EP1548773B1 - Arc extinguishing installation for a circuit breaker with a double break - Google Patents

Abstract

A magnetic casing (91) fits around a pre-chamber so as to amplify magnetic blowing action on an electric arc formed between the pre-chamber's first (51) and second (61) electric arc running rails. Inserted into an arc-quenching circuit, a blowing loop runs parallel to an electric arc running rail in sections. An independent claim is also included for a safety switch with a two-way interrupter switch.

Description

TECHNICAL AREA

The present invention relates to the field of power switches for low voltage distribution networks. It relates to an arc quenching device for circuit breaker with double break according to the preamble of claim 1.

STATE OF THE ART

In low-voltage distribution networks, installation circuit-breakers are used to rapidly and reliably protect low-voltage lines, motors, equipment, and equipment from the effects of overload and short-circuit currents. They generally have a thermal release with a bimetal and an electromagnetic release with a coil and a percussion anchor and preferably a contact arrangement with double interruption.

In such switching devices is for the life and switching capacity of crucial importance that the resulting arc when opening the contacts does not remain on the contact pieces, but as fast as possible in a quenching chamber area, where a cooling and extinguishing of the arc takes place. Any persistence of the arc on the contact pieces, even in the millisecond range, leads to increased burnup and wear of the contact pieces.

A normal circuit breaker has a contact point, which is formed of a fixed and a movable contact piece. The contact point is located in a so-called prechamber, to which a quenching chamber with an arc splitter stack connects. The foot points of the arc are passed from the fixed contact piece and the movable contact piece via arc guide rails to the arc splitter stack. The arc widens immediately after the contact opening, and the inlet velocity of the arc in the Arc splitter stack is dependent on the so-called own blowing, ie the generated by the arc itself magnetic blowing field, the pressure conditions in the arc, the shape of the guide rails and the choice of contact material.

From the EP-A 649,155 a generic circuit breaker with double break is known, in which in the arc extinguishing circuit an additional electromagnetic blower loop is provided to accelerate the arc run. This blowing loop, which only carries current during the switch-off process, is symmetrical with respect to a dividing wall which separates two extinguishing chambers and is formed geometrically parallel to the arc guide rails. By a parallel current flow in the blower loop and the adjacent guide rails, the electromagnetic force is amplified on the arc and its movement accelerates, ultimately resulting in a higher switching performance.

In the EP-A 0 212 661 a current limiter is described for medium or high voltage applications, in which an arc between two arc guide rails runs away from a switching point. Due to the special design of the low-inductive guide rails, the resistance in the quenching circuit is significantly increased, so that the quenching circuit can be easily interrupted by a series-connected disconnector. To accelerate the arc motion, the magnetic field generated by the turn-off current itself is amplified by attaching a magnetic core around one of the bus bars.

In the " EP-A-255 016 "An arc quenching device according to the preamble of claim 1 is disclosed.

PRESENTATION OF THE INVENTION

Object of the present invention is to optimize the acceleration of the two generated by a shutdown movement of a switching contact targeted at a circuit breaker with double break. This object is achieved by an arc quenching device having the features of patent claim 1 and a circuit breaker having the features of claim 10. Advantageous embodiments will become apparent from the dependent claims.

The core of the invention is to reinforce by a suitable magnetic jacket, the magnetic fields in the arc and thus acting on the arc and this driving in the direction of the arc splitter Lorentz force. As a result, the arc moves faster, the contact erosion is reduced and the turn-off increased ultimatively. By the inventive separate magnetic jacket need the arc guide itself have no magnetic properties and thus can be made of non-magnetic, the arc movement favoring copper.

Preferably, the magnetic jacket, for example, made of steel is realized by a one-piece, one-sided open U-profile mold is slipped over a bridge-side arc run rail that the arc chamber or the antechamber is completed on three sides by the molding. The magnetic field acting on the arc of the current flowing in the arc run-off current, i. the so-called own blowing, is thereby reinforced. In addition, such a molded part can be easily manufactured and attached to the arc running rail during the assembly process.

