US3518387A - Arc-quenching electrode assembly for high-power circuit breakers and switches - Google Patents

Description

June 30, 1970 A. LATOUR 3,518,387

ARC-QUENCHING ELECTRODE ASSEMBLY FOR HIGH-POWER CIRCUIT BREAKERS AND SWITCHES Filed April 13, 1967 8 Sheets-Sheet 1 Anclr Lafour BY W ATTORNEY INVENT OR.

June 30, 1970 A. LATOUR 3,518,387

ARC'QUENCHING ELECTRODE ASSEMBLY FOR HIGH-POWER CIRCUIT BREAKERS AND SWITCHES Filed April 13, 1967 a Sheets-Sheet g Andre Lafour INVENTOR.

\ lass Attorney June 30, 1970 A.- LATOUR ARC-QUENCHING ELECTRODE ASSEMBLY FOR HIGH-POWER CIRCUIT BREAKERS A-ND SWITCHES 8 Sheets-Sheet 5 Filed April 13, 1967 Andr La'l'our INVENTOR.

ATTORNEY June 30, 1970 A. LATOUR 3,518,387

ARCQUENCHING ELECTRODE ASSEMBLY FOR HIGH-POWER CIRCUIT BREAKERS AND SWITCHES Filed April 13, 1967 8 Sheets-Sheet 4 Fig.5

Andre Lafour INVENTOR.

ATTORNEY June 30, 1970 A. LATOUR 3,518,387

ARC-QUENCHING ELECTRODE ASSEMBLY FOR HIGH-POWER CIRCUIT BREAKERS AND SWITCHES Filed April 13, 1967 8 Sheets-Sheet 5 Fly. 6

I A I I 5a- 3 15b I I l 50% I I $593131 313a. I

' I I I I I I I Andre Lafour INVENTOR.

BY i- ATTORNEY June 30, 1970 A. LATOUR 3,518,387

ARC*QUENCHING ELECTRODE ASSEMBLY FOR HIGH-POWER CIRCUIT BREAKERS AND SWITCHES Filed April 13, 1967 8 Sheets-Sheet 6 Fig. 7

Andre Lafour INVENTOR.

BY M R ATTORNEY June 30, 1970 A. LATOUR ARC-QUENCHING ELECTRODE ASSEMBLY FOR HIGH-POWER Filed April 13, 1967 CIRCUIT BREAKERS AND SWITCHES 8 Sheets-Sheet '7 ---5O Ia' v Andre Lafour INVENTOR.

ATTORNEY June 30, 1970 A. LATOUR 3,518,

ARCQUENCHING ELECTRODE ASSEMBLY FOR HIGH-POWER CIRCUIT BREAKERS AND SWITCHES Filed April 13, 1967 8 Sheets-Sheet 8 \w ll Andre Lafour INVENTOR.

ATTORNEY United States Patent Office 3,518,387 Patented June 30, 1970 Int. (:1. H01h 9/30, 33/00 U.S. Cl. 200144 12 Claims ABSTRACT OF THE DISCLOSURE Arc-quenching electrode assembly for high-power circuit breakers and switches which has a plurality of mutually parallel, transversely spaced primary plates carrying respective relatively large primary electrodes across which the breaker arc is applied and forming arc chutes for the deionization of the breaker arcs, and at least one secondary plate between each pair of primary plates and having a pair of secondary electrodes of dimensions smaller than those of the primary electrodes for subdividing each primary fractional arc into a number of secondary arcs. The secondary plates are formed with upwardly narrowing throttling slots forming a progressively constricted aperture between each pair of primary blast electrodes or horns for limiting the movement of the primary arc between them toward the secondary electrodes until the amplitude of the primary discharge falls off in its periodic sinusoidal cycle, the upwardly converging slot having a relatively narrow gap adapted to pass only a relatively thin spark and terminating substantially at the secondary electrodes. The primary electrodes and secondary electrodes are mutually offset and offset from the corresponding electrodes of an adjoining arc chute and the arc loops between the electrodes are maximalized to provide a multi-convolution configuration for the current flow which promotes the magnetic-field effect upon the discharge. The primary electrodes have extensions reaching toward the secondary electrodes and of a specific resistivity dimensioned to attenuate the current flow as the arcs move toward the secondary electrodes.

