US2442199A - Circuit interrupter - Google Patents

Description

Milly 25, 1948 R. c. DlcKlNsoN :a1-AL 2,442,199

CIRCUIT INTERRUTER Filed Dec. 15, 1943 5 Sheets-Sheet 1 Patented May 25, 1948 UNITED STATES PATENT OFFICE CIRCUIT MERBUPTER Application December 15, 1943, Serial No. 514,362

Claims. l

This invention relates to improvements in circuit interrupters, and more particularly to arc extinguishing structures for circuit interrupters of the air break type.

In U. S. Patent 2,243,038, which issued May 20, 1941, to Leon R. Ludwig and which was assigned to the assignee of the instant application is shown and described an arc extinguishing structure for circuit interrupters of the air break type in which arc extinction is accomplished by the lateral movement of an established arc toward the closed ends of a series of tapered slots formed in spaced plates of insulating material. Lateral movement of the arc is obtained by a magnetic eld induced in plates of magnetic material disposed adjacent the arc receiving slots. This magnetic ield is also relied upon to produce a blast of un-ionized gas through the arc while the arc is held substantially immovable against the closed ends of the slots in the plates of insulating material.

Various improvements concerning the plate structure of such an arc extinguishing device to increase the voltage rating thereof are disclosed in U. S. Patent 2,243,039, which issued May 20, 1941, to Leon R. Ludwig and Merl E. Horn and which was assigned to the assignee of the instant application. Further improvements in the plate structure adjacent the arcing plates to prevent the formation of hot cathode terminals upon the arcing plates, thereby reducing the vaporization of the contact metal to a minimum so as to materially increase the breakdown voltage between the arcing plates, are set forth in U. S. Patent 2,242,905, which issued May 20, 1941, and which was assigned to the assignee of the present application.

In U. S. Patent 2,243,040, which issued May 20, 1941, to Leon R. Ludwig, Herbert L. Rawlins and Robert H. Nau and which was assigned to the assignee of the present application, the aforesaid type of arc extinguishing device was further improved by increasing the intensity of the gas blast through the arc as a result of utilizing gas evolving spacer strips between the slotted insulating refractory plates.

An improved venting arrangement for arc extinguishing structures of the foregoing type is disclosed in U. S. Patent 2,276,859, which issued March 17, 1942, to Robert H. Nau and which was assigned to the assignee of the instant application.

The principal object of our invention is to further improve the operation of circuit breakers of the aforesaid type so as to materially extend the interrupting capacity of such breakers with respect to both the current and voltage ranges interrupted.

More specifically, this invention relates to improvements in arc extinguishing devices of the 5 type comprising a plurality of spaced insulating plates having slots formed therein which, when aligned, form a substantially V-shaped arcing passage in which an established arc is magnetically moved toward the closed ends of the slots to eiect its extinction. We have found that in are extinguishing structures of the foregoing type. there is a tendency, especially during the use of high magnetic ilelds and at high currents. for the terminal ends of the arc to loop upward and, at times, to go over the exhaust end of the arc chute. The result is a flashovef at the exhaust end of the plate assembly. Furthermore, the

pressure created in the vents adjacent the arcing horns, by such looping of the terminal ends of under conditions of high interrupting duty. One object of our invention is to provide a construction which will prevent the aforesaid looping of the terminal ends of the arc and, consequently, will minimize the pressure formed.

Another object is to provide 9, plate construction in an arc extinguishing device which will facilitate cooling of the arc gases to prevent ilashover over the exhaust end of the arc chute.

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

Figure 1 is a vertical sectional view of a circuit interrupter embodying our invention and shown in the closed circuit position,

Fig. 2 is a plan view in section, taken substantially on the line II--lI of Fig. l,

Fig. 3 is a vertical sectional view, taken on the 4 une 111-111 of Fig. 1,

Figp4 is another vertical sectional view, taken on the line IV-IV of Fig. 1,

Fig. 5 is an elevational view of a. modified type plate which may be used in the arc chute of Fig- 1.

