US2419106A - Oil circuit breaker - Google Patents

Description

April 15, 1947. B. P. BAKER ET A1. 2,419,106

OIL CIRCUIT BREAKER Filed Jan. 29, 1944 Patented Apr. 15, 1%?

UNITED STATES PATENT GFFICE OIL CIRCUIT BREAKER Benjamin P. Baker, Turtle Creek, and Robert C.

Dickinson, lVilkinsburg, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania pratica-tion January 29, 1944,-Serial No. 520,254

(Cl. ZOO-150) l5 Claims.

ysimple and inexpensive arc-extinguishing structure which s effective for interrupting both high and low currents.

Another' object of the invention is to utilize the moving Contact as a piston for providing a flow oi arc-extinguishing liquid to extinguish the are.

A further object of the invention is to utilize a single arc-extinguishing structure into which a bridging Contact member is movable to draw two arcs, one at each end of the bridging meinber.

It is also an object of the invention to mount the arc-extinguishing structure at a distance yfrom `a stationary Contact so that the extinguishing structure does not cover the Contact and prevent inspection of the contacts.

Another object in having the .arc-extinguishing structure spaced from the stationary contact is to give the further advantage that an isolating gap oi insulating liquid is provided between the stationary Contact and the extinguishing structure, so that good insulation is obtained between the stationary and moving contacts immediately after are Aextinction and before the moving contact has moved to full open position. This reduces the tendency toward reignition of the arc over the surface or" the vextinguishing chamber if it should become coated with carbon.

An additional object of the invention lies in the provision of a structure in which the moving contact is allowed to move freely to quickly obtain sufficient arc length for `interruption during the initial part of the opening stroke, and is then lengthened more slowly within an interrupting structure which begins to extinguish the arc after the initial part of the opening operation. This keeps the arc energy to a minimum and requires only a minimum of mechanical power to open the circuit land extinguish the arc.

A further object of the invention is to utilize the kinetic energy, which is stored in the moving `Contact during its initial movement, to move the arc extinguishing liquid to assist in interruption of the arc. This useful dissipation of the kinetic energy of the moving Contact eliminates any necessity for providing dashpots for stopping the Contact and preventing bouncing thereof.

It is another object of the invention to so arrange the contacts and arc-extinguishing structure thatfthe magnetic force of the current loop assists in `driving the moving contact in opening direction, and yto utilize this magnetic driving `force to give piston action for moving liquid through the iarc to extinguish it. This is .particularly eiective for the interruption vof heavy currents where the vmagnetic forces are large.

Another object of the invention is-to initially draw vthe arc outside of the arc-extinguishing lchamber so vas to permit immediate escape of the are gases until the arc has been lengthened suinciently to Vpermit interruption. This ease of escape for the gas first formed keeps the pressure in the arc-extinguishing vchamber low until the pressure can be used effectively to extinguish the arc without reignition. The arrangement prevents destructive pressures from building up with the initial rise of arc voltage, as has taken place in prior art structures `before the vents have been denuded of the arc-extinguishing liquid which blocks the escape 'of gas.

Other objects and advantages of the invention will be apparent from the following description of the specic modications shown on the drawing, in which:

Figure 1 is an elevational view of a Vcircuit breaker embodying kthe invention, with the tank broken away to show the contact and arc-extin-guishing structure. The contacts Vare shown in closed position.

Figure 2 is an enlarged view in section through theatre-extinguishing chamber showing the contacts in separated position.

Figure 3 is a sectional view through the arcextinguishing structure taken on the line III- III of Fig. 2 and looking upwardly.

Figure 4 is a sectional View similar to Fig. 3 but showing a modified arc-extinguishing structure.