My present invention relates to an arc-quenching arrangement for high-power circuit breakers and switches and, more particularly, to a system wherein a flow of air is utilized to deionize, by cooling, a circuit-breaking arc in conjunction with an arc-splitting system of electrodes.

State of the art It has already been proposed, in connection with circuit breakers, switches and the like to provide, in addition to a mechanism for disconnecting a pair of contacts at the current-input and current-output sides of the switch, various means designed to quench the are formed upon opencircuiting these contacts. In general, several systems have been proposed for use individiually or in combination to achieve this result. It has, for example, been suggested to provide between the main contacts a number of divergent linearly extending electrodes which subdivide the arc into a plurality of smaller arcs and thereby permit easier dissipation of the heat and evenual arc quenching;

commonly these electrodes are provided above the main electrodes in a so-called arc chute or duct through which a convection current of air is induced upwardly in the direction past an array of arc-splitting electrodes. It is also possible, together with arc-splitting electrodes, to provide air-blast arc-quenching means for augmenting the coolgas flow upwardly through the arc chute. In both cases, and where heat conductors or heat sinks are provided in the arc chute or duct, 21 decrease in the temperature of the gas has the effect of deionizing the are. To this end, the arc chute or horns are determined and configured to increase the effective length of the breaker opening and facilitate dissipation or subdivision of the discharges. Finally, a magnetic-blowout system can be used in conjunction with the arc chute to effect a magnetic shaping of the arc and its eventual dissipation.

Object of the invention It is the principal object of this invention to provide an improved system for the subdivision of a circuitbreaking arc which is of economical and simple construction, conserves space, affords better heat-dissipation and faster arc quenching, and which is more easily assembled and repaired than prior arc-quenching arrangements for circuit breakers and the like.

Brief summary of the invention I have found that this object can be attained, and that improvements in the magnetic control of the arc in other aspects achieved, when the arc-quenching arrangement comprises a stack of plates against which the circuit-breaking arc is applied and which run perpendicularly to this arc and parallel to one another, preferably in vertical planes, these planes being provided with rider contacts or blast electrodes (blast horns) which subdivide the breaker discharge into a plurality of elementary arcs which are angularly offset or rotated with respect to one another with angles of approximately The angular offset of the effective electrodes and the loops of the arcs bridging same form convolutions of electric-current flow whose magnetic field is in effect that of a solenoid and shapes or controls the duration of the discharge while a cooling flow of air through the arc chutes between these plates and the dissipation of heat through the walls of chutes deionizes the discharge region and causes quenching of the arc. According to the principal features of this invention, between each pair of these primary plates, there is disposed at least one intermediate plate having an arc-throttling aperture converging in the direction of gas movement through the arc chute and adapted to control the upward movement of the respective discharge between the primary-electrode lobes or horn on opposite sides of the intermediate or secondary plates, the throttling slot terminating substantially at a pair of secondary electrodes above the primary electrodes at which the elemental are between each pair of primary electrodes is subdivided into at least two secondary arcs which are offset from one another and thereby increase the magnetic or solenoidal effect.

While it has already been proposed to orient a number of arc-splitting electrodes between respective plates in the general manner described and thereby obtain a mag netic lengthening of the arc loop and, consequently, a greater heat dissipation for early quenching of the arc, the conventional arrangements have been of limited utility because. the primary electrodes were required to be relatively close together for spatial considerations and such proximity impeded the gas flow through the arc chute. As a consequence, the arc frequently hung between the primary electrodes without forming the loops which were a requisite to the lengthening of the arc and the increased magnetic-field effect. Earlier systems in which slotted partitions were provided between the primary electrodes were ineffective because they limited the length of the are within each arc chute. By providing at the narrow end of an upwardly converging V-shaped aperture in the intermediate plate or partition, a pair of electrodes which lie alongside the faces of this intermediate plate and are adapted to form a conductive bridge between the secondary arcs formed upon subdivision of each of the elementary or primary arcs, it has been possible to avoid the disadvantages of the earlier systems and rapidly provide the solenoid effect without increasing the volume of the unit and the number of primary electrode cells. Thus, according to a feature of this invention, the converging aperture terminates in a narrow gap through which the arc of an AC. breaker discharge can pass only when the fatness of the are or its intensity decreases during the passage of the sinusoidal waveform through the null or zero condition in the amplitude versus time characteristic, the secondary electrodes being disposed above the main blast electrodes or primary horns in the region of this narrow gap and having a surface area and size which is less than that of the corresponding pair of primary electrodes.

