US2293513A

US2293513A - Electric air circuit breaker

Info

Publication number: US2293513A
Application number: US298946A
Authority: US
Inventors: Leonard J Linde
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1939-10-11
Filing date: 1939-10-11
Publication date: 1942-08-18
Anticipated expiration: 1959-08-18
Also published as: GB550819A; FR52381E; FR52067E; GB541612A; BE447160A; BE449237A; DE740646C; GB545868A; BE446034A; DE767738C; FR877644A; FR52103E; FR867464A; DE969869C; GB549540A; DE762739C

Description

W- 1942- L. J. LINDE 2,293,513

ELECTRIC AIR CIRCUIT BREAKER Filed Oct. 11, 1939 Fig.1. 7

lo a 0 o 00 4 20 Inventor: Leonard J. Uncle,

His Attorney.

Patented Aug. 18, 1942 ELECTRIC AIR CIRCUIT BREAKER Leonard J. Linde, Drexel Hill, Pa., assignor to General Electric Company, a corporation of New York Application October 11, 1939, Serial No. 298,946

6 Claims.

My invention relates to electric air circuit breakers, more particularly to air circuit breakers of the magnetic blowout type wherein a high current power arc is forced or directed into arc extinguishing structure, and has for its principal object the provision of an improved air circuit breaker that is capable of quickly interrupting a high voltage power circuit that may be characterized by a high rate of increase of the recovery voltage with minimum system disturbance and without re-establishing of arcing. A further object is the provision of an improved air circuit breaker that has high current interrupting capacity and that is etficient, positive and consistent in operation.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view, partly in section of an air circuit breaker embodying the present invention adapted for a well-known form of metal clad switchgear; Fig. 2 is an enlarged view, partly in section, of the arc extinguishing structure shown in Fig. 1; Fig. 3 is an end view of the arc extinguishing structure shown in Fig. 2; Fig. 4 is another end view of the arc extinguishing structure taken along the line 44 of Fig. 2; Fig. 5 is an exploded view showing details of the arc extinguishing structure of Figs. 2 and 3; Fig. 6 is a view taken along the line 6-6 of Fig. 2, and Fig. 7 is a top view, partly broken away, of the main housing for the arc extinguishing structure.

The air circuit breaker illustrated by Fig. 1 is in a form that is particularly adaptable for central stations and sub-stations wherein the circuit breaker unit can be bodily disconnected with respect to the stationary circuits by a simple plugging operation. That is, in the present instance the circuit breaker is of the well-known dropdown type wherein disconnection is effected merely by bodily lowering of the circuit breaker. More specifically, the arrangement comprises a main supporting frame I for the movable contact structure which comprises a fixed contact 2 and a relatively movable contact 3 that is pivotally mounted at 4 on one of the circuit breaker studs and is operated by means of a reciprocally movable rod 5. The operating rod 5is suitably con- .nected to an actuating mechanism 6 carried by the frame I that may be, as indicated, of the sclenoid type. The contacts 2 and 3 are electrically connected to the lower ends of the conductor studs 1 and 8 respectively which also serve as plug type disconnecting contacts for the breaker unit. Accordingly, when the contacts 2 and 3 are connected in a power circuit and are separated, an arc may form across the gap indicated.

For the purpose of interrupting this power are, an arc extinguishing structure generally indicated at 9 is mounted in the frame I so as directly to receive the power are which is under the influence of the magnetic fields produced by the blowout coils l0 and H. In the arrangement so far described, the arc extinguishing structure is similar to a conventional arc chute wherein the arc is formed at a narrow entrance part of the chute and is rapidly extended in the form of a loop through the chute.

