US2846529A - High current switch - Google Patents

Description

Aug. 5, 1958 H. w. GRAYBILL arca cunaan'r snncn 2 Sheets-Sheet 1 Filed April 5. 1954 4aa- 75a nur.;

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3l Z2 O/ o/ Aug. 5, 1958 H. w. GRAYBILL HIGH CURRENT SWITCH Filed April 5. 1954 2 Sheets-Sheet 2 United States Patent Office.

l 2,846,529 Patented Aug. 5, 1958 2,846,529 HIGH CURRENT SWITCH Howard'W. Graybill, Greensburg, Pa., asalgnor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation ot Pennsylvania,

Application April 5, 1954, No. 420,976

Claims. (Cl. 20G-16) My invention relates to high current switch and is more particularly directed to a novel switch structure having a pair of bridging contact members which are particularly adaptable for bridging terminal bars which are in close proximity to each other.

The novel switch of my invention is particularly applicable for low voltage and high current rating.

One particular example of ,the application of this switch is in circuitry involving electrolytic cells such as aluminum pots or sodium cells. In these cases, the individual pots or cells operate at a relatively high current, for example from 30,000 to 100,000 amperes and with relatively low voltage of between 5 and 6 volts.

A plurality of cells are usually connected in series to form a pot-line which operates the voltage between 400 and 750 volts and the total pot-line current passes through each cell. l

When one of the cells or potsis to be removed from service for maintenance or repair, it is necessary to shortcircuit this unit.

The prior art arrangement used in the aluminum industry to shortcircuit the cells is to use copper wedges as switches, as shown in Figure 1 in my copending application Serial No. 357,021, filed May 25, 1953which matured to Patent No. 2,766,335 on October 9, 1 956.

The pot-line bus is made up of a plurality of sections, each of which-consists of between 8 and l0 bars of aluminum or copper. These bars arranged with a wedge-shaped gap which is so arranged that the gap in the bus isin parallel with the cell. The normal current tlow is, therefore, through the cell or pot-line.

To shortcircuit the cell or pot, a copper wedge is driven into the wedge shaped gap in the bus and if the shortcircuit is to be maintained for any appreciable period of time, the heavy copper plates are bolted to either side of the bus. As described in my copending application Serial No. 357,021, filed May 25, 1953, this procedure is both time consuming, expensive and dangerous.

The switching structure shown in my copending application Serial No. 357,021, filed May 25, 1953, is particularly adaptable for a plurality of` spaced parallel buses wherein the wedge shaped gap runs the width of the pending application Serial No. 317,101, tiled October 65 27, 1952, which matured to Patent No. 2,743,338 on VApril 24, 1956, is particularly adaptable for laminated bar configurations which are spaced close together. This is achieved by having a pair of moving contacts for each pair of terminal bars and so arranged that one of the 7o lmcwing contacts moves into the wedge shaped gap from either side ot the bus. All oi the contacts are controlled from a single point and their operation occurs simultaneously.

' 'I'he construction of my novel switch, when applied to a plurality of closely spaced parallel terminal bars, re-

5 solves all the vertical and horizontal forces so that the forces resulting from the contact pressure are completely self-contained in the switch with no external forces being exerted on the terminal bar structure. Y

Accordingly, a primary object of my invention is to provide a novel high current switch which is particularly adaptable for use with a plurality of spaced parallel terminal bars which are spaced apart a distance no greater than the thickness of the bars.

.Another object of my invention is to provide a novel l5 high current switch for terminal bars wherein all of the forces resulting from the contact pressure are selfcontained in the switch so that there are no external forces on the bus to which the switch is connected.

A still further object of my invention is to provide a novel switch structure in which a pair of contacts simultaneously move in opposite directions to bridge a gap in a `terminal bar. v

A still further object of my invention is to provide a switch in vwhich only two parallel bridging contacts will carry the same current as the associated terminal bar of the order of 6,000 amperes and higher with a temperature rise not exceeding that of the bus to which it is attached.

A still further object of my yinvention is to providea novel high current switch having a pair of bridging contacts; for each terminal bar with which it is associated wherein all pairs of contacts are simultaneously moved to bridge the gaps between the terminal bars.

These and other objects of my invention will be app'arent from the following description when taken in connection with the drawings in which:

Figure 1 is a schematic wiring diagram illustrating one particular use of my novel high current switch used as a shortcircuiting switch.

40" Figure 2 is a side elevation viewof my high current switch illustrating the control mechanism for simultaneously operating a pair of bridging contacts for an upper and lower pair of terminal bars.

Figure 3 is a side elevation view of my high current switch similar to Figure 2 with the crank mechanism of the switch removed and illustrates the three positions of the bridging contact, namely, closed, contact parting and open.

taken along the line and in the direction of the arrows 4-4 of Figure 3.

