US2266982A - Circuit breaker - Google Patents

Description

H. MILLIKEN 2,266,982

CIRCUIT BREAKER Filed June 1, 1939 3 Sheets-Sheet l INVENTOB/ HJVHLLIKEN ATTORNEY Dec. 23, 1941. WLLIKEN 2,266,982

CIRCUIT BREAKER Filed June 1, 1939 5 Sheets-Sheet 2 FIG.4

INVENTOR ".MILLI KEN ATTORNEY Dec. 23, 1941. H. MILLIKEN 2,266,982

CIRCUIT BREAKER 3 Sheets-Sheet 3 Filed June 1, 1939 INVENTOR FIGE! H-MILLI KEN BY mam/z ATTORNEY Patented Dec. 23, 1941 UNITED STATES PATENT OFFICE cmcurr BREAKER Humphreys Millik n, Marni Royal, Quebec,

6 Cana Application June 1, 1939, Serial No. 276,888

10 Claims.

extinguishing blast.

According to one feature of the invention the .two interrupter contacts connected to the ex? ternal circuit are widely spaced to provide a relav tively great are striking distance between them;

and the long arc drawn between said contacts in the open-circuit position of the interrupter is divided into a plurality of arc loops in series which are held entirely within a relatively small length, of arc chute where the velocity and, consequently,

the arc rupturing efllciency of the insulating fluid is relatively high. The arc chute, while relatively short, is designed to ensure emcient concentration of the stream of insulating fluid along the entire length of the arc held in said chute. By this combination of features I obtain a substantial increase in the maximum voltage interrupting capacity as compared with other known types of interrupters.

Another feature, which materially increases the maximum current interrupting capacity, resides in the provision of means for efl'ectively dividing the total arc current into a plurality of arcs in multiple, each arc. being subjected to a separate blast of air within a separate arc chute forming part of a single interrupting element.

The foregoing features of the invention are useful both separately and in combination with each other as will be made clear in the following detail description of the accompanying drawings,

wherein-- Fig. 1 is a diagrammatic view of one practical embodiment of the invention.

Fig. 2 is a sectional view taken along the line 2-2 of Fig. i.

ig. 2a is a sectional viewalong the line 2a-1a of Fig. l. I

Fig. 3 is a diagrammatic view of a modified embodiment of the invention.

Fig. (is a diagrammatic view showing certain elements of Fig. 3 on an enlarged scale.

Fig. 5 is a sectional view taken along the line 8-5 of Fig. 4.

Figs. 6 to 9 inclusive are partly diagrammatic illustrations of the embodiment appearing in Figs. 3 to 5 inclusive. v

The interrupter element shown in Figs; 1 and 2 substantially comprises widely spaced contacts 5 and 6 to which the leads A and B of the external circuit are respectively connected. The gap between these contacts is normally bridged by a movable contact I which is operated to open-circuit or closed circuit position by suitable operating means such. for example, as the operating means hereinafter described in connection with Fig. 3.

A relatively great arc striking distance is provided between contacts 5 and 6 ,by mounting them in widely separated opposing walls 8 and 3 of the arc orifice I0, the, remaining walls II and II of which are spaced aparta distance only slightly greater than the thickness of the contact I. The width of the contact I along the axis Ia is equal or approximately equal to the distance between the portions of the walls 8 and 9 in which the contacts I and i are mounted. It will thus be seenthat the contact 'I is relatively wide and thin and is of such dimensions that only a relatively small clearance is left between this contact and the arc orifice walls II and II when contact 'I is in its closed-circuit position.

In Figure 1, contact I is shown in its opencircuit position. The dotted lines a, b, and c indicate successive positions to which the are drawn between contacts 5 and I is blown by the high velocity air or other insulating fluid which travels in the direction indicated by the arrows 'X.

