US2871319A - Circuit interrupter - Google Patents

Description

Jan. 27, 1959 R. c. DICKINSON CIRCUIT INTERRUPTER 2 Sheets-Sheet 1 Filed Oct. 18, 1956 INVENTOR Robert C.Dickinson Fig.|.

WITNESSES- ATTORNEY Patented Jan. 27, 1959 CIRC Ullt INTERRUPTER Robert C. Dickinson, enn Township, Allegheny County, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pin, a corporation of Pennsylvania Application October 18, 1956, Serial No. 616,758

1 Claim. (Cl. 260-444) This invention relates to circuit interrupters in general and, more particularly, to arc-extinguishing structures therefor.

A general object of the invention is to provide an improved circuit interrupter in which the established arc may be more effectivelyv interrupted than in arc-interruptiug structures heretofore employed in the industry.

A more specific object of the present invention is to provide an improved arc chute for effecting the extinction of an established arc, which are chute comprises a plurality of spaced plate portions having a slot configuration such that the heating effect is distributed over a wider area, and hence cooling and are extinction more quickly occurs.

Another object of the invention is to provide an improved arc chute for a magnetic air circuit interrupter of the type in which an established arc is moved laterally into an arc chute, in which a plurality of substantially parallel disposed arc-interrupting passages are provided so that the established arc is encouraged to be divided into two are streams, each of which is subjected to strong and effective arc-extinguishing action.

In magnetic arc interrupters, such as the type set out in United States Patent 2,442,199, issued May 25, 1948, to Robert C. Dickinson and Russell E. Frink, and assigned to the assignee of the instant application, the arc is moved laterally by a magnetic field into inverted V slots in spaced refractory plates. The voltage interrupting ability of a given stack of plates with a given slot configuration and magnetic field strength is greater at low currents than it is at high currents. This means also that, at a given voltage, the current interrupting ability is generally lower than desired for a given overall size of interrupter.

This effect appears to be caused by local temperature conditions in the plate slots at the time of are interruption, or attempted interruption. At high currents the temperature of the refractory material in the immediate vicinity of the arc space will be higher than at low currents and the temperature of the adjacent gases will also be higher. On account of the higher ionization of the air and the lower resistivity of the refractory material at the elevated temperature, the arc space will break down at a lower voltage than at lower current values, which are accompanied by lower temperatures. It is, therefore, a further object of the present invention to provide a means for increasing the current-interrupting ability of a given overall size of arc chute of the spaced plate type.

The advantages of my invention are not limited to the type of arc chute comprising a plurality of spaced plates, spaced apart at their edges and cemented together to form a unitary stack. As will be apparent to those skilled in the art, certain features of the invention are applicable to the interleaving type of arc chute, in which a plurality of plate portions are integrally formed with the opposite side walls of the arc chute. Merely for purposes of illustration is the invention described in connection with a stacked plate type of arc chute, it being understood that the same arrangement of slotted plate portions could be employed in an interleaving fin type of arc chute, as described above.

Yet a further object of the invention is to provide an improved arc chute having a plurality of spaced plate portions, a plurality of which each possesses a doubleslotted construction to encourage arc division.

An ancillary object of the present invention is to provide an improved arc chute for a magnetic air type of interrupter in which each of a plurality of plate portions has a pair of inverted, closed slots, the upper ends of the closed slots being off center, so that a pair of substantially parallel arc chute passages result, each of which is formed by a group of one of the two slots, in each of a plurality of plate portions.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

Figure 1 is a side elevational view, partially in vertical section, of an air-break type of circuit interrupter, embodying the invention and shown in the closed-circuit position;

Fig. 2 is a vertical sectional view taken along the line IIII of Fig. 1, looking in the direction of the arrows;

Fig. 3 is an enlarged plan view of one of the arc-extinguishing plate portions forming the arc-extinguishing structure;

Fig. 4 is an edge view of the plate portion illustrated in Fig. 3; and

Fig. 5 is an enlarged, fragmentary, sectional view taken substantially along the line V-V of Fig. 2, looking in the direction of the arrows.

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference numeral 1 generally designates suitable contact structure which, when separated to the open circuit position, establishes an arc which is moved upwardly into an arc chute, generally designated by the reference numeral 2, as a result of the transverse magnetic field set up by the blowout coil 3 and associated magnet structure 4. A rotatable contact arm 5 carries a conducting bridge 6, which, in the closed-circuit position, as shown in Fig. l, interconnects stationary main contacts 7, 8.

