US2470611A

US2470611A - Circuit interrupter

Info

Publication number: US2470611A
Application number: US724425A
Authority: US
Inventors: Robert E Friedrich
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1947-01-25
Filing date: 1947-01-25
Publication date: 1949-05-17
Anticipated expiration: 1966-05-17

Description

May 17, 1949. R. E. FRIEDRICH 2,470,611

CIRCUIT INTERRUPTER Filed Jan. 25, 1947 Patented May 17, 1949 UNITED STATES PATENT OFFICE CIRCUIT INTERRUPTER Application January 25, 1947, Serial No. 724,425

(Cl. 20G-150) 9 Claims. 1

This invention relates to circuit interrupters, in general, and, more particularly, to arc-extinguishing structures therefor.

In interrupting devices utilizing self-generated iiuid flow for arc extinction, the pressures produced by the generating arc vary with the cur-- rent and most often become excessive at high currents, excessive from both the standpoints of that required for interruption and of the stresses applied to the containing chamber. My invention relates to means for limiting. the length of the ilow producing or pressure generating arc to prevent the occurrence of excessive pressures.

l am aware that heretofore different schemes have been proposed utilizing electromagnetic means or pressure-responsive means to eiiect shortening of the pressure arc in self-generated pressure type of circuit interrupters. However, such schemes have. suffered from the disadvantages, namely of' being complicated and causing the contact structures to become sluggish in operation because of such complications, and' furthermore, such schemes have been slow in operation. because of the Weight of the moving parts.

The object of my invention is to provide a high-speed relatively light arcing electrode arrangement, entirely separate from the Contact structure normally used to carry the load c'urrent and initially draw the arcs, which will be very sensitive to the pressure of the pressure chamber or the current conditions in the circuit to be protected.

Another object is to provide an arrangement of parts so as to readily facilitate the transfer of one terminal end of the pressure arc from the movable contact which normally establishesthe pressure arc tol an adjacently disposed movable arcing electrode whose motion is dependent upon the current being carried by the circuit.

Further objects and advantages -will readily become apparent upon a reading of the following specification taken inv conjunction with the drawing, in which:

Figure 1 is a side elevational View, partly in section, of a tank-type liquid break circuit interrupter embodying my invention and shown in the closed. circuit position;

Fig. 2 is an enlarged vertical sectional view through the left-hand arc-extinguishing unit of Fig. l, the' contact structure being shown. in the closed circuit position;

Fig. 3 is a. view similar to- Fig.. 2,. but showing. the disposition of the several' contacts during high current interruption immediately after by the reference numeral I2.

2 transfer has occurred to the movable arcing electrode;

Fig. 4 is a fragmentary view of a modiiied type of circuit interruptor employing electromagnetic means instead of pressure-responsive means for effecting motion of the movable arcing electrode, the contact structure being. shown in a position immediately after transfer of one terminal end of the pressure arc has taken place to the movable arcing electrode; and

Fig. 5 is a fragmentary sectional view taken along the line V-V 0f Fig. 2.

Referring to the drawing, and more particularly to Fig. 1 thereof, the reference numeral I designates a tank lled to the level 2 with a suitable arc-extinguishing fluid 3, in this instance circuit breaker oil. Depending from the cover 4 of the tank I are two terminal bushings 5 having aflixed thereto at their lower ends identical arc-extinguishing units, generally designated by the reference numeral 6.

vThe units 6 are electrically interconnected in the closed circuit position of the interruptor, as shown in Fig. 1, by a conducting bridging member 'I, the latter being reciprocally vertically operated by an insulating lift rod 8 actuated by suitable mechanism (not shown).

Referring more particularly to Fig. 2, it will be observed that there is provided contact structure including a pivotally mounted pressure-generating or rst movable contact 9 pivotally mounted at ID to the Wall of the casting Il I. The casting II forms a substantially confined pressure-generating chamber, generally designated A pair of externally disposed actuating arms I4, only one of which is shown in Fig. 2, are integrally formed with the contact 9 and extend externally of the unit 6'.

The pair of actuating arms I4 have apertures I5 provided at their outer ends through which extends in loose fashion a pin I6, the latter being affixed to the upper end of an insulating operating rod I'I. Preferably, integrally formed with the operating rod I'I is a collar I81which serves as a lower seat for a compression spring I9, the upper end of which seats upon a washerv 2I loosely movable upon the rod I1 and making abutting engagement with the lower ends 22 of the actuating arms I4.