Referring more particularly to Figs. 2 and 4, the arc extinguishing structure comprises spaced side Walls l2 and I3 composed of arc resisting material, such as asbestos board, each side wall having on the side facing the other wall a plurality of parallel fins l2 and 13' respectively as best shown by Fig. 4. The fins l2 and I3 are preferably integral with the side walls which are Joined and suitably clamped together at the ends I! and IS. The length and spacing of the fins l2 and I3 are such that when the side walls I2 and I3 are clamped together, the fins are spaced and interleaved with respect to each other, i. e. in staggered relation, so as to form a sinuous or zigzag passage l6 into which the arc is driven at the entrance I! of the chute-like structure 9. As shown by Fig. 2, which illustrates but half the extinguishing structure, namely the side wall l3, the fins extend in a direction transverse to the direction of the movement of the are as it passes from the entrance I1 into the chute.

Referring more particularly to Fig. 6 which shows a transverse section of the zigzag arc passage defined by the fins i2 and IS, the fins are shown as tapered toward the entrance of the chute. The tapering edge is preferably defined .-by a curvilinear contour as illustrated so that the angle alpha" defined by the intersection of the curved edges is acute and not appreciably in excess of 20. The angle alpha is but diagrammatically indicated in Fig. 6 and it should be clearly understood that the angle is measured substantially at or immediately beyond the indicated intersection of the fin edges. I have found that this angle should be very sharp, for

example less than 20, in order that the arc suppressing fins be most effective in lengthening,

attenuating and cooling the arc. However, angles between 20 and 30 can be used although to less advantage.

As the arc is driven by the magnetic blowout field into the entrance passage ll of the are extinguishing structure, there is comparatively little transverse deflection of the arc stream during this initial movement. The narrow tapered edges of the fins l2 and I3", while not traversing the are at this stage, nevertheless have a cooling effect along the edges of the are. As the arc is driven further into the space defined by angle alpha in Fig. 6, the cross-section of the arc is reduced to a certain extent and the arc starts to assume a wavy form. If the arc is not interrupted at this point, the blowout field continues to move the arc outward through the arc passage, thereby progressively lengthening the path of the are as the amplitude of the zigzag path becomes greater. The are is thereby greatly lengthened and attenuated concurrent'with material cooling .thereof due to the large cooling surface of the fins near the exhaust part of the extinguishing structure.

As previously indicated, the switch contacts and the magnetic blowout structures can assume any preferred form and constitute no part of the present invention. In the arrangement specifically illustrated, referring to Fig. 2, the magnetic blowout coils ID are electrically connected to the conductor stud l and to the arc runner I so that the arc current traverses the blowout coils in a manner well-known in the art. Normally the current is carried in the closed circuit position of the breaker by the spring biased contact 2', the current being shunted to the arcing contact 2 upon opening of the breaker. As the arc is drawn by the movable contact 3, it is transferred to the arc runner N (Fig. 2) when the contact passes the position indicated by Fig. 1 so that the blowout coil H, which is electrically connected at 3 to the conductor stud 8, is now connected in series with the arc current. Accordingly, the blowout coils are energized by the arc current to influence the arc in a well-known manner. For the purpose of utilizing the blowout field to the greatest extent, iron pole pieces l9 are secured along the outer sides of the extinguishing device as illustrated by Fig. 4.

Although the arc extinguishing structure above described is very effective for interrupting both overload and short circuit currents, the arc, along with the ignited gases, may in certain instances be expelled from the exhaust 'end of the interrupter. Since this is generally objectionable in practice even though the arc may be ultimately extinguished, I have provided means for suppressing the are at the chute exhaust and for cooling the highly heated arc gases without creating excessive back pressure which would decrease the interrupting capacity of the breaker.

Thus arc suppressing structure can be incorporated in the side walls l2 and I3 or take the form of a detachable unit 20 illustrated by Figs. 3 and wherein a pair of spaced insulating strips 2| and 22 are clamped with respect to insulating end portions 23 and 24 so as to form an elongated rectangular frame for supporting the arc suppressing means.

