US2568381A - Circuit interrupter - Google Patents

Description

P 1951 T. E. BROWNE, JR 2,568,381

CIRCUIT INTERRUPTER Filed March 23, 1945 5 Sheets-Sheet l 4 4 Fig.2.

3 L Insulation 60s Pressure \jaurce E asure Source Fzlqd. Fig 4.

6 WITNESSES: 60 INVENTOR momdsffiroufigzfit 2242M /5 25 V Ly; V 26 Gas Prjcssur: \jalrcc P 1951 T. E. BROWNE, J 2,568,381

CIRCUIT INTERRUPTER Filed March 23, 1945 3 Sheets-Sheet 2 6a.: Pressare \fiource 'WITNESSES: lNVENTOR ATTORN EY Sept. 18, 1951 T. E. BROWNE, JR

CIRCUIT INTERRUPTER 3 Sheets-Sheet 5 Filed March 25, 1945 [a so Divergence Hnyle [77 D eyree s.

INVENTOR 760mm? Efiro M276; J)?

BY W YZ ,ATTORN E WITN ESSESZ fi/f Patented Sept. 1 8, 1951 UNITED STATES ()F F lE Thomas E. Browne, J r., ForestHills;.l%a.;.assignor to Westinghouse Electric Corporation, East v Pittsburgh,.I a., a corporation of Pennsylvania Application March 23, 1945, Serial No 584A13 100laims. (o1. zoo-15oz) Theinvention relates to: circuit interrupters in guishing structures therefor.

A; general-object of my invention is-to provide. an'improved: circuit interrupter having. improvedarc extinguishing characteristics. To achieve such-results, I provide improved'fiow conditions adjacent the drawn are including elevated pressure: onat least the discharge side of a flowdirecting structure. Preferably I employ an-orificetype interrupting structure disposed in a circulating system and provide elevated gas pressure throughout the circulating, system. 7

Another: object is to provide an improved circ-uitl interrupter in which elevated pressure is employed and in which the elevated pressure may be utilized to efiectopening, of' the contact structure.

Another object is to provide animprovedcircuit interrupter inwhich elevated pressure is employed not only to effect opening. of the contact structure, but is provided on. both the inletand-discharge sides of an orifice structure which preferably has a novel configuration, as will be more fully explainedhereinafter.

Another object is to provide an improved circuitinterrupter of the type which directs fluid,

such as oil, against the arc and to provide an improved interrupting orifice construction to properly and more effectively direct the fluid into the arc stream. Preferably elevated pressure is employed on the fluid.

Another object is to provide an improved circuit interrupter of the liquid-break type in which suitable gases for are extinction are employed. Preferably such gases are at elevated pressure sov that their tendency todissolve in the liquid is facilitated.

Another object is to provide an improved-orifice construction-in a circuit interrupter of particular dimensional proportion in conjunction with the employment of elevated pressure to more effectively direct the fluid flow against theme with a lower energy input to the fluid than has been obtained heretofore.

Further objects and advantages will readily become apparent upon a reading of the following specification'taken in conjunction with the draw-- ings, in which:

Figure 1 is a verticalsectional view through a circuit interrupter embodying my invention and shown in the closed circuit position;

Fig. 2 is a vertical sectional view of a modified type of circuit interrupter embodying my invention and shown in the closed circuit position;

Fig. 3 is a sectional View taken on the line: III-4110f Fig: 1';

Fig; t iS-f a sectional view' taken onthe line- IV-IV of Fig. 2; 7

Figs. 5. through'7 collectively illustrate a-circuit interrupter of modified construction embodying myinventionin which Figs. 6 and 7 aresectional viewstaken along the lines VI-VI and VII--VII- respectively ofzF-igsaZ and 6;

Fig. 8 shows the improved orifice construction ofmyinvention;

Fig. 9 illustrates aslightly modified type of orifice construction: embodying my. invention; and

Figs. 10 through 12 arecurves 1 illustrating the improved performance of my. invention.