As this arc is blown beyond position c it is divided, by the insulated arcing contact ll, into two sections d and d which are blown to the loop forming positions e and e. Similarly, the dotted lines a, b, and c indicate successive positions of the are drawn between contacts 6 and I. As this arc is blown beyond position 0 it is divided, by insulated arcing contact it, into sections d and d which are then blown to the loop forming positions e and c Contact I is streamlined in cross section (see Fig. 2a) to provide sharp leeward edge portions Ib and I0 lying at opposite sides of a central leeward notch or recess Id. Owing to this shaping of contact I the ends of the arcs which terminate on the edges 'Ib and Ic are effectively swept along these edges until they reach the recess Id where they are kept separated by the arcing points Ia and If until the arcs are extinguished by the blast after being formed into the loops e e, e, and e.

Channels it are formed in the walls II and I! so that the lower portions of these channels lie at opposite sides of notch Id, as clearly shown in Fig. 1. These channels serve to direct strong blasts of air between and beyond the arcing points 1e and If so that the adjacent arc sections e and e are prevented from coming in contact with each other.

Each of the insulated arcing contacts l3 and H comprises a series of relatively wide. and thin contact members l5 arranged with their wide faces lying parallel with the walls H and I2. As clearly shown in Fig. 2, the members l5 of each series are rigidly joined together inspaced relation by a connecting web l6 which is supported from the walls and I2. The upper edge or each member |5 is made concave to provide arcing points 5d and |5b separated by an intervening recess l5c. Channels l8, provided in the walls H and I2 at opposite sides of each of the contacts l3 and I4, serve to direct strong blasts of insulating fluid between the arcing points I50 and I5!) to prevent merging of the arc sections whose adjacent ends are held by these points. The passage of insulating fluid between the thin. closely spaced members l5 of the arcing contacts l3 and II also serves to render non-conductive the stream 01' air and are products blown from are c and between members and arcing tips 15a and |5b. The thinness and spacing of the members l5 also'eliminates any possibility of the arc sections being so sheltered at the leeconditions necessary to successful execution of this idea. It is known that the quantity of arc current which can be extinguished by directing a blast of insulating fluid against a single arc is limited by the tendency of the current to concentrate into a central core-path which is of such extremely small diameter and 0! such extremely high density of ionizationthat it is not possible to effect a corresponding concentration of the air blast in exactly the same space coincident with the current path. This knowledge has prompted the development of interrupters ward edges of these members as to interfere with effective action ofthe extinguishing fluid.

The advantages of the constructionset forth 'in the 'foregoing description will beflapparent from the following observations; It the arcing ,contacts'l3 and together with the notch 1d and arcing points is and If of contact 1 were omitted the arc drawn in the open-circuit position of the interrupter would consist of only two sections, one drawn between contacts 5 and .lOa of the orifice and intounconfined space where the velocity of the blast is so low as to have only negligible extinguishing efiect. In

this case only those portions of the arc sections lying within the arc orifice are eflectively acted on by the air blast. On the other hand, when each of the arcs initially drawn between contacts 5 and and 6 and! is'divided into loops in series as described herein the whole length of the arc is held within th arc orifice wherethe velocity and extinguishing efiect o! the blast of insulating fluid is at the maximum value. With the latter arrangement the arc extinguishing capacity obtainable with a given length of arc orifice and with a given quantity of air blast is much greater than would otherwisebe the case.

comprising two or more sets of interrupter contacts connected in multiple but without any means being provided to ensure attainment of the desired result, namely, division of the main current into a plurality of smaller arc currents inrmultiple. Such interrupters have failed of their purpose owing to the fact that it is diflicult to prevent the contacts of one set reaching an open-circuit position slightly in advance of the contactslof the remaining se'tor sets. When this occurs the current is merely shifted to the conducting paths afforded by the wt or sets of interrupter contacts which are still in closedcircuit position with the result that all thecurrent is concentrated in an arc drawn-between the contacts or the set which is opened last.

