material by making continued passes with the welding electrode.

Therefore, it is desirable, and it is an object of this invention, to provide an apparatus for making connections between the straps of a multiple strap conductor and a bus bar which does not necessitate excessive weld build-up to provide satisfactory electrical performance.

SUMMARY OF THE INVENTION There is disclosed a new and useful arrangement for connecting conductor straps. A fixture having at least two partitions positioned to form at least one channel is constructed of a suitable material, such as aluminum. The straps of the conductor are positioned in the channel with the ends of the straps located adjacent to and flush with the faces of the partitions. Suitable conducting material is disposed over the partition faces and the strap ends. The conducting material may be deposited by an arc welding process. The thickness of the layer of conducting material is not required to equal the cross-sectional area of the conductor since the strap current is transferred to the bus bar by the partitions. The fixture may include a base plate or the partitions may be attached directly to the bus bar. This invention may also be used to connect together conductors having multiple straps.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawings, in which:

FIG. 1 is a view of a prior art arrangement for connecting a plurality of conductor straps to a bus bar;

FIG. 2 is a view of a fixture arrangement for connecting a plurality of conductor straps to a bus bar according to one embodiment of this invention;

FIG. 3 is a view of a fixture arrangement for connecting a plurality of conductor straps to a bus bar according to another embodiment of this invention;

FIG. 4 is a front elevational view of the apparatus shown in FIG. 3 with the conducting material shown in phantom; and

FIg. 5 is a front elevational view of another embodiment of thisinvention.

Throughout the following description, similar reference characters refer to similar members in all figures of the drawings.

Referring now to the drawings, and FIG. 1 in particular, there is shown a connection illustrating a prior art arrangement. The conductor 10 is connected to the bus bar 12 by the conducting material 14. The conductor 10 comprises a plurality of straps l6 constructed of a low resistance metal, such as aluminum. The conducting material 14 is an aluminum alloy which has reasonably low resistance. In order to prevent decreasing the cross-sectional area of the current path, the conducting material 14 is deposited generally in the form of a are having a radius R and a width equal to the width W of the conductor. Arc welding may be used to deposit the conducting material 14 in the proper shape.

The prior art arrangement illustrated in FIG. 1 provides satisfactory mechanical and electrical performance, however, the amount of labor involved in constructing the connection is excessive. Sine the size of the weld bead is limited, numerous passes by the welder are necessary to build-up the weld material to the proper dimensions.

Currents flowing through the conductor straps 16 travel through the conducting material 14 to the bus bar 12. Application of a single layer of conducting material to the ends of the straps 16, with the lower edge of the layer welded to the bus bar 12, would not provide the desired mechanical and electrical performance. Currents flowing in the portion of the conducting material nearest the bus bar would be nearly equal to the sum of the currents in all of the straps 16 of the conductor 10. Thus, the cross-sectional area of the current path would be substantially less than the desired area and excessive heat would be developed.

As a practical matter, only a small portion of the total current flows between straps before it reaches the weld material 14. Oxidation on the surface of the straps significantly increases the strap-to-strap resistance, thus most of the current flows through the conducting material 14 and not across the junction 18 formed by the lower straps and the bus bar 12.

An embodiment of this invention is illustrated in FIG. 2. A fixture 20 is attached to the bus bar 12 by the conducting material 21 and by conducting material at other locations not illustrated in FIG. 2. The quantity of conducting material which attaches the fixture 20 to the bus bar 12 is usually sufficient if the perimeter of the bottom portion of the fixture 20 is welded to the bus bar 12. In this embodiment, the bus bar 12, the fixture 20, and the conductor straps 16 are all constructed of aluminum. The fixture includes the

partitions

22 and 24 which form the channel 26 into which the straps 16 of the conductor 28 are positioned. The straps 16 extend through the channel 26 with their ends substantially flush with the front faces 30 and 32 of the parti-.

tions

22 and 24, respectively. A conducting layer 34 electrically connects the ends of the straps to the partition faces 30 and 32. As will be discussed hereinafter, a single layer 34 of conducting material provides adequate electrical and mechanical performance. Although the conducting material 34 may be an-alloy of aluminum deposited by an arc welding process, other conducting materials and methods of deposition may be used.

The fixture 20 may be manufactured by extruding, casting, machining, welding, or any other suitable method. As will be illustrated later, the bottom plate 36 may be omitted. The partition faces 30 and 32 extend beyond the edge 38 of the bus bar 12. Although this is not necessary for proper performance of the connector, it permits convenient disassembly of the connection should that be desired. To disconnect the conductor straps 16, the fixture and strap assembly may be cut along a plane positioned parallel to the edge 38 and located between the edge 38 and the partition faces 30 and 32. Effectively, this removes all of the material 34 from the connection and the conductor straps 16 may be easily removed. The same fixture can, be used again by inserting the conductor straps l6'with their ends in flush alignment with the new partition faces produced by the cutting step. New conducting material, similar to the material 34, would be appliedto the new partition faces and the ends of the conductor straps 16.

The fixture in FIG. 2 provides an arrangement for connecting the straps of a conductor together or, when the fixture is attached to a bus bar, an arrangement for connecting the straps to the bus bar. The arrangement requires less conducting material and welding labor than required by the prior art arrangement; The multiple channel fixture, illustrated in FIG. 3, may be used when the conductor width is beyond the capacity of the single channel fixture.

