EP0217106B1 - Extinguishing device for an all-current power circuit breaker - Google Patents

Abstract

The extinguishing device has ferro-magnetic extinguishing plates (2) in a housing chamber (1), located at a distance next to one another, which are provided in each case on their narrow side facing one contact point (3, 4) with a funnel-shaped V-slot (2a). Transversely in front of the extinguishing plates (2) there are arranged two dielectric material plates (5, 6) which make contact on the end face with tongues (2b, 2c) on both sides of the V-slot (2a) and flank the contact point (3, 4). The individual extinguishing plates (2) are provided with insulating, narrow arc tracks (8) in the centre region of their tongues (2b, 2c) from both outer longitudinal edges (2d) extending up to in each case the V-slot (2a), which arc tracks are designed as comb-like inserts (8) plugged in between the extinguishing plates (2). The lower dielectric material plate (5) covers a permanent magnet (9) and encroaches with a projection (5a) of its end face in front of a groove-shaped end contour (2a'') of the extinguishing plates (2). Above the permanent magnet (9), there is designed the insulating material plate (5) extending from the flat region (5d) flanking the contact point (3, 4) to the extinguishing plates (2) with step-like thickened regions increasing in steps (5b, 5c). The steps (5b, 5c) result in the switching arc (7) running into the V-slot (2a) well at DC currents above about 30 A. Subsequently, the comb-like inserts (8) prevent the partial arcs (7d, 7e) formed running back onto the tongues (2b, 2c) of the extinguishing plates (2) and keep them on the inner contours thereof. <IMAGE>

Description

The invention relates to an extinguishing device for a circuit breaker, in particular an all-current circuit breaker with a stack of a plurality of ferromagnetic quenching plates, spaced apart in a housing chamber, each with a funnel-shaped V-slot forming two protruding tongues on its narrow side facing a contact point are provided, and with two transversely arranged in front of the quenching plates, lying on both sides of the V-slot on the tongues on the front side and flanking the contact point, at least one of which covers a permanent magnet.

The purpose of such a quenching device is to bring the arc into the quenching plate stack as quickly as possible so that it can form base points on all quenching plates. The resulting partial arcs should remain between the extinguishing sheets until the end of their burning time and should not reunite at their edge to form a total or partial arc or be pushed back into the area of origin. Now, with a pure AC switch, all currents in the zero voltage crossing are interrupted with a correspondingly large contact spacing, with a DC switch there is no automatic interruption at a contact point, since smaller currents up to about 60 A with DC voltages of approximately 220 V are to be switched off. In such a case, the magnetic field of the current is not sufficient to draw the arc into the stack of quenching plates. A permanent magnet is therefore required in the arcing chamber.

Furthermore, with DC switches, the arc voltage must exceed the maximum driving voltage in order to interrupt the circuit. The arc burn time the longer the ratio of the arc voltage to the voltage to be driven and the greater the time constant T as the ratio of the self-inductance L to the resistance R of the circuit to be protected. Since the number of quenching plates is fixed for a switch or a certain number of quenching plates is required in order to interrupt the applied voltage, the level of the arc voltage is also approximately fixed, and the first-mentioned ratio can be assumed as a constant value. The second ratio is dependent on the circuit, so that a higher self-inductance causes a correspondingly longer arc burning time in the stack of quenching plates. In this case, partial arcing can occur, particularly when the current intensity decreases at the end of the shutdown to the edges of the extinguishing plates and in the direction of the permanent magnet. It easily burns or the arc flashes over several quenching plate distances. This case is particularly critical with direct current and leads to the failure of the switch. Furthermore, the arc is only surrounded by a little iron on the narrow tongue ends, so that it remains on the inner contours of the V-slot.

An extinguishing device of the type mentioned at the outset is known (DE-0S 33 37 562), in which the extinguishing plates are provided with a step in the tongues on each side of the V-slot. As a result, only the end edges of these gradations abut the insulating material plate covering a permanent magnet, as a result of which a channel-like depression is formed in front of the contour of the extinguishing plate. The insulating plate also covers the end face of the permanent magnet with an angular extension projecting in the direction of the housing wall. This arrangement is particularly useful for extinguishing the switching arc at comparatively low levels Direct currents up to about 30 A are an advantage. Above such a current, however, such measures are not sufficient to safely extinguish the arc in the case of DC cutoffs.

