US2735043A - speck - Google Patents

Description

Feb. 14, 1956 w, s c 2,735,043

PANELBOARDS I Filed June 24, 1952 2 Sheets-Sheet l WITNESSES: 2 INVENTOR Wi||isA.Speck.

United States Patent PANELBOARDS Willis A. Speck, Union, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, 1 21., a corporation of Pennsylvania Application June 24, 1952, Serial No. 295,290

14 Claims. (Cl. 317-119) My invention relates, generally, to panelboards and, more particularly, to circuit breaker panelboards of the distribution or power type where the branch circuits carry heavy currents several times greater than in lighting circuit panelboards, and employs novel formed connectors for connecting the branch circuit controlling devices to the main bus bars in the panelboard.

Heretofore it has been common practice to make the branch circuit copper connectors of such a size that the current density in a connector would not exceed 1000 amperes per square inch of cross-sectionalarea of the connectors. It has also been the practice not to exceed 200 amperes per square inch of contact area between the bus bar and the connector. These requirements have caused the use of cast copper connectors because of the different dimensions required for the different parts of the connectors.

In order to conserve copper, it is desirable to reduce the size of the connectors for a certain current rating, and to reduce the cost of manufacture of the connectors. However, the specified temperature rise for the connectors and other parts of the panelboard must not be exceeded.

Accordingly, an object of my invention is to provide a panelboard construction permitting an increase in the current carrying capacity of the connectors without materially increasing the temperature rise of the device.

It is also an object of my invention to eliminate the need for the casting of panelboard connectors, and to obtain improved results from connectors which can be formed cheaply from straight strips of rolled copper bars or straps of uniform cross section.

Another object of my invention is to provide for rigidly attaching a connector to a main bus bar in a panelboard in such a manner as to give increased heat and current llow, and to positively prohibit rotation of the connector.

A further object of my invention is to provide in a panelboard construction for the installation of additional circuit controlling devices in blank spaces in the panelboard, after it is placed in service, without the installation of connectors in addition to those originally installed.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of my invention, an auxiliary or supplemental connector having an angular or U-shaped portion engaging the branch circuit connector and a straight portion engaging the bus bar is provided for each branch circuit connector, thereby increasing the effective contact area between the branch circuit connector and the bus bar. This decreases the electrical resistance of the connection and increases the capacity to conduct current and to transmit heat from the branch circuit connector to the bus bar, which, in turn, increases the capacity of the branch circuit connector to carry current with a given temperature rise. The supplemental connector also prevents turning of the branch circuit connector about the single screw which attaches the connector to the bus bar, and avoids the possibility of a short circuit across the main buses where the other end of the connector is not supported.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a view, in plan, of part of a panelboard structure embodying the principal features of the invention, portions being broken away for clearness;

Fig. 2 is a view, in section, taken along the line IIII in Fig. 1;

Fig. 3 is an enlarged view, in plan, of a connector utilized for connecting circuit breakers to one of the outer bus bars;

Fig. 4 is an enlarged view, in elevation, of the connector shown in Fig. 3;

Fig. 5 is an enlarged view, in elevation, of a connector utilized for connecting circuit breakers to the center bus bar;

Fig. 6 is an enlarged view, in plan, of a supplemental connector utilized in conjunction with the connector shown in Fig. 3;

Fig. 7 is an enlarged view, in side elevation, of the supplemental connector;

Fig. 8 is an enlarged detail view showing the manner of connecting a circuit breaker to a bus bar by means of a center connector;

Fig. 9 is an enlarged detail view showing the manner of connecting a circuit breaker to a bus bar by means of an outer connector; and

Fig. 10 is an isometric view showing a center connector and its supplemental connector connected to a bar with a prior cast connector also connected to the bar.

Referring to the drawings, and particularly to Fig. 2, the panelboard structure shown therein comprises a sheet metal cabinet or box 6 having a cover 7 provided with a hinged door 8 and a return or trim 9. A mounting plate or pan It carries a plurality of main bus bars 11 for the phases A, B and C, and a plurality of circuit controlling devices 12 which are preferably automatic circuit breakers of a type having a circuit breaker mechanism enclosed in a housing 13 with an operating handle 14 for actuating the circuit breaker mechanism. The circuit breaker housings 13 are disposed side-by-side in two parallel rows, the number of breaker units depending upon the number of circuits to be controlled.

