US3670125A

US3670125A - Blast nozzle for self-blasting compressed gas electric circuit-breakers

Info

Publication number: US3670125A
Application number: US134269A
Authority: US
Inventors: Benito Jose Calvino Y Teijeiro
Original assignee: Magrini Fabbriche Riunite Magrini Scarpa e Magnano MSM SpA
Current assignee: Magrini Fabbriche Riunite Magrini Scarpa e Magnano MSM SpA
Priority date: 1970-04-16
Filing date: 1971-04-15
Publication date: 1972-06-13
Anticipated expiration: 1989-06-13
Also published as: GB1351860A; NO129596B; FR2089725A5; ES390208A1; CA938966A; SE371531B; CH535487A; DE2118166A1; DE2118166B2; BE765779A; JPS5341346B1; BR7102243D0; DE2118166C3

Abstract

An axial blast breaking chamber for self-blasting compressed gas electric circuit breakers wherein the chamber wall is provided with a plurality of radial holes having an entrance to the inside of said breaker chamber through a ring-like feeding groove coaxial to the longitudinal axis of the chamber. When the contacts are closed the fixed contact, which is in close proximity to the inner wall of the chamber, extends past the feeding groove thereby inhibiting flow of quenching gas. Flow of quenching gas remains inhibited until the chamber and attached movable contact are displaced sufficiently to withdraw the feeding groove and radial holes below the lower end of the fixed contact.

Description

United States Patent Calvino y Teijeiro [54] BLAST NOZZLE FOR SELF -BLASTING COMPRESSED GAS ELECTRIC [2]] App]. No.: 134,269

[30] Foreign Application Priority Data April 16, 1970 Italy ..23394 A/70 [52] US. Cl.... ..200/l48 R, 200/148 A [51] Int. Cl. ..H0lh 33/70 [58] Field of Search ..200/l48 A, 148 G, 148 C, 148 R [451 June 13, 1972 Primary Examiner-Robert S. Macon AttorneyStevens, Davis, Miller & Mosher [57] ABSTRACT An axial blast breaking chamber for self-blasting compressed gas electric circuit breakers wherein the chamber wall is provided with a plurality of radial holes having an entrance to the inside of said breaker chamber through a ring-like feeding groove coaxial to the longitudinal axis of the chamber. When the contacts are closed the fixed contact, which is in close proximity to the inner wall of the chamber, extends past the feeding groove thereby inhibiting flow of quenching gas. Flow of quenching gas remains inhibited until the chamber and attached movable contact are displaced sufficiently to withdraw the feeding groove and radial holes below the lower end of the fixed contact.

6 Claims, 4 Drawing Figures PATENTEnJum m2 Y 3.670.125

SHEET 1 OF 2 INVENTOR.

BENITO JOSE CALVINO Y TEIJEIRO WOQ WW TORNEYS PATENTEDJUM 1s zen BENITO JOSE CALVINO Y sum 2 0F 2 22 vrvL INVENTOR TEIJEIRO OR EY The object of this invention is to provide an improved blast nozzle for self-blasting compressed gas electric circuitbreakers, which provides substantial improvement in the performance of the breaking chambers employed in said circuitbreakers in comparison with known types. Compressed gas circuit-breakers are already well known and widely used in electric generating and distributing systems and well known are, in particular, the axial blast breaking chambers, used in these types of circuit-breakers, the shape of which has, in its various embodiments, been determined through widely known principles.

In relatively recent times the applicant has filed some other patent applications (against one of them Italian Pat. No. 791,651 has been granted, while others are still pending, one of them under reference 24973-A/69) concerning axial blast breaking chambers for self-blasting compressed gas electric circuit-breakers having a nozzle shape provided with decompression holes and ring-like grooves, said holes and grooves being formed to favor the escape of both the gases developed by the decomposition of the materials making up the breaking chambers themselves and the quenching gas, thus obtaining a concomitant flow of the first and latter mentioned gases, said breaking chambers having their downstream (or end) parts dependently relating to the circuit-breaker rated service voltage according to the experimental relation (simplified form:

L 2 v1.5 U,,),

wherein L stands for the chamber end part length, stated in,

mm, and U, is the circuit-breaker rated service voltage expressed in kV.

It has been found, however, that the known axial blast breaking chambers do not exhibit optimum performance with respect to the arc quenching gas exhaust.

