US2748227A

US2748227A - Electric circuit breakers

Info

Publication number: US2748227A
Application number: US315315A
Authority: US
Inventors: Caton George
Original assignee: Yorkshire Switchgear and Engineering Co Ltd
Current assignee: Yorkshire Switchgear and Engineering Co Ltd
Priority date: 1951-06-27
Filing date: 1952-10-17
Publication date: 1956-05-29
Anticipated expiration: 1973-05-29

Description

May 29, 1956 G. CATON ELECTRIC CIRCUIT BREAKERS 2 Sheets-Sheet 1 Filed Oct. 17-, 1952 May 29, 1956 Filed Oct. 17, 1952 G. CATON ELECTRIC CIRCUIT BREAKERS 2 Sheets-Sheet 2 ice ELECTRIC CIRCUIT BREAKERS George Caton, Leeds, England, assignor of one-half to Yorkshire Switchgear & Engineering Company Lint sit. Leeds, England, a British company Application October 17, 1952, Serial No. 315,315

7 Claims. (Cl. 200-=-=-150) This invention relates to electric circuit breakers of the type incorporating arc-control devices for extinguishing the arc between the contacts.

It is particularly concerned with improvements in oilimmerscd electric circuit breakers of the kind including a pair of fixed contacts and a movable bridging contact cooperating with said fixed contacts to make and break a circuit and having an arc-quenching chamber in an insulating carrier structure associated for movement with the bridging contact, said arc-quenching chamber extending between spaced arcing points provided by arcing contacts cooperating within the chamber and having at least one restricted outlet passage arranged so that under pressure of gas generated by arcing within the chamber, a stream of oil under pressure is directed across the arcing path at at least one arcing point.

The invention is of particular application to such electric circuit breakers in which arcing electrodes are arranged to break the circuit after the main contacts so that arcing is confined to arcing contacts disposed within the arc-quenching chamber.

It has before been proposed in an electric circuit breaker of the kind referred to having arcing electrodes connected to the main fixed contacts and arranged to coact with arcing contacts within the arc-quenching chamber, to form the carrier structure of rectangular section comprising two side walls of insulating material and a central insulating partition arranged to provide parallel arcquenching compartments, the carrier structure being closed at the top by a wall member extending across the top of the carrier structure in a plane at right angles to the plane of movement of the carrier structure, and at the bottom by members arranged between the side walls and the partition, each compartment housing a pair of arcing contacts for cooperation with arcing electrodes associated with the main fixed contacts, and the outlet from one compartment being at the opposite end of the carrier to the outlet from the other compartment, one end of each compartment being closed by an insulating block and the other end by spaced bafiie plates. In this proposal, however, not only is the said top wall member disposed in a plane at right angles to the plane of movement of the carrier structure, but the main bridging contact is inset into the top wall of the carrier structure and provides an exposed conducting surface within the arc-quenching chamber intermediate the arcing electrodes and thus provides an alternative path for arcing within the chamber at a position Where the arc would not be subject to the quenching action of the oil, stream.

The present invention has for its object to provide an improved construction of oil-immersed electric circuit breaker whereby the thickness of the insulating carrier structure, in the dimension at right angles to its plane of movement may be reduced to a minimum to facilitate quick action of the circuit breaker, while at the same time providing a structure which is highly resistant to bursting stresses and in which, not only is the danger of possible arcing across between the stationary contacts,'or

other than at the arcing points, obviated, but a more efiicient and certain arc-quenching action is obtainable.

The term oil used herein includes any other liquid suitable for arc-quenching purposes.

According to the present invention, there is provided an oil-immersed electric circuit breaker including a pair of fixed contacts and a movable bridging contact cooperating with said fixed contacts to make and break a circuit and having an arc-quenching chamber in an insulating carrier structure associated for movement with the bridging contact, said arc-quenching chamber extending between spaced arcing points provided by cooperating arcing contacts within the chamber and having at least one restricted outlet passage arranged so that under pressure of gas generated by arcing within the chamber, a stream of oil under pressure is directed across the arcing path at at least one of the arcing points, and the arc-quenching chamber being formed within an assemblage of insulating plate members, the planes of which are disposed in the plane of movement of the carrier. The assemblage of insulating plate members is so constructed as to provide continuous insulating interior Wall surfaces extending between the fixed arcing contacts when disposed within the chamber so that no metal surface, which would allow the arcing current to take an alternative path other than through the arcing points, is exposed within the chamber.

