US2081830A - Electric circuit interrupter - Google Patents

Description

May 25, 1937.

E. B. MERRIAM ELECTRIC CIRCUIT INTERRUPTER Filed Jan. 2s, 193s OIL LEVEL Inventor: Ezra B. Merriam,

` HIS Attorreg.

Patented May 25, 1937 Imotorino omom'r nv'rEnnnr'rEa Ezra B.V Merriam, Swarthmore, Pa., assig'nor General Electric Company, a corporation of New York Application January 2s, 193s, sei-iai No. cuss My invention relates to electric circuit interrupters, more particularly to circuit interrupters of the liquid blast type wherein the are is subjected to a substantially transverse or cross blast voi? arc extinguishing liquid during a circuit opening operation, and has for its principal object the provision of an improved circuit interruptor of the aforesaid type.

y My invention will be more fully set forth in the following description referring to the accompany 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 speciiication.

Referring to the drawing, Fig. i is an elevational view, partly in section, of the operative part of an electric circuit breaker lembodying my invention; Fig.2 is a similar view illustrating a modication of the arrangement shown by Fig. 1; Fig. 3 is an elevational view, partly in section, of a double-break type of circuit breaker; and Fig. 4 is likewise an elevational view, partly in section, of another form of double-break circuit breaker embodying my invention.

In certain types of liquid blast circuit interrupters the arc formed upon opening of the circuit is drawn within a pressure conflning chamber adjacent to and generally transversely oi' a pressurerelief opening or port. The arc pressure generated within the chamber directs `a. turbulent blast of are extinguishing liquid through the relief port, tending to interrupt the arc at that point.- Where an appreciable body or head of arc extinguishing liquid, such as insulating oil for example, is directly in the path of the blast. it will be apparent that acceleration of this mass of liquid tends to a certain degree to slow up the application of the arc interrupting blast. l

In accordance with my invention, an appreciable part of the aforesaid body of liquid is acA celerat-ed in a direction away from the liquid blast upon opening of the circuit by piston structure, or the equivalent thereof. coincident with d the circuit opening movement, the back pressure at the pressure relief or exhaust port is thereby appreciably decreased so that the arc at that point is subjected to the eect of the liquid blast without appreciable delay.

50 Fig. 1 illustrates a simpleway of carrying out my invention in a low-voltage single-break oil circuit breaker. ln this case, the circuit breaker casing i is provided with an insulating lining i and an insulating partition 2 forming an upper low pressure or pressure 4relief chamber 3 and a (ci. sou-15u) lower pressure confining or arc chamber I. A movable contact rod 5 extends through the partition 2 and engages at its lower end a iixed socket contact 6 which is mounted in the lower wall of the switch casing. Upon opening the circuit, the rod contact 5 is elevated for separating the contacts. The switch casing l contains a suitable arc extinguishing liquid,r such as circuit breaker oil, to the level indicated.

The pressure relief passage for the chamber 4 is formed in the present instance by insulating structure I forming an annular space or passage, the inner side oi which is providedvwith a circular port 8. This annular passage is in communication at 8 with a pressure relief insulating conduit-at lli formed along the side wall ofthe circuit breaker casing. As illustrated, the arc drawn between contacts 5 and 6 is centrally of the circular relief port 8 and transversely thereof, 'so that the arc pressure within the chamber I tends to expel oil through the arc radially into the relief port.

For the purpose of appreciably reducing the back pressure at the exhaust port 9 for facilitating the oil'blast, a piston Y il is mounted within the passage Hi which forms the cylinder thereof,

and is operatively connected to the movable rod contact 5 or switchoperating mechanism so as to be raised when the rod contact is raised. The particular arrangement for connecting the piston rod i2 to the movable contact structure forms no part of the present invention and may be as in Fig. 2 wherein the piston moves directly with the rod contact, or as in Fig. 4 wherein the piston is connected through a pivoted lever to the movable contact structure. In this latter case, of course, the relative movement between the movable contact and piston may be as desired.

The piston il upon opening of the circuit may initially move a predetermined, distance prior to actual separation of the contacts, thereby tending to set in motion, by suction, the oil towards y the exhaust passage 9V. Furthermore, if the speed of the piston H is greatly increased with respect to the contact opening movement, a partial vacuum may momentarily exist within the relief passage upon opening of the circuit, therebyY greatly facilitating the oil blast from the chamber l. This increased speed of application of the oil blast is of considerable importance in interrupting the arc within a few cycles at cornmecial frequencies.

Fig'. 2 illustrates a modified form of Fig. l wherein the relief port is sixnplied and provided with arc splitting insulating bames. In this arrangement, the exhaust passage 9 is formed by a tubular extension I3 of the insulating lining terminating adjacent the iixed contact S so that the arc is drawn transversely of the passage 9.

An insulating baille I4 is suitably disposed within the passage 9 transversely of the arc path so that the arc is broken up when driven into the passage 9, the portions of the arc in the passage being acted upon by separate oil blasts.

The piston rod I2 is directly connected through a member I2v to the movable rod contact 5 for operating the piston in the manner above described upon opening of the circuit. However, as above pointed out, the connection between the piston II and the rod contact may be chosen so as best to anticipate the operating requirements of the breaker.