Referring particularly to Fig. 5, the insulating ferred form of my invention a plurality of alter-. nately disposed fibre and copper spacing plates or

sheets

25 and 26 respectively. Preferably the copper sheets are corrugated or crimped as illustrated so as to form passages for the arc gases from the chute while at the same time providing maximum cooling surface. The copper sheets 26 correspond in width to that of the-recesses 2| and 22' so as to readily be retained therein and the fibre sheets 25 are notched as at 25' to fit in the slots so as to Werlap or overhang the copper sheets 26 at the exposed edges thereof. This arrangement provides improved insulation for the copper sheets, and results in improved performance, particularly in the case of high voltage power arcs. As illustrated by Fig. 5, the fibre and copper sheets can simply be stacked between the insulating side walls 2| and 22, no additional spacing members being necessary by reason of the corrugated or crimped form of the copper sheets.

The unit 20, which also functions as a muffler as well as an arc suppressor, cooperates with the arc chute in different ways so that, the interrupting capacity of the arc chute is greatly increased. Also the interrupting characteristics are greatly improved. By way of example, I have found that by the addition of my improved arc suppressor, the interrupting ability of the chute in certain tests was increased approximately 50%.

It is believed that my improved arc suppressor functions to supplement the arc chute in interrupting high current arcs in the following manner. In the first place, the closely stacked fibre sheets and their copper spacing elements function as a throttling device at the chute exhaust to prevent too rapid discharge of the explosive arc and its products through the chute body. In other words, upon the drawing of an arc between the separating contacts, the suppressor 20 immediately functions to maintain a cushion of air within the chute body to oppose the free progress of the arc and its products. In this way the whole of the initially cool chute inner surfaces are more efficiently employed in progressively cooling the advancing heat wave (thereby extracting are heat energy) to increase the arcs resistance and thus expedite its decay and extinguishment. This cushioning eifect automatically adjusts itself as in a dashpot, for the greater the surge of this are heat and pressure wave, as during the interruption of very heavy short circuits, the greater becomes the cushioning tending to regulate its advance.

Second, during the interrupting operation, ad-

vanced arc loops or heat wave crests may approach the suppressor 20. In so doing, the overhanging fibre edges of the plates 25 are encountered which, thereupon, emit arc extinguishing gas under the influence of the are heat. Such advance are crests are, therefore, automatically repelled by these localized back pressure areas. In addition, since'the fibre gas so produced is cool compared to the arc gases, the are heat wave' is further cooled and more energy is extracted as it approaches this newly formed cooling agent. In our preferred embodiment shown in Fig. 2 in which the fibre sheets and their spacing copper elements extend across a zone some 2%" deep, it may be assumed that in exceptional cases involving unusual interrupting conditions, the fibre sheets continue to generate gas along their side surfaces to effectively combat the arc although the latter may penetrate somewhat into the suppressor structure.

Third, the throttling action already discussed is also responsible for another beneficial effect in that the increased pressure within the chute causes increased dielectric strength of the gas which accordingly further aids interruption.

It will be understood that this aggregate retardation efiect from throttling and gas emissivity provides a very flexible and self -adjusting agency for controlling arcs throughout a wide range of current values, the essential features being that the arc is regulated in its progress and kept within the chute body where it is most effectively extinguished. Interruption is attended with minimum circuit and physical disturbance, while at the same time the residual arc products are not unduly impeded in passing through the suppressors grid-like structure, during which further cooling of these gases takes place.

I also may use stacked and spaced insulating sheets of non-gaseous emitting material which will also function, in part, like the fibre sheets by providing throttling means alone in order to extend the arcs brief passage through the zigzag chute structure. However, I prefer to use fibre or other gas-emitting sheets by which full advantage is taken both of cushioning and gas emissivity to control and extinguish the are by virtue of the combined cooling and resistance eifect above described.

The specific construction of the suppressor can take different forms in accordance with my invention. For example, a great part of the advantages can be retained and the construction simplified by using a single grid-like structure comprising a unitary plate of fibre, or other suitable insulating material, that is slotted or perforated to give the throttling or repelling action described. The slots in eifect would define thin individual grid members which may extend either transversely or longitudinally of .the chute exhaust opening.

The spacing between the stacked gas-emitting sheets may also be varied to suit particular conditions. By way of example, I have found that closer spacing toward the center portion of my suppressor to be advantageous in repelling the advance arc loops, which in some cases, tend to ocour in this region.