Furthermore, even it it were practically possible to simultaneously open the circuit at the points of interruption provided by several sets of interrupter contacts connected in multiple, the resulting arcs could not be maintained long enough to extinguish them separately since all the arc currents would quickly beconcentrated in a single arc carrying the entire current. This is due to unavoidable variations in the initial -relative magnitude of multiple arc-currents. The

larger arc, having the highest temperature and 40 theleast resistancatends to take more and more It may also be noted at this point that with very large currents the electromagnetic repulsion betwen adjacent arc sections is also efiectiverin maintaining equal spacing of the arc sections to prevent them merging together. Another feaa Previous proposals to divide a single current into smaller arc currents in multiple have not proven of the current until the other multiple arcs are conipletely extinguished by this diversion of ourren a Y The interrupter shown in Figs. 3, 4 and 5 is provided with means for dividing a single current into a plurality of smaller arc currents in multiple and for maintaining said multiple arc currents until they are disrupted bythe arc-extinguishing blast of air or other insulating fiuid. The manner in which this is accomplished will be clear from the followingdescription.

The contacts 5, 6 and-1 of Figs. 3, 4 and 5 correspond-to the contacts previously described in connection with Figs. .1 andz. Additional contacts 20 and 2| are mounted in the walls 8 and 9 so that they lie directly'opposite the contacts 5 and 6 and are contained in the same horizontal plane; Contact 20 is' connected to contact 5 by way of conductor 22 and contact'fl is connected to contact 6 byway of resistor 23. In the closedcircuit position of the interrupter the gap between contacts 20 and 2| is bridged by a, movable contact 24 which is a duplicate'of the movable contact I. The contacts and 24 are fastened together by a screw 25but are insulated from each other as indicated at 26, 21 and 28. These two contacts are offset about so that, during opening of the circuit breaker.-contact 1 passes out of engagement with contacts 5 and 5 slightly before contact 24 passes out of engagement with contacts 20 and 2|. This will be clear from examination of the diagrammatic illustrations of Figs. 8 and 9. 7

Contacts 1 and 24 are carried by a common opfeasible owing to inadequate realization of the erating piston 30 working in cylinder 3|. Piston escapes ill is moved into the closed circuit position shown in Fig. by air admitted to the lower end of cylinder II through supply pipe l2. To open the interrupter a blast of air is delivered to the arc oriflce or passage it through blast pipe 13. The force of the blast forces piston downwardly so that contacts 1 and 24 are shifted to the opencircuit position shown in Figs. 4 and 5.

When the interrupter is in closed-circuit position there is a normal division. of the load current between the two sets of interrupter contacts since resistor 23 is shunted by a shunt conductor 38 bridging contacts 6 and ti. This shunt conductor is held against contacts 8 and 2| by a toggle 36 when said toggle is extended as shown in Figs. 3, 4, and 6. During opening of the interrupter a blast operated trip plunger 31 is forced outwardly by the blast pressure and acts against the pivotally connected ends of the toggle levers 38 and I! to initiate collapse of toggle 36. A spring 39a assists in separating shunt conductor from contacts 6 and II during collapse of the toggle by plunger 31. As here shown plunger 31 is slidably mounted in a guide bore to so that its enlarged inner end 31a exposed to .the blast pressure in oriflce III.

In the present instance I have describeda circuit breaker designed to utilize compressed air or gas as the arc extinguishing fluid. It is ob-- vious, however, that thenovel features of the invention may also be embodied in a circuit breaker adapted to utilize a suitable liquid, such as oil, as the .arc extinguishing fluid. In the latter case the circuit breaker should, 01' course,

be designed so that the oil is discharged at high velocity through the interrupting orifices and then returned to its original container.

The lower end of toggle lever 39 is provided with a laterally extending resetting arm 40 having its free end disposed above a toggle resetting piston ll working in cylinder 42. The lower end of pipe 32 by way of branch connection ll.

After each circuit interrupting operation the interrupter is reclosedby supplying pressure fluid through'pipe 32 to return piston 30 and interrupter contacts I and 24 to closed-circuit position. A portion of the pressure fluid in pipe 32 passes through branch connection 43 and acts through piston ll and toggle arm it to reset the previously collapsed toggle 38 so that shunt conductor 35 is reengaged with contacts 8 and 2|. During opening of the interrupter, arcs A and A' are initially drawn between contacts l and 1 Y20 and II draws arcs A and A in multiple with the previously drawn arcs A andA'. In connection with the foregoing description it is assumed, for the sake of simplicity, that no change has yet taken place in the generated voltage of the external circuit and that the total current remains constant.

