US2092652A

US2092652A - Electric circuit interupter

Info

Publication number: US2092652A
Application number: US758925A
Authority: US
Inventors: Ezra B Merriam
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1934-12-24
Filing date: 1934-12-24
Publication date: 1937-09-07
Anticipated expiration: 1954-09-07
Also published as: FR799837A; BE413029A

Description

Sept. 7,` 1937. E. a. MERRIAM I ELECTRIC CIRCUIT INTERRUPTER Filed Dec. 24, 1934 1 l l l inventor y Ezra B. Merriam, b5 Nan/147 M/.4441

Hi' Attorrwe'g.

Patented Sept. 7, 19137 1 UNITED STATES ELECTRIC CIRCUIT INTERRUPTER Ezra B. Merriam, Swarthmore, Pa., assigner to General Electric Company, a corporation of' New York Application December 24, 1934, Serial No. 758,925

4 Claims.' (Cl. 20o-150) My invention relates to electric circuit interrupters of the single pole type wherein the circuit 4is opened within a pressure chamber containing an arc extinguishing liquid such as oil, and the pressure generated bythe resulting arc is utilized to eiect expulsion of liquid from said chamber for extinguishing the arc.

Electric circuit interrupters of the aforesaid typeare commonly known as explosion chamber breakers and have long been used for interrupting high voltage power circuits. A well known form of explosion chamber breaker comprises an insulated explosion pot forming the explosion chamber having at one end a xed contact structure. A coacting contact rod is movable into said chamber through an exhaust opening or throat at the opposite end of said chamber. 'Ihe explosion pot and contact structure are immersed in a suitable insulating and arc-extinguishing liquid such as oil, the oil filling the explosion chamber.

When the contacts are separated to open the circuit the Well known explosion chamber effect is obtained; that is, the pressure generated within the explosion chamber by arc current causes a blast of oil through the arc as the movable contact passes through said throat. The arc is generally interrupted at that point.

In modern electric power transmission systems operating at commercial frequencies, it is highly desirable to limit the duration of arcing and hence the length of the arc. 'I'he conventional type of explosion chamber above described, however, utilizes the interrupting action of the blast mainly after the arc has been drawn throughout the length of the explosion chamber, i. e. at the throat. Although this results in effective interruption of arcing operating requirements may necessitate even faster interrupting time.

A principal object of my invention is the provision of an improved single pole electric circuit interrupter of the explosion chamber type, as contrasted with an interrupter having two ormore breaks in the same chamber, which is simple and r,inexpensive in construction and which-is effective to decrease the arcing time for breakers of the aforesaid type.

In accordance with my invention in an operative form thereof, the explosion pot or chamber is provided with an exhaust opening or port extending substantially transversely of the path of the arc, as distinguished from the throat opening through which the movable contact may operate. In this form, the width of the chamber corresponds roughly to its length so that appreciable arcing spaceis involved. The arc may be drawn eccentrically with respect to the longitudinal axis of the chamberI so as to be adjacent and transverse of said exhaust port, the remaining portion or' the explosion chamber serving as an oil reservoir. I have found that an explosion chamber breaker so constructed is effective to interrupt the arc well within the explosion chamber so that the arcing time is limited to a few half cycles.

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 eleval various single pole forms my invention may asn sume.

Fig. 1 illustrates the circuit interrupting means i of one pole of an oil' circuit breaker comprising an explosion pot I, relatively movable contacts 2 and 3, and an insulating and arc extinguishing liquid 4, such as oil, in which the explosion pot and contact structure are immersed. It shall be understood that the term oil as used hereinafter is intended to comprehend a suitable arcextinguishing liquid. The explosion pot l is suit-- ably formed o f a mechanically strong insulating material, such as a laminated structure impregnated with a phenolic condensation product, and is secured in depending relation to a flange 5 of the stationary adapter 6. The lead-in conductor l is insulated with respect to the circuit breaker tank (not shown) by the usual high voltage insulating bushing 8 at the lower end of` which,l at 9, is secured the contact adapter.