While the invention will be described hereinafter in connection with a single secondary plate and pair of secondary electrodes between each pair of primary electrodes, it will be understood that a plurality of secondary or intermediate plates may be stacked between each pair of primary plates and all of these intermediate or secondary plates may have a respective upwardly convergent throttling slot and secondary electrode pair previously described.

The lobes of each pair of secondary electrodes, which are interconnected by a web and are preferably unitary with one another, lie generally on opposite sides of a longitudinal median plate through they narrow gap so that the secondary arcs, formed between each lobe and a respective primary electrode or between each lobe and a respective lobe. of the secondary electrode of an adjoining plate, are also angularly offset from one another whereby the secondary arcs, when taken with the secondary electrodes, form effective convolutions whose magnetic field operates in the solenoid manner previously described. Thus, the subdivision of each primary are into at least two, but generally a greater number of, secondary arcs, permits the heating effect of the discharge between the primary electrodes to be distributed to a larger number of secondary electrodes and thereby allows the metal plates constituting the secondary electrodes to be dimensioned smaller than the primary electrodes while nevertheless serving to dissipate the discharge energy. The length of the secondary are extending to each lobe of a secondary electrode and the length of the primary arc as controlled by the throttling slot may, therefore, be increased by comparison with earlier systems so that the effective space between the primary electrodes is increased without increasing the gap between the primary plates and, therefore, reducing the air-flow velocity which is conducive to arc quenching.

Furthermore, the present system has the advantage that the intensive heating and damage to the electrodes is avoided by ensuring a transformation of the primary arc into a number of secondary arcs only during the transition period at which the discharge-current intensity is minimum, i.e. in the period in which the sine characteristic passes through zero. It is important to note, in this regard, that the rapidity with which the solenoid effect is generated is directly related to the effectiveness of the socalled blast coil formed thereby. The optimum effectiveness is achieved with a minimum number of convolutions during the high-intensity current periods and a multiplication in the number of convolutions when the intensity of the discharge passes through its null value. By combining the secondary electrodes and throttling aperture slots in the manner described, a synchronization of the number of convolutions with the intensity of the discharge is achieved. The arc-splitting arrangement of this invention is thus characterized by a primary-arc chamber with a minimum number of loops and convolutions, the discharge then passing into a secondary arc chamber in which the number of convolutions and loops is at least doubled, i.e. increased geometrically.

A key advantage of this invention is that a minimum number of primary electrodes can be used with a maximum spacing and relatively large dimensions without endangering the thermal and electrodynamic effectiveness while a large number of secondary electrodes are operable with currents of lesser intensity and may be of smaller dimensions whereby a more rapid deionization can occur.

According to a further feature of this invention, as is particularly desirable for the synchronization of the system as previously described, the secondary electrodes are provided above constrictions in the outlet cross-section of the primary chamber so that a throttling of the gas flow is effected and high intensity breakage arcs are prevented from prematurely entering the secondary chamber. This constriction also increases the gas velocity through the secondary chamber and facilitates the final quenching of the arc.

I have found it advantageous to provide in the narrow gap or throat of the throttling aperture a body of a heatresistant, insulating material which may be formed as a refractory cement for holding the secondary electrode in place and which resists premature passage of the primary discharge until the null-region of its sinusoidal wave form is reached and prevents damage to this secondary plate in this region of high thermal stress.

Brief description of the views of the drawing The above and other objects, features and advantages of the present invention will become more, readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is an elevational view of a group of plates in an arc-splitting arrangement, in accordance with the present invention, adapted to be used with high-power circuit-breaker mechanisms in the usual manner, the primary front plate of the assembly being removed to reveal the underlying secondary plate;

FIG. 1A is a perspective view diagrammatically illustrating the relationship between a pair of primary electrodes of one are duct and the related secondary electrodes and plate, the members of this portion of the assembly being shown with exaggerated spacing and represented in a stylized form;

FIG. 2 is a cross-sectional view taken generally along the line IIII of FIG. 1 with the plates of one spark duct separated to indicate details of their configurations;

FIG. 3 is a cross-sectional view taken generally along the line III-HI of FIG. 1, with the plates in their separated condition corresponding to FIG. 2.

