US2673912A

US2673912A - Arc extinguisher

Info

Publication number: US2673912A
Application number: US229090A
Authority: US
Inventors: James M Wallace; Howard W Graybill
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1951-05-31
Filing date: 1951-05-31
Publication date: 1954-03-30
Anticipated expiration: 1971-03-30
Also published as: FR1069651A

Description

3 Sheets-Sheet l l`Il 11111114 Insulation Insulation f/l Il Nylon sew RC 0mm. n Tlf NOG. E WW V T m m T a. A m W O nm Vl J dB n 0 E` s. s I E my? .w

March 30, 1954 J. M. WALLACE ET AL ARC EXTINGUISHER 3 sheets-sheet '2 Filed May 3l, 1951 Fig.5.

Fiber /Boric Acid R. MS. Amperes INVENToRs James M.Wu|loce und Howard W. Groybill. j BY.

` ATTORSEY WITNESSES: L/Wgy March 30, 1954 Filed May 51, 1951 J. M. WALLACE ETAL ARC EXTINGUISHER 3 Sheets-Sheet 3 ATTORN Patented Mar. 30, 1954 VARC EXTINGUISHER James'M. Wallace, Pittsburgh, and Howard W.

Graybill, Greensburg, Pa., assgnors to Westinghouse Electric Corporation, East Pittsburgh, Ba., a corporation of Pennsylvania.

i Application May 31, 1951, Serial N0. 229,090

`Arc extinguishing materials are applied in or adjacent to those portions of circuit interrupters that' are subject to the establishment of an arcv when in service. The heat of the arc will effect a-decomposition of the arc extinguishingmaterial resulting in an evolution of large quantities of `gas which destroys orextingui'shes'the are, or creates a conditionV whereby thearc cannot be sustained. In addition to the gas evolvng'qualities of the arc extinguishing material, it must also be and remain an insulator at all times, and substantial quantities of conducting carbonaceous material, such as soot, should not be formed on thesurface of the arc extinguishing material as a result of having been subjected to an arc.

'A `material frequently used as anarc extinguishing material `is boric acid. However, the use of `boric acid hasbeen unsatisfactory in) many cases because of its relativelyv low mechanical strength and othery physical properties. In particular, boric acid is difficult to form or shape bymolding'with or without machining.' Thus, the lack of suitable mechanical properties make it diillcult to use boricy acidin many applications for which its electrical arc extinguishing characteristics areotherwise satisfactory. VThe 'same limitations apply to numerous other inorganic solids' which when subjected' tov arcing conditions will give oil a gas. VFor instance, magnesium borate, oxalic acid, ammonium borate Vand the like by themselves are weak mechanically,` thus placing `a limitationl on their use as an are extinguishing material.

'It is also to be noted that ber may be employedin circuit interrupters with some success since it possesses a high degree of mechanical strength, in spite of the fact 'that its arc interrupting ability is not cuite as satisfactory as that of'boric acid. However, ber is subject to warping whereby-satisfactory operation of1 circuit interrupters employingtheber may-be'dctrimentallyzaffected. l a u Anobiect of thisinvention is the' provision of a circuit interrupter having an arc confining and interrupting, structure comprising nylon.

' A furtherobject of this invention is the provision of `an arc confining and interrupting structure suitable for repeated use comprising a nylon material which evolves an adequate amount of gas for extinguishing an arc and has a low rate of erosion or deterioration.

These and other objects of thisinvention will tbrm'lsh''une .forni of'circuit interrupter; i

3 Claims. (Cl. 200-149) Fig. 2 is a cross section through an elevation view of a fuse link;

Fig. 3 is a view partly in plan and partly in section of the device shown in Fig. 4, the section being indicated by the ine III-III thereof;

Fig. 4 is an elevaticn view of a disconnect switch;

Fig. 5 is a graph plotting loss by erosion against amperes and showing the erosion of numerous arc extinguishing materials for various current inputs to a circuit interrupter; and

Fig. 6 is a graph plotting restored kilovolts on an arithmetic scale against amperes on a logarithmic scale and illustrating the interrupting characteristics for a plurality of fuses each having an arc extinguishing member comprising a different material.

According to the present invention, arc conning and extinguishing portions of circuit interrupters are prepared from nylon or superpolyamides, which we have found have unusually low erosion characteristics when repeatedly subjected to an arc.

