US2590524A - Circuit interrupter - Google Patents

Description

March 25, 1952 A. w. EDWARDS CIRCUIT INTERRUPTER Filed sept. 29, 1949 INVENTOR Andrew W. Edwards. 48 BY '06 6i i! ATTORNEY WITNESSES:

Patented Mar. 25, 1952 CIRCUIT INTERRUPTER Andrew W. Edwards, East McKeesport, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Appcationseptember 29, 1949, serial No. 118,500

l 14 Claims.

This invention relates generally to electric circuit interrupters, and more particularly to such interrupters of the type having means for elongating the arc during a circuit interrupting operation.

inasmuch as a circuit interrupter may be called upon to interrupt currents which vary widely in magnitude, it has been the practice in interrupter design to effect some compromise in their construction in regard to ability to interrupt are given magnitude of current, because the most eicient design for a given current magnitude is quite different from that for another current magnitude. Such design compromises are dictated by economic considerations as it has been generally thought impractical from a cost standpoint to provide at any given location, an interrupter entirely suited for every possible value of current which might be encountered at that location.

One such design feature which has been the subject of compromise is the speed at which the arc terminals are separated during circuit nterruption. For high current interruption it is` desirable to have a relatively low speed at which the are terminals separate because the rate of energy input to the are is high enough so that the arc will be extinguished at the rst or second current zero, and yet by keeping the arc length short at that time, it is possible to limit the total energy input to the arc and the arc voltage. For the interruption of low currents, however, it is desirable to separate the arc terminals at a high speed because the energy input rate of such arcs is not important, but the arcs. must be quite. long before they can be extinguished.

Accordingly, one object of this invention is to provide a circuit interrupted having means for separating the arc terminals at a speed which varies generally inversely with the magnitude of current being interrupted.

More specically, it is an object of this invention to provide high speed arc terminal separating means for a circuit interrupter, with means for braking separating movement dependent on the magnitude of current being interrupted.

These and other objects of this invention will become more apparent upon consideration ofthe following detailed description of preferred embodiments thereof, when taken in connection with the attached drawing, in which:

Figure 1 is a side elevational view partially in section, showing a fuse embodying this invention;

Fig. 2 is an enlarged longitudinal sectional view of the rell unit for the fuse shown in Fig. 1;

Fig. 3 is a transverse cross-sectional view taken substantially on the line III-III of FigfZ;

Fig. 4 is a transverse cross-sectional view taken through a modified form of fuse rell at substantially the same point that the section of Fig. 3 is taken; and

Fig. 5 is a side elevational View, partially in section. of a circuit breaker embodying this invention.

The circuit interrupter disclosed in Figs. 1 to 4 embodying this invention, is particularly illustrated as comprising afuse of the general type shown in J. M. Wallace Patent No. 2,276,899, issued March 17, 1942, to the same assignee as this invention. This type of fuse, generally, is contained in a weatherproof tube 2 o1 insulating material, such as porcelain or the like, and containing an inner tube 4 also of insulating material, but which need not be weatherproof in character, such, for example, as ber or the like. The inner tube 4 has a top contact cap 6 threadedly mounted on the upper end thereof, with this cap having an integral flange 8 at its inner end, with a washer I0 0f a resilient packing material, such, for example, as rubber or the like, being interposed between flange 8 and the upper end of outer tube 2. A bottom terminal ferrule I2 is threadedly mounted on the lower end of inner tube 4, and a washer I4 of a material similar to washer I0 is interposed between the upper end of ferrule I2 and the lower end of outer tube 2, so that the latter may be clamped between ferrule I2 and top cap 6.

For the purpose of mounting the fuse o'n a line terminal support or the like, bottom terminal ferrule I2 may be provided with a plurality of integral mounting and positioning lugs I6 and I8 (only one of each being shown) for engagement with the line terminal structure. To enable handling of the fuse, the upper terminal cap 6 may have an integral extension 20 for pivotally supporting a hook-eye 22, in which a hook-stick or other operating member may be inserted.