Fig. 6 is a vertical sectional view, taken on the line VI-VI of Fig. 5,

Fig. 7 is a portion of Fig. 6, enlarged to show more clearly the conilguration of the surface grooves,

Fig. 8 is a fragmentary view, taken on the line VIII-VIII of Fig. 5, and enlarged to show more clearly the shape of the surface grooves,

the arc, may cause breakage of the end plates Fig. 9 is a fragmentary view of a modiiled type arc chute, formed of a plurality of plates of the type shown in Figs. 5 and 6,

Fig. 10 is a top plan view of the arc chute shown in Fig. 11,

Fig. ll is an elevational view, partially in section, taken substantially on the line XI-XI of Fig. 10 of a modified type arc chute,

Fig. 12 is a vertical sectional view, .taken on the line XII-XII of Fig. 10,

Fig. 13 is a. fragmentary elevational view of one of the insulating walls of Figs. 10 and 11.

Referring to the drawings, and more particularly to Fig. 1, the reference numeral I generally designates suitable contact structure which, when separated to the open circuit position, establishes an arc which is moved upwardly into an arc chute, generally designated the reference numeral 2, as a result or a transverse magnetic neld set up by the blowout coil 3 and associated magnet structure 4. A rotatable contact arm 5 carries a conducting bridge Ii which, in the closed circuit position, as shown in Fig. 1, interconnects stationary main contacts T, I.

A contact stud 9 carries the current from the stationary main contact l, through an insulating bushing I to the external circuit. The contact stud for the stationary main contact 8 is not shown but it may be identical .to the contact stud S. K

Consequently, in. the closed circuit position of the interrupter, as shown in Fig. l, .the electrical circuit comprises the contact stud 9, stationary main contact l, conducting bridge S, stationary main contact 8, to .the contact stud therefor, not shown, to the external circuit.

During the opening operation of the interrupter, the contact arm E is rotated in a clockwise direction about a pivot point, not shown, but which is in electrical contact with the stationary main contact 8, to draw an are between the arcing contacts il. i2 after the separation of conducting bridge E from main contacts l, 8.

When the arcing contacts il, I2 separate, the arc formed therebetween wll expand upwardly because of the loop circuit so that one terminal thereof will be transferred to the are terminal member I8, and the other arc terminal will be transferred to the arc terminal member I9. When this occurs the blowout coil 3 will be put into series circuit and the transverse magnetic eld set up thereby between the field pole members Ilwill move the established are laterally along the arc terminal members I8, I9 into the arc chute 2. The electrical circuit now comprises contact stud 9, conductor 20, blowout coil 3, contact clip I5, arc terminal member I8, the arc itself, arc terminal member i9, flexible shunt 28, contact arm to the other contact stud not shown.

The arc chute 2 comprises an insulating rectangular-shaped housing member 22 positioned adjacent to an insulating plate 2l, .the latter serving as a base for the blowout coll 3. Within the housing 22 is placed a plate 2l composed of an insulating material such as asbestos. Two insulating spacer strips 25 (refer to Fig. 3) space a plate 26 composed of an insulating material away from the plate 24. 'I'he plate 2B may have a plurality of apertures 2l formed therein which facilitate the venting of'arc gases therethrough, particularly when high currents are .to be interrupted. Two more insulating spacer strips 25 space the plate 2t from a plurality of plates or a group of insulating plate portions 2l, forming a unitary plate and which are composed preferably of a refractory insulating ma- 4 terial which does not give ofi gas when contacting an arc. The plate portions or plates 29 are separated by insulating strips 30 which provide venting passages 35 therebetween.

Above the arc terminal member I9 is a second refractory plate 26, which is spaced by two spacer strips 25 from the right-hand plate 29 of the plate assembly. Two additional spacer strips 2b space the plate 26 from a refractory plate 3 I. Between the plate 3l and the housing member 22 are disposed a plurality of strips of iish paper 32. Bolts 33 secure the several strips 25. plate 26 and the housing 22 to the plate 2 I. Bolts 34 secure the right-hand plate 26 and its spacer strips 25 and iish paper strips 32 to the housing 22.