The circuit breaker of the .invention is lshown for purposes of illustration as comprising a tank 5 containing a 'body of insulating and arc-extinguishing liquid, such as oil .'l. A pair of insulating bushings 9 extend through the top of the tank 5 and have conductors Il extending therethrough. .Stationary-contacts I3 are mounted on the lower end of each of the lead-in conductors II. A kunitary arc-extinguishing structure l5 is mounted below the contacts :I 3 by being suspended from the top r(i of the vtank 5 by a pair of insulating rods Il.

The interrupting or arc-extinguishing chamber I5 'is shown as being built up of a stack of insulating plates I9 and 2|. Each of the plates I9 and 2l are oval 'in shape. The plates I9 have a smaller oval opening 23 than `the openings 25 of the alternate plates 2I, so that the arc-extinguishing chamber has a corrugated surface which not only provides a longer breakdown path, but also provides recesses which retain the arc-extinguishing liquid and cause turbulence as the liquid and arc gases now out of the structure. A bottom plate 21 closes the lower end of the interrupting structure while the upper end is open. It is understood that the lower end of the arcextinguishing structure need not be completely closed but may have a small bleed or vent opening.

The electrical circuit is completed between the stationary contacts I3 by a conducting bridging member 29 which is mounted on an insulating contact-operating rod 3i which may be actuated by any suitable mechanism for opening and closing the circuit. Moving contacts 33 are mounted on each end of the conducting bridging member 29 for engagement with the stationary contacts I3.

As shown best in Figure 3, the bridging member 29 is made to t rather snugly within the opening of the arc-extinguishing chamber so as to act as a piston. Passages 35 adjacent the ends of the bridging member 29 and/or openings 31 through the bridging member are provided so that as the bridging member moves into the arcextinguishing chamber, the liquid under the bridging member is forced by piston action to ow upwardly through the passages 35 and/or 31 and longitudinally through the arc space between the contacts I3 and 33. Insulating barrier members 39 may be mounted on the bridging member 29 for conning the arc and the now of liquid and gas to the arc space between the contacts I3 and 33.

The upper end of the arc-extinguishing chamber I is mounted at a distance from the stationary contacts I3 so that there is a clear gap in the insulating liquid between the contacts I3 and the top of the aro-extinguishing chamber. This provides good insulation immediately after the arc is formed so that if the interior of the chamber should become coated with carbon from decomposed oil, there will be a gap through clean oil to provide insulation, and to render unlikely restriking of the arc over the surface of the chamber after the arc has been once extinguished, even though the moving conta-ct has not yet moved to full open position.

Effective arc-extinguishing action during the interruption of both high and low currents is obtained because of the piston action of the bridging member 29, which causes upward now of the arc-extinguishing liquid through the are space between the contacts I3 and 33. If the current being interrupted is small, it will be extinguished largely because of the forced flow of liquid by the bridging and piston member 23 whereas, if the current interrupted is larger, there will be an increased amount of liquid turned into gas which will also now upwardly and longitudinally of the arc in the space between the contacts I3 and 33. The corrugated internal surface of the arc-extinguishing chamber retains the arc-extinguishing liquid -along the arc path and also causes turbulence in the outward flow of gas and liquid to further break up the arc stream.

It will be noted that the current flows in a looped path extending downwardly from one lead-in conductor II through one arc to one end of the bridging member 29, then across the bridging member and up through the other arc to the other lead-in conductor II. During the interruption oi heavy currents, this loop tends to enitself because of the magnetic action. This has two advantages. First, the magnetic force to move the bridging and piston member 29 downwardly so as to give a stronger piston action. Second, the arcs are moved outwardly into Contact with the corrugated end portions of the extinguishing chamber and are held adjacent the pockets which supply oil for extinguishing the arcs.