An object of this invention is, therefore, to provide a breaking chamber for compressed gas electric circuit-breakers which is structurally improved incomparison with the known chambers, and particularly in connection with the breaking chambers of similar type previously disclosed by the applicant.

A further object of this invention is to provide improvements in the breaking chambers of electric circuit-breakers whereby the holes made through the chamber walls particularly favor the decompression in the nonle zone having the smallest cross section, where said holes have their entrance thereby permitting the quenching gas to escape with particular ease.

A still further object of this invention is to provide an axial blast breaking chamber wherein it is still possible to reach, and indeed to improve, the combination of the efiects of the quick decompression in the entrance zone of the through-wall holes as well as of the best possible course concomitance of the decomposition gases and the quenching gas flows through the end (or downstream) part of the interruption chamber itself, consequently accelerating the outflow of the whole of said gases through the outlet orifice of the chamber and decreasing the whirl effects occurring in the total outflow.

These and other objects, which those skilled in the art can better deduce from the following detailed description, are profitably reached by an axial blast breaking chamber for selfblasting compressed electric circuit-breakers, said breaking chamber having a blast nozzle internally shaped in way to provide, in the outlet direction, a first conical and convergent zone, a second cylindrical zone having the smallest cross-sectional area in comparison with the other internal zones and a third substantially conical and divergent zone, the length of which is determined from the already known experimental relation said third conical and divergent zone having a plurality of ringlike grooves each of which is substantially triangular sectioned within a plane passing through the chamber axis with open base towards the outlet orifice of the breaking chamber, said breaking chamber having a plurality of lateral outlet means, through the chamber wall corresponding to said second smallest cross-sectioned cylindrical zone, which communicate among themselves in the chamber inside, where said outlet means have their own entrance sections, through a ring-like feeding groove coaxial to the breaking chamber itself.

The breaking chamber which is the object of this invention will be hereinafter more detailedly described with reference to the enclosed drawings, wherein FIG. 1 schematically shows the longitudinal section, of the breaking chamber according to this invention, marked by broken line A-A'on FIG. 2, i.e., along two different axial planes.

FIG. 2 schematically shows a plan view of the same breaking chamber cross-sectioned in correspondence with plane BB on FIG. 1.

FIG. 3 illustrates the breaking chamber of FIGS. 1 and 2 with the breaker contacts in their closed position, and

FIG. 4 illustrates the breaking chamber with the contacts in the open position.

Referring to these figures, the improvement in the nozzle of the breaking chamber for self-blasting compressed gas electric circuit-breakers, being the scope of this invention, consists in providing a chamber with the following features: substantial nozzle shape according to the Venturi tube principle, with a second (or necked and smallest surfaced) zone 5 cylindrically shaped and provided with a plurality of decompression holes 6 for allowing the communication of said cylindrical smallest surfaced zone 5 with the breaking chamber outer room, said holes 6, unlike the similar decompression holes of the known art, having rather reduced diameters and being in number considerably greater than the number of holes used in known breaking chambers. The number of holes ranges from six, as a minimum, to a maximum solely limited by its compatibility with the restrictions imposed by the technological manufacturing requirements, namely the mechanical machining work the chamber has to undergo for obtaining said holes. Since large diametered holes can be made in smaller number and vice versa, and since the axes of said holes are radial to the chamber and lie within a common cross section plane of the same chamber, it is clear that an interference exists between the diameter and number of holes. The concerned improvements consists moreover in providing a ring-like (consequently coaxial to the breaking chamber and particularly to cylindrical zone 5) groove 22, made in the inner wall of the above specified smallest surfaced cylindrical zone 5, having the task of ring or duct feeding all decompression holes 6, said ring-like groove 22 having a substantially rectangular radial cross section with height h correlatively depending on the diameter d of holes 6 and depth 1 suitably dimensioned according to the breaking chamber service conditions. Entrance sections 10 of holes 6, which open to the inside of the breaking chamber (or, more exactly, to the bottom of ring-like groove 22), are parallel to breaking chamber axis YY in consequence of the shape of said groove 22. Holes 6 pass through the wall of said chamber and their sections for the debouchment into open air are referenced 1 1 on the figures.