Furthermore, a circuit breaker with an extinguishing device is known (DE-0S 26 16 825), in which at least one of the extinguishing plates is covered with an insulating material and partially covers it. It is thereby achieved that the base point of the arc can only burn on the free area of the quenching plate and the risk of a short-circuiting or bridging of this quenching plate by the arc is reduced. This known quenching device, in which the arc at the end of the V-slot is to be stabilized by an insulating sheath of the entire stack of quenching plates, preferably lying on the outer quenching plates, is suitable for an AC switch. Since only the two outer quenching plates are covered with insulating material, the partial arcs can join together at the edge contours of the inside quenching plates and short-circuit part of the quenching plates. Such a burning of the arc leads to failure of the switch, especially with direct current.

The invention is based, to improve the effectiveness of the above-mentioned quenching device for an all-current circuit breaker in order to obtain a higher DC switching capacity, in particular for direct currents with a high time constant, the task. In this case, it should be possible to classify it with as few changes as possible in the usually existing pure AC switch series, in order to provide a cost-effective supplementary series of miniature circuit breakers for DC or AC power.

To achieve this object, the features mentioned in claim 1 are provided according to the invention. Developments and advantageous embodiments of the invention are the subject of the dependent claims.

Due to the inventive design of arc locks on all quenching plates, for example in the form of two comb-like inserts reaching into the stack of quenching plates on both sides, the return of partial arcs to the tongues of the quenching plates and their stopping there towards the end of the shutdown are definitely excluded. On the other hand, at the start of the shutdown, an arc in the critical current range of approximately 30 to 100 A is effectively conducted via the step-like thickening of the insulating material plate covering the permanent magnet into the V-shaped slot in the stack of quenching sheets. The thickening of the insulating material plate also results in less demagnetization of the permanent magnet in the area important for DC cutoffs in the case of AC short-circuit cutoffs. Thus, in addition to a very good disconnection of different direct currents with a high time constant, there is also a higher alternating current disconnection capacity.

Fig. 1

zeigt schematisch einen Schnitt durch die Löscheinrichtung in Löschblechebene entsprechend der in Fig. 2 eingezeichneten Schnittlinie, während in

Fig. 2

eine Draufsicht der Löscheinrichtung in Funktionsebene des Leitungsschutzschalters vereinfacht dargestellt ist.

Fig. 3

zeigt die Ansicht einer kammartigen Einlage und

Fig. 4

eine Vorderansicht der das Wesen der Erfindung mitbestimmenden Isolierstoffplatte von der Löschblechseite her.

The invention is explained in more detail below with the aid of the drawing.

Fig. 1

schematically shows a section through the extinguishing device in the plane of the fire-extinguishing sheet corresponding to the cutting line drawn in FIG. 2, while in

Fig. 2

a plan view of the extinguishing device is shown in simplified form in the functional level of the circuit breaker.

Fig. 3

shows the view of a comb-like insert and

Fig. 4

a front view of the essence of the invention with determining insulating plate from the quenching plate side.

The extinguishing device shown as a section of a circuit breaker is accommodated in a housing chamber 1 formed from a lower part 1a and an upper part 1b, which is largely filled by a stack of preferably 12 pieces of ferromagnetic quenching plates 2 spaced apart from one another. In the other part of the housing chamber, in the area of a contact point formed by a fixed contact piece 3 and a movable contact piece 4, an insulating plate 5 underneath and an insulating plate 6 above are flanking in front of the extinguishing plates. When lifting the movable contact piece 4 in the direction of the arrow and the subsequent, already shown contact opening occurs with a corresponding current flow, a switching arc 7, flanked by the insulating plates in a manner to be described in more detail can enter the quenching sheet stack.

The quenching plates 2 standing next to each other in a packet, the mutually facing surfaces of which are oriented perpendicular to the level of the insulating material plates and also to the functional level of the circuit breaker, each have a funnel-shaped V-slot 2a at their narrow end edges facing the contact point, which is approximately in the middle of each quenching plate in one Narrowing 2a 'passes. Thus, tongues 2b, 2c remain on both sides of the V-slot, which protrude in the direction of the insulating material plates. The tongues are flush on their outer longitudinal edges 2d with the rest of the fire-extinguishing plate and are therefore in contact with the housing walls of the lower part or upper part with only a slight gap. Likewise, the extinguishing plates with their rear narrow side 2e rest against a partition wall of the housing chamber 1, in which blow-out openings 1c (not shown in detail) are cut out.