The fuse further includes a renewable fuse unit 24 mounted within the holder structure comprising inner tube 4, outer tube 2, top cap 6 and ferrule I2. The fuse unit 24 has its own supporting tube 26 of insulating material, which may be of fiber or the like, with this tube being filled with a gas evolving `material 28, such, for example, as boric acid. The filling material 28 is retained within tube 26 by a top plug 30 of insulating material, preferably a molded insulating material, which is threaded into the upper end of tube 26, and may have a washer 32 also in position' 3 of a similar insulating material located at the inner side of plug 30. A bottom plug 34 is held in position within the lower end of tube 26 by a bottom contact ferrule 36 which is threaded 0nto the lower end of tube 26. If desired, a washer 38 may be interposed between an internal shoulder provided integral with ferrule 36 and the lower end of refill tube 26. Y

The filler material 28 is provided with a relatively large central bore 40, and with a smaller bore 42 at one side. ends of bores 40 and 42 by means of an oval- Access is had to the upper lrenewable fuse unit, and then through this rod, iiexible strip 50, fusible material 52, flexible strip 54,"botto'm`contact ferrule 36 to bottom terminal shaped opening 43 providedi-n plug 38, with the lower ends of these bores opening into an outwardly ared bottom outlet portion 544,. whichtion shown in Fig. v2 by a fusible connection tol contact ferrule 36 comprising a strip of' conf ducting material 5 0 secured to the lower end of rod 48, and joined by a mass of fusible Inaterial 52 to a second conducting strip 54 whichv is in turn secured to contact ferrule 36, as by a A strain element 58 alsov connects4 screw 56. the lower end of rod 48 to contact ferrule 36, being also secured to the ferrule by screw 55.

Both strips 50 and 58 are brought together andv secured in a slotprovided in the lower end or rod 48, for example as by solder or the like. Strain element 58 is also of an electrical conducting material, but is of a material having higher resistance than either strips 58 or 54,l

or the fusible material 52. Thus, the main cur-v rent path-between rod 48v and contact ferrule 35 will be that of lowest resistance, comprisingstrip 50, fusible mass 52 and strip 54.

Small bore 42 in ller material 28 contains' one wire 50 secured to the upper end of rod 48,.

as by being looped about a cross-pin 62 passing through the upper end of rod 48, and this wire extends downwardly in bore 42 and overlaps the upper end of a second wire 64 which has its lower end secured between washer 38 and bottom plug 34, by contact ferrule 36. It will thus be observed that-there are two parallel conductingv paths between the upper end of rod 48 and contact ferrule 36, with the lower resistance 4path being through large bore 40.

Renewable fuse unit 24 is adapted to be.mount-. ed in the fuse holder shown in Fig. l by inserte;

ity through the open lower end of the fuse holder until contact ferrule 36 engages an inl tegral internal shoulder 66 on holder terminal. The fuse unit 24 is held at this Aposi- .v tion by a threaded sleeve 68 which is threaded-- errule I2.

into the lower end of holder ferrule I2 to clamp-V contact errule 36 of the fuse unit'against shoul der 66 of ferrule l2.l A head 10 issecured tothe upper end of rod 48 when the fuse unitrZ is mounted in a fuse holder, as shown in-lig.' 1.,: and head 'Hl forms one anchor pointv for al coiled tension spring 12 stressed between head.VV 'i8 and an upper head 14 which has a reduced;

threaded extension extending through a central opening in cap 6 and held in position at the upper end of the holder by a cap nut 76. Head Hi on the upper end of rod 48 for the fuse uniti,

24de vpreferably electrically connectedif he'ai '-ferr'u1e.-l;2of the holder. Accordingly, upon any a'excesscurrentow, fusible material 52 will be melted,.and`since strain element 58 is disposed at an angle, tension spring 'l2 will exert a force component onfusible .material 52 in a direction transversel tothe longitudinal axis of the fuse so that :as-'soon as the fusible material 52 softens,

it will be separated by this force component. The excessA current will then substantially all pass through strain element 58 which will be quickly melted to release rod 48 for movement upwardly through itsbore 48 by spring 12. As rod 48 moves upwardly, it also carries wire 60 upwardly through its bore 42, with the first part of its movement having its lower end in overlapping relationv to the vupper end of wire 64, and finally separating these two wires.

