US2365131A - Alternating current electric circuit breaker of the gas-blast type - Google Patents

Description

Dec. 12, 1944. D. F. AMER arm. 7 2,365,131

ALTE'RNATING CURRENT ELECTRIC CIRCUIT-BREAKER OF THE GAS-BLAST TYPE Filed June 16, 1941 3 Sheets-Sheet 1 7 Gas 5/037 Fig.2.

[III/[Ill I Attorney Dec. 12, 1944. AMERVETAL 2,365,131

ALTERNATING CURRENT ELECTRIC CIRCUIT-BREAKER OFTHE GAS-BLAST TYPE F'lled June 16, 1941 :5 sheets-sheet 3 V IA'IW'V Fi .5 22 .6. gl

IIIIIiII/II 1 a IIIIIVIIIVIIIIII A Y I 7 Attorney Patented Dec. 12, 1944 ALTERNATING CURRENT ELECTRIC CIR- CUIT BREAKER OF THE GAS-BLAST TYPE Donald Foster Amer and Walter Henry Webb, Newcastle-on-Tyne, England, assignors to A. Iteyrolle & Company Limited, Hebburn-on- Tyne, England, a company of Great Britain Application June 16, 1941, Serial No. 398,354 In Great Britain June 17, 1940 Glaims.

This invention relates to A. 0. electric circuitbreakers of the kind having a pair of arcing contacts, one or more nozzles associated therewith, and means whereby a blast of deionising gas is forced through the nozzle or through each nozzle to assist in extinguishing the arc which extends through the nozzle or nozzles between the two arcing contacts.

In such circuit-breakers the arc is usually drawn out by relative movement of the arcing contacts, but for efficient operation it is desirable for the parts (especially the nozzle or nozzles) to be of relatively small size, which in turn gives rise to difiiculty in cases where the normal current-carrying capacity required involves comparatively large contact surfaces.

The present invention has for its object to avoid this difficulty and at the same time to ensure increased speed and certainty of operation.

This object is achieved according to the invention by first forming the are at relatively movable arc-initiating contacts on the high pressure side of the nozzle or each nozzle, and utilising the gas-blast to transfer the are from such contacts to a position in which it extends through the nozzle between fixed arcing contacts. In this way the arc is brought into the position most favourable for are extinction by the gas-blast more quickly and certainly than would be possible if the arc were drawn out in the usual manner by relative movement between the arcing contacts themselves.

A further object of the invention is to provide a convenient practical arrangement of the arcinitiating contacts, whereby any desired normal current-carrying capacity can be readily catered for without interfering with the means provided for facilitating arc-extinction by the gas-blast.

Another object of the invention is to provide a satisfactory circuit-breaker arrangement havingtwo breaks in series, by the use of two nozzles through which the resultant are or arcs after transfer from the arc-initiating contacts extend between fix'ed arcing contacts where they can most satisfactorily be acted on by the deionising gas streams flowing through the nozzles.

Further objects of the invention will. be apparent from the appended claims and from themcompanying drawings, which show by way of example some convenient practical arrangements of circuit-breakers according to the invention. In these drawings Figure 1 shows in longitudinal section an arr'angement having a single nozzle and a lateral arc-initiating movement,

' Figure 2 is a transverse section on t -e line 2-2 of Figure 1,

Figure 3 is an end elevation of the moving arc-initiating contact in the arrangement of Figure 1,

Figure 4 is a somewhat diagrammatic longitudinal sectional view of an arrangement having two opposed nozzles with lateral arc-initiating movement.

Figure 5 illustrates in'longitu'dinal section a double break arrangement with an axial arcinitiating movement, and

Figure 6 shows a single-break arrangement with an axial arc-initiating movement.