Referring to FIGS. 3 and 4, the fixed contact 30 and movable contact 31 are shown positioned within the nozzle, movable contact 31 being secured to and moving with said nozzle. When the circuit-breaker is closed, the fixed contact 30 occupies a large portion of the space within the breaking chamber;

i.e., the whole truncated cone divergent zone 9 of the chamber fixed contact 30, being in close proximity to the inner wall surface of cylindrical zone 5, even if not fully tight, substantially hampers the quenching gas outflow, except the neglectable quantities which can escape through the usual mechanical clearances due to the machining tolerances.

As the opening operation continues, as shown in FIG. 4, the fixed contact 30 no longer blocks ring-like groove 22 and holes 6. The quenching gas outflow is from this moment established through said ring-like groove 22 and holes 6. The exhaust section area corresponds, at this moment, to the sum of the areas of the openings offered by holes 6.

In consequence of the breaking chamber parting from fixed contact 30, as soon asthe fixed contact lower end reaches the beginning of zone 9, also the sections of this zone, (said sections being substantially circular crown shaped in that they are determined inside by the above specified fixed contact and outside by the inner wall of said zone 9) are available for the outflow both of the quenching gas and the decomposition gases. The example illustrated by the figures illustrates 12 holes 6 symmetrically arranged and, therefore,

reciprocally displaced by 30. It should be noted, however,

that as already mentioned, said holes can be at least six and may be more than, 12 compatible with the manufacture requirements. (However, too small a number of decompression holes should be avoided since this reduces the number of the, outflow paths which in accordance with the invention should be as large as possible, compatibly with the condition that each hole has s sufficiently dimensioned opening).

.Remarkable results can be attained in this way: first, regularization in the gas flow through radial decompression holes 6, thanks to which the outlet from said holes becomes much easier, consequently granting a quicker decompression of cylindrical zone and reduction of the whirl effects, inside the concerned zone and generally the whole breaking chamber," to a neglectable value.

Each hole 6 made through the wall of cylindrical zone 5 is, I

in fact, a point attracting the quenching gas to the outlet way and the more of these points there are, the better are the even- ,ness conditions of the plasma which sets up the electric arc in consequence of the better quenching gas distribution. To this aim, however, the availability of ring-like groove 22 appears as detenninant, clearly characterizing the nozzle concemed by the present invention in respect to the known art. Groove 22 acts, in fact, as a chamber for equalizing the quenching gas pressure thereby improving its distribution among the'various holes and making uniform, as already said, the eddy conditions whereto the electric plasma is submitted. Through this solution, infact, the electric arc is surrounded by a full quenching gas sleeve and nearly attacked by an electric action, deionizing and quenching, which while always advantageous, is even more beneficial at the initial are striking stage when the fixed contact is still within cylindrical zone 5, consequently still keeping the nozzle closed, but having freed groove 22 and, in consequence, also holes 6. The quenching gas can in this way very energetically influence the whole of the just striken electric are by a blast and eddy action which, instead of being concentrated in the points whereat the arc is facing the holes, is distributed on its whole circumference.

The advantages obtained with this invention are increased by the advantages due to the particular shape of the chamber end zone 9 provided with ring-like triangularly cross-sectioned grooves 1 3, due to which the resultants of the elementary flow lines of the decomposition gases offer a component, parallel to axis Y-Y, which favors the outflow of both the quenching (or deionizing) gas and the decomposition gases. Although this detail of the chamber has been already described in a previous applicants patent, it is seen that, in the same chamber, the addition of the effects reached through the present and the foregoing invention permits the attainment, with regard to a quicker and fuller arc. quenching, of .more effective results than could be attained by having separate and single recourse to the above pointed out solutions.

The present invention has precisely the advantage of not in the least altering zone 9 of the chamber, the constructional shape of which has been experienced and led to remarkable success, and of only slightly altering zone 5 of the chamber, thus obtaining the advantages of the peculiar features of both zones. Ring-like groove 22, and also holes 6, can in fact be differently dimensioned but its availability does not particularly alter the nozzle construction. As already mentioned, said ringlike groove has, preferably, a radial rectangular cross section which can however be also triangular, semicircular, or otherwise suitably shaped.