'I'he difference in operation Von high and low currents is due to the fact thatthe circuit is rstbroken by fusion of fusible material 52 and strain element 58, whereupon current now passes to thecircuit through overlapping wires 60 and 64' in the small bore 42. If the current being interrupted is cfa relatively low value, the arc formed upon fusion of wire 6B, or in case these wires are not fused by actual separation thereof, is confinedin small bore 42 where it is most efficiently extinguished due to the fact that it is in closer proximity to the gas-evolving material. However, if the current being interrupted is of a relatively high value, the small wires 60 and 64 will vfuse, and the resulting arc in bore 42 will haVuCh-a Ahigh are voltage due to the small lateral 'dimension of this bore that it will substantially instantaneously transfer to large bore 46 and restrike from the lower end of rod 48 to bottom contact ferrule 36, or any unfused remnants of ` strips 50 and 54 and will eventually be extinguished in this bore 40.'

The present practice in fuses of this type which are employed iny high power circuits employs rela` tively large masses as part of the assembly which must be moved by spring 'l2 in moving rod 48 upw'ardly'in orderto obtain high interrupting ability.""'I he reason for, this practice is that the use voi" such large masses having relatively high inertia c'orres'pondinglyreduces the velocity of upward travel of rod 48 Lduring the early part of its movement after it is released at its lower end.' This 'prevents excessive lengthening of the arc prior to the first current zero, when such highlcurrent arcs are usually extinguished, and

' consequently keeps to a minimum the arc voltage and attendant high energy which may cause V*forces high enough to rupture the fuse holder.

While such provision of slow initial travel of rod 48 vachieves its objective and is thus advantageous for the interruption of high current arcs. it works to disadvantage during interruption of low Acurrent arcs, because the energy input rate ofsuch low-current arcs-is not important, but

Qn the; other hand inward-must. be lengtheeed.

as rapidly as possible to achieve early interruption of the are at an early current zero.

This invention achieves efficient interrupting ability on both high and low currents by introducing a semicircular permanent magnet 80, which may be imbedded in top plug 30 of re'iill unit 24 during the process of molding this plug. It will be observed that due to the particular position of permanent magnet 88, a magnetic .field passes through rod 48. When current iiows through the arcing rod, the reaction between the field produced by this current about conductor 48, with the magnetic iield of magnet 80, causes the rod 48 to move against one side or the other of the opening through washer 32, depending on the direction of current iicw through rod 48. On

high values of alternating current the rod will usually engage but one side of the opening through washer 32 because the arc is usually extinguished at the rst current zero. On lower values of alternating'current the rod may oscillate from side to side of the opening through washer 32 with each reversal of current now. On low currents, the force with which rod 48 engages the side of the opening in washer 32 is not large, so any braking action on upward movement of the rod 48 under the innuence of coil spring 12 is very small. However, on high currents, the force urging the rod against the side of the opening in washer 32 is quite large, and the desired reduction in velocity is thus obtained to enable more eiiicient interruption of such large current arcs. At the same time during inter ruption of lower currents, the movement of rod 48 is substantially unimpeded, and it will move very quickly to thus most eiiiciently extinguish such low current arcs. Depending upon the direction of current iiow through rod 48, the lefthand side of opening 43 in plug 30 may assist Washer 32 in this frictional rubbing engagement. The retarding action on higher currents is due to the friction between rod 48 and the material of plug 30 and washer 32, and this retarding action may be enhanced by the use of a friction brake material in the manufacture of plug 30 and washer 32, such, for example, as asbestos brake lining material commonly used on automobile brake shoes.

