US2051196A

US2051196A - Oil circuit breaker

Info

Publication number: US2051196A
Application number: US739583A
Authority: US
Inventors: Barfoed Svend
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-08-13
Filing date: 1934-08-13
Publication date: 1936-08-18
Anticipated expiration: 1953-08-18

Description

Aug. 18, 1936. s, BARFOED 2,051,196

' OIL CIRCUIT BREAKER Original Filed Sept. 10, 1950 4 Sheets-Sheet 1 one I 7 I 38 E 37 INVEN TOR.

A TTORNEYS.

1936- s. BARFOED OIL CIRCUIT BREAKER 4 Sheets-Sheet 2 Original Filed Sept. 10, 1930 INVENTOR.

BY 1&4 vmd- CQWd/ZO ATTORNEYS.

Aug. 18, 1936. s. BARFOED OIL CIRCUIT BREAKER 4 Sheets-Shet 3 Original Filed Sept. 10, 1950 IN V EN TOR.

m2 ATTORNEYS.

S. BARFOED OIL CIRCUIT BREAKER Original Filed Sept. 10, 1930 4 Sheets-Sheet 4 fi F .5.

INVENTOR.

ATTORNEYS.

Patented Aug. 18, 1936 UNITED STATES PATENT OFFICE Substitutefor application Serial No. 480,874, September 10, 1930. This application August 13, 1984', Serial No. 739,583

10 Claims.

This invention relates to oil circuit breakers particularly intended for use in alternating current circuits, the present application being a substitute for my former application Serial Number 480,874, entitled Oil circuit breaker, filed September 10, 1930-.

There are several forms of oil circuit breakers now in use and generally the arrangement consists of a pair of stationary contacts and a pair'of movable contacts mounted to separate or close in a vertical direction through the oil.

When opening such a circuit breaker, an arc is drawn between each pair of stationary and movable contacts and an. arcs position will, at the beginning of the stroke, be nearly stationary in the path of the moving contact; the oil vaporizes and gasifies'to form a large bubble which will be inefficiently cooled since the surrounding oil must flow towards 'itfrom rest by convection; Upon further movement'of'the contacts, the electrodynamic force: of the current flowing in the arc comes more into play to move or bend out the arc to enlarge its loop. This'bending of the arc will tend to cool it chiefly in: its middle region.

Both contacts andthe ends of the" arc will still be inefliciently'sco-ured and cooled by the: oil; the

upper contact, because-it 'is stationary, and the lower or moving contact, because of cavitation pockets formedin the oil by its movement through the oil; therefore, the arc'will maintain itself a comparatively long time from the: continuedion production from the hot cc'ntactsvand from the hot gas bubble attheends of the arciwhere its position is nearly stationary with respect to'the arc. The path taken by" the contacts in passing through the oil; the amount of cavitation pro- The heat wave generated by the-pulsating power in each successive half cycle will produce, in: like manner, pulsating quantities of: gases "and vapors from the contact materials and decomposition products of the oil;

5 The object of the present invention is to generally improve and simplify the construction and operation of circuit breakers of this" character; to

provide a circuit breaker in which the contacts" canbe separated ata high rate ofspeedi; to pro-' vide contacts which present a minimum area to the path of travel through the oil so as to reduce resistance of movement to a minimumand to substantially eliminate cavitation and undue agitation of the oil; to provide a pair of contacts which 5 are pivotally mounted and movable in unison on arcs away from each other soas to pull or move the arc downwardly and horizontallythrough the oil during" the breaking operation; to. provide contacts which are divided into Widely spaced 10 pairs of main contacts and each pair having an intermediate auxiliary contact to carry the arc during the breaking operation; to provide a barrier to confine the arc between the auxiliary contacts during the breaking operation; to form 15 pockets in the barrier to contain oil in such quantities as to become instantaneously vaporized by the heat of the are as it sweeps overthe same and thereby cause a series of explosions tending to disperse or blow out the arc; and, further, to provide means for deflecting and directing oil over the faces of the auxiliary contacts and between the same to reduce burning and to break up and further quench the arc.

The circuit breaker is shown by way of illustration in the accompanying drawings, inwhich- Fig. 1 is a side elevation ofthe oil circuit breaker, said view'being partially in section and showing the switch or contact operatingmechamsm;

Fig.2 is an enlarged central vertical section of the n circuit breakerj v Fig. 3 is an enlarged central 'sectionof the barrier member, said view also showing different positions assumed by the contacts during separation thereof; I

Fig. 4 isia crosssection taken on line IVIV of Fig. 3;" I V Fig. 5 is a view similar to Fig. 3, showing the connecting links whereby'the' contact arms are actuatedyand Fig. (iis an end view of Fig. 5.