Fluid circuit breakers subjected to high hydro-- static pressures will generally; contain a. consid erabl ev volume ofcompressed gas in which, due to-its compression, much mechanical energy will be stored: I

. In. order to -siinplify breaker construction and: operation,.it i s proposed thatsome offthis stored energy be usedinste'ad. ofv thatusuallyv stored in externalsprings tooperate the mechanism of the breaker, that is,., to. open its contactsto produce oil flow, or both. The following discussion taken inrconjunction. with the drawings. will illustrate some possible; ways of 'doihgthis.

Referring to the drawings and, more particularly,..t'o Fig-. 1" thereof, the reference numeral I designates a tank,- preferably of? metal, which. maybe; in this instance, at line potential. Ektending}. through the cover 2 of-' the tank I is a bushing 3? through which extends a terminal: stiid4. A- line cable .5 may; be electrically connected'to the terminal stud 41 The lower ends ofthej terminal stud ffpreferab'ly constitutes the stationary contacti of the contact construction; to. be more fully described hereinafter.

Cooperating. with the stationary contact 6' is a'movab'le Contact Tl'atche'din its closed-"position e: the bottom of the tank 1. Consequently, by utilizing the flanges H, 12 in conjunction with the use of gaskets l3, l4 fluid leakage out of the bottom l5 of the tank I is eliminated in both the fully opened and in the fully closed positions of the movable contact 1. While moving between the fully opened and fully closed positions, the movable contact 1 permits only a negligible quantity of fluid under pressure to leak past the movable contact 1 and out of the bottom [5 of the tank l. Consequently, the movable contact I is latched in its closed position by the latch 8 and is fluidoperated to its open position by the utilization of a suitable gas l6 disposed above the liquid level IT. The fluid l0 may be a suitable insulating liquid, such as oil or carbon tetrachloride.

The tank I forms two compartments l8, l9, which in the position shown in Fig. l, are men connected by conduits 2i and the valve 22. Thus, in the position of the valve 22 shown, there results intercommunication between the conipartments l8,- l9, and hence equalization of the high pressure gas 16 therein.

A conduit 23 leads out of the two-way ma netically operated valve 22 and has a pressurelimiting valve 24 provided at its open end to limit the discharge of pressure out of the compartment I B when the valve 22 is operated to its other position, not shown.

Leading into the tank I and preferably at the lower endthereof is a conduit 25 having a pressure-regulating inlet valve 26 disposed therein. The lower end of the conduit 25 leads to a compressed gas storage tank, not shown. Thus, when the pressure drops to a suitably low value within the tank I; the pressure-regulating inlet valve 26 will automatically be operated to permit gas to bubble upwardly through the liquid l0 disposed within the tank I. As will be more fully explained hereinafter, the bubbling of gas through the liquid tends to dissolve the gas therein, which may improve the arc-extinguishing characteristics of the interrupter.

Preferably the orifice construction 32 has a configuration more clearly shown in Fig. 8 of the drawings. I

The operation of the interrupter will now be explained. From the above, it will be noted that Fig. 1' is a sketch of a simple forced liquid fiow type of breaker, utilizing the principle of my invention in perhaps the simplest way. Initially the liquid levels and the gas pressures in the two compartments I8, l9 will be equal with the valve 22 in the position shown, thus permitting intercommunication between the two compartments l8, IS. The moving contact I is latched externally in the closed position shown. The breaker is operated by energizing the solenoid 28 to magnetically cause rotation of the valve 22 to its other position, not shown, in which there exists 1 communication between the conduits 2|, 23 to thereby permit an exhausting of part of the gas out of the compartment [8 to a predetermined lower pressure as limited by the pressure-limiting exhaust valve 24. Simultaneously the latch 8 is operated. Only a moderate reduction in the gas pressure above the orifice 32 will be required to cause sufiicient oil flow velocity through the orifice for arc-extinction. The tendency of the internal pressure to eject the moving contact I from the tank i will cause it to move quickly to the open position shown dotted. The pressurelimiting valve 24 is utilized to limit the pressure drop within the discharge chamber l8 to any de- 4 sired minimum, and thus also to limit the total oil displacement.