Even higher retarding frictional forces on high currents .during movement of rod 48 may be obtained by employing an inductively operated electromagnet in place of the permanent magnet 80, and such a modification is shown in Fig. 4 of thedrawing. This figure shows a plug |06 which may be of an insulating material like plug 30, and having imbedded therein a semicircular bar |08 .of magnetic material, such, for example, as soft iron or the like. A conductor yis also preferably imbedded in the material of plug |06, and comprises one or more turns about the central axis of the fuse, with a number of turns in a closedcircuit about magnetic bar |08, as shown at ||2. The operation of the electromagnetic braking means shown in Fig. 4 is exactly the same as that of the permanent magnet shown in Figs. 2 and 3, except that much higher braking forces can be obtained as the value of current being interrupted increases due to the stronger magnetic field, as well as the higher current through such field.

The invention is illustrated in Fig. of the drawing as applied to a circuit breaker which has a supporting tube 82 of an insulating material, such as fiber or the like, with an upper terminal ferrule 84 secured to the upper end of tube 82,

and a lower terminal cap 86 threaded on the lower end of tube 82. Supporting tube 82 of the circuit breaker may be filled with an arc extinguishing material, such as the material 28 shown in Fig. 2, and this material may be in the form of blocks 88 stacked inside tube 82, with each block having a central opening forming a substantially central bore 89. A contact rod 90 is adapted in the closed position of the circuit breaker to extend through bore 89 With the upper end thereof being engaged at opposite sides by contact fingers 92 mounted in upper terminal ferrule 84. The lower end of contact rod 90 is provided with a head 94 secured thereto, with the head being electrically connected to bottom terminal cap 86 by a flexible conductor 96. A coil compression spring 95 is located between head 94 of contact rod 90 and bottom terminal cap 86 to bias the rod downwardly for circuit opening movement.

Contact rod 90 is adapted to be held at the closed circuit position shown in Fig. 5 with spring 95 in compressed condition by a latch lever 98 having a latching portion adapted to engage head 94. Latch lever 98 is preferably in the form of a bell crank lever having an armature portion |82 located beneath a solenoid coil |04. Latch lever 98 is preferably pivotally mounted at an intermediate point on a bracket secured to lower terminal cap 88, as at |00.

In the closed circuit position of the circuit breaker shown in Fig. 5, the circuit extends from terminal ferrule 84 at the top of the breaker through contact fingers 92 to contact rod 90, and then by way of flexible conductor 96 to bottom terminal cap 86. Solenoid coil |04 may be connected in series in the same circuit, or it may be energized from another source, but in any case when it is energized sufficiently to attract armature |02, latch 98 will be released to thus release contact rod 90 for movement by spring 95 downwardly, to draw an arc between the upper end of the rod and ferrule 84 and rapidly elongate such arc through bore 89 in the arc extinguishing material.

In order that most eiiicient arc extinguishing action may be had in interrupting currents of low value as well as currents of high value, it

will be observed that a plug ||4 is provided in' tube 82 at the bottom thereof, preferably constructed of a molded insulating material similar to the material employed for plug 30 in the embodiment of the invention shown in Fig. 2, and having a semicircular bar H6 of magnetic material, which is permanently magnetized in a manner similar to the permanent magnet referred to in connection with the embodiment of the invention shown in Fig. 2. The permanent magnet ||6 will thus operate to retard movement of contact rod during interruption of high current arcs, and will have substantially no retarding effect on contact rod 90 during interruption of low currents substantially in the same manner as permanent magnet 80 described above in connection with the form of invention illustrated in Figs. 1, 2 and`3.

It is believed apparent from the foregoing that this invention provides for most efficient arc extinction irrespective of the current magnitude of the arc, by permitting extremely fast arc lengthening when arcs of relatively low current value are being interrupted, and automatically retarding arc lengthening when arcs of higher current value are being interrupted.

