US3549842A - Fluid-blast circuit interrupter with piston assembly and electromagnetic driving means - Google Patents

Description

United States Patent [72] Inventors Appl. No. Filed Patented Assignee William H. Fischer Pittsburgh; Russell E. Frink, Forest Hills, Pittsburgh, Pa.

Nov. 21, 1966 Dec. 22, 1970 Westinghouse Electric Corporation Pittsburgh, Pa.

a corporation of Pennsylvania FLUID-BLAST CIRCUIT INTERRUPTER WITH PISTON ASSEMBLY AND ELECTROMAGNETIC DRIVING MEANS 9 Claims, 4 Drawing Figs.

Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attarneys-A. T. Stratton, C. L. McI-lale and W. R. Crout ABSTRACT: An improved fluid-blast circuit interrupter is provided utilizing magnetic forces of repulsion and attraction to accelerate the opening movement of a movable piston assembly carrying the movable contact structure within an operating cylinder. An accelerating coil is carried along with the movable piston assembly and is connected serially into the circuit when the main-current arc is transferred to a centrally located movable arcing contact. A movable repulsion-coil driver unit is also connected, by a piston-rod structure, to the aforesaid movable piston assembly, the latter carrying the movable contact structure and movable arcing contact.

Additionally, the movable repulsion-coil driver unit itself carries a separable contact structure, which opens during the initial portion of the opening operation, and thereby inserts into series circuit the three magnetic accelerating coils. These coils, by their magnetic forces of repulsion and attraction, serve to assist the opening action of the operating mechanism in driving the movable piston assembly to its fully open-circuit position, thereby forcing fluid flow through the transferred are at the main separable contact structure to effect the extinction thereof.

PATENTED DEC22 I970 v 35491842 sum 1 0F 2 v INVENTORS William H. Fischer and Russell E. Frink FIG. I.

BY flaw W ATTORNEY WITNESSES As well known by those skilled in the art, the general trend in metal-clad switchgear over the past decade has been to higher voltages and to higher interrupting ratings. In 1955, approximately 80 percent of the production of a large electrical company was 5-kv. switchgear. In 1965, for example, the same manufacturer accounted for only 4.7 percent of his total switchgear production in 5-kv. units. ln addition to this general trend to higher voltage switchgear, the trend has been to higher interrupting ratings for circuit breakers. Up until -1957, the highest interrupting rating available in metal-clad switchgear was 500-mva. In that year, the first 750-mva. breakers were made available. In 1958, metal-clad switchgear with 1,000-mva. breakers were made available. Currently, in 1966, 34.5-kv. metal-clad switchgear with breakers having an interrupting capacity of 1,500-mva. are now for the first time available.

The first requirement for any line of switchgear is a reliable circuit breaker. Various types of interrupters have been proposed. However, to increase the voltage and interrupting ratings, it has been proposed to use puffer-type structures. Basically, the puffer concept is not new. It consists essentially of a pair of separable contacts, a piston and a cylinder all mounted in a reservoir containing a suitable arc-interrupting gas. Note U.S. Pat. No. 3,114,815 Easley et al. in this connection. The contacts and piston are mounted in such a way that as the contacts are parted, the piston moves to drive the gas in the cylinder through the arc to interrupt it. Such devices were investigated as long as years ago using the then available interrupting gases. A moderate degree of success was attained at that time. However, the devices were too inefficient to warrant further development.

The discovery of the ability of sulfurhexafluoride (SP gas to interrupt an arc gave the puffer interrupter a new boost, and the first commercial application of the puffer interrupter was a load-break disconnecting switch capable of switching load currents at voltages up through a 16l-kv. on a single break.

Following this, a series of prototype puffer interrupters were built with the final one being capable of interrupting 50,000 amperes at 22-kv. across a single break. However, the back pressure in the operating cylinder created by the arc required a piston-driving force of 10,000 to 12,000 pounds for interruption of the highest currents. This would require too large a mechanism to make this a practical breaker. At this point in the development period, the discovery was to use a magnetic puffer. This would provide a good interrupter, and the power to operate it would not be too great. It was s proposed to use the short circuit current to drive the piston. Experience with magnetic air circuit breakers has shown the tremendous force available from coils carrying fault current. It was proposed to shunt this current into coils and let them do the work of mechanically driving the piston.

