US3017482A - Air or gas blast electric circuit breakers - Google Patents

Description

Jan. 16,1962 A. ROXBURGH ErAL 3,017,482

AIR 0R GAS BLAST ELECTRIC cmcurr BREAKERS Filed June 23, 1958 5 Sheets-Sheet 2 Jan. 16, 1962 A. ROXBURGH ,E-TAL 3,017,482

AIR 0R GAS BLAST ELECTRIC CIRCUIT BREAKERS Filed June 23, 1958 3 Sheets-Sheet 3 46 41 a .3.- 40 j 43 g l7 s ws 3 '1 [Q] 22 IL) lb 26 f7 20 I20. l5 27 29 5. wit/V7095 Q 6 45597 FOXEUAGH 4 TTOFP/VEY United States Patent O 3,017,482 AIR R GAS BLAST ELECTRIC CIRCUIT BREAKERS Albert Roxburgh, Willesden Green, London, and Albert Leigh, Kenton, Harrow, England, assignors to The British Thomson-Houston Company Limited, London, England, a British company Filed June 23, 1958, Ser. No. 743,758 Claims priority, application Great Britain July 1, 1957 5 Claims. (Cl. 200-448) This invention relates to air or gas blast circuit breakers, and particularly to such circuit breakers of the type wherein the moving contact is adapted to be separated from a co-operating contact by the application of pressur acting on said contact or a piston member coupled therewith. -It will be understood that air is a gas and that the operation of the circuit breaker described hereafter does not depend upon the chemical nature of the gas. Thus the expressions air and gas must be considered as equivalent throughout the specification, and where one is used it includes the other as driving and arc extinguishing medium, it being understood that in individual cases a gas of higher insulating quality, such as nitrogen, may be preferred to air. In a well known arrangement of circuit breaker of this type the contacts are mounted within an arc chamber to which pressure air or gas is applied by opening a blast control valve when the circuit is to be interrupted, the pressure air or gas causing separation of the contacts and an air or gas blast across the contact gap. I

In application for Letters Patent No. 692,459, now abandoned, arrangements of air or gas blast circuit breakers of the type above referred to are described wherein a piston or an equivalent member subject to the air or gas pressure and adapted to separate the contacts is connected with a moving contact by means permitting an initial lost-motion or relative movement between said member and the moving contact, whereby on application of pressure air or gas to separate the contacts said piston or like member will first be moved without causing separation of the contacts and subsequently the relative movement or lost-motion will be taken up so that further movement of the piston or like member will effect contact separation. V

Arrangements according to said application No. 692,- 4 59 provide that the piston or equivalent member will not inititate contact separation until said piston or mem-' her is moving with a velocity and momentum suificient to cause reliable separation of the contacts. The arrangements therefore overcome the disadvantage in circuit breakers of the type referred to as previously arranged in that since the moving contact has tended to separate from the co-operating contact so soon as the air or gas pressure exceeds a predetermined value corresponding with the biasing force urging the moving contact into engagement with the co-operating contact, and since the pressure requires a finite time to build up, the contacts have tended to separate under a comparatively small diflerential force so that the contact will accelerate I v 60 No. 692,459'thus enables the interrupting capacity of aonly slowly. The invention according to said application given circuit breaker to be increased.

Preferably in carrying out the arrangements according to said application No. 692,459 the mass of the piston and the degree of relative movement between said piston and the moving contact is such in relation to the rate of rise of air pressure as to cause the piston to engage with a co-operating member connected with the moving .contact with a considerable impact thereby transferring at least some of its momentum to the moving contact.

According to the present invention, in an air or gas blast circuit breaker having a moving contact normally biased by spring means or otherwise into engagement with a co-operating contact and adapted to be operated by a piston or equivalent member as in the arrangements according to the patent application aforesaid, said piston or equivalent member is provided with means such as abutment stop adapted to arrest the movement of the piston at an intermediate point in the travel of said moving contact, and meansoperative with a time delay after the engagement of said piston or equivalent member with said abutment are arranged to effect a further opening movement of said moving contact. The arrangements according to the invention provide that after the moving contact has been separated from the co-operat.- ing contact by said piston or equivalent member said moving contact will be arrested at an intermediate point in its opening movement. This point may be such that the gap between the co-operating contacts is the optimum for are extinction.