Threadedly secured to the lower end of the operating rod I1 is a head 23 which serves as a lower seat for an accelerating compression spring 2'4, the upper end of which makes abutting engagement with the lower metallic plate 25 of the unit 6. The opposed outer ends of the conducting bridging member 1 are bent up wardly and form lower movable or second contacts 29 which cooperate with a relatively stationary intermediate contact 21 to establish an interrupting arc 28, more clearly shown in Fig. 3.

Also cooperable with the relatively stationary contact 21 is the movable pivotally mounted pressure contact 9 which draws a pressure arc designated by the reference numeral 29 in Fig. 3.

Suitable passage means is provided, vented and configured to force fluid, in this instance oil, under pressure from the pressure arc 29 downwardly through two vertical flow passages 3Q from the pressure chamber I2 through a plurality of pairs, in this instance three, of inlet passages 3l, to ilow into intimate engagement with the interrupting arc 28 (Fig. 3) to pass through orifices 92 provided by insulating orifice plates 33 (Fig. 5) to pass in opposite directions out of the unit 6 through opposed vent passages 34 having a configuration more clearly shown by the dotted lines of Fig. 5.

The plate structure herein described and the normal contact structure is not a part of my invention and is more fully set forth and claimed in United States Patent application, Serial No. 465,244, filed November 11, 1942, now U. S. Patent 2,406,469, issued August 2'7, 1946, to Leon R. Ludwig, Winthrop M. Leeds and Benjamin P. Baker, and assigned to the assignee of the instant application.

My invention is concerned `with means ior shortening the length of the pressure arc 29 during the existence of high magnitude currents in the circuit controlled by the interrupter. In Figs. 1-3, I employ a pressure-responsive device generally designated by the reference numeral 31 and including a pressure-responsive piston 36 responsive to the pressure within the pressure chamber I2. The piston 38 has a stem 39 pivotally connected at 40 to a lever 4I. The lever 4I is pivotally mounted at a fixed pivot -42 provided by a pair of brackets 43, in this instance integrally formed with the casting I I.

Pivotally connected to the left-hand end of the level1 4I at 36 is a movable arcing electrode 44 having its lower end extending downwardly into the pressure chamber I2 through an aperture 45 formed in the upper wall of the casting II. A flexible conductor 46 electrically connects the arcing electrode 44' to the casting Il. A compression spring 41 is disposed between the piston 38 and the upper wall 48 of the piston chamber 49 and serves to bias the piston 38 downwardly to its at rest lower position as shown in Fig. 2. In this position, as shown, the movable arc'- ing electrode -44 is retracted to its upper position and remains well out of proximity to the contacts 9, 21.

Preferably, I employ an over-pressure relief valve means, generally designated by the reference numeral 50, and so disposed in the wall of the casting I I so that upon the operation thereof to relieve the pressure within the pressure chainber I2, the flow of gasses will facilitate transfer of the upper terminal end of the pressure arc 29 from the pressure contact 9 to the lower tip of the movable arcing electrode 44.

From the foregoing description, it will be apparent that in the closed circuit position of the interrupter, as shown in Figs. 1 and 2, the electrical circuit therethrough includes the terminal stud (not shown) extending exteriorly through the terminal bushing 5, casting Il, flexible shunt 5I, contact S, intermediate contact 21, lower contact 25 through the conducting bridging member l and through the right-hand arc-extinguishing unit i3 of the interrupter in an identical fashion to the right-hand terminal bushing 5 of the interrupter.

During the opening operation, suitable mechanism (not shown), which is responsive either to manual operation or to the existence of excessive currents in the circuit controlled by the interrupter, causes downward opening motion of the lift rod I3. The downward motion of the lift rod S causes corresponding downward motion oi the bridging member 1 and the lower movable or second contacts 255 in both units 6.

Also, the downward movement of the conducting bridging member 1 permits the compression spring 24 to cause downward opening motion of the operating rod i1.

The intermediate contact 21 is biased downwardly by a compression spring 52 to a limiting position as determined by a, flange portion 53 integrally formed with the intermediate contact 21. Thus, lowering of the contact 26 permits a short following travel of the contact 2, meanwhile making contacting engagement with the contact 2E. During this time the pin I5 is moving downwardly within the apertures I5 provided in the actuating arms I4, the spring biased washer 2i maintaining the contact 9 in contacting engagement with the intermediate Contact 21.