Fig. 2 shows a similar scheme in which a piston 33 is used to limit the oil displacement and also to operate the moving electrode 1. Here a smal spring 3| is used to returnthe mechanism to the closed position when valve 22 is returned to the position shown. Preferably the orifice construction 32 has a configuration more clearly shown in Fig. 8.

A differential piston arrangement might also be used to advantage with such a breaker, as shown in Figs. 5 through '7. Here the conduit 33 associated with the valve constrution 34 ex-f hausts to atmosphere. Thus, when the solenoid 35 is energi't'ed to cause downward motion of the armature 35, the valve 34 is operated to permit exhausting of the gas to atmosphere from the differential volume 31. This causes downward movement of the diiferential piston 38 to thereby cause opening of the movable contacts 1 against the return biasing action exerted by the tension spring 39. The orifice construction 32 is similarto that shown in Fig. 2. It will be observed that operation of the valve 34 to the position shown will cause equalization of presusre between the differential volume 31 and the region 40 to thereby permit the tension spring 33 to retrieve the differential piston 38 to its upward position, as shown.

The tank I is at ground potential inasmuch as an insulator supports a linkage 6| interconnecting a movable U-shaped contact 43 with the differential piston 38. Consequently, two simultaneous breaks are established, the arcs being drawn individually through two orifice constructions 32, which will be more fully described hereinafter. Preferably, a guide pin 44 secured to the movable U-shaped contact 43 guides the reciprocating vertical movement of the contact 43 throughv a boss 45 in the plate 46 as shown more clearly in Fig. 6.

As before, downward movement of the piston 38 causes oil flow upwardly through each orifice construction 32, there being sufficient clearance between the movable contacts I constituting the opposed outer ends of the U-shaped contact 43 and the orifices 32 to permit initial oil flow upwardly around the movable contacts 1 following initial downward movement of the piston 38. This is necessary to permit initial downward movement of the piston 38 to effect the drawing of the movable contacts I through the orifice constructions 32. Thus, the orifices are not plugged by the movable contacts 1. A pressure-limiting relief valve 5!] may be provided to limit gas pressure in the space 43 to a predetermined upper value.

Experiments with arcs subjected to turbulent gas flow produced, for example, by magnetically spinning an arc in an annular slot, have shown the importance of the gaseous medium in determining the arcs ability to interrupt alternatingcurrentcircuits. Even with gas motion occurring only by convection, the interrupting ability of the arc has been found to depend to a marked degree on the gas in which it has drawn. Al-

though it has not been studied to the same extent, this eifect of the gas is also undoubtedly important in the extinction of an arc in a directcurrent circuit. Experience has shown that almost any other gas medium is more favorable for the extinction of an arc than is air or nitrogen. Hydrogen and steam have been found to be especially favorable and carbon dioxide, oXygen, and helium have been found comparatively favorable (compared with air).

The high interrupting ability of an are drawn under oil or water is believed to be due, in part, to the more favorable atmosphere existing within the gas bubble surrounding the submerged arc. This gas, resulting from evaporation and dissociation of the oil or water is known to be composed quite largely of hydrogen or hydrogencontaining steam. In this case or" oil, the bubble gas also contains hydrocarbon gases such as acetylene. The rate of generation of gas by the action of the are under oil or water is also believed to be important in aiding its extinction by deionization resulting from cooling, dilution, and turbulence-enhanced diffusion. In some circult breakers, this gas generation serves also to cause motion of the surrounding liquid in a favorably directed way, such as through a slot or orifice surrounding containing a portion of the arc and its enveloping gas bubble. Thus, the interrupting effectiveness of a circuit breaker liquid may depend to some degree on (a) the composition of the gas generated by action of the arc, and (b) the ease or efliciency with which this gas is generated on exposure to the arc.

The gas within the arc bubble comes principally from chemical decomposition of the surrounding liquid. under the intense heat of the arc. However, some of the gas will also be produced by simple vaporization of the liquid d also by liberation of any gases physically um solved in the liquid adjacent to the bubble. Although the amount of this dissolved will normally be small, it will depend upon the affinity of the liquid for the gas and also directly on the pressure existing within a vessel containing liquid and gas in physical contact. The importance for arc extinction of the dissolved gas will be enhanced if the gas is one which has a favorable effect upon arc extinction when serving as an arc atmosphere.

