US3529108A

US3529108A - Nozzle and contact construction for fluid-blast circuit interrupters

Info

Publication number: US3529108A
Application number: US576711A
Authority: US
Inventors: Robert M Roidt
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1966-09-01
Filing date: 1966-09-01
Publication date: 1970-09-15
Anticipated expiration: 1987-09-15
Also published as: BE703409A; SE330567B; GB1158559A

Description

Sept. 15, 1970 R. M. ROIDT I 3,529,108

NOZZLE AND CONTACT CONSTRUCTION FOR FLUID-BLAST CIRCUIT INTERRUPTERS Filed Sept. 1, 1966 2 Sheets-Sheet l PRIORART PRIOR ART I I3 2 & DISPLACEMENT FIG. 8.

INVENTOR Robert M. Roidf ATTORNEY U.S. Cl. 200148 9 Claims ABSTRACT OF THE DISCLOSURE A fluid-blast type of circuit interrupter is provided having separable stationary and movable contact structures. The movable contact structure comprises an outer main movable contact tube insulatingly encompassing an inner movable arcing contact. The stationary contact structure includes outer main stationary contact fingers and an inner conducting orifice, through which the fluid blast exhausts.

The operation is such that the main current arc, drawn between the main contact fingers and the outer movable conducting tube, is transferred, by the radial inward fluid blast through the stationary conducting nozzle, to the inner movable arcing contact, thereby inserting into series circuit impedance means. The impedance means may assume the form of a resistance, or accelerating coils, to assist piston motion in creating the desired fluid blast. The fluid-flow path through the conducting stationary nozzle is smoothly configured to avoid stagnant regions, and to rapidly open up the nozzle flow area.

A modification of the invention provides a biased inner conducting nozzle having a lost-motion connection with the outer main contact fingers.

This invention relates generally to fluid-blast circuit interrupters and, more particularly, to fluid-blast circuit interrupters in which an impedance means, assuming the form of a resistance means, or an a'celerating coil, is electrically connected between the arcing and main movable contacts during the opening operation.

A general object of the present invention is to provide an improved fluid-blast circuit interrupter in which are transfer of the main-current arc to the arcing contact is effected in a minimum of time.

Another object of the invention is to provide an improved fiuid-blast circuit interrupter in which the gas flow is directed in a highly-efiicient manner to prevent retransfer of the transferred arc.

Still a further object of the pesent invention is to provide an improved fluid-blast circuit interrupter of the type utilizing electromagnetic means for inducing a fluid flow, in which the arc is transferred from the main contact structure to arcing contact structure to insert thereby accelerating coils into the series electrical circuit.

In US. patent application filed Sept. 1, 1966, Ser. No. 576,616 by Russell E. Frink, and assigned to the assignee of the instant application, there is illustrated and described a fluid-blast circuit interrupter in which fluid flow is achieved by piston actuation utilizing electromagnetic means for assisting in piston motion. Certain features of the aforesaid electromagnetic means are incorporated in a subsequent-filed patent application by the same inventor Ser. No. 576,739, which utilizes an arc-transfer means United States Patent for inserting the accelerating coils into the series circuit for assisting in piston motion. It is a further object of the present invention to improve upon the arc-transfer means of the aforesaid Frink patent application rendering the same of the improved construction.

A commercial form of circuit interrupting structure embodying the ideas of the aforesaid two Frink applications is set forth and described in US. patent application filed Sept. 1, 1966, Ser. No. 576,740, by Russell E. Frink and William H. Fischer, and likewise assigned to the assignee of the instant application. It is a further object of the present invention to improve upon the generally commercial form embodying the concepts set forth in the first-mentioned two patent applications.

Still a further object of the present invention is the provision of an improved fluid-blast circuit interrupter of the type utilizing a nozzle, or orifice construction associated with the stationary contact structure, in which the fluid-flow path is improved in combination with the movable contact structure incorporating main and arcing contacts, so that arc transfer is readily achieved with a minimum of likelihood of the arc retransferring back to the main contact structure.

Still a further object of the present invention is the provision of an improved fluid-blast circuit interrupter of the type set forth in the immediately preceding paragraph, in which the fluid-flow path is improved by a lostmotion mechanical connection between the conducting nozzle electrode, or contact of the stationary contact structure and the co-operable surrounding main contact fingers.

In accordance with one embodiment of the present invention, there is provided a movable contact structure incorporating an outer main movable contact and an inner arcing contact insulated from the outer main contact movable together as a unit. An impedance means, either assuming the form of a resistance, or assuming the form of one or more accelerating coils, is electrically connected between the outer and inner movable contacts. Cooperable with the aforesaid two movable contacts is a relatively stationary contact structure incorporating outer main contact fingers and an inner member so configured as to provide an orifice, through which fluid, such as gas, under high pressure may flow. The insulation between the outer and inner movable contacts is so configured, and the nozzle member is likewise so configured as to rapidly effect are transfer from the outer main contacts to the inner contacts to effect the lengthening thereof, and to prevent a retransfer of the are back to the main separable contacts.