There are a pluralityV of processes for producing nylon or superpolyamide resin and the following described process is only one of many such processes. In this process polyamides are obtained from polyamide-forming reactants, as for instance by self-polymerization oi aminocarboxylic acids or by heating a polyamine with a polycarboxylic acid under polymerizing conditions until a high molecular weight polyamide is obtained. Particularly useful for the present purpose are the linear or fiber-forming polyamides or superpolyamides disclosed in U. S. Patents 2,071,253 and 2,130,948. However, non-.fiber forming superpolyamides may be employed. The reaction of unsaturated polycarboxylic acids such as malic acid with or without a saturated dibasic acid, with a polyamine will produce crosslinked superpolyarnide resins. The linear polyamides, which are usually definitely crystalline rather than resinous, are obtainable from bifunctional reactants, asfor instance from diamines and dicarboxylic acids or by the selfpolymerization of monoamino monocarboxylic acids or theirJamide-forming derivatives, e. g., the lactams, the reaction being continued until the polyamide has a viscosity of at least 200 poises at 285 C. or has an intrinsic viscosity of 0.6 as dei-ined in U. S. Patent 2,130,948. These nylon polymers as defined herein include, but lare not limited to, the linear ber-forming polyamides which contain recurring amide groups as an integral part oi the main chain of atoms in the molecule and which are obtained by including with the polyamide-forming reactants other bifunctional, reactants, such as glycols in which 'case esteramide interpolymers are obtained.

V Although the larger portion of the arc extinguishing vmember should lcomprise nylon, it is to be understood that for securing excellent results, both mechanically and electrically, the arc extinguishing material may contain other substances. Less than 50% of the weight of the arc extinguishing member may be composed of reinforcing fibers, such as asbestos or glass fibers, or solid, inorganic materials, such as titanium dioxide, silica, magnesium oxide, or the like. It will be appreciated that other gas evolving materials, such as boric acid, ammonium berate or magnesium borate, as Well as reinforcing solids, may be incorporated in the nylon.

Referring to Fig. l ofthe drawings, there is nillustrated a circuit interrupter comprising a stationary contact member I having a passage I2 therein. The stationary contact member I0 is threadedly engaged with a tube or sleeve I4 of nylon which is capable of evolving arc extinguishing gas in the presence of an electrical arc. The remainder of the circuit interrupter comprises a movable contact member I6 which is disposed for reciprocating motion within a passage I8 contained within the tube I4.

In operation, a circuit may be closed by actuating the movable contact member I6 downward into engagement with the stationary contact member I0. On actuating the movable contact member I6 upward from its circuit closing position, an arc will be established between the movable contact member I6 and the stationary contact member I0 which arc will effect a partial decomposition of the nylon forming the tube I4, thus evolving an arc extinguishing gas. The arc-extinguishing gas resulting will flow to the passage I2 and will exert a cooling and deionizing effect on the arc, thus extinguishing it.

Referring to Fig. 2 of the drawings, there is illustrated a fusible interrupting device which comprises another embodiment of this invention. The fusible interrupting device comprises an elongated insulating tube of nylon having a terminal ferrule 22 threadedly engaged with the upper end thereof, and a lower terminal collar 24 disposed around the outside of the insulating tube 20 adjacent the lower end thereof and secured in position on ther tube by a set screw 26.

In order to secure a removable fuse link unit 28 within the fusible interrupter, an upper terminal cap 32 is threadedly engaged with an extension of the terminal ferrule 22 so that the upper portion 34 of the removable fuse link unit 28 is secured between the cap 32 and the upper portion of the ferrule 22. The fuse link unit 28 comprises an upper terminal portion 36 electrically connected by a fusible member 33 to a lower terminal strip 40, all of which are disposed within a relatively small arc confining and extinguishing tube 42 of nylon. The lower terminal strip 40 is resiliently held away from the upper terminal strip 36 by means of a spring 44 held in compression between the tube 42 and a pin 46 connected to the lower end of the lower terminal strip 40. For the purpose of completing an electrical circuit from the lower terminal strip 48 to the lower terminal collar 24 one end of a exible conductor 48 is connected by soldering, or the like, to the lower terminal strip 40 and the other end of the conductor 48 is electrically connected to the lower terminal collar 24 and there held in place by the set screw 26. .i