Preferably the means for efiecting the further movement of the moving contact comprise a second piston area formed by a part of the moving contact or a member connected therewith, which piston area works within a space to which pressure air is applied with a time delay after application of pressure air to the first-mentioned piston or equivalent member.

The invention has general application in air or gas blast circuit breakers of the type referred to, but is advantageously applicable in circuit breakers of the type wherein after the contacts have been opened by the air pressure in the contact chamber the exit of the pressure air from the contact chamber is closed so as to maintain pressure in said chamber without consumption of air, and thereby hold the contacts open under pressure, whereby the circuit in which the circuit breaker is included may be disconnected continuously without the openingof series isolators as are otherwise required. Ac-

cording to a further feature of the invention, for pro-- viding operation in 'the manner just above set forth, the moving contact member is formed as or is coupled with a valve member which in the-fully open position of the moving contact is adapted to close the air discharge passage from the contact chamber and thereby maintain pressure in-said chamber for holding the contacts open. According to a. further feature of the invention, theworking space for the further piston area to which pressure air is applied with a time delay in the manner hereinbefore indicated is provided, in addition, with a discharge passage communicating with the contact chamber so that release'of air pressure from said chamber will result in closing of the contacts under the force of the biasing means for the moving contact, with an additional discharge passage which is controlled by the moving contact so as to be open in the fully closed position of the moving contact but to be closed on movement of the porarily brought to rest, namely the position to which.

said contact is moved by the first-mentioned piston or equivalent member. This.arrangement provides in the closed position of the circuit breaker an air bleed to atmosphere from said working space such that on closing of the contacts any air remaining in said working space is discharged to atmosphere whereby to place the circuit breaker in immediate readiness for re-opening. Conveniently the additional discharge passage referred to is controlled by means of a port in the working space for the second mentioned piston area, such port being controlled by the peripheral surface of a member pro viding said second piston area. 7

Generally this invention resides in a gas blast circuit breaker having first and second contacts, and operating means to separate initially the first contact from the second contact and then to remove further the first contact from the second contact, wherein the said means comprises first and second driving members for causing respectively said separating motion and further removing motion, said driving members being associated respectively with first and second pressure control means which control the elfective presence of pressure gas for operating said first and second driving members. This is accomplished by arranging the contacts in a chamber and providing means forming first and second spaces in which first and second pistons operate for actuating the movable contact. Means are provided for serially admitting the pressure gas through the first space and then the second space from which it is discharged to the atmosphere. A control closing element is mechanically connected to the second contact to close the discharge when the contacts are fully separated.

More details will be seen from the accompanying drawings, in which:

FIG. 1 is a vertical sectional elevation illustrating one arrangement of circuit breaker according to the invention and arranged also in accordance with Application for Letters Patent Serial No. 743,759, now Patent No. 2,902,570, issued September 1, 1959 to which attention is hereby directed;

FIGS. 2 and 3 are sectional elevations similar to FIG. 1 but showing the circuit breaker respectively at intermediate and final stages in the contact opening operation;

FIG. 4 is a fragmentary sectional elevation corresponding with part of FIG. 1 and illustrating a modification thereof; and

FIG. 5 is a fragmentary sectional elevation corresponding with part of FIG. 1 and illustrating a modification of the latter.

The circuit breaker shown in the drawings comprises a fixed rod-like contact 1 and a co-operating movable contact 2 of tubular form arranged within a tubular insulating housing 3. At its right hand end in the figures the housing 3 is secured to a metal supporting structure 4 in which thecontact 1 is fixed. The structure 4 includes internal passages 5 whereby an entry port 6 in said structure is placed in communication with the interior of the housing 3. As FIG. 1 shows, the circuit breaker may be of the otherwise known symmetrical double-break type wherein a second tubular housing partly shown at 3A is also mounted on the structure 4 and encloses a fixed contact 1A with which co-operates a moving contact (not shown) similar to the contact 2 and having in association therewith similar means as hereinafter to be described for the contact 2. The structure 4 may be mounted at the upper end of a vertical insulating colum as is well known per se for air blast circuit breakers. This vertical insulating column is of tubular construction providing a through passage in alignment with the entry port 6 and is connected at its foot with an air conduit adapted to be 'connected by means of a main control valve with an air pressure reservoir. Furthermore, valve means are provided whereby the foot of said insulating column may be placed in direct communication with atmosphere for operation of the circuit breaker in'the manner hereinafter to be described.

