US2337949A

US2337949A - Circuit breaker

Info

Publication number: US2337949A
Application number: US444972A
Authority: US
Inventors: Ludwig S Walle
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-05-29
Filing date: 1942-05-29
Publication date: 1943-12-28
Anticipated expiration: 1960-12-28
Also published as: GB564050A

Description

Dec. 28, 1943. s. WALLE CIRCUIT BREAKER Filed May 29, 1942 uw ,m aww www@ 1m/m, .L9 b n M r Patented Dec. 28, 1943 Ludwig S. Walle, Lansdowne, Pa., assigner to General Electric Company, a corporation o! New York Application May 29, 1942, Serial No. 444,972

`A16 Claims. (Cl. 20o-'147) My invention relates to circuit breakers, more particularly to arc extinguishers for circuit breakers, and has for its object a simple, effective and low cost device for extinguishing an arc.

In carrying out lmy invention in one form, I form the arc extinguisher device mainly from a material which is an electrical insulator and which also has the characteristic of being a conduotor oi' magnetic flux. This material is preferably a basically inorganic one that can be molded in the desired form and may, for example, be formed of a mixture of iron oxide, asbestos powder and phosphoric acid, this mixture being molded by subjecting it to a high pressure and heat.

' This magnetic flux permeable material forms a path for the magnetic flux generated by the current in the arc and produces a more intense magnetic eld around the arc 4whereby`the arc is moved electromagnetioally into the device thereby to be lengthened, reduced in section, cooled and thereby extinguished. To further lengthen having a lower portion I6 extending at an acute angle toward the left so as to be just above the movable contact II when it moves to its open t circuit position. These two arc runners I4 and I5, as shown, diverge apart in an upward direction so that as the arc travels upward on these two members it is elongated. Preferably, the

the arc, the extinguisher device is formed to provide a plurality of substantially parallel walls which are substantially perpendicular to the arc.

,For a more complete understanding of my invention, reference should be had to the accompanying drawing in which Fig. 1- is a side eleva- -tion view, partly in section, of an arc extinguisher device embodying my invention; Fig. 2 is an end view of the device lshown in Fig. 1; Fig. 3 is a sectional view along the line 3--3 of Fig.' 1 looking in the direction of the arrows but showing a complete device; Fig. 4 is a sectional view along the line 4-4 of Fig. 1 looking in the direction of the arrows but showing a complete device; while Fig. 5 is a fragmentary view in section of a modied form of my invention,

Referring to the drawing, I have shown my invention in one form as applied to a stationarycontact I ll with which cooperates a movable contact II, the movable contact being commonly mounted on the end of an arm I2 which is mounted for pivotal movement so that the contact II is movable by manual or other means (not shownltoward the left, as seen in Fig. 1. about this pivot to an open circuit position. The contact I0 is mounted adjacent the lower end of a U-shaped member I3 made of electrically conducting material, the inner arm I4 of which forms a runner for movement of the arc upward, as

Y seen in Fig. 1.

Suitably spaced horizontally from the contact Ill is a second arc runner member I 5 made of.

electrically conducting material, such as copper,

contacts and arc extinguisher will be mounted in the upright position shown in Fig, l. A The arc extinguisher, as shown, is of the type described and claimed in Patent No. 2,306,204,

issued on December 22, 1942, to' Eugene W. Boehne. It is molded in the form of two plates or members I'I `and I8 which are positioned on opposite sides of the path of movement of said movable contact and are formed with complementary projections or ridges thereby to provide a plurality of substantially f parallel walls. As shown, the member I1 is provided with a plurality of equally spaced projections or ridges I9 which extend substantially vertically, as seen inv Fig. 1, and'which are narrower at their tops than attheir bases. Likewise, the member I8 is provided with a plurality of projections or ridges 20 which are identical in size and spacing with the projectionsl I9 but are complementary with the projections I9 so that the projections, when the two blocks are put togetheras seen in Fig. 3, are interleaved or set between each other alternately. Also, the members are so formed that the projections I9 and 20 are spaced apart, as seen in Fig. 3, so as to form a continuous narrow -slot 2I of substantially uniform width, as seen in Fig. 3, at the upper ends of the members Il and I8.

of substantially parallel spaced walls extending' y substantially at right angles to the path of movement of the movable contact I I.