As shown most clearly in Fig. 2, the outer ends of the circuit breaker housings are attached to 2 bars 15 by means of mounting brackets 16 which may be attached to the Z bars 15 by screws 17. Each breaker housing may be attached to a mounting bracket 16 by means of a screw 18. The mounting plate 10 may be adjustably mounted in the cabinet 6 (by means not shown).

As shown, the circuit breaker units 12 may be of either the single pole, two-pole, or three-pole type. If desired, space may be left available in the structure for the installation of additional circuit breaker units after the panelboard has been originally assembled. Filler plates 19 may be provided in the spaces for the additional circuit breaker units. The filler plates are supported by brackets 21 which are attached to the 2 bars 15 by the mounting brackets 16. Cover plates 22 are provided at the center of the panelboard structure. The plates 22 are attached to the breaker housings 13 or the filler plates 19 by screws 23. The bus bars 11 may be mounted upon insulating blocks 24 which rest upon the mounting plate 10.

The circuit breaker units are provided with load terminals 25 which may be connected to the branch load circuits by power conductors (not shown). The breaker units are provided with line terminals 26 which may be connected to one of the outer bus bars 11 by means of connectors 27 or to the center bus bar by means of connectors 28.

As shown most clearly in Figs. 3 and 4, each outer connector 27 is generally of a Z shape having an arm 29 with an opening 31 therein for attaching the connector to one of the bus bars 11 and an arm 32 with two threaded openings 33 therein for attaching two oppositely disposed circuit breaker terminals 26 thereto. As shown in Figs. 1 and 2, each terminal 26 may be attached to a connector 27 by a screw 34.

As shown most clearly in Fig. 5, each center connector 28 is bent from rolled straps of uniform cross-section to be generally of a U-shape, having outwardly extending arms 35 with openings 36 therein for receiving the screws 34 for connecting oppositely disposed breaker terminals to the connector. The base or bight of the U has an opening 37 therein through which a screw 38 may be inserted for attaching the connector to the center bus bar 11, as shown in Figs. 1 and 2. As also shown in these figures, each outer connector 27 may be connected to one of the outer bus bars by means of a screw 38 which extends through opening 31 into the outer bus bar.

The outer connectors 27 are formed by bending rolled copper strap of uniform cross-section to the shape shown in Fig. 4. The two side edges of each arm 32 are cut away between the holes 33, as shown in Fig. 3, to reduce the width and increase the clearance between the connectors. This is desirable in the higher voltage panelboards where the electrical flash-over distance through air between two outer connectors 27 when they are adjacent to to each other and connected to phases A and C, as illustrated at 27a and 270 in Fig. l is not sufiicient to prevent flash-over, in view of the close spacing of the circuit breaker terminals. The greater width of the connectors at the terminal holes 33 is permissible because these terminal portions of the connectors 27 are each recessed in a depression 13 in the bottom of the circuit breaker housing 13 and the integral ribs of insulating material between adjacent depressions 13 form barriers 13 between the adjacent connectors giving adjacent flashover distance between the portions of the connectors recessed in the bottom of the breaker housings.

The main portion 30 between the openings 31 and 33 of the outer connectors 27 need not be of reduced width to give sufficient electrical clearance since, as is evident from Fig. 1, adjacent connectors 27 when connected to different phases extend in opposite directions from the center of the panel to the outer bus bars A and C and never have the main portions 30 of two connectors next to each other when they are at diiterent potentials. in fact, the full width of the main portion 30 is desirable to carry the maximum amount of current without excessive heating since the main portion 30 carries more current than does the arm 32. For example, if two opposite circuit breakers 12 are each of 100 ampere rating and each has one pole connected at one of the two openings 33 in a given connector 27, the current flow in the arm 32 of reduced width is only the 100 amperes passing through one breaker, whereas the main portion 30 of the connector carries the current of both breakers or a total of 200 amperes. it is thus seen that the construction disclosed makes eificient use of a minimum amount of copper, and at the same time cooperates with the recesses in the bottoms of the circuit breakers to permit close spacings Without flashover and thus keep the size of the whole panelboard to a minimum.

