US2654012A - Circuit interrupter - Google Patents

Description

SePt- 29, 1953 A. R. CELLERINI 2,654,012

CIRCUIT INTERRUPTER Filed April 8, 1950 .Albert R. Cellerini.

Patented Sept. 29, 1953 CIRCUIT IN TERRUPTER Albert R. Cellerini, Beaver, Pa., assig-nor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 8, 1950, Serial N 0. 154,813

8 Claims. l

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

The general object of my invention is to provide an improved spaced metallic plate type of arc chute, in which the established arc is more elfectively cooled and extinguished than has been obtained heretofore.

Another object is to provide an improved composite plate structure for a circuit interrupter of the spaced metallic plate type in which special provision is incorporated for the interruption of both low and high currents.

A further object is to provide an improved spaced metallic plate type of arc-extinguishing structure in which novel means are utilized to accelerate movement of the arc into the spaced plate structure and thereacross to become subdivided thereby.

A further object is to provide an improved magnetic structure for such a type of circuit interrupter in Which the transverse magnetic iield is intensified at the rear or exhaust end of the arc chute to facilitate the interruption of the higher magnitude currents.

Further objects and advantages Will readily become apparent upon reading the following specication, taken in conjunction with the drawing, in which:

Figure 1 is a side elevational view, partially in V vertical section, of an improved spaced plate type of circuit interrupter incorporating my invention, the contact structure being shown in the open circuit position;

Fig. 2 is a fragmentary side elevational view of the arc-extinguishing structure of Fig. 1, with the cover removed from the interrupter;

Figs. 3 and 4 are side elevational and end views of the plate used in the rear portion of the composite plate structure;

Figs. 5 and 6 are side elevational and end views of the plate used in the front or entering portion of the composite plate structure;

Figs. 7 and 8 are side elevational and end views of the gas-evolving barrier plate Iemployed in my improved arc chute;

Figs. 9 and 10 are side elevational and front elevational views of the improved magnetic structure for my improved arc-extinguishing structure; and

Fig. 11 is a fragmentary vertical sectional view of a modified type arc chute with the contact structure in the open circuit position.

Referring to the drawing, and more particularly to Fig. 1 thereof, the reference numeral I (Cl. 20D-147) generally designates a circuit interrupter including a molded cover 2 through an aperture of which extends an operating handle 3. The cover 2 rests upon a molded base 4 which may be mounted either horizontally or vertically as shown. The invention is applicable to either a single-pole circuit interrupter controlling one line of a circuit7 or to a multi-pole circuit interrupter controlling all of the lines of the circuit to be protected.

Briey, the circuit through a single pole of the interrupter includes a terminal stud 6, a nexible strap '1, which may be associated with a thermal tripping device, not shown, but which may be utilized to automatically actuate the operating mechanism upon the occurrence of overload conditions. The circuit then extends through a second flexible conducting strap 8 to a movable contact 9, the latter being actuated by a movable operating lever IU actuated in turn by any suitable mechanism, not shown. The mechanism is manually operated by operation of the externally projecting handle 3 in a manner well known to those skilled in the art.

In the closed-circuit position of the interrupter, not shown, the circuit extends from the movable contact 9 to a stationary contact I2, and thence through a strap conductor I3 to the other terminal stud I4 of the interrupter.

Associated with the movable and stationary contacts 9, I2 is an arc chute, generally designated by the reference numeral I6, and comprising a composite conducting plate structure I'I and a magnetic circuit I8. The composite conducting plate structure II includes a plurality of composite arcing plates I9 disposed in spaced relationship, as shown in Fig. 1, to receive the established arc 20 and to cause the subdivision and movement of the same.

Referring to Figs. 3-6, it will be observed that each composite plate I 9 includes a U-shaped front or entering magnetic arcing plate 2|, the coniiguration of which is more clearly shown in Figs. 5 and 6. The front plate 2I is made of any suitable magnetic material, such as iron, so that the magnetic eld surrounding the established arc 20 will be distorted and will cause the arc 2U to be attracted or biased in the direction 22 of Fig. 5 toward the bight portion 23 of the U-shaped plate 2l. The action of the iron plate 2l is particularly effective during low-current interruption.

'I'he composite plate I9 also includes a rear arcing plate 24, more clearly shown in Figs. 3 and 4. Preferably the rear plate 24 is made of ticularly described, its characteristics set forth,

and is claimed in my copending application ld February 16, 1950, Serial No. 144,46l, and asf signed to the assignee of the instant application.

