EP2859570B1 - Switchgear for direct current - Google Patents

Description

The invention relates to a switching device for guiding and separating high DC currents. The switching device comprises a gas-tight encapsulated housing, which is filled with an insulating gas, and at least one contact pair, which is arranged in the housing and having a first contact and a second contact, wherein at least one of the two contacts is movable and the two contacts in an on state of the switching device in contact with each other and in an off state of the switching device are out of contact with each other. Furthermore, the switching device comprises an arc runner arrangement which generates a magnetic field at least in the region of the contact pair.

Such a switching device is for example from the US Pat. No. 5,680,084 known. The housing described therein is filled with a gas mixture comprising hydrogen. There are also known other switches in which one or more contact pairs are provided, which are operated in an air atmosphere. When opening such switches creates a switching arc between the contacts of a contact pair. In AC applications, this switching arc extinguishes between the contacts at the natural zero crossing of the current, thus causing a permanent interruption of the current flow. In particular, at higher currents is generated by means of a magnetic blower field, either externally via a permanent magnet system or via a self-guided in the switch itself current path generated own magnetic field, so that the switching arc is expelled from the contacts and expanded and extinguished due to deionization and cooling. There are also known switches with extinguishing systems, for example in the form of so-called Deion chambers in which by dividing the switching arc into several partial arcs with simultaneous cooling through chamber walls and quenching plates, a rapid increase in the arc voltage, so that it expires at the latest when reaching the driving voltage and thus comes to a permanent interruption of the electric current.

Depending on the energy content of the arc, this results in a different level thermal stress of the contact arrangement, associated with a certain burn on contact material. The switching chamber walls and the extinguishing chambers are also subjected to thermal stress, which results in a limitation of the electrical life of the switching device. The load of the switching device during the switching process is particularly high in the case of high arc performance, especially in the absence or low mobility of the arc, resulting in a relatively high contact erosion and material changes of the switching chamber walls by locally high thermal loads result.

A high thermal load of the switching chambers occurs in particular at high direct currents, which in contrast to comparable alternating currents have no sinusoidal current profile with natural zero crossing and thus have after separation of the switching contacts a consistently high arc performance. To achieve the highest possible life expectancy of a switching device for DC applications, it is therefore essential to minimize the burning time of the switching arc by its rapid cooling and deionization of the switching path. In this case, a rapid increase in the burning voltage is achieved, which leads to the extinction of the arc when reaching the driving voltage.

In the arrangements known for extinguishing direct currents (DC currents), in which the switching arcs are driven via magnetic blowing fields in so-called deion chambers and extinguished there, flashbacks can frequently occur, in particular in the case of high-energy arcs. This occurs in a portion of the switching path, in which the arc no longer acts directly, whereby the electrical conductivity in this area by deionization of the surrounding air has already significantly reduced overall, to a renewed ignition by the arc, associated with a sudden break-in the arc voltage. Repeated flashbacks can significantly increase the overall arc burn time, which in turn increases the thermal load on the switchgear. Circuits with frequent restrikes therefore result in a reduced life expectancy of the switching device.

A very efficient arc quenching can be achieved if instead of normal air as switching environment hydrogen or a hydrogen-containing gas mixture in the form of a hermetically encapsulated housing of the switch selects. It is known that hydrogen molecules cause a very efficient cooling and deionization of the switching path due to significantly higher particle velocity compared to air molecules. As a result, when switching in a hydrogen atmosphere on a free-burning arc, a multiple of the arc voltage achievable with the same switching arrangement in air can be achieved. In practice, this means that you can build a higher arc voltage over a targeted elongation of the switching arc, caused by a magnetic blower field, as by the division of the arc into several partial arcs in the form of a classic arc splitter.

Encapsulated hydrogen-filled switching devices can be found today in several products in the form of compact relays for currents up to several hundred amps realized. Above all, these products are designed to permanently carry currents of this magnitude in the form of very compact arrangements and typically to switch them several thousand times. With these compact switching chambers, however, the achievable switching numbers are limited at high switching capacities by a gradually decreasing insulation capacity of such arrangements. The document DD 37 438 describes a switching device especially for DC operation.

The document EP 1 022 758 A2 shows a switching device in a rotationally symmetric insulator tube.