Referring now to the schematic diagram of Figure 1, I have shown a direct current source 10 which supplies current to a plurality of cells 11a, 11b, etc., which are connected in series.

The source voltage may be between 400 and 750 volts 4-ancl since there are usually more than a hundred pots ysimilar to 11a connected in series thereacross, the voltage across each cell is between 5 and 6 volts. The source is usually capable of delivering between 30,000 and 100,000 amperes to each of the cells connected in series.

,r If it is necessary to remove one of the cells, as, for

example, cell 11a, a shortcircuiting switch 12 must be provided to shortcircuit the cell.

The bus bars 13 may consist of between 8 or more spaced parallel bars so that each bar will carry approximately 3,000 amperes. Since there are a pair of convtacts associated with each pair of bars, it is necessary Ato design the switch to carry approximately 3,000 amperes cuited.

My invention is directed to the switch 12, the construction of which is shown in Figures 2, 3, and 4.

'Ihe pluralityof spaced parallel bars is shown in the sectional view of Fig. 4.

For the sake of simplicity, I have yshown only four spaced parallel bars 14a, 14b, 14e and 14d. However, it will be understood that the novel switch can be conl structed and is readily adaptable to a terminal bar congreater than the width of the bars.

'Ihe bats in each vertical line are comprised of a top or upper and bottom or lower section, designated, respectively, by the letters T and .B,v wherein a wedge shaped gap on each side separates the pair. Thus, as best seen in Figures 2 and 4, the lower terminal bar ,14aB is spacedfrom the upper terminal bar 14al' by the wedge shaped gap 16R and 16L. l

Diamond shaped insulating plates 17 and 18 parallel to the terminal bars 14 are positioned'at the outer eittremities of the switch torsecure and position the operating components of the bridging contact members in a manner hereinafter more fully described.

The interrupting plates 17 and 18 may be a laminated insulation polyester or melamine resin with glass cloth or could be a metal with an insulating sleeve over the bolts 19T and 19B which secure the sandwiched combination of the copper terminal bars 14, the transite spacers and the diamond shaped insulating plates 17 and 18.

The bolts 19T,and 19B clamp the entire structure together and Ahave Belleville washers 20B and 20T positioned below the nuts 21T and 21B in order to maintain proper pressure in the event of shrinkage of the insulation due to drying-out.

The top or upper terminal bars 14T and the bottom or lowerterminal bars 14B are provided withl a plurality of openings 2 2 which can receive appropriate bolts or clamping means in order to secure the switch to the terminal bars which shunt the cell or pot to be short-circuited.

As will be best seen in Figures 2 and 3, the switch is symmetrical about the lvertical center line.

The diamond shaped interrupting plates 17 and 18 support the two operating shafts 22R and 22L.

The semicylindrical elongated contacts 23R and 23L each are provided with independent contact pressure springs 24 and are controlled from the' operating shafts 22R and 22L through the linkage 25 in the manner fully described and set forth in my copendingapplication Serial No. 317,101, filed October 27, 1952.

'Ihe contact members 23 are coated with a heavy silver plating. The manner in which the bridging contacts 23 coopereate with the stationary contacts formed by the wedge shaped gap between the top and bottom terminal bars 14 will hereinafter be more fully described.

As has been fully set forth in my copending application Serial No. 317,101, filed October 27, 1952, the rotation of the shafts 22 will rotate the associated bridging contact into and out of engagement with the stationary "the plurality of bridging contacts 23R and 23L are moved simultaneously. The shafts 22R and 22L simultaneously operated will now be described.

The crank 27R and 27L are, respectively, attached to 4 i theshaft22R and 22L bypinni'ng,keyingorother able means, as best'seen in Figure 2.

stit- One end of the insulating link 28 is pivotally secured the second shaft in an oppodte direction and at mately the-same rate of angular rotation.

A socket 29 is secured to one end of the operating shaft 22L and is provided with an operating handle 30 which may be manually controlled. The position of the components when the shortcircuiting switch is in the fully closed position is illustrated in Figure 2'. It will be noted that any desirable means may be utilized in order to latch or lock the components in the closed position. I

The switchis openedbyrotatingthehandlel'ina clockwise direction for'approximately 60 as this -will transmit a direct force to the operating shaft 22L and rotate this shaft in a similar 60 'clockwise ln addition, the force from the operating handle will be.. 1 transmitted through the crank 27L, the insulating link 28, through the crank 27R to thereby rotate the operatthe position of the contact when it is in the fully closed .ofFigure2. As'canbebestaeenln l contact is the same.

position, the broken solid line illustrates the position of the contact during the opening operation and line illustrates the position ofthe contact in the fully opened position.