A proposal of my invention is to take gases which have a favorable effect on arc-extinction, for example, hydrogen, helium, carbon dioxide, or gaseous hydrocarbons, such as acetylene, methane, propane, and the like, or mixtures of such gases, to be used as atmospheres above the liquid in enclosed liquid-type circuit breakers, such as those described in Figs. 1-7 of the drawings. These atmospheres should be especially worthwhile when used at several atmospheres static pressure, as in the elevated pressure type breakers like those described above. Thus, the entrance of the gas at the inlets 25, such as shown in Fig. 1 at the lower end of the breaker, causes a bubbling of the gas through the liquid to facilitate saturation of the liquid with the gas, especially when first filling the breaker with liquid and gas.

The presence of the dissolved gas in the liquid acts to (a) help control the content of the arc atmosphere and (b) augment the gas generated per unit of are energy expended. The latter will be true because liberation of the dissolved gas will occur at far lower temperature and with the addition of far less heat than is required for chemical decomposition of the liquid or even for boiling it. Thus, gas will be released from a volume of liquid appreciably greater than that actually vaporized by the arc since this volume will include that immediately adjacent to the arc bubble and heated by conduction and radiation to a temperature less than the boiling point. This greater efficiency of gas generation should,

in general, shorten the arcing time at an inter" ruption and so reduce the consumption and pollution of the liquid with the result that the breaker will require less servicing. The improved interrupting efficiency will also lessen the velocity and total volume of oil displacement through the orifice required for an interruption and so aid in the design of the breaker, or alternately, increase its factor of safety. The use of nonoxygen-containing atmospheres will also reduce or eliminate the fire hazard from possible sec-' ondary gas explosion above the liquid.

Evidence of the possible importance of the dissolved gas in the interrupting liquid appeared in tests with an elevated pressure oil-flow interrupter acting upon a l250-ampere arc in a 13,800 volt, -cycle circuit of near zero power factor. With an elevated pressure of only four atmospheres absolute due to compressed nitrogen gas above the oil, interruptions would often occur with no displacement of the oil driving piston whatsoever. The orifice diameter was 0.4 inch and the maximum electrode separation only onehalf inch. Interruption was evidently due t oil and gas flow through the orifice resulting from gas generation in the closed liquid space on the upstream side of the orifice. The evidence of the gas efiect arose from the fact that such operations generally occurred only after the oil near the orifice had been exposed to arc-generated gas by preliminary arcing tests and only when pressure was left on the oil between tests. Such no flow interruptions never occurred when the gas pressure was released and the oil flushed between operations. The indication thus was that such interruptions of abnormally high efficiency were due to arc-generated gas dissolved in the oil and retained there by maintenance of pressure.

Tests have shown that the improvement in interrupting efiiciency (kva. interrupted per unit of fluid driving power) resulting from use of elevated hydrostatic pressure can be fully realized only in flow interrupters properly designed for a this condition.

The essential requirements for such a high efficiency fluid flow circuit interrupter have been found to be that:

1. The are region must be maintained at an elevated pressure by static means distinct from the fiuid driving means.

2. There must be sufiicient radial fluid velocity to reduce the minimum section of the arc path (heated and ionized gas space) to a small value near current zero.

3. The shape of the flow channel must be such that the fluid fiow is opposed as little as possible by are generated gas pressure.

The important features of an orifice designed in accordance with requirement (3) are:

(a) The are is drawn at the main constriction of the orifice with as little of the arc length as possible on the intake side of the constriction, consistent with requirement (2) for adequate flow into the arc space.

(b) The discharge side of the orifice (beyond the constriction) is made to diverge'in such a manner that the freest possible venting of the arc gases is accomplished.