'I'he fixed contact structure 2 comprises a butt contact resiliently biased, as by a spring l0, to-

wards a lower limiting position into engagement with an annular arcing portion l I. The butt contact is electrically connected through flexible conductors I 2 to the contact retaining structure i3 which is electrically connected to the adapter 6 and hence to the leadin conductor l. l

At high voltages an insulating cylindrieai shield I4 is mounted on' a flange I5 which is supported. as at i6, by the explosion pot securing means.

The movable rod contact 3 is mounted at one end of a bridging member Il, the other end of which carries the contact of the other and similar pole of the breaker (not shown). The contact 3 is movable through an exhaust opening er throat I8 formed in the lower end of the explosion pot opposite the iixed contact 2. As will be noted, the movable contact enters the explosion chamber eccentrically with respect to the longitudinal axis of said chamber for coaction with the xed contact 2.

For the purpose of eiecting interruption of the circuit within the explosion chamber and while the arc is still comparatively short, an exhaust port I9, which is restricted as compared with the volume of the chamber, is formed in a lateral wall of the explosion pot adjacent and opposite the path of the arc. As illustrated, the arc, generally indicated at 20, is drawn transversely of the exhaust port I9 while the arc is comparatively short. I have found that with this arrangement the arcing time is appreciably reduced and that the arc is interrupted wellgwithin the chamber as compared with interruptions at or near the throat I8.

One explanation of the improved interrupting characteristics of this form of explosion chamber may be based on the fact that the arc, which by reason of its Contact with the oil generates pressure within the explosion chamber at a high rate, is subjected as indicated tothe wash of the oil as it is expelled from the. chamber through the .lateral port I9.

In View of the fact that the throat I8 is still practically closed by the movable contact 3, oil by reason of the arc pressurey within the explosion chamber must exhaust at a high rate through the port I9 into the exterior free oil body. The lines of flow converging toward the port I9 traverse the arc which is swept l toward the port and extinguished at that point While the movable contact 3 is still within the explosion chamber.

. The eccentric positioning of the movable contact within the explosion chamber not only provides an appreciable oil storage space opposite the exhaust port in the event of heavy short circuits, but also advantageously locates the arc with respect to the lateral exhaust port I9. In the event that the arc is not interrupted within the chamber the usual interrupting effect is also obtained at the throat I8.

In Fig. 2 the explosion pot I is fundamentally similar to that of Fig. 1. In this case the contact 3 moves centrally of the explosion chamber through the lower throat I8. The lateral port I9 is positioned in a side wall ofthe explosion pot as above described, and anllinsulating bailie 2I projects horizontally from the-inner wall of the explosion pot beneath the port: I9. The purpose of this balile is to direct the oil ilow from the explosion chamber so as to intensify the how across the arc. The operation is generally similar to Fig. 1.

Fig. 3 illustrates a simple application of my invention to circuit interrupters of the single break type wherein the movable contact member is elevated to open circuit position. In this arrangement the circuit breaker tank 22 is lled with oil to the level indicated,the tank having suitable insulating lining 23. A xed contact 24 is mounted at the lower part of the tank, and a movable rod contact 25 is guided for vertical reciprocal movement with respect to contact 24. The contacts coact within an interrupting chamber 26 formed by a strong insulating cylinder 21 having a reinforcing lining 28. An insulating disk 29 forms the upper wall of the interrupting chamber. The rod contact 25 is guided within a bushing 30 forming a throat at the upper Wall of the interrupting chamber.

For the purpose of obtaining the improved interrupting characteristics above described, the

' chamber 26 is provided with a lateral port at 3l substantially opposite the point of contact separation opening into the annular free space 32 formed between the insulating cylinder 21 and the breaker casing. Accordingly, upon separation of the

contacts

24 and 25 the arc pressure generated within the chamber 26 is effective to expel oil at a high rate through the port 3| for interrupting the arc at that point. In this arrangement Which is particularly adapted for comparatively low voltage power circuits, the arc is generally interrupted after a short vertical travel of the contact 25 beyond the port so that there is no necessity for moving said contact out of the interrupting chamber 26.