Evidently modifications and alternatives can be brought to the invention, as hereinabove described, exemplified, illustrated, and hereunder claimed, without getting out of the inhave their axis not perpendicularly positioned toward chamber axis Y-Y but suitably slanting, towards axis Y-Y, in that direction which provides an improvement in the gas outflow, precisely to define towards said axis Y--Y an angle smaller than in the direction of the chamber outlet orifice Moreover, ring-like groove 22, which together with the relevant plurality of holes 6 characterizes this invention, provides improvements in the operation of the circuit-breakers, when used in similarly styled breaking chambers of the known art.

What is claimed is: 1. In an axialblast breaking chamber for self-blasting compressed gas electric circuit breakers having fixed and movable contacts (30, 31), a blast nozzle internally shaped to provide, in the outlet direction, a first conical and convergent zone (1 a second cylindrical zone (5) and a third substantially conical and divergent zone (9) having a length L equal to or greater than i I where U,, is the rated service voltage of said circuit breaker,

said second zone (5) having a cross-sectional area not greater than that of said first and second zones, and said third zone (9) having a plurality of ring like grooves (13) each of which has a substantially triangular cross section within a plane passing through the longitudinal axis (Y--Y)'of the chamber, said ring-like grooves being open toward the outlet orifice (2) of the breaking chamber, wherein the improvement comprises having a plurality of lateral outlet means (6), through the chamber wall corresponding to said second smallest cross-sectioned cylindrical zone (5), which outlet means (6) communicate among themselves in the chamber inside, where they have their own entrance sections (10), through a ring-like feeding groove (22) coaxial to the longitudinal axis (Y-Y) of the breaking chamber itself.

2. An axial blast breaking chamber as defined by claim 1 wherein said chamber is provided with at least six lateral outlet means.

3. An axial blast breaking chamber as defined by claim 1 wherein said lateral output means are radial holes having circular cross sections.

4. An axial blast breaking chamber as defined by claim 1 wherein said lateral outlet means areradial holes having a 7 diameter (d) as small as possible, compatibly with gas outflow requirements, and thereby provide the maximum number of holes in said chamber wall.

5. An axial blast breaking chamber as defined by'claim 3 wherein said ring-like feeding groove (22) is, with respect to a plane passing through the chamber axis, substantially rectangular in cross section and has a height (h) at least equal to the diameter (d) of the radial outlet holes.

hibiting flow of the quenching gas, said flow continuing to be inhibited until said movable contact and nozzle are displaced sufficiently to withdraw said ring-like feeding groove (22) below the lower end of said fixed contact.

I k '0 I

Claims

1. In an axial blast breaking chamber for self-blasting compressed gas electric circuit breakers having fixed and movable contacts (30, 31), a blast nozzle internally shaped to provide, in the outlet direction, a first conical and convergent zone (1), a second cylindrical zone (5) and a third substantially conical and divergent zone (9) having a length L equal to or greater than where Un is the rated service voltage of said circuit breaker, said second zone (5) having a cross-sectional area not greater than that of said first and second zones, and said third zone (9) having a plurality of ring-like grooves (13) each of which has a substantially triangular cross section within a plane passing through the longitudinal axis (Y-Y) of the chamber, said ringlike grooves being open toward the outlet orifice (2) of the breaking chamber, wherein the improvement comprises having a plurality of lateral outlet means (6), through the chamber wall corresponding to said second smallest cross-sectioned cylindrical zone (5), which outlet means (6) communicate among themselves in the chamber inside, where they have their own entrance sections (10), through a ring-like feeding groove (22) coaxial to the longitudinal axis (Y-Y) of the breaking chamber itself.

4. An axial blast breaking chamber as defined by claim 1 wherein said lateral outlet means are radial holes having a diameter (d) as small as possible, compatibly with gas outflow requirements, and thereby provide the maximum number of holes in said chamber wall.

5. An axial blast breaking chamber as defined by claim 3 wherein said ring-like feeding groove (22) is, with respect to a plane passing through the chamber axis, substantially rectangular in cross section and has a height (h) at least equal to the diameter (d) of the radial outlet holes.

6. An axial blast breaking chamber as defined by claim 1 wherein said movable contact (31) is secured to said nozzle and, when said circuit breaker is closed, the fixed contact (30) extends into said first conical and convergent zone (1), the outer surface of said fixed contact being in close proximity to the inner wall surface of said cylindrical zone (5) thereby inhibiting flow of the quenching gas, said flow continuing to be inhibited until said movable contact and nozzle are displaced sufficiently to withdraw said ring-like feeding groove (22) below the lower end of said fixed contact.