A long continued basic study has been made of alternating-current arc-extinction in oil and water flow circuit interrupters, using high speed photography as well as controlled interrupting tests. This study has led consistently to the view, supported also by theoretical analysis, that arc-extinction under flowing liquids normally i esults (at a current zero) from recovery of high dielectric strength by the gas within the arc bubble. The rapid recovery of such high dielectric strength by are bubbles at current zero is attributed to:

1. Rapid deionization and cooling of the gas resulting from (a) Constriction of the bubble by the flow, and

(b) Diffusion processes greatly accelerated by intensely turbulent gas flow, as well as by the constriction, combined with 2. High gas density resulting from (a) Cooling by the same diffusion processes and (b) Compression by application to the bubble of part of the pressure head producing the fluid velocity or by elevated static Pressure.

A few experimental results are given below leading to these concepts, as are results indicating that reductions in required fluid driving power by factors of or more are possible when elevated static pressure is used. Tentative design rules are suggested for efficient orifice arrangements utilizing elevated pressure.

This study of alternating-current arc-extinction in oil flow circuit breaker devices has brought more complete knowledge of the interrelated roles of fluid velocity and fluid pressure in the interrupting process. Part of my inven tion is concerned with setting forth newly formulated design principles guided by these findings, and experimental results show that interrupting efficiency (kva. interrupted per unit of fluid driving power) can be increased ten or more times by using superimposed hydrostatic .pressure in accordance with the principles set forth below.

In successful breakers, the arc bubble at current zero is reduced to a small section over some of its length and both heat and ionization diffuse from it to the nearby bubble walls at a rate tremendously accelerated by the highly turbulent flow of the gas being vented from the bubble. The quickly approached ultimate dielectric strength of this gas space is, in successful forced fiow breakers, always raised by hydrostatic pressure to the same order of magnitude as the dielectric strength of the liquid insulating medium. Hence, with normal circuits, the time at which ultimate displacement of the gas bubble by the insulating liquid occurs is not critical for are extinction and so need bear no direct relation to the circuit voltage recovery rate. The flow problem becomes one, not of displacing the arc bubble, but simply of reducing the bubble section to a small value near current zero while at the same time maintaining adequate hydrostatic pressure on it.

The following discussion sets forth those results which have contributed directly to a better understanding of the roles of fluid velocity and pressure and of their effective utilization for are extinction. In general, critical values of oil velocity (only oil was used in the experiments to be described) were determined for any set of conditions by a series of tests in which the oil-driving pressure was varied until the minimum values at which the arc would be extinguished after one or two half-cycles were approximately found. The oil velocity during this test was calculated either from the oscillograph-recorded velocity of the oildriving piston or from the pressure drop through the orifice, also recorded on the oscillogram by means of a special electromagnetic pressure telemeter. Only steady-state values following the arcing were used.

Curve 5! of Fig. 11 shows results of some tests in which oil velocity and pressure in the orifice shown in Fig. 8 were controlled independently. The dependence upon pressure of the critical oil velocity for interruption of 1250 amperes at 13,800 volts is shown to be very marked. The distance S between the top of the lower stationary electrode 58 and the horizontal or radially inwardly extending plane portion 59 was inch. The separation between the electrodes in the fully open circuit position shown was either inch, as shown in Fig. 8, or Q inch, and both electrodes had a inch diameter. The diameter of the constriction of the orifice was 0.4 inch. The flow was as indicated by the arrows in Fig. 8.

The reason for using the 0.1-inch value of S in obtaining the data of curve 51 of Fig. 11 is revealed by the curves 62, 63 of Fig. 12. In the tests represented there, the open position of the upper (discharge-side) electrode was held con stant, and the spacing of the lower electrode below the orifice constriction was varied. A sharp minimum in oil velocity, as represented by curve 62, and driving power, as represented by curve 63 in Fig. 3, may be seen to exist at or near the spacing of 0.1 inch.

It will be noted that the curve 62 designates the required oil velocity for arc extinction, and that the curve 63 of Fig. 12 designates the corresponding power ratio" curve, giving the ratio of required mechanical oil-driving power to the kva. capacity of the circuit being interrupted. Since the reciprocal of this ratio may be thought of as a kind of efficiency for a forced oil flow interrupter, the power ratio so defined serves as an interesting basis of comparison for various interrupting arrangements. Convenient units are inch pounds per half-cycle per thousand kva.