Referring to the drawings in detail and particularly Figs; 1 and 2, Aindicatesa tank or similar containerprovided witha bottom section 2 and a cover section 3. Supported by the cover section and extending therethrough are a pairof insulatingbushings such as indicated at 4 and 5 and extending through the bushings are conductor bars BandBd on the lower ends of which are '50- pivotally mounted, as at 1' and 8, contact or switch arms 9 and H]. The lower ends of the armsyse'e, Figs. 3, 4 and 6, are fork-shaped toform a pair of main contacts ll; These contacts are widely separated so that theym ay straddle" a barrier ,line position shown in Fig. 2.

member generally indicated at l2. The central and lower end of each arm is provided with a deflector plate l3. The sides of the deflector plates are carried downwardly, as shown at M, and they form bearings for a pair of auxiliary contacts generally indicated at 15 and I6. These contacts are pivoted between the bearing lugs l4 and are free to move about the pivots to a limited degree, the amount of pivotal movement being determined by stop lugs Mia. The auxiliary contacts are urged to a position where the stop lugs lea stop their movement by springs such as indicated at ll. The function of the deflecting plates l3 and the yielding action of the auxiliary contacts will hereinafter be described.

The barrier member indicated at 12 may be constructed of any suitable insulating material and it is supported with relation to the bottom section 2 by means of a pedestal insulator such as shown at 68. The barrier member in side elevation is substantially wedge-shaped. A groove I9 is formed in each side of the upper face of the barrier member and these grooves are connected by a center slot 26, the adjacent faces of which are grooved as shown at 2! to form successive superposed cylindrical pockets for the reception of oil, as will hereinafter be described. The main function of the barrier block is to confine the are formed between the auxiliary contacts during separation thereof or breaking of the circuit and it also functions to disperse or blow out the arc, as will hereinafter be described. In addition thereto, it carries a pair of contact members 22 which are engaged by the main contact arms H when a circuit is closed.

In the operation of a switch or circuit breaker of this character, it is essential that the separating action of the contacts shall be as rapid as possible. Means must accordingly be provided whereby rapid separation or opening of the contacts may be accomplished. The operating mechanism employed in the present instance is best illustrated in Figs. 1 and 2. It consists of a pair of links 25 pivotally connected at their lower ends to the respective contact arms 9 and Ill, as shown at 26, and pivotally connected at their upper ends, as shown at 21, to a plunger bar 28. The upper end of the plunger bar, see Fig. 1, is connected with a lever 29 pivoted as at 30. The opposite end of this lever is connected with a connecting rod 3! which, in turn, is pivotally connected to a crosshead 732 and a piston 34 which operates a cylinder such as shown at 35. This cylinder is provided with a pair of three-way valves such as shown at 36, which are connected with a suitable source of fluid supply through means of a pipe 31 and which is also provided with a discharge pipe 38. The source of fluidsupply is maintained at a predetermined pressure so that the speed of the piston 34 and the contact arms 9 and I0 may be determined, this being of considerable importance, as will hereinafter appear. The valves 36 are connected by common link mechanism 39 and this is in turn actuated by an operating lever M), as shown.

In actual practice it will be understood that the container A is substantially filled with oil so as to maintain the switch mechanism and the barrier member in a submerged condition. If a circuit through the breaker has been closed, the contact arms and contacts will assume the position shown in Fig. 2 and when the circuit is broken the contact arms will assume the dotted To break the circuit it is only necessary for the operator to swing the operating lever 40 from the full line position shown in Fig. 1 to the dotted line position indicated at 40c. This reverses the position of the valves 36 and as such admits the fluid under pressure to the lower side of the piston 34 and at the same time permits the fluid previously delivered to the cylinder to discharge through the upper valve 36 and the discharge pipe 38 and, as the fluid employed is maintained at a predetermined pressure, the speed of the piston and the mechanism actuated thereby can be determined. The operating mechanism of course performs only one function, to wit, that of separating or closing the contacts.