A series of calculations was made to determine what force could be obtained from coils carrying high current. The calculations were based on a system of 3-10 inch diameter 10- turn coils arranged for attraction and repulsion over a 7 inch stroke. These calculations showed that a 21,000 ampere short circuit current through these coils would produce a force of 12,100 pounds at the beginning of the stroke. A 42,000 ampere short would produce a force of 48,000 pounds. The discovery was made that here was a means of obtaining the high force required to drive the piston for the circuit interrupter. Accordingly, a general object of the present invention is to provide an improved fluid-blast circuit interrupter having magnetic means serially connected into the electrical circuit, and taking advantage of the short circuit energy to improve the fluid-blast operation of the interrupter.

Another object of the present invention is to provide an improved fluid-blast type of circuit interrupter having improved piston-operated means associated therewith, and electromagnetic driving means to assist in the operation of said piston means.

Another object of the present invention is the provisionof an improved fluid-blast circuit interrupter in which a plurality of accelerating coils are used to assist in the operation of the associated piston assembly to more rapidly generate fluid under pressure, which'is subsequently ejected intothe arcing region to rapidly effect the extinction thereof.

Another object of the present invention is the provision of an improved fluid-blast circuit interrupter, having highly effective piston-moving means; and fluid-directing means associated therewith.

Still a further object of the present invention is the provision of an improved fluid-blast circuit interrupter of compact size, and operating in a highly efficient manner to quickly generate the required amount of high-pressure fluid, such as gas, and to effectively direct the gas under high pressure toward the established arc to effect circuit interruption. Still a further object of the present invention is the provision of animproved fluid-blast circuit interrupter having a stationary operating cylinder with a cylinder head closing one end thereof, in which a stationary accelerating coil is positioned, and providinga movable piston assembly carrying the movable contact structure in which a second accelerating coil, which is movable, is carried to assist in the opening and fluid-compressing stroke.

In application filed Sept. 1, 1966, now U.S. Pat. No. 3,524,958 Ser. No. 576,616, by Russell E. Frink, and assigned to the assignee of the instant application, there is illustrated and described a novel fluid-blast circuit interrupter having piston means associated therewith, which is assisted by an electromagnetic driving means, which is inserted into the series electrical circuit during the opening operation. It is still a further object of the present invention to improve the interrupting circuit'interrupter of the aforesaid patent application rendering it of highly efficient operation and of compact dimensions.

In application filed Sept. 1, 1966, now U.S. Pat. No. 3,524,959 Ser. No. 576,739, by Russell E. Frink, and assigned to the assignee of the instant application, there is illustrated and described a novel fluid-blast circuit interrupter incorporating piston means assisted by an electromagnetic driving structure including a pair of accelerating coils, and utilizing arcing-hornmeans to effect arc transfer, and consequent insertion of the two accelerating coils into the circuit during the opening operation. It is a further object of the present invention to improve upon the transfer-arcing means of the aforesaid patent application to provide an improved fluidblast circuit interrupter of highly efficient operation and operable in a very short span of time, such, for example, as 3 cycles.

In application filed Sept. 1, 1966, Ser. No. 576,707, by William H. Fischer, and assigned to the assignee of the instant application, there is disclosed movable arcing-horn means for effectively inserting electromagnetic means, including a pair of accelerating coils, into the electrical circuit to augment the piston-driving effect of an associated fluid-moving means. It is still a further object of the present invention to improve upon the movable arcing-horn means of the aforesaid Fischer application to provide an improved circuit interrupter of compact and highly efficient construction.