As explained hereinbefore, in the past it has been the practice to utilize comparatively heavy cast connectors containing a relatively large amount of copper in order to get the shapes desired and to carry the required amounts of current without exceeding the specified temperature rise for panelboard structures. Castings were used for the further purpose of providing a relatively large amount of contact area between the connector and the bus bar where the connector is connected to the bus bar in order 4 to prevent exceeding the specified temperature rise, since a connector bent from strips of the witdh permitted by the close spacings does not give sufficient contact area to permit adequate flow of current and heat into the bus bars.

In order to reduce the amount of copper in each connector, 1 have reduced the cross-sectional area of each connector and I have also reduced the direct contact area between the connector itself and the bus bar. In order to enable each connector to carry the same amount of current in spite of these reductions and without increasing the temperature rise in the connector, I have provided a supplemental connector 41 for each of the outer connectors 27 and a supplemental connector 41 for each of the center connectors 28. The connectors 41 and 41 are similar in structure, the connectors 41' being slightly narrower and shallower than the connectors 41 because of the smaller cross-section of the connectors 28 which is possible since each leg of the U has to carry the current of only one breaker.

As shown most clearly in Figs. 6 and 7, each supplemental connector 41 has a U-shaped portion 42 and a straight portion 43 which is integral with the U-shaped portion 42. As shown in Fig. 1, the U-shaped portion 42 is placed over the arm 29 of a connector 27 and attached thereto by means of the screw 38 which extends through an opening 44 in the supplemental connector 41 and the opening 31 in the connector 27 into the bus bar 11. The straight portion 43 is attached to the bus bar 11 by means of a screw 45 which extends through an opening 46 in the connector 41 into the bus bar 11.

The screws 38 and 45 extend into threaded openings 47 in each of the bus bars. The openings 47 are positioned at uniform intervals, equal to the terminal spacings of the breakers, along the length of the bus bars even though all of them will not be used in any particular panelboard assembly, since this simplifies manufacture and it is desirable that changes in the connections may be made in the field without drilling and tapping the bus bars. The length of the supplemental connectors 41 is made such that each screw 45 goes into the next hole 47 which is provided anyway, so no additional drilling is required to use the supplemental connectors.

It will be noted that the width of the supplemental connector 41 is substantially the same as the length of the arm 29 of the connector 27 which engages the flat surface of the bus bar 11. Furthermore, the area of the straight portion 43 of the supplemental connector which engages the surface of the bus bar 11 is equal to or greater than the area of the U-shaped portion 42 which engages the rectangular portion of the connector 27.

Thus, the eifective contact area between the connector 27 and the bus bar 11 is increased by means of the supplemental connector without increasing the size of the portion of the connector 27 which is actually in direct engagement with the bus bar 11. The increase in the contact area through the supplemental connector reduces the contact resistance between the connector 27 and the bus bar 11 and increases the capactiy of the connector for transmitting heat to the bus bar, thereby increasing the current carrying capacity of the connector without increasing the temperature rise. In this manner, the amount of copper in the connector 27 is materially reduced as compared with previous connectors for the same current rating and an overall saving in copper is made possible since the amount of copper required for the supplemental connector 41 is considerably less than the difference between the copper required for the present connector 27 and the prior connector.

Another important function of the supplemental connector 41 is to prevent turning of the connector 27 on the bus bar 11 about the single screw 38 which attaches the connector to the bus bar. Heretofore it has not been permissible to install the connectors in the spaces in the panelboards which were left vacant for the installation of circuit breaker units in the future, because of the '5 possibility-of the connectors turning about the screws 38 and reducing the amount of clearance between adjacent connectors. In fact, if it were possible for the connector 27c to rotate downwardly under force of gravity about its screw 45 it could touch the connector 27a and cause a direct short circuit across the buses.

In the present structure, it is impossible for a connector 27 to turn about the screw 38 when the supplemental connector 41 is provided, since the U-shaped portion 42 engages the rectangular arm 29 to prevent turning of the connector 27. Thus, each connector 41 performs the dual function of increasing the current carrying capacity of the connector 27 for a given temperature rise and preventing turning of the connector about its attaching screw.

As also shown in Fig. l, a supplemental connector 41 is attached to each one of the center connectors 28. As previously explained, the supplemental connector 41' is similar in structure to the connector 41 and it is attached to the connector 28 in the same manner as the connector 41 is attached to the connector 27. Thus, the connector 41' increases the effective contact area between the connector 28 and the center bus bar 11, thereby increasing the capacity of the connector to transmit heat to the bus bar and decreasing the electrical resistance between the connector and the bus bar.

