US2911546A

US2911546A - Electric circuit breaker

Info

Publication number: US2911546A
Application number: US697878A
Authority: US
Inventors: John A Oppel
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1957-11-21
Filing date: 1957-11-21
Publication date: 1959-11-03
Anticipated expiration: 1976-11-03

Description

Nov. 3, 1959 Filed NOV. 2l, 1957 Ffgj.

J. OPPEL ELECTRIC CIRCUIT BREAKER 2 Sheets-Sheet 1 H`S Atborneg.

Nov. 3, 1959 J. A. oPPEL 2,911,546

ELECTRIC CIRCUIT BREAKER Filed Nov. 21. 1957 2 Sheets-Sheet 2 Inventor: John A. Oppel,

r2,911,546 ELECTRIC crRcUrrBREAKER John A. 'OppeL Aldan, Pa., assi'gnor to General Electric Company, a corporation ofA New York Application November 21, .1957, .Serial No. 697,878V

6 Claims. l(c1. 307-136) ment for interrupting the current flowing through said impedance means after said main contacts have been opened. p f

For controlling the voltage developed across the main contacts of a circuit breaker during a circuit-interrupting operation, it has been customary to shunt these contacts with an impedance through which current is transferred when the main contacts are opened to interrupt the circuit. For interrupting the current through the impedance, there is customarily provided a switch which opens afterftlie main contacts have been opened.

v`In order for the impedanceconsistently to carry out its intended function during the interrupting process, it is important that its switch always be opened at a precisely-controlled predetermined time interval after the main contacts part.

Most prior arrangements for operating such a switch have `not been capable of controlling this time interval with the desired degree of precision and consistency. For example, the usual Huid-controlled operating arrangements have been subject to inconsistencies as a result of variations in the-pressure and temperature ofthe operating fluid; Direct mechanical couplings between the impedance vswitch and thefmain contacts have sometimes been used, but prior couplings of this nature-have been subject to certain disadvantages. For example, they generally do not lend themselves to providing a long enough time delay and, in many cases, do not readily United States Patent 0 lend themselves to closing the Yswitch and main contacts in the desireditimed sequence during closing of the circuit breaker. in this regard, it is desirable that closing of the impedance switch be delayed until relatively late in the closing stroke-for the main contacts, thus providing forreduced heating of the impedance as a result of current flowing therethrough prio-r to-.closure of the main contacts. Y

Accordingly, it is an object of my invention to provide, in a circuit breaker of this general type, improved operating means for consistently opening an impedance switch at a precisely-controlled predetermined time interval after the main contacts part.

Another object is to construct the switch-operating means in such a manner that it is capable of providing an accurate time delay of a relatively great duration and is also capable, during a closing operation,y of delaying closing of the impedance switch until relatively late in the closing stroke ofthe main contacts. y

In carrying out my invention in one form, i provide a circuit `breaker which has its main contacts shunted by an impedance. Connected in series with the impedance and in shunt with the main contacts, separable auxiliary contacts are provided. A connnon actuating member is provided for a movable one of the main contacts and a movable one of the auxiliary contacts;

Means connecting the actuating lmember'and the movable main contact causes the main contacts to part in'response to opening movement of the actuating member. A coordinating member connected between the actuating member and an auxiliary contact-operating spring is arranged to effect charging of the spring in response to initial opening movementof the actuating member. A latch is provided to block discharge of the spring during such initial opening movement, but, at a selected point thereafter, means controlled by the coordinating member acts tov release the latch, thus allowing the spring to discharge. A lost-motion connection provided between the spring and the movable auxiliary 4contact allows initial discharge of the spring to takeplace Without affecting the then-closed position of the movable auxiliary contact, but, at a selected point thereafter, this connection transmits forces from the spring to the movable auxiliary contact, and such forces open the auxiliary contacts. Due to the intentional time delay in tripping the latch and the intentional time delay resulting from the lost-motion connection,` the auxiliary contacts part substantially after the main contacts have parted.

Fork a better understanding of my invention, reference may be had to the following speciiication taken in connection with the accompanying drawings, wherein:

Fig. 1 is a side elevational view, partially in section, f

showing a circuit breaker embodying my invention. The

' circuit `breaker is depicted in the closed position. v

- ing the parts of Fig. 2 at an instant during a circuit breaker-opening operation.