More specifically, the invention includes an oil-immersed electric circuit breaker including a pair of main fixed contacts, a movable carrier structure provided with main bridging contact means to cooperate with said fixed contacts, an arc-quenching chamber in the carrier structure, arcing electrodes connected to said fixed contacts to extend into said chamber to coact with arcing contacts in said chamber connected to said main bridging contact means and providing spaced arcing points in said chamber, said arcing electrodes being arranged to break contact with the arcing contacts after the main contacts have broken, and said chamber having at least one outlet passage for discharge of oil across the arcing path at one arcing point under pressure of gas generated by areing at the other arcing point, the arc-quenching chamber being formed within an assemblage of insulating plate members, the planes of which are disposed in the plane of movement of the carrier, the insulating assemblage providing continuous insulating interior wall surfaces extending between said arcing electrodes. The arc-quenching chamber may be divided by transverse bafiie means into two compartments communicating through a restricted passage disposed substantially opposite to said outlet passage, the compartment of the chamber between the restricted passage and the outlet passage being smaller than the other compartment and housing one of said arcing contacts. By such an arrangement, flow of oil under pressure from the larger compartment, due to gas pressure generated at the arcing point in said larger compartment, is directed through the restricted passage across the arcing path in the smaller compartment to said outlet passage with increased velocity.

An additional outlet passage may communicate with said restricted passage at a point further from the arcing contact than said first-mentioned outlet passage. A third outlet passage may intersect an opening in the assemblage for the electrode coacting with the arcing contact in the larger compartment of the chamber.

The bridging contact means may comprise conductive plates applied at opposite sides of the assemblage of insulating plate members and serving as reinforcement therefor.

Preferably one of the arcing contacts is adapted to break contact before the other and the arcing electrodes preferably also are of relatively small cross-sectional Patented May 29, 1956 area as compared with the main contacts so as to reduce the siZe of the arc and facilitate the arc-quenching action.

The circuit breaker may include intermediate transfer contacts associated with the main contacts adapted to make before and break after the main contacts.

The invention is hereinafter described, by way of ample, with reference to the accompanying diagrammatic drawings, in which:

Fig. 1 is an elevation illustrating one embodiment of electric circuit breaker according to the invention, showing the main fixed contacts engaged by the main bridging contact means on the movable carrier structure;

Fig. 2 is a cross-section on the line 11-11, Fig. l, the section being taken in part through main contacts and in part through transfer contacts as indicated in Fig. 1;

Fig. 3 is a vertical cross-sectional on line 33 of Fig. 1.

Fig. 4 is a view similar to Fig. l, but with the carrier structure moved downwards to the position where the main contacts have broken and the transfer contacts still complete the circuit through the main bridging contact means;

Fig. 5 is a longitudinal section through the movable carrier, showing arcing commencing at one arcing electrode;

Fig. 6 is a view similar to Fig. 5, but showing arcing occurring at both electrodes; and

Fig. 7 is a similar view showing the circuit clear after the arc-quenching operation and the carrier moved to a position to open a relief passage.

