US2604563A

US2604563A - Circuit breaker employing high and low intensity gas blast

Info

Publication number: US2604563A
Application number: US119372A
Authority: US
Inventors: Gustav E Jansson
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1949-10-03
Filing date: 1949-10-03
Publication date: 1952-07-22
Anticipated expiration: 1969-07-22

Description

July 22, 1952 JANSSON 2,604,563

CIRCUIT BREAKER EMPLOYING HIGH AND LOW INTENSITY GAS BLAST Filed Oct. 3, 1949 war/170212100115 W/WVAI/I/I/YA Patented July 22, 1952 CIRCUIT BREAKER EMPLOYING HIGH AND LOW' INTENSITY GAS BLAST Gustav, E. Jansson, North Quincy, Mass, assignor to Allis-Chalmers Manufacturing Company, -M ilwaukee, Wis, a corporation of Delaware Application- October 3, 1949, Serial No. 119,372

'6 Claims. '1,

This invention: relates to circuit interrupting devices and. more particularly to are extinguishing means for usein connec-tion therewith. Spe cifically thisinvention is. an improvement on the invention disclosed and claimed in George A. Burnhams application, Serial No. 126,572, filed November 19,1949; and Gustav E. Janssons application, Serial No. 119,373, filed October 3, 1949.

In the construction and operation of circuit intcrrupters, it is frequently necessary to provide means for extinguishing quickly the are which is drawn between separable arcing contacts. This are is usuallyblown by blowout means, such as an air blast, into an arc chute which is arranged to quench thearc .bylengthening it, cooling it, or-otherwise.

The interruptingcapacity of a circuit breaker interrupter in a high voltage circuit depends to a. great. extent on the circuit characteristics relating to the. rate of increase of recovery voltage when the current is interrupted. Although the breaker may be. successful in interrrupting the currentmomentarily, the. recovery voltage across the interrrupting gap, may rapidly rise to such a. value that arcing is reestablished before the breaker has sufficiently increased the dielectric strength of the gap. For interrupting higher currents under suchv conditions, it would be necessary toilmrease the pressure and the in.- tensity of the gas blast. If it is impractical to increase the gas pressure, the size of the blast passage or'the type of gas passage. or passages must be varied toprovide-for greater gas volume or reater.interruptingability. Such changes, however, usually result, in either a more expensive or larger breaker.

In accordance with the, invention claimed an arc, chute is provided adjacent a. pair of arcing contacts for receiving the arc atone end thereof and exhausting the arcing products at the other end thereof. The arcchute comprises a first blast passage for interrupting relatively. high currents and a second blast passage for interrupting relatively low currents. An insulating blast divider is arranged between the. source of fluid under pressure and the arc chute of the circuit breaker for distributing the blast from the point where it arrives in highly concentrated form to the arcingz' ones. This blast divider comprises a funnel-shaped portion'for receiving th blast o fl fro th v s r nd a pa r of passages or nozzles foredividing theblast into a high intensity stream which flows through the first blast passage for interrupting high currents and a low intensity stream which flows through the second biast passage for interrupting lower currents. I -he nozzle for directing the high, n e si y. s r m. i o h irst s a s e is asymmetrical at its intake portion and symmetrical at its outlet portion. The nozzle for directing the low i-ntensity streamintothe second blast passage may be asymmetrical throughout its entire length. 13y inserting a suitable resistor in the circuit by means of the arc in the first blast passage, the voltage recovery'rate of the current is decreased, and if the circuit isnot interrupted by the high, intensity blast, itmay be interrupted at a greatly decreased current at a much more favorable recovery rate by the cornparatively limited blast of the low intensity stream in the second; blast passage. In this manner, the interrupting capacity of the circuit breaker, for a given blast; pressure and gas consumption, is greatly increased.

It is, therefore, one object of the present invention to provide a new and improved arc interrupting device.

