US2106316A - Circuit interrupter - Google Patents

Description

INVENTOR (XW/fz f//da/ ATTORNEY C. L. DENAULT CIRCUIT INTERRUPTER Filed March 29. 1934' Jan. 25, 1938.

Patented Jan.. 25, 1938 y CIRCUIT INTERRUPTER Clinton L. Denault, Forest lilll, Wilkimbnrg, Pa.,

assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 29, 1934, Serial No. 717,940

19 claims.; (C1. 20c-1z0) My invention relates to 'circuit interrupters and'Y particularly to high voltage circuit interrupters .of the type which utilizes an expulsive gas blast for extinguishing the arc formed incident to the interruption of the controlled circuit.

The commonest form of expulsion circuit interrupter is the well known expulsion fuse. This device usually comprises a tubular arc passage, a means, such as a fuse, for establishing the arc within the tubular arc passage, and a means for producing an expulsive gas blast which ilows longitudinally through the arc to effect its extinguishment. The simplest method of producing this gas blast consists in the provision of a lining for the arc passage which is formed of a material that is capable of evolving considerable quantities of an are extinguishing gas when placed in proximity to an electric arc. The eiliciency and the reliability of operation of these devices depends to a great extent upon the amount and the chemical characteristics of the gas which is. caused to expulsively flow through the arc during the circuit interrupting operation, and one principal problem of the art has always d been the securing of an adequate volume of gas having a satisfactory chemical composition.

The rate of evolution of gas from the surface of the lining of the arc passage depends to a great extent upon the intimacy of contact between the lining and the arc, and it is obvious that the maximum possible evolution of gas (and the most efficient operation of the interrupter) will be effected when the arc completely fills the arc passage. Unfortunately, however, the magnitude of the overload current in most present-day circuits varies through wide limits, and the physical dimensions of the arc `likewise vary, in direct proportion. It might appear that this would not create any serious diili'culties, since the arc pas- 40 sage could be made small enough to cause an intimate engagement between the lining and the surface of the smallest magnitude arc that might be drawn within that passage.

The problem is not so simply solved, because, while intimate engagement between the lining of the arcvpassage and the arc is imperative, it

55 may be sufliciently to become cenducting `danger of rupture or excessive heating. vious result of this is that for most circuits the COD- circuit interrupter, or failure ofJ the device to.

operate, during the occurrence of very heavy overload conditions makes it necessary that the physical dimensions of the arc passage shall be sufficiently large to permit an arc having the largest possible .current magnitude considering the circuit with which the device is to be used, to be drawn within the arc passage without The obarc pasage must have a very considerable crosssectional area, and when the interrupter is in use on such circuits, the low magnitude arcs produced by normal overloads will but partially illl the arc passage. Under these conditions, only a small volume of arc extinguishing gas will be generated, and the eiliciency of the interrupter will be very low. In fact, if the current magnitude of the arc is very small, and the dimensions of the arc passage, even reasonably large, a small current arc drawn therein may not be extinguished at all. i

To overcome this difficulty, and to assure efflcient operation o-f the interrupter under varying conditions ofarc current, the prior art structures have utilized two arc passages, one of large' cross-sectional area, wherein arcs of heavy current magnitudes are interrupted, and one of small cross-sectional area wherein arcs of a lower current magnitude are extinguished. Y This arrangement requires selective means for assuring that the are shall be drawn in the proper passage and is not entirely satisfactory from an economic viewpoint. A

TLhe principal object of my invention, therefore, is to provide; an improved expulsion circuit interrupter of the type discussed above that shall utilize but a single arc passage, and that shall be provided with means for assuring the satisfactory interruption of both small and large current arcs in that passage.

In carrying out this object of my invention, I provide a suitable means for defining an are passage, means, such as a fuse, for establishing an arc within that passage, and means of insulating material positioned within that passage so as to form a narrow passageway which is substantially annular in cross-section. By this means, the opposed surfaces of the insulating members which define the walls of the arc passage are at all times spaced closely adjacent each other, and at the same time the actual total crosssectional area or the arc passage is comparatively large. Thus, even an are of low current magnitude is caused to intimately contact the surfaces of the arc passage so as to decompose the gas evolving lining of that passage and effect its extinguishment, and at the same time there is suilicient area wherein arcs or large current magnituale may spread so as to prevent the building up of excessively high pressures Within the arc passage.

In the preferred embodiment of my invention, provide aicylindrical tube of hard fibre vhaving relatively heavy side walls `i'or defining the arc passage, and a cylindrical rod likewise of hard bre positioned within and concentric with the y main tube. The arc passage is thus defined by a pair of concentric cylindrical surfaces and is periorce of substantially constant width. Hard bre, as is well known in the art, decomposes when exposed to the heat of an electric arc to form a large quantity of an arc extinguishing gas, and during the operation of the interrupter this gas flows longitudinally through the arc with an expulsive action to effect its extinguishment.