As well known by those skilled in the art, a fluid-blast circuit interrupter utilizing piston means for fluid-pressure generation, and a subsequent forcing of the fluid under pressure into the established arc, the mechanical effort required of the operating mechanism becomes more severe during the interruption of high-amperage fault currents. If the mechanical driving effort is provided exclusively by the piston-operating arrangement, to accommodate high-current fault interruption, an extremely powerful operating mechanism is required. In an effort to reduce the power requirements imposed upon the associated operating mechanism, it is desirabie to provide some means utilizing the energy in the associated electrical circuit to assist the mechanical requirements of the moving piston means during fault-current interruption. By so doing, it results that the power requirements of the operating mechanism may be held to a minimum. In other words, for low, or load-current interruption, the power supplied by the associated operating mechanism may be sufficient in itself to provide the desired piston-driving effort suitable for high-pressure gas generation. On the other hand, during heavy fault-current interruption, a desirable assist is provided by the electromagnetic means, as set forth in the present invention, as described hereinafter.

As set forth in application Ser. No. 576,616 if a pair of accelerating coils have the windings suitably arranged, there will be an attractive force set up between the two coils. On the other hand, the pair of coils may be so wound as to provide a repulsive magnetic force existing between the coils. It is a further object of the present invention to incorporate these attractive and repulsive magnetic forces to assist in the fluid driving effort of a piston assembly operated in conjunction with a fluid-blast circuit interrupter. I

Certain features of the structure are set 'forth and claimed in application filed Sept. 1, l966, Ser. No. 576,740 by Russell E. Frink and William H. Fischer, and assigned to the assignee of theinstant application. The broad concept of using three accelerating coils in series for additional electromagnetic assistance is set forth and claimed in application filed Sept. 29, I966, now U.S. Pat. No. 3,531,608 Serial No. 582,925, by Edmond Bateman, and likewise assigned to the assignee of the instant application.

In accordance with a preferred embodiment of the invention, there is provided a stationary operating cylinder containing a suitable arc-extinguishing gas, such as sulfurhexafluoride (SF gas, at a pressure of say 75 p.s.i. One end of the aforesaid stationary operating cylinder is closed by a stationary piston head having a stationary accelerating coil encapsulated therein. Movable longitudinally within the stationary operating cylinder'is a movable piston assembly carrying the movable contact structure, the latter comprising an outer main contact and an inner arcing contact insulated from the outer main contact. Associated with the movable piston assembly is a movable accelerating coil. Two guide rods mechanically interconnect the movable piston assembly through the closed end of the operating cylinder with a movable driving assembly-or unit, the latter comprising a movable repulsion coil. A stationary contact assembly is situated adjacent the open end of the stationary operating cylinder, and comprises a tubular main contact for venting the arc gases. In addition, a movable nozzle insulating member moves over the stationary main contact with the movable piston assembly to effectively direct the compressed gas flow through the stationary tubular vented main contact.:The' arrangement is such that during the opening operation the main arc, established between the main contacts, is carried by the gas flow to impinge onto the movable arcing contact tothereby insert serially into the electrical circuit being interrupted the piston accelerating coil. A second pair of main contacts is provided forming an auxiliary break to serially connect the stationary cylinder head coil and the moving repulsion coil of the driver unit into the electrical circuit being interrupted. Thus, the initial mechanical movement of the movable piston assembly, as supplied by a conventional mechanism, is augmented and assisted by the electromagnetic driving means including a plurality of, such as three, accelerating coils, two moving and one stationary, inserted serially into the electrical circuit. This is particularly advantageous during heavy fault-current interruption.

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

FIG. 1 is a vertical sectional view of a fluid-blast circuit interrupter embodying principles of the present invention, the contact structure being shown in the closed-circuit position;

FIG. 2 is a longitudinal sectional view taken through the fluid-blast type circuit interrupter ofFlG. l, the contact structure being illustrated in the partially open-circuit position;

FIG. 3 is a fragmentary view showing the initial establishment of the main current arc; and,

FIG. 4 is a schematic view of the coil connections and separable contact structure, with the circuit breaker being shown in the open-circuit position.

Referring to the drawings, and more particularly, to FIG. 1 thereof, the reference numeral 1 generally designates a fluidblast circuit interrupter. As shown in FIG. 1, generally, the fluid-blast circuit interrupter 1 comprises an upstanding insulating casing 2 formed of a suitable weather-proof material, such as porcelain, for example, having a pair of flange rings 3, 4 cemented to the upper and lower ends thereof. Secured to the upper end of the casing 2, as by a plurality of bolts 7, is an upper conducting line terminal cap 8 having a line connection 9, the latter being connected to the external lead L Extending downwardly centrally within the top metallic casting 8 is a stationary tubular vented contact, designated by the reference numeral 10, and making closed contacting engagement with a main movable annular contact 11, which constitutes a part of a movable contact structure, generally designated by the reference numeral 12. Preferably, the lower end of the stationary tubular venting contact 10 is slotted to form a plurality of resilient contact fingers 10a.