Thus, at the moment the flange portion 53 determines the extent of the following downward motion of the intermediate contact 21, the pin I6 has arrived at the lower end of the apertures I5. Further downward opening travel of the bridging member 1 causes substantially simultaneously the drawing of a pressure-generating arc 29 in the pressure chamber I2 and the drawing of an interrupting arc 28 within the interrupting chamber 54. Since the chamber I2 is substantially confined and the interrupting chamber 54 is vented out of the unit 6 through the exhaust passages 34' (Fig. 5) oil under pressure will flow downwardly from the pressure chamber I2 through the two vertical ovv passages 3@ to effect extinction of the interrupting arc 23 in a manner as previously described.

During the existence of relatively low or medium value currents in the circuit to be interrupted, it is desirable to permit the pressure are 29 to attain its maximum length to thereby provide the pressure necessary to cause requisite fluid flow to pass toward the interrupting arc 28 to effect the latters extinction. rIhe pressure generated at the pressure-generating arc 29 is, other things being equal, dependent upon its length. Consequently, it is desirable to obtain a relatively long length of pressure arc 25J during low and medium value currents to obtain the requisite pressure for forcing oil toward the inter rupting arc 28.

Under these conditions of low or medium value currents, the pressure-responsive device 31 is not operable and the arc lengthens between the contacts 9, 21, not transferring under these conditions to the movable arcing electrode 44.

However, during the existence of relatively high currents in the circuit controlled Iby the interrupter, it is desirable to shorten the length of the pressure arc 29 to avoid the attainment of excessive pressures within the pressure chamber I2. Under these high current conditions, the pressure Within the pressure chamber I2 will cause upward movement of the pressure-responsive piston 38 against the downward biasing action exerted by the compression spring 41 to thereby cause through the medium of the lever 4l downward motion of the tip of the movable arcing electrode 44 to the region immediately adjacent to the intermediate contact 21 as shown in Fig. 3. Also, the pressure relief valve 59 will open to permit gas and oil to pass out of the apertures 55 associated therewith.

It will. be noted that there is a partially looped electrical path including the arc 29 inasmuch as the pressure-generating contact 9 is in its` open position substantially perpendicularly to the axial length of the unit E, Since the magnetic forces in a loop tend to expand the loop, it will be apparent that the electromagnetic forces exist," ing in the partial loop circuit as aorded by the contacts 9, 21 will facilitate transfer of the upper terminal end of the pressure arc 29 from the contact 9 to the lower tip of the movable arcing electrode 44 as shown in. Fig, 3. Also the gas and oil flow passing out of the chamber I2 through the apertures 55 provided in the over-pressure relief valve means 5B will facilitate such transferring action to take place.

It will consequently be apparent that I have provided a structural disposition of the several parts so that the electromagnetic forces in thev circuit cooperate with the opening of the valve 59 to cause transfer of the pressure arc 29 to the electrode 44 where itsl length. is considerably shortened as compared to what. it would be if it were permitted to be lengthened by the con-- tinued opening motion of the pivotally mounted pressure contact 9. Thus, I have provided a pressure-responsive device which is operable during the existence of high currents in the circuits to be protected to cause shortening of the length of the pressure arc 29 by the transfer of the upper terminal end thereof to the movablev arc- .f

ing electrode 44.

The arcing electrode 44 is made lightweight in construction and the piston is designed to ac,- celerate the downward movement of the arcing electrode 44 at a rapid rate to make the transfer effective before the rocker contact 9y is fully open; and the movement of the pressure-generating contact 9 is in no way impeded.

In Fig. 4 I have sho-wn a modified type of unit 59 with arc-shortening means in which electromagnetic forces in the circuit are employed. More specifically, I have shown an electromagnetic device or means generally designated by the reference numeral 59 and including an iron armature 6| secured to the upper end of the movable arcing electrode M, A tension spring 62 has its upper end secured to a bracket 63 aflixed to the contact foot 64, the latter being threadedly secured and clamped to the terminal stud 65 passing interiorly through the terminal bushing 5.

The lower end of the tension spring B2 is secured to the upper end of the armature 6l and biases the latter upwardly to a limiting position as determined yby a flange 69 secured to the electrode 44 interiorly of the pressure chamber I2. As before, a flexible conductor 46 electrically connects the arcing electrode 44 to the casting H.