The fact that the top of the extinguishing chamber l5 is mounted below the stationary contacts I3 has the advantage that the condition of the contacts I3 and their engagement with the moving contacts 33 on the bridging bar 29 when the breaker is closed, may be readily inspected without demounting the arc-extinguishing chamber I5. rlhe space between the stationary contacts I3 and the top of the arc-extinguishing chamber I5 also permits the bridging and piston member 29 to be accelerated during the opening part ci its stroke without substantial retarding action. This permits kinetic energy to be stored in the moving contact which is later available for forcing oil to iiow by piston action through the arcs. The arc-extinguishing chamber has its greatest retarding eiiect at the very end of the stroke of the moving contacts, where it is desirable to give dashpot action and bring the moving contacts to rest without bouncing or excessive forces on the operating mechanism.

The spacing of the top of the arc-extinguish ing chamber l5 from the stationary contacts I3 also has the advantage that free venting of the arc space is obtained when the arc is iirst drawn and is of short length. This keeps the pressure low until after the arc has been drawn into the arc chamber, and gives a better flow of gas and liquid after the arc has been drawn to such a length that it may be extinguished. It also prevents the building up of pressures in the arcextinguishing chamber, which might be destructive unless the chamber is made of extremely strong construction.

The modification shown in Figure 4 is mounted and arranged in the same manner as shown in Figs. l to 3, the only diiierence being in the construction of the end portions of the arc-extinguishing chamber. The plates 4I having the smaller opening 43 are provided with recesses 45 along a slot at each end thereof. Surrounding the slot is a U-shaped recess in which is embedded a U-shaped magnetic member 41. The plates 49 having the larger openings 5I are provided at their ends with narrow slots 53.

When the arc is drawn between the stationary contacts I3 and the moving contacts 33 on the ends of the bridging and piston member 29, a magnetic held is induced in the magnetic members 41 which acts to magnetically draw the arcs into the narrow slots 53 and into the pockets 45. The narrowness of the passage into which the arc is moved provides a strong deionizing action and holds the arc directly in the path of the out-flowing gas and liquid to quickly extinguish it.

It is apparent that the narrow slots 53 and the pockets 45 in the ends of the extinguishing chamber may be used without the use of the magnetic plates 41 since the magnetic repulsion between the two sides of the looped current path may be relied upon for moving the arcs into the narrow slots. In other respectsy the modified structure shown in Figure 4 operates in the same manner and with the same advantages set forth in describing the modication shown in Figures 1 to 3.

While two specific embodiments of the inven- S tion have been described, it is vobvious that other changes and modifications may be made without departing from the spirit and scope of lche invention as set forth in the claims.

We claim as our invention:

1. In a circuit breaker, a container of arcextinguishing liquid, a pair of insulated lead-in conductors extending into the container, a contact on the 'inner end of each of said conductors, an arc-extinguishing chamber mounted in said container independently of and spaced from the inner end portions of said lead-in conductors and separated by liquid therefrom, bridging means which in closed position completes the electrical circuit between said contacts, said arc-extinguishing `chamber having its interior of a size to closely receive said bridging means therein, means for moving the bridging means into the chamber for drawing the arcs into the chamber and forcing liquid to ow out of the chamber through the arc.

2. In a circuit breaker, a container of arcextinguishing liquid, a pair of insulated lead-in conductors extending into the container, a contact on the inner end of each of said conductors, a stationary arc-extinguishing chamber mounted in said ycontainer independently of the inner end portions of said lead-in conductors and separated by liquid therefrom, movable bridging and piston means including conducting material for completing `the electrical circuit between said contacts, means for moving said bridging and piston means to open the circuit by moving into said chamber, said bridging and piston means having an area tting rather snugly into said chamber except adjacent the arcs for forcing liquid to iiow through the arcs as it flows out ci the chamber `when the piston moves in.