FIG. 3A is a cross-sectional view along the line III-III, of this portion of the apparatus, with the plates properly positioned;

FIG. 4 is a view similar to FIG. 1 of another arcdivider assembly wherein the primary electrodes have a modified configuration;

FIG. 5 is a view similar to FIG. 1 of a system in which the primary electrodes have upwardly extending longitudinal portions and bent members co-operating with the secondary electrodes, according to this invention;

FIG. 6 is another elevational view with the front primary plate removed, corresponding to FIG. 1 of an arc-splitting arrangement in which the secondary electrode has a modified configuration;

FIG. 7 is an elevational view corresponding to FIG. 1 of a system whose secondary electrodes have still other configurations;

FIG. 8 is an elevational view of a secondary plate of one arc chute of a splitting arrangement having an inclined throttling slot; and

FIG. 9 is an elevational view of another secondary plate adapted to be mounted upon the assembly of FIG. 8 or to be used in conjunction therewith.

Specific description In FIGS. 1, 1A, 2, 3 and 3A, 1 show one are chute of an arc-splitter arrangement having a plurality of such arc chutes in horizontally stacked or cascade arrangement. It will be understood that this arrangement is designed to be substituted for any conventional arc-splitting arrangement having upwardly extending arc chutes and a multiplicity of electrodes across which the circuit-breaking arc is distributed and which are adapted to propagate the arc upwardly in forced or convected air streams with eventual break-off of the secondary arcs. The system maybe used with any conventional breaker mechanism in which the current-input and current-output terminals may be bridged by a movable contact via any actuating mechanism and the assembly of arc-splitting primary electrodes is connected at its ends with the operating terminals or contacts of the circuit-opening mechanism. Consequently, the circuit-breaking spark, which would normally extend between the operating contacts, is transferred to the primary arc-splitting electrode array and is there subdivided into a multiplicity of smaller arcs, each jumping between a pair of such primary arc-splitting electrodes through an air space. The actuating mechanism and the method of connecting the arc-splitter thereto may be, as indicated, of a conventional type, e.g. see Standard Handbook =for Electrical Engineers, Knowlton, Ninth Edition, McGraw-Hill Publishing Company, New York, 1957, pages 1011-1025 and 1026K. While only one pair of primary electrodes and the related secondary plates and electrodes will be described in connection with each of the specific embodiments illustrated, it will be understood that each pair of primary plates forms a respective air space across which a respective arc may jump between the primary electrodes. The primary plate-s will in general, be stacked, with each supporting a pair of electrically connected primary electrodes which are exposed to the air spaces on either side of the primary plate, while respective secondary plates are sandwiched between the primary plates and subdivide the arc chutes or air spaces of each pair of them.

Thus, a pair of primary plates 1 are disposed in mutually parallel, spaced-apart horizontally-stacked relationship and define between them respective air chutes which are represented generally at In. The plates 1 are composed of a heat-resistant, electrically insulating material and have relatively thick central portions 1b which subdivide the air chute into a lower primary arc chamber and an upper secondary arc chamber at the upper and lower ends 10 and 1d of each plate. These chambers are separated by a constriction which limits upward movement of high-energy fat arcs. Each plate 1 carries, moreover, a pair of primary arc-splitting horns or primary electrodes designated at 2. The primary electrodes 2, in this embodiment, each have a pair of flat lobes or leaves 2a and 2b which extend parallel to one another on opposite sides of the lower portion 1d of the respective primary plate 1 and are connected electrically and mechanically by a. bight 2c extending along the lower end of each plate 1 through a gap 16 in a marginal rim 5a provided along the bottom portion of each plate 1. Thus 'the lobes. 2a and 2b of each electrode 2 are exposed to the gas space in one of the arc chutes 1a, etc. In the system illustrated in FIGS. 1 through 3, the lobes 2a and 2b of each pair of mechanically and electrically connected primary electrodes 2 have downwardly inclined edges 2d which cross the vertical median plane of symmetry P through the arrangement so that the edges 2d and 2d of the lobes 2a and 2b of each pair of electrodes in the respective arc chute 1a and generate a respective relatively fat and elrliergetic spark discharge S across the airgap between t em.

