US2284684A

US2284684A - Electric circuit breaker

Info

Publication number: US2284684A
Application number: US370818A
Authority: US
Inventors: David C Prince
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1940-12-19
Filing date: 1940-12-19
Publication date: 1942-06-02
Anticipated expiration: 1959-06-02
Also published as: GB550301A

Description

June 2, 1942. D. c. PRINCE 2,284,634

ELECTRIC CIRCUIT BREAKER Filed Dec. 19, 1940 Inventor David C. Prince,

by JV 6.)

His Attorney.

Patented June 2, 1942 ELECTRIC omcm'r BREAKER David CQPrince Schenectady, N. Y., asslgnor to General Electric Company, a. corporation of New York Application December 19, 1940, Serial No. 370,818

Claims.

My invention relates to electric circuit breakers, more particularly to circuit breakers of the fluid blast type wherein fluid such as gas under pressure is directed through the are for interrupting it, and has for its principal object the provision of improved fluid blast circuit breakers utilizing multiple extinguishing jets for effecting rapid cooling and interruption of the arc stream.

The successful interruption of high voltage alternating power circuits by a blast of arc extinguishing fluid depends to a great extent on the effectiveness of the blast in breaking up the continuity of the arc stream and interposing near a current zero fluid dielectric between the separating contacts of the breaker at such a rate that the rapidly rising recovery voltage cannot puncture or break down the interposed dielectric. If the arc is not reignited during this critical period, the interrupting operation is generally successful as the separating contacts are now adequately insulated from each other by fresh dielectric. It will therefore be apparent that the are interrupting operation can be improved by increasing the effectiveness of the fluid blast in breaking up the continuity of the arc stream.

In accordance with my invention, I arrange a plurality of jets of arc extinguishing fluid with respect to the arc stream so that they converge from different directions on the arc stream in slightly offset planes so as to produce a shearing effect on the are stream. This results not only in subiecting portions of the arc to cross blast action but also in sharply breaking at one or more points the continuity of the arc stream for introducing dielectric thereat.

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

Referring to the drawing, Fig. 1 is an eleva tional view of a fluid blast circuit breaker embodying my invention illustrating an are interrupting operation, Fig. 2 is a plan sectional view taken along the line i -2 of Fig. 1, Fig, 3 is an elevational view partly in section of a modified form of my invention in more simple form and Fig. 4 is a plan view of the breaker shown in Fig. 3 taken along the line 4-4 of Fig. 3.

The circuit breaker shown by Fig. 1 comprises a pair of relatively movable contacts, namely a fixed contact I and a movable rod contact 2 arranged to engage in butt contact to complete the circuit between the breaker terminals diagrammatically indicated at 3 and 4. The coacting contacts operate within an insulating housing 5 having a centrally disposed arc extinguishing chamber or recess 6 that is in the present instance open to atmosphere at one side of the casing at 6'. The invention as illustrated in the present case is applied by way of example to a gas blast circuit breaker so that the opening 6 is shown communicating directly with atmosphere.

As shown, the fixed contact I is suitably mounted in the upper part of the chamber 6 and the coacting movable contact 2 is operable longitudinally of the chamber through a lower guide opening 5 in the lower wall of the breaker casing. Accordingly, when the contacts are sep* arated to open the circuit an arc is drawn sub-- stantially along the central longitudinal axis of the chamber 6.

For the purpose of effectively interposing fiuid dielectric, specifically gas, between the separating contacts for the purpose of breaking up the con-- tinuity or the arc stream, there are provided in the side walls of the arc chamber 6 a plurality of slot-like passages generally of fan shape arranged to communicate with a source of gas under pressure. The source of gas (not shown) can conveniently be a compressor tank communicating through suitable valve control means (not shown) with the gas supply conduits and 'l. The supply conduit 7 communicates with a longitudinal bore 8 in the casing 5 which in turn communicates with the arc chamber 6 through a plurality of slot-like passages S. The passages ii are spaced along the longitudinal axis of the arc stream so that the planes generally defining the passages are parallel and tending in a direction transversely of the arc stream as illustrated by Fig. 1. Accordingly the issuing sheet-like jets act in a direction so as to cause a cross blast at the arc stream as best illustrated by Fig. 1. More specifically, the gas blasts from the passages 9 are directed diagonally across the arc chamber 8 as specifically illustrated by Fig. 2.

The supply conduit 1' also communicates with a bore In in the casing 5 defining a passage extending substantially parallel to the passage 8 at the opposite side of the casing. As in the case of the passage 8, the passage l0 also communicates with the arc chamber 6 through a plurality of similarly arranged slot-like passages H which are spaced along the longitudinal axis of the arc stream so as to direct gas blasts diagonally across the chamber 6 in a direction to cause a cross blast at the arc stream.

The planes generally defining the slot-like passages II are, however, offset to a certain extent or interleave with respect to the planes generally defining the passages 9 so that the converging blasts from the passages 9 and II respectively act in pairs to produce a shearing effect on the arc stream. This action is diagrammatically illustrated in Fig. 1 wherein the sheet-like blasts from the passages 9 and II acting on the arc stream l2 are indicated by the dotted lines 8' and II respectively. It will be noted that the arc is subjected at'a plurality of points to the shearing action of pairs of converging overlapping jets so that the coaction of the jets is most effective in breaking up of the continuity of the arc stream.

Furthermore, a number of portions of the are are subjected to strong cross blasts of extinguishing jets so that the probability of arc interruption by cross blast action is greatly increased. By reason of the overlapping arrangement of the opposing gas blasts, the surface of the arc stream exposed to the gas blasts is made comparatively large so that a more effective cooling of the arc stream also results. In other words, no part of the arc can escape an intense cooling action by the fluid blast.