The movable contact structure 12, in addition, comprises an arcing-horn means 14, which, together with the movable contact structure 12, is carried by a movable piston 16 secured to a pair of piston rods l7, 18, the latter being mechanically driven by a suitable operating mechanism, more fully described hereinafter. 1

It will be noted that the movable piston member 16 reciprocally operates within a stationary operating cylinder 19 supported on a stationary annular insulating support ring 20, which is secured, as by bolts 200, both to the casing 2 and to a conducting base 23. The conducting base 23 is supported up in the air an adequate distance by an insulating pedestal 13.

It will be observed that the piston rods 17, 18 extend through openings 24 provided in the stationary base portion 25 of the operating cylinder 19, and are bolted, as at 26 and 27, adjacent their lower ends to a movable driver unit 28, which, in turn, is pivotally connected, as at 30, to a floating link 31, pivoted to a rotating crank-arm 33movable with a rotatable crankshaft 34.

The crankshaft 34 extends through a seal 35, and has an external crank-arm 36 provided at its outer extremity, which is mechanically connected, by insulating linkage means 37, to a suitable operating mechanism at ground potential, generally designated by the reference numeral 38. From the foregoing description, it will be apparent that functioning of the operating mechanism 38 will effect closing and opening rotative movement of the rotatable crankshaft 34, and hence vertical opening and closing movement of the piston rods 17, 18 and movable contact structure 12 with respect to the stationary contact 10.

It will also be obvious that downward opening movement of the piston 16, as effected by the operating mechanism 38, will compress a suitable arc-extinguishing fluid 40, such as sulfurhexafluoride (SF gas, within the region 41 below the movable piston 16, and force this compressed arc-extinguishing gas 40 upwardly through suitably provided apertures 43 in a conducting supporting spider member 22 and through a nozzle insulating member 45 adjacent the established main current are 47 (FIG. 3).

As mentioned, the movable contact structure 12 comprises the annular movable contact 11 and the centrally located arcing horn 14, which is insulated from the annular movable main contact 11 by a perforated insulating plug, designated by the reference numeral 48.

The piston assembly 49 additionally comprises a movable accelerating coil 50, which is electrically connected at one of its terminal ends 50a (FIG. 4) to the central movable arcing horn 14. The other terminal 50b of the movable accelerating coil 50 is electrically connected, by a strap connector 51 to one of two conducting piston rods, 17, 18, which extend through the openings 24 in the head portion 25, which closes the lower end of the stationary operating cylinder 19.

"The other guide rod 18, which is preferably conducting, also makes electrical contactwith the annular main contact structure- 11, as does the conducting piston rod 17.

As viewed in FIGS. 1, and 2, the two piston rods 17, 18 are secured to a movable repulsion coil driving assembly 28, which includes a repulsion coil 53 and a movable set of contact fingers 54. As shown, the contact fingers 54 are seated in recesses 55 provided in a conducting supporting member 56, the latter, in turn, being secured, as by welding 57, to a movable end conducting plate 58. Compression springs 59 may be employed, as indicated, to bias the two main contact fingers 54 inwardly against a stationary main contact 61 in the closed position, which is electrically connected by a strap connection 62 to the conducting base 23 and hence to the terminal 64.

From the foregoing, with reference to FIGS. 1 and 2, it will be noted that the movable piston accelerating coil 50, which travels with the piston assembly 49, is connected in parallel with the separable main contact structures 10, 12. Additio rialiy, it will be observed that the stationary base accelerating coil 65, disposed in the base, or head portion 25 of the operating cylinder 19, is electrically connected in series with the repulsion coil 53 carried by the driving element 28, both coils 53, 65 being connected in electrical parallel across the separable contacts 54, 61. In more detail, a flexible lead 67 and a stationary strap'connection 68 electrically connects the stationary accelerating coil 65 with one terminal 53b of the movable repulsion coil 53 carried by the driving element 28.

