US2345375A

US2345375A - Electric circuit breaker

Info

Publication number: US2345375A
Application number: US469519A
Authority: US
Inventors: Robert M Bennett
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-12-19
Filing date: 1942-12-19
Publication date: 1944-03-28
Anticipated expiration: 1961-03-28
Also published as: GB566685A

Description

March 28, 1944. R, M. BENNETT 2,345,375

ELECTRIC CIRCUIT BREAKER Filed DSC. 19, 1942 Inventor: Robevt M. Bennett, by )V0/75,3

His Attorney Patented Mar. 28, 1944 ELECTRIC CIRCUIT BREAKER.

Robert M. Bennett, Ithan, Pa., assigner to Gen` eral Electric Company,v a corporation of New York ' applicati@ December 19, 1942, serial No. 469,519

4 claims. l(ci. 2012+148) vMy invention relates to electric circuit breakers, more particularly to circuit breakers of the gas blast type wherein a blast of arc extinguishing gas such as air under pressure is directed into the arc gap formed upon separation of the breaker contacts, and has for its principal object the provision of an improved circuit breaker of the aforesaid type that is more efficient in its cooling treatment and disposal of the interrupting blast gases that are ventedfrom the breaker for pre-r venting ejection of llame therefrom.

In a s successful and well-known type of, air blast circuit breaker, the air blast is directed sub-v stantially transversely of the arc to drive the arc into insulating arc chute structure where it is extinguished. In this design, the arc is drawn across a plurality of insulating arc barriers forming exhaust passages in the chute and the gas blast is applied at the opposite side to drive the arc against the barriers and into the passages. In this form of cross blast breaker a movable blade contact coacts with aA fixed contact opposite the insulating arc barrier edges so that the exhaust passages are uncovered in sequence, the first passage to be uncovered being the farthest from the chutes main exhaust passage. Accordingly, the passage last to be uncovered, which is nearest the main exhaust is adapted when the arc is interrupted early in its formation to direct comparatively cool unheated blast air into the highlyheated gases that are vented from the first passage or passages so as to mingle with and cool said gases. Also since. theexhaust gases often contain combustible gases, the fresh air blast supplies oxygen for aiding complete combustion before nal venting, thereby tending to eliminate flame-throw from the breaker.

In accordance withV my invention, the ejection of flame from thebreaker is greatly minimized by means forboth cooling the gases by heat transfer to metallic surfaces and for creating a high degree of turbulence and centrifugal action in'the main exhaust passage includingvanes or the like arranged to direct the blast gases toward the exhaust alonga helical path or aseriesV of helical paths. l c

yA 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 ls an elevational vlew in section illustrating a crossblast air open circuit position thereof, and Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1.

The cross-blast type air circuit breaker shown by way of example in Fig. 1 comprises relatively -movable arcing contacts, such as fixed contact structure I of the linger type'and a reciprocally guided blade-like contact 2. The xed contactis electrically connected as indicated to one line terminal of the breaker at 3 and the blade- Vlike movable contact is also indicated as con-` nected to the other line terminal at 4. The blade contact 2 is movable by suitable actuating means (not shown) along a generally rectilinear path to make and break the circuit with respect to the xxed contact I. f

For the purpose of extinguishing the arc formed between the contacts when a power circuit is opened, an insulating arc chute 5 is arranged with respect to the contacts so that the arc is drawn at the entrance of the chute directly opposite a gas blast supply conduit 6. The conduit E is suitably connected through a blast control valve (not shown) to a source of compressed gas, such as air, comprising for example a storage tank and compressor equipment (not shown).

.The arc chute 5 defines a narrow, diverging space into which the arc is driven and extinguished by the blast and is formed by diverging end walls I and 8 and comparatively closely spaced parallel side walls, one of which is shown at 9, connected to a bottom wall ID through which the blast passage extends. The walls of the chute are composed of a mechanically strong insulating material, such as a molded laminated structure.

.The exhaust end of the chute is closed except for a laterally extending conduit or stack II which directs the heated blast gases away from the circuit breaker proper. The conduit I I forms the main exhaust passage for venting the blast gases fromthe breaker proper.

The chute also includes a plurality of insulating arc barriers I2 and I3 that are disposed edge wise to the arc path with the barrier Width transversely of the arc path so as to form diverging gas passages in which are spaced metal cooling plates I4 leading to the exhaust conduit. The barriers extend fairly close to the arc path as indicated and are composed of a vaporizable insulating material such as hard nbre that does not lose its insulating characteristics in the presence of the arc. The insulating material does however give off highly heated gases in vaporizing that produce flame when united with air or oxygen. This may be explained as follows; The excircuit breaker ,embodying my inyention in theta-haust gas in the breaker contains unburned caring of the gas.

gases.

bon, hydrogen, carbon monoxide, and solid carbon particles which come from the destruction of the insulating parts of the circuit breaker, and in addition, particles of copper and tungsten from the contacts. The gases may be suihciently cool to faihto burn upon being mixed with fresh air, but either spontaneous combustion of the carbon particles or ignition by incandescent solid particles of copper and carbon often causes burn- This is the flame that is often ejected during the interruption of heavy power currents.

A circuit breaker of this character is disclosed and claimed in Prince et al. Patent No. 2,284,842, issued June 2, 1942, for Circuitbreaking apparatus and assigned to the same assignee as the present invention.