Object of the present invention is therefore to realize a switch, preferably for high DC currents, which allows for relatively compact dimensions high electrical switching performance at high switching frequency and high total number of switching.

The object is achieved by a switching device according to claim 1. Preferred embodiments will become apparent from the dependent claims
Characterized in that the switching device is filled with an insulating gas, in particular hydrogen or a hydrogen-containing gas mixture, and additionally an extinguishing device is provided, two effective methods for extinguishing the switching arc are combined, so that there is a particularly efficient and rapid deletion of the switching arc. Alone by the hydrogen atmosphere, an efficient extinguishing of the arc is effected. However, by providing an arc quenching device, the switch can also be used for higher currents, since even in cases where the hydrogen atmosphere is insufficient, then the Arc quenching ensures that the arc is safely extinguished. The extinguishing device is made of an electrically non-conductive material and shaped so that the arc is widened meandering. In this case, the extinguishing device may be made of ceramic, for example. Due to the meandering expansion of the arc, the effective arc gap is significantly extended, without having an increased space requirement within the switching device.

The quenching chamber may include a plurality of spaced-apart quenching plates of refractory and electrically non-conductive material, such as e.g. Ceramic, include. This results in a simple structure and a simple production, as is known for example in connection with Deion chambers.

The extinguishing device has an inlet side, from which the arc is directed into the extinguishing device and enters it. At this inlet side of the extinguishing device, the individual extinguishing plates protrude differently, so that when the arc is driven into the extinguishing device, the arc is already widening in a meandering or undulating manner, since the arc moves around the plates and conforms to them. For this purpose, different length extinguishing plates can be provided, wherein alternately shorter and longer extinguishing plates are arranged.

The extinguishing plates may further each have a notch on the inlet side of the extinguishing device, in which the arc is driven into it. The notch may be asymmetrical in this case and / or arranged off-center, so that the lowest point of the notch is arranged off-center. In addition, the notches of adjacent extinguishing plates together can form a groove with an odd course. Thus, the arc is additionally widened meandering transverse to its direction of movement. Thus, a waveform of the arc on the one hand in the direction of movement of the arc by nestling on the extinguishing plates and a waveform transverse to the direction of movement results through the notches. This causes a very efficient extension or expansion of the arc.

The arc runner assembly may include at least two permanent magnets that are arranged outside the housing and generate the magnetic field in the region of the contact pair.

For an effective expansion of the arc and for guiding it in the direction of the extinguishing device, at least one arc guide arrangement is provided, by means of which an arc occurring between the contacts is led to the extinguishing device. The arc guide assembly may include a first baffle and a second baffle, each extending from the contacts in the direction of the at least one quenching device, that increases the distance from each other.

For a first polarity of an arc, a first extinguishing device and for a second polarity of the arc, a second extinguishing device may be provided. Thus, regardless of polarity, safe erasure of the arc is ensured.

The first contact is electrically conductively connected to a fixed electrode and the second contact is electrically conductively connected to a movable electrode.

In this case, each of the electrodes has a guide arrangement of the arc guiding device in the form of a surface widening starting from the respective contact in the direction away from the respective other electrode. In this case, the surface of the electrode can be represented by a separate cup-shaped component.

The movable electrode may be sealed out of the housing via a bellows, wherein a shield plate is provided on the movable electrode, which at least partially surrounds the bellows and protects against thermal influences.

The housing has an insulating tube of electrically insulating material and two covers closing the insulating at its ends, wherein the insulating tube, the cover and the electrodes are rotationally symmetrical to a longitudinal axis of the switching device.

Figur 1

einen Längsschnitt durch ein erfindungsgemäßes Schaltgerät,

Figur 2

eine perspektivische Darstellung des Schaltgeräts gemäß Figur 1 und

Figur 3

eine perspektivische Darstellung einer Löscheinrichtung des Schaltgeräts gemäß Figur 1.

In this case, one of the lids may be integrally formed with the fixed electrode in order to ensure the most efficient heat dissipation from the housing. A preferred embodiment of a switching device according to the invention is explained in more detail with reference to the following drawings. Herein shows

FIG. 1

a longitudinal section through an inventive switching device,

FIG. 2

a perspective view of the switching device according to FIG. 1 and

FIG. 3

a perspective view of a deletion device of the switching device according to FIG. 1 ,

The basic structure of a switching device 1 according to the invention is in the Figures 1 and 2 represented, which will be described together below.