A control valve is provided for admitting pressure air to the circuit breaker and for discharging the air from the circuit breaker to atmosphere. This valve may be of a known construction, does not form part of the invention and therefore is not shown.

The tubular moving contact 2 extends through a fixed tubular member 7 having an in-turned end 8 serving to guide the adjacent end of the contact 2. The tubular member 7 is formed with a flange 9 which by means of a clamping ring 10 and suitable studs or the like is rigidly secured to the end of the insulating housing 3 remote from the structure 4.

At its end remote from the fixed contact 1 the moving contact has an enlarged diameter portion providing a piston 11 which works Within a space provided by a cylinder 12 of a metal assembly 13, having a flange 14 which is secured to the flange 9 and clamping ring 10, such as by studs 15 and nuts. The cylinder 12 is provided with an end cover 16 secured in place such as by studs and nuts 17, said end cover being provided with a central. air discharge port 18 and an external discharge passage 19.

The moving contact '2 is urged into engagement with the fixed contact 1 by means of a compressing spring 20. The piston part 11 of the moving contact includes a central surface 21 having an annular groove in which is located a sealing gasket 22 adapted as will hereinafter be described to engage with an annular seating 23 surrounding the port 18. A plurality of ports, such as 24, are provided within the piston 11 for allowing passage of air during operation as will hereinafter be described. The cylinder 12 includes a portion of reduced diameter providing a further space or cylinder 25 in which works a piston 26. The piston 26 includes a trunk 27 slidable within the tubular member 7. For a purpose which will hereinafter appear, ports, such as 28, are formed in the flange 9 for admitting pressure air from the housing 3 to the face of the piston '26. Ports are provided, such as at 29, in the tubular member 7 for admitting such pressure air to the interior of the cylinder 12, it being observed that a substantial annular clearance is provided between the piston trunk 27 and the moving contact 2. The piston portion 11 of the moving contact includes an annular flange 30 which is adapted to be engaged by the left hand face of the piston 26. Preferably an annular rubber or other cushion 31 is carried by the piston 26 for providing a resilient engagement between said piston and the flange 30. A light compression spring is provided at 32 so as to tend to move the piston 26 away from the flange 30.

For a purpose which will also hereinafter appear a port 12a is provided in the cylinder 12.

The contact 2 may be connected electrically with the assembly 13 by means of a resilient sliding contact assembly or garter spring of any suitable construction indicated diagrammatically at 33.

The circuit breaker illustrated also includes means in accordance with application Serial No. 743,759 aforesaid as will now be described.

The cylinder 12 is formed with a lateral extension or antecharnber 36 enclosing a lever 37 which is mounted on a fixed pin 38. At its free end the lever 37 has a pin connection 39 with an actuating member fora movable auxiliary contact 40 which is slidably located for axial movement in a guide member 41 secured to the wall of the antechamber 36. The contact 40 and a cooperating fixed auxiliary contact 42 are located within a tubular insulating housing 43 closed at its upper end by a cover plate 44 but in communication with the antechamber 36 by Way of ports such as 45 in the member 41. The auxiliary contact 42 is connected with one end of a resistor,

.shown diagrammatically at 46, the other end of which resistor is connected with the assembly 4. In the case of a symmetrical double-break circuit breaker such as indicated by FIG. 1 the assembly at the right hand end of the circuit breaker may be arranged similarly to that shown forthe left hand end in FIG. 1, a second resistor being partly shown at 46A.

The contact 40 carries an. abutment disc 48 between which and the upper'end of the member 45 a compression spring 47 acts to tend to move said contact downwardiy. The connection between the lever 37 and the contact 40 is effected by means of a further compression spring 49 acting between the disc 48 and an abutment disc 50 having the pin joint at 39 with said lever. The arrangement comprises an elongated spigot 51 which has telescopic engagement with an axial bore in the lower end of the contact 40. g

A roller 52 rotatably carried by the lever 37 engages with the piston portion 11 of the main moving contact. The arrangement is such that when the roller 52 is engaged by the peripheral surface of said piston portion as shown in FIG.1 the lever 37 will be positioned so as to maintain the contact 40 in engagement with its co-operating contact '42.