Having described preferred embodiments of the invention in accordance with the `patent statutes, it is desired that the invention be not limited to any particular form of electric circuit interrupter, inasmuch as it is demonstrated that it is applicable to different types` of interrupters, and accordingly it is desired that the invention be interpreted as broadly as possible.

I claim as my invention:

l. An electric circuit interrupter comprising, separable arcing terminals, Ameansfor'striking only a single arc and separating said arcing terminals, a speed retarding device for one of Vsaid arcing terminals, and said speed retarding device including a magneticelemcnt responsive to the magnitude of arc current for determining vthe rate at which said arcing terminals separate.

2. An electric circuit interrupter comprising, separable contacts, means for striking only a single arc and separating said contacts, a speed retarding device for one of said contacts, and said speed retarding device including a magnetic element responsive to the magnitude of arc currentV for determining the rate at which said contacts separate.

3. An electric circuit interrupter comprising, separable arcing terminals normally held adjacent each other, means biasing at least one of said arcing terminals for rapid separation movement, means forV releasing ,said terminals and causing only a single arc to be formed between said terminals, and current responsive braking means including a magnetic element for said one terminal so that its rate of separating movement will vary in accordance with the value oi current in the circuit. f A

4. An electrical circuit interrupter comprising, separable arcing terminals normally held adjacent each other, means biasingrat least one of said arcing terminals for rapid separation movement, frictional braking means located'adjacent said one arcing terminal, said one arcing terminal and braking means being relatively movable into and out of braking engagement, vmeans for releasing said terminals and causing an are to be formed between said terminals, and current responsive means-for causing relative movement of said one arcing terminal andA braking-means into engagement so that separating-movement of said one arcing terminalv will vary in accordance with the value of current in the circuit.

5. An electric circuit interrupter` comprising, separable arcing terminals normally held adjacent each other, means biasing at least one of said arcing terminals for rapid separation movement, frictional braking means located adjacent said one arcing terminal, said one arcing terminal being mounted for movement into and out of engagement with said braking means, means for releasing said terminals and causing an laro to be formed betweensaid terminals, and :current responsive means for causing movement of said one arcing terminal into engagement with said braking means so that separating movement of said one arcing terminal will vary in accordance with 'the value 'of current in the circuit.

6. An electric circuit interrupter comprising, separable arcing terminals normally held radjacent each athen-'means biasing atleast one of saidarcing terminalsfor rapid separation movement,- frictional braking'means located adjacent said oner arcing terminal, said one arcing term'ihal and braking means being yrelatively movableirito and out oi braking engagement, means for releasing 4said--terminals Aand causing an arc toib'el formed' betweensaid terminals; and current responsive electromagnetic means energized by the current in the circuit for causing relative movement of said one arcing terminal and braking means into engagement so that separating movement of said one arcing terminal will vary in accordance with the value of current in the circuit.

7. An electric circuit interrupter comprising, separable arc terminals one of which is at one end of an elongated terminal support which in turn is mounted for generally longitudinal movement toward and away from the other oi said arc terminals and for limited lateral movement, means biasing said movable terminal for rapid separation movement, means for releasing said terminals and causing an arc to be formed be- 'tween said terminals, a frictional brake member positioned adjacent to one side of the path ofv longitudinal movement of said terminal support, means responsive to the current in the circuit for moving said terminal support laterally into engagement With said brake member so that the rate of separating movement of said movable arc terminal will depend on the magnitude of current being interrupted.

8. An electric circuit interrupter comprising, separable arc terminals one or" which is at one end of an elongated terminal support which in turn is mounted for generally longitudinal movement toward and away from the other of said arc terminals and for limited lateral movement,` means biasing said movable arcing terminalfor rapid separation movement, means for releasing said terminals and causing an arc to be formed between said terminals, said terminal support being of electrical conducting material and serving to conduct current to. said movable arcing terminal, a frictional brake member positioned adjacent to one side of the path of longitudinal movement of said terminal support, means producing a` magnetic field passing through said terminal support to cause the latter to be moved laterally into engagement with said brake member with a force determined by the magnitude of current being interrupted.