According to the principles of this invention, between each pair of successive primary plates 1, a secondary plate 3 of heat-resistant electrically insulating material is interposed, the primary and secondary plates being mutually parallel. The secondary plates 3 (see FIGS. 1 through 3) subdivide the arc chutes 1a between the pair of primary plates 1 and carry a secondary horn or secondary electrode 4 whose structural function will become more apparent hereinafter. As previously indicated, the plates 1 and 3 illustrated in FIGS. 2 and 3 are spaced apart somewhat while, in FIG. 1, the foremost primary plate 1 has been removed. In FIG. 3A, it is possible to see the plate assembly when the primary and secondary plates are properly positioned whereas FIG. 1A illustrates the relationship of the primary electrodes 2 and the secondary electrodes 4 during the spark-splitting operation. By removing the foremost primary plate in the illustration of FIG. 1, the forward half or lobe 4a of the secondary electrode 4 has been made completely visible. Thus the secondary electrode 4 comprises a pair of lobes 4a and 4b which are of a smaller dimension then the primary electrodes and extend laterally of the vertical median plane P on opposite sides of the thickened central portion of the secondary plate 3 and are interconnected by a web 4c extending through this plate in the plane P. The lobes 4a and 4b of the secondary electrode 4, like the lobes 2a and 2b of each primary electrode 2, are generally planar and lie in respective planes parallel to the plates 1 and 3 and to each other. The primary and secondary plates 1 and 3 are provided along their vertical longitudinal edges with spacing rims 5 integral with the plates and with a bottom rim 5a which is split by an opening 5b through which the bight portion 2c of the primary electrodes extends. The split in the secondary plates 3 is unoccupied. The rims 5 sealingly engage the adjoining plates to form generally flat outlet ducts 0r chutes 6 which open upwardly and contain a flame protector or shield 7 or other conventional cooling means for lowering the gas pressure as the gas passes through these ducts. Thus the ducts 6 may be provided at their upper end, in addition to the flame shields 7 or in place of the latter, with cooling surfaces having ribs, baflies or the like for conducting heat away from the gases and effecting an indirect heat exchange between the gas and a heat sink. The flame shields 7 are, however, metallic and have high thermal conductivity so that they also form a cooling means for the gases passing upwardly through the arc chutes or ducts 6. The rims 5 and 5a may also be provided with gaskets 5b which engage the adjacent plates 1 or 3 and thereby form a sealed conduit for the gases when the plates are horizontally stacked and brought into abutting relationship.

Each secondary plate 3 is provided with a relatively large upwardly converging wedge-shaped aperture or window whose flanks extend symmetrically on opposite sides of the median plane P and converge to a narrow gap 8 just above the primary electrodes 2. The web portion 4c of each secondary electrode 4 extends to an upper part of this gap above a plug 9 of an electrically insulating and refractory material. This plug 9 can be composed of a hardenable cementitious substance which also serves to bond the secondary electrode 4 in place in the upper portion of the narrow gap or throat 8. A suitable cementitious material for this purpose may be the refractory cement formed by mixing sodium silicate and asbestos powder to a paste and permitting the resulting cement to dry. Another cement 7 of this type is the refractory material formed by mixing barium sulfate, water glass and asbestos.

Referring now generally to FIG. 1A, the operation of the system will be readily apparent. During the period in which the current intensity remains relatively high, the fat circuit-breaking arc, because of its relatively large diameter and in spite of the blast field arising from the primary windings, is held back by the narrow gap 8 of the upwardly converging throttling slot or by the combined effect of this narrow gap and the constricted cross-section of the duct 6 with the effectiveness of this retardation being increased when the plug 9 is provided. During this period, as represented in FIG. 1A, the heavy discharge S jumps directly between the two lobes of the primary horns or electrodes 2 in the respective arc chute 1a. Thus, while the spark remains relatively fat, it can burn only over a relatively short spark length in the wide portion of the upwardly converging opening 10. In the case of alternatingcurrent circuit breakers, the current characteristic with time has a sinusoidal relationship and each current peak is followed by a passage of the current amplitude through its null value, the arc thins and is guided by the flanks of the throttle slot 10 upwardly into the throat 8 onto the secondary electrodes 4. In this manner, the discharge between each pair of primary electrodes is split into a pair of secondary discharges represented at S and S" in FIG. 1A.