In the arrangement of Figures 1 to 3 the circuit-breaker contacts are enclosed in a metal casingA of generally cylindrical shape with a lateral branch A for housing themoving arcinitiating contact member. For convenience of description, it will be assumed that the cylindrical casing A is mounted vertically (as shown). Just above the lateral branch A an upwardly diverging nozzle 13 of refractory insulating material is mounted in the casing, gas for the gasblast being introduced under pressure toa conduit A at the lower end of the casing (through suitable valves opened when it is desired to open the circuit-breaker), so that the gas flows upwardl through the nozzle B and is discharged from the upper end of the casing A. The gas pressure is also utilised to operate the moving arc-initiating contact member C, which is provided for the purpose with a piston C sliding in a cylinder C in the lateral branch A The moving contact C itself consists of a group of contact fingers normally projecting from the lateral branch into engagement with the sides of a rod-like contact D constituting both the fixed arc-initiating contact and one of the two fixed arcing contacts. This rod-like fixed contact D is mounted centrally in the cylindrical casing A in a bushing insulator D passing through the lower end of the casing, and its upper end D lies just below the nozzle. The upper end D is coned so as to cooperate with the nozzle B in providing a generally smooth gas-flow passage. The second fixed arcing contact E is ofstreamlined shape and is carried by a spider E just above the nozzle B, such contact bein in electrical connection through the casing A with the moving arc-initiating contact C.

Thus to open the circuit-breaker compressed gas is admitted into the casing A beneath the nozzle B, the pressure causing the moving arcinitiating contact C to be withdrawn laterally into the lateral branch A thus leaving the easing A clear for an uninterrupted gas-flow. The are is initially formed horizontally between the moving arc-initiating contact C and the rod-like contact D, the contact finger C nearest the nozzle being slightly longer than the others to act as an arcing tip. The gas blast, however, immediately blows the arc in a loop through the nozzle B until it strikes the second arcing contact E, whereby half the arc loop is short-circuited and the arc remains stabilised centrally through the nozzle B between the two arcing contacts D E. The transfer of the are from the arc-initiating contacts to the arcing contacts under the action of the gas blast takes place substantially instantaneously whilst the arc is forming, and the are thus becomes stabilised in the best positionfor arc extinction much more quickly than would be possible if the arc were drawn out by a separatim movement between the arcing contacts. It is to be noted that in the final central position of the arc, the arc root at one end is on the high pressure side of the nozzle B, where it is cooled most efiectively by the gas-blast, whilst the main length of the arc is within the nozzle and on the low pressure side thereof. The blast is applied along the arc symmetrically on all sides so as to maintain the arc in its central position, so that when the arc goes out at the current zero the whole interior of the nozzle will be effectively scavenged and deionised, thus reducing risk of re-striking to a minimum. Since there is no movement of the nozzle B and arcing contacts D E, these parts can be dimensioned to suit the ideal gas-blast conditions, the size of the nozzle being independent of the normal current-carrying capacity of the circuit-breaker. Thus the same structure is suitable for use over a wide range of current-carrying capacities, which can be fully accommodated, as required, by the addition or removal of contact fingers on the moving arc-initiating contact C. The cylindrical metal casing A may be surrounded by insulation, if desired within an outer earthed metal casing. Such outer casing may be utilised to afford a tortuous path for cooling and silencing the dis charged arc gases (as shown by way of example in the arrangement of Figure 4) The arrangement of Figure 4 differs from that of Figures 1 to 3 in that there are two nozzles each with its own gas-blast and main contacts. The two nozzles F F are in line with one another, each in the end of a cylindrical casing G or G of insulating material, and the two gas-blasts flow towards one another through the nozzles F F and discharge outwardly through the space between the nozzles. Each casing G or G is provided with a moving arc-initiating contact H or H housed in a lateral branch J or J and cooperating with a central rod-like contact K or K serving the double purpose of fixed arc-initiating contact and of arcing contact, the general arrangement of these parts (although shown only diagrammatically in Figure 4) being similar to that of Figures 1 to 3.

