US2611058A - Circuit interrupter - Google Patents

Description

Sept. 16, 1952 H. L. RAwLlNs 2,611,058

' CIRCUIT INTERRUPTER Filed Aug. 12, 195o z SHEETS-SHEET 1 i NVENTOR Hererl, Paw/fm; deceased, by

2 SHEETS-SHEET 2 FiledfAug. 12, 1950 WITNESSES: www? Zd A? J Patented Sept. 16, 195:2

UNI-TED ATE'S PTINT OFFICE? CIRCUITTINTERRUPTER Herbert L.Rawlins,..deceased, late of Pittsburgh, Pa., bye harlotte.. M. Rawlins,v administratrix, Pittsburgh,',1?a;, assigner to Westinghouse Electric. CorporationEast Pittsburgh, `Ia.,- -a corporation 'of Pennsylvania v ApplicationAugust- 12, 195.0, Serial No.v.179,.0.6 6

i6 Claims.

This invention relates @to circuit interrupters in general, and more Ls'pecically. to arceextin.- guishing structures therefor.

A general object of the invention is to Vprovide an,V improved circuit interruptor having:=an.- im proved arc-extinguishing structure-which will more electively `interr upt' the acircuit.`v therethrough than hasv heretofore.v been fachieved.'

A more specicpobject is to provide. an improved circuit interruptor...particularlyronefof the air-break magnetic typeiinwhich a restriction is purposely. interposed between:-the -rcontact chamber and theiarcingn chamber-aso that -the interruptions will generally allfbeof one type, i. e., will take place atvabout the same point. in the current Wave.

Still a further Objectis to -irnprovethe spaced insulated plate typefof arc chute inanair-break magnetic circuit mterruptergbygutilizing a pair of cooperating plate vmembers,spaced laterally apart and affordinga restrictiongto theupw-ard movement of the arc'fromthe contact ychamber or region past thecooperatinggplatesfntoathe upper arc chute. chamber,. gyvherein arc Vextinction takes. place.

still anotherV object is to .prnvidexanl improved circuit interruptor. in whichthearois, momentarily held against. a.V normally. insulating# surface which has an inverse; :temperature-resistance characteristic. lIn other. words',-when such-:amaterial is heated bythe-arc:itsresistancei drops, and the result is the samersasL-havingga;resistance across the arc horns swhich;.damps thelhigh ,frequency transients present at interruption fto effect more ecient arc extinction.;l

Further objects and advantages .zwillzreadily become apparent upon. .--rea.ding y thev following specification, taken in conjunctiony with the drawings, in which:

Figure 1 is :a side elevational viewf,.'partiaflly in vertical section,- of nan fair-breakmagnetic Y More specifically, the contact structurefl includes a terminalstudlsurrounded by a flanged insulating.. bushng. 4, the latter extending through av support. plate-.5 and secured thereto. Atthe right-hand end of the'terminal stud 3 is secured a stationary maincontact 5 'having 1a pair of .outwardly extending metallic support plates'i secured. thereto. A rotatable' contact arm 8 is pivotallymountedat..9'.between the-support. plates, 1, andis Causedto .move thereabout 'by ythe .actuation of ,en insulatn'g ,Operating rod I2.

The operating rod l.2 is 'actuatedby Suitable mechanism,. not shown, butv which is responsive either to .manual operationlor to thev existence of overload .conditions 4existinggin thepcircuit controlled bythe interruptor..

The operating rod l2 is pivotally connected at i3 between. a. pair of support plates lrigidly secured to and rotatablewiththe vContact arm 8.

Alsomovable with the Contact arm Sisamain contact bridge l5 formed of conducting material andielectrically .interconnecting the stationary main contactt witha second ,stationarymain contactl'l.. The contact. .il .is secured` to the righthandend of a second. terminal.stud. l, which. is likewise enclosedwithina angedinsulating bushing i9., The bushing. vL9 is secured to and. supported by. the frameworkor supporting. plate structure 5.

Movablewith, the.' rotatable contact arm 3. is a pistoncylinder. 2f.within'.whichmoves apiston, not shown, secured .to .a piston-rod 2 i,` pivotally securedat 22 to the support plates l.