Fig. 4 is a view partiallyy in section taken along the line 4-'4 of Fig. l.

Referring now to Fig. 1, *the circuit breaker shown therein is of the general type disclosed and claimed in Patent No. 2,783,338-1Beatty, assigned to the assignee of the present invention. This circuit breaker comprises an enclosed interrupting chamber 11 dened, in part, by a metallic casing 12 which is filled with pressurized arcextinguishing gas. t

A pair of elongated conductive studs 15 and 2t). project into the casing 12 from diametiically-opposed points, and each of these studs carries a suitable stationary contact assembly 16 at its radially inner end. Cooperating with each stationary contact assembly is a movable contact 2S pivotally mounted upon a stationary pivot 29. These pivots 29 are supported upon stationary brackets 31 which are integral with one end of a stationary operating cylinderV 32. Suitable means (not shown) are provided for transferring current between the movable contacts 23 and the brackets 31, so that the brackets 31 together with the cylinder 32 form a conductive path electrically interconnecting the two movable contacts 28.

The cylinder 32, at its left hand end, is suitably supported from Va generally cylindrical housing 33,"which, in turn, is suitably secured at its left hand end to the metallic casing 12.l The mechanical connection between the housing 33 and the casing 12 is best shown in Fig. 4, where the housing 33 is shown provided with a ilange 34 that is suitably joined to a flange 35 secured to the casing 12.

For producing a gas-blast action for extinguishing the arcs which are established by separation of the contacts 16 and 23, the housing 33 is provided ywith a normallyclosed annular exhaust passage 36 which leads from Vthe interrupting chamber 11 to the surrounding atmosphere. This will be more readily housing 33 at its right hand end is formed with a `pair of generally diametrically-opposed.nozzle-type electrodes 3S defining inlets to the exhaust passage 36. For controllingv apparent from Fig.` 4. The

the flow of arc-extinguishing gas through the nozzle electrodes 38 and through the exhaust passage 36, there is provided at the outer end of the exhaust passage 36 a cylindrically-shaped reciprocable blast valve member 40 which slides smoothly in a surrounding tubular valve housing 41 integrally formed in the housing 33. ln Fig, 4, the valve member 40 is shown in its closed position wherein an annular liange 42 formed at its left hand end sealingly abuts against the stationary liange 34, which serves as a valve seat. The valve member 40 is normally mainA tained in this closed position of Fig. 4 by the action or a suitable spring (not shown) and by the action of the pressurized gas within the passageway 36. This gas produces upon the flange 42 an unbalanced force urging the valve member 40 to the left into its closed position.

Since the chamber 11 is normally filled with pressurized gas, it will be apparent that when the valve member is opened by movement to the right (by means not shown), gas in the chamber 11 will flow at high speed through the nozzles 38 land out 4the passage 36 past valve member 4t) to atmosphere, as is indicated by the `arrows e and f shown in Fig. 4. This rapid flow of gas through the nozzles 3S creates an axial arc-enveloping blast which acts rapidly'to extinguish the `arcs which are drawn ad.- jacent the nozzles by movement of the movable contacts 28 away from Itheir stationary contact assemblies 16.

For operating the blast valve 40 and the movable contacts 28, a combined operating mechanism preferably of the kiluid-actuated type shown in the aforementioned Beatty patent is provided within the

cylinders

32 and 33. The details of this operating mechanism form no part of the present invention and, hence, such details are not shown in the present application. standing of the present invention may be had if it is understood that the operating mechanism acts during an opening operation to drive a piston rod shown Vat 58 to the right and also acts to open the blastivalve 40. The piston rod 58 is coupled to the contacts 28 (by means soon to be described) and, hence, such movement ot the pistonJod serves to drive the contacts open. At a predetermined instant after the contacts 28 have been opened, the then-open blast valve 40 is driven closed by the operating mechanism, as is described in detail in the Beatty patent. This prevents further loss of gas from the interrupting chamber 11.