9.,An electric circuit interrupter comprising, separable arc terminals one of which is 'at one end of an elongated terminal support which" in turn is mounted for generally longitudinal movement toward and away from the other o1" said arc terminals and for limited lateral movement, means biasing said movable arcing terminal for rapid separation movement, means for releasing said terminals and causing an arc to be formed between" said terminals, said terminal support being of electrical conducting material and serving to conduct current'to said movablearcing terminal, a frictional brake member positioned adjacent to one side ofthe path of longitudinal movement of said terminal support, a permanent magnet located so that its magnetic field passes through said terminal support to cause the latter to be moved laterally into engagement with said brake member with a force determined by the magnitude of current being interrupted.

10." An electric circuit interrupter comprising,- separable arc terminals one of which is at one end of an elongated terminal support which inv turn is mounted for generally longitudinalmovement toward and away from the other or said arc terminals and for limited lateral movement, means biasing said movable arcing terminal for rapid separation movement, means for releasingl saidA terminals and causing an arc tobe :formedl between' said terminals, said terminal -support being of electrical conducting material and serving to conduct current to said movable arcing terminal, a frictional brake member positioned adjacent to one side of the .path of longitudinal movement of said terminal support, an electromagnet energized by current iiow in said terminal support and located so that its magnetic iield passes through said terminal support to cause the latter to be moved laterally into engagement with said brake member with a force determined by the magnitude of current being interrupted. t

l1. An electric circuit interrupter including means forming an elongated arc passage of restricted cross-section, at least inner walls of said passage being of a material which evolves an arc extinguishing gas when in proximity to an electric arc, a stationary arc terminal adjacent one end of said are passage, an elongated arc terminal mounted for movement through said are passage, means biasing said movable terminal for movement in a direction away from said stationary terminal to rapidly elongate an arc between said terminals, means normally holding said movable terminal at a position adjacent said stationary terminal, means for releasing said holding means, a brake member positioned adjacent one side of said movable terminal at least during an initial part of its movement under the influence of said biasing means. and means responsive to the magnitude of current flow in the circuit for moving said movable terminal laterally into engagement with said brake member with a force proportional to current magnitude.

l2. A circuit interrupter having a pair of separable arcing terminals between which an arc may be established and lengthened, braking means including a relatively stationary brake part and a movable brake part, one of the separable arcing terminals being movable and causing movement of the movable brake part during the opening operation, means responsive to the magnitude of the arc current for causing a greater interaction between the relatively.; stationary brake part and the movable brake part during high current interruption than during low current interruption, and the braking means thereby acting to reduce the speed of separation between the arcing terminals during high current interruption.v

13. A-.circuit interrupter having a pair of separable arcing terminals between .which an arc may be established and lengthened, braking means including a relatively stationary brake part and a movable brake part, one of the separable arcing terminals being movable and causing movement of the movable brake part during the opening, operation, electromagnetic means responsive to the magnitude of the arc current for causing a greater interaction between the relatively stationary brake part and the movable brake part during high current interruption than during low current interruption, and the braking meansY thereby acting to reduce the Vspeed of separation between the arcing terminals during high current interruption.

1,4. A circuit interrupter having a pair of separableV arcing terminals between which an arc may be established and lengthened, braking means including a relatively stationary brake part and a cooperable frictionally engageable movable brake part, one of the separable arcing terminals being movable and causing movement of the movable brake part during the opening operation, electromagnetic means responsive to the magnitude of the arc current for causing a greater mechanical frictional engagement between the cooperable relatively stationary and movable brake parts during high current interruption than during low current interruption, and the braking means thereby acting to reduce the speed of separation between the arcing terminals during high current interruption.

ANDREW W. EDWARDS.

REFERENCES CITED UNITED STATES PATENTS Name Date Wallace Mar. 17, 1942 Number

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