It will be apparent lthat upon v.clockwiseopening rotative motion-of -the. c,ontact.arrn 8 about the pivot point- 9, the Apistola. not showngqwill move upwardlyy wit-hin the pistonv cylinder T20 ,to force a blast-of compressedair out yof .the upper end-0f thepistonf-cylinder A2 0 and-through a. blast tube 23 adjacent the'.contact-structure. This vblast ofv air-5 facilitates .upward-movement-of `low current. arcsl into the interrupting chamber- Y2 the separation of the arcing contacts 25, 21.

movable secondary contact 2S separates from the relatively stationary secondary contact 24 after disengagement of the contact bridge I5 from the stationary main contacts 6, I'I. However, the secondary contacts 24, 26 separate prior to the Thus, the arc which is finally drawn by operation of the contact structure I is drawn between the arcing contacts 25, 21. y

Because of the loop circuit formed by the contact structure I including the horizontally disposed terminal studs 3, I8 and the moving arm 8, the arc which is finally drawn between the arcing contacts 25, 21 expands upwardly to thereby cause one portion of the drawn arc to engage the panel arcing horn or arc terminal member 35. The arc position at this point is indicated by the dotted line 32 with the movable arcing contact 21 being moved to the position shown in dot-dash lines in Fig'. 1. I y

There is provided suitable coil structure 33, including a pair of parallel disposed blowout coils 34. One end of the coils 34 is Vconnected to the socket stationary contact 35. The other end of the 'coils 34 is connected to the stationary main contact structure I1 by the strap connection 34a. Thus upon transfer of one terminal of the arc 32 to the arcing horn 3D, the coil structure 33 will be inserted into series circuit and will serve to energize the transverse magnetic field extending between the magnet pole shoes 35, 31. This transverse magnetic eld extending across the interrupting chamber 2 serves to cause upward movement of the arc, no w designated by the reference character 38, into the arc chute 39 inl cluding a plurality of spaced slotted ceramic plates 4U. Y

It will be noted that each pole shoe 36, 31 has depending downwardly therefrom and secured thereto, such as by welding, a sub-pole piece 42.

The use of such sub-pole pieces 42 facilitates the initial upward movement of the arc initially drawn between the contacts 25, 21. This follows inasmuch as when the arc is originally drawn between the arcing contacts 25, 21 there is formed a magnetic field about said arc. A portion of the magnetic field passes through thel sub-pole pieces 42 through the pole shoes' 36, 31 and through the core 43 enclosedl by the blowout coils 34. However, the magnetic iield below thev arc, as initially drawn between the arcing contacts 25, 21, must pass through the air space below the arc Yand since the magnetic eld is more ccncentrated below the arc than above it, the arc is rapidly moved upwardly to cause a portion of it to strike the arcing horn 30. Also the portion of the arc, designated by the reference numeral 44, is moved toward the left into the transfer interrupting stack generally designated by .the reference numeral 41. It will be noted that the transfer interrupting stack 41 includes a plurality of spaced slotted ceramic plates 43 having slots 49 provided therein.

A transfer arc horn 54V is made of metallic material. Below the arcing horn 54 and secured thereto by rivets are a plurality of plates formed Y of magnetic material, such as steel. In this instance, there are four such magnetic plates, two of which are designated by the reference character 59 and two of which are designated by the reference character 59. The presence of the four plates 59,50 of magnetic material disposed immediately below thetransfer arc horn 54 facilitates the leftward movement of the lower end of 4 the arc from the stationary arcing contact 25 to the arc horn 54 and also facilitates the entering motion of the arc portion 44 of the arc 32 into the transfer interrupting device 41. The position of the arc portion 44 may now be designated 44a.

High field strengths have been found necessary for high interrupting capacity within a small space. All of the iiux across the interrupting chamber 2 between the pole shoes 35, 31 must thread the magnetic coils 34. rhis means that the reactance of the magnetic coils 34 is high, and a countervoltage of several hundred volts will appear across the terminals of the magnetic Vcoils 34 when the short circuit current is attempted to be transferred to the coils 34, which are in parallel, and which are connected electrically between the arc horn 39 and the upper terminal stud I3.