In accordance with a modification of the contact structure, as described in the immediately preceding paragraph, there is provided a lost motion mechanical connection between the relatively stationary nozzle member and its associated encompassing outer main stationary contact, which may assume the form of a plurality of stationary circumferentially-disposed contact fingers, so as to effectively direct the gas flow.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

FIG. 1 illustrates a prior-art contact construction resulting in poor arc-transfer conditions, the contact structure being illustrated in the closed-circuit position;

FIG. 2 is a fragmentary view similar to that of FIG. 1,

illustrating the prior-art contact construction of FIG. 1,

but illustrating the contacts in a separated condition in which are establishment occurs;

FIG. 3 is a graph illustrating the relatively poor conditions of fluid flow, which occur in a contact structure of the type set forth in FIGS. 1 and 2, as compared with a later improved contact construction;

FIG. 4 is a vertical cross-sectional view through a commercial form of piston-operated device, incorporating the principles of the present invention, the contact structure being illustrated in the closed-circuit position;

FIGS. 57 illustrate, fragmentarily, different separated contact positions of the contact structure illustrated in FIG. 4, showing different steps during the circuit-opening operation;

FIG. 8 illustrates a modified form of contact and nozzle configuration in which lost-motion is incorporated into the nozzle member to improve the fluid-flow conditions;

FIG. 9 illustrates, fragmentarily, the contact and nozzle construction according to FIG. 8, but illustrating the contacts in the partially open-circuit position; and

FIG. 10 illustrates the accelerating coil connections of the commercial form of the invention illustrated in FIGS. 4-7 of the drawings.

Operation of magnetic puffer-type circuit interrupters in accordance with the fluid-blast circuit interrupter set forth in US. patent application filed Sept. 1, 1966, Ser. No. 576,616 requires: (a) rapid transfer of an arc from the closed-circuit contacts to the arcing current electrodes and, once this transfer has been effected, (b) rapid opening of the area occupied by the arc to the flow of quenching gas. Condition (a) is necessary, since slow arc transfer permits electrode erosion by the arc during the opening operation, and thus may result in an open circuit after contact reclosure following an interruption operation. Condition (b) is required to interrupt the arc as rapidly as possible before its establishment as a steady arc.

FIGS. 1 and 2 illustrate prior-art forms of contact and nozzle constructions, having objectionable features, which it is the purpose of the present invention to overcome. With reference to FIG. 1, it will be noted that the stationary contact structure 1 includes a plurality of outer contact fingers 2 and an inner annular arcing contact surface 3. Cooperable with the stationary contact structure 1 is a movable contact structure 5 including an outer main contact tube 7 spaced by insulation '8 from an inner projecting movable arcing contact. From a study of the aforesaid patent applications, it will be noted that impedance means is electrically connected between the outer and inner movable contacts 7, 10 to cause the insertion of, for example, accelerating coils into the circuit to assist in the fluid-driving motion of associated piston members, more fully described hereinafter. For the purpose of moment, in relation to FIGS. 1 and 2 exemplifying prior-art contact and nozzle constructions, it will be noted that a main-current arc is established between the

main contacts

2, 5, and is transferred by the gas flow, as illustrated by the arrows 13, to the inner arcing contacts 3, 10, thereby causingthe insertion into the series electrical circuit of associated accelerating coils.

It will be noted, with reference to FIGS. 1 and 2, that during interruption the electrodes 1, 5 are separated, and arc transfer is effected by the proximity of the arcing contacts 3, 10, i.e., a geometrical arc-transfer procedure.

Although rapid arc transfer is effected by such a contact structure, as illustrated in FIGS. 1 and 2, the hot turbulent quenching gas in the complicated flow path, especially

stagnant regions

4 and 6, frequently allowed arcing restrikes from electrodes or contacts 3, 7 and

contacts

2, 10 and between contacts 2, 7. Also, condition (b) discussed above, was only partially fulfilled, as a graph of minimum flow path area vs. separation distance shows, as illustrated by the line in FIG. 3 of the drawings.

With reference to FIG. 3 of the drawings, it will be noted that the plateau (region A) shown on the graph 'is'a result of the long arcing electrode 10' remaining near electrode 3 to insure arc transfer. However, if the first current zero occurs during this stage of interruption, the mass-flow rate of quenching fluid through this small area may not be great enough to cool, and quench the arc and, at the next current zero, the arc may be too well established to quench. The contact and nozzle construction with which the present invention is concerned, and which drastically improves the contact mechanism just discussed, is based upon the concept that the flow of qu nching medium, such as high-pressure sulfur-hexafiuoride (SP gas, may be solely ralied upon to insure arc transfer, and thereby enhance the minimum nozzle area vs. displacement curve. As illustrated in FIGS. 4-7 the improved contact and orifice constructions of the present invention provide improved gas-flow paths, and a prevention of retransferring of the transferred arc.