It is, ofcourse, within the province of my invention that the outer tube or the centrally disposed volume restricting member could be formed of a refractory material or of a gas evolving material different from the fibre. One material which I have found particularly suitable for this is boric acid, that material evolving a large quantity of an inorganic, non-inflammable gas when placed in proximity to an electric arc. Boric acid has another advantage in that thel surface does vnot become conducting even when heated to the temperature of an electric arc, this characteristic assuring that the full circuit voltage will not break down along the surface of the arc passage.

Since as pointed out above, one of the principal elds for immediate application of my invention is in connection with expulsion fuses, I shall hereinafter describe an embodiment of' my invention as applied to such devices, without, however, in any way intending to restrict the scope of my invention except as indicated in the appende claims.

Referring to the single sheet of drawing,

Figure l is a sectional view of an expulsion fuse wherein are embodied the principal features of my invention;

Fig. 2 is a sectional view taken on the line II-II of Fig. 1;

Fig. 3 isa sectional view taken on the line III-HI of Fig. 1;

Fig. 4 is a bottom plan view of the fuse shown in Fig. 1; and

Fig. 5 is a fragmentary, sectional view showing a modified form of the fuse structure illustrated in the other figures of the drawing.

The expulsion fuse shown in the drawing comprises, generally, a main tube I of fibre or like insulating material which possesses sufncient strength to withstand the pressures ordinarily developed within these devices, a metallic cap or ferrule 3 for enclosing the upper end of the main insulating tube, and a second ferrule 5, hraving a centrally disposed opening 'I therein, for engaging the lower end of the main insulating tube I. Both the upper and the lower ferrules are adapted to be retained in position by means of suitable screw threads 9 formed in the cooperating yportions of those members. A cylindrical rod member II of insulating material, preferably nbre, is positioned within and concentric with the main tube in order to define the annular arc passage Il.

The ,upper endof the rod member II is provided with a threaded opening Il therein which isadapted to be engaged by the positioning screw I1 extending down through a suitable opening in the upper ferrule. lThe lower end of the rod member Il is likewise provided with a threaded opening I9 which is adapted to be engaged by a sirnilar positioning screw 2l extending through suitable opening in the bridge member 23 which extends across the opening "i in the lower er- 'rule 5.

The central portion of the bridge member 23 is supported in the position shown in the drawing, by means of a pair of radially extending spoke members 25 formed integral with the lower ferrule. Except for these spoke members 25, the opening I within the lower ferrule 5 is of substantially the same cross-sectional area as the annular arc passage I3. The opening T has a funnel shaped portion 2l at its extreme lower portion in order to facilitate the outflow of the arc extinguishing gas from the arc passage.

The cylindrical rod member II is provided with two sets of positioning members 29 which are shown particularly in Figs. 1 and 2. These positioning members are adapted to project outwardly from the'rod member I I in a substantially radial direction and are disposed between the rod member and the main tube in order to prevent any warping which might occur during service from causing relative displacement of the rod member II with respect to the inner walls of the main tube I. As shown, these positioning members 29 are formed of insulating material and are cemented or otherwise securely amxed to the outer surface of the rod member II.' It is possible, however, to form these members of metal or any other material which will retain its strength during the arc extinguishing operation.

A fuse wire II, the upper end of which is connected by means of a screw 33 to the upper ferrule l and the lower end of which is connected by- CTI adapted to be supported upon suitable clips or other means which are well known to the art.

Inv the preferred embodiment of my invention,

the centrally disposed rod member II is formed of hard fibre as is the main tube I. This arrangement is desirable in that it is inexpensive, and at the same time provides an adequate blast of arc extinguishing gas for effecting the extinguishment of the'arc. it is possible, and in some cases desirable, to form the rod member II of a refractory material, or the main tube itself may be formed of a refractory material, and the rod member formed of a gas evolving material. It is also possible. and in some cases desirable, to provide a lining l! of compressed boric acid for the inner surface of the main tube I and to form the rod member II of that material, such a structure being shown in Fig. v5. 'I'he use of boric acid as a lining for the arc passage assures a gas blast which is noninflammable and which is inorganic in lts chem-l ical composition. Also, the arc interrupting emciency ofl the gas evolved from a boric acid lining is somewhat greater than that evolved from a similar means formed of nbre.