It will be observed that s'el'ci'irecvrl,l` siichj as by'v spot welding, to the exhaust end of the rear plate 24 is another plate 25, which is also preferably formed of a nickel-chromium alloy similar to" the plate 24, the purpose for which wilvlsubsequently be explained. I provide a pair oflcerarnic plate holders 25, 26a, having grooves 21 provided tlierealong.' The composite' plates VI9 are' securely fastened into' position by being placed" within th'e'groves 2l, in a" manner morey clearly shown in Figs; 1'aid`2. It will be' observed that asliglit space 2B is present between the two plates 2|, N'of each composite platelg:

To" expeditek the movement of high current yarcs across' the" plate' structure Il, I provide th magneticcircuit VI8 more clearly shown in Figs. 9 and 10. clud'es a U'shaped. magnetic yoke member 29 having abaseportion a'nd outwardly extend'- ingleg portions 3|.

Preferably' the"distanceY D between the ex'- hausten'ds-of thelegs '3l is less than the distance f D1, which is the distance between theA iront edges 32'of the magnetic circuit" I8 so that the transverse magnetic eld 33* will be more cori'- Vcontracted atthe rear portionl or` the arc chute I6 because"v of the smaller air gap therebetween, as' indicated in'Fig. 2.

Disposed'at the re'arl end'of4 the arc' chute I6, as'shcwnin Figs." 1'and2; is a` perforated gas evolving barrier plate 35 having staggeredraper'- tur'es 36'providedftherethrough, the purpose for which" will:V be subsequently explained. Also a vsubstantially U'shap"ed" b'ent insulating plate member 31 isprovided aboutthe base portion 30 of the magnetic yoke 29v to prevent electrical contactA betweenA the yoke 29 andthe' stra-p conductor I3'.`

TheV operation of my improved arc chute. I will now be' explained. WhenV it isv desired to openthecontact structure, the handle 3 may be manually operated. Or ifv overload conditions a're'present, a suitable thermal or magnetic tripping device will be, actuated,l a's is` well known tov those skilled in the art, to actuate the operating mechanism (not'show'n) associated with the interrupter to cause separation of the movable contact 9 away from'the stationary contact I2 to establish an arc 20 therebetween.` Because of thel loop; circuit including the operatingfleverv I0, the movable contact 9 and the stationary contact I2, thegarc 20 will tend to expand, asI shown by the reference character 38.

During the interruption of low amperage cur-v rents, the magnetic or iron plates ZI will be par-f ticularly eiective to bias or force the yarc l3'8 toward' the bight portion 23 thereof, so that the arc 38 will become subdivided by the l plurality ci front plates 2l. Such subdivision' of the arc Y38 into a plurality of arcs 39', as shown in Fig.; 1, brings' about intensive cooling and deionivzation of the several short arcs 38' extending between Briefly the magnetic circuit I8"in" the front iron plates 2l. Under normal conditions such arcs will be rapidly extinguished, this all occurring during a time when the magnetic eld 33 is relatively weak due tothe small amount of current.

During the interruption of heavy currents, the single turn winding, as indicated by the current arrowsY 42`of 'Fig/.51, oftheV magnetic yolr 29 will create an intense transverse magneti'c'eld 33, particularly concentrated at the rear portion o'f the arc chute IB, as shown in Fig. 2. In such case y the high amperage arcs 39, having been previously subdivided by the iron plates 2 I, will continue their lateral movement into the rear plates `24` attracted thereinto by the intense magnetic field 33': Moreover, the presence of the plates 25j, which cause the spacing S to be less lthan'the spacing S1, the distance between th''iro'nt edges of the plates 24, will attract the heavy current arcs 4I to the rear end of the composite'plate'structure I9. Because of the greater mass of metal, and because of the intensive magnetic field, such lateral' movementv or` the'high current'arcs' 4I will be rapid. When'the` high current arcs'lll reach the outerends ofthe plates 25, they will cause the evolution'of gas from the gas-'evolving' plate 35; which gas willk tend to move the arcs 4I backward toward the front of the arc chute I6.' Interruption soon follows.

Because of the provision of thev vents-3B inthe barrier member Sli being *disposed*A in .staggered relation, as shown in Fig."7,v thev arcs lllwill'not pass out through the barrier 35'to' cause ilashover at'the exhauste'nd of the arc chute IIizQl From the foregoing descriptionitwill be apparentthat I have provided; an-improved arc chute inV combinationV with a` suitably designed 'and located magnetic coil to obtainamore eifecftive movement of the arc towards the back of theA arc chute I6'. The iront partV ofA the arc chute I6 is especially suitable for the interruption of smallcurrents, the magnetic eld being too weak at this time to be effective; vOn large currents, such asjshortcircuit` currents, however, 'the magnetic coil takes up the are at the throat of the arc chuter IG- and moves it back towards the rear of the arc chuteV I6; By having the rear part of the plates made ofY an arc-resisting-alloy such as nickel-chromium, the material is hence nonemagnetic and atthe same time a goodconductor. In this way the arc meets little; resistance in being split up into sma-ll arcs and forced towards the'back of the are chute I6. g t,