.'Ihese projections I9 and 20 are tapered downward, i. e., become shallower, from the upper end downward, as shown in Fig. 4. As shown in this ngure, the tops of the projections or rightand left-hand edges are straight and meet with the lower substantially-ilat

inner walls

22 and 23 at

points

24 and 25 just above the arc runners I4 and I5. Between the bottoms of the projections are continuations upward ofthe

fiat surfaces

22 and 23. At the upper ends of the projections, however, the material between the projections is cutaway to form recesses 26 in each of the members I1 and' I8, these recesses providing for a greater height of the opposite projections at their upper ends.

Thus, it will be seen that as the movable contact II moves toward the left, the arc at first strikes `directly between the two contacts and is not interfered with by the projections I9'and 20. As the arc travels upward, however, it is forced to pass more and more between the projections whereby the arc is elongated and restricted in cross section. Thus, any portion of the arc that 4 exists at the top of the members I1 and I8 must take the very much elongated and restricted path of the slot 2l shown in Fig. 3.

For the purpose of producing an increased magnetic eld in the arc space between the plates for assisting electromagnetically the rapid movement of the arc upward into the elongated and restricted path provided by the slot 2|, I make the members I1 and I8 f1 om a homogeneous material having substantially uniform electrically insulatlng and magnetic characteristics throughout the ,members This material, while still electrically insulating, is magnetic to a pronounced extent. In other words, the members I1 and I8 have a relatively high permeability as compared with the permeability of air and other well known electrical insulators. I preferably make the members from a mixture of magnetic materia1 and electrically insulating material of the type described and claimed in applications Serial Nos. 423,518 and 507,016, led by Edwin H. Brink and Nicholas F. Arone on`December 18, 1941, and October 20, 1943, respectively, both assigned' to. the same assignee as this invention. Preferably I use a mixture by weight of 3 parts powdered iron oxidelFEaOi) and 1 part asbestos powder, with cubic centimeters of 75 per cent phosphoric acid (HPaOl) for each 100 grams of the mixture. These materials are thoroughly mixed together, heated to a temperature of 200 F., and subjected at that temperature to `a pressure of about 3,000 pounds per square inch in forming thegmembers or blocks I1 and I8. In a typical circuit breaker the permeability of the material of the blocks was found to be about seventy, i. e., seventy times the permeability of air. This circuit breaker interrupted successfully a current of over 10,000 amperes at 600 volts A.C.

Preferably, in the aforesaid mixture I use an asbestos powder consisting by weight of:

of the resistance ofthe material to a point that the chute and breakerare destroyed.

Preferably. after the arc chute members I1 and I8 have been molded and finished as to form, they are subjected to an,A additional baking operation for a` period of twelve hours at a temperature of 110 C. This baking operation imu proves the dielectric characteristics of the material of the arc chute members.

If desired to assure'a greater'uniformity in the pressure applied to the mixture, the blocks may be molded with more or less uniform rectangular cross sections and then` machined to provide the various grooves and projections.

In order to still further reduce the reluctanceof the magnetic flux path, I provide a pair of magnetic soft iron plates 21 and 28 on the outer sides of the plates I1 and I8 and on opposite sides of the Contact I0 and the arc runner arm I4. Also, I provide a pair of

magnetic iron plates

23 and 30 on the outside of the plates and on opposite sides of the arc runner I5. These plates 29 and 30, as shown, are preferably set in re cesses provided for them in the plates and have substantially their entire inner surfaces in engagement with the plates I1 and I 8.

The pair of plates 21 and 28 are electromagnetically joined togetherwat theirouter ends by a plate 3I of magnet iron'inser'ted between the outer ends of the plates'and in engagement with the plates so as to be in good magnetic flux conducting relation with them. This plate 3| extends across the outer ends of the blocks and itis separated from the arc runner I4 by a layer of suitable electrically insulating material 32. As shown in the drawing, the arc runners I4 and I5 have the same width, i. e., dimension as seen in Fig. 4, as the distance between the blocks at the points where the arc runners are secured.

lAlso, a bar 3Ia, made of magnet iron, lies in the `curve of the conductorl member I3 and joins magneticallytogether at thispoint the two plates Per cent MgO 33.30 SiO: 40.92 F6203 8.70' A1203 5.18 H2O 11.30

This asbestos. while containing 8.7% of iron oxide, does not, I have found, show any trace of magnetic attraction even when molded into an article.