f Upon the occurrence of a predetermined overload in the circuit controlled by the device, the fusible element II melts and causes an arc to be established within the annular `irc passage Il. If the magnitude of the overload current causing As mentioned above, however,v

rso

the melting of the fusible element Il is small, the arc occupies only a portion of the annular arc i'passage, but, because of the comparative nearness of the opposed surfaces which define this arc passage, asuiiiciently intimate contact between the arc and the gas evolving lining is effected to assure a rapid extinction of the arc by the outiiowing blast of gas which flows longitudinally through the arc passage. If the magnitude of the arc current is large, a substantial portion of the annular arc passage may be occupied by the arc, and as the upper range of safe operation of the device is reached, the entire arc passage will be entirely filled by the arc., Under any of these circumstances, however, the arc is caused to intimately contact the gas evolving lining of the arc passage walls and a rapid and efficient extinction thereof is effected.

From the foregoing, it will be seen that I have provided an improved expulsion-type circuit interrupter which is capable of satisfactorily interrupting arcs of small and of large current magnitude within a single arc passage, this arrangement differing from the prior art devices which utilize at least two arc passages for accomplishing the same result. The structure of the preferred form of my invention is comparatively simple and the cost of devices wherein my invention is embodied is not materially increased despite the greatly improved operation which results.

I have also disclosed certain preferred structural arrangements which are particularly suitable for carrying out the objects of my invention, and I have disclosed certain types of materials which are particularly adapted for use in conjunction with my invention.

While in accordance with the patent statutes, I have disclosed the foregoing details of practical embodiment of my invention, it is to be understood that many of these details are merely illustrative, and that the broad features of my invention are capable of much wider adaptation than to the particular structure disclosed in this application. I desire, therefore, that my invention shall be given the broadest reasonable construction, and that'the claims shall be limited only by what is expressly stated therein and by the prior art. y

I claim as my invention:

1. In an expulsionfuse, means of insulating material for defining the outer walls of an arc passage, said outer Walls completely enclosing the sides of said passage, means for closing one end of said passage during each circuit interrupting operation, the other end of said passage being open during each circuit interrupting operation, means including a fusible element for establishing an aro within said passage, and means of insulating material positioned within said passage for so restricting the volume of said passage that arcs of small current magnitude as well as arcsof large current magnitude are caused to intimately contact the inner surface of said `wall defining means during each circuit interrupting operation.

2. In an expulsion type circuit interrupter, means, at least partially of insulating material for defining a completely closed outer surface of an arc passage; means for closing one end of said passage, the other end of said passage being open, during each circuit interrupting operation; meansat least partially of insulating material, positioned within said passage, at least during each circuit interrupting operation for defining the inner surface of said arc passage; and means 3. In an expulsion type circuit interrupter, l

means, at least partially of insulating material,V for defining a completely closed outer surface of an arc passage; means for closing one end of said passage, the other end of said passage being open, during each circuit interrupting operation; means, at least partially of insulating material, positioned within said passage, at least during each circuit interrupting operation for defining the inner surface of said arc passage,

and means for establishing an arcrbetween said inner and said outer surfaces; said surface defining means so restricting the volume of said passage that arcs of small current magnitude as well as ares of large current magnitude are caused to intimately contact the surfaces defining said arc passage during each circuit interrupting operation; at least a portion of one of the surfaces of said arc passage being lined with a material which is capable of evolving substantial quantities of an arc extinguishing gas when placed in proximity to an electric arc.

4. In an expulsion fuse, means defining the walls of a substantially tubular passage which is completely closed along the sides thereof, means for closing one end of said passage at least during each circuit interrupting operation, the other end of said passage being open during each circuit interrupting operation, means including a fusible element for establishing an arc within said passage, and means of insulating material for so restricting the volume of said passage that arcs of small current magnitude as Well as arcs of large current'magnitude are caused to intimately contact the inner surfaces of said passage during each (arc extinguishing operation, at least a portion of the inner surface of said wall defining means being lined with a material which is capable of evolving substantial quantities of an arc extinguishing gas when placed in proximity to an electric arc. v

5. In a circuit interrupter for use with circuits subjected to overloads of varying magnitude; means at least partially of insulating material for defining a completely closed outer surface of an arc passage; means at least partially ofinsulating material positioned within said passageway, at least during each circuit opening cperation of said interrupter, for defining the inner surface of said arc passage; and means for establishing the arc incident to each opening op- 60 rent magnitude are caused to intimately contact the surfaces defining said arc passage during the circuit interrupting operation; at least a portion of one of said surface defining members being formed of a material which is capable of evolving an arc extinguishing gas when placed in proximity to an electric arc and means for venting said passage.