Another condition found to be important for obtaining maximum efficiency is the shape of the orifice beyond the constriction. Fig. 9 shows an orifice arrangement having the shape on the discharge side of the orifice constriction of such configuration that there exists more of a longitudinal length 84. This smoothly expanding orifice gave practically as good results as the orifice construction of the type shown in Fig. 8. However, an orifice having a concave discharge shape beyond the constriction was not satisfactory, probably because there was too much expansion of the flow channel beyond the constriction which tends to make probable the formation of vortices, or eddies, at the orifice edge. The eddies would trap masses of gas bubbles, and carbonized oil, which would tend to lower the dielectric strength of the interelectrode space unless somehow nullifled in effect by a greater flow velocity. Photographs of arcs in simple orifices have actually revealed such ring-shaped vortices rising periodically from the discharge side orifice edge.

As a further investigation of the effect of orifice shape at elevated pressure, the tests illustrated by Fig. 10 were conducted. The divergence of flare angle 0, measured axially, as indicated in Fig. 8, of an orifice of the type as shown in Fig. 8 was varied, and also found to have a considerable effect on the necessary oil velocity for are extinction. The curve 65 of Fig. 10 shows that the most efficient value for the divergence angle 0 lies between 30 and 45, not far from the 40 value. It is thought that this value represents a compromise between the requirements for noeddy formation on the one hand, and freest possible venting of the arc gases on the other. At very small divergence angles, are photographs show large backing up of arc gas in front of the orifice constriction. The expulsion of this backed up gas was undoubtedly what required the higher oil-driving pressure represented here by the higher resulting oil velocities at small angles. Too large flare angles also undoubtedly were unsatisfactory, as explained above, in that they encouraged eddy formation in the electrically-s'tressed region, again requiring higher oil velocities to counteract their effect.

Experiments such as cited in the foregoing, show that the problem of extinguishing an alternating-current power are by means of a flowing liquid dielectric, such as oil, is essentially the mechanical problem of properly directing the fluid fiow in the vicinity of the arc. This problem should be approached as one of so arranging the flow that (a) the arc bubble is sharply reduced in section near current zero, and (b) an adequate amount of hydrostatic pressure is applied to it.

The theory that is proposed in my invention suggests that it is unnecessary to depend on the same means, the fluid driving mechanism, for accomplishing both objectives (a) and (b), but that they can to advantage be accomplished separately. By actual experiment, it has been shown that, if pressure is maintained on the arc bubble by non-energy-requiring static means, such as raising the gas pressure on the whole system to the necessary value, the control of the bubble size can be accomplished, with a suitably designed orifice arrangement, by far less expenditure of energy than has hitherto been found to be necessary.

Thus, the essential requirements for a. high efliciency liquid flow circuit interrupting arrangement are:

I. The arc region must be maintained at an elevated pressure by a static means.

II. There must be suiiic'ient radial fluid velocity to reduce the minimum arc bubble section to a small value near current zero.

III. The shape of the flow channel must be such that the liquid flow is opposed as little as possible by arc-generated gas pressure.

The separate role of the driving pressure used to obtain the velocity has seldom been recognized. Thus, the important result of my discovery has been that if both requirements I and III are satisfled, requirement II can be met with far greater ease, in terms of mechanical effort needed, than has hitherto been supposed.

The following rules for the design of efiicient orifice flow circuit interrupting arrangements may be stated as follows:

1. Orifice shape:

(a) The orifice should have its constriction sharply at the entrance.

(b) The discharge side of the orifice should be I so shaped that free gas expansion is facilitated but eddy formation near the constriction is prevented. For this purpose a 30' to 45 degree cone has been found to be better than conical surfaces of greater or smaller divergence.

2. Electrode position:

(a) The length of are on the intake side of the constriction should be limited to the minimum necessary for getting sufficient oil into the arc space. This means that the influx or inlet area provided by the electrode-orifice separation should not be greater than the orifice area. For circular orifices and cylindrical electrodes of the same diameter, the orifice-electrode spacing on the intake side should be one-fourth the orifice diameter or less. In other words, the orifice area is The cylindrical influx or inlet area between the orifice and outer edge of the fiat electrode tip is 1rDS. Since S is made equal to the two areas are hence equal.