An important consideration in the operation of prior types of cross blast circuit breakers is the deterioration under influence of the arc of extinguishing structure such as insulating barriers or bafiles against which the arc is driven by the blast. In the case of frequent interruptions of large power currents, this deterioration of the insulating structure, such as hard fiber cross barriers, is considerable necessitating replacement of breaker parts. However, it will be noted that in the present case the cross blast principle, which in practice has proved to be effective, can be applied to the arc stream without the use of insulating cross barriers. That is the blasts from the slot-like passages at one side of the arc chamber form sheets of dielectric which in efiect serve as barriers for the arc with respect to the blasts coming from the opposite side of the chamber, and vice versa. Accordingly, the arc is clipped into a pluralityof sections by cross blast action within a free space with no appreciable accompanying breaker structure deterioration.

It should be understood that the number and positioning of the jet passages 9 and II can vary to suit the particular interrupting requirements of the breaker.

The embodiment of my invention illustrated by Figs. 3 and 4 illustrates to a more pronounced extent the shearing effect on the arc stream of oppositely positioned and slightly overlapping sheet-like jets. In this design, the arc l2 formed between the fixed and movable contacts I and 2 is surrounded by an insulating annular structure l3 forming, a gas passage I 4 in communication with the supply conduit IS. The passage l4 communicates with the free space in which the arc I2 is drawn through the center of the annular structure l3 by way of slot-like passages or nozzles I6 and I1.

As best illustrated by. Fig. 3, the passages l6 and I! are arranged to direct Jets of gas transversely of the arc stream as indicated at l6 and I1 respectively. The slot-like passages l6 and I! define the blast nozzles for directing the opposing jets of gas in slightly offset relation with respect to each other so that the arc stream is; Iegrentually sheared at the portion indicated a A particularly important feature of my inven-.

tion is that the blasts are effective to shear the arc notwithstanding the magnitude of the arc current. In previous types of fluid blast breakers, both liquid and gas, excessive back pressure created by large arc currents often interfered with application of the blast itself. For example, in the well-known nozzle or radial type gas blast breaker, a high current are may create such back pressure that the gas blast cannot be eflectively directed through the nozzle for interrupting the arc.

In accordance with my invention, however, the arc is drawn in comparatively free space so that excess arc pressure is readily dissipated. However, the arc is subjected, as above described, to strong cross blast action notwithstanding the absence of insulating baflie structure or the like for partially confining the arc, Since, as above pointed out, the back pressure generated by the arc itself can escape freely without preventing positive operation of the blast jets, the comparatively cool jet can penetrate with comparatively little hindrance into the core of the are thereby greatly facilitating the interrupting operation, whereas under the pressure conditions existing in previous structures this was either very diflicult or impossible.

By applying a more positive shearing action as shown by Fig. 3, the extinguishing medium is concentrated on a comparatively small portion of the arc length, thereby greatly reducing the energy dissipated during the interrupting process. Such limitation of energy liberation, l. e.. heat, is obviously advantageous since deterioration of the circuit breaker structure is thereby minimized. 1

It should be understood that my 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 from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric circuit breaker of the fluid blast type comprising relatively movable contacts separable to form an are within a free space, means for directing a jet of arc extinguishing fluid transversely across the arc stream, and

means for directing a second jet of arc extin-- guishing fluid from another direction transversely across the arc stream, said jets being in shearing contact with each other and directed so asvto shear the arc stream between them.

2. An electric circuit breaker of the fluid blast type comprising relatively movable contacts separable to form an are within a free space, a slot-like passage for directing a sheet of arc extinguishing fluid transversely of the arc stream, and a second slot-like passage for also directing a sheet of arc extinguishing fluid transversely of the arc stream, said sheets of fluid being in shearing contact with each other and converging on said arm stream from different directions in overlapping relation so as to produce a shearing efiect upon said are stream within said free space.

3. An electric circuit breaker of the gas blast type comprising relatively movable contacts separable to form an are within a free space, a slot-like passage arranged adjacent to said are at an intermediate point thereof for directing a sheet of arc extinguishing gas transversely of the arc stream in cross-blast relation, and a second slot-like passage also similarly arranged for directing a sheet of arc extinguishing gas transversely of the arc stream in cross-blast relation, said sheets of gas being in shearing contact with each other and in parallel overlapping planes. and converging on said are stream from difierent directions so as to produce a shearing effect upon said are stream within said free space.

4. An electric circuit breaker of the gas blast type comprising relatively movable contacts separable to form an arc with a free space, a plurality of slot-like passages arranged closely ad- Jacent to and intermediate part of said are for directing in cross blast relation sheets of arc extinguishing gas transversely of the arc stream, and a second plurality of slot-like passages similarly arranged for also directing in cross blast relation sheets of are extinguishing gas transversely of the arc stream, said sheets of gas being in shearing contact with each other and converging on said arc stream from different directions in interleaving relation so as to produce a shearing effect upon a number of portions of said arc stream within said free space, the first-named plurality of sheets of gas serving as insulating barriers for the cross blasts due to said second plurality of sheets, and vice versa.

5. An electric circuit breaker of the gas blast type comprising relatively movable contacts, and two nozzles for directing opposing jets of gas under pressure transversely through the are formed upon separation of said contacts, said nozzles forming sheet-like jets arranged to converge from different directions on said arc, the planes generally defining said sheet-like jets being parallel to each other and at right angles to the length of said are, said jets also closely overlapping and in Shearing contact with each other so as to produce a shearing effect on a portion or the arc stream.

DAVID C. PRINCE.