US2147497A - Electric circuit interrupter - Google Patents

Description

Feb. 14, 1939. o. c. PRINCE ET AL ELECTRIC CIRCUIT INTERRUPTER Filed Nov. 11, 1937 e 9 ..c% m Smim MP FPt O mmw ,mwm D m Patented Feb. 14, 1939 PATENT OFFICE ELECTRIC cracm'r INTERRUP'I'ER David 0. Prince, Swarthmore, and Percy Bartlett, Springfield, Pa., assignors to General Electric Company, a corporation of New York Application November 11, 1937, Serial No. 174,066

8 Claims.

Our invention relates to electric circuit interruptersfor high voltage power circuits, more particularly to circuit breakers of the impulse type wherein a piston or the equivalent thereof is utilized to project arc-extinguishing liquid through the arc to be interrupted.

Power breakers of the above type have been proposed wherein the arc pressure tending to oppose or block normal operation of the piston is compensated to a certain degree by admitting arc pressure to the opposite side of the piston. While improving the breaker operation, certain diihculties including uncertain interruption at low current values when the arc pressure is very low and improper utilization of the arc pressure are still present.

A principal object of our invention is the provision of an improved circuit breaker oi the. im-

pulsetype that is simple and compact in design, and eflicient, rapid and positive in its interrupting operation throughout the entire range of current rating.

Our invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing the 1 single figure thereof is an elevational view, partly in section,

of an electric circuit breaker embodying our invention.

The circuit interrupter illustrated by way of example comprises a main housing or casing l adapted to contain a suitable arc-extinguishing liquid such as oil. Immersed in the arc-extinguishing liquid is an arc interrupting device generally indicated at 2 supported at the lower wall of the housing by an insulator 3. The arc-extinguishing device includes a conducting or fixed contact structure 4 supported in part by a second insulator 5 serving as the lead-in terminal conductor bushing between the fixed contact structure 4 and the exterior circuit. The other terminal of the breaker includes a contact 6 suitably mounted withrespect to an insulator i that i also serves as a lead-in terminal conductor bushing in the wall of the housing I.

The movable contact structure associated with the arc-interrupting device 2 comprises a contact rod 8 adapted to make sliding contact with .the contact 6 and suitablyguided for reciprocal rectilinear movement. The means for effecting movement of the rod contact 8 comprises a linkage mounted within a spherical extension 9 of the main housing, the extension being attached to the housing through an intermediate cylindrical member l0.

The interrupting device 2 including the fixed contact structure 4 is provided with a cylindrical portion H open at its opposite ends. A piston I2 is mounted for reciprocal movement within the cylinder and is attached through an insulating rod l3 to the linkage above referred to in the spherical extension 9. The upper end of the arcinterrupting device 2 is closed by a pair of spaced insulating plates I4 and I5 through which the contact rod 8 is moved in alined apertures 16 to engage the relatively fixed contact structure. The spacing between the plates l4 and I5 forms 7 a lateral passage ii that communicates at one rod 8, there is provided an intermediate floating contact l9 disposed between the fixed contact structure 4 and the rod contact 8 arranged so that two arcs are formed in series when the complete contact structure is separated. The intermediate contact i9 is mounted in and supported by an insulating partition 20 forming with the conducting structure 4 pressure chambers 2| and 2| in communication with the lower and upper faces respectively of the piston l2. A vent 20" of suitable bore and location in the partition 20 permits the piston [2 to descend during the closing or resetting stroke. During this movement the chamber 2| is scavenged of residual gases resulting from the preceding arc interruption.

The contact separation within the chamber 2| takes place between the arcing tips 4' of the fixed contact and IQ of the intermediate contact. A spring 22 seated at the opposite side of the partition 20 tends to bias the intermediate contact away from engagement with the contact tip 4'. The intermediate contact is also provided with arcing tip IQ" for coacting with the rod contact 8 which is illustrated in alinement therewith through the apertures I5. Accordingly, it will be noted that when the rod contact 8 is lowered to close the circuit between the terminals 5 and I, the intermediate contact will The circuit is then comscribed, the contact tips d and it first separating due to the following movement of the intervelocity transversely of the arcwithin the pasmediate contact I9 under the influence of spring 22. When the intermediate contact reaches its upper limit of travel, as illustrated, separation of the rod contact-3 and contact tip it" takes place resulting in a second break in the circuit. This second break is in the transverse passage ill through which oil is driven by the piston i2 in a manner presently to be described for interrupting the arc.