Each of the refractory insulating plates 29 has a slot 36 formed therein which has its upper closed end 3l positioned slightly off-center. The plates 29 are alternately positioned so that the upper ends 3l of the slots 36 form a slightly staggered construction. This staggered construction is disclosed in the aforesaid Patent 2,243,039 and causes a more rapid rise in the arc voltage which in turn causes the arc which has moved to the end of the slots 36 to momentarily be extinguished and restrike at a lowei point along the narrow portion of the slot. Thus an oscillating effect is obtained which materially decreases the burning eilect of the arc along the narrow portion of the slot. When the several plates 29 are assembled, the slots 38 form a V-shaped are passage or opening through the group of plate portions for receiving an are. This opening or arc passage is genera y designated the reference numeral 38 and extends between the arc terminal members i8, I9. The arc is laterally forced by the magnetic ileld into the opening or arc passage 38 to effect its extinction.

The plates 29 and the spacer strips 30 are cemented together in a preliminary process to form a unitary plate assembly which may be bodily placed into the rectangular housing 22. Insulating holding strips 3S are secured by bolts 4D to the opposed inner sides of the housing 22 to preI vent the unitary assembly of plates 29 from being forced upwardly out of the housing 22 by the pressure of gas formed during the interrupting operation.

The opening operation of the interrupter will now be explained. Upon the clockwise rotation of the contact arm 5, an arc is drawn between the arclng contacts II, I2, which quickly transfers, because of the loop circuit, to the arc terminal members I8, IB to thereby connect into series circuit the blowout coil 3. The magnetic iield set up by the blowout coil 3 between the field pole members I4 forces the arc upwardly along the arc terminal members I8, I9 into the slots 36 of the plates 29. The magnetic ileld forces ions upwardly out of the arc stream and through the vents 35 formed between the plates 29 by the strips 30. This raises the arc voltage and necessitates a further ionization of air to maintain the arc. At the iirst current zero, the dielectric strength of the arc stream space is sulllciently raised to prevent a restriking of the extinguished arc when the recovery voltage transient builds up across the arc terminal members I8, I8. 'I'he electrical circuit through the interruptor is consequently opened. y

In previous designs involving a plate structure of the foregoing type, wide vents were provided adjacent thel arc terminal members I8, I9 to facilitate the escape of the arc gases. It has been found that the use of increased magnetic exhaust end of the arc chute.

llelds above the value previously employed helps interruption and permits a reduction oi' size of the breaker since more volts per inch may be interrupted, but that this creates a condition whereby the terminal ends of the arc would loop upwardly in the wide vents provided adjacent the arc terminal members. Under heavy interrupting conditions the t-wo loops formed at the two arc terminal members I8, I9 tended to go upwardly clear out of the top of the arc chute and the result would =be a ashover over the exhaust end of the plate assembly. Furthermore. the pressure created in the end vents adjacent the two arc terminal members I8, I9 Fby the two are loops occasionally broke the end plates in the ceramic chute assembly.

To overcome this condition, we have discovered that the use of a short plate 26 of insulating arc-resisting material such as asbestos disposed above the arc horns or arc terminal members Il, I9 prevents looping of the terminal ends of the arc. However, suillcient vent space is provided on either side of the short plates 26 to facilitate removal of the arc gases upwardly out of the arc chute. To further help in the venting of the arc gases apertures 21 may be provided in the short plates 26. The use of these plates 26 entirely eliminates the flashing occasionally observed during heavy interrupting conditions. Furthermore, when the plates 26 were employed on interrupters of previous design together with increased field strength, there resulted an increase in rating of the interrupters oi.' approximately 50%. The result of the use of our invention permits thorough venting but prevents looping of the terminal ends of the arc.