In a preferred embodiment of the invention, a blown loop is inserted into a current flow only during the shutdown of the circuit breaker and the two arc arc extinguishing circuit. The latter is arranged in sections parallel to an arc track and is traversed by a current which points in the same direction as the turn-off in the adjacent arc guide. As a result, the magnetic blowing effects of the two streams are accumulated on the arc. The U-shaped magnetic jacket preferably also surrounds or surrounds this running-rail-parallel blow-loop section.

Preferably, the blower loop is geometrically or materially equipped with current-limiting properties. Since the blown loop in nominal operation, i. When the switch contact is closed, no current is supplied, this does not affect the intrinsic impedance of the switch and, due to its low initial or cold resistance of a few mΩ, does not hinder the commutation of the arc to the corresponding arc runners. After the commutation of both arcs, the blown loop is also current-flowed, as a result of which its impedance increases and limits the cut-off current.

In switches with double interruption, the blower loop is formed so that both arcs are favored to a similar extent, for example, by a respect to the extinguishing chamber partition symmetrical design of the blower loop or by two electrically connected in parallel, each associated with an arc blowing loops. In any case, each arc or two atria associated with a separate magnetic sheath, which also serves as a magnetic shield of the arc chamber with respect to the prevailing in the other arcing space magnetic fields.

In a preferred embodiment, the U-shaped magnetic jacket is separated from the actual arc chamber by a prechamber insulation of, for example Plexiglas. This prevents a flashover of the arc on the possibly metallic jacket. In addition, the insulation may have outgassing properties, i. Remove arc-extinguishing gases.

The pre-chamber insulation preferably has a bulge projecting into the arc region for reducing the prechamber volume. The reduced volume counteracts a pressure loss of the gases in the arc region and prevents the arc from broadening. In particular, the foot points of the arc remain compact and thereby heat the arc guide rails, which is conducive to movement of the arc.

The bulge preferably has a V-shaped profile, which opens in the direction of the quenching chamber and approximately follows the contour of the guide rails. This ensures that the two arc-root points move at the same speed and that the arc expands before its entry into the quenching chamber over its maximum length determined by the distance between the arc guide rails. Thus, all quenching plates are equally involved in the division and extinction of the arc.

BRIEF DESCRIPTION OF THE FIGURES

• Fig. 1 eine Lichtbogenlöscheinrichtung umfassend zwei Vorkammern mit je einem magnetischen Mantel und je einer Blasschlaufe,
• Fig.2 eine Detailansicht einer ersten Vorkammer, und
• Fig.3 einen Schnitt durch eine erste Vorkammer mit einer Vorkammerisolation.

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. These show in perspective

• Fig. 1 an arc quenching device comprising two prechambers each having a magnetic jacket and a respective blown loop,
• Fig.2 a detailed view of a first antechamber, and
• Figure 3 a section through a first antechamber with a Vorkammerisolation.

The reference numerals used in the drawings are summarized in the list of reference numerals. Basically, the same parts are provided with the same reference numerals.

WAYS FOR CARRYING OUT THE INVENTION

Fig.1 shows in oblique view a section of a single or multi-pole circuit breaker with two series-connected switching contacts per pole. A first terminal 10 leads via the coil of a short-circuit current release 100 and a first connection conductor 11 to a first fixed contact 21. This is in the closed switch position (not shown) in electrical contact with a first bridge contact 31 of a movable fork-shaped contact bridge 3. A second bridge contact 32 of Contact bridge 3 is in the closed switch position in contact with a second fixed contact 22, which leads via a second connecting conductor 12 on to an overcurrent release, not shown, and to a second terminal. Both switching points formed by a fixed and bridge contact each have a first or second prechamber 41, 42 assigned to it.