The relative sizes of and the difference in the amount of copper in the present connector 28 and a prior connector 28' is illustrated in Fig. 10, in which one of the present connectors 28 and its supplemental connector 41 are shown attached to a portion of a bus bar 11 and a prior connector 28 is also attached to the bus bar 11. It is quite obvious that the amount of copper required for the connector 28 and its supplemental connector 41 is materially less than the amount of copper required for the prior connector 28, but at the same time the area in contact with the bus bar is kept large. Thus, the cost of producing the present connectors is reduced and, furthermore, copper is saved, thereby making it available for other uses.

From the foregoing description, it is apparent that I have provided connectors suitablefor use in panelboards or other electrical apparatus which have an increased current carrying capacity for a given temperature rise and which may be rigidly attached to bus bars in a simple manner. The present connectors require considerably less copper than prior connectors of corresponding ratings.

Since numerous changes may be made in the abovedescribed construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all mtater contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a panelboard, in combination, a cabinet, a circuit interrupter disposed in the cabinet, a bus bar, a branch circuit connector for connecting the interrupter to the bus bar, a supplemental connector having a portion directly engaging the branch circuit connector and a portion directly engaging the bus bar, securing means extending through the supplemental connector and the branch circuit connector into the bus bar, and additional securing means extending through the supplemental connector into the bus bar, thereby increasing the etfective contact area between the branch circuit connector and the bus bar.

2. In a panelboard, in combination, a bus bar, a branch circuit connector, a supplemental connector having a portion directly engaging the branch circuit connector and a portion directly engaging the bus bar, threaded means extending through the supplemental connector and the branch circuit connector into the bus bar for attaching the branch circuit connector to the bus bar, and additional threaded means extending through the supplemental connector into the bus bar for attaching the supplemental connector to the bus bar, thereby increasing the effective contact area between the branch circuit connector and the bus bar.

3. In a panelboard, in combination, a cabinet, a circuit interrupter disposed in the cabinet, a bus bar having a flat surface, a branch circuit connector having a fiat surface in direct contact with the flat surface of the bus bar for connecting the interrupter to the bus bar, a supplemental connector having a portion directly engaging and attached to the branch circuit connector and a portion directly engaging the bus bar, securing means for attaching the branch circuit connector to the bus bar, and additional securing means for attaching the supplemental connector to the bus bar, thereby increasing the effective contact area between the branch circuit connector and the bus bar.

4. In a panelboard, in combination, a bus bar, a branch circuit connector having one side engaging the bus bar, a supplemental connector having a portion engaging the side of the branch circuit connector opposite the bus bar and a portion directly engaging the bus bar, and securing means extending through said connectors at different places for attaching them to the bus bar, thereby increasing the effective contact area between the branch circuit connector and the bus bar.

5. In a panelboard, in combination, a bus bar, a branch circuit connector having a generally rectangular portion with one side engaging the bus bar, a supplemental connector having one portion engaging the side of the branch circuit connector opposite the bus bar and another portion directly engaging the bus bar, a screw extending through the supplemental connector and the branch circuit connector into the bus bar, and another screw extending through the supplemental connector into the bus bar, thereby increasing the effective contact area between the branch circuit connector and the bus bar.

6. In a panelboard, in combination, a cabinet, a plurality of circuit interrupters disposed in the cabinet, a plurality of bus bars, a branch circuit connector having a generally rectangular portion with one side engaging a bus bar to connect an interrupter to the bus bar, each interrupter having a recess in its bottom for receiving its connector, a supplemental connector having one portion engaging the side of the branch circuit connector opposite the bus bar and another portion engaging the bus bar, and securing means for attaching said connectors to the bus bar at different places.

7. In a panelboard, in combination, a cabinet, a circuit interrupter disposed in the cabinet, a bus bar, a branch circuit connector having a generally rectangular portion with one side engaging the bus bar to connect the interrupter to the bus bar, said interrupter having a recess in its bottom for receiving the connector, a supplemental connector having an offset portion engaging at least two sides of the branch circuit connector and another portion engaging the bus bar, and securing means for removably attaching said connectors to the bus bar at different places.