1h the'closed-circuit position, as illustrated in FIG. 1, it will be observed that the electrical circuit passes from the terminal connection 9'to the stationary main contact 10, to the annular movable contact 11, legs 21 of movable main contact supportingspider structure22 to the conducting guide rods 17, 18, to th'eend conducting plate 58, and by way of the main contact fingers 54 to the stationary main contact 61, and thence by way of the conducting supporting base 63 to the other line terminal 64.

, During the opening operation, suitable means, such as a current-responsive relay (not shown) actuates the associated operating mechanism 38 to effect initial downward compressing action of the movable piston assembly 49. This means may assume the form, as shown, of the rotatable crankshaft 34 and link 31 pivotally connected to the movable piston as sembly 49 and driving unit 28.

The initial downward opening movement of the movable contact structure 12 and movable piston assembly 49, as effected by the operating mechanism 38, causes an initial compression of gas, such as sulfurhexafluoride (SF gas 40, to force the same in an upward direction through the movable nonle element 45. The gas flow quickly effects transfer of the main current are 47 (FIG. 3) drawn between the separable contacts 10, 11 to the center movable arcing born 14, as shown in FIG. 2, which action thereby electrically connects into series circuit the movable accelerating coil 50. The transferred arc is indicated by the reference numeral 69 in FIG. 2.

Because of the fact that the movable driving element 28 is mechanically connected by the guide rods 17, 18 to the movable piston assembly 49, the main separable contact fingers 54 will also make disengagement with the stationary contact 61, thereby inserting electrically into the circuit the two accelerating coils 53, 65. Reference may be had to FIG. 4 in this connection.

- The electromagnetic means 70, which utilized to assist the mechanical opening movement of the movable piston assembly 49, consequently, comprises the two accelerating coils 50, 65 which are magnetically attracted to each other. In addition, the two accelerating coils 53, 65 are repelled, so that utilization is made of both attractive and repulsive magnetic forces to augment the mechanical action exerted during the opening movement by the associated operating mechanism 38.

As well known by those skilled in the art, the puffer-type circuit interrupter has been known for many years, and has given a very good performance. It has, however, certain inherent advantages over the two-pressure or dual-pressure v scheme, as shown, for example, in U.S. Pat. No. 3,057,983 Yeckley et al., issued Oct. 9, I962. The puffer design is self-.

force needed to drive it at large fault currents is quite large.

One solution for overcoming this disadvantage has been the.

magnetic puffer, as set forth in the aforesaid patent applications.

As set forth above, the present invention is concerned with a three-coil magnetic puffer interrupter in which two accelerating coils move, and one accelerating coil is stationary.

The following is the sequence when the breaker opens to interrupt a fault. The moving piston assembly 49 moves downwardly. An are 47 (FIG. 3) is drawn between the moving contact 11 and stationary contact 10. As flow is established out the hollow stationary contact 10 the arc transfers from the moving contact 11 to the arc probe 14.

The probe 14 is connected to the attraction coil 50, which now has full fault current flowing through it. The other end of coil 50 is connected to the tie-rod 17. At the same time that this is happening, the contacts 54, 61 have parted. Contacts 54, 61 short out coils 53 and 65 in the breaker closed position. The repulsion coil 53 and the stationary base coil 65 are now transferred into the electrical circuit. Coils 53 and 65 are wound to repel each other, coils 50 and 65 are wound to attract. These magnetic forces drive the moving piston assembly 49 downwardly helping to overcome the retarding force of the gas pressure.

From the foregoing description it will be apparent that there has been provided a novel electromagnetic puffer-type fluidblast circuit interrupter in which three accelerating coils are utilized in an advantageous manner, and in which one of the coils, namely a repulsion coil, is utilized as an essential element in a movable driving assembly 28, which assists in moving the movable piston assembly 49.