Another object of this invention is to provide a new and improved gas blast circuitinterrupter which divides a blast of gas into a high intensity stream and a low intensity stream, the high intensity stream flowing through a passage for interrupting a relatively high current and the low intensity stream flowing through a different passagefor interrupting a current of relatively low magnitude.

A further object of the invention is to provide a new and improved arc extinguishing device for interrupting a resistor-shunted are by means of a stream of gas and a predetermined time thereafter extinguishing a second arc in series with the shunting resistor by means of another stream of gas.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing in which Fig. 1 is a diagrammatic showing partly in cross section of a fluid blast circuit breaker em: bodying the presentinvention;

Fig. 2 is a view in cross section of the. embodimentillustrated Fig. 1 taken along the line II..II;

Fig. 3 is. a cross sectional view of the embodiment illustrated Fig.1 taken along the. line II a Fig. l is across sectionalview of Fig. 1 taken along theline IVIV.

The cross blast type air blast circuit breaker shown by way of example in Fig. 1 comprises relatively movable arcing contacts such as fixed contact structure I of the finger type and a pivoted blade-like contact 8. The fixed contact structure may comprise a plurality of current carrying contacts and an arcing contact as is well known, and is electrically connected to one line terminal 9 of the breaker. The blade-like movable contact is connected to the other line terminal I0. Although in general, circuit breakers of the type considered in Figs. 1, 2, 3 and 4 are provided with a plurality of similar pole structures, one for each phase of a polyphase electric circuit, only one such pole structure is shown in the drawing and the circuit breaker will be described in detail as if it were of the single pole unit type.

The movable contact 8 is suitably connected to an actuating mechanism (not shown) through a connecting rod II for operating the movable contact between closed and open circuit positions.

For the purpose of extinguishing the arc formed between the contacts when a power circuit connected thereto is opened, an insulating arc extinguishing structure I2 is arranged with respect to the contacts so that the arc is drawn at the entrance of the structure directly opposite a gas blast supply conduit I3. The conduit I3 is suitably connected through a blast valve (not shown) to a source of compressed gas, such as air, comprising for example a storage tank and compressor equipment (not shown).

The are extinguishing structure may, for example, define a double barrel arc chute I4 comprising a first blast passage I5 for interrupting relatively high currents and a second blast passage I6 arranged parallel with and spaced apart from passage I5 for interrupting relatively low currents. The blast passages l5 and I6 as illustrated in Fig. 3 have substantially uniform cross sections which may be rectangular or circular in form.

An insulating blast divider I9 is arranged between the gas supply conduit I3 and the arc chute I4 for distributing the blast from the point where it arrives in highly concentrated form by the narrow blast supply conduit l3 to an arc chamber provided for enclosing the are upon inception thereof. The are chamber comprises arcing zones and 2I which are spaced apart and situated at the upstream end of the double barrel arc chute I4. The blast divider comprises a funnel-shaped portion 22 mounted immediately adjacent the supply conduit I3 and a pair of

nozzles

23 and 24 which diverge from the diverging end of portion 22 toward chute passages I5 and I6.

The sides of the funnel-shaped portion 22 diverge at such a rate that the air expansion within the funnel is limited to the required minimum. The common axis 25 of supply conduit I3 and of funnel-shaped portion 22 of blast divider I9 is situated only slightly to the right of axis 26 of the first blast passage I5 of arc chute I4. Thus, the air blast reaching the downstream end of funnel-shaped portion 22 may pass into nozzle 23 with little restriction.

Nozzle 23 comprises an inlet portion 21 and an outlet portion 28. The inlet portion 21 may be asymmetrical and the outlet portion 28 symmetrical. Nozzle 23 may have a zone of minimum cross sectional area between the upstream and the downstream ends thereof and the walls 29 may converge more rapidly on the upstream end thereof than they diverge on the downstream end thereof, thus providing a well defined point of maximum fiow velocity where the rate of deionization of the arc path is high and the rate of fluid expansion downstream from the point of maximum flow velocity is controlled. Outlet portion 29 of nozzle 23 forms with the Wall of the first blast passage I5 a circular air pocket or gap 30.