In more detail, with reference to FIG. 4 of the drawings, it will be noted that there is provided an interrupting unit 17 of the fluid-flow type. This interrupting unit 17 comprises, generally, a piston-actuated fluid-flow arrangement comprising an outer stationary operating cylinder 18, within which moves a piston assembly 19 incorporating a first movable element 20 connected to a second movable element 21 by a plurality of concentricallylocated conducting tubes and a pair of conducting guide tubes (not shown).

As shown in FIG. 4, the movable piston assembly 19 carries a movable contact structure, generally designated by the reference numeral 26, and comprising an outer main contact tube 23 insulated by cylindrical spacers 28, 29 from an inner hollow venting arcing contact tube 24, which projects further toward the stationary contact structure 31 than the outer main movable contact tube 23. In addition, the piston assembly 19 includes an accelerating coil 33 and a movable tubular insulating orifice member 34. A pair of insulating operating links 35 are connected to bifurcated movable connections 36, which are bolted, as at 37, to the movable piston assembly 19.

The relatively stationary contact structure 31 includes an inner stationary nozzle, or conducting orifice member 39, which is enveloped by an outer set of main contact fingers 41. The relatively stationary contact structure 31 is supported, adjustably, by a threaded connection 43 to a stationary main support casting 44, which is bolted to the outer stationary insulating operating cylinder 18.

The outer conducting main contact tube 23 and the inner arcing tube 24 move together as a unit, and are connected to the movable element 21 of the movable piston assembly 19, as by means of an auxiliary contact casting 46, which is threaded to the right-hand end of the outer main contact tube 23. As shown, the auxiliary contact casting 46 has movable contact portions 47, which electrically engage with the two pairs of contact fingers, which are supported by a stationary casting 50', which is connected to one line terminal L2 of the device.

An accelerating repulsion coil 51 is embedded in an insulating head 52, which is secured to the right-hand extremity of the conducting

tubes

23, 24, and FIG. 11 generally shows the circuit connections.

During the opening operation of the device of FIG. 4, the insulating links 35, being connected to the operating mechanism (not shown), are moved toward the right to compress the gas, such as sulfur-hexafluoride (SP gas, within the region 54, and force the same past the openings in a spider support 55 and through the orifice opening 56 provided by the contact nozzle member 39. The establishment of a main-current arc, as shown in FIG. 5 is carried by the gas flow, as illustrated by the arrows 59, to the

inner arcing contacts

24, 39, the movable arcing contact 24, as mentioned, being insulated from the outer conducting main movable contact tube 23.

FIG. 6 illustrates the location and contact separation distance, which takes place upon arc transfer 61 to the stationary and

movable arcing contacts

24, 39, thereby establishing an electrical circuit through the three accelerating

coils

33, 51 and 53. As mentioned previously, two of the

coils

33, 51 are connected with the movable piston assembly 19 at opposite ends thereof, and a third accelerating coil 53 is embedded within an insulating plastic 62, which is cemented within the right-hand end of the stationary operating cylinder 18.

Generally, the functioning of the accelerating coils is such as to effect an attraction, or attracting force between the two accelerating

coils

33, 53, and a repulsion, or opposing force between the two accelerating

coils

51, 53 to assist the mechanical effort exerted by the operating mechanism (not shown), to effect fluid-driving motion of the piston member 20 within the operating cylinder 18.

It will be noted, comparing the contact and orifice construction of FIG. 4 with that of FIGS. 1 and 2, as with the previous device, there is a closed-circuit contact dwell time at the initiation of the interruption operation to permit a quenching medium pressure build-up prior to contact separation. However, upon electrode separation, the device of FIG. 4 directs the high-velocity flow at the short arc 58 (FIG. 5) between the closed-

circuit contacts

23, 41 and, rather than driving it into a large stagnant region, as shown in FIG. 2, forces it instead smoothly down a channel 64 to make contact with the arcing electrode 24. Although the arcing

electrodes

24, 39 are not as close as in the device discussed previously in connection with FIGS. 1 and 2, the high-velocity flow in the upper section of the flow path prevents upstream restriking during the interruption trial operation. Elimination of the close proximity arcing electrodes results in the minimum nozzle area vs. displacement curve, as illustrated by the line 66 in FIG. 3 of the drawings.