Similar to known vacuum interrupters, the switching device 1 comprises a switching chamber 2 forming a housing 3, which is hermetically sealed to the outside and is designed substantially cylindrical with a fixed electrode 4 at one end face. A movable electrode 5, which is movable in the axial direction relative to a longitudinal axis L of the switching device 1 against the stationary electrode 4, is provided on a second end face remote from the first end face.

On the side of the fixed electrode 4 is a cup-shaped first lid 7, which is connected either as a separate component concentric with the fixed electrode 4, wherein the outer part of the fixed electrode 4 passes through an opening in the lid 7, or as in the FIG. 1 shown, the first cover 7 and the fixed electrode 4 are designed as a unitary component.

The mobility of the movable electrode 5 is achieved via an axially variable-length bellows 6, whose one end face is connected to the movable electrode 5 gas-tight. The other end face of the bellows 6 is also gas-tightly connected to a cup-shaped second lid 9 in such a way that the portion of the movable electrode 5 located outside the housing 3 is passed through a concentric opening 8 on the lid front side.

The ends facing away from the outer electrode sides of the two covers 7, 9 are each gas-tightly connected to an end face of a cylindrical insulating tube 10 made of an electrically insulating material, preferably ceramic. The insulating tube 10 is in this case positioned in the longitudinal direction of the housing 3 so that the inner ends of the two electrodes 4, 5 are located in the interior of the insulating tube 10.

The located in the interior of the housing 3 side of the fixed electrode 4 carries on its front side 11 a first contact 13 and the inside of the housing 3 located side of the movable electrode 5 carries on its front side 12 a second contact 14. Die beiden Kontakte 13, 14 are the same size and together form a contact pair. The contacts 13, 14 are preferably made of a suitably chosen erosion-resistant contact material. The two contacts 13, 14 are in this case firmly connected with their respective electrode 4, 5 via a flat solder connection.

For guiding and erasing the arcing occurring when the two contacts 13, 14 are opened under load, the switching chamber 2 is designed as follows. Two parallel to each other permanent magnets 15, 16, in the middle of which the switching chamber 2 and the housing 3 is located, are arranged outside of the housing 3. The permanent magnets 15, 16 are arranged at the level of the two contacts 13, 14 and generate a magnetic field whose field lines in the region of the contacts 13, 14 are approximately homogeneous, wherein the field lines are parallel to the surface of the contacts 13, 14.

A resulting when opening the contacts 13, 14 arc is due to the force acting in the contact area Lorentz force at a properly selected magnetic field strength rapidly from the surfaces of the contacts 13, 14 away in the direction of the insulating 10 moves. Between the contacts 13, 14 and the insulating tube 10 there are two diametrically opposed extinguishing devices 17, 18, namely a first extinguishing device 17 and a second extinguishing device 18. The extinguishing devices 17, 18 are used for targeted expansion or lengthening of the running in the direction of the insulating tube 10 Arc as soon as it reaches an inlet side 19 of one of the two extinguishing devices 17, 18. The extinguishing devices 17, 18 each comprise a stack arrangement of extinguishing plates 20, 21 of a erosion-resistant insulating material, preferably ceramic, which in analogy to the When switching to air often used Deion extinguishing chambers are fixed in a defined distance from each other in a frame 32, which also consists of insulating material (see FIG. 3 ). The extinguishing devices 17, 18 are aligned with the permanent magnets 15, 16 located outside the switching chamber 2 in such a way that the magnetic field lines perpendicular to the longitudinal axes L1, L2 of the two permanent magnets 15, 16 and perpendicular to a connection plane, which includes both longitudinal axes L1, L2, lie.

In an advantageous embodiment of a quenching devices 17, 18, the stacking arrangement of extinguishing plates 20, 21 of different length, with a shorter extinguishing plate 20 each have a longer extinguishing plate 20 'follows and vice versa, so that the arc facing inlet side 19 of the extinguishing devices 17, 18 a receives zigzag, meandering contour. Unlike a Deionkammer in which the arc divides into a plurality of individual partial arcs whose length corresponds to the distance between adjacent quenching plates, wherein the total arc voltage generated in the Deionkammer results as the sum of the voltages of all partial arches, the arc is when entering a the extinguishing devices 17, 18 are not divided according to the invention, but selectively extended by nestling on the individual extinguishing plates 20, 21 and by the blasfeldbedingte bulge in the space between the extinguishing plates 20, 21. With a stepped plate assembly of the shape just described thus additional elongation of the arc is achieved.