The main function of the tube 42 is to confine low current arcs resulting from the fusion ofthe fusible member'i so that the nylon gas evolving composition comprising the tube is in close prox- 4 imity to the'fusible link unit 28, thereby assuring a rapid and efficient extinction ofarcs of low current value. When the fusion of the member 38 is due to a short circuit which effects a high current ow through the circuit interrupter, the tube 42 is suiliciently weak to completely disintegrate, thereby relieving the gas pressure developed .and permitting the arc extinguishing gases to expand within the larger volume encompassed by the tube 20 as well as permitting the arc to come in contact with the tube 26, thus developing sufficient gas to assure the extinction of the arc. For this reason the tube 42 is preferably composed or prep'afred from a composition having somewhat more fibrous Vreinforcement than the tube 20, for example, 10% or moreA bye weight of fibrous material. i

Referring to Fig. 4 of the drawings, there is illustrated still another embodiment of the teachings of this invention. The disconnect switch illustrated comprises a pair of supporting

insulators

50 and 52, such as porcelain insulators or the like, on which the switch proper is mounted. The supporting insulator 52 is illustrated as having a hinge tongue casting 54 secured thereon as by bolts 56, and it is provided with an integral terminal 58 to which a line conductor may be secured in any desired manner. The 4hinge tongue casting 54 is apertured for the reception of a pivot bolt 60 for pivotally mounting a split switch blade 62.

The supporting insulator 50 is adapted to support a stationary cont-act tongue 64 having an integral base which is secured to the 'insulator 50 and having an integral outwardly extending terminal 66 to which a line conductor maybe secured in any desired manner. The stationary contact tongue 64 is preferably provided'with a slot for receiving bolt 68 in the closed position of the switch, as illustrated in Fig. 4. An actuating handle 10 is adapted to be secured between the outer edges of the sides of the blade 62 and is preferably provided with a hookeye 12 for the reception of a hookstick, operating member or. the like.

For the purpose of interrupting load currents, switch blade 62 is provided with an auxiliary snap acting. blade 14 adapted to be vdisposed in spaced relation with respect to one side of the blade 62. The auxiliary blade 14 is mounted by means of bolts 15 on a box-like casting. 16 which is supported in turn` by a. pivot bolt 82 so -asto .be freely rotatable on this bolt, which is secured in the split blade 62. The side of the mounting casting 16 which lies adjacent the main Iblade 62 is notched, as shown at 88, to receive a stop screw `9|) mounted in the main blade-.62. Thepurpose lof stop screw 96 is to limit pivotal movement of the auxiliary blade 14 relative to the main blade 62,

Thelstructure .thusfar described is substantially identical to that structure disclosed in the Rawlins Patent No. 2,308 026, and accordingly for a more complete description of such parts and their operation, reference may be .made thereto.

However, this invention is primarily concerned with the material fromwhich arc chute 941s constructed. The arc chute 94 comprises a pair of spaced plates 96 which may be machined or molded to shape. The plates 96 are provided with liners 58 and |80 which are disposed ad-` jacent the spring-biased contact clips y9| andthe cooperating "snap actingblade 14. The liners 98 and |00 are 'formed from nylon and they are maintained in place by means of the screws |02. It is of course to be understood that the plates 96 and the liners 98 and |00 could be integral.

W'hen it is desired to open the switch from the closed position, as shown in Fig. 4, a hookstick or other operating member is inserted in hookeye 12, fand the lmain blade 62 is pulled away from the stationary Contact tongue 64. How-v ever, the auxiliary blade 74 is held fri-ctionally between the spring-biased contact clips 6|, while the auxiliary blade 'I4 rotates on the pivot bolt 82 and stresses a spring 92. rlhis movement of the parts continues until the main switch blade 62 is separated a substantial distance from the stationary contact tongue 64, and the other side of notch 83 of the mounting xture 76 engages the stop screw 90 whereupon continued opening movement of the main switch blade 62 causes the auxiliary plate 74 to be pulled out of the spring-biased contact clips 9|. As soon as the auxiliary blade 'I4 escapes from frictional engagement with the clips 9|, its biasing spring 92 acts to rapidly move the auxiliary blade counterclockwise relative to the ymain blade 62 in a pivotal manner about the bolt 82 to restore it to a parallel relationship with the main switch blade 62, this movement being arrested by the engagement of the side of the notch ywith the stop screw I90. Preferably, this snap action of the auxiliary blade I4 takes place substantially throughout the narrow slot formed between the liners 98 and |00 of nylon so that the arc drawn upon separation of the auxiliary -blade 'M from the spring-biased contact clips 9| will @be very rapidly elongated through the arc chute S4 and extinguished therein. The liners 98 and |00 of nylon composition when subjected to such an arc will develop a large quantity of un-ionized arc cooling gases and the use of nylon assures a rapid and effective extinction of the arc as well as other advantages which will be hereinafter mentioned.