The two moving arc-initiating contacts H H are electrically connected together, so that the two arcs formed by separation of the arc-initiating contacts are in series with one another between the main circuit terminals, which are con nected to the central rod-like contacts K K. The two gas-blasts blow the two arcs through their respective nozzles, so that the arcs merge of an insulator N into a single are between the contacts K K This arrangement has the advantages mentioned above in connection with the arrangement of Figures 1 to 3, and also the further advantage that the arc roots at both ends of the are are in the high pressure Zones whilst the main length of the arc is in the low pressure zone.

Figure 4 also serves to show diagrammatically an outer insulating casing L surrounding the insulating casings G G and itself surrounded by an earthed metal casing L The discharged arc gases enter the space within the insulation casing L from between the two nozzles, and after passing through cooling devices L are discharged into the atmosphere at the ends of the outer casing L the tortuous path eifectively silencing the discharge of the gases.

The lower fixed arcing contact K is shown mounted on a spider K and connected through spring contacts K with the rod K which passes through the end wall to the main circuit terminal. The rod K is so mounted as to be longitudinally movable for isolating purposes, when the are between the fixed arcing contacts K K has been extinguished.

The central rod-like contact D or K or K of the foregoing arrangements may be replaced if desired by a hollow tubular contact, the gas blast flowing not only around but also through the contact. or alternatively may consist of a central rod mounted within and connected by webs to a hollow tubular contact, the central rod serving as fixed arcing contact, and the hollow tube as fixed arc-initiating contact. Such an arrangement is shown in Figure which also serves to show another modification in which the arc-initiating movement is effected in an axia direction instead of a lateral direction.

Figure 5 illustrates a circuit-breaker having two breaks in series, each break being arranged according to the invention. Thus the lower break consists of an insulating nozzle M surrounded by a metal ring M electrically connected to an enclosing metal casing N supported on the top In sliding contact with the metal ring M is a moving arc-initiating contact 0 in the form of a group of inwardly springpressed contact members, the contact 0 being movable in an axial upward direction by the action of the gas-blast on a piston O sliding in a cylinder 0 within the casing N.

In the closed position of the circuit-breaker the contact 0 also engages with a hollow tubular contact member P which constitutes the fixed arc-initiating contact and is supported at its lower end by a spider P carried by a metal fitting P on which the insulator N is carried this metal fitting carrying the main circuit terminal. Within the tubular contact member P and connected thereto by metal webs P is a central rod P constituting one of the fixed arcing contacts, the second fixed arcing contact W being in the form of a metal bar passing through the wall of the nozzle M near the low pressure end thereof into engagement with the metal ring M The gases flowing out of the nozzle M are discharged to the atmosphere through a discharge casing N which is arranged to provide a tortuous path for cooling and silencing the discharged gases and is mounted on the top of the casing N. This discharge casing N also carries conduits N for supplying the pressure gas for the gas-blast of the upper break which is carried on the top of the discharge casing.

This upper break differs from the lower break in that the tubular fixed arc-initiating contact and the rod-like fixed arcing contact within it are replaced by a single central contact member Q serving for both purposes. In other respects the parts are similar to those of the lower break and the same reference letters are used, the nozzle of the upper break being at the lower end and discharging into the same discharge casing N as the lower break.

In this arrangement the current flows normally', when the circuit-breaker is closed, from the main circuit terminal at the lower end through the fixed and moving, arc-initiating contacts P O of the lower break, and thence through the discharge casing N and the moving and fixed arcinitiating contacts 0 Q of the upper break to the other main circuit terminal which is at the top of the fixed. central contact Q. When it is desired to open the circuit-breaker, pressure gas for the two gas-blasts is supplied from the lower end and acts on the two pistons O to move the two moving arc-initiating contacts 0 away from the fixed arc-initiating contacts P and Q. The gas-blasts then act on the arcs "thus formed and blow the arcs through their respective nozzles, thus transferring them to the fixed arcing contacts P M and Q M where they are in favourable positions for extinction by the blasts, the gas-blast for the lower break flowing not only around but also through the tubular contact member P.