Nozzle 24 comprises an inlet portion 3I and an outlet portion 32. As indicated in Fig. 3, the inlet and outlet portions 3| and 32, respectively, provide an oblong cross sectional area.

The width of nozzle 24 is constant throughout its length and is greater than the width of nozzle 23 at its narrowest point. Nozzle 24 provides a zone of minimum cross sectional area between the inlet and outlet ends thereof.

As illustrated in Figs. 1 and 4 the fixed contact structure I projects almost to the longitudinal axis of nozzle 23 and is therefore subjected to an intense air blast upon operation of the arc extinguishing structure.

The walls of the funnel-shaped portion 22 of the blast divider I9, as illustrated in Figs. 1, 2 and 4, define a diverging passage 35 therethrough which accommodates the movable sickleshaped blade contact 8. These walls closely surround contact 8 and control the escape of compressed air and are products through passage 35 into blast passages I5 and I5. Passage 35 is provided with a plurality of transversal grooves 36 which tend to establish eddies in the small flow of escaping air and are products through passage 35. These eddies, in turn, tend to minimize the rate of that fiow.

A pair of

probe electrodes

31 and 38 may be mounted within blast passages I5 and I6, respectively, for aiding arc extinguishment. Electrodes 31 as illustrated in Fig. 2 may comprise a rectangular portion 39 of refractory metal or alloy which is mounted to extend across the full width of the first blast passage I5 at the downstream end of outlet portion 28 of nozzle 23. A current limiting resistor 40 interconnects electrode 31 and the multiple finger contacts of the fixed contact structure I, thus lowering the value of the arc current at a predetermined time during arc extinguishment. Electrode 38 may comprise a rectangular portion H of refractory metal or alloy which is mounted to extend across the full width of the second blast passage IB at the downstream end of outlet portion 32 of nozzle 24.

The circuit breaker illustrated in the drawing is shown with the cooperating arcing contacts in the closed circuit position. An opening operation is initiated by admission of gas under pressure to supply conduit I3. The further flow of such gas through passage 35 of funnel-shaped portion 22 of blast divider I9 is at first impeded by contact 8, which obstructs the passage 35. Actuation of the connecting rod II moves blade contact 8 toward the right to open the electric circuit.

As the blade contact 8 is separated from the fixed contact I an arc is drawn across the arcing zone 20 leading to the first blast passage I5 and substantially concurrently therewith a path is opened for a blast of gas of high intensity through the supply conduit I3 and nozzle 23 of blast divider I9 to the first blast passage I5. This blast includes substantially all the gas being supplied through conduit I3, and drives or loops the are from zone 20 into passage I5. Frequently the arc is interrupted in the first blast passage y the blast. of asflowing through nozzle 2.3. As theiblade continues. to. move toward: the right, thearcis extended intozonezl if. it isnotalready extinguished. The-second blast passage It and nozzle, 24 of blast divider I9. are'uncovered. and part of the arc isdriven or. looped fromzone 2| into blast passage l 6 by, theblastirom'nozzle.24.

In accordance with the inventionclaimed a funnel-shaped portion 22 of blast divider 19 forms a blast duct, the side, walls of which diverge at a rate suchthat the air expansion within the blast. ductv isv limited to. a predetermined minimum value. The. blast therefore reaches thev arcing. zoneat. a hi h pressure, that has a strong tendency toovercome, the back pressure produced. by the; heat generated. by theparc. The common axis of conduit 13 and. funnelshaped portion. 22. of blast divider I9 is situated slightly. to the right of the axis of the, first. blast passage l50 f.arc chute, l;4.. This isconduciveto sucha distributionof the blast of air; that, most of it is caused to escape through. hefirst blast assage [5 which is situated immediately adiacent. the station ry fin r icontactsil while nly a m r p rtion of the blastis. caused o scape through the second blast passage 1 6 which is situated at a point remote from the stationary finger contacts 1.