(b) The exit-side electrode in its open position should clear the arc region near the constriction but greater separation than this is of little benefit for interruption. For plain cylindrical butt contacts and a -degree conical orifice the separation should be at least one orifice diameter but need not exceed two diameters.

3. Orifice size: The orifice area should be only as large as necessary for enicient interruption of the maximum currents to be handled.

4. Orifice material: The orifice surface should retain its dielectric strength in the presence of the are. This practically requires that the orilice be made of a non-refractory gasforming material such as fiber. The gaseous decompositi'on products from fiber may also have a favorable effect on arc-extinction.

5. Pressure: The optimum hydrostatic pressure in the arc space appears to be around 10 or' 15 atmospheres. With a properly designed orifice, the efliciency increases rapidly with pressure up to this range and falls ofi slowly beyond it.

According to the picture of arc-extinction as presented above, minimum fluid velocities for arc-extinction may be determined under various conditions by any one of three critical requirements:

A. Prevention of growth of the gas bubble. Such a bubble always surrounds the are up to and during the critical current zero period. Below some minimum velocity, it becomes exce sively large.

B. Deionization and cooling of the arc path within this bubble.

0. Elevation of dielectric strength of the deionized bubble gas.

The usefulness of statically superimposed pressure in helping to meet requirements A and C most efliciently may be theoretically explained by formulas developed from these concepts. The observed effects of variations in arc length below the orifice and in current magnitude may be similarly explained.

From the preceding curves, considerable factual information has been presented about the relations between the limiting values for areextinction of various independently controllable variables such as fluid velocity, static pressure, orifice size and shape, and electrode shape and position. There are presented above tentative design rules based on these observed relations. The more detailed rules for efficient flow-produced extinction could be summarized in the fol lowing two general requirements:

A. Sulficient radial fluid velocity must be maintained, in spite of the opposing action of arc-generated gas pressure, to reduce the minimum are bubble diameter to a small value near current zero.

B. The are bubble must be subjected to several-atmosphere pressures by static means.

The need for the first requirement might seem fairly obvious. It was shown, however, that it could be met with far greater ease than hitherto supposed if the second requirement were also met, especially if the orifice arrangement were specifically designed for use with elevated static pressure. With the orifices so designed, moderate currents (1,000 or 2,000 amperes) could be interrupted with extremely small ratios of oil driving power to circuit kva. Even at fairly high currents, very considerable improvement in efficiency of flow-produced interruption can be achieved by the use of superimposed pressure.

From the foregoing description, it will be apparent that I have invented an improved circuit interrupter of the liquid break type, which may include either interrupters of the oil break type or water break type. Also, it will be noted that I have disclosed improved orifice structure dimensions utilized in conjunction with the elevated gas pressure of at least several atmospheres. Furthermore, I have disclosed the bubbling of suitable arc extinguishing gases into the liquid to facilitate their dissolving therein to more readily bring about arc extinction.

From the above, it will also be apparent that I have provided improved operating arrangements for more easily utilizing the concepts of my invention.

Although, I have shown and described specific structures it is to be clearly understood that the same were merely for the purpose of illustration and that changes and modifications may readily be made therein by those skilled in the art Without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In a circuit interrupter of the fluid blast type, means defining an insulating orifice having a radially inwardly extending plane portion on the inlet side thereof and a sharply flared exhaust portion on the outlet side thereof, contact means for drawing an are through the insulating orifice, the inlet side contact having a final separation distance from the orifice constriction of substantially one-fourth the orifice diameter, means for forcing fluid through the orifice from the inlet to the outlet sides thereof to effect ex tinction of the arc, and means for producing at least several atmospheres gas pressure on the discharge side of the orifice.