The molded material manufactured as I have described, in a typical case, had for a. cubic centimeter sample, ohmic -resistances A.as follows: at 1,000 volts applied to opposite sides of the sample an infinite resistance; at 1,200 volts applied, 240,000 ohms resistance; 'at 1,500 volts applied. 80,000 ohms resistance. The composite material thus has a negative temperature coefficient, the leakage current through it heating the material and lowering its resistance. When the material is cooled to its original temperature, its original f insulation resistance values are restored.

A destructive or appreciable current through the material of the'arc chutev may therefore be defined as'a current of a value, such as in `eircess of 5 milliamperes` a square centimeter, which 21 and 2 8. It will be understood that the conductor I3 forms a half turn blow-out coil around the bar 3Ia for the generation of magnetic flux. g A second cross plate 33 made of magnet iron is provided for joining together the ends of the` plates 29 and 30, this member 33 being separated from the arc runner I5 by a layer of electrically insulating material 34. The two plates 3i and 33 are held in position against the ends of the blocks b'y means-of

screws

35 and 36 mounted in extensions -0n the members I3 and I6, layers of electrically insulating

material

31 and 38 being pro- 'vided between the screws and the members 33 and 3|.

As seen in Fig. 1, the adjacent spaced ends 39 and 40 of the iron plates 29 and 21 are formed so as to extend at an acute angle with the vertical, the rtwo ends being substantially parallel with each other. The adjacent ends of the plates 30 and' 28 are likewise formed to extend at an angle with-the vertical. Also, the plates 21 and 28 are wide enough at their bases or lower ends, as seen generates more heat than is radiated from the chute members with consequent eventual decrease in Fig. 1, so as to slightly overlap the lower end of the arc 'runner I5 whereby these two plates form part of the magnetic flux path of the entire arc at the time that the arc strikes from the lower end'of the runner I5.

In -order to reduce the undesirable effects of the magnetic ux induced in the plates 21 to III',

inclusive, they are provided withslots 21a to 30a, as shown in the drawing. the slots 21a and 28a extending substantially at right angles with the arc runner I 4 and the

slots

29a and 30a extending substantially at right angles with the arc runner I5.

I also provide at the top of the blocks I1 and I8 an arc cooler grill of the type described and claimed in Patent No. 2,293,513, issued on August 18,1942 to Leonard J. Linde comprising a plurality of vertically corrugated magnetic metal, such as iron, sheets or strips 4I which strips are electri` cally insulated from each other by strips 42 of electrically insulating material such as mica or iiber. Besides cooling the arc and` accelerating the movement of the arc, there iron sheets o r k strips serve to effect a nearly uniform distribution of the arc and gases across the blocks, i. e., from one end of the slot 2I to the other. By spacing the insulating strips 42 farther apart toward the left side of the chute, as seen in Fig. 1, and using deeper upright corrugations in the metal strips, a nearly uniform spread of the arc and gases is obtained resulting in efficient cooling.

The metal strips 4I and the insulating strips 42 extend crosswse of the members I1 and I8, as shown in the drawing. They are` held at their ends by U-shaped supporting members 42a and 42h into which their ends are inserted. The insulating strips 42 are wider than the metal strips in a vertical direction, as viewed in the drawing, and project above the metal strips at both the top and the bottom. The lower edges of the strips 42 rest on the upper plane surfaces of the chute members I1 and I8, and t tightly on the upper surfaces of the chute members.

It will be observed that the strengthof the magnetic eld is governed by the distance between the blocks I1 and I8 since the blocks 'are made of a magnetic flux conducting material, instead of by the much greater distance between the pairs of

plates

21, 28 and 29, 30. Thus as the arc rises, as seen in Fig. 1, and the distance between the blocks decreases, the air gap at that point, i. e., the distance between the blocks I1.

and I8, correspondingly decreases with a corresponding increase in magnetic iiux density for the propulsion of the arc upward into the narrow slot .2 I. In a typical device the slot 2I at the top of the chute was only if of an inch wide, this being the air gap at that point.