In this manner it is possible to obtain a device which originally has n primary convolutions in the hypothetical solenoid, formed by the arcs and electrodes during the discharge in the primary chambers below the constriction 1b and, in the region of the null point of the sinusoidal characteristic of the intensity of breaking current with time, is transformed into 2-n arc bridges or loops and, accordingly, into 2 n convolutions of the hypothetical solenoid. Furthermore, a plurality of such intermediate plates 3 with respective secondary-electrode pairs can be provided between each primary plate and, when m such plates are employed, the hypothetical solenoid will be made up of m-n bridges or convolutions, a system which is highly satisfactory from the point of view of energy dissipation and quenching of the multiplied number of arcs formed during the final stages of the operation of the device.

According to a further feature of this invention, the transistion region between the active sections of the primary and secondary electrodes of each gas duct is constricted in the manner illustrated with the thickened portions 1b of the plates 1 and 3. In order to promote the transformation of the primary are passing through the relatively wide part 110 of the upwardly converging throttling gap 110 of a secondary plate 103, I provide electrodes 102a and 10% having projections 102 reaching beyond the constricted region 1011) of the duct 106 substantially to the region of the lobes 104a and 104b of the secondary electrode 104. The latter may be mounted in the throat 108 via a plug of refractory cement in the manner previously described. In this case, the transition between the primary arc and a pair of secondary arcs is promoted because the extensions 102' reach substantially toward the lobes of the secondary electrodes which are located on opposite sides of the vertical median plane P of the throat 108 and the slot 110. The co-operating primary and secondary lobes may, in each of the chamber partitions by the secondary plate 103, be disposed on opposite sides of this plane P although they are multiparallel and may even be coplanar, thereby ensuring a suflicient gap, however small, for the secondary arcs. At the upper or outlet end of the arc-quenching duct 106, a flame shield or cooling arrangement 107 is provided in the manner previously described. To prevent excessive restriction of the gas-throughflow opening by the portions 102 of the primary electrodes extending into the constricted portions of the duct 106 housing the secondary electrodes 104, I prefer to make the primary-electrode extensions of limited width.

An arrangement of this type is readily apparent from FIG. 5. In this embodiment the secondary plate 203, which is provided with the upwardly converging throttling slot 210, narrow throat 208 and a pair of secondaryelectrode lobes 204a and 204k on opposite sides of the median plane P and flush along the faces of the plate 203, co-operates with primary electrode plates (not shown) whose primary-electrode lobes 202a and 20211 have the configuration described with respect to FIG. 1 but are provided with electrically conductive longitudinal extensions 213a and 213b which lie along the vertical flanks of the duct 206. The primary electrode, generally represented at 202, are in electrical contact With the longitudinal extensions 213a and 2131) which reach upwardly toward the outlet of this duct and extend into the constricted portion 206a of this duct. Each of the extensions 213a and 213b is provided with a hook-shaped finger 211a, 21112, which has a leading edge 212a, 212b approaching the active section of the respective lobe 204a and 204b on the corresponding side of the plate 203. The extensions 203a and 203b and the electrode fingers 211a, 212a and 211b, 21% are composed of a material of reduced thickness so that they form no barrier to the throughflow of gases and have a specific resistivity calculated, in view of their length, to attenuate the current flow and thereby diminish the arc intensity as the secondary arc is delivered to the secondary electrodes 204a and 204k.

In all of the aforedescribed embodiments, the secondary electrode lobes and horns have their active sections upon the side of plane P opposite the active side of the corresponding other electrode with which they form the secondary arc. This other electrode is the primaryelectrode lobe in the gas duct containing the secondary and primary lobes bridged by any secondary arc, although the use of a plurality of secondary plates between any pair of primary plates will constitute some of the secondaryelectrode lobes, the co-operating other electrodes for the purpose of this description.