In carrying the invention into effect according to one embodiment, and with reference to the accompanying diagrammatic drawings, the invention is shown as applied to an oil-immersed electric circuit breaker of the conventional type having two terminals 1 and 2 for each phase. Foot members 4 carried by the terminals provide mounting for main fixed contacts 3 adapted to be engaged by main bridging contact means comprising con

ductive plates

17, 18 on a movable carrier structure. Each main contact assembly may be of any suitable conventional construction and conveniently may comprise pairs of resiliently mounted fingers spaced apart to engage the

conductive plates

17, 18 on the carrier structure. Any number of main contact fingers may be provided according to the rated load capacity of the circuit breaker, and transfer contacts 7 may be arranged to make before and break after the main contacts 3 in known manner so as to transfer the circuit from the main contacts 3 to the contacts 7 before the current is transferred to arcing contacts comprising arcing electrodes 19, 21) arranged to cooperate with arcing contacts 27 connected to the main bridging contact means, i. e. the

plates

17, 18, the

arcing electrodes

19, 20 being carried by the foot members 4 and being of small cross-sectional area and narrow width, as indicated in Fig. 2 so as to reduce the size of arc and facilitate the arc-quenching operation.

The arcing contacts 27 are arranged so that arcing points between said contacts and the electrodes 19, are disposed in known manner within an arc-quenching chamber provided in the carrier structure and communicating with at least one outlet passage, such as 23, so that under pressure of gas generated at the arcing point between the electrode 19 and the respective contact 27, oil under pressure is directed across the arcing path between the electrode 20 and the corresponding arcing contact 27.

According to the invention, the arc-quenching chamber 21 is formed within an assemblage of insulating plate members disposed in the plane of movement of the carrier and providing continuous insulating interior wall surfaces extending between the fixed arcing electrodes 1 20 when disposed within the chamber. Thus, as shown in the drawings, the carrier comprises a central insulating plate member 16 which is cut through transversely to form the arc-quenching chamber, as shown more clearly in Fig. 3, and insulating plate members 16a closing opposite sides of the apertured member 16 and forming the side walls of the arc-quenching chamber. Thus it will now be apparent that the entire interior surface areas of the

plate members

16 and 16a which define the are quenching chamber are insulative in character. That is to say, except for the

arcing electrodes

19, 20 which enter the chamber and the stationary arcing contacts 27 within the chamber there are no other metallic, conductive surfaces exposed to the interior of the chamber which might result in the establishment of an are between the contacts 27. The arcing contacts 27, which are spring-loaded, are carried by removable plates 31 secured by

bolts

16b, 16c to the

conductive plates

17, 18 and project into the chamber through apertures in the insulating plate members 16a. Bolts 16b located out side of the boundaries of the arcing chamber 21 also extend through the assemblage of

insulating plates

16, 16a, and the

conductive plates

17, 18. Bolts 16c located within such boundaries terminate short of the interior face of the insulating plates 16a.

it is preferred that one arcing electrode, i. e. the electrode 19, should break contact before the other, as shown in the drawings, although this is not essential as, in any case, an arc will be formed at the electrode 1?, in addition to an are at the electrode 20, for creating gas pressure whereby cool oil in the arc-quenching chamber will be forced under pressure through an outlet passage 28 and thus across the arcing path at the other electrode 21). If, however, an arc is formed at the electrode 19 in advance of the are at the electrode 20, this facilitates build-up of pressure for quenching of the are at the electrode 24) at an early stage.

The arc-quenching chamber 21 is divided by transverse bafiie means 16d into two

compartments

23, 26 communicating through a restricted passage 24 disposed adjacent the electrode opening 25 for the electrode 20 and substantially opposite to the outlet passage 28. The compartment 26 between the restricted passage 24 and the outlet passage 28 is relatively small and provides a confined space housing the arcing contact 27 coacting with the arcing electrode 20. By this arrangement, gas pressure created by arcing at the electrode 19 is applied in the most effective manner for directing a high velocity stream of cool oil through the restricted passage 24 and across the arcing path at the electrode 20 at the best position for quenching the arc. Furthermore, owing to the fact that the arcing contacts are thus located in separate compartments communicating only through a restricted passage, and to the fact that all interior wall surfaces intermediate the arcing electrodes are of insulative material,-any possibility of arcing across between the

electrodes

19, 26 through the chamber 21 is obviated.