The means for coupling the piston rod 5S to the main contacts comprises a crosshead 59 and two sets of connecting links 60. The crosshead 59 is rigidly secured to the piston rod 58 by suitable clamping means, whereas the connecting links 6l) are pivotally connected -at 61 and 62 to the crosshead and movable contacts, respectively.

ln the position of Fig. l, the movable contacts 28 are biased into closed position by means of overeenter compression springs 64. Each of these springs 64 has one end pivotally supported at 65 on a projecting portion of one of the brackets 31. At ltheir inner ends, the springs 64 are pivotally supported on the crosshead 59. These overeenter springs 64 tend to urge the contacts closed while the crosshead 59 is to the left of a reference line connecting the pivots 65. But when the crosshead is moved to the right beyond this reference line (as occurs during a contact-opening operation), the overcenter springs thereupon tend to urge the contacts in a contactopening direction. This action coupled with that of the operating mechanism acts to hold the contacts 28 in a fully-open position until the operating mechanism is subsequently operated to close the contacts 28.

Shunting the upper pair of

main contacts

16, 28 is an impedance element 7 0, preferably in the form of a resistor Wound about an insulating core 70a carried by a conductive tube 71. The conductive tube 71 is supported from the conductive stud by means of conductive webs 72 electrically interconnecting the tube 71 and the stationary contact assembly 16. The lower terminal of the resistor 70 is connected to the tube 71, whereas the upper termi- An adequate underl 4 nal is locally insulated from the tube 71 and is connected by means of a conductor 74 to an electrode 73 of an impedance or resistor switch 75.

The resistor switch 75 comprises, in addition to -the electrode 73, a second electrode 76 spaced from electrode 73 and coacting with electrode 73 to form an interrupting gap between the two electrodes. The electrode 73 is supported on the central housing 33 by an insulator 77 which is capable of electrically isolating the electrode 73 from the housing 33 When the resistor switch is open. The electrode 73 is also supported on the housing 33 but is electrically connected to the housing. Electrically bridging the two

stationary electrodes

73 and 76 is a movable electrode 78, which in its closed position of Fig. l, butts against the two stationary electrodes. Thus, it will be seen that the resistor 70 is connected in shunt with the

upper contacts

16, 28 by means of -a circuit which extends through the

parts

72, 71, 70, 74, 73,78, 76 and 33. As will be apparent from Fig. 1, the lower

main contacts

16, 28 are shunted by a similar circuit. Since the parts forming this lower shunting circuit are substantially identical to those forming the upper circuit, corresponding lower parts have been assigned corresponding reference numerals followed by the suiix a.

The electrodes of the resistor switch may be thought of as being auxiliary contacts for the overall circuit breaker and are frequently referred to in the present application as auxiliary contacts.

Referring more particularly to the resistor switch 75, it will be noted from Fig. l that each of the

movable electrodes

78 and 78a has an elongated pin 80 integral therewith and projecting therefrom to the right. Each of these pins is `freely received in Ian opening formed in a reciprocable cross-beam 81 of insulating material. A pa-ir of compression springs 82. and 82a, each of which is disposed between the cross-beam 81 and one of the

movable electrodes

78 or 78a, urges the movable electrodes into firm circuit-closing engagement with the stationary electrodes. While the switch 75 is in its normal closed position of Fig. l, the cross-beam 81 is restrained from moving to the right, as will soon appear more clearly. When, however, the cross-beam 811 is driven to the right during a switch-opening operation, it eventually impacts against suitable abutments 83 adjustably secured to the outer ends of the pins and, thus, drives the movable electrode 78 and'78a to the right into an open position spaced from the stationary electrodes. To aid in guiding the cross beam 81 during such opening movement, a suitable guide pin 84v is shown secured to a stationary portion of the switch 75 and projecting through a guide opening formed in the crossbeam.

Opening of the resistor switch 75 is yprecisely coordinated with opening of the

main contacts

16, 28 by means including a switch-operating rod, lor coordinating member, 85 which is suitably secured to the crosshead 59, as shown in Figs. l. This securing means of Fig. l comprises ia pair of nuts 86 threaded on the operating rod 85 and clamping a bracket 87 therebetween. The bracket 87 is bolted or otherwise secured to the crosshead 59.