2. In a circuit interrupter of the fluid blast type, means defining an insulating orifice having a radially inwardly extending plane portion on the inlet side thereof and a sharply flared exhaust portion on the outlet side thereof, contact means for drawing an are through the insulating orifice, the inlet side contact having a final separation distance from the orifice constriction of substantially one-fourth the orifice diameter, the discharge side of the orifice having substantially a 40 flare angle measured axially, means for forcing fluid through the orifice from the inlet to the outlet sides thereof to effect extinction of the arc, and means for producing at least several atmospheres gas pressure on the discharge side of the orifice.

3. In a circuit interrupter, means for establishing an arc, means causing a flow of are extinguishing liquid to effect extinction of the arc, and means providing the bubbling of a hydrocarbon gas into the liquid to collect above the liquid level.

4. In a circuit interrupter of the liquid break type, means for establishing an arc within an arc extinguishing liquid, and means for providing the bubbling of a hydrocarbon gas into the arc extinguishing liquid to collect at elevated pressure above the liquid level.

5. In a circuit interrupter of the liquid break type, a tank containing liquid, means for producing elevated gasv pressure on top of the liquid level within the tank, contact structure for establishing an arc, a piston for forcing liquid against the arc to effect the extinction thereof, a linkage interconnecting the piston and the contact structure, and means utilizing the elevated gas pressure within the tank to effect opening movement of the piston to thereby force liquid against the arc.

6. In a circuit interrupter of the liquid break type, means for maintaining elevated gas pressure on top of the liquid level, contact structure for establishing an arc, a differential piston for moving liquid against the arc, a linkage interconnecting the differential piston and the contact structure, and means utilizing the elevated gas pressure to effect opening movement of the differential piston for moving liquid against the arc to effect the extinction thereof.

'7. In a circuit interrupter, means defining an orifice, a stationary contact, a movable contact separable from the stationary contact through the orifice to draw an arc therethrough, means for establishing elevated gas pressure above the liquid level, means utilizing the elevated gas pressure to force liquid through the orifice to effect extinction of the arc, and means for unlatching the movable contact to permit the gas pressure to cause separation of the movable contact from the stationary contact during the opening operation.

8. In a circuit interrupter of the liquid-break type, means defining an orifice having a radially inwardly extending plane portion on the inlet side thereof and a sharply flared exhaust portion on the outlet side thereof, contact means for drawing an are through the orifice, one of the contacts having a separation distance from the orifice of substantially one-fourth the orifice diameter, a'circulating system in which the orifice constitutes a flow constricting member, means for producing an elevated gas pressure in the system, and means for forcing liquid. at least partially around the system through the orifice structure adjacent the arc to effect the extinction of the same.

9. In a circuit interrupter of the fluid-blast type, means defining an insulating orifice having a radially inwardly extending plane portion on the inlet side thereof and a sharply flared exhaust portion on the outlet side thereof, contact means for drawing an arc through the insulating orifice, the influx area for the fluid passing through the orifice from the inlet to the outlet sides thereof being substantially the same as the cross-sectional area through the most constricted portion of the orifice, and means for producing at least several atmospheres gas pressure on the discharge side of the orifice.

10. In a circuit interrupter of the fluid-blast type, means defining an insulating orifice having a radially inwardly extending plane portion on the inlet side thereof and a sharply flared exhaust portion on the outlet side thereof, contact means for drawing an arc through the insulating orifice, the discharge side of the orifice having substantially a 40 flare angle measured axially, the inlet area on the entrance side of the orifice for the fluid passing from the inlet to the outlet sides thereof being substantially THOMAS E. BROWNE, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Hunsicker Nov. 29, 1910 Merriam Aug. 20, 1918 Charpentier Jan. 20, 1925 Rodman Mar. 29, 1927 Number I Number Name Date Kubler July 12, 1927 Wade Jan. 10, 1928 Styler Jan. 14, 1930 Whitney et a1 Aug. 22, 1933 Whitney et a1 Sept. 26, 1933 Clerc Nov. 10, 1936 Biermanns June 22, 1937 'Irencham Apr. 4, 1939 Rankin Dec. 22, 1942 Kesselring et a1. Oct. 23, 1945 Denault Nov. 20, 1945 FOREIGN PATENTS Country Date Austria Dec. 1932 Great Britain May 31, 1928

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