A further reinforcement of the arc bulging can be achieved by notches 22, 23 in the extinguishing plates 20, 21 on the inlet side 19. The indentations 22, 22 'of adjacent extinguishing plates 20, 20' may be offset from one another or formed differently asymmetrically. With a quenching devices 17, designed in this way, significantly higher arc voltages can be achieved in a switching chamber atmosphere composed of hydrogen or a hydrogen-containing gas mixture than in a deion chamber of comparable size operated in air, which as a result greatly shortens the burning time of the electric arc.

In order to achieve optimum arc running behavior in the magnetic blowing field between the contacts 13, 14 and the quenching devices 17, 18, on the one hand the two contacts 13, 14 are chamfered in such a way that the surfaces facing the electrodes 4, 5 larger are as the respective other contact 14, 13 facing surfaces. By this ramp-shaped transition, a continuous migration of the arc from the surfaces of the contacts 13, 14 is favored. Furthermore, a favorable arc running behavior can be achieved by a conical or bell-shaped configuration of the electrode surfaces 24, 25 in the interior of the housing 3. An additional improvement of the arc guide in the direction of the quenching devices 17, 18 can be achieved by a bead 26, 27 or a bead-like elevation of the bell-shaped electrode surfaces 24, 25 of both electrodes 4, 5 in the direction along the connecting plane of the two quenching devices 17, 18. A particularly advantageous embodiment of the arc guide can be achieved in that, as in FIG. 1 represented baffles in the form of starting from the respective contact in the direction away from the other electrode opposite direction widening caps 28, 29 are provided of electrically conductive material. The caps 28, 29 also each form one of the beads 26, 27. The caps 28, 29 are separate components, which consist of a erosion-resistant material and in full length to the conical or bell-shaped surface geometry of the electrodes 4, fifth nestle and form a solid bond with these, for example via a flat solder joint. With such an arrangement, the erosion counteracted by the local melting and evaporation along the arc root points associated with each circuit can be counteracted.

Due to the mirror-symmetrical design of the switching arrangement, a switching chamber is realized, which - embedded in the manner described in the permanent magnetic field - allows a polarity-independent switching, i. Irrespective of the polarity of the current, the electric arc produced when the contacts 13, 14 are opened will always pass through one of the two baffles in the form of the caps 28, 29 into the respectively adjacent extinguishing devices 17, 18 and extinguish there become.

In order to prevent the expansion of the switching arc in the magnetic field of the external permanent magnets in individual cases to the formation of Lichtbogenfußpunkten in the range due to its only small thickness very sensitive bellows 6, which can lead to punctual leaks, which inevitably lead to the total loss of the encapsulated Hydrogen atmosphere and thus leads to failure of the switching device is the bellows 6 in the direction of the switching path protected by a shield plate 30 which surrounds the bellows 6 shell-shaped.

For a hermetically sealed switching arrangement, it is very important in the case of high switching frequencies and arc performance, the heat energy emanating from the arcs efficiently dissipate to the outside to prevent overheating of the switching chamber or the housing interior. This is promoted on the one hand by the massive design of the two electrodes 4, 5 in the field of arc stress. For the same reason, the contacts 13, 14 are not in the height of the switching chamber center, but moved towards the front end of the fixed electrode 4 out. As a result, the distance for the derivation of the arc heat from the switching chamber 2 out is comparatively short. Also favorable for efficient heat removal is a large-area clamping of current conductors to the electrodes 4, 5.

For a rapid cooling of the heated by the arc stress insulating gas inside the housing continues to run around the movable electrode 5 concentric fin system 31, which means a significant increase in surface area of the movable electrode 5, which as well as the fixed electrode 4 is preferably formed as a solid copper electrode, and This provides a correspondingly large convection cooling surface.