In Fig. 4 the explosion pot I 'is provided with the lateral port I9 at a point appreciably beyond the initial formation of the arc. As illustrated, the lateral port I9 is adjacent the throat I8 so that, although the arc length is increased, the oil flow across the arc is concentrated at the'lower part of the chamber and is greatly intensified as the Contact 3 moves into the throat I8. A powerful cross blast effect is thereby obtained which has been found to be very eiective in interrupting heavy short circuits. Y

In Fig. the explosion pot I is provided with an expulsion arc chute 33 mounted within the lateral port I9 and arranged to form a channel for receiving the arc. The expulsion chute 33 may be suitably formed of plates of insulating material, the chute opening downwardly into the oil body at 34. The chute preferably extends within the explosion chamber so that the movable contact is drawn between the side-extensions of the chute. Accordingly, the arc drawn is within or at the entrance 33 ofthe chute and is confined within the path of oil iiow as indicated so that it is swept in a denite direction by the oil blast from the explosion chamber. It will be apparent, of course. that the expulsion chute may exhaust directly outwards from the explosion chamber. Where, however, the breaker tank wall is close to the explosion chamber downward venting of the expulsion chutevmay be preferred.

In the above-described arrangements for carrying my invention into effect, conventional contact structure is employed for interrupting the circuit. However, other suitable circuit interrupting means may be employed, the fundamental concept being that of forming a break and drawing an arc within'an explosion chamber, or its equivalent, transversely of a lateral exhaust port through which oil from the explosion chamber is expelled by the arc pressure at the aforesaid break to cause interruption of the arc.

It should be understood that my invention is not limited to specific details of construction and arrangement hereof herein illustrata-i, 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. A single pole electric circuit interrupter comprising an insulating casing forming a substantially undivided pressure confining chamber containing oil, the width of said chamber corresponding approximately to its length, a xed contact disposed in said chamber and a coacting contact movable in said chamber for opening the circuit at said fixed contact, said casing having an exhaust port located adjacent to and at one side of the path of the arc drawn by said movable contact, the size of said arc chamber bearing such relation to said arc path andto said exhaust port respectively that said arc is appreciably spaced from thewalls of said casing, and the arc pressure generated Within said casing causes expulsion of oil at high velocity through said exhaust port for interrupting the arc at that point.

2. A single pole electric circuit interrupter comprising an insulating pot forming a substantially undivided pressure conning chamber containing oil, the width of said chamber corresponding approximately to its length, a xed contact disposed at one end of said chamber and a coacting rod contact movable along a path eccentric with respect to the longitudinal axis oi' said pot for opening the circuit at said xed contact, said pot having an exhaust port located adjacent and transversely of said arc path, the size of said arc chamber bearing such relation to said arc path and to said exhaust port respectively that said arc is appreciably spaced from the walls of said pot, and the arc pressure generated within said pot causes expulsion of oil at high velocity through said exhaust port for interrupting the arc at that point.

3. A single pole electric circuit interrupter comprising an insulating pot forming a substantially undivided pressure confining chamber containing oil, the width of said chamber corresponding approximately to its length, a xed contact disposed within said chamber and a coacting contact movable ln said chamber for opening the circuit at said xed contact, said pot having an exhaust port located substantially transversely of the path of movement of said movable contact adjacent the point of initial separation of said contacts and initial formation of the arc, the size of said arc chamber bearing such relation to said path and to said exhaust port respectively that the arc is 'appreciably spaced from the walls of said pot and the arc pressure generated within said pot by said initial arcing causes, expulsion of oil at high velocity through said exhaust port for interrupting the arc at that point.

4. A single pole electric circuit interrupter comprising an insulating pot forming a pressure confining chamber containing oil, a fixed contact disposed in said chamber and a coacting contact movable through said chamber for opening the circuit at said xed contact, said pot having an exhaust port located at one side of the path of the arc drawn by said movable contact, and means forming an arc chute in said chamber communicating with said port including spaced insulating members between which said arc is drawn, the size of said arc chamber bearing such relation to said exhaust port that the arc pressure generated within said pot causes expulsion of oil at high velocity through said chute and exhaust port for interrupting the arc within said chute.

' EZRA B. MERRIAM.