This makes the transfer interrupter 41 necessary to interruptA the arc portion 44a extending between the transfer'arc horn 54 land thearc horn 30.

The use of a transfer interrupting device 41 to facilitate insertion into series circuit of the blowout coils 34 is more fully set forth and claimedin U. S. patent application filed January 4, 1947, Serial No. '720,165 by Robert C. Dickinson and Russell E. Frink and assigned to the assignee of the instant application.` This application also sets forth'and claims the use of the sub-pole pieces 42 to facilitate the initial upward movement of the arc as initially drawn between the arcing contacts 25, 21.

After the transfer interrupting device 41 has interrupted the arc portion 44a. and caused the arc to extend between the arc horn 3D and the movable arcing contact 21, the parallel disposed blowout coils 34 are in series circuit, and energize the transverse magnetic eld extending across the interrupting chamber 2 through the pole shoes 36, 31. The right-hand end of the arc 32 soon transfers to the right-hand arc horn or arc terminalmember 62, which is connected by a conducting strap 63 to the lower terminal stud 3i'ef1the-interrupter. Thus the reference character 38 indicates the position of the arcextending between the arc horns 3G, 62 after the blowout coils 34 are in series circuit.` Y

The arc 3.3 is moved upwardly within the arc chute 39, which, as mentioned previously, includes a plurality of spaced insulating ceramic plates 4U. Fig. 3 more clearly shows the configuration of the plates 40.

It will be noted that each'plate 49 has a slot 64 A provided therein, the upper closed end of which is slightly unsymmetrical about the center line of the plate 49. Thus the alternate positioning Y and produce-an actual' blast of gas perpendicular to the are, which action requires the arc to ionize fresh quantities of gas in considerable quantities. When current zero' is reached, this action iscontinued to effectively deionize the arc and establish dielectric in the arcchute 39. The theory of the interrupting i operation is more clearly set forth in U. S. 'Patent-2,442,199, issued 'May 25,

ammess- 1943;v to Robert C. DickinsonandRusselrE-,fllrink andassigned;` to the yassignee ofthe-instant application. Certain features of'f'the' Aforegoing arc chuteare describedand claimed inUnited States patent` application filed :January fi, 1947,V Serial No. i 720,166; byf' Herbert fRawlin's; Robert Dickinson, .-andRussell E. Vliirinkfand` assigned to the yassignee Vor ,the instant" application.

This `invention' is particularly concerned' with an improved method 'sof arcrcontrol for high'voltage'air'circuit breakers of -themagnetic-blowout type. Improvement-in operation of circuit-breakers of this type could be'obtained if it were practicall to make the are alwaysY enter; the are chute 39 or arcl passage 66 iat the Asame time wither-e vspeci: to 'currentzero VYVari-'ous schemes havebeen devised 'to ytimethe-openingpr the contacts to "accomplish this, but `they havebeen tcofcomplijcated to be commercially practical. It isl readilyapparent, moreover, that the problem vis' rendered more Y difficult' in ya .three-pole..` single mechanism breaker; In" such" 'a breaker. the' contacts open at the'same time,'but the value 'of the-instantaneous 'current'is different in .each of thethree poles. 'Ihusgcurrentl zeros falll at different times zin the three. phases.

A structure vhas been vdevised which rvaccomplishes timing of the? entrance of the arc"38into the arc-- chute 391er arcpassage 1,66 "independently off'the time ofy contact parting. As'willbe apparent-:from theiollowing description, thev device is simpleand. adds little' 'totheV cost ofthe interrupter. Furthermore, tests show that the desired resultsI are accomplished. IThis permitsjthe ilel'dstrength, `slot shape,v etc., to be coordinated in such a manner Vthat the; interrupter willwork best onthe'one type, of interruption that will result. Otherwise,z it is necessary to produce a compromise Adesign which will handleV many types of interruption and, therefore, is less eiicent.