3. In a circuit breaker, a container of arcextinguishing liquid, a pair of insulated lead-in conductors extending into the container, a contact on the inner end of each of said conductors, a single yarc-extinguishing chamber for the arcs from both contacts mounted in said container independently of the inner end portions of said lead-in conductors and separated by liquid therefrom, bridging and piston means `movable from a position where its end portions engage and complete the electrical circuit between said contacts to a position within said single arc-extinguishing chambery said bridging and piston means having a portion substantially filling the opening in the arc-extinguishingchamber except for one or more passages adjacent the ends thereof through which liquid is forced to ow by pisto-n action to eX- inguish both arcs.

d. In a circuit breaker, a container of arcextinguishing liquid, a pair of insulated lead-in Vconductors extending into the container, a contact on the inner end lof each of said conductors, an are-extinguishing chamber mounted in lsaid container independently of the inner end portions of said lead-in conductors and separated by liquid therefrom, bridging and piston means movable from a position where its end portions engage and complete the electrical circuit between said contacts to a position within said arc-extinguishing chamber, said bridging and piston means having a portion substantially filling the opening in the arc-extinguishing chamber except for one or more passages adjacent the ends thereof through which said liquid is forced to dow, and said passages being pointed in a direction generally longitudinally of the arc to cause a longitudinal low through the arc as it is drawn.

5. In a circuit breaker, a container ci arcextinguishing liquid, a pair of insulated lead-in conductors extending rinto the container, a contact on the inner end of each of said conductors, means of insulating material forming a single arc-extinguishing chamber for the arcs drawn from both of said contacts, bridging and piston means movable from a position where itsend portions engage and complete the electrical circuit between said contacts to a position within said arc-extinguishing chamber, said bridging 'and piston means having a portion substantially the same size as the opening in the arc-extinguishing chamber except for one or more passages through which liquid is forced to now into contact with the arc adjacent its end on the bridging member vand then longitudinally oi the arc.

6. 1n a circuit breaker, a container of arcextinguishing liquid, a relatively stationary contact mounted in the container and in the arcextinguishing liquid, stationary means of insulating material forming an arcextinguishing 4chamber immersed in said liquid and spaced from said relatively stationary contact only by a gap oi said liquid, said arc-extinguishing chamber being substantially closed at its end remote from said relatively stationary contact member and open -at its other end, and a contact and plunger member movable away from said relatively stationary contact to draw an arc into the chamber and having a relatively close fit with the interior of said arc-extinguishing chamber at least adjacent its substantially closed end to cause said liquid to flow toward the open end of the chamber through the arc space.

7. En a circuit breaker, a container of arcextinguishing liquid, a relatively stationary contact mounted in the container and in the arcextinguishing liquid, means of insulating material forming a stationary arc-extinguishing chamber, said relatively stationary Contact and said chamber being mounted at a distance from each other with only a clear gap in said liquid therebetween, said arc-extinguishing chamber being substantially closed at its end remote from said relatively Istationary contact member and open ai; its other end, and a contact and plunger member movable away lfrom said relatively stationary contact to draw an arc into the chamber and having a relatively close nt with the interior of said arc-extinguishing chamber to cause said liquid to flow toward the open end of the chamber through the arc space.

8. In a circuit breaker, a container of arcextinguishing liquid, a pair of relatively stationary contacts mounted in the container and in the arc-extinguishing liquid, a conducting member for bridging said relatively stationary contacts,

`ya unitary arc-extinguishing device having an open jend large enough to receive said conducting bridging member and into which the arcs drawn between the ends of said bridging member and said pair of contacts are both drawn, and said unitary arc-extinguishing device being mounted spaced from said pair of contacts so as to permit visual inspection of the point of engagement, of said bridging member with said pair of contacts without disturbing said arc-extinguishing device.

9, In a circuit breaker, a container of arcextinguishing liquid, a pair of relatively stationary contacts mounted in the container and in the arc-extinguishing liquids a conducting member for bridging said relatively stationary contacts, arcextinguishing means including a chamber large enough for movement of said bridging member therein and having an open end permitting rapid acceleration of the bridging member during the first part of its movement away from the relatively stationary contacts, and said chamber being substantially closed at its other end and having a relatively close t with said bridging member adjacent said other end for retarding movement of the bridging member and utilizing its kinetic energy to move arc-extinguishing liquid through the arc.