The arc .chamber or space in'which the arc. is drawn is formed at the entrance of the chute between the iblast supply conduit 6 and the arc barriers I2 and I3 and constitutes an elongated chamber I5 having at one end an opening I6 in registry with the movable contact 2 which can move exteriorly of the chute to a safe isolating distance. The barrier I3a extends entirely across the arc chamber for conning the arc flame to the chute interior. and has a slot I3b-also in registry with the contact 2. The arc formed between the separated contacts may extend longitudinally of the chamber as is evident from Fig. l so as to be in the direct path of thel gas blast a-s it is'.

directed into the chute. The arcing is preferably confined to specialarcing portions or tips I and 2' on the fixed and movable .contacts respectively.

It will therefore be noted that the arc gap initially is formed adjacent to and across the entrance to the first exhaust passage I2 definedv by the barrier I2 and the arc chute end wall 8. This passage is farthest from the exhaust conduit II. The movable contact, as: it is Withdrawn from the chute uncovers the other exhaust passages in succession which are progressively' nearer said conduit.v The arc chute end at the blast exhaust conduit forms in effect a mixing chamber I3c for the exhaust gases. In this arrangement the blade contact moves from the fixed' contact so as to open the rst :passage at I 2 so that the initially formed arc can be looped by the blast against the edge of the first barrier I2. The arc is often interrupted at the first arc barrier. In such a case fresh blast air, for example, enters the chamber I3:c from the later uncovered passages before complete venting of the highly heated and partly combustible arc gases and mixing of these gases with air'therefore takes place within this chamber. However, this mixing in itself is often inadequateto prevent flame ejection from the breaker.

There are a number of factors involved in flame ejection or throw from the breaker; For example, if the gases are sufficiently cooled and no l igniting means, such as incandescent particles are present, there may be no flame even though combustible gasesare vented with other exhaust Also, if complete combustion takes place within the breaker and exhaust passages before venting there will be no ame. In accordance with my invention, the exhaust gases areV cooled,

thoroughly intermixed by turbulent flow to bring about more complete combustion and also subjected to centrifugal action for separating out solid. incandescent particles, such as metal, carbon, etc.

In a specific. form of my invention shown by Fig. 1,.the. exhaust conduitrll' isprovided with a plurality of stationaryV metal vane structures I1 of fan-like form. Each vane structure I'I as shown by Fig. 2 comprises blades Il having a suitable pitch for imparting a positive helical motion or whirl to the exhaust gases. The vane structures I'I are also sufficiently spaced within the exhaust passages to form in effect a series of combustion and. separating chambers for both burning the gases and separating out solid particles. It will be apparent that due to the high linear velocity of the exhaust gases through conduit I I, there will be set up by the whirling motion indicated in Fig. 1 positive centrifugal forces tending, to throw solid incandescent particles to the conduit Walls where they are precipitated instead of being expelled with the arc gases. Accordingly, the possibility of igniting any combustiblegasesthat escape complete burning within the breaker is greatly reduced.

Although I have shown the pitch of the blades I1 substantially uniform it will be apparent' that they can be varied to anyvsuitable degree. Also, the pitchk of the blades of certain vane structures can be reversed so that, for example, the gases are whirled clockwise in one chamber, such as I8, and relatively counterclockwi'se' in an adjaf skilled in` the art without departing from the:

spirit of my invention.

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

l. An. electric. circuit breaker of the gas blast type comprising anarc extinguishing chamber, said chamber .including Vaporizable insulating structure, means including a gas blast for inter--4 rupting the arc formed upon opening ofthe cir'- cuit within said chamber, an exhaust passage for venting the` blast gasesfrom said chamber, said4` gases including combustibley gases and carbon and metal particles from said chamber; and meansdisposed in said exhaust passage for` irnparting to said gases a whirling motion progres'- sing'towardl the exhaust 'end' of said passage so that turbulence of said gases is promoted within said` passage and solidf particles in said gases are precipitated tothe passage walls by centrifugal action thereby minimizing flame at the atmospheric exhaust of said passage. v

2. An` electric circuit breaker of the gas blast type comprising an arc extinguishing chamber, means including a gas blast for interrupting the arc formed upon opening of the circuit within said chamber, an exhaust passage for venting the blast gases fromsaidv chamber to' atmosphere, and means including vane structuredisposed inY said exhaust passage at spaced intervals for causing" said gases to flow along a generally helicalxpath leading to the exhaust of' said passage so that turbulence of' saidgases is promoted within said passage and solid" particles in said vgases are pre iipitated to the passage walls by centrifugal acon. A

3. An electric circuit breaker of the* gasblast type comprising an. arc extinguishing chamber,

means including` a gas blast for interrupting the arc formed upon opening of the circuit within said chamber, an exhaust passage for venting the blast gases from said chamber, and a plurality of relatively fixed vanes disposed in said exhaust passage at spaced intervals, said vanes being positioned with respect to the linear flow of said gases for imparting to said gases a whirling motion leading to the exhaust of said passage so that solid incandescent particles in said gases are precipitated to the passage Walls by centrifugal action thereby to minimize llame when the gases are finally Vented to atmosphere.

4. An electric circuit breaker of the gas blast type comprising an arc extinguishing chamber,

means including a gas blast for interrupting the arc formed upon opening of the circuit Within said chamber, an exhaust passage for Venting the blast gases from said chamber, and a plurality of fan-like structures disposed in spaced relation in said exhaust passage, said fan-like structures having blades pitched with respect to the linear flow of said ga-Ses through said passages for imparting to said gases a whirling motion so that turbulence of said gases is promoted within said passage for aiding combustion and solid incandescent particles in said gases are precipitated to the passage walls by centrifugal action.

ROBERT M. BENNETT.