FIG. 1 illustrates the position of the movable parts when the circuit breaker is in its closed condition. In order to open the circuit breaker the control valve referred to is operated to admit pressure air from the reservoir to the housings 3 and 3A. This pressure air flows through the ports 28 so as to move the piston 26 outwardly in its cylinder. The piston 26 is permitted a predetermined distance of free travel before the cushion 31 engages with the flange 30. On engagement of the cushion 31 with the flange 30 the moving contact member is subjected to an impact due to the kinetic energy possessed by the-piston126 and its trunk 27. The arrangement is such that when the moving piston 26 impacts upon the seating 30 it has already gathered up speed and inertia so that thezcompression spring 20 is no longer able to maintain the end 2 of the moving contact in engagement with the'fi-xed contact -1. Thus the initial acceleration of the contact 2 by means of the kinetic energy imparted to the piston 26 priorto the engagement of the latter with the movingcontact member ensures a safe contact separation in a manner comparable with what has been shown in the said application for Letters Patent No. 692,459 to which attention is hereby directed.

The piston 26 and moving contact now travel together until as shown by FIG. 2 the'pi'ston 26 engages with an abutment formed by an in-turned flange 34 on the end of the cylinder 25'. It will be understood that on the previously described impact of the piston 26 with the seating 30 all or the major part of the kinetic energy possessed at that time by the piston will be absorbed in accelerating the moving contact 2. If desired the cushion 31 may be arranged to engage with the abutment 34.

In the position shown by FIG. 2 the pressure air admitted tothe housing flows through the annul-argap be tween the fixed contact 1 and the adjacent end of the moving contact 2 and is discharged to atmosphere through the ports 24 and 18 and discharge passage 19 so as to extinguish the are between said contacts. The movingcontact2 remains in the position illu'strated in FIG. 2 until further separating movement of the contact 2 is provided in the following manner. During the operation above described pressure air flows also through the ports 29; the annular clearance between the contact 2 and piston trunk 27, and passages such as 35 in the flange 30, to the free space in the antechamber 36 and housing 43'. It will be observed that whereas in the fully closed position of FIG. 1 the port 12a is unobstructed by the piston 11, in the position shown by FIG. 2 said port has been cove'red by the piston. Consequently the pressure air which is permitted to flow into said time space will build up pressure in said free space and after a predetermined time period determined by the size of passage 35 in relation to said free volume, said pressure will provide on the piston 11 a forcesuflicient to overcome the force of the spring 20. "When these conditions are reached the piston 11 and moving contact 2 will be moved further in the opening direction so as to bring the sealing gasket 22 into engagement with the seating 23. The gasket 22 and area '21 of the piston then closes the discharge port 18 preventing further discharge of pressure air to atmosphere. The moving contact isretained in the position iliustrated in FIG. 3 by the pressure air acting on the area 21 of the piston and the contact will therefore remain open so long as thercont-rol valve is opened to apply pressure air to the housing 3. V

The arrangement shown also operates in accordance with application Serial No. 743,759 aforesaid in the following manner.

When the moving contact reaches the position illustrated by FIG. 2, at which the arc between the main contacts 1 and 2 is extinguished by the air blast, the peripheral surface of the piston portion 11 will have reached a position where the roller 52 is still located for maintaining the auxiliary contact 40 in engagement with the contact 42 but on further movement of the main contact 2 a conical portion 53 of the piston will move under the roller so that the further movement of the main contact 2 after the pause in the condition shown by FIG. 2, will allow the spring 47 to move the contact 40 downwardly out of engagement with the contact 42. By this means the current flowing in the resistor 46 consequent on the opening of the main contact will be interrupted, the auxiliary contacts being fully separated when the main cont-act reaches the fully open position as shown by FIG. 3. The separation of the auxiliary contacts is eifected in a space which as above described is charged with pressure air, namely by way of the ports 45, the increase of air pressure surrounding said contacts facilitating the interruption ot the resistor current.