Since the circuit breaker here illustrated is particularly intended for alternating current circuits, it is to be remembered that the power of a single phase supply is pulsating due to the sinusoidal variation in current and voltage with respect to time; and for explanation unity of power factor will be assumed. In the present instance, the time required to swing the contacts from closed position to full open or separated position is known and for the purpose of de scription it will be assumed that while the contacts sweep over the barrier member I2, six half cycles or impulses take place. Five of these pockets are illustrated, see Figs. 3 and 4. The are produced during separation of the contacts is, in the present instance, confined between the auxiliary contacts I 5 and I6 by means of the barrier block l2, and as these contacts align with the slots 19 and the slot 20 having the enlarged pockets 2| formed therein, the arc must pass therethrough. During movement of the contacts and as the half cycle pulsations occur, maximum current flow takes place at a frequency that causes arcing through the several pockets 2! successively. The body of oil confined in these pockets is comparatively small and the current flow and heat produced by the are are so great that the oil contained in the respective pockets is vaporized with such rapidity as to expand with explosive action, hence tending to disperse or blow out the arc. The oil pockets 2| become longer and longer as the contacts sweep downwardly over the barrier and as each body of oil explodes it tends to disperse or blow out the ionized decomposition products as the current decreases to zero, making it more and more difiicult for the current to reestablish the are as the current flow again reaches maximum during each half cycle of flow.

The dispersing or blowing out action of the arc just described is not the only action depended upon to quench the arc. For instance, by referring to Fig. 3, it will be noted that the deflecting plates [3 are provided. These will, during the downward and outward sweep of the contact arms, function as nozzles and discharge oil under high velocity downwardly over the faces of the auxiliary contacts and between the same in the direction of the arrows indicated at a. The high velocity of the oil is obtained by the rapid motion of the contact arms in an outward direction and the oil thus delivered over the faces of the auxiliary contacts and between the same is depended upon to reduce any burning action and the formation of vapors which would tend to sustain the arc. In the present structure the current contacting leads passing through the insulators 4 and 5 and the arms 9 and I0 form a loop in which current flows. Such a loop is subject to an electrodynamic force tending to enlarge it on 75..

the well: known". principle. of: electromagnetism.-. When the contact arms separatmandzthea arc:isx struck, the. same. el'ectrodynamic; force! isalso active onv the arc: duegto the. current.flowing through it;and.the.:arc:iszthereby enlarged; curved:

and;pro.pelled in a downward-direction, asrindie catedbythe dotted-lineb..- This is another-reason;

for directing. the oilijetsin the directionlofi arrows a, see Eig: 3;.asthe oil so: directed. is pro.- jected'with high velocity against theaarc formed: between the. contact. membersand in the same direction as the electrodynamic force relative to the are, .thus tending to .furtherenlarge: and expand-.the arc-to.causedisruptionthereof.

Also.=it. should-be notedthat the contactarm sweep. downwardly. and" outwardly about the pivots l and 8-. Thisisalso.importantias-zit"rapidly. increasesthespacing between the contacts,

thereby lengtheningethe arc, and asthma contactsv atthesametime move'downwardly, there is a tendency to. pullithearc into a body of fresh cool oil, this .action being exceedingly-important as it.

rapidly. cools the are core and, furthermore, interposes a larger and larger: body of oil; thexresistance.ofiwhichsoonbecomes too great for the arc to penetrate.

Another important feature to be considered is the forking of the main contact arms at their lower ends to form a pair of main contacts I I on each arm. These contacts are widely separated and are disposed on opposite sides of the barrier member I2. These contacts, when in engagement with the stationary contact blocks 22, carry the main current flow when a circuit is established. They are held in engagement with the contact blocks 22 with pressure due to the upward pull on the links 25. When the contact arms are brought together to close the circuit, the auxiliary con tacts first engage and, as they are pivotally and yieldingly supported between the bearing lugs M by means of the springs I'I, they will give until the main contacts ll engage the contact blocks 22. During separation of the contacts when breaking the circuit, the main contacts II will leave the contacts 22 and will move a considerable distance before the auxiliary contacts [5 and i6 are disengaged, as they will be held in engagement with relation to each other by the springs I! until the stop lugs l6 prevent further movement. At that point they separate and as they have been carrying the current flow during the preliminary separation of the main contacts, the arc is established between the auxiliary contacts, hence preventing arc formation between the main contacts. Burning action, if any, will accordingly take place between the auxiliary contacts, leaving the main contacts unaffected. Another important feature to be considered is the fact that the main contacts present a comparatively small area when passing through the oil, as they are substantially knife-like in formation, hence cutting through the oil during the rapid movement of the contact arms without producing any material agitation or cavitation in the oil. This is obviously desirable as it is cavitation more than anything else that tends to continue arcing.