As an additional safeguard to ensure quenching of the arcing at the electrode 20, an additional outlet passage 29 communicates with the restricted passage 24 at a point further from the respective arcing contact 27 than said first-mentioned outlet passage 28. A third outlet or relief passage 31) communicating with the chamber 21 intersects the opening 22 for the electrode 19 so as to open when the carrier is moved to the position shown in Fig. 7 to permit rapid relief of internal pressure after the arc has been quenched. The passage 30 also functions as a safeguard for independent quenching of an are at the electrode 19 if the circuit has not been cleared by quenching of the are at the electrode 20.

The

electrodes

19, 20, may be of round, rectangular,

or other cross-sectional shape.

It is known to use an insulating material which reacts to arcing and produces a (lo-ionising gas, and the insulating carrier structure according to the invention may be built up of such insulating material so that the de-ionising gas generated will assist the arc-quenching action.

What I claim is:

1. An oil immersed electric circuit breaker including a pair of fixed contacts and a movable bridging contact cooperating with said fixed contacts to make and break a circuit, an arc quenching chamber in an insulating carrier structure associated with the bridging contact, said chamber extending between spaced arcing points provided by contacts cooperating Within the chamber, said are quenching chamber having at least one restricted outlet passage arranged so that under pressure of gas generated by arcing at one arcing point a stream of oil under pressure is directed across the arcing path at the other arcing point, said are quenching chamber formed within an assemblage of plate members disposed in the plane of movement of the carrier the interior surface areas of said plate members forming the entire walls of said chamber being of insulative material thereby providing continuous insulating interior surfaces extend along all walls of said chamber between the fixed arcing contacts when disposed within the chamber.

2. An oil-immersed electric circuit breaker including a pair of main fixed contacts, a movable carrier structure provided with main bridging contact means to cooperate with said fixed contacts, an arc-quenching chamber in the carrier structure, arcing electrodes connected to said fixed contacts to extend into said chamber to coact with arcing contacts in said chamber connected to said main bridging contact means and providing spaced arcing points in said chamber, said arcing electrodes being arranged to break contact with the arcing contacts after the main contacts have broken, said chamber having at least one outlet passage for discharge of oil across the arcing path at one arcing point under pressure of gas generated by arcing at the other arcing point, and said chamber being formed within an assemblage of plate members disposed in the plane of movement of said carrier structure, the interior surface areas of said plate members forming the entire walls of said chamber being of insulative material thereby providing continuous insulating interior surfaces extending along all walls of said chamber between said fixed arcing contacts in said chamber.

3. An oil-immersed electric circuit breaker according to claim 2, wherein said arc-quenching chamber is divided by a baffie into a larger compartment and a smaller compartment, said smaller compartment housing and substantially isolating one of said arcing contacts, and said compartments communicating with each other through a restricted passage disposed opposite an outlet near the top of said smaller compartment whereby, upon an occurrcnce of arcing in said larger compartment, oil at high velocity is directed in a confined stream across the arcing point in said smaller compartment.

4. An oil-immersed electric circuit breaker according to claim 3, wherein said arc-quenching chamber includes an additional outlet passage communicating with said restricted passage at a point further from the arcing contact than said first-mentioned outlet passage.

5. An oil-immersed electric circuit breaker according to claim 4, wherein said arc-quenching chamber includes a third outlet passage intersecting an opening in said assemblage for the electrode coacting with the arcing contact in the main part of the chamber.

6. An oil-immersed electric circuit breaker according to claim 2, wherein said main bridging contact means comprises conductive plates applied at opposite sides of said assemblage of insulating plate members and serving as reinforcement therefor.

7. An oil-immersed electric circuit breaker according to claim 2 and which further includes intermediate transfer contacts associated with said main contacts and adapted to make before and break after said main contacts.

References Cited in the file of this patent UNITED STATES PATENTS 1,805,497 Paul May 19, 1931 1,934,454 Spurgeon Nov. 7, 1933 1,949,258 Paul Feb. 27, 1934 2,156,450 Cole May 2, 1939 2,419,106 Baker et a1. Apr. 15, 1947 FOREIGN PATENTS 413,751 Great Britain July 26, 1934 661,181 Germany June 13, 1938