As will be Yapparent from Figs. l and 2, the operating rod 85 extends from the crosshead 59, through an opening 89 in the cross-beam 81, into a cylinder 93 mounted on the casing 33 of the breaker. The opening 89 in the cross-beam 81 is large enough to permit the operating rod 85 to move freely relative to the crossbeam.

Ars shown in Fig. 2, the operating rod carries at its left hand end an abutment 91 which is preferably threaded thereon and is prevented from accidentally moving ont of its position of adjustment by means of a suitable jam nut 92. Further to the right, a second abutment 93 is secured to -the rod 85, `and between this second abutment 93 and the cross-beam 81, a compression spring 94 is disposed. This compression spring 94 and the abutment 93 are disposed within a tubular housing 95 that is secured to the crossbeam 81 and is slidably through the arcing regions.

-

tacts

16, 28 part.

mounted within-'the cylinder V90 hy means of suitable slide bearing 95a. The compressionv spring 94 urges the cross-beam 81 to the rightitoward its Vopen position, but

. the cross-beam-81 is restrained in its position'of Fig. 2 by the abutment V93. In thisregard, as shown in Fig. 2,

such as the torsion spring 100, urges the latch 96 coun terclockwise about its pivot 97 vinto the position of Fig. 2', Where its head 98-'is seated within the slot `99.

When theoperating rod 85 is driven tothe right during a circuit-breaker opening operation, it drives the'abutment 93 to'the right thereby compressing the spring 94. During such movement of the operating rod 85 from its position of Fig. 2 to that of Fig. 3, the latch 96 blocks movement of the tubular housing 95 `and the connected cross-beam 81, thus preventing the spring 94 from discharging at its right hand end during this interval. As theoperating rod continues its rightward opening move ment through the position of Fig. 3, the abutment 91 on the operating rod engages a camsurface 101 formed on,the latch 96. This forces thelatch 96 downward, thereby releasing vit from latching relationship with the tubular housing 95. A y 1 'When the latch 96 so released, the charged spring 9,4 `discharges thereby forcing the cross-beam 81 to the right.` The springs 82 and 82a alsodischarge inresponse to latch release and thus aid in driving the cross-beam 81fgtothe right. The

movable contacts

78, 78a remain closed 'until the cross-beamrnoves suiciently to they right to engage the abutments 83, shown in Fig. 1. This impact coupled with continued'L motion ofthe cross-beam 81- to the right, simultaneouslyl drives the electrodes 78, 78ay to the right into an open-circuit position spaced from the stationary electrodes. v,Preferably,this opening travel ofthe electrodes 78 and 7 8a is approximately equal to the distance moved by the crosshead 59 after the main contact first part.- Thus, at the endof the opening stroke', the Ashoulder 112 on tube 95 bears against abutment 93.A

The arcs which are established by opening movement s "of the

movable electrodes

78, 78a are quickly extinguished by blasts of uid which flow at high speed To this end, the electrodes 76-3 and 76a are each formed of a` hollow construction with centrallyv disposed blast passages 105 leading into the `annular blast passage 36. When the blast valve 40 is opened, pressurized fluid Hows at high' speed through these blast passages, and the resulting blasts are capable of, quickly extinguishing the arcs opening movement of electrodes 7S,

It is to be noted that the arc-extinguishing blasts through all of the circuit-interrupting arcs of the breaker are controlled by the single blast valve 40 located downstream from the arcs. When the opening operation is completed and the blast valve40 has closed, the pressurized -gas in the interrupting `chamber 11 maintains a high dielectricstrengthinsulating gap between each pair of spaced contacts, or electrodes, thus maintaining the circuit open.

vThe above-described operating mechanism for' the resistor'switch 75 is capable of consistently parting the electrodes of the switch'at a precisely-controlled predetermined instant that is spaced by an interval ofrelatively. great duration fromk the With regard to the extensive duration. of this time-delay, it is to `be noted thatkth'e operating rod 85 effects release of the latch 101 after the main contactsy open 16, 28 part and, preferably, near the end which are formed by.

instant at which themain con of their opening stroke. Moreover, even then, the discharging spring 94 does not immediately open the

electrodes

78, 78a but -must .first drivethe cross-beam 81 through its relatively extensive lost-motion travel into engagement with the abutments 83 before the

switch electrodes

78, 78a begin to part. With regard to precisely controlling this time-delay with a high degree of consistency, it is to be noted that operation of the switch is not signiiicantly affected` by temperature or pressure variations inthe interrupting medium, inasmuch as this medium is not being relied upon as an actuating uid, as in many prior constructions. Nordoes vthe switch rely upon dashpots or similar timers, which are subject to varying characteristics as a result of temperature changes..