It is, however, also possible and an important feature of this invention in view of the simplicity of the system, to dispose each secondary lobe and the co-operating other electrode within the respective arc chute on the same side of the median plane perpendicular to the plates and passing through this throat and slot. In FIG. 6, therefore, I show an arrangement of this type and it will be noted that the lobe 304a of the secondary electrode 304 of the secondary plate 303 co-operates with the upwardly extending portion 313a of the primary electrode 302a and that the extension 303a, which reaches into the region of the secondary electrodes 304 at the throttled duct section 306a lies on the same side of the median plane P through the slot 310 and its throat 308 as the secondary lobe 304a with which it co-operates. Behind the plate 303, the other lobe 304b of the secondary electrode 304 co-operates with the similarly disposed extension 313b of the primary electrode 302b. In FIG. 6, the primary electrode 302a forwardly of the plate 303 has been represented in solid lines for convenience of explanation although it will be understood that this lobe is carried by the primary plate which is removed here. Thus, the general form of the secondary electrode 304 is that of an isosceles triangle (which may be equilateral) and the assembly of primary-electrode extensions and secondary electrode is of H-configuration. Advantageously, the secondary electrode has shanks whose free ends 304a bend away from the region of closest approach to the extensions 313a, etc.

The H-configuration, which also is found in the system of FIG. 5, has an important advantage in that the secondary arcs climb upwardly by a J acobs-ladder effect between the free end of the extensions 313a and 313b which can be beveled outwardly at 313a and 3 13b' and the free ends 304a and 304b' of the auxiliary electrodes which diverge from the extensions 313a and 313 b. The resistance of the extensions tends to attenuate these secondary arcs as they climb upwardly because of the increasing ohmic-resistance encountered by the arc current and promoting the quenching of the arc. When it is desired to provide more than two secondary electrodes 404' upon respective secondary plates 403 between each pair of primary electrodes 402 within a particular duct 406, I prefer to use the system generally illustrated in FIG. 7 which shows a primary plate whose primary electrode 402;: is provided with an upward extension 413a of the type described in connection with FIG. 6. When this primary plate 401 is covered by the secondary plate 406 carrying the secondary electrode 404,-the upwardly converging throttling slot 410 is disposed between the partially hidden electrode lobe 402a and the foremost lobe which has been removed in this figure, but is positioned by analogy to the system of FIG. The secondary electrode 404 has a bent portion 404a beyond the; plate 403 and integral with the wing-shaped lobe 404b which overlies the front face of the plate 403. The lobe 404a has a configuration similar to that described and illustrated with respect to FIG. 6 while the front lobe 404b is constituted as illustrated in FIGS. 15. Thus the [rear lobe 404a co-operates with the extension 413a of the blast electrode 402a while the forward lobe 404b co-operates with the rearmost lobe of an identical secondary electrode upon a plate 403 (positioned in front of the plate illustrated but of a symmetrical configuration with respect to the plane P and thus as'represented in dotdash lines at 404a in this figure); Thus, two secondary plates are employed in this system between each pair of primary plates and a single primary arc is subdivided into three secondary arcs. Alternatively, the secondary plates may have the configuration illustrated in FIG. 1 and, therefore, the lobes on opposite faces of each primary plate bent in opposing directions with respect to the plate P. In this case, the stacked plates need not be mirror-symmetrical with respect to one another but may be identical. The bent portion 404a has a free arm 404a diverging from the extension 413a.

Furthermore, as represented in FIGS. 8 and 9, the arc length can be increased still further and a greater throttle effect achieved when the vertically staoked secondary plates, when a number of them are provided, have upwardly converging slots directed to opposite sides of the axis of symmetry Y-Y' and plane P through the assembly. Thus, immediately in front of the primary plate 501 of FIG. 8, which carries the primary electrode 502 whose lobe 502a has an extension 513a, there is provided the secondary plate 503' carrying the secondary electrodes 504' which have been described in greater detail in connection with FIGS. 6 and 7. The rearmost lobe 504a of this secondary electrode co-operates with the extension 513a as already described while the frontmost lobe 504 h co-operates with the lobe 504b (shown in dot-dash lines in FIG. 8) of a further secondary plate 503-" disposed forwardly of the plate shown in FIG. 8 and as illustrated in FIG. 9. The secondary plate 506 has an upwardly converging throttle slot 510' which is directed to the right of the plane P and converges in the direction of a throat 508' which is parallel to the plane P and extends from the slot 510' to the secondary electrode 504 and can be filled with a plug of refractory material as represented at 9. The next plate 503", however, has its upwardly converg ing slot 510" directed to the left of plane P and terminating in the throat 50 8", laterally offset from the throat 508, above which is disposed the secondary electrode 504 whose rearmost lobe 504b" co-o-perates with the lobe 50411 as mentioned earlier. The lobe 504a of the secondary electrode 504" overlies the forward face of the plate 503" and co-operates with the extension -13b of a primary electrode 502'b carried by the primary plate (not seen in FIG. 9) which overlies the plate 503". When the extensions 513a and -513b are composed of material having a high specific resistivity, the secondary arcs which jump between the upper ends of these extensions and the free ends of the lobes 504a" etc. diverging therefrom are rapidly quenched.