.The position of the crank 271. when the switch the fully open position is illustrated of'Figure 3, the bridging contact initially has longitudinal movement imparted thereto by the rotation of the operatingshaft22andafteritengages the stationarycon tacts formed by the wedge shaped gap within the bars l14, continued rotation of the shaft 23 merely rocks to the horizontal center line of the wedge shaped gap. Hence, since the final movement of the movable contact is a rotational movement, the initial surface of the movable contact which engages the stationary contact isy not the same as the final surface which remain in permanent electrical engagement with the stationary contacts. It pitting should occur on the contact, it will notbeon the surface of the movable contact which finally the stationary contact. The coating of heavy silver plating is all that is necessary to properly protect the movable contacts.

However, as is clearlylseen in the moving picture view of Figure 3, the portion of the stationary contact which is initially engaged by the bridging contact member 23 is the same area that is nally engaged by the bridging contact. 'I'hat is, since the bridging contact after initial engagement with the stationary contact no longer has longitudinal movement, it is instead restricted to rotational movement.

Both the initial and final contact area of the stationary Hence, if pitting should occur at this point, it will exist in the area of the stationary contact which isA intended to carry current for an appreciable length of time. Thus, it can be seen'that it is desirable to provide means to eliminate pitting of the stationary contact although this is not necessary for the movable contacts.

In Figures 2 and 3, I have illustrated one means whereby pitting of the stationary contact can be eliminated. This is achieved by brazing refractory pieces 38-31 of silver tungsten on the stationary contact of the portion of the terminal bar which is nearest to the operating handle. Thus, for example, silver tungsten pieces 38-31 will be a lied onl to the gap 16L of the terminal bars l4-14a. bleither they remaining bars 14a, 14h. 14e nor the right hand side air gap 16R will havev a silver tungsten piece 1. sofi-sahereinafter noted, since all of the bridging contacts 23aR 23aL, 23bR, 23bL, 23cR, 23cL, 2 3dR ZM'L are simultaneously operated and since a' raised portion is provided on the lefthand side in theleft wedge shaped gap of the terminal bars or 14a, the bridging contact 14aL will enage the stationary contacts before and disengage the stationary contacts after all ofthe remaining bridging contacts have engaged or disengaged, respectively.

Hence, any pitting which may occur will be confined.

A to the wedge shaped gap 16L of the terminal bar 14a and more particularly will be confined to the silver tungsten pieces 30-31 which are brazed thereon.

Since the pitting will be confined to this particular area, after continued use of several hundred operations, the pitted silver tungsten pieces 30--31 can be removed and new pieces can be brazed thereon. In this manner, the bridging contact 23aL is considered the arcing contact confining any damage which may be done due to pitting of the pieces 30--3ll.

The shortcircuiting switch of my instant application is designed to carry current in the range of 3,000 amperes for each moving contact. I

Since the width of the movable contacts 23 is limited to twice the width of the terminal bars 14,l when the tern minal bars are spaced from each other by a space not greater than the width of the bars, it is necessary to provide means to dissipate any excess of heat which maybe generated by the 12R losses. This is achieved by making the bridge contacts elongated semi cylindrical'members so that the excess heat can be dissipated by radiation and convexion by the portion of the contact which is not in engagement with the terminal bars lf.

Since the shortcircuiting switch set forth in my copending applications Seriall N0. 317,101, filed October 27, 1952, and Serial No. 357,021, filed May 25, 1953, is designed primarily to have currents in the range of approximately 600 amperes for each contact. It is not necessary to provide an elongated contact and, hence, only the semi cylindrical contact is shown.

However, in my instant application, each bridging coritact 23 would have to carry as much as 3,000 amperes and, hence, the elongated portion is provided for the reasons noted.

As will be clearly seen in Figures 2 and 3, the diamond shaped insulating bracket 17 is provided with a vertical portion 33. The diamond shaped bracket 18, a sectional view of which isseen in Figure 4, is also provided with a comparable vertical section 33.

When the switch is closed, the horizontal components of the reaction forces due to the contact pressure springs 24 are in opposite direction thereby balancing each other. That is, since the pair of moving contacts 23R and 23L move into the wedge shaped gap 16R and 16L from opposite sides of the busbar, the horizontal components of the reaction forces are balanced.

The vertical component of the forces tend to push the bottom of lower or terminal bars 14B down and the top or upper terminal bars 14T up awayv from the center of the switch. However, these reacting forces are balanced by tensional forces in the vertical portion 33 of the diamond shaped insulating brackets 17 and 18 which' are located at both sides of the switch. Hence, the reacting forces due to the contact pressure springs 24 impart no 'strain on the busto which the switch is connected.