In the `disclosed switch, the point of latchrelease is coni notedthat the electrodes of the resistor'switch are of the butt-type substantially devoid of sliding engagement between the electrodes, thus avoiding significant variations in the frictional retarding forces imposed by the contacts during opening movement. Incontrast, with sliding con# tacts, those irregularities in the contact surface resulting' from arcing can introduce some relatively unpredictable retarding forcesA which could significantly aiect the desired time delay.' With butt contacts of the type present in the disclosed -switch,fsueh sliding friction is largely absent and therefore can introduce no objectionable variations in the duration vofthisA time delay. I

With regard to controlling the time-delay which occurs afterV the latch 96A isreleased, the effective mass' of the cross-beam 81 is purposely made very large in comparison to that of the

contact structure

78, 80, 83 and 78a, 80, 83... To this end, arelatively massive block 81a is suitably joined to the cross-beam 81 so asto retard initial discharge of the springs 82 and 94 to a predetermined desired extent. Since the combined massof the crossbeam together with its yattac-hed block is much greater than that ofy the contact structure,.once the springs 82, 94.have driven these parts 81. and 81a through their lost-motion travel, considerable .momentum has been attained and the relatively lightfcontac'ts 78, 78a can 'then be picked up without an objectionable reduction in opening speed. This allows the contacts 78 and^78a to open at the desired highspeed in spite ofv the initial retardation of spring discharge.

Anothery feature of myswitchis that it is an inexpensive and-compact device having its major components housed within a slender cylinder which is. readily attachable to a stationary part of the switch. In this latter regard, notein Fig. l that suitable fastening devices in the form of conventional screws 110 are utilized to secure the switch 75 to the side ofl the circuit breaker casing 33.

Closing of the circuit breaker is effected by returning the crosshead 59 from its'open positionleftward to its closed position shown in Fig; l. At the beginning of this closing stroke,'the'left end`112 of the tubular casing is bearing against the abutment 93 and, accordingly, initial leftward movement of the crosshead 59 and the connected operated rod forcesV the tubular casing 95 together 'with the lcro'ssbeam, 81 to the left, thus driving the

electrodes

78, 78a` toward closed position. Simultaneously with such action, leftward movement of the crossfhead 59 is also driving the movable main contacts 28 closed. Since the distance between fully-open posi- A tacts first touches `its stationary contact at roughly the `same instant for each set of contacts.

While 1I have shown and described a particular embodiment of my invention, it Will be obvious to those skilled in the art that various changes and modications may be made without departing from my invention in its broader aspects and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

`l. In an electric circuit breaker, separable main conttacts, impedance means .shunting said main contacts, fseparable auxiliary contacts connected in series with said impedance means and in shunt with said main contacts, a "common actuating member for a movable one of said main contacts and for a movable `one of said auxiliary contacts, means for connecting said actuating member to said one main contact for parting said main contacts in response to opening movement of said actuating member, a reciprocable rod connected to said actuating member, a spring operatively connected between said movable auxiliary contact and said rod and arranged to be charged by movementV of said rod during opening movement of said actuating member, latch means blocking discharge of said spring `during initial opening movement of said rod, means controlled by said rod for releasing said latch means after a predetermined opening movement of said actuating member tot allow said spring to discharge, and means responsive to discharge of said` spring for driving said one auxiliary contact out of engagementwith the other said auxiliary contacts at an instant appreciably after said main contacts have parted.