A contact stud 9 carries the current from the stationary main contact 7, thorugh an insulating bushing 10 to the external circuit. The contact stud for the stationary main contact 8 is not shown, but it may be identical to the contact stud 9.

Consequently, in the closed-circuit position of the interrupter, as shown in Fig. 1, the electrical circuit comprises the contact stud 9, stationary main contact 7, conducting bridge 6, stationary main contact 8, to the contact stud therefor, not shown, to the external circuit.

During the opening operation of the interrupter, the contact arm 5 is rotated in a clockwise direction about a pivot pin, not shown, but which is in electrical contact with the stationary main contact 8, to draw an are between the arcing contacts 11, 12 after the separation of conducting bridge 6 from the main contacts 7, 8.

When the arcing contacts 11, 12 separate, the are formed therebetween will expand upwardly because of the loop circuit so that one terminal thereof will be transferred to the arc terminal member 18, and the other are terminal will be transferred to the other are terminal member 1d.

When this occurs, the blowout coil 3 will be put into series circuit and the transverse magnetic field set up thereby between the field pole members 14 (Fig. 2) will move the established arc upwardly along the arc terminal members 18, 19 into the arc chute 2. The electrical circuit now comprises contact stud 9, conductor 20,- blowout coil 3, contact clip 15, are terminal member 18, the arc itself, are terminal member 19, flexible shunt 28, contact arm 5 to the other contact stud, not shown.

The arc chute 2 comprises aninsulating rectangularlyshaped housing member 22 positioned adjacent toan insulating plate 21, the latter serving as a base for the blowout coil 3. Within the housing 22 is placed a plate 24 composed of an insulating material. Two insulating spacer strips 25 space a plate 26, composed of an insulating material, away from the plate 24. The plate 26 may have a plurality of apertures 27 formed therein which facilitate the venting of arc gases therethrough, partic ularly when high currents are to be interrupted. Two more insulating spacer strips 25 space the plate 26 from a plurality of plates 29, forming a unitary plate assembly. The plates 29 are composed preferably of a refractory insulating material, such as a zircon porcelain, which does not give off gas when contacting an arc. The plates 29 have a construction more clearly shown in Figs. 3 and and are separated by pairs of asbestos rope 35.

Above the arc terminal member 19 is a second insulating plate 26, which is spaced by spacer strips 25 from the right-hand plate 29 of the plate assembly. Two additional spacer strips 25 space the right-hand plate 26 from a refractory plate, not shown, which is, in turn, separated from the right-hand end of the housing 22 by a plurality of strips of fish paper. Bolts 33a secure the several strips 25, plate 26 and the housing 22 to the Plate 21. Bolts 34a secure the right-hand plate 26 and its spacer strips 25 and fish paper strips to the housing 22.

The plates 29 and the spacer strips 35 are cemented together in a preliminary process to form a unitary plate assembly which may be bodily placed into the rectangular housing 22. Insulating holding strips 39 are secured by bolts 38 to the opposed inner sides of the housing 22 to prevent the unitary assembly of plates 29 from being forced upwardly out of the housing 22 by the pressure of gas formed during the interrupting operation.

With particular reference to Figs. 3 and 4 of the drawings, which show more clearly the configuration of each of the insulating plates 29, it will be observed that each plate 29 has provided therein a pair of closed slots 30, 31, the upper closed ends of which, respectively 40, 41, are unequal distances from the sides of the plate, as will be apparent from a comparison of the distances D D The intervening plate portion 29a between the two slots 30, 31 of each plate 29 terminates in a relatively sharp splitter portion 29b facing the contacts. Preferably, it is desirable to alternate, or stagger the plates 29 throughout the arc chute 2, so that the narrow leg 42 is first disposed to the right, then to the left, then to the right, etc. As a result, the upper closed ends 40, 41 do not align with each other, as is indicated in Fig. 2. This will form a pair of substantially parallel arc passages 43, 44 extending lengthwise along the arc chute 2, for the reception of the arc.

The manner of interruption of the established arc will now be described. The clockwise rotation of the contact arm 5 will establish an arc between the arcing contacts 11, 12. Because of the loop circuit this are will move upwardly into the arc chute 2, contacting the arc terminal members 18, 19 and thereby inserting the blowout coil 3 into series circuit. The energization of the blowout coil 3 will set up a strong magnetic field within the magnet structure 4 including the field pole members 14. This will effect upward movement of the estab lished arc, in a well known manner, into the arc chute 2. The are will enter one set of slots constituting an arc passage 43, or the other set of slots constituting the arc passage 44, at random.