Approximately in the middle of the tongues 2b and 2c, short incisions 2b 'and 2c' are provided from the outer longitudinal edges 2d, into each of which a comb-like insert 8 (FIG. 3) made of insulating material as an arc barrier on both sides of the V- Slot 2a is inserted. The two comb-like inserts 8 engage with their teeth 8a between the quenching plates 2 and over the two outer quenching plates and lie firmly against their surfaces, while their comb back 8b runs over the entire stack of quenching plates and holds them together, if necessary. The teeth of the preferably inclined comb-like inserts extend with their free ends to the V-slot 2a and point in the direction of the insulating material plates. With regard to the arrangement of the comb-like inserts in the area of the tongues or the V-slot, reference is expressly made to FIG. 1 for understanding the invention.

From Fig. 1 it can also be seen that the front edges of the quenching plates facing the arc chamber are provided with a gradation 2b '' and 2c '' on both tongues 2b and 2c. As a result, a channel-like depression 2a ″ is formed in particular between the fire-fighting sheet contour below the V-slot and the end face of the lower insulating material plate 5 facing the fire-fighting sheets, which protrudes with an angular projection 5a and covers a permanent magnet 9. The permanent magnet 9 only inserted into the lower part of the housing is completely covered towards the contact point by the insulating material plate 5 and is protected from damage by the arc both on its surface and on its end edges, in particular by the attachment 5a resting on the edge of the fire-extinguishing plate. Similar to the entire insulating material plate 6, the insulating material plate 5 is flat in the area of the contact point, while it has a step-like thickening towards the extinguishing plates on its upper side facing away from the permanent magnet (FIG. 4). This thickening consists of a first step 5b reaching above the opening of the V-slot in front of the larger part of the quenching plates and a second step 5c which is higher than this in the area between the fixed contact piece 3 and the remaining quenching plates. Here, reference is made in particular to FIG. 2. The second stage 5c extends approximately to the middle of the V-slot and lies against the side of an arc discharge horn 3a of the fixed contact piece 3. The resulting switching arc 7 is therefore inevitably raised on its way into the stack of quenching iron with its base point migrating on the arc discharge horn through the second stage 5c up to approximately the central plane of the quenching device. Both stages expediently emerge with a bevel from the flat area 5d of the insulating material plate 5. Since the second stage 5c runs approximately parallel to the arc discharge horn in the plane of FIG. 2, the first stage 5b widens in a funnel shape towards the quenching plates. This improves the entry of the arc into the quenching plate package.

As further components belonging to the extinguishing device and which delimit these serve on their upper side a return potential plate 10 connected to the fixed contact piece 3, which is electrically conductively connected to an input terminal 11 in a manner not shown, and an arc guide plate 12 located at the bottom of the housing chamber. This in parallel Arc guide plate running to an outer extinguishing plate is guided in the region of the arc space in the direction of the movable contact piece 4 for good takeover of its arc base and carries a bimetal 13 as a thermal trigger at its free end 12a. This is via a connecting line 15 connected in series with a connecting terminal 14 and via a flexible line 16 with the movable contact piece 4.

The direction of flow of the direct current is indicated by arrows in FIG. 2 and leads from the connection terminal 11 to the fixed contact piece 3 and further via the movable contact piece 4, the line 16, the bimetal 13 and the line 15 to the other connection terminal 14. Thus, when contacts open, a direct current flows through the switching arc 7, which under the effect of the magnetic field of the permanent magnet 9 shown schematically in FIG. 1, effectively flows into the V-slot even at currents above approximately 30 A via the steps of the lower insulating plate 5 2a of the sheet stack is directed. In particular, due to the central guiding of the arc on the arc discharge horn 3a caused by the step 5c, the latter can enter the narrowing 2a 'of the V-slot in the critical current range from approximately 30 to 100 A via indicated intermediate positions 7a, 7b, 7c. This process is further supported by the larger air gap to the magnet due to the lower insulating material plate thickened in front of the extinguishing plates.

Has the arc run into the narrowing of the V-slot and has partial arcs formed between the quenching plates in accordance with positions 7d, 7e; the arcing voltage that builds up counteracts the driving direct voltage. Especially with longer arc burning times and direct currents of more than 100 A, however, there is a risk that the partial arcs will run back between the surfaces of the quenching plates into the area of origin (indicated by arrows). With the comb-like inserts 8 it is now achieved that these arcs can only run up to position 7f in front of these barriers and cannot reach the tongues 2b or 2c. Here, such arcs would only be surrounded by little iron on the narrow ends of the tongues and would result in them stopping on the inner contours of the V-slot. However, this is excluded by the invention, so that the switching arc of direct currents from about 30 A is safely extinguished in the wider part of the quenching plates.