A series coil 61 is provided encircling the armature 6| to cause the downward actuation of the l same during high current interruption. To insure the passage of series current entirely through the lcoil B1, I have insulated the casting Il from the contact foot 64 by an insulating ring 68 and insulating bolts 69. Thus, in the closed circuit position of the interruptor (not shown) the electrical path includes terminal stud t5, contact foot 64, series coil 61, casting l I, exible conductor 5l, contact 9, contact 21 and lower conta-ct 2G (not shown), through the conducting cross-bar 1 to the right-hand unit 59 of the interrupter.

During the existence of low or medium value currents in the circuit controlled by the interrupter, the electromagnetic forces exerted in the series coil 61' will not be sufficient to cause downward movement of the armature 6| and arcing electrode 44 afiixed thereto against the upward biasing action exerted by the tension spring 52. Thus, the arcing electrode il will remain in its upper at rest position during the existence of low or medium value currents in the circuit.

It is only during the existence of high current conditions in the circuit controlled by the interrupter that. the electromagnetic device 59 will function to draw the armature t! downwardly' as shown in Fig. 4. In this position the pressure arc 29 will transfer in a manner as previously mentioned, being assisted in this action both by the opening of the pressure relief valve 59 and by the partially looped circuit as afforded by the contacts 9, 21.

It will be observed that the electromagnetic device 60 functions even before separation of the contact structure. In other words, the armature 60 will be drawn downwardly and the arcing electrode 44 will be in its lower state prior to separation of the contacts 9, 21. Thus, the electromagnetic device 60 anticipates the over-pressure conditions` even before the separation of the contacts 9, 21 and, hence operates to have the lower tip of the electrode 4i immediately adjacent to the Contact 21 at the time that the pressure contact 9 initially separates therefrom to draw the pressure arc 29.

From the foregoing description of two embodiments of my invention, it will be apparent that I have provided an improved device which may assume either the form of an electromagnetic device or a. pressure-responsive device which will y serve during the interruption of relatively high currents to cause shortening of the length of the pressure arc 29. The device does not impede the operation during low or medium value of currents. It is lightweight in construction and is very rapid in operation. Also, it is readily adaptable to existing contact constructions involving in no way the complicating of the mechanis-m employed to effect opening of the contact structure.

A distinct advantage of my invention is that since it is entirely separate from the mechanism operating the contact structure; it does not complicate the latter and is high speed in operation.

Although I have shown and described specic structures, it is to be clearly understood that the same were merely for the purpose of illustration and that changes and modications may readily be made therein by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim as my invention:

l. In a circuit interrupter of the duid blast type, a relatively stationary contact, a movable contact separable from the stationary contact in one direction to establish an arc, a separate and independently movable arcing electrode disposed in proximity to the relatively stationary contact and adapted for movement in the opposite direction, and means responsive to the magnitude of the current being interrupted for causing movement of the arcing electrode in the said opposite direction to thereby cause transfer of the terminal of the arc from the movable contact to the arcing electrode to shorten the length of the arc.

2. In a circuit interrupter of the liquid blast type, a relatively stationary contact, a first movable contact separable in one direction from the stationary Contact to establish a pressure-generating arc, a second movable contact separable in the opposite direction from the stationary contact to establish a second serially7 related interrupting arc, passage means so Vented that pressure from the pressure-generating arc causes liquid to flow toward the interrupting arc to extinguish the latter, a separate and independently movable arcing electrode disposed in near proximity to the relatively stationary and rst movable contacts and adapted to move in the said opposite direction toward the relatively stationary contact, and means responsive to the magnitude of the current being interrupted for causing the said motion of the arcing electrode to thereby cause upon excessive current conditions transfer of one end of the pressure-generating arc from the iirst movable contact to the arcing electrode to shorten the arc.

3. In a circuit interrupter of the fluid blast type, a substantially enclosed arc extinguishing unit, a relatively stationary Contact, a movable contact separable from the stationary contact in one direction to establish an arc, a separate and independently movable arcing electrode for moving in the opposite direction disposed laterally of the aforesaid contacts, means responsive to the magnitude of the current being interrupted for causing movement of the arcing electrode in the said opposite direction to thereby cause transfer of the terminal end of the arc from the movable contact to the arcing electrode to shorten the length of the arc, and over-pressure valve means disposed in the wall of the extinguishing unit laterally of the arcing electrode and opened upon excessive pressure to facilitate the transfer.