If the contact bridge 3 is moved away from the fixed contacts 21, 22 in the short-circuit or overcurrent case by the short-circuit current release 10 or the overcurrent release, two arcs flowing in opposite directions from the cut-off current form between the fixed contacts 21, 22 and the bridge contacts 31, 32, the bridge-side bases in the sequence of the bridge contacts 31,32 on bridge side arc runners 61,62 commute or "jump". Due to the shape of the (in the arrangement Fig.2 "lower") bridge-side arc runners 61,62 and connected to the fixed contacts 21,22 (in the arrangement according to Fig.1 a first arc between the first connection-side arc runner rail 51 and the first bridge-side arc runner 61 moves toward a first arc splitter stack 71, while a second arc travels between the second connection-side arc runner 52 and the second bridge-side arc runner 62 moves toward a second arc splitter stack 72. When switching off the arcs are thus forced by the self-generated magnetic fields along the arc rails in extinguishing chambers, cooled to the quenching plates, divided into partial arcs and deleted.

In Fig.2 In another perspective, a detail of the first pre-chamber 41 is shown, wherein the splitter stack has been omitted between the widened ends of the two first arc guide rails 51,61. The inventive magnetic jacket 91 with U-shaped cross-section, which consists of a magnetically active Material such as iron or steel is preferably prepared as a one-piece shielding plate, is arranged so that it closes the arc space, which is defined between the first arc guide rails 51,61, laterally. A back 911 of the shell is located along the first bridge-side arc guide rail 61, while the side surfaces 912 of the shell extend toward the first connection-side arc guide rail 51. The magnetic jacket 91 bundles the arc magnetic field and drives the arc in the direction of the extinguishing chambers.

How out Fig.1 Furthermore, it can be seen that each of the two prechambers 41, 42 is assigned a separate magnetic jacket 91, 92. As a result, the arc region between the two arc guide rails 51, 61; 52.61 magnetic with respect to the outside space and in particular with respect to the other prechamber 42; 41 shielded. Next is in Fig.1 a first blower loop 81 is provided between the first bridge-side running rail 61 and the second bridge-side running rail 62. In the event of tripping, the cut-off current flows from the first to the second arc through this first blower loop 81. It comprises at least one Lorentz section located inside the jacket 91, which is arranged geometrically parallel to the first bridge-side arc runner 61 and in which the current flow direction is the same as in the adjacent arc runner 61 As a result, the electromagnetic Lorentz force on the first arc, which moves it in the direction of the first splitter stack 71, amplified.

The blower loop 81 is preferably equipped with turn-off current limiting properties. A current-limiting behavior can be achieved, for example, by the selection of materials, all conductors with an electrical resistance in question, which increases with increasing current, and including in particular the known as PTC resistor or positive temperature coefficient (PTC) resistance metallic alloys based on Ni, Co, Fe, such as NiCr, NiMn, NiFe, NiCrMn, NiCo, NiCoFe, CoFe, CrAlFe, or ceramic materials. Another such PTC thermistor is based on a polymer composite whose polymer matrix is filled with a mixture of carbon, a metal such as Ni, and a boride, silicide, oxide or carbide such as TiC ₂ , TiB ₂ , MoSi ₂ , V ₂ O ₃ . It is important that the initial or cold resistance is not too high and the commutation of the Arcs on the bridge-side rails 61,62 and the concomitant training of the arc extinguishing circuit is not hindered.

In Figure 3 a section through the first pre-chamber 41 is shown, whereby from the first magnetic shell 91 only the sectional area of its back 911 is visible. In general, the arc running properties are highly dependent on the contour of the arc guide rails 51,61. Due to the apparent narrowing between the upper and lower guide rail over a large part of the antechamber, the arc is optimally accelerated. Since the magnetic suction effect by the quenching plates 71 of magnetic material is already effective in the widening of the guide rails 51,61, a persistence of the arc is prevented on the arc guide rails and allows instantaneous shrinkage of the same.