The magnetic field is increased by the half turn of the U-shaped'member I3 to the end of which one terminal 43 lof the electric circuit is connected. This connection of course leads to the stationary contact I8." Connections (not shown) are established between the opposite terminal of the electric circuit and the contact area I2 and movable contact Il. Also, an electrical connection 44 and ilexlble conductor 45 connect electrically the contact arm I2 to the lower end of the bar I6 so that the arc when it strikes to the runner I5 will be in the electric circuit of the circuit breaker. Electrically insulating supporting

plates

48 and 41 are provided on opposite sides of the device by means of which it may be secured to the base of the circuit breaker.

Thus it will be observed that the two arc chute members I1 and I8 serve as inner pole pieces for the pairs of

magnet plates

21, 28 and 28, 38. The amount of magnetic flux that is generated is in inverse proportion to the reluctance of the magnetic path which consists, for example, at one end of the device of the iron plates 21, 28 and 3|, the two chute members I1 and I8 and the air gap between the chute members. The reluctance of this path is very small except for the air gap, but the air gap at the top is very short, as short as sa of an inch in a typical device. Therefore., a

' large amount of magnetic flux is produced in each magnetic circuit at the ends of the chute by a small expenditure of electric energy. The magnetic ux is produced by the current in the half turn ofthe U-shaped member I3 and after the contacts have separated, by the current in the arc runners or arcing horns I4 and I5.

'The magnitude of the force pushing upward on the current carrying arc, asv with all current carrying conductors, is in proportion to the amount of the magnetic flux the arc includes. The arc moves in a direction to embrace the greatest amount of ux, consequently upward as seen in the drawing. The arc keeps on including more and more ilux regardless of its -guration until the very top edge of the chute is reached. The arc is restrained somewhat, of course, by the narrow passage of the chute.

It will be understood that by the use of material of higher electrically insulating value at crucial points, a magnetic insulating'material can be used for the chute members l1 and I8 havingl a lower electrical resistance than the preferred material described hereinbefore. This material would have a composition giving it a correspondingly higher magnetic permeability; for example, it may have an increased proportion of iron oxide. For example, as shown in Fig. 5, the arc runner member I4 is surrounded on three sides by an electrically insulating channel 48 made of a suitable electrically insulating material such as fibre or asbestos. This channel 48 electrically insulates the arc runner from the chute members I1 and I8 so -that these members can be made of a material having a higher magnetic permeability and lower resistance.

- While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. The combintion in a circuit breaker of a pair of contacts at least one of which is movable to close and open an electric circuit between said contacts, arc chute members on opposite sides of the path of movement of said movable contact made of a material which is electrically in- -sulating to cause an arc between said contacts to pass between said members andmagnetic to provide an increased magnetic field thereby to accelerate the movement of the arc between said members, and a pluralityof sheets of magnetic mtaerial adjacent the edges of said chute members toward which the arc moves extending transversely with respect to the arc for further accelerating the arc movement.

2. The combination in a circuit breaker of a pair of contacts at least one of which is movable to close and open an electric circuit between said contacts, and arc chute members on opposite sides of the path of movement of said movable contact made of a mixture of electrically insulating and magnetic materials which is electrically insulating to prevent the passage of an appreciable electric current therethrough and produce an arc between'said contacts when said contacts are separated and which has many times the magnetic permeability of air thereby to accelerate the movement of the arc between said 15 members.

3. Thecombination in a circuit breaker of a pair oi contacts at least one of which is movable toclose and open an electric circuit between said contacts, and arc chute members on opposite sides of the path of movement of said movable contact made of a mixture of iron oxide and a powdered basically inorganic electrically insulating material in proportions such that said members are electrically insulating to cause an arc between said contacts to Ipass between said members and magnetic to provide an increased magarc runners and gradually increasing in height netic iield thereby to accelerate the movement of the arc between said members.