This arrangement may be modified, if desired, by omitting the central rod P of the lower break, the tubular contact member P then itself serving the double function of fixed arc-initiating contact and fixed arcing contact in a manner analogous to that of the rod-like contact D of Figures 1 to 3.

Again the moving arc-initiating contacts can be arranged to move in the opposite direction, that is away from the nozzles, if desired, and such an arrangement is shown for a single-break circuit-breaker in Figure 6, which also serves to show a further variant in which the group of spring contact members constitute the fixed arcinitiating contact instead of the moving contact. In the arrangement ofFi-gure 6 the insulating nozzle R is surrounded by a group of spring contact members R constituting the fixed arc-initiating contact and electrically connected both to one of the main circuit terminals R and to a fixed arcing contact R in the low pressure end of the nozzle R, whilst the moving arc-initiating contact S is in the form of a tube normally engaging with the spring contact members R but withdrawable therefrom (by the action of the gas-blast on a piston S carried by but insulated from the contact S) is a direction parallel to the axis of the nozzle R but away therefrom. The moving tubular contact S is electrically connected both to the second main circuit terminal S and to a fixed arcing contact T in the form of a rod centrally disposed within the tubular contact S.

With this arrangement, when it is desired to open the circuit-breaker, pressure gas is introduced from the lower end into the casing surrounding the contacts and acts on the piston S to effect separation of the arc-initiating contacts S R thereby drawing out the are between these contacts. The are is at once transferred by the gas-blast from these contacts to the two arcing contacts T R so that it extends axially through the nozzle R in a position favourable to extinction by the action of the gas-blast.

It will be appreciated that the foregoing arrangements have been described by way of example only and may be modified in various ways within the scope of the invention. Thus, for-example, although the arrangements have been described as mounted vertically, they may be arranged horizontally or at any desired angle. Again, instead of making the nozzle or nozzles of insulating material, it may sometimes be pref erable to make them of metal insulated from the. contacts.

What we claim as our invention and desire to secure. by Letters Patent is:

1.. An A. 0. electric circuit-breaker comprising a generally cylindrical casing, a nozzle of insulating. material fixed within the casing, means for admitting gets under pressure to one end of the. casing s that a blast of gas will flow through the nozzle, a pair of fixed arcing contacts disposed; approximately in alignment with the nozale respectively on the high and low pressure parallel to the arc gap between such contacts to break. such connection, and means whereby the gas pressure causes the movable arc-initiating contact to be withdrawn from its cooperating contact and thereby to draw out an are which is immediately transferred by the gas-blast to a position in which it extends through the nozzle between the two: fixed arcing contacts, the gasblast then acting to assist in extinguishing the arc.

2. An A. C. electric circuit-breaker as claimed in claim 1, in which the fixed arcing contact on the high pressure side of the nozzle is in the form of a rod substantially in alignment with the arc gap between the two fixed arcing contacts, and the relatively movable arc-initiating contacts are in the form of a group of spring contactmembers and a tubular .contact surrounding such rod.

3'. An A, C. electric circuit-breaker comprising. a pair of fixed arcing contacts, two fixed nozzles insulated from the arcing contacts and disposed substantially in axial alignment between the arcing contacts, arc-initiating contacts by whose separation two arcs in series respectively associated with the two nozzles are initially formed, and means whereby a blast of deionising gas is caused to flow in two gas streams towards one another through the two nozzles and to discharge outwardly between themozzles, the gas streams acting to transfer the two arcs from the arc-initiating contacts so that they merge into a single arc'extending between the two fixed arcing contacts through the two nozzles.

4. An A. C. electric circuit-breaker as claimed in claim 3, in which the arc-initiating contacts consist of two pairs of relatively movable contacts, the fixed contact of each pair being constituted by the associated fixed arcing contact, whilst the separating movement in each pair takes place in a direction lateral with respect to the arc-gap between the two fixed arcing contacts.