In FIG. 3, the fixture 40 includes the

partitions

42, 44 and 46 which form the channels 48 and 5.0. The conductor 52 comprises the

strap groups

54 and 56 which are positioned in the

channels

48 and 50, respectively, with the ends of the straps located in flush relationship with the front faces 58, 60 and 62 of the

partitions

42, 44 and 46, respectively. The conducting material 64 is disposed on the fixture 40 and the straps l6 similarly to the conducting material 34 shown in FIG. 2.

By using the middle partition 44, the current density of the weld or conducting material 64 is not as high as would be if the partition was absent. This makes it feasible to apply a single layer of conducting material 64 to the fixture l4 and the straps 16 to achieve satisfac tory connector performance.

FIG. 4 is a front elevational view of the fixture 40 with the conducting material 64 shown in phantom. Lines, such as 68, illustrate generally the paths of the current flowing between the straps of the

strap groups

54 and 60 and the bus bar 12. For instance, current flowing through the strap 16 follows a path through the weld material 64 into the partition 44, through the weld 70, and into the bus bar 12. As a result of this arrangement, the

partitions

42, 44 and 46 carry a substantial amount of the current, thus the current density in the conducting material 64 is satisfactory even when relatively thin. Although the thickness of the layer of conducting material 64 may be otherwise, a suitable thickness is one which equals the width w of a strap conductor.

In FIGS. 3 and 4, the

partitions

42, 44 and 46 connect to the base plate 72. Although shown as one integral piece, the fixture 40 may comprise partitions which are attached to'the base plate 72 by welding or any other suitable means. Connectors having a different number of partitions, channels, total conductor straps, and/or conductor straps per strap group, as well as other variations of this embodiment, are all within the contemplation of this invention.

Rather than attaching partitions to a base plate, it may be desirable to connect partitions directly to the bus bar. FIG. 5 illustrates such an arrangement, with the conducting material 74 shown in phantom. The partitions 76, 78 and 80 in this embodiment are welded to the bus bar 12. The current paths from theconductor straps 16 to the bus bar 12 aresimilar to the paths 68 illustrated in FIG. 4, with the exception that the paths do not extend through a base plate. If the partitions 76, 78 and 80 have their

faces

82, 84 and 86, re-

spectively, projected beyond the bus bar 12, the conducting material 74 may not extend below the top of the'bus bar 12 as illustrated. In such case, it may be desirable to deposit some of the conducting material 74 adjacent to the junction of the bottom layer of conductor straps l6 and the bus bar 12.

There has been disclosed a novel arrangement for making an electrical connection. Since numerous changes may be made in the above described apparatus and different embodiments of this invention may be made without departing-from the spirit thereof, it is intended that all of thematter contained in the foregoing description, orshown in the accompanying drawings, shall be interpreted as illustrative rather than limiting.

We claim as our invention: y

l. A fixture connecting together a plurality of conductor straps, said fixture comprisingpartitions having front and side faces,'adjacent partitions positioned with their adjacent side faces substantially parallel to define a channel betweensaid partitions, said channel containing the conductor straps with the ends of the conductor straps being substantially flush with the front faces of said partitions, means connecting said partitions to a bus bar, and conducting material disposed across the front faces of said partitions and the ends of the'eonductor straps.

2. The fixture of claim 1 wherein the partitions are connected to a base plate.

3. The fixture of claim 2 wherein the base plate is connected to a bus bar with the front faces of the partitions extending beyond an edge of the bus bar.

4. The fixture of claim 1 wherein the partitions are connected directly to a bus bar.

5. The fixture of claim 1 wherein the fixture comprises a plurality of channels with conductor straps disposed in each channel.

6. The fixture of claim 1 wherein the partitions are constructed of aluminum.

7. A fixture connecting a plurality of aluminum conductor straps to an aluminum bus bar, said fixture comprising at least two partitions each having front and side faces, means connecting said partitions to said bus bar,

of one of the conductor straps.

Claims

1. A fixture connecting together a plurality of conductor straps, said fixture comprising partitions having front and side faces, adjacent partitions positioned with their adjacent side faces substantially parallel to define a channel between said partitions, said channel containing the conductor straps with the ends of the conductor straps being substantially flush with the front faces of said partitions, means connecting said partitions to a bus bar, and conducting material disposed across the front faces of said partitions and the ends of the conductor straps.

2. The fixture of claim 1 wherein the partitions are connected to a base plate.

6. The fixture of claim 1 wherein the partitions are constructed of aluminum.

7. A fixture connecting a plurality of aluminum conductor straps to an aluminum bus bar, said fixture comprising at least two partitions each having front and side faces, means connecting said partitions to said bus bar, the front faces of said partitions extending beyond an edge of the bus bar, adjacent partitions positioned with their adjacent side faces substantially parallel to define a channel between said partitions, said channel containing the conductor straps with the ends of the conductor straps being substantially flush with the front faces of said partitions, and conducting material disposed by arc welding across the front faces of said partitions and the ends of the conductor straps.

8. The fixture of claim 7 wherein the conducting material has a thickness approximately equal to the width of one of the conductor sTraps.