In order to reclose the circuit breaker the control valve is operated to its position discharging air from the housing 3 to atmosphere. The pressure air within the housing 43 will also be discharged toatmosphere, since this air flows into the chamber 3' by way of the ports 35, the clearance between the piston trunk 27 and the contact 2, and the ports 29. With the reduction of air pressure the force acting on the piston area 21 falls below the pressure of the spring 20 and thereafter the spring will move the contact and piston 11 toward the closed position. So soon as the gasket 22 leaves the seating 23, air within the circuit breaker will also discharge to atmosphere through the ports 24fand 18. The air pressure within the housing 43- will continue to discharge to atmosphere in .the same way as the air within the tubular housing 3 and additionally when the moving contact reaches the closed position as shown by FIG. 1 any air remaining at pressure within said housing 43 will be discharged directly to atmosphere through the port 12a and the port 18 when said'port 12a is uncovered by the piston 11. The circuit breaker'is then in readiness for subsequent re-opening. It will be observed that the port 12a provides that on reclosure of the contacts the circuit breaker is in immediate readiness for re-opening since the uncovering of the port 12a ensures that no residual pressure air will be trapped and maintainedin any of the volumes associated with the housing 43 as well as housing 3.

During the closing movement of the main contact 2 the conical portion 53 of the piston 11 will progressively raise the lever 37 so as to re-close the auxiliary contacts 40, 42 when the main contact returns to the position of FIG. 2. It will be observed that the arrangement ensures that the auxiliary contacts will be closed to re-insert the.

resistor in circuit in direct response to the re-closing movement of the main contact 2. It is thus mechanically impossible for the main contacts to re-close without prior re-closing of the auxiliary contacts.

The connection of the moving contacts 40, with the lever 37"bymeans of the compression spring 49 provides for a predetermined contact force to be obtained in the V closed position. of the main contact, such spring permitting further movement of the lever 37"by' the conical 7 surface 53 after the contact 40 has engaged the fixed contact 42.

In certain circumstances it may be desirable to provide, as is shown by FIG. 4, additional air discharge ports, such as 36, placing the right-hand side of the piston 11 in communication with the interior of the moving contact and said piston. By this means, on movement of the piston 11 from the fully opened position, air at pressure within the housing 43 may discharge directly through such ports 36 and the ports 24, to the port 18 and thereby to atmosphere. rapid discharge of air pressure from the housing 43 to atmosphere on reclosing the circuit breaker, and rapid fall of pressure within said chamber 43 so that after an initial movement of the piston 11 away from the seating 23 the spring 20 is relieved of any opposition in reclosing the contacts, or by residual air pressure .within the housing 43.

The ports 36 are arranged so as to be covered when the piston 26 engages the flange 30. Consequently during opening operation passage of air through said ports will be terminated when the piston 26 engages said flange and the piston 26 and moving contact move together to the position shown by FIG. 2. In the position of FIG. 2 there is therefore no discharge of air through the ports 36' and the air flows through port 35 to build up pressure in the housing 43 in the manner hereinbefore described.

It is to be noted that with constructions according to the invention such as shown in the accompanying drawings, the moving contact may readily be withdrawn from the circuit breaker. For this purpose it is necessary only to remove the end cover 16 when the spring 20 and contact 2 together with the piston portion 11 thereof can be immediately withdrawn from the circuit breaker without the removal or displacement of any of the other parts associated with the moving contact. Conversely, the moving contacts may be replaced without any particular positioning of the lever 37 being necessary, and when said contact is replaced the auxiliary contact 40 and its operating means are automatically in condition for proper operation.

FIG. illustrates a modification of the arrangement of FIG. 1 for a circuit breaker in which resistance switching is not required. In FIG. 5 thecylinder 12 is formed by an inner wall within an outer housing 121:. The annular space between the cylinder and outer housing is in direct communication with the right hand side of the piston 11 so as to provide a free volume appropriate for the desired time delay in build up of pressure necessary to cause the final movement of the moving contact.

It will be understood that in place of the resistance switching means shown in FIGS. 1-4, operating in accordance with application for Letters Patent Serial No. 743,- 759 aforesaid, other arrangements for controlling the connection of a resistance in parallel with the main contacts and for terminating the current in the resistance may be employed.