We have discovered that for interrupting large amperage currents, such as 40,000 amps., the spacing between thel arc horn I8 and the rst plate 29 of the unitary plate assembly should be near 1/4 inch. For interrupting lower values of currents, such as 20,000 amps., the spacing should be substantially 1,/8 inch. For greater spacing than 1,41 inch there tends to be some looping of the arc at the arc terminal member I8. It is to be observed that the plate 26 is practically of the same thickness and lies in the same vertical plane as the arc terminal plate I8. Since the insulating plate 26 is in substantially the same vertical plane as the arc terminal member I8, it is apparent that we have provided venting means or vent passages on two sides of the arc terminal member I8.

A problem in the construction of air type magnetic circuit breakers is flashover over the As designs are made more compact, and voltage ratings are increased, the problem becomes more paramount. Flashovers result when the ion density of the exhaust gases out of the exhaust end of the arc chute is sufilciently high that a breakdown occurs and an arc is established. Deionization can be accomplished in several ways, among them being to increase the turbulence of the gases in their passage from the top of the slots 31 to the top of the arc chute. We have found that turbulence may be increased by using a modified type of refractory insulating plate 42 having surface irregularities or grooves 43, and which is shown more clearly in Figs. 5-8 of the drawings. It will be observed that the modified type of plate 42 is identical to the plate 29 previously described with the exception that a plurality of horizontally disposed surface irregularities or grooves 43 are provided. When the unitary plate assembly ls composed of the modified type of plates 42 instead of the plates 29, the result ls an arc chute construction partially shown in Fig. 9. f It will be noted that in such a modified arc chute construction the upward passage of the arc gases between the plates 42 encounters great turbulence as the gases pass over the surface irregularities or grooves 43. 'I'he gases are forced to change their direction a number of times. Each time a change of direction takes place, high turbulence will result, producing deionization by recombination and, at the same time, exposing more of the hot gases to the relatively cool surfaces of the plates and causing the loss of additional ions.

Figs. 10-13 show a modified type of arc chute construction which comprises a rectangular lnsulating enclosure 45, in which are inserted two cooperating insulating walls 46, 41 having cooperating interleaving ns 48 integrally formed therewith. The wall 46 has an end portion 49 integrally formed therewith through which extends bolts 50 which cooperate with spacer washers 5I to hold in position the arc terminal member I9. The wall 46 has a slot 52 formed therein (see Fig. 13) which cooperates with a slot 53 formed in the wall 41 to hold in position a short refractory plate 54 which has the same function as the plate 26 in the interrupter shown in Fig. l of the drawings.

The wall 41 also has an end portion 55 integrally formed therewith, which has bolts 50 passing therethrough to support the other arc y terminal member I8 in position. Again a slot 52 formed in the wall 41 cooperates with a slot 53 formed in the wall 46 to hold in position a second refractory insulating plate 54 which cooperates with the arc terminal member I8 in a manner as described above in connection with the interrupter shown in Fig. l.

The interleavingY fins 48 have horizontally disposed surface irregularities or grooves 43. When the two walls 46, 41 are inserted into the enclosure 45 holding strips 39 are secured by bolts 40 to the enclosure 45l to prevent the arc gases from forcing the cooperating walls 46, 41 uplwardly out of the enclosure 45.

The arc which is established between the are terminal members I8, I9 is moved upwardly by the transverse magnetic eld and is elongated between the interleaving fins 48 which form a zig-zag arc passage having a V-shaped entrance portion. As the arc current approaches zero, the progressive elongation of the arc, coupled with the cooling thereof, as it is forced against the interleaving fins 48, all contribute to effect its extinction at a current zero, the surface grooves 43 cooling the heated arc gases and preventing a ilashover over the exhaust end of the are chute.

From the above description, it is apparent that we have provided an improved circuit interrupter which prevents the terminal ends of the arc from looping upwardly out of the arc chute. We have disclosed improved spacing dimensions between adjacent plates which are especially eifective to cause rapid interruption when utilized in conjunction with relatively high magnetic ileld strength. Such a construction not only materially increases the rating of the interrupter but permits a reduction in external dimensions thereof. We have furthermore disclosed improved plate constructions to facilitate the cooling and deionization of the arc gases, and have shown how such a construction may be em- 7l ployed on an arc chute of the interleaving iin type.