FIGS. 8 and 9 illustrate a modified type of contact and nozzle configuration in which a lost-motion connection 65 is provided between the inner nozzle member 39a and the outer main contact structure 66 comprising a plurality of relatively flexible main arcing contact fingers 41a. It will be noted that an accelerating compressing spring 68 is provided within a recess 69, which biases the stationary nozzle conducting member 39a toward the right, as viewed in FIGS. 8 and 9, in the direction of opening movement of the movable contact structure 26. Preferably, a flexible connection 70 insures electrical contact between the main contact fingers 41a and the inner arcing member 39a. It will be noted that the stationary spring seat 71 for the compression spring 68 also provides a stop member for limiting the rightward travel of the inner nozzle member 39a.

With the devices under consideration, it will be obvious that the more rapidly the arc transfer takes place, the sooner the pressure necessary for arc interruption will be obtained between the moving and

stationary pistons

20, 62. The modification set forth in FIGS. 8 and 9 suggests a means of enabling proper nozzle design with a non-floating center electrode of floating instead a portion of the outer electrode. The motion of the sliding electrode may be, as shown, by a spring mechanism 68, or other means may be provided such as magnetic coupling, as will be apparent to those skilled in the art.

From the foregoing description, it will be apparent that there has been provided improved contact and nozzle, or orifice configurations, which facilitate arc transfer, and prevent the arc from retransferring back to its initial position. In addition, the flow path has been improved so that the high-velocity gas flow effects rapid arc transfer.

Although there has been illustrated and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

I claim as my invention:

1. A fluid-blast type of circuit interrupter including, in combination, relatively stationary and movable contact structure separable to establish a main current are and a later residual current arc, the movable contact structure including an outer tubular main movable contact and an inner movable arcing contact insulated from the outer tubular main movable contact and projecting further toward the direction of the stationary contact structure than the outer tubular main movable contact, the relatively stationary contact structure including an outer main contacting portion and an inner hollow arcing portion collectively defining a nozzle-shaped stationary contact with smooth converging and diverging wall portions, means providing a blast of high-pressure fluid flow along the outer tubular main movable contact and through the nozzle-shaped stationary contact to eifect arc transfer to the inner movable arcing contact, and impedance means connected between the outer and inner movable contacts.

2. The combination according to claim 1, wherein the fluid-flow means comprises one or more accelerating coils constituting at least a portion of said impedance means.

3. The combination according to claim 1, wherein the inner hollow arcing portion of the relatively stationary contact structure is movable relatively ot the outer main contacting portion and biased in the direction of the movable contact structure.

4. A piston-type of fluid-blast circuit interrupter including a stationary operating cylinder and a movable piston assembly movable therein and carrying a movable contact structure, a relatively stationary cooperable contact structure separable to establish a main current arc and a later residual current arc, the movable contact structure including an outer tubular main movable contact and an inner movable arcing contact insulated from the outer tubular main movable contact and projecting further toward the direction of the stationary contact structure than the outer tubular main movable contact, the relatively stationary contact structure including an outer main contacting portion and an inner hollow arcing portion collectively defining a nozzle-shaped stationary contact with smooth converging wall portions, the movement of said piston assembly within said stationary operating cylinder providing a blast of high-pressure fluid flow along the outer tubular main movable contact and through the nozzle-shaped stationary contact to effect are transfer to the inner movable arcing contact, and impedance means including an accelerating coil movable with said movable piston assembly electrically connected between the outer and inner movable contacts.

5. The combination according to claim 4, wherein the inner hollow arcing portion of the relatively stationary contact structure is movable relatively to the outer main contacting portion and biased in the direction of the movable contact structure.

6. The combination according to claim 1, wherein the outer main contacting portion of the relatively stationary contact structure comprises a plurality of circumferentially-disposed somewhat flexible main contact fingers which extend over the outer tubular movable main contact in the closed-circuit position of the circuit interrupter.

7. The combination according to claim 1, wherein the inner movable arcing contact comprises a hollow venting tube, whereby double opposite venting action of the are products may take place for rapid circuit interruption.

8. The combination according to claim 4, wherein the inner movable arcing contact comprises a hollow venting tube, whereby double opposite venting action of the are products may take place for rapid circuit interruption.

9. The combination according to claim 1, wherein the 7 insulation between the outer and inner movable Contacts has a smoothly converging configuration.

References Cited UNITED STATES PATENTS 704,202 7/ 1902 Michalke 200146 2,281,385 4/ 1942 Saint-Germain et a1. 2,678,984 5/1954 Ramrath 200'-146 3,052,783 9/ 1962 Buron.

8 3,114,816 12/1963 Beatty. 3,238,340

3/1966 Lerch 335- 201 x FOREIGN PATENTS 4/1965 Germany.

, US. 01. X.R. 20 -144, 146