While certain features of the present invention are more or less specifically described, I wish it understood that various changes may be resorted to within the scope of the appended claims. Similarly, that the materials and finishes of the several parts employed may be such as the manufacturer may decide, or varying conditions or uses may demand.

' Having: described: my inventiom. what. I claim and desire: to) securerbya Letters Patent is-" 1-. In; a; circuitzbreakeri of? the character described, a. container: for: oil, azpair ofi pivotally' mounted arms submerged: in the oil, apair of spaced; maini contacts on each: 'arm, an auxiliary contact on. each arm and disposed between the main contacts, means for imparting movement to the arms about their: pivots toseparate: the contacts; means whereby. the auxiliary contacts are. maintained: in engagement until a substantial separation betweenv the main. contacts: has takenplace; and apain of barrier:plates":disposed" in. the container in-Ja position. where the 1 main contacts willmove parallellto the said plates while the auxiliary contacts will move along the'edgesof the plates and the are formed during the separatiomofithe auxiliary contacts will be confined between the: plates and the auxiliary contacts 2..In a-= circuit breaker: of thecharacten described, a: container for oil, a pair: of pivotally' mounted arms submerged inthe: oil, a pair of spaced main contacts on eacharm, an auxiliary contact on each arm and disposed between the" mainv contacts, means forimparting movement to the arms about their pivots to separate the contacts, means whereby the auxiliary contacts are maintained in engagement until a substantial separation between the main contacts has taken place, a pair of barrier plates disposed in the container in a position where the main contacts will move parallel to the said plates while the auxiliary contacts will move along the edges of the plates and the are formed during the separation of the auxiliary contacts will be confined between the plates and the auxiliary contacts, and means for directing oil under high velocity between the faces of the auxiliary contacts and downwardly between the barrier plates.

3. In a circuit breaker of the character described, a pair of movable contacts, a barrier member cooperating therewith, said member comprising a pair of plates constructed of insulating material spaced to form a slot for the reception of oil and the adjacent faces of the plates having spaced grooves formed therein forming successively disposed enlarged bodies of oil, and means for moving the contacts at opposite ends of the slot and exteriorly thereof sothat the are only will pass through the slot.

4. In a circuit breaker of the character described, a pair of contact members, means for moving the contact members from a closed to an open position, and a barrier interposed between the paths of movement of said contact members, said barrier being constructed of insulating material and having elongated pockets extending through it in a position to align one at a time with said contact members as they traverse their path of movement, said pockets progressing in length toward the full open position of the contact members.

5. In a circuit breaker of the character described, a pair of contact members, means for moving the contact members from a closed to an open position, and a barrier interposed between the paths of movement of said contact members, said barrier being constructed of insulating material and having elongated pockets extending through it in a position to align one at a time with said contact members as they traverse their path of movement, said pockets decreasing in cross sectional area toward the full open position of the contact members.

6. In a circuit breaker, a pair of plates constructed of insulating material and spaced to form a slot, a pair of contact members, and movable exterior of said plates from a closed to an open position in the plane of said slot and at opposite ends of said slot whereby the arc formed between said contact members will pass through the slot. g

7. In a circuit breaker, a pair of plates constructed of insulating material and spaced to form a slot, 2. pair of contact members, movable exterior of said plates from a closed to an open position in the plane of said slot and at opposite ends of said slot whereby the are formed between said contact members will pass through the slot, and means for directing a flow of oil through the arc.

'8. In a circuit breaker, a pair of plates constructed of insulating material and spaced to form a slot, a pair of contact members, means to move said contact members from a closed to an open position in the plane of said slot and at opposite ends of said slot whereby the are formed between said contact members will pass through the slot,,and means actuated by movement of the contact members for directing a flow of oil transversely through the are.

9. In a circuit breaker of the character described, a container for oil, a pair of arms each having a contact member at one end, said arms being pivoted at their other ends so that when a circuit is broken the contact ends of the arms will swing away from each other in the plane of the electrodynamic force produced in the loop of the arc which is formed during the breaking of the circuit, and means for directing a flow of oil into the arc and transversely thereof between the contacts in the same direction as the electrodynamic force to control and quench the arc.

10. In a circuit breaker, a pair of plates constructed of insulating material and spaced to form a slot, a pair of contact members movable exterior of said plates from a closed to an open position in the plane of said slot and at opposite ends of said slot whereby the are formed between the contact members will pass through the slot, and means for maintaining the movable contact members and the spaced plates submerged in a liquid arc quenching medium.

SVEND BARFOED.