For example, the resistance may have included in series therewith a pair of fixed electrodes located within a chamber to which pressure air is adapted to be supplied under control of the main moving contact in order to extinguish the arc formed between said electrodes when current flows in the resistance as a result of opening the main contacts. Arrangements of this kind are per se described and claimed in Letters Patent No. 2,794,886 to which attention is hereby directed.

The breakdown of the gap between the fixed electrodes above referred to may be facilitated, in accordance with Letters Patent No. 2,833,896 to which attention is hereby directed, by the provision of means for reducing below the atmosphere value the airpressure in a chamber in 1 which the electrodes are located. As also described insaid complete specification the resistance current may be terminated by application of increased air pressure to The ports 36 thus provide for.

705 ton closing member and no other 8 said chamber similarly to the arrangements described in said Letters Patent No. 2,794,886.

For example, a circuit breaker in'accordance with the invention may ,be arranged in accordance with FIG. 5 but including the resistance 46 of FIG. 1 and the insulating housing 43 of FIG. 1. Said housing is, however, closed at both ends thereof and instead of the movable contact 40 of FIG. '1 a fixed electrode is used and is separated by an appropriate gap from a co-operating electrode the general arrangement of which is similar to that of contact 42 of FIG. 1. The electrode housing may then be connected by'means of a suitable conduit with the housing 12b of FIG. 5, whereby to provide operation in accordance with Letters Patent No. 2,794,886 aforesaid. Preferably, said housing is connected by a conduit with means for producing an extractor or ejector action of air from the electrode housing in accordance with Letters Patent No. 2,833,896 aforesaid.

What we claim is:

l. A gas blast circuit breaker comprising a pressure gas duct, a contact chamber, co-operating stationary and movable contacts enclosed insaid chamber, first and second piston members, said movable contact being mechanically movable by said second piston member, means forming first and second spaces in which said first and second piston members operate, a communicating passage between said first and second spaces, means for admitting the pressure gas from said duct to said first space and also through said passage to said second space, said means forming said second space comprising a pressure chamber having a wall with an outlet to outer atmosphere, a communicating means between said second space and said outlet to the outer atmosphere, said communicating means comprising at least one port in a wall of said pressure chamber, said port being so positioned in relation to said second piston that it is normally open and is closed gradually as the second piston slides over the port along the surface of the wall of the said pressure chamber, the first piston being arranged to bear against the second piston so as to move it and cause by its movement the final closure of the port before the first piston arrives at the end of its effective movement.

2. A circuit breaker as claimed in claim 1, wherein the outside of a portion of the wall of the pressure chamber forms a guiding means for the second piston.

3. A circuit breaker as claimed in claim 1, wherein a closure member is provided for said outlet .to the outer atmosphere, said closure member being connected with said second piston, and means is provided to control the flow of pressure gas to said pressure chamber thereby to determine a time interval starting with the closure ofv the outlet port and suflicient to build up pressure in said chamber to a value for overcoming a force biasing said second piston, thereby also determining a time interval between the motions of said first and second pistons.

4. A circuit breaker as claimed in claim 1, wherein the second piston memberrhas a recess communicating with a hollow in said movable contact and has at least one aperture for directing pressure gas from said contact enclosing chamber to said outlet to atmosphere, the end of said second piston remote from said stationary contact forming a closing member for the said outlet to atmosphere to interrupt the discharge of pressure gas therethrough when said movable contact is fully removed from said stationary contact, and means for biasing said second piston away from said outlet to atmosphere having a force such that the pressure gas admitted through the hollow movable contact into said second space overcomes said biasing force and holds the said contacts open while said outlet to atmosphere is closed by said second pispressure discharge is open. 8'

5. A circuit breaker as claimed in claim 1, wherein said second piston has a should-er arranged to be engaged by a portion of said first piston on its movement for causing an initial opening of said contacts and a displacement 2,902,570 of said second piston relative to said port in said com- 2,919,329 munication means to provide said closure of said port.

References Cited in the file of this patent 5 59 799 UNITED STATES PATENTS 2,500,429 Nijland Mar. 14, 1950 541,941 2,645,697 Beatty July 14, 1953 933,819

10 Roxburgh et al Sept. 1, 1959 Latour Dec. 29, 1959 FOREIGN PATENTS France Feb. 17, 1954 (First addition to No. 990,536) Great Britain Dec. 18, 1941 Germany Oct. 6, 1955

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