The operating linkage previously referred to in the housing extension 9 is arranged to cause simultaneously both opening movement of the rod contact 8 and an upward wormng stroke of the piston I2. By way of explanation the draw-' ing illustrates the mechanism in the process of being closed, piston l2 being first depressed and, the rod contact 8 then lowered to engage the contact structure within the arc-interrupting de-' vice.

When the breaker is opened, pressure generated by the are formed between the contact tips 4' and [9' in the pressure chamber 2i acts on the lower side of the piston l2 tending to assist the upwardly pulled piston in driving 'a stream of oil through the passage l1 transversely of the are subsequently formed at the contact 8. In the case of arc currents of appreciable magnitude, this operation'is very effective and the piston propelled by both mechanical and arc-gem, erated pressures drives a blast of oil at high sage il.

During the interruption of low currents, however, the generated arc pressure maybe ,of quite a low value or slow in forming. Hence au-retardation of the piston would ensue because of i s tendency to produce a vacuum or negative pressure on its under side di'iring its upward travel.

' This would lessen the zintensity nf an early and decisive oil blast through the passage it. For the purpose of eliminating-this hazard a nonreturn valve -23 is provided for the chamber 25 arranged so that oil is drawn into the chamber from the main housing i when the piston it tends to create a vacuum in the chamber due to insufiicient arc pressure. The valve 23 obviously remains closed when the arc pressure is sufiicient to aid the piston i2. That is, the pressure chamher it is provided with valve means arranged to close the chamber when the arc pressure therein has or exceeds a predetermined value, and also ar= ranged to open the chamber when said pressure is less than said predetermined value.

Accordingly, the piston is efiectiv'e throughout the entire range of current rating to project an effective oil blast through the main are within the passage ii. In the caseof heavy current arcs, it will be noted that the piston E2, in mov-- ing to the dotted line position shown, establishes a wide communication between chambers Zi2i' to form a common pressure region. He-

terrupting device.

ber within which one of said break areas-er pendently to the best-advantage as current conditions may dictate.

The operating linkage for the contact rod d and the piston 12 above referred to may comprise any suitable arrangement for effecting quick separation of the contacts and a positive stroke of the piston. In the present instance, there is shown a main operating shaft 241 transversely pivotally connected to a link 30 near the midportion thereof, the link 30 also being pivotally connected at 38 to the upper end of the contact rod 8.

The lever 27 is also pivotally connected to a floating lever 32 that is in turn loosely connected to the insulating rod I3 of the pistbn 52. A pin 33 at one end of the link 30 operates in a slot 32' in the floatin'g lever 32, the movement of the opposite end of the floating lever being controlled in one direction by an abutment 36. v

The linkage is shown in a partially closed position in which the operating shaft 2% has been rotated counter-clockwise towards the circuit closing position so as to extend or charge the spring 35. The spring in this position biases thepiston l2 through the insulating rod is in an upward or blast-producing direction. Further clockwise rotation of the shaft 25 will cause the lever 2'8 to rotate the'link 28 also in a counterclockwise direction thereby rotating the link 36 clockwise and moving the contact rod 8 downward into contact engagement within the arc-in- This operation also will extend the biasing spring 36 tending to move the contact rod 8 in a circuit-opening direction.

rotated to a point so that the crank arm 25 and link 26 are slightly overset so as to hold the breaker in the circuit-closing position. In the circuit-opening operation the shaft 2% is rotated in a clockwise direction so that the linkage will N be released and the springs 35 and 36 are effective to cause simultaneous movement or the con tact rod 8 and piston i2 upward, thereby causing separation of the breaker contacts and extin guishing of the arc.

It should be understood that our invention is not Limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing iron; the spirit of our invention.

What we claim as new'and desire to secure by Letters Patent of the United States; is:

1. ,An electric circuit breaker of the impulse type comprising an arc-extinguishing liquid, relatively movable contact structure adapted to form two breaks in series in said liquid upon opening of the circuit, means defining a pr ssure chamis formed,

. tween said chamber and said passage arranged a piston communicating with said chamber and arranged to project arc-extinguishing liquid through the are at said other break, means for actuating said piston independently of said are pressure, and means for compensating low arc pressure in said chamber when said piston tends to create a negative pressure therein.