5. An A. C. electric circuit-breaker comprising two fixed nozzles of insulating material disposed substantially in axial alignment, means whereby a blast oi deionising gas is caused to how in two gas streams towards one another through the nozzles and to discharge outwardly between the nozzles, a fixed arcing contact on the high pressure side of each nozzle, at least' one fixed arcing contact in the low pressure zone between the nozzles, and arc-initiating contacts by whose separation two arcs are formed in series respectively on the high pressure sides of the two nozzles, the gas streams acting to transfer the two arcs from the arc-initiating contacts so that they extend respectively through the nozzles between the fixed arcing contacts.

6. An A. C. electric circuit-breaker as claimed in claim 5, in which the separating movement of the arc-initiating contacts takes place in a substantially axial direction with respect to the two nozzles.

'7. An A. C. electric circuit-breaker as claimed in claim 5, in which the arc-initiating contacts on the high pressure side of at least one of the nozzles are constituted by an axially movable group of spring contact members cooperating with a fixed tubular contact, and the associated fixed arcing contact on the high pressure side is in the form of a contact rod disposed within such tubular contact.

8.-An A. C. electric circuit-breaker comprising in combination a generally cylindrical casing having a lateral branch, a nozzle of insulating material fixed within the casing, means for admitting gas under pressure into the part of the casing where the lateral branch is situated whereby a blast of gas will flow through the nozzle, a fixed arc-initiating contact in the form of a rod-like member, a fixed arcing contact at the end of such rod-like member, means for mounting such rod-like member within the casing on the high pressure side of the nozzle with its length approximately in alignment with the axis of the nozzle, a second fixed arcing contact on the other side of the nozzle, a movable arcinitiating contact in the form of a group of spring contact members normally engaging with the rodlike member but withdrawable laterally therefrom, and means for withdrawing the movable arc-initiating contact from the fixed arc-initiating contact into the lateral branch of the casing and thereby drawing out an arc, which is immediately transferred by the gas-blast to a position in which it extends through the nozzle from one fixed arcing contact to the other, the

gas-blast then acting to assist in extinguishing the arc.

9. An A. C. electric circuit-breaker comprising in combination a nozzle, means whereby a blast of deionising fluid is carried to flow through the nozzle, a pair of fixed arcing contacts separated by an arc-gap extending in the direction of flow of the gas stream through the nozzle, relatively movable arc-initiating contacts respectively comprising a rod-like member and a group of spring contact members cooperating therewith, said rod-like member constituting one of said arcing contacts, means whereby the nozzle is insulated from the contacts, means for mounting the rod-like arc-initiating contact in substantial alignment with the arc-gap between the arcing contacts, and means for effecting separation of the arc-initiating contacts and forming the are between them, whereby the arc is transferred by the fluid blast to the arcing contacts where it is extinguished by the fluid blast flowing along and around it.

10. An A. 0. electric circuit-breaker comprising in combination a nozzle, means whereby a blast of deionising fluid is carried to flow through the nozzle, a pair of fixed arcing contacts separated by an arc-gap extending in the direction of flow of the gas stream through the nozzle, relatively movable arc-initiating contacts respectively constituted by a rod-like member and by a group of spring contact members cooperating therewith, said rod-like arc-initiating contact being hollow, a rod disposed within said last named contact and constituting one of said fixed arcing contacts, means whereby the nozzle is insulated from the contacts, means for mounting the rod-like arc-initiating contact with its length extending in substantially the same direction as the arc-gap between the arcing contacts, and means for eifecting separation of the arc-initiating contacts and forming the arc between them, whereby theatre is transferred by the fluid blast to the arcing contacts where it is extinguished by the fluid blast flowing along and around it.

DONALD FOSTER AMER. WALTER HENRY WEBB.

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