As the arc moves higher into one set of slots, the progressive restriction in the slots will cause the arc column to become more restricted, and the staggering of the slots, as indicated in Fig. 5, will cause the arc to become gas expansion, to the other set of slots. The voltage and ionization cause a second arc to start in the latter slots, resulting in two arcs being in parallel in the same stack of refractory plates. This condition is illustrated by the parallel arcs 46, 47 in Fig. 5.

Each are 46, 47 carries approximately one-half of the total current, so that the local surface temperatures are considerably lower than if the same total current were in one set of slots. The upper limit of current interrupting ability thus is higher for the double slot construction than for the single slot construction.

From the foregoing description, it will be apparent that there is provided an improved arc-chute construction in which a plurality of double-slotted plates are employed. Preferably, the closed ends of the slots are unequal distances from the side walls of the arc chute, so that a pair of zig-zag arc passages 43, 44, in parallel, are provided along the arc chute 2. As a result, the initially established arc is encouraged to divide into two arcs 46, 47, in parallel, each moving within one of the zigzag arc passages 43, 44, becoming restricted, and finally being extinguished.

It is to be understood, however, that a staggered construction is not absolutely necessary, and the invention includes in its broader aspects a double-slotted plate construction, in which the closed ends of the slots may be an equal distance from the side walls of the arc chute, as will readily be apparent to one skilled in the art. Preferably, however, a staggered construction is employed to obtain in addition to the restriction of the arc column, an additional progressive lengthening of the arc column, as is indicated in Fig. 5.

It will be apparent to one skilled in the art that the practice of the present invention is not confined to stackedplate are extinguishers, in which a stack of separate plates are spaced by asbestos rope and cemented together, as is illustrated in the drawings, but the invention may readily be incorporated into the interleaving-fin type of arc chute, in which the plate portions are integrally formed with a side wall member. Thus one could divide each late 29 along the broken line 50, Fig. 3, dividing it into two separate portions A, B, with the portions A being integrally formed with one arc-chute side wall, whereas the portions B could be integrally formed with the complementary, or opposite side wall. Thus, upon assembly, the portions A, B would meet along the line 50 so that the resulting structure would be indistinguishable from a stacked-plate construction in which separate plates 29 were employed.

From the foregoing description, it will be apparent that the invention encourages the subdivision of an established are into two parallel arc portions, each of which has intensive deionizing action brought to bear thereon. By dividing the are up into two are columns, local heating is considerably reduced, and the cooling ability of the entire plate area is utilized. The current-interrupting ability of the arc chute is consequently increased without any increase in over-all size of the interrupter.

Certain broad aspects of the invention are describedand claimed in United States patent application filed April 7, 1955, Serial Number 499,970, by Russell E. Frink, and assigned to the assignee of the instant application.

Although there has been illustrated and described a specific type of arc-chute construction, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

I claim as my invention:

An air-break magnetic circuit interrupter including contact means for establishing initially a single arc, an arc chute of generally rectangular shape having side wall portions and end wall portions for receiving said single arc and for causing its subsequent subdivision into two, generally parallel disposed arcs, each of said two arcs extending substantially the entire length of said generally rectangularly-shaped arc chute, said are chute including a multiplicity of spaced, parallel disposed insulating plate portions extending generally transversely of said initially established single are, a plurality of said insulating plate portions each having only two spaced, closed tapered slots therein, each tapered, closed slot having a widened portion near to the contact means smoothly tapering to a restricted closed portion more re mote from said contact means for gradual restriction of the arc column as it moves outwardly from the widened to the restricted portion, the intervening plate portion between the two slots of each plate terminating in a relatively sharp splitter portion near to said contact means, the closed ends of the two slots in each plate portion being spaced unequal distances from the side wall portions of the arc chute, the plate portions being disposed in staggered relation so that a pair of generally parallel, zig-zag, arc passages are provided along the entire length of said rectangularly-shaped are chute to accommodate said two generally parallel disposed arcs extending the entire length of the arc chute, and the aforesaid arc-chute plate construction resulting in widespread dissipation of the generated heat of the two arcs throughout a wide surface area of the generally rectangularly-shaped arc chute to effect thereby rapid circuit interruption.

References Cited in the file of this patent UNITED STATES PATENTS

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