In order to return the disconnect switch to the circuit "closing position, the main switch blade 62 is manually actuated into engagement with the stationary contact tongue `64. During the closing movement of the main blade 62 the auxiliary blade `'I4 remains parallel thereto due to the combined action of the stop screw 90 and the notch 88 in the xture 16.

Referring to Fig. 5, there is illustrated a graph which represents the erosion characteristics for fuse members iwhose arc extinguishing material are made from ber, boric acid and nylon, respectively. These tests were conducted with separate groups of 4 'inch fuses having a 1/4 inch bore, a group being made from ber, boric acid and nylon, respectively. It is to be noted that, as indicated by th-ese tests, the loss in grams per half cycle of arcing for any one of the various values of current ow through the fuse constructed of nylon was only a small percentage of that loss indicated for the fuses constructed of ber or boric acid. Thus, by manufacturing the -arc extinguishing material utilized on various circuit interrupters from nylon, the operating life of the circuit interrupter can be greatly extended, which is an extremely important factor.

Referring to Fig. 6, there is illustrated a graph which represents the interruption characteristics for fuse members having arc extinguishing members made from boric acid, ber, and nylon, respectively, and Whose length and bore are 4 inches and 1/4 inch, respectively. In particular, the graph illustrates at what open circuit voltage across the fuse and corresponding current iiow through the fuse, each fuse will interrupt a circuit within a period of time of ve half cycles of arcing. It is to be noted that the fuse made from nylon has far superior interruption characteristics as compared to the boric acid and ber fuses up to approximately 200 root-meansquare amperes. The nylon fuse also has interruption characteristics that are superior to those of the ber fuse up to approximately 400 rootmean-square amperes. The superior interruption characteristics for the nylon fuse permits the use of a smaller size fuse, as compared to the boric acid or ber fuse, and still have the same interruption characteristics. This is of considerable advantage both from the standpoint of original cost, as well as a saving of space which under many circumstances is extremely important.

Having described preferred embodiments of our invention, we wish it t0 be understood that the invention is not limited to the particular embodiments disclosed herein since it is apparent that many changes and modications may be made in the composition and the various structures shown without departing from the broad spirit and scope of the invention.

We claim as our invention:

1. A circuit interrupter` comprising in combination a fusible link which may be fused forming an arc, an arc extinguishing and confining means consisting of at least 50% by weight of a resin and the balance being a non-resinous ller, the resin being composed substantially entirely of superpolyamide, the arc extinguishing and conning means being so disposed with respect to the means for establishing an arc as to provide for evolution of an arc extinguishing gas when subjected to the arc.

2. A circuit interrupter including means for establishing an arc, and arc extinguishing and conning means consisting of at least 50% by weight of superpolyamide resin, the balance composed of at least one of the group consisting of ber reinforcing materials and solid llers, the arc extinguishing and conning means being so disposed with respect t0 the means for establishing an arc as to provide for evolution of an arc extinguishing medium when subjected to the arc.

3. A circuit interrupter including means for establishing an arc, an arc extinguishing and conning means consisting entirely of superpolyamide resin, the arc extinguishing and confining means being so disposed with respect to the means for establishing an arc as to provide for evolution of an arc extinguishing medium when subjected to the arc.

JAMES M. WALLACE. HOWARD W. GRAYBILL.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,300,208 DAlelio Oct. 27, 1942 2,308,026 Rawlins Jan. 12, 1943 2,377,866 DAlelio June 12, 1945 2,434,315 Froland Jan. 13, 1948 2,516,026 Strom et al. July 18, 1950 2,526,448 Amundson Oct. 17, 1950