4. In a circuit interrupter of the liquid blast type, a substantially enclosed arc extinguishing unit, a relatively stationary contact, a first movable Contact separable in one direction from the stationary contact to establish a pressure-generating arc, a second movable contact separable in the opposite direction from the stationary contact to establish a second serially related interrupting arc, passage means so Vented that pressure from the pressure-generating arc causes liquid to floW toward the interrupting arc to extinguish the latter, a separate and independently movable arcing electrode adapted to move in the said opposite direction toward the relatively stationary contact and disposed laterally of the said rst movable contact, means responsive to the magnitude of the current being interrupted for causing the said motion of the arcing electrode to thereby cause upon excessive current conditions transfer of one end of the pressure-generating arc from the rst movable contact to the arcing electrode to shorten the arc, and over-pressure valve means disposed in the Wall of the extinguishing unit laterally of the arcing electrode and opened upon excessive pressure to facilitate the transfer.

5. In a circuit interrupter, a pair of contacts separable to establish a pressure-generating arc, a second pair of contacts separable to establish an interrupting arc, fluid iioW passage means vented and configured to cause fluid under pressure to flow from the pressure-generating arc toward the interrupting arc to extinguish the latter, a separate and independently movable arcing electrode disposed substantially laterally of the first said pair of contacts, and pressureresponsive means responsive to the pressure adjacent the pressure-generating arc to cause motion of the arcing electrode in a direction to shorten the gap distance between the rst said pair of contacts, the arrangement functioning to cause transfer of one terminal end of the pressure-generating arc to the arcing electrode under high current conditions to thereby shorten the length of the pressure-generating are.

6. In a circuit interrupter of the liquid blast type, a relatively stationary contact, a first movable contact separable in one direction from the stationary contact to establish a pressure-generating arc, a second movable contact separable in the opposite direction from the stationary contact to establish a second serially related interrupting arc, passage means so vented that pressure from the pressure-generating arc causes liquid to flow toward the interrupting arc to extinguish the latter, a separate and independently movable arcing electrode adapted to move in the said opposite direction toward the relatively stationary contact, and pressure-responsive means responsive to the pressure adjacent the pressure-generating arc to cause motion of the arcing electrode, the arrangement functioning to cause transfer of one terminal end of the pressure-generating arc to the arcing electrode under high current conditions to thereby shorten the length of the pressure-generating arc.

7. In a circuit interrupter of the liquid blast type, a substantially enclosed arc extinguishing unit, a relatively stationary contact, a rst movable contact separable in one direction from the stationary contact to establish a pressuregenerating arc, a second movable contact separable in the opposite direction from the stationary contact to establish a second serially related interrupting arc, passage means so vented that pressure from the pressure-generating arc causes liquid to flow toward the interrupting arc to extinguish the latter, a separate and independently movable arcing electrode adapted to move in the said opposite direction toward the relatively stationary Contact, pressure-responsive means responsive to the pressure adjacent the pressuregenerating arc to cause motion of the arcing electrode, the arrangement functioning to cause transfer of one terminal end of the pressuregenerating arc to the arcing electrode under high current conditions to thereby shorten the length of the pressure-generating arc, and overpressure valve means disposed in the Wall cf the extinguishing unit laterally of the arcing electrode and opened upon excessive pressure to facilitate the transfer.

S. In a circuit interrupter, a pair of contacts separable to establish a pressure-generating arc, a second pair of contacts separable to establish an interrupting arc, fluid ilow passage means vented and congured to cause fluid under pressure to flow from the pressure-generating arc toward the interrupting arc to extinguish the latter, a separate and independently movable arcing electrode disposed adjacent to the first said pair of contacts, and electromagnetic means responsive to current in the circuit to cause motion of the arcing electrode in a direction to shorten the gap between the rst said pair of contacts, the arrangement functioning to cause transfer of one terminal end of the pressure-generating arc to the arcing electrode under high current conditions to thereby shorten the length of the pressure arc.

9. In a circuit interrupter, a substantially enclosed arc extinguishing unit, a pair of contacts separable to establish a pressure-generating arc, a second pair of contacts separable to establish an interrupting arc, iluid flow passage means vented and configured to cause iluid under pressure to flow from the pressure-generating arc toward the interrupting arc to extinguish the latter, a separate and independently movable arcing electrode, electromagnetic means responsive to current in the circuit to cause motion of the arcing electrode in a direction to shorten the gap between the iirst said pair of contacts, the arrangement functioning to cause transfer of one terminal end of the pressure-generating REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,904,519 Paul Apr. 18, 1933 FOREIGN PATENTS Number Country Date 653,248 Germany Nov. 18, 1937