Referring..particularly,to Fig.' 2, it will be observed that there are .provided a pair. of convergingrefractory arc shields 61, 68. `A pair of horizontally disposed rectangular pieces 69,' 1U of refractory insulating materialVpreferably ceramic, are placed between the arc shields '61, 68 and the arcchute-SS. Consequently','there=is Aformed a narrow, slot-like opening or aperture,l designated by the reference characterlZyandfdividing the arc chute into a lower contactchamber or region 1,4 and-an upper arc chutelchamberor arcing chamberf.. Fig.V 2 approximately shows the critical proportions utilized in 'a test sample.' The slot 12 was 1%; inch wide, and the distance S was 111g inch.

Circuit interruption with the foregoing device takes place as follows. The arc, which is drawn between the arcing contacts 25, 21, transfers to the arc horns 30, 62 in the manner previously described, energizing the magnetic structure 33. The transverse magnetic field, extending between the pole shoes 36, 31, forces the arc 38 into the upper part of the lower chamber 14 against the refractory pieces 69, 10. The narrow slot-like aperture 12 between the pieces 69, 10 permits only a fraction of the ionized gas to pass into the relatively cool upper chamber 66 where the deionization is suiiicient to keep the ion density below that in the lower chamber 14 as long as the current in the arc stream 3B is high. When current zero is approached, the ionization of fresh quantities of gas in the lower chamber 14 practically ceases, and the momentum of the gas upwardly through the aperture 12 into the upper chamber or arc passage 66 carries enough of the 6 resid-ualjionization uprthatl -whenf-t-hei currentreestablishes inthe opposite direction, ItheI-ioniza tion in theupperchamber- 66-is more intense than infthe 4lower-chamber 14; and the; arc-38` is re- `ignited in the upper 1 arcing chamber -`66.-

The magnetic eld nowL-carriesthe arc- 38 rapidly to thetops ofthe-slotsfGdf-whileit is still small; 'and themhigh -resistance -d-ue to 'restriction and; length `limits the f current passing through theare'streamy 38 -to Aa fraction goi the value it would reach without -theiinterruptein 1 -The1greatly reduced amperage and highpower factor-caused by this sequence of events makes interruption easyy-a-nd thisoccurs at ntheenext -currentfzero The-f spaced insulatingr plate i portions 40 are particularlyv effective, inf-conjunction withv 'the transverse V--magnetic "eldv -set up -lziy-the` -coi-1 structureL 33; tofeiectV theffextinction of' low: current` arcs. This is par-ticul'arly'important4 since, unlike previous l'structuresoff-'this type; the plate portions-461 arefonly ca-lledhfupon` to Vinterrupt relatively/low current arcs. Moreoveiyftheifreely- Vented-exhaust passages'dfprovid'ed between the several plates 40 bring A`particularlyA 'effective V'deionizingi conditions to bear upon the-lowcurrent arc-`38`-after it has passed-above-the restricting pieces 69,10 into thearc passage-66.

Thus, the combination -of `the slot TF2 andthe areV chute 3 9,- particularly` designed-rorlow current interruption, together with the: transverse magnetic- `-field, all' contributeto :result in av cir cuit interrupterv particularly effective ingepera-OD'.

Still another advantage #is vobtainedvwith the structure described.v 'lhel pieces'l69,v 10 placed acrossthe arc chute andheated-to -a highftemperature-byconfining the-arc-38 `in the lower chamber 14 vmay be -made to actas a resistor and-dampthe high frequency-transients present at interruption. However, an instant later, lafter theiarc -38- has moved above the'pieces 69, 10 and has been extinguished inthe arc chute .39, these pieces 69, 'I0 will-have -cooled suiciently to Apresentv practically infinite vresistance to the-cir cuit. Thusfmeans may be provided for momentarily holdinganarc against a normally insulating surface which has `an -inversetemperature characteristic (drops to `10,000 ohmsvat temperatures above-500 C.) andwhich is effectively connected acrossv the' terminals of rrthe 'breaker yduring interruption.

From the foregoing'description'oi themproved interruptingdeviceit willbeapparentthat there is provided improvedmeans for controlling the entrance time of high current arcs into an arc chute. In addition, it will be apparent that there is provided improved means for damping the high frequency transients present at interruption by utilizing a normally insulating piece of material connected across the terminals of the breaker having an inverse temperature-resistance characteristic. The normally insulating piece of material, whose resistance value drops at relatively high temperatures, brings about a situation in which a high resistance is connected between the terminals of the breaker at the time of interruption, thereby damping the high frequency transients present at the time of interruption. The theory of such transient effects, at the time of interruption, are set forth in detail in United States Patent 2,467,760 issued April 19, 1949, to Leon R. Ludwig, Benjamin P. Baker and Winthrop M. Leeds, and assigned to the assignee' of the instant application.