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6. In a circuit interrupter for use with circuits subjected to overloads of varying magnitude; means at least partially of insulating material for defining the outer surface of an arc passage; means which is also at least partially of insulating material and which has a substantially cylindrical outer surface positioned within said passageway, at least during each arc extinguishing operation of said interrupter, for defining the inner surface of said arc passage; one end of said passage being open at least during the circuit opening operation; said outer and inner surface defining means being completely closed, means for establishing the arc incident to the opening operation of said interrupter within said a-rc passage; .the'cross sectional area of said surface defining means which is positioned within said passageway being so correlated with respect to the cross sectional area of said passageway that arcs of small current magnitude as well as arcs of large -current magnitude are caused to intimately contact said inner and said outer surfaces during each circuit interrupting operation.

'7. In a circuit interrupter for use with circuits subjected to overloads of widely varying magnitude; means at least partially of insulating material for defining the outer surface of a substantially cylindricalarc passage; 'at least a portion of said outer surface being formed of a s lid material which is capable of evolving an arc extinguishing gas when placed in proximity to an electric arc; means also at least partially of insulating material and which has a substantially cylindrical outer surface disposed within and substantially concentric with said passageway, at least during each arc extinguishing operation of said interrupter, for defining the inner surface of said arc passage; said passage being open at one end at least during the circuit interrupting operation; but otherwise completely closed, and means for establishing the arc incident to each opening operation of said interrupter within said arc passage; the arrangement of said outer and said inner surfaces dening means causing said arc passage to have the, substantial form of a hollow cylinder, the cross sectional area of said means positioned within said passageway being so correlated with respect to the cross sectional area of said passageway that arcs of small current magnitude as well as arcs'of large current magnitude are caused to intimately contact said surfaces which define said armpassageY during the operation of said interrupter. g Y

8; In a circuit interrupter; hollow means which is formed at least partially of insulating material for defining the walls and the outer surface of an arc passage having a length at least several times its greatest width; rod means which is also at least partially of insulating material positioned within said hollow wall defining means, at least during each opening operation of said interrupter for defining the inner surface.

of said arc passage; said outer and said inner surface defining means being so formed that said arc passage has the substantial form of afhollow prism completely closed on its sides; and means for establishing the arc incident to each circuit opening operation of said interrupter within said arc passage; at least a portion of said surface defining means being formed of a material which iscapable of evolving an arc extinguishing gas when placed in proximity to an electric arc; the physical dimensions of said rod means lbeing so alessio correlated with respect to the physical dimensions of said Wall defining means that arcs of small current magnitude as well as arcs of large current magnitude are caused to intimately contact the surfaces defining said arc passage.

9. In an expulsion fuse; means of insulating material for defining the walls of and the outer surface of an arc passage having a length which is at least several times its greatest width; means for closing one end of said arc passage, at least during each circuit opening operation, the other end of said arc passage being open, at least during each circuit opening operation; rod means of insulating material positioned within said arc passage, at least during each circuit opening operation, fordefining the inner surface thereof; and fusible means for establishing the arc incident to each opening operation of said fuse within said arc passage; the opposed surfaces which define said arc passage being completely closed and at least a portion thereof being formed of a material which is capable of evolving an arc extinguishing gas when placed in proximity to an electric arc; the physical dimensions of said rod means being so correlated with respect to said wall defining means that said arc passage has the substantial form of a hollow prism, the thickness of which is such that arcs of small current magnitude as well as arcs of large current magnitude are caused to intimately contact the opposed, defining surfaces thereof.

10. In an expulsion fuse; means of insulating material for defining the walls of a substantially cylindrical passageway; means for closing one end of said passage, at least during each circuit opening operation, the other end of said passage being open, at least during each circuit opening operation; a substantially cylindrical rod adapted to be disposed within and substantially concentric with said passageway, at least during each opening operation of said fuse for defining the inner surface of a space wherein the arc incident to the opening operation of said fuse is established; and means including a fusible element for establishing said arc within said space; the opposed surfaces which define the space wherein said arc is established being completely` closed and at least a portion thereof being formed of a material which is capable of evolving an arc extinguishing gas when placed in proximity to an electric arc; the cross sectional area of said rod means being so correlated with respect to the cross sectional area of said cylindrical passage formed within said wall dening means that arcs of small current magnitude as well as. arcs of large current magnitude are caused to intimately contact said opposed surfaces during the operation of said fuse.