I claim:

1. In an arc-quenching arrangement for circuit breakers, switches and the like adapted to generate a circuitbreaking arc, in combination:

a plurality of horizontally stacked upright mutually parallel electrically insulating primary plates defining at least one upright primary arc-extinction chamber between them;

respective primary electrodes on each of said plates and connected in the path of said circuit-breaking arc and formed with primary-electrode lobes along faces of said plate confronting one another across said primary extinction chamber to sustain a primary arc thereacross whereby the passage of electric current across said stack generates a magnetic field inducing movement of said primary arc upwardly in said primary arc-extinction chamber;

at least one intermediate insulating plate defining a window between said primary plates at least along lower portions of said primary-electrode lobes While partitioning said chamber above said lower portions of said primary-electrode lobes into a plurality of downwardly open upright secondary arc-extinction chambers;

a secondary electrode on said intermediate plate formed with arc-splitting secondary lobes on opposite sides thereof for intercepting the rising primary arc and subdividing it into two arcs together forming at least part of a solenoid-type convolution further inducing the upward movement of said primary and secondary arcs, said secondary lobes lying above said primary lobes, said intermediate plate being formed with a throttling slot running upwardly from said window to said secondary electrode and of a width limiting the passage of said primary arc therethrough; and

an electrically insulating body received in said slot at a location spaced above said window and below said secondary electrode for preventing premature passage of the primary arc onto said secondary electrode.

2. The combination defined in claim 1, further comprising constriction means between said primary-arc chamber and said secondary-arc chambers for impeding the passage of discharges of excessively high energy into said secondary-arc chambers.

3. The combination defined in claim 2 wherein said body is composed of refractory material.

4. The combination defined in claim 2 wherein said lobes of each of said secondary plates are disposed with respect to a median plane through the respective slot toward the side of said plane at which the active region of the cooperating other electrode is located.

5. The combination defined in claim 2 wherein the lobes of the secondary electrode are disposed on the same side of a median plane through said slot.

6. The combination defined in claim 2 wherein a plurality of such intermediate plates are disposed between each pair of primary plates, and the throttling slots of the successive secondary plates between each pair of primary plates are inclined alternately in opposite directions with respect to a median plane through the plates perpendicular thereto.

7. The combination defined in claim 1 wherein each of said primary electrodes is provided with a respective extension reaching toward a respective secondary electrode for effecting a transition of each primary arc to the respective secondary arcs.

8. The combination defined in claim 7 wherein said extensions have respective specific resistivities dimensioned to attenuate the discharges emanating from them upon their application to the respective secondary electrode.

9. The combination defined in claim 7 wherein said extensions of each pair of primary electrodes form an H configuration with the respective secondary electrode.

10. The combination defined in claim 1 wherein said secondary electrode has the configuration of isosceles triangles with rounded vertices.

11. The combination defined in claim 1 wherein a plurality of such intermediate plates is provided between each pair of said primary plates, the lobes of the secondary electrodes on each side of a respective secondary chamber being positioned to one side of a median plane through the stack perpendicular to the plates from the other secondary lobe of the secondary chamber, said Window being of upwardly convergent triangular configuration, terminating in said slot.

12. The combination defined in claim 1 wherein said secondary electrode is located wholly above said primary electrodes, said primary electrodes each having lobes formed as wings on opposite sides of the respective 12 primary plate and said secondary electrode having its secondary lobes formed as unitarily connected wings on opposite sides of said intermediateplate, said secondary electrode further having a web received in said slot above said insulating body.

1/ 1959 Wood. 3/1964 Latour.

HERMAN O. JONES, Primary Examiner

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