8. In a panelboard, in combination, a bus bar having spaced holes therein, a branch circuit connector having a generally rectangular portion with one side engaging the bus bar, a supplemental connector having a U-shaped portion engaging the other three sides of the rectangular portion of the branch circuit connector and a straight portion engaging the bus bar, and securing means for attaching said connectors to the bus bar at different ones of said holes.

9. In a panelboard, in combination, a bus bar having threaded holes therein, a branch circuit connector having a generally rectangular portion with one side engaging the bus bar, a supplemental connector having an oifset portion engaging at least two sides of the rectangular portion of the branch circuit connector and a straight portion engaging the bus bar directly, the width of the supplemental connector being substantially equal to the length of the side of the circuit connector which engages the bus bar, and screw means in different ones of said threaded holes for attaching said connectors to the bus bar.

10. In a panelboard, in combination, a bus bar having spaced holes therein, a branch circuit connector having a generally rectangular portion with one side engaging the bus bar, a supplemental connector having a U-shaped portion engaging the other three sides of the rectangular portion of the branch circuit connector and a straight portion engaging the bus bar, the area of the straight portion of the supplemental connector being substantially equal to the area of the portion of the circuit connector which is engaged by the supplemental connector, and threaded means disposed in different ones of said spaced holes for attaching said connectors to the bus bar.

11. In a panelboard, in combination, a cabinet, a plurality of circuit breakers disposed in the cabinet in sideby-side relation and having spaced terminals thereon, a plurality of bus bars having holes therein on spacings corresponding to the breaker terminal spacings, branch cir cuit connectors for connecting the breaker terminals to the bus bars, supplemental connectors engaging the bus bars and the branch circuit connectors, each supplemental connector being in direct contact with a branch circuit connector and a bus bar and having at least two holes therein on the same spacing as the holes in the bus bars, and securing means disposed in both of said holes for attaching the branch circuit connectors and the supplemental connectors to the bus bars.

12. In a panelboard, in combination, a cabinet, a pinrality of circuit breakers disposed in the cabinet in sideby-side relation and having spaced terminals thereon, a plurality of bus bars having holes therein on spacings corresponding to the breaker terminal spacings, branch circuit connectors for connecting the breaker terminals to the bus bars, supplemental connectors engaging the bus bars and the branch circuit connectors, each supplemental connector being in direct contact with a branch circuit connector and a bus bar and having holes therein on the same spacing as the holes in the bus bars, threaded means extending through a supplemental connector and a branch circuit connector into a bus bar in certain of said holes,

and additional threaded means extending through the supplemental connector into the bus bar in others of said holes.

13. In a panelboard, in combination, a plurality of circuit breakers disposed in the cabinet in two parallel rows with an intervening space between the rows, said breakers having spaced terminals thereon, a plurality of bus bars having holes therein on spacings corresponding to the breaker terminal spacings, branch circuit connectors of formed rolled strip material for connecting the breaker terminals to the bus bars, supplemental connectors engaging the bus bars and the branch circuit connectors, each supplemental connector being in direct contact with a branch circuit connector and a bus bar and having at least two holes therein on the same spacing as the holes in the bus bars, and securing means disposed in both of said holes for attaching the branch circuit connectors and the supplemental connectors to the bus bars.

14. In a panelboard, in combination, a plurality of circuit breakers disposed in the cabinet in two parallel rows with an intervening space between the rows, said breakers having spaced terminals thereon, a plurality of bus bars having holes therein on spacings corresponding to the breaker terminal spacings, branch circuit connectors of formed rolled strip material for connecting the breaker terminals to the bus bars, certain of said connectors being reduced in width in said intervening space, supplemental connectors engaging the bus bars and the branch circuit connectors, each supplemental connector being in direct contact with a branch circuit connector and a bus bar and having at least two holes therein on the same spacing as the holes in the bus bars, and threaded means disposed in both of said holes for attaching the branch circuit connectors and the supplemental connectors to the bus bars.

References Cited in the file of this patent UNIT ED STATES PATENTS l,39l,9l6 Sweet Sept. 27, 1921 l,536,l.49 Schmid May 5, 1925 1,876,536 Alsaker Sept. 13, 1932 1,945,393 Chapman Jan. 30, 1934 2,007,174 Benjamin July 9, 1935

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