Smaller direct currents up to about 30 A, however, are drawn due to the gradation 2b '' of the sheet metal tongues over the end face of the insulating plate 5 into the groove-like depression 2a '' and are extinguished there at the tongue ends of the sheet metal outline (item 7c ').

In addition to a high DC cut-off capacity, especially with a large time constant, the quenching device according to the invention also allows a higher AC cut-off capacity. This is achieved insofar as the demagnetization of the permanent magnet 9 takes place in the region important for direct current cutoffs due to the step-like thickening of the lower insulating material plate 5 when the current flows in the opposite direction.

Instead of comb-like inlays, the arc barriers can also be provided by means of appropriate housing webs which grip between the quenching plates or by local insulation directly on the surface of the quenching plates in the zones in which the teeth 8a grip over the tongues 2b or 2c. Adhesive strips, lacquer or corresponding materials can be used for this local insulation.

Claims (9)

1. Quenching equipment for a circuit breaker, in particular for an alternating and direct current circuit breaker, with a stack of several ferromagnetic quenching laminations (2), which are disposed one beside the other at a spacing in a housing chamber and each provided at their narrow side facing a contact place with a funnel-shaped V-slot (2a) forming two projecting tongues, and with two insulating material plates (5), which are arranged transversely in front of the quenching laminations, lie against the end faces of the tongues to both sides of the V-slot and flank the contact place and of which at least one covers a permanent magnet (9), characterised thereby, that the individual quenching laminations (2) are provided with insulating narrow arc movement barriers (8) in about the central region of their tongues (2b, 2c) on their surfaces and from both outer longitudinal edges (2d) each time to the V-slot (2a) in such a manner that the arc return movement of the partial arc ends (7d, 7e) from that respective areal region of the quenching laminations (2), which receives the constriction (2a') at the end of the V-slot (2a), to those parts of the tongues (2b, 2c), which are disposed in front of the arc movement barriers (8), is prevented.
2. Quenching equipment according to claim 1, characterised thereby, that the arc movement barriers are each formed of a respective comblike insert (8) of insulating material, which insert is disposed between the quencing laminations (2) and engages at both sides of the stack and the teeth (8a) of which each fill out a respective gap between the surfaces of the individual tongues (2b, 2c) to the V-slot (2a), wherein the comb spine (8b) is led over those longitudinal edges (2d) of the quencing laminations (2), which are provided with a notch (2b', 2c').
3. Quenching equipment according to claim 1, characterised thereby, that the arc movement barriers are formed by means of narrow housing webs shaped on at the walls of the housing chamber (1) to be projecting therefrom and each time filling out the gap between the tongues (2b, 2c) of the individual quenching laminations (2) to the V-slot (2a).
4. Quenching equipment according to claim 1, characterised thereby, that the arc movement barriers are each formed by limited local insulations on the surfaces of the tongues (2, 2c) by means of adhesive strips, enamel or similar insulating materials.
5. Quenching equipment according to one of the claims 1 to 4, characterised thereby, that an insulating material plate (5), which covers the permanent magnet (9) and protrudes by a projection (5a) to the housing wall of the quenching chamber (1), engages over an end face of the permanent magnet (9) in front of the end face outline of the quenching laminations (2) and the insulating material plate (5) above the permanent magent (9) is formed by a rising staircaselike thickening (5b, 5c) from the planar region (5d), which flanks the contact place (3, 4), to the quenching laminations (2).
6. Quenching equipment according to claim 5, characterised thereby, that the staircaselike thickening rises out of the planar region (5d) with bevelled transition in a first step (5b) before about three quarters of the number of the quenching laminations, which lie further away from an arc-spreading horm (3a) of the fixed contact member (3).
7. Quenching equipment according to one of the claims 5 and 6, characterised thereby, that the staircaselike thickening (5b, 5c) is formed in the region, which is situated behind the arc-spreading horn (3a), before the remaining about quarter of the quenching laminations (2) in a second step (5c), which is higher than the first step (5b) and reaches almost to the centre plane of arc-spreading horn (3a) and thereby also of the V-slot (2a).
8. Quenching equipment according to one of the claims 5 to 7, characterised thereby, that the insulating material plate (5) flanks the fixed contact member (3) laterally by the planar region (5d) and is led by the thickened second step (5c) directly to the arc-spreading horn (3a).
9. Quenching equipment according to one of the claims 5 to 8, characterised thereby, that the second step (5c) of the thickening is led bevelled about parallely to the arc-spreading horn (3a) and the first step (5b) is thereby enlarged in trapezium shape towards the quenching laminations (2).

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