2. An electric circuit breaker oi the impulse type comprising an arc-extinguishing liquid, relatively movable contact structure adapted to form two breaks in series in said liquid upon opening of the circuit, means defining a pressure chamber within which one of said breaks is formed and a transverse passage within which the other of said breaks is formed, a piston interposed beso that arc pressure in said chamber tends to move said piston in a direction to cause a blast *ber and arranged to project arc-extinguishing oi arc-extinguishing liquid through said passage for interrupting the are at said other, break, means for actuating said piston independently of said are pressure, and a valve associated with said chamber for compensating low arc pressure therein whensaid piston tends to' create a negative pressure'in said chamber.

3'. An electric circuit breaker of the impulse type comprising an arc-extinguishing liquid, relatively movable contact structure including a fixed contact, an intermediate contact and a main movable contact adapted to form two breaks in series in said liquid upon opening of the circuit, means defining a pressure chamber within which thebreak between said fixed and intermediate contacts is formed, said intermediate contact coacting with said main movable contact exteriorly of said chamber, a piston communicating with said chamliquid through the arc at the break between said intermediate and main movable contacts, the

arc pressure in said chambertending to aid said projection of arc-extinguishing liquid through said other are, means for actuating said piston independently of said are pressure, and valve means controlling a port in said chamber arranged to close said chamber in the case of heavy current interruptions whereby said piston is assisted by the resulting arc pressure.

4. An electric circuit breaker of the impulse type comprising an arc-extinguishing liquid, an arc-interrupting device immersed. in said liquid having a pressure chamber and a transverse exhaust passage, a fixed contact disposed in said chamber, a floating contact coacting therewith and extending through a wall of said-chamber, a movable contact coactingwith said floating contact exteriorly of said chamber in said exhaust passage, a piston interposed between said chamber and passage arranged so that are pressure. formed in said chamber between said fixed and floating contacts tends to drive arc-extinguishing liquid through said passage and transversely of the are between said floating and movable contacts, means for actuating said piston independently of said are pressure, and means associated with said chamber for compensating low arc pressure in said chamber when said piston tends to create negative pressure therein.

5 An electric circuit breaker or theimpulse type comprising an arc-extinguishing liquid, relativeiy movable contact structure including a fixed a the break between said fixed and intermediate contacts is formed, a non-return valve associated with said pressure chamber, said intermediate contact coacting with said main movable contact exteriorly of said chamber, a piston communicating with said chamber and arrangedto project arc-extinguishing liquid through the are at the break between said intermediate and main movable contacts, the arc pressure in said chamber tending to aid said projection of arc-extinguishing liquid through said other are, and means for actuating said piston independently of said arc pressure.

6. An electric circuit breaker oi the impulse type comprising an arc-extinguishing liquid, relatively movable contact structure adapted to form two breaks in series upon opening of the circuit, means defining a pressure chamber within which one of said breaks is formed in said liquid, a piston communicating with said chamber and arranged toproject arc-extinguishing liquid through the arc at said other break, means for actuating said piston independently of the arc pressure in said chamber, and means for openingsaid chamber to said liquid and adapted to form two breaks in series upon opening of the circuit, means defining a pressure chamber within which one of said breaks is formed, means forming an interrupting chamber within which the other of said breaks is formed, a piston communicating with both chambers and arranged to project arc-extinguishing liquid through the arc in said interrupting chamber, the arc pressure in said pressure chamber tending to aid said projection of arc-extinguishing liquid, means ior actuating said piston independently of said are pressure, and valve means coactmg with said pressure chamber arranged to be closed when said are pressure has or exceeds a predetermined value, and arranged to be opened when said are pressure is less than said predetermined value.

8. An electric circuit breaker oi the impulse "type comprising'an arc-extinguishing liquid, relatively movable contact structure adapted to term two breaks in series upon opening of the circuit, means defining a pressure chamber within which one oi said breaks is formed in said liquid, at piston communicating with said chamber and arranged to project arc-extinguishing liquid through the are at said other break, actuating means for eflecting a working stroke of said piston, and valve means controlling a port in said chamber communicating with a region ebrt'eriorly thereof, i

mm c. memos.

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