The arcs A and A are blown into' an arc chute L while the arcs A and A are blown into a separate arc chute L, the two chutes being separated by a partition wall M so that the arcs in each chute are subjected to a separate air blast.

In the usual case of interrupting a 60 cycle current the difference in the relative positions of contacts I and 24 will be traversed in about one-eighth of a cycle and during the remainder of the half cycle arc currents will be flowing in multiple in both interrupting circuits and both are currents will be interrupted at the first current-zero of the external circuit.

It is important to note in Figs. 4 and 5 that the partition M, separating arc chutes L and L, does not extend downwardly as far as the points at which the movable contacts 1 and 24 are actually separated from the cooperating stationary contacts during the opening operations of the interrupter. The termination of partition member M above such points is advantageous since it permits radiation of the intense heat and light rays from one arc (such as that comprising the arc sections A and A) to the adjacent arc space to ionize said space and thus assist in establishing the arc sections A and A if the latter have not already been established by the separation of contact 24 from contacts 20 and I l.

The total current undergoes a reduction when current is forced to flow through the resistor by the arcing across I, but such reduction is not the main purpose of the resistors; the main purpose cylinder 42 is connected to fluid pressure supply being to divide the total arc currentinto several paths in multiple, thereby reducing the interrupting duty imposed on any one set of contacts.

The present drawings show two interrupter elements connected in multiple but it will be understood that the same principle may be embodied in circuit-breakers in which two or more interrupting elements are connected in multiple.

Another advantage of the construction described herein is that it permits the interrupter to be closed when there is a short circuit on the system to which it is connected. The interrupter may be designed so that, during the closing operation, the contact 24 reaches closed-circuit position slightly before the contact 1, thereby dividing the total short-circuit current between the two multiple paths afforded by the two sets of interrupter contacts thus reducing burning of the contacts to a minimum. In order to further reduce burning of the contacts when closing on short circuits the interrupter may be provided with air ducts SI and nozzles 58 through which jets of compressed air are injected between the cooperating contacts of each set. These jets of air serve to increase the dielectric strength of the space between the approaching contact points of the component contacts of each set so that these contacts are, in eflect. closer together at the instant the arc strikes; and the time between striking of the arcs and. the touching of the contacts which extinguishes the current-carrying arc path) is thereby reduced. The Jets of air supplied through the nozzle have a further beneficial effect in that they tend to sweep each are away from the point of initial striking and thereby reduce the temperature of the metal and the amount-of burning.

The interrupter shown in Fig. 1 comprises a single interrupting element including the stationary contacts I and 8 and the movable contact I, whereas the interrupter shown in Figs. 3 and 4 comprises two interrupting elements in multiple, each element including a pair of stationary contacts and a cooperating movable contact. In view of this explanation the sense in which the term interrupting element" is used in the appended .claims will be readily understood. l

.In Figure 3 I have shown an air duct 51 through when a jet of the compressed air supplied to are orifice I is directed toward the contacts 6 and 2| and the cooperating shunt conductor 35. This air jet serves to increase the dielectric strength of the space which exists between the contacts 6 and 2| on the one hand and the conductor 35 on the other hand when these two sets of contacts are separated during opening of the interrupter and this permits the required motion .of the fixed contacts to be minimized.

Havingthus described my invention, what I claim is: I

- 1. In a circuit breaker in which a high velocity blast or stream of insulating fluid is utilized to efiect arc-extinction, .the combination of means forming an arc orifice, ,a' conduit for conveying the fiuid stream to'said arc orifice; said orifice, as viewed'in cross section, being relatively wide along one axis constituting the major axis and relatively narrow along an intersecting axis c0nstituting the minor axis, two opposite contacts mounted in said conduit so that their opposite surfaces are spaced apart the full width of the arc orifice measured along said major axis, a

movable contact normally bridging the gap be-' tween the opposite surfaces .of said first mentioned contacts, the transverse thickness of said movable contact being only slightly less than the width of the arc orifice as measured along said minor axis, said movable contact being tapered to provide sharp leeward edges inclined toward the axial center line of said orifice, the inner ends of'said edges terminating at opposite sides of a central notch provided in'the leeward side of said contact and channels formed in wall portions of the orifice lying at opposite sides of said notch, said channels serving to direct the arc extinguishing fiuid into said notch during operation of the interrupter to open-circuit position.