10. In a circuit breaker, a container of arcextinguishing liquid, a pair of relatively stationary contacts mounted in the container and in the arcextinguishing liquid, a conducting member for bridging said relatively stationary contacts, a unitary arc chamber into which said bridging member is movable, said arc chamber being substantially closed at the end toward which the bridging member moves in opening the circuit and having a relatively close fit with said bridging member adjacent said substantially closed end for causing liquid to flow in the chamber to ward the opposite end thereof to aid in extinguishing the arcs.

11. In a circuit breaker, a container of arcextinguishing liquid, a pair of relatively stationary contacts mounted in the container and in the arc-extinguishing liquid, a conducting member for bridging said relatively stationary contacts, a unitary arc chamber into which said bridging member is movable, said arc chamber being substantially closed at the end toward which the bridging member moves in opening the circuit and having a relatively close t with said bridging member adjacent said substantially closed end for causing liquid to ilow in the chamber toward the opposite end thereof to aid in extinguishing the arcs, and barrier means for conning the flow of :duid in the chamber largely to ilow adjacent the ends of the bridging member where the arcs play.

12. In a circuit breaker, a container of arcextinguishing liquid, a pair of relatively stationary contacts mounted in the container and in the arc-extinguishing liquid, a conducting member for bridging said relatively stationary contacts, a unitary arc chamber into which said bridging member is movable, said arc chamber having an elongated opening therein into which said bridging member ts substantially as a pist0n, one or more passages adjacent at least one end of the bridging member through which liquid is forced to ow through the arc in a direction opposite to the movement of the bridging member in the drawing the arc.

13. In a circuit breaker, a container of arcextinguishing liquid, a pair of relatively stationary contacts mounted in the container and in the arc-extinguishing liquid, a conducting member for bridging said relatively stationary contacts, a unitary arc chamber into which said bridging member is movable, said arc chamber having an elongated opening therein into which said bridging member ts substantially as a piston, and a narrow slot extending outwardly from each end of the chamber and into which the arcs may be moved.

14. In a circuit breaker, a container of arcextinguishing liquid, apair ofrelatively stationary contacts mounted in the container and in the arc-extinguishing liquid, a conducting member for bridging said relatively stationary contacts, a unitary arc chamber into which said bridging member is movable, said arc chamber having an elongated opening therein into which said bridging member fits substantially as a piston, and a, narrow slot extending outwardly from each end of the chamber and magnetic means for moving the arcs outwardly toward the ends of said narrow slots.

15. In a circuit breaker, a container of arcextinguishing liquid, a pair of insulated lead-in conductors extending into the container, a contact on the inner end of each of said conductors, a bridging member for completing the electrical circuit between said contacts, a single arc-extinguishing chamber having an opening through its upper end large enough to receive said bridging member, means mounting said arc-extinguishing chamber independently of and spaced from the inner end portions of said insulated lead-in conductors and the contacts thereon with its upper end below the level of the bottom of said contacts and without any solid material bridging the space between the upper end of the arc-extinguishing chamber and the inner end portions of the insulated lead-in conductors, and said single arc-extinguishing chamber being substantially closed at its sides and lower end and having a relatively close fit with said bridging member at least adjacent the lower end thereof.

BENJAMIN P. BAKER. ROBERT C. DICKINSON.

REFERENCES CITED The following references are of record in lthe le of this patent:

UNITED STATES PATENTS Number Name Date 1,940,120 Edsall Dec. 19, 1933 1,991,909 Rawlins Feb, 19I 1935 2,095,441 Howe Oct. 12, 1937 1,936,492 Whithead Nov. 21, 1933 2,111,416 Balachowsky Mar. 15, 1938 FOREIGN PATENTS Number Country Date 91,415 Swiss Nov. 1, 1921 511,364 British Aug. 17, 1939 628,547 French June 28, 1927

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