Fig. 3 illustrates a double-break oil circuit breaker comprising fixed contacts I5 of the well known finger type construction and a movable bridging member I6 connected to a central lift rod I1 for moving the bridging member into and out of engagement with the contacts I5. The xed contacts Il are mounted at the lower ends of the lead-in insulating bushings I 8 which are suitably mounted in the cover structure (not shown). of the circuit breaker tank. The relatively movable contact structure above described is immersed in an insulating liquid I9, such as oil.

Enclosing the contact structure Within the main circuit breaker tank (not shown) is an insulating casing forming a pressure confining chamber and having pressure relief ports 2| opposite the breaks, respectively, formed between the iixed contacts Il and the bridging member I6. The casing 20 is provided with an upper insulating baille 22. preferably below the level of the oil I8, for directing the oil blast through the ports 2I when arcing pressure is generated within the chamber. i

In this arrangement the'oil body in the path of the blast is accelerated by means of `a piston 2l operatively connected to the lift rod I1 and operable within an insulating cylinder 24. The cylinder 24 at its lower end is provided with lateral exhaust openings 25 which are generally in alinement with the ports 2|. The piston 23 may have a resilient connection with the rod I1 compricing a spring 2B and shoulder 21 for initiating, if desired, movement of the contact structure prior to movement of the oil piston. However, it will be apparent that this arrangement may be reversed, if desired,.as in the previous case,

- depending upon the power of the operating mechanism available and the requirements ofthe breaker.

In operation, downward or opening movement of the bridging member I6 is accompanied by movement of the piston 2l. causing a lateral flow of oil from the cylinder side ports 25 in the direction of the ports 2|. 'Ihe arc pressure within the chamber, assisted by the accelerated body of oil, is therefore more effective to expedite the oil blast and interrupting arcing.

Fig. 4 illustrates an oil circuit breaker of the general type shown by Fig. 3, wherein the oil body exteriorly of the relief ports is accelerated and the back pressure at those ports appreciably reduced as in the case of Figs. 1 and 2. In this case. the circuit breaker tank'll contains insulating oil I9 in which are immersed the fixed contacts I5 and the movable bridging menibers Il. The lead-in insulating bushings Il. as in v the prsviom instance, an suitably supported in the cover of the breaker tank. The bridging vmember is connected to the conventional lift rod I1 for opening and closing the circuit in the usual manner. Enclosing the contact structure, as in the previous case, is the insulating casing 20 provided with the upper baiile 22 forming the pressure confining or arc chamber. The chamber is provided with lateral relief ports 2| located opposite the two breaks formed upon opening of the circuit.

'I'he relief openings 2| communicate with upwardly extending cylindrical passages 2B open- ,ing into the low pressureregion above `the baille 22. Operable within the cylindrical passages 28 are pistons II, the piston rods I2 of which are connected, respectively, to the lift rod |1 'through pivoted levers 29, respectively. 'Ihe levers 29 are pivoted with respect to the circuit breaker struc` ture, as at 30, and are provided with pin and slot connections at 3| and I2 with the pistons and lift rod, respectively. Further description of the operation of the circuit breaker shown in Fig. 4 is believed to be unnecessary other than to point out that the pressure generated within the arc chamber upon opening o'i' the circuit tends to cause va cross blast generally predominating through one or the other of the relief ports 2l, this blast being appreciably aided by the 1eduction of back pressure by the piston operation at the aforesaid ports.

It should be understood that my invention is not limited to specic 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. y

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

1. An electric circuit interrupter of the liquid blast type comprising a casing forming a pressure confining chamber, relatively movable contacts operable within said chamber, said chamber containing an arc extinguishing liquid and provided with a pressure relief port, said contacts arranged to draw an arc within said chamber opposite and substantially transversely of said port so that arc pressure in said chamber tends to extinguish the arc by liquid blast through said port, and a piston disposed exteriorly of said chamber operatively connected with respect to the movable contact for reducing by suction the back pressure to said liquid blast at the exhaust side of said port in accordance with the circuit opening operation.

2. .An electric circuit interrupter of the liquid blast type comprising a casing forming a pressure confining chamber, said chamber containing an arc extinguishing liquid, relatively movable contact structure operable within said chamber including a pair of fixed contacts and a movable bridging contact arranged to form two breaks in series. said chamber having a pressure relief port .substantially opposite each of said breaks, and

piston structure disposed exteriorly of said chamber operatively connected with respect to said bridging contact for reducing the pressure in said chamber and accelerating liquid in the direction of said ports and transversely of said breaks in accordance with the circuit opening operation.

3. An electric circuit interrupter of the liquid blast type comprising a casing forming a pressure connning chamber, said chamber containing an arc extinguishing liquid, relatively movable contacts operable within said chamber including a pair of 'xed contacts and a movable CFI and a piston operable exteriorly of each of said ports, and means operatively connecting said pistons with respect to said bridging contact for lowering the back pressure by suction at e'ach of said ports in accordance with the circuit opening operation; l

' EZRA B. MERRIAM.

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