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

We claim:

1. A fluid-blast circuit interrupter including a first relatively stationary main contact structure, a cooperable movable main contact structure cooperable therewith to carry the line current in the closed position of the circuit interrupter, said movable main contact structure establishing arcing including a main movable first contact portion and a movable first probe contact portion movable together with the first arcing probe portion insulated from the main movable first contact portion, a first accelerating coil electrically connected between the movable main first contact portion and the movable first arcing probe contact portion, a second separable series pair of cooperable contacts one stationary and the other movable separable in response to separation of the first contacts, me ans connecting said other movable contact with said main movable first contact portion, a second and third accelerating coils connected in series and the series combination of these two coils only being electrically connected in parallel across said separable series pair of second cooperable contacts, piston means for forcing fluid under pressure toward said arcing to effect the extinction thereof, electromagnetic means for assisting in the fluid-driving motion of said piston means including said first, second and third accelerating coils, whereby separation of the first relatively stationary contact from the first movable contact structure will electrically insert said first accelerating coil, and separation of said second separable contact structure will electrically insert the second and third accelerating coils into the circuit.

2. The combination according to claim 1, wherein said piston means includes an operating cylinder and a movable piston movable therein to compress fluid and force the same against said arcing, said movable piston carrying said first movable contact structure and said first accelerating coil, said operating cylinder having a base portion for supporting said second accelerating coil, and a driver unit mechanically connected to said movable piston and carrying said third accelerating coil.

3. The combination according to claim 2, wherein, operating linkage is mechanically connected to said movable driver unit.

4. The combination according to claim 3, wherein the operating cylinder is supported upon a conducting base portion and said one stationary second contact, and a terminal of said second accelerating coil electrically connected to said conducting base portion.

5. In combination, means defining an upstanding insulating casing having an upper terminal cap supported thereon, a vented stationary contact extending downwardly from the central portion of said cap, an upstanding stationary operating cylinder disposed within said casing and having reciprocally movable therewithin a movable piston assembly carrying a first accelerating coil and also movable contact structure, the latter comprising a movable main'contact and an arcing contact insulated from the movable main contact, said first accelerating coil being electrically connected between said movable main contact and said movable arcing contact, said stationary operating cylinder having a lower base portion having a second stationaryaccelerating coil associated therewith, a movable driver unit carrying a third accelerating coil which is electrically connected in series with said second accelerating coil, a stationary auxiliary contact associated with the base portion of said operating cylinder, a movable auxiliary contact carried by said driver unit, said second and third accelerating coils being in electrical parallel across said pair of separable auxiliary contacts, said first and second accelerating coils being wound so as to be magnetically attracted to each other and said second and third accelerating coils being wound so as to be magnetically repelled.

6. The combination according to claim 5 wherein at least one piston rod is conducting and mechanically interconnects the piston and driver unit assemblies, and the electrical connection between the first and third accelerating coils being carried by said conducting piston rods.

7. The combination according to claim 1, wherein the first movable contact structure comprises an outer movable main contact and an inner movable arcing contact insulated from the outer movable main contact.

8. A fluid-blast circuit interrupter including first terminal means, relatively stationary contact structure electrically connected to said first terminal means, cooperable movable contact structure separable from said relatively stationary contact structure to establish arcing, piston means including an operating cylinder having a closed end and a movable piston movable therein to compress fluid and force the same against said arcing, second terminal means, said closed end of the operating cylinder containing an accelerating coil having one terminal end thereof connected to said second terminal means, a movable driver unit carrying an accelerating coil, said movable piston also carrying an accelerating coil, said movable contact structure including an annular movable main contact and a concentrically arranged movable arcing horn, the movable accelerating coil carried by the movable piston being electrically connected in electrical parallel between said movable arcing horn and said movable annular main contact, said movable driver unit carrying a movable mam contact separable from a stationary contact, said stationary contact connected to said second terminal means, and the stationary accelerating coil in the head of said operating cylinder being electrically connected in series with the movable accelerating coil movable with the movable driver unit, and both of said latter-mentioned coils being in electrical parallel across the last-mentioned separable main contacts.

9. The combination according to claim 8, wherein the movable piston member carries a movable nozzle member to more efficiently direct the compressed arc-extinguishing fluid to effect are transfer to the movable arcing horn.

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