Although we have shown and described specific structures, it is to be clearly understood that the same were merely for the Duri-08e 0f illlustration and that changes and modifications may readily be made by those skilled in the art without departing from the spirit and scope of the appended claims,

We claim as our invention:

1. In a circuit interrupter, an arclngI plate,v

means holding the arcing plate in position so that the front and back faces are freely vented, a plurality of slotted spaced insulating plates disposed adjacent one face of the arcing plate so as when aligned to form a substantially V-shaped arc passage, means for establishing an arc and for moving it into the Vshaped arc passage fwith one terminal end thereof moving along the arcing plate, and an insulating plate of substantially the same thickness as the arcing plate and disposed in the same vertical plane as the arcing plate with venting spaces on both sides thereof, the insulating plate being positioned adjacent the upper end of the arcing plate to prevent looping of the terminal end of the arc.

2. In a circuit interrupter, an arcing plate, means holding the arcing plate in position so that the front and back faces are freely vented, a plurality of slotted spaced insulating plates disposed adjacent one face of the arcing plate so as when aligned to form a substantially V- shaped are passage, means for establishing an arc and for moving it into the V-shaped are passage with one terminal end thereof moving along the areing plate, and an insulating plate of substantially the same thickness as the arcing plate and disposed in the same vertical plane as the arcing plate, the insulating plate being positioned adjacent the upper end of the arcing plate to prevent looping of the terminal end of the are, the insulating plate having holes provided therein to facilitate free venting of the arc gases.

3. In a circuit interrupter of the 'air break type, contact means for establishing an arc, an arc chute structure for extinguishing the arc, an are terminal member disposed within the arc chute, means defining venting passages on at least two sides of the arc terminal member per mitting direct commmunication of the hot arc gases from the region adjacent the contact means past the arc terminal member and out of the arc chute structure, plate means at least partly of insulating material disposedA adjacent the arc chute end of the arc terminal member to prevent looping of the terminal end of the arc, means positioning the plate means in substantially the same vertical plane as the arc terminal member so that the aforesaid venting passages may freely extend past the plate means, plate structure positioned within the arc chute including one or more slotted plates of insulating material, means positioning the one r more plates in planes substantially parallel to the plane of the arc terminal member, and the arc moving into the slot of the one or more plates as the terminal end thereof moves along the arc terminal member.

4. In a circuit interrupter of the air break type, a pair of separable contacts for establishing an arc, an arc chute structure including a plurality of spacedslotted plates of insulating material, the slots of the several plates aligning to form a. V-shaped arc passage into which the arc may be moved to eifect its extinction, an are terminal plate. means spacing the arc terminal plate fromoneendofthearechutetoprovldeapair oi'ventingesonopposite sidesofthe arc terminal plate to allow direct e of the hot arc gases from the contacts past the are terminal plate and out of the arc chute structure, means positioning the slotted plate nearest the are terminal plate less thanv one-fourth inch away therefrom, an insulating plate disposed adjacent the arc chute end of the arc terminal plate to prevent looping of the terminal end of the arc, and means positioning the last-mentioned insulating plate in the same vertical plane as the arc terminal plate so that the aforesaid venting passages may freely extend past the last-mentioned plate.

5. In a circuit interrupter of the air break type, a pair of separable contacts for establishing an arc, an arc chute structure including a plurality of spaced slotted plates of insulating material, the slots of the several plates aligning to form a V-shaped are passage into which the arc may be moved to effect its extinction, an arc terminal plate, means spacing the arc terminal plate from one end of the arc chute to provide a pair of venting passages on opposite sides of the arc terminal plate to allow direct passage of the hot arc gases from the contacts past the arc terminal plate and out of the arc chute structure, means positioning the slotted plate nearest the arc terminal plate less than one-eighth inch away therefrom, an insulatingv plate disposed adjacent the arc chute end of the arc terminal plate to prevent looping of the terminal end of the arc, and means positioning the last-mentioned insulating plate in the same vertical plane as the arc terminal plate so that the aforesaid venting passages may freely extend past the last-mentioned plate.