2. In a circuit breaker in which a high velocity blast or stream of insulating fluid is utilized to elfect arc extinction, the combination of means forming an arc orifice which, in cross section, is relatively wide along one axis constituting the major axis and relatively narrow along an intersecting axis constituting the minor axis, means for conveying the fluid stream to said'orifice, two opposite contacts mounted in said arc orifice so that their opposing surfaces are spaced apart the full width of the arc orifice as measured along said major axis, a movable contact normallybridging the gap between the opposing surfaces of said first named contacts and a series of insulated arc dividing conductors located in said orifice at the leeward side of the movable-contact, each of said are dividing conductors comprising a plurality of relatively wide and thin members joined together in closely spaced relation.

3. A circuit breaker as set forth in.claim 2 in which the relatively wide and thin members of each arc dividing conductor are rigidly Joined together and are arranged with their wide faces lying parallel with the major axis of the arc orifice.

4. A circuit'breaker as set forth in claim 2 in which the relatively wide and thin members of each arc dividing conductor are arranged with their wide faces lying parallel with the major axis of the arc orifice and are joined together closely spaced relation by connecting webs,

each of said members being also provided with a concave upper edge afiording arcing tips sepa-' rated by an intervening recess.

5. In a circuit breaker in which a high velocity blast or stream of insulating fiuid is utilized to efiect arc extinction, the combination of means forming an arcoorifice, a conduit of insulating material for conveying the fiuid stream to said orifice, two contacts mounted in opposite walls of said orifice so that their opposing surfaces are spaced apart, a movable contact normally arranged to bridgethe gap between the opposing surfaces of said first mentioned contacts and a pair of arc dividing conductors located in said orifice, each of said are dividing conductors'being located above and adjacent one of said first mentioned contacts and comprising a plurality of relatively wide and thin blade-like members joined together in closely spaced relation by connecting webs, each of said blade-like members being provided with a concave upper edge affording arcing tips separated by an intervening recess. 7 6. A circuit breaker as set forth in claim 5 in which the movable contact is provided with arcing tips extending in the direction of said are di'viding conductors. Y

7. In a circuit breaker in which a high. velocity blast or stream of insulating fluid is utilized to efiect arc extinction, the combination of means forming a plurality of arc orifices, a single conduit through which the fiuid stream is conveyed to each. of said orifices, two opposing contacts mounted inopposite walls of each orifice, a plurality of movable contacts, each normally bridging the gap between opposing surfaces of the contacts mounted in one of said orifices, a common operating member for operating all of said movable contacts to their circuit closing and circuit opening positions, said movable contacts being connected to said operating member in ofiset relation with respect to each other so that each movable contact engages and disengages its cooperating arc orifice contacts at a different time as compared with the companion movable contact or contacts, means for insulating. said movable contacts from' each other and an external circuit in which the several pairs of contacts mounted in the arc orifices are connected in multiple so that the total are current in said circuit is divided into a plurality of arcs in multiple in the circuit opening position of the several movable contacts.

8. A circuit breaker as set forth in claim 7 including a resistor in series with one contact of one or more of the several pairs of contacts mounted in said are orifice.

9. In a oircuitbreaker in which a high velocity blast or stream of insulating fiuid is utilized to effect are extinction, the combination of means forming a plurality of arc orifices, means for conveying the fluid stream to each of said orifices, two opposing contacts mounted in opposite walls 10. In a circuit breaker in which a high velocity blast or stream of insulating fluid is utilized to eifect are extinction, the combination of means forming a pluralityoiarc orifices, a single conduit through which the fluid stream is conveyed to each oi. said orifices, said conduit being in direct communication with all of said orifices, two opposing contacts mounted in opposite walls of each orifice, a plurality of movable contacts each normally bridging the gap between the opposing surfaces of the contacts mounted in one of said orifices, a common operating member for

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