2. In an electric circuit breaker, separable main contacts, impedance means shunting said main contacts, separable auxiliary contacts connected' in series with said impedance means and in shunt with said main contacts, a common actuating member for a movable one of said main contacts and for a movable one of said auxiliary contacts, means for connecting said actuating member to said one main contact for parting said main contacts in response to opening movement of said actuating member, a coordinating member connected to said actuating member, a spring operatively connected between said movable auxiliary contact and said coordinating member and arranged to` be charged'by movement of said coordinating member during opening movement of said actuating member, latch means blocking discharge of said spring during initial opening movement of said actuating member, means controlled by said coordinating member for releasing said latch means after a predetermined opening movement of said actuating member to allow said spring to discharge, a driven member coupled to said spring and arranged to be actuated by said discharge of said spring, coupling means forming a lostmotion connection between said driven member and said one auxiliary contact for permitting said spring, in discharging, to drive said driven member through a predetermined tra'vel before establishing a positiveconnection between said auxiliary contact and said driven member, said vcoupling means thereafter transmitting contact-separating forces to said auxiliary Contact and parting said auxiliary contacts appreciably after said main contacts have been parted. the effective mass of the structure driven by said spring prior v'to establishment of said positive connection being substantially greater than lthe effective mass of the added structure driven by said spring after establishment of said positive connection.

3. In an electric circuit breaker, separable main contacts, impedance means shunting said main contacts,

v separable auxiliary contacts of the non-sliding butt-type connected in series with said impedance means and in shunt with said main contacts, a common actuating member for a movable one of said main contacts and for a movable one of said auxiliary contacts, means for connecting said actuating member to said 'one main con'- tact for parting 'said main contacts in response to opening movement of said actuating member, a coordinating member connected't'o saidactuating member, a spring operatively connected between said, movable auxiliary coupling means forming a lost-motion connection between said driven member and said one auxiliary contact for permitting said spring, in discharging, to drive said driven member through -a predetermined travel before establishing a positive connection between said auxiliary contact and said driven member, said coupling means thereafter transmitting contact-separating forces to said one contact and parting said auxiliary contacts appreciably after said main contacts have been parted. r

4. The circuit breaker of claim 3 in combination with additional spring means connected between said driven member and said movable auxiliary contact for 'maintaining said movable auxiliary contact closed during movement of said driven member through said predetermined travel. f p l 5. In an electric circuit breaker of the fluid-blast type, separable main contacts, impedance means shunting said main contacts, separable auxiliary contacts connected in series with said impedance means and in shunt with-saidmain contacts, blast valve means located downstream from said contacts and openable tov produce anearcextinguishing blast of fluid through the regionV of said contacts when said ,contacts are being opened duringa circuit-interrupting operation, a common actuating member for a movable one of said main contacts and for 'ai movable one of said auxiliary contacts, means connecting said actuating member to said one main contact for parting said main contacts in response to opening movement of said actuating member, a reciprocable rod connected to said actuating member, a spring operatively connected between said movable auxiliary contact and said rod varid arranged tobe charged by movement of said rod during opening movement of said actuating member, latch means for blocking discharge of said spring, during intial opening movement of said actuating member, means controlled by said rod for releasing said latch means after a predetermined opening movement of' said actuating member to allow said spring to discharge, and means responsive to dischargevof said spring for driving said one auxiliary contact out of engagement with the other said auxiliary contacts at an instant appreciably after said mainv contacts have parted.

6. In an electric circuit breaker, separable main contacts, impedance means ,shunting said main contacts, separable auxiliary contacts connected in series with said impedance means and in shunt with said main contacts, a common actuating member for a movable. oneof said main contacts and for a movable one of said auxiliary contacts, means for connecting ysaid actuatingmember ot said one main contact for parting said main contacts in response to opening movement of said actuating niember, a reciprocable rod connected' to said actuating member, a cylindrical member in which said rod is movable,

a tubular casing surrounding said rod `and disposed with-4 insaid cylindrical-member, abutment means secured to said rod and disposed Within tubular casing, adriven' member secured to said tubular casing and coupledto said contacts, a spring disposed withinsaid tubular cas` ing and operatively connected between said abutment means and said driven member, latch means for blocking discharge of said spring during initial opening movement of said actuating member, means controlled by said rod for releasing said latch means after a predetermined opening movement of said actuating member, and means responsive to discharge of said spring for driving said one auxiliary contact out of engagement with the other of said auxiliary contacts at an instant appreciably after said main contacts have parted.

References Cited in the file of this patent UNITED STATES PATENTS Flurscheim Jan. 23, 1945 Thommen Nov. 9, 1948 Roxburgh et al. June 4, 1957