4. The combination in a circuit breaker of a pair of contacts at least one of which is movable to close and open an electric circuit between said contacts, and arc chute members on opposite sides of the path of movement of said movable contact provided. with a plurality of spaced Walls extending at right angles to the'path of movement of said movable contact, said walls being made of a mixture of electrically insulating and magnetic materials which is electrically insulating to prevent the passage of an appreciable cur. rent therethrough and produce an arc between said contacts when said contacts are separated and magnetic to provide an increased magnetic field thereby to accelerate the movement of the arc between said walls.

5. The combination in a circuit breaker of a stationary contact, a cooperating movable contact having a predetermined path -of movement, a pair of complementary spaced members constltuting arc extinguishing members mounted on opposite sides of theV path of movement of said movable contact providing a plurality of spaced apart substantially parallel walls substantially perpendicular to said path of movement,

said members being made of an electrically insulating material having many times the magnetic permeability of air thereby to provide an increased magnetic field by the current in an arc between said contacts to force the arc between said spaced members, and a plurality of sheets of magnetic material adjacent those edges of said walls toward which the arc moves and extending transversely with respect to the arc for further accelerating the movement of the arc.

6. The combination in a circuit breaker of a stationary contact, a cooperating movable con,-i

tact having a predetermined path of movement, a pair of plates forming an arc chute on opposite sides `of the path of movement of said movable contact, a plurality ofparallel ridges on the-adjacent sides of said plates with the ridges on one plate interleaved with the ridges of the other plate and uniformly spaced with respect theretov and said ridges beginning at points adjacent said arc runners and gradually increasing in height tothe upper extremities of said plates so that an `arc between said runners is increasingly elongated in passing between said ridges as it moves upward .between said plates, said plates being `made of a mixture of electrically insulating and 'lpair of spaced apart upwardly diverging arc runner members, `va stationary. contact -on the lower end -of one of said runner members, a cooperating; movable cont-act having a predetermined path of movement extending under the ,75

to the upper extremities of said plates so that an arc between said runners is increasingly elongated in passing between said ridges as it moves upward between said plates, and a pair oi plates of magnetic metal forming pole pieces on the exterior of said insulating plates in direct engagement with said plates and on opposite sides of each of said arc runners.

8. The combination in a circuit breaker of a stationary contact, a cooperating movable contact having a predetermined path of movement,

a pair of complementary spaced members con-'- stituting arc extinguishing means mounted on opposite sides of the path of movement of said movable contact providing a plurality of spaced apart plates substantially perpendicular to said path of movement, said members being made of a mixture of powdered electrically insulating and magnetic materials having many1 times the magnetic permeability of air` thereby to provide an increased magnetic field caused by the current in an arc between said vcontacts whereby the arc is forced by said field between said spaced members and thereby elongated, a. pair of plates of magnetic metal on the exterior of said members in direct engagement with said members on opposite sides of said stationary contact, and a member of magnetic metal on the side of said stationary contact opposi said movable contact forming a magnetic path of high permeability between said plates, said plates and said connecting member forming a path of high magnetic p member made of lmagnetic material extending y around at least one of said arc rlmners and being substantially coextensive lengthwise with said one arc runner and having its sidesl on the outside of said arc chute members and projecting beyond said one arc runner on opposite sides of the path of an arc between said arc runners, a. layer of electrically insulating material between said U-shaped member and said one Aarc runner, said U-shaped member having a magnetic iiux induced therein solely by the current in an arc between said arc runners, and a plurality of sheets ormagnetic material adjacent edges of said chute members toward which the arc moves extending transversely with respect to the arc for further accelerating the arc movement.

10. The combination in a circuit breaker of a pair of contacts at least one of which is movable to close and open an electric circuit between said contacts, arc chute members made of electrically insulating material on opposite sides of the path of movement of said movable contact, arc runnetic material adjacent edges of said chute members toward which the larc moves extending transversely with respect to the arc for further accelerating the arc movement.-

11. The combination in a circuit breaker of a pair of contacts at least one of which is movable to close and open an electric circuit between said contacts, arc chute members made of electrically insulating material on opposite sides of the-path of movement of said movable contact, arc runners between s-aid chute members, a U-shaped member made of magnetic material extending around at least one of said arc runners substantially coextensive with the length of said one arc runner having its sidesl on the outside of said arc chute members and projecting beyond said one arc runner on opposite sides of the path of an arc between said arc runners, a layer of electrically insulating material between said one arc runner and said U-shaped member, a blowout coil in the electric circuit between said contacts, a core member made of magnetic material encircled by said blow-,out coil, and pole pieces of magnetic material on opposite ends of said core member extending outside of said arc chute members on opposite sides of the path of movement of said movable contact.