Although there is shown and described a 7 specific structure, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and niodications may readily ,be made therein by those skilled in the art, Without departing from the spirit and scope of the appended claims.

V `What is claimed as the invention is:

1., A circuitrinterrupter including means for establishing an arc, an arc chute for extinguishing the arc, restricting means disposed Within the arc chute dividing,r it into a contact chamber and an arc-extinguishing chamber, the restricting means causingthe arc to enter the arc-extinguishing chamber only near the current. Zero period, and the restricting means being composed of insulating material having an inverse temperature-resistance characteristic and effectively connected across the terminalsV of the interrupter to damp the high frequency transient voltageat the time of interruption.

2. A circuit interrupter including means for establishing kan arc, an arc chute for extinguishing the arc, insulating material bridging the terminals of the arc chute against which the arc is momentarily vforced, and the insulating material having an inverse temperature-resistance characteristic to damp the high frequency transient voltage at the time of interruption.

3. A circuit interrupter of the air-breakv type including means for establishing an arc, an aro chute for extinguishing the arc, restricting means disposed Within the arc chute dividing it into a contact chamber and an arc-extinguishing chamber, the arc-extinguishing chamber comprising a plurality of spaced insulating plate portions, means` for establishing a'transverse magnetic field for moving the arc against the insulating plate portions,` and the restricting means causing the'arc to enter the arc-extinguishing chamber only near the current zero period.

4. A circuit interruptor of the air-break type includingmeans for establishing an arc, an arc chute for extinguishingthe arc, restricting means disposed Withinthe arc chute,i dividing itV into a contact chamber` and. an arc-extinguishing chamber, the arc-extinguishing chamber comprising a pluralityof spacedinsulating plate` portions, means for establishing a transverse magnetic field for moving the arc against the insulatingI plate portions, the-restricting Vmeans causing the arc to enter the arc-extinguishing chamber only near the current zero period, and the restricting `means being composed of insulating material having an inverse temperature-revsistance characteristic and effectively connected .across theterminalsof the interrupter'to damp the high frequency transient voltage at the time of interruption; f f

5, A circuit interruptor of the air-break type including means for establishing an arc, an arc chute forI4 extinguishing the arc, a pair of cooperating elongated insulating members'closely spaced apart toaiTord a restriction dividing the arc chute into .a Contact chamber and an arcexting'uishing chamber, f the arc-extinguishing chamber comprising a plurality' of spaced insulating plate portionsvv having freely vented passages therebetweemmeans for establishing a transverse magnetic field across the arc-extinguishing chamber for moving the arc therein'against the insulating plate portions, and the closely spaced apartmembers ,permitting the arcVA to enter the arc-extinguishing chamberonly near the current zeroperiod.

6. A circuitinterrupter of the air-break type including meansffor establishing an arc, an arc chute for extinguishing the arc, a pair of cooperating elongated insulating.. members closely spaced apart to alford ay restriction dividing the arc chute into' a contact chamber and an arcextinguishing chamber, the arc-extinguishing chamber comprising a plurality of spaced insulatingY plate portions having freely vented passages therebetween, means for establishing a transverse magnetic eld across the arc-extinguishing chamber for moving the arc therein against the insulating plate portions, the closely spaced apart niembers'perrnitting the arc to enter the arcextinguishing chamber only near the current zero period, and the closely spaced apart members being of insulating material having an inverse temperature-resistance characteristic and eiectively connected across the terminals of the interrupter to' dampVV the highirequency transient voltage atjthetime of interruption.v

v if 'CHARLOTTE M. RAWLINS, Administratric of thefEstat'e of Herbert L.

Rawlins, Deceased.

REFERENCES oigan The following references are of record in the le of this patent: f

` UNITED STATES PATENTS l 2,442,199 Y Dickinson et al. May25, 1948

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