6. I claim: 1. A high current switch comprised of a plurality of terminal bars; a pair of insulating brackets; a first and second operating shaft; and a first and second plurality of bridging contacts; said plurality of terminal bars spaced `of bridgingcontacts associated with said second gap'in each terminal bar; said first operating shaft being operatively connected to and controlling said first plurality of bridging contacts to engage and disengage said first wedge shaped gaps; said `second operating shaft being operatively connected to and controlling said second plurality of bridging contacts to engage and disengage said second wedgeshaped gaps; means to simultaneously control said first and second operating shaft.

2. A shortcircuiting switch comprised of a plurality of terminal bars, a pair of diamond shaped insulating brackets, a first and second operating shaft, and a first and Second plurality of bridging contacts; said plurality of f terminal bars spaced from each other by insulating means having a width approximately equal to the width of said terminal bars; said pair kof diamond shaped insulating brackets secured to each side of said spaced parallel terminal bars and insulating means; said diamond shaped insulating plates supporting said first and second operating shaft; each of said terminal bars having a first and second wedge shaped gap communicating with each other; said first plurality of bridging contacts associated with said first gap in each terminal bar; said second plurality of bridging contacts associated with said second gap in each terminal bar; said first operating shaft controlling said first plurality of bridging contacts to engage and disengage said first wedge shaped gaps; said second operatiig shaft controlling said second plurality of bridging members for engagement and disengagement with said second wedge shaped gaps; means to simultaneously control said first and second operating shaft; said diamond shaped insulating plate balancing the horizontal and vertical forces of said switch thereby-eliminating external forces.

3. A shortcircuiting switch comprised of a plurality of terminal bars, a first and second operating shaft, a first and second plurality of bridging contacts; said plurality of terminal bars spaced from each other by insulating means having a width approximately equal to the width of said terminal bars; each of -said terminal bars having a first and second wedge shaped gap `communicating with each other; said first plurality of bridging contacts associated with said first gap in each terminal bar; said second plurality of bridging contacts associated with said second gap in each terminal bar; said first operating shaft controlling said first plurality of bridging contacts into and out of bridging engagement with said wedge shaped gaps; said second operating shaft controlling said second plurality of bridging members for engagement and disengagement with said second wedge shaped gaps; refractory material on one side of said wedge shaped gaps to eliminate arcing or pitting on the remaining wedge shaped gaps; means to simultaneously control said first and second operating shaft.

4. A high current switch comprised of a plurality of terminal bars; a pair of insulating brackets; a first and second operating shaft; and a first and second plurality of bridging contacts; said plurality of terminal bars spaced from each other by insulating means having a width approximately equal to the width of said terminal bars; said pair of insulating brackets Secured to each side `of said assassin spaced parallel terminal bars; said insulating brackets supporting said first and second operating shaft; each of said terminal bars having a first and second wedge shaped gap communicating with each other; said first plurality of bridging contacts associated with said first gap in each terminal bar; said second plurality of bridging contacts associated with said second gap in each terminal bar; said first and second plurality of bridging contacts being semicylindrical elongated members to dissipate heat by radiation and convexion; said first operating shaft being operatively connected to and controlling said first plurality of bridging contacts to engage and disengage said first wedge shaped gaps; said second operating shaft being operatively connected to and controlling said second plurality of bridging members for engagement and disengagement with said second wedge shaped gaps; means to simultaneously control said first and second operating shaft.

5. A shortcircuiting switch comprised of a plurality of terminal bars; a pair of diamond shaped insulating brackets; afirst and second operating shaft; and a first and second plurality of bridging contacts; said plurality 'l other; said first plurality of bridging contacts associated 30 with said first gap in each terminal bar; said second pluralityof bridging contacts associated with said second gap in each terminal bar; biasing means for said first and second plurality of bridging contacts and said first and gagement and disengagement with said second wedge i shaped gaps; means to simultaneously control said rst and second operating shaft; said diamond shaped insulatmg plates balancing all of the forces resulting from said biasing means thereby eliminating external forces of said switch. v y

References Cited in the file of this .patent UNITED STATES PATENTS 1,214,083 Schultz Jan. 30, 1917 1,399,493 Krantz Dec. 6, 1921 1,968,869 Austin Aug. 7, 1934 2,306,565 Ramsey Dec. 29, 1942 2,571,794 Turner Oct. 16, 1951 2,658,971 Wettstein Nov, 10, 1953 FOREIGN PATENTS 420,125 France Jan. 23, 1911 431,074 Italy Feb. 23, 1948 966,165 France s Mar. 1, 1950`

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