' 12. 'I'he combination in a circuit breaker of a pair of contacts at least one of which is movable to close and open an electric circuit between said contacts, an arc runner member made oi! electrically conducting material extending upward from 'said stationary contact, a vsecond arc runner spaced from 4vsaid flrst'arc runner extend-` ing upward in diverging relation witherespect to said nrst arc runner, an electrical connection between said second arc runner and said movable contact, isaidsecond arc runner`having its lower end in closely spaced relation with said movable contact when said movable contact is in its open circuit position so that an arc between said contacts rises along said arc runners, arc chute members made of electrically insulating material on.-

opposite sides of said contacts and said arc runners, a pair of plates made'of magnetic material on opposite sides of each of said arc runners and outside oi'v said arc chute members, said plates being substantially coextensive with the length ci; each of said arc runners and extending beyond each of said arc Arunners on opposite sides of an arc between said arc runners, and a length 'of magnetic material onv the outside of each of said arc` runners Vjoin-ing together' its pair of plates, a`\layer oi electrically insulating material between each of said lengths and its arc runner, said lpairs of plates acting by reason o'f the flux induced insaid plates by the current` in an varc between said arc runners to force the arc upward' y jacent edges of said plates remote fremsaid conalong said arc runners and between said arc chute members;

13. The combination in a circuit breaker of a. pair of contacts atleast one of which is movable to close and open an electric circuit betweensaid contacts, a pair of spaced apart arc chute members made of electrically insulating material on opposite sides of the path of movement of said movable contact, said members comprising walls converging toward each other in the direction of arc travel, said walls being made'of a. mixture of -basically inorganic electrically ,insulating material and a small proportion of magnetic mal terial to make said walls magnetic as compared with the air thereby to accelerate the movement of the arc between said converging walls.

14. 'Ihe combination in a circuit breaker of a pair of contacts at least one of which is movable to close and open an electric circuit through said contacts, and arc chute members on opposite sides of the path of movement of said movable contact at least one of which is made of a mixture of electrically insulating material and magnetic material having substantially uniform lelectrically insulating characteristics which are high enough to prevent the flow through said members of substantial currents at the voltage between said contacts and having substantially uniform magnetic characteristics which are'high enough to accelerate the movement of an arc drawn between said contacts. 4

15. The combination in a circuit breaker of a pair of contacts at least one of which is movable to close and open an electric circuit through said contacts, a pair of arc chute plates on opposite sidesof the path of movement of said movable contact, each of said plates being in one piece made of a mixture of powdered electrically in'- sulating material and powdered magnetic material in such proportions that said plates have a high resistivity to prevent tire flow through them of substantial currents at the voltage between said contacts and are magnetic to accelerate the movement between them of an arc from one of said contacts to the other, a pair of plates of magneticmetal on the exterior of said arc chute plates in direct engagement throughout substantially their entire surfaces vrespectively with said arc chute plates. and a magnetic metal plate across one of theends of said arc chute plates Joining said nrst two metal plates.

16. The combination in a circuit breaker oi' a pair of contacts at least one of which is movable to close and open an electric circuit through said contacts, a pair 'of arc chute plates on opposite sides of the path of movement of said movable contact, each of said plates being in onepiece made oi a mixture of electrically insulating material and magnetic `material in such proportions that said..

plates have a high resistivityto prevent the iiow .through them oi' substantial currents at the voltage between said contacts and are magnetic to accelerate the movement between them of an arc from one of said contacts to the-other, and a plurality of spaced sheets of magnetic metal adtacts extending transversely with respect to said V plates for further accelerating the movement o! an arc between said plates.

. LUDWIG S. WALLE.