The magnet I8 is placed back farenoughin the arc chute- I6 from' the iron part of the platesjZI s o` that little or no magneticy iiux is shunted through the iron. In other words, the flux from the'magnet is located back far enough to bevback out of the iniuence of the iron part of the plates I9 so that all magnetic forces are effective in drawing the arc towardsv the back of the arc chute I6. It will furthermore be noted that the L21- shaped magnet' 29 by being slightly wider at the front end than at the rear end causes a" greater air gap at the front end with a corresponding narrower air gap at the rear end. y This tendsrto keep the magnetic flux towards the rear'of the arc chute IS and away from the'iron end ofthe arcing plates- I5. I'he presence of iron at the front end of the plates can be neutralized somewhatby the narrower air gap at the rear ofthe arc chute I. It is apparent that the coilene'rgizing the magnetic circuit I8 is formeelv by `the conductor I3 on the one side of the base portionl 30 of the magnetic circuit I8 and by the'arcrun- -ner 4U on the top of the base portion 30. When the arc has travelled to the rear of the arc chute I6, there will be, in effect, almost one complete turn about the core 30.

From the foregoing description it will be apparent that with my improved arc chute I 6, when the contacts part, the arc immediately comes under the drawing influence of the front or iron part of the plates. When it has travelled back far enough to come under the inuence of the magnetic eld of the magnet, it is drawn back by this eld towards the rear of the arc chute I6. In this way the arc is stretched to a greater length, thus increasing its resistance. It is cooled more eifectively by the sides of the plate holders 26, 26a and by the composite plates I9. it is deionized more effectively as it is forced to move back to the comparatively cooler part of the arc chute I 6. The wear on the plates I 9 is consequently diminished because the arc is in motion.

By having the rear gaps between the plates 24 slightly smaller than the front gaps between the plates 24, the arc, in seeking the easiest path, will travel to the rear of the arc chute I6 where this path is located. Thus, since the gaps are arranged so that the total sum of the gap spaces in the rear is a little less than the sum of the gap spaces at the front ends of the alloy plates 25:, the arc travels to the back of the plates 24 seeking the shortest path. Thus the lateral movement of the arc over the plates 24 is expedited.

My improved arc chute I6 has the following advantages:

1. There is more effective cooling because the arc travels to the rear of the arc chute and thereby comes into contact with the cooler parts of the plates.

2. Burning at one spot is minimized since the arc is in motion.

3. If the arc should hang on longer, it will be at the rear of the plates 24, 25 where damage to the plates 24, 25 will be less than if the arc played at the throat; this result is caused by the fact that the rear of the plate 24 is thicker than the front of said plate.

4. Deionization will be more rapid due to the more eiicient cooling of the arc, and consequently higher voltage ratings can be given to the interrupter.

5. There will be increased arc resistance as a result of more stretching of the arc and a compressing of the arc by the narrow rear end of the arc chute.

6. Low currents can be quenched by the front end of the are chute alone.

7. There is less deterioration of the plates because the arc is in motion most of the time.

8. The evolution of gas from the gas evolving barrier plate intensies the deionizing action brought to bear upon the arc.

Fig. 11 illustrates a modification of my invention utilizing a modified type arc chute generally designated by the reference character 43. The arc chute 43 includes a plurality of spaced metallic plates 44 which are preferably slotted, as were the plates 2I of Figs. 5 and 6. Again the stationary contact I2 and the movable contact S may be utilized to establish an arc 2U which enters the slots 45 of the several plates 44. If the plates 44 are formed of a nonmagnetic material, it is desirable to utilize a transverse magnetic eld to force the arc 20 into the plate structure to become subdivided thereby. However, if the plates 44 are formed of a magnetic material, such as iron, such transverse magnetic iield is not necessary, and the magnetic plates 44 themselves will suflice to attract the arc 20 into the slots 45 and onto the plates 44 to become subdivided thereby.

The important thing, however, is not the material of which the plates 44 are made, but the fact that the sum of the gap distances at the rear ends 46 of the plates 44 is less than the sum of the gap distances at the front entering edges 41 of the plates 44. The advantage accruing from the use of such a smaller gap distance at the rear ends 46 of the plates 44 has previously been set forth in connection with Fig. 1. Consequently, Fig. 11 merely shows how, instead of utilizing auxiliary plates 25, as in Figs. 3 and 4, one may use a plurality of single plates and have the plates slope in such a direction as to make the sum of the gap distances at the rear ends of the plates smaller than the sum of the gap distances at the arc entering ends of the plates.