6. In a circuit interrupter of the air break type. an arcing terminal plate, means holding the arclng terminal plate in position so that the front and back faces are freely vented, a plurality .of insulating members disposed adjacent the arcing terminal plate and comprising a pair of cooperating walls having interleaving ilns extending therefrom, the walls when assembled forming a zig-zag arc passage having a V-shaped entrance portion, means for establishing an arc and for moving it into the V-shaped portion of the arc passage with one terminal end thereof moving along the arcing terminal plate, an insulating plate of substantially the same thickness as the arcing terminal plate and disposed in the same vertical plane as the arcing terminal plate with venting spaces on both sides thereof, and the insulating plate being positioned adjacent the up.. per end of the arcing terminal plate to prevent looping of the terminal end of the arc.

7. In a circuit interrupter of the air break type, a pair of cooperating walls having interleaving fins formed thereon, the walls when assembled forming a zig-zag arc passage, an arcing terminal plate, means holding the arcing terminal plate in position so that the front and back faces are freely vented, means for establishing an arc and for moving it into the arc passage with one terminal end thereof moving along the arcing terminal plate, an insulating plate of substantially the same thickness as the arcing terminal plate and disposed in the same vertical plane as the arcing terminal plate with venting spaces on both sides thereof, the insulating plate being positioned adjacent the upper end of the arcing terminal plate to prevent looping of the terminal end of the arc, and the insulating plate having aplurality or holes provided therein to facilitate.

ing therethrough for receiving an arc, means for` establishing an arc and moving it into said opening through the group of plate portions with the terminal ends thereof moving along the arc terminal members, means dening venting passages on at least two opposite sides of each arc terminal member, and a plate at least partly of insulating material disposed adjacent the outer end of each arc terminal member to prevent looping of the terminal ends of the arc, means positioning each plate in substantially the same plane as its respective arc terminal member so that the aforesaid venting passages on opposite sides of the arc terminal members may freely extend past the two opposite sides of said plates and out of the are chute structure.

9. In a circuit interrupter of the air break type, an arc chute including at least one arc terminal member disposed along one side thereof, a plurality of closely positioned insulating plate p0rtions disposed within the arc chute close to and in planes extending in the same general direction as the arc terminal member, means for establishing an arc and moving it against the plates with one terminal end thereof moving along the arc terminal member, means holding the arc terminal member in position so that venting passages are provided on the opposite sides of the 10 10. ,In a circuit interrupter oi the air break type, an arc chute structure including a pair of spaced arc terminal membersl positioned at the opposite sides thereof, means for establishng'anV are terminal member, and a plate at least partly 40 of insulating material disposed adjacent the outer end of the arc terminal member to prevent looping of the terminal end of the arc, means positioning the plate in substantially the same plane as the are terminal member so that the aforesaid venting passages on opposite sides of the arc terminal member may freely extend past the two opposite sides of the said plate and out of the arc chute.

arc between the arc terminal members and moving'the arc within the arc chute structure, aiplurality of closely spaced plate portions of insulating material positioned between the arc terminal members within the 'arc chute structure, said plurality of spaced plate portions being positioned transversely of the arc and having spaced edges extending transversely toward the arc and against which the arc is moved to eect the extinction thereof, said spaces between the plate portions permitting now of the hot gases therebetween from said edges against which the arc is moved to their opposite edges to exhaust out of the arc chute structure, and each of a plurality of the closely spaced plate portions having their faces which extend transversely to the arc Y provided with surface irregularities projecting substantially transversely to the direction of ow o1' the hot arc gases at a plurality of points' spaced along the flow paths between the plate portions to simultaneously increase the resistance of movement of the arc gases and provide turbulence between the plate portions to thereby cool and deionize the hot arc gases and reduce the Possibility of ashover at the exhaust end of the arc chute structure.

ROBERT C. DICKINSON. RUSSELL E. FRINK.

REFERENCES CITED The following references are of record in the ille of this patent:

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