11. In a circuit interrupter, means at least partially of insulating material for defining the outer surface of an arc passage, means for closing one end of said passage, the other end of said passage being open at least during each circuit opening operation, means at least partially of insulating material positioned within said passage at least during each circuit interrupting operation for defining the inner surface current magnitudeas well asV arcs of -large current magnitude are caused to intimately contact the surfaces dening the arc passage during the circuit interrupting operation, said passage having a generally annular cross-section to enable lateral movement of the arc therearound.

l2. In a circuit interrupter, means at least partially of insulating material for defining the walls of a tubular arc passage, said passage being completely closed along itslsides and open at one end at least during the circuit interrupting operation, means for establishing an arc longitudinally of said passage, said passage having a generally annular cross-section to enable lateral movement of the arc therearound, said wall defining means restricting the volume of said passage so that arcs of small current magnitude as well as arcs of larg'e current magnitude are caused to intimately contact the surfaces delining said arc passage during each circuit interrupting operation. A

13. In a circuit interrupter, means at least partially of insulating material for defining the walls of a tubular arc passage, the walls defining said passage being completely closed and having at least a portion thereof lined with a material which gives off a gas when acted upon by an arc to aid in extinguishing the arc, means for venting said passage, means for establishing an arc longitudinally of said passage, said passage having a generally annular cross-section to enable lateral movement of the are therearound, the width of said passage being restricted so that arcs of small current magnitude as well as arcs of large current magnitude are caused to intimately contact the walls defining said arc passage during each circuit interrupting operation.

14. In a circuit interrupter, means at least partially of insulating material for defining the outer surface of an arc passage, means for clos- `ing one end of said passage, the other end of said passage being open at least during each circuit opening operation, means at least partially of insulating material positioned within said passage at least during each circuit interruption for defining the inner surface of said arc passage, means for holding said last-named means against lateral deflection within said passage and means for establishing an arc between said inner and said outer surface, said surface defining means so restricting the volume of said passage that arcs of small current magnitude as well as arcs of large current magnitude are caused to intimately contact the surfaces defining the arc passage during the circuit interrupting operation.

15. In a circuit interrupter, a tubular member at least partially of insulating material for defining the outer surface of an arc passage, means for closing one end of said passage, the other end of said passage being open at least during each circuit opening operation, a cylindrical member at least partially of insulating material positioned within said passage for dening the inner surface thereof, means disposed between said tubular member and said cylindrical member for holding the latter against lateral displacement and means for establishing an arc longitudinally of said passage, said passage having a generally annular cross-section to enable lateral movement of the arc therearound.

16. In a circuit interrupter, a tubular member at least partially of insulating material for delining the outer surface of anarc passage, means for closing one end of said passage, the other v end of said passage being open at least during each circuit opening operation, a cylindrical member at least partially of insulating material positioned within said passage for defining the inner surface thereof, spacing means disposed between said tubular member and said cylindrical member intermediate the. ends thereof for preventing lateral movement of said cylindrical member within s aid passage, and fusible means for establishing an arc longitudinal of said passage, said passage having a generally annular cross-section to enable lateral movement of the are therearound, the width of said passage being restricted so that the arcs of small current magnitude as well as arcs of large current magnitude are caused to intimately contact the walls defining said arc passage during each circuit interrupting operation.

17. An expulsion fuse comprising a hollow tube of insulating material, conducting terminals affixed to said tube adjacent the ends thereof, a cylindrical element of insulating material having an outside diameter less than the inside diameter of said tube supported between said terminals Within said tube, spacing members disposed between said tube and said element intermediate the ends thereof for holding said element against lateral displacement within the tube and a fusible link within said tube connected at its ends to said conducting terminals, said tube being closed at one end and having vent openings at the other end to permit the expulsion of the products of decomposition resulting from the operation of said fusible link.

18. An expulsion fuse comprising a hollow tube of insulating material, terminal members releasably attached to the respective ends of said tube, a cylindrical element of insulating material having an outside diameter less than the inside diameter of said tube disposed within the tube and supported between said terminal members to provide an arc passage of generally annular crosssection, support members disposed between said tube and said cylindrical element intermediate their ends for holding said element against lateral displacement within said tube and a fusible ele,- ment within said tube connected between said terminal members for establishing an arc within said passage, said passage being closed at one end by one of said terminal members and vented at the other end through openings in the other of said terminal members.

19. In a circuit interrupter, a tubular member at least partially of insulating material for defining the outer surface of an arc passage, means for closing one end of said passage, the other end of said passage being open at least during each circuit opening operation, a cylindrical member of compressed boric acid positioned within said passage for defining the inner surface thereof, and means for establishing an arc longitudinally of said passage, said wall defining means restrictlng the volume of said passage so that arcs of small current magnitude as well as arcs of large current magnitude are caused to intimately contact the surfaces defining said arc passage during each circuit interrupting operation.

CLINTON L. DENAULT.

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