Although I have shown and described speciiic 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. A circuit interrupter including means for establishing an arc, an arc chute including a plurality of spaced composite metallic plates, the arc entering portion of each composite plate Jeing U-shaped and formed of magnetic material, the rear portion of each composite plate being formed solely of' non-magnetic material, and means for forcing the established arc into the arc chute to become subdivided thereby into a plurality of serially connected arcs.

2. A circuit interrupter including means for establishing an arc, an arc chute including a plurality of spaced composite metallic plates, the arc entering portion of each composite plate being a slotted plate entirely formed of magnetic material, the rear portion of each composite plate being a plate formed solely of non-magnetic material, and means for setting up a substantially transverse magnetic eld across the arc chute especially intensied at the rear portion of the arc chute.

3. A circuit interrupter including means for establishing an arc, an arc chute including a plurality of spaced metallic plates, the established arc moving into the metallic plates to become subdivided thereby into a plurality of arcs, and the sum of the gap spaces at the rear ends of the metallic plates being less than the sum of the gap spaces at the arc-entering ends of the metallic plates.

4. A circuit interrupter including means for establishing an arc, an arc chute including a. plurality of spaced metallic arcing plates, the established are moving into engagement with the arcing plates to become subdivided thereby into a plurality of short are portions therebetween, and a plurality of relatively small additional metallic arcing plates secured to the rear portions of the iirst said arcing plates between the same so that the summation of the arcing distances at the rear of the first said arcing plates is less than the summation of the arcing distances at the arc-entering ends of the rst said arcing plates and the short arc portions will correspondingly be reduced in length as they move rearwardly across the first said arcing plates.

5. A circuit interrupter including means for iafeeioiie estatiiriiiig #an taie, fan termite iiieiudiiig @a lfpliiralityif'f vspaeeci-cii'iposite rinetani'eplates,`the Aare entering piftion 'fof leach composite plate --beixg "U-s'haped fand ifoiiriiedv of Vmagnetic "frna- `'aha7-ing a greater air vgap atthe frontend thereof ftlia'ni'at Ytheirear'end thereof for 'setting 11p-fa sbstantiallytransverse niagnetieeld across the Y*are ieh'ute -'espeeially intensified f'a't the 4'rear lp'or- .l-tionff the ivareTenute.

'6. A "cireuit "interrupter "including -means for :"istabli'shin'g Aan are, ein iarc eh'ute ineludingfa fpluralityof spacedcomposite-metallic plates, Vthe @arci-entering 'plate vportion of :eah composite 1 plate being 'formed' of magnetic material, 'anon- 'Ynagnetie---plateLportion 1positioned Ibeyond the rearmost portion 'of""eachl of aplurailty Vni the Smagnetic plates, whereby "the"-established Tare is ff's'bdivdedlinto' aplurality of'A serial1y=connected f7. oircuit Vinterrupter 4iriclndii'fig means `for establishing van are, fanffarc chute including a :'ipiurality o'f spaced-compositemetallic plates, the

arc-entering plate portion fof f each composite plate being U-shaped 'av'rid formed YlefInaIgriet-,ic ImateriaL a fnonlm'agnetic plate portion positioned beyond vtlfie-'rearmost portion of "eah of 'a"pluralty"f 'the magnetic plates, and"rneans lfor forcing theestablishediarc into the are chute and on to the non-magnetic plate portions -to iipl'ay ther'ebetweenas a-'plurality ofserially coni necte'diarcs.

'8.TA 'ereiiit in'terfruptr ineludin'g iiieans 'ffr establishing an are, an 4`arechiite linbluig 5a plurality of 'spaced compositernetalli'e plates, the arc-entering plate portion 'o'i ea'ch 4*eo'nip'site plate being formed'of vmagnetic material, a -non- Amagnetic plate por-tion positioned 'beyond the rearmost portion ofeach of a plurality of '-tlfie magnetic' plates, the `surfaces of both the magnetic plates and the non-'magnetic plates being exposed to areing, atleastv at the central portions thereof, to provide Afor movement `of terminals of 'short arcs thereon, whereby the 'established lare is `subdividedinto a plurality'of serially Conneted arcs Whose terminals move a'oross ytne lplates of bothtyp'nes.`

'ALBERT R. CELLERII.

References Cited in the Ifile'of this patent UNITED STATES VP'I'NIS Number Name Date 1,364,389 Lijndq'uist etal. Jan. 4, 519-21 1,896,763 Austin Feb. 7,11933 1,896,764 VBrai'naiti Feb. 7, 1938 1,919,438 Lindstrom Jui-y 25, 41933 2,147,419 Baker Feb. 14, 1939 2,268,336 AJackson et al Dec. 30, 1941 2,293,487 Bartlett Aug. v18,1942

FOREIGN PATENTS member Country Date

Images