Between the guide rails 51,61 and the magnetic jacket 91 is a pre-chamber insulation 411, which has substantially the same cross section as the jacket 91 and this isolated from the arc region. A pre-chamber insulation as an injection molded part is suitably introduced into the jacket or placed over the guide rails prior to assembly of the jacket. An indentation 412 within the prechamber insulation directs the ionized gases onto the guardrails, which are heated by the gases and thus allow the arc root to run. The bulge 412 reduces the distance perpendicular to the cutting plane of the Figure 3 between the side surfaces of the insulation, ie the clear width of the arc chamber, by 30 to 50%. The bulge according to Figure 3 has the shape of an elongated elevation, which opens in a V-like direction towards the splitter stack 71 out.

LIST OF REFERENCE NUMBERS

10

First connection terminal

100

Short circuit current release

11

First connection conductor

12

Second connection conductor

21

First fixed contact

22

Second fixed contact

3

Contact bridge

31

First bridge contact

32

Second bridge contact

41

First antechamber

411

prechamber

412

bulge

42

Second antechamber

51

First connection-side arc runner

52

Second connection-side arc runner

61

First bridge-side arc runner

62

Second bridge-side arc runner

71, 72

Arc splitter packages

81

First blow loop

82

Second blow loop

91

First magnetic coat

911

move

912

side surface

92

Second magnetic coat

Claims (10)

1. Arc-quenching device for circuit breakers having double-break contacts, comprising

   - two fixed contacts (21, 22) which can be connected to connection terminals of the circuit breaker and with which contact can be made by two link contacts (31, 32) of a moveable contact link (3),

   - two prechambers (41, 42), separated by a partition wall, each having two arc guide rails (51, 61; 52, 62), of which a connection-side arc guide rail (51, 52) is connected to a fixed contact (21, 22), and a link-side arc guide rail (61, 62) is formed by the contact link (3) for the purpose of taking over an arc, and

   - two quenching chambers, connected to the prechambers, each having an arc splitter stack (71, 72) which is connected to the respective arc guide rails (51, 61; 52, 62),

   characterized in that a magnetic shield (91) is provided for the purpose of intensifying the magnetic forces acting on a first arc which is formed between the first link-side and the first connection-side arc guide rails (51, 61), and in that this magnetic shield (91) is a shaped part having a rear side (911) and two parallel side faces (912) which form a U-shaped profile, the rear side (911) coming to rest next to the first link-side arc guide rail (61), and the side faces (912) pointing toward the connection-side arc guide rail (51).
2. Arc-quencing device according to Claim 1, characterized in that the shaped part is integral.
3. Arc-quenching device according to Claim 1 or 2, characterized in that a first blowing loop (81), which is connected to the two link-side arc guide rails (61, 62), is provided on the first arc for the purpose of generating a Lorentz force directed toward the first arc splitter stack (71).
4. Arc-quenching device according to Claim 3, characterized in that the magnetic shield (91) surrounds the first link-side arc guide rail (61) and a Lorentz section, which is arranged geometrically parallel thereto, of the blowing loop (81).
5. Arc-quenching device according to Claim 3 or 4, characterized in that the first blowing loop (81) has current-limiting properties.
6. Arc-quenching device according to Claim 3 or 4, characterized in that the two prechambers (41, 42) are shielded from one another by in each case one associated magnetic shield (91, 92).
7. Arc-quenching device according to Claim 2, characterized in that prechamber insulation (411) made of an electrically nonconductive material surrounds the arc region and insulates the arc with respect to the magnetic shield (91).
8. Arc-quenching device according to Claim 7, characterized in that a bulge (412) is provided on at least one of the inner walls of the prechamber insulation (411) which face the arc region.
9. Arc-quenching device according to Claim 8, characterized in that the bulge (412) of the prechamber insulation has a V-shaped structure which opens toward the quenching chambers.
10. Circuit breaker having double-break contacts, comprising two connection terminals (11), a short-circuit current release (100) acting on a contact link (3) and the arc-quenching device according to one of the preceding claims.

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