As indicated by Fig. 2, the arc suppressing unit of Fig. 3 can readily be secured to the exhaust part of the main extinguishing structure, such as by securing the insulating strips 2| and 22 to the outer sides of the chute as indicated at 21. In order more completely to house the interrupting device and to guard against injuries due to possible ejection of hot gases, an insulating casing 28 can be mounted on the frame I. As shown, the casing 28 is provided at the exhaust end of the chute with a detachable insulating cover member 29 coacting with a wedge shaped insulating deflector member 30 for diverting the heated arc gases into opposite sides of the casing 28. A portion of the wedge is secured to the cover 29 and the tapered part 30' is mounted in the unit 20.

For the purpose of facilitating further deflection of the are gases the cover 29 is provided with an insulating deflector 3|, as best illustrated by Fig. '7 which shows a portion of a three-phase breaker, a single arc extinguishing unit being indicated at 9. This arrangement divides the gas exhaust substantially equally and deflects the two streams of gas backward along the outer walls of the extinguishing device. The gas so cooled and deflected can now fiow harmlessly through the grills 32 at opposite sides of the casing 28 as shown by Figs. 2 and 7. The gas deflecting and dissipating arrangement above referred to comprises no part of the present invention and is specifically disclosed and claimed in a copending application Serial No. 298,925, filed concurrently herewith by E. W. Boehne for Electric air circuit breaker.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departingv from the spirit of my invention.

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

1. An electric air circuit breaker comprising relatively movable contacts between which a power arc may be formed upon opening of the circuit, an arc extinguishing structure into which said arc is driven comprising spaced insulating side walls, each wall. having extending from its side facing the other wall a plurality of fins extending in spaced relation longitudinally in a direction generally transversely of said arc, portions of said fins being interleaved and overlapped with respect to each other so as to form a narrow zigzag arc passage between the spaced overlapped fins, said fins being tapered in height toward the arc entrance of said extinguishing structure so as to define between overlapping edges of interleaving fins at the apparent point of intersection a sharp acute arc-entrance angle of 20 or less.

2. An electric air circuit breaker including relatively movable contacts between which a power are may be formed upon opening of the circuit and are extinguishing structure for receiving said are comprising a chute having spaced insulating side walls, are cooling and suppressing means disposed in the space between said side walls, and additional arc suppressing means compactly disposed at the exhaust end of said chute for confining arcing within said chute comprising a plurality of closely spaced alternately disposed insulating and conducting plates.

3. An electric air circuit breaker including relatively movable contacts between which a power arc may be formed upon opening of the circuit and are extinguishing structure forreceiving said are comprising a chute having spaced insulating side walls, arc cooling and suppressing means disposed in the space between said side walls, and additional arc suppressing means compactly disposed at the exhaust end of said chute for confining arcing within said chute comprising a plurality of closely spaced cooling plates including thin corrugated copper sheets.

4. An electric air circuit breaker including relatively movable contacts between which a power arc may be formed upon opening of the circuit and are extinguishing structure for receiving said are comprising a chute having spaced insulating side walls, and are suppressing means disposed at the exhaust end of said chute comprising a plurality of closely spaced cooling members including alternately disposed fibre and deformed copper sheets, said fibre sheets overhanging the exposed edgcs of said copper sheets.

5. An electric air circuit breaker including relatively movable contacts between which a power arc may be formed upon opening of the circuit and an insulating chute for receiving said arc, arc cooling and suppressing means disposed within said chute including interleaving fins arranged to form a zigzag passage for the arc path wall a. plurality of ridges extending longitudinally in the general direction of movement of said arc through said chute, ridges of one wall being closely adjacent to, overlapping and staggered with respect to ridges of the opposite wall so that the arc in passing through said chute is forced to take a tortuous closely confined path around the outer edges of said ridges to increase the length of and attenuate said arc, said ridges being tapered in height toward the arc entrance of said chute so as to define between overlapping ridges of opposite walls at the apparent point of intersection a sharp acute arc-entrance angle of 20" or less.

LEONARD J. LINDE.