This concentration of the blast in, the form of a high intensity stream on thestationary arcing contact structure 15 causes an intense deionization of the arc path at the point'where a. reignition is most likely to occur. The concentration of the blast upon arcing zone 20 and the first blast passage l5 causes a rapid rise of the resistance of the portionof thearc situated at the upstream end of the blast passage. I5, The are rises and comes incontact with probe electrode 31. The section of the'arc which is shunted by resistor 40 interconnecting the fixed finger contact structure I with the probe electrode 3'! arranged in the first blast'passagel5 wi1lbc rapidly extinguished and replaced after the first current zero by current through theresistor 40. From then on in the interrupting cycle, the task is limited to interrupting a resistor limited are current of lower intensity and this may be. achieved either at the upstream end of'blast. passage, l5. or at the upstream ends of'the first and second blast passages l5 and 16, respectively.

By providing rectangular shaped probe electrode portions 39 and 4| extending across the full width of blast passages l5 and I6 respectively, the arc when driven into passages 15 and I6 cannot bypass the

electrodes

31 and 38 without being engaged by them. Thus, the full arc extinguishing effect of the probe electrode is assured.

The intensity of the blast of gas necessary to interrupt a resistor limited current of low intensity is much lower than that necessary to interrupt a higher are current. Therefore, a blast of gas of relatively low intensity is provided through blast passage [6 for interrupting lower currents. The lower intensity of such blast results both from the division of the blast into two streams through

nozzles

23 and 24 and of the arrangement of nozzle 24 out of axial relation with supply conduit I3, whereby the momentum of the blast forces it to flow principally through nozzle 23. If the arc is not interrupted in blast passage 15 by the high intensity stream provided by nozzle 23 of blast divider 19 the resistor limited current is then interrupted in blast passage l6 by a, lower intensity blast of gas provided by nozzle 24.

Gap 30 formed by the outlet portion 28 of nozzle-1:3: and; the. upstream. portion. of: blast pas.- sage. li rormsa circular air pocketwhichis. not likely to be contaminated; by arc'products; and thus tends tojprecludeanelectrlc breakdown between .the first and second blast passagesv l5 and I6, respectively.

Although. but oneembodiment of' the present invention hasbeen illustrated and described, it will be apparent to those skilled in theart that various changes and modifications maybe; made therein'without departing-'iromthespirit of the invention or from the scope of the appended claims.

It isclaimed and desired 7 to secure by Letters Patent:

1 In. a fluid blast circuit interrupter, the combination comprising; a, source of, fluid under pressure, separable arcing contacts for establishing anarc, a conduit for conveying a blast of fluiidrrom said source adjacent saidcontacts for extinguishing the are drawn upon separation, of said contacts, an arc chute mounted adjacent said contacts-for receivingthe are at: one end thereof and; exhausting the arc; products at the other end. said are chutecomprisia first: blast passage and; a second: blastapassa and: a blast divider mounted betweensaid conduit and said arcchute comprlsinga first nozzle; having a circular cross sectional; area between the ends thereof for directing a: highintensity stream of fluid un er pressure: into. said firs blestr pa a for interrupting:relatively high currents anda second nozzle having: an oblong cross. sectional area bctweenwthe'ends thereof for directing a lower intensity stream of fluid under pressure into said second blast, passage for interrupting relatively; lowcurrents. I

2. In; a. fluid, blast: circuit interrupter, the; combination comprisingz; asource offluid under pressure, separablev arcing-contacts forestablishing a.n.arc,.a. conduit foraconveying-a blast of fluid from. saidsource-adjacent said contactsfor extinguishing the are drawn, upon separation of saidcontacts, an arc; chute mounted adjacent said" contacts for receiving the are at one end thereof-ianda exhausting the; are products at the other end, said: arc chute comprising a first blast passage. and a second: blast passage, and: a. blast divider mounted between. said conduit and said are chute comprising a first nozzle having a circular cross sectional area between the ends thereof for directing a high intensity stream of fluid under pressure into said first blast passage for interrupting relatively high currents and a second nozzle having an oblong cross sectional area between the ends thereof for directing a lower intensity stream of fluid under pressure into said second blast passage for interrupting relatively low currents, said cross sectional area of said second nozzle being substantially smaller than said cross sectional area of said first nozzle.

3. In a fluid blast circuit interrupter, the combination comprising: a source of fluid under pressure, separable arcing contacts for establishing an arc, a conduit for conveying a blast of fluid from said source adjacent said contacts for extinguishing the arc drawn upon separation of said contacts, an arc chute mounted adjacent said contacts for receiving the arc at one end thereof and exhausting the arc products at the other end, said are chute comprising a first blast passage and a second blast passage, and a blast divider mounted between said conduit and said are chute comprising a first nozzle having a circular cross sectional area between the ends thereof for directing a high intensity stream of fluid under pressure into said first blast passage for interrupting relatively high currents, and a second nozzle having an oblong cross sectional area between the ends thereof for directing a lower intensity stream of fluid under pressure into said second blast passage for interrupting relatively low currents, said second nozzle having a cross sectional area substantially smaller than said cross sectional area of said first nozzle and providing a zone of minimum cross sectional area between the ends thereof.

4. In a fluid blast circuitinterrupter, the combination comprising: a source of fluid under pressure, separable arcing contacts for establishing an arc, a conduit for conveying a blast of fluid from said source adjacent said contacts for extinguishing the are drawn upon separation of said contacts, an arc chute mounted adjacent said contacts for receiving the are at one end thereof, said are chute comprising a first blast passage for interrupting relatively high currents and a second blast passage for interrupting relatively low currents, and a blast divider mounted between said conduit and said are chute comprising a first nozzle having a fluid intake portion and a fluid outlet portion for directing a high intensity stream of fluid under pressure into said first blast passage for interrupting relatively high currents and a second nozzle for directing a lower intensity stream of fluid under pressure into said second blast passage for interrupting relatively low currents, said first nozzle being asymmetrical at its fluid intake portion and symmetrical at its fluid outlet portion.

5. In a fluid blast circuit interrupter, the combination comprising: a source of fluid under pressure, separable arcing contacts for establishing an are, a conduit for conveying a blast of fluid from said source adjacent said contacts for extinguishing the are drawn upon separation of said contacts, an arc chute mounted adjacent said contacts for receiving the are at one end thereof, said are chute comprising a first blast passage for interrupting relatively high currents and a 4 fluid outlet portion for directing a high intensity stream of fluid under pressure into said first blast passage for interrupting relatively high currents and a second nozzle for directing a lower intensity stream of fluid under pressure into said second blast passage for interrupting relatively low currents, said outlet portion of said first nozzle forming with said first blast passage a gap which prevents an electric breakdown between said first and second blast passages.

6. In a fluid blast circuit interrupter, the combination comprising: a source of fluid under pressure, separable arcing contacts for establishing an arc, a conduit for conveying a blast of fluid from said source adjacent said contacts for extinguishing the are drawn upon separation of said contacts, an arc chute mounted adjacent said contacts for receiving the are at one end thereof and exhausting the are products at the other end, said are chute comprising a first blast passage and a second blast passage, a pair of proble electrodes mounted one within each of said blast passages and each comprising a metallic portion extending across substantially the full width of said blast passages for engaging the arc, a current limiting resistor conductively connecting said probe electrode mounted within said first blast passage to one of said separable arcing contacts, and a blast divider mounted between said conduit and said arc chute comprising a first nozzle of circular cross section for directing a high intensity stream of fluid under pressure into said first blast passage for interrupting relatively high currents and a second nozzle of oblong cross section for directing a lower intensity stream of fluid under pressure into said second blast passage for interrupting relatively low currents.

GUSTAV E. JANSSON.

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

UNITED STATES PATENTS Number Name Date 2,290,004 Thommen July 14, 1942 2,290,708 Rankin July 21, 1942 2,306,240 Wyman Dec. 22, 1942 2,365,134 Amer et al Dec. 12, 1944