In order to realize a hermetically sealed switching arrangement in the manner described, one can in principle follow the same paths as they are common practice in the manufacture of vacuum interrupters. To mention here is, for example, the so-called "pinch-off" method, in which in the first step, first the individual components or assemblies of the switching device mounted and the entire assembly then gas-tight, preferably via solder joints, is closed. Before filling with the desired insulating gas, the atmospheric air must first be completely removed from the housing. This is done via a suction tube preferably made of copper, which is connected to the housing gas-tight at the chamber end to the housing preferably via a solder and which is connected at the other end to a vacuum pump. After reaching the desired vacuum, the housing is filled via an appropriate valve with the insulating gas of the desired pressure. Finally, the chamber is then over a flat Squeezing the suction tube and subsequent separation sealed from the filling gas-tight.

Another advantageous method for filling and hermetically sealing the housing is the so-called "one-shot brazing" method. In this soldering process, the housing is first built completely according to the modular principle and prefixed suitable. Between all surfaces to be soldered solder material is added in a suitable form and amount. Subsequently, the entire assembly is placed in a vacuum brazing furnace where it is evacuated successively in a single furnace process, filled with insulating gas of the desired pressure and finally sealed completely gas-tight at a furnace temperature above the solder melting point.

As a prerequisite for the realization of this "one-shot brazing" method must be chosen on the one hand all suitable components of suitable high temperature resistant gas-tight materials of low outgassing, on the other hand must be ensured by a suitable pre-cleaning of all parts that it during the brazing process to no relevant pollution-related outgassing occurs and continues to be a complete, gas-tight solder wetting of all components to be soldered.

LIST OF REFERENCE NUMBERS

1

switchgear

2

switching chamber

3

casing

4

fixed electrode

5

movable electrode

6

bellow

7

first lid

8th

opening

9

second lid

10

insulating

11

front

12

front

13

first contact

14

second contact

15

permanent magnet

16

permanent magnet

17

first extinguishing device

18

second extinguishing device

19

Inlet side 20, 20 'extinguishing plate

21

extinguishing plate

22

22 'notch

23

notch

24

electrode surface

25

electrode surfaces

26

bead

27

bead

28

cap

29

cap

30

shroud

31

Fin assembly

32

frame

L

longitudinal axis

L1

Longitudinal axis of the first extinguishing device

L2

Longitudinal axis of the second extinguishing device

Claims (11)

1. Switching device (1) suitable for direct current operation comprising a gas-tight encapsulated, electrically insulated housing (3) which is filled with an insulating gas, at least one contact pair (13, 14) arranged in the housing (3) and having a first contact (13) and a second contact (14), wherein at least one of the two contacts (13, 14) is movable and the two contacts (13, 14) are in contact with each other in an activated state of the switching device (1) and are out of contact to each other in a deactivated state of the switching device (1), wherein the first contact (13) is electrically connected to a fixed electrode (4) and the second contact (14) is electrically connected to a movable electrode (5), as well as an arc driver assembly (15, 16) which generates a magnetic field at least in the region of the contact pair (13, 14), wherein an extinguishing device (17, 18) is provided for extinguishing the arc, into which the arc is driven by the arc driver assembly (15, 16), wherein the housing (3) comprises an insulator tube (10) made of an electrically insulating material and two lids (7, 9) closing the insulator tube (10) at its ends, and wherein the insulator tube (10), the lids (7, 9) and the electrodes (4, 5) are configured rotationally symmetrical with respect to a longitudinal axis (L), wherein the extinguishing device (17, 18) is made of an electrically insulating material and is formed such that the arc is expanded in a meander shaped way, wherein at least one arc guide assembly (24, 25) is provided for guiding an arc occurring between the contacts (13, 14) to the extinguishing device (17, 18), wherein each of the electrodes (4, 5) comprises a guide arrangement of the arc guide assembly in the form of a surface which expands, starting from the respective contact (13, 14), in the direction facing away from the respective other electrode.
2. Switching device according to claim 1, characterised in that the extinguishing device (17, 18) comprises a plurality of extinguishing plates (20, 20', 21) made of a heat-resistant and electrically insulating material which are stacked spaced apart from each other.
3. Switching device according to claim 2, characterised in that the extinguishing plates (20, 20', 21) protrude to differing extents on an inlet side (19) of the extinguishing device (17, 18).
4. Switching device according to claim 3, characterised in that alternately shorter (20) and longer (20') extinguishing plates are provided.
5. Switching device according to any of claims 2 to 4, characterised in that the extinguishing plates (20, 20', 21) each comprise an indent (22, 22', 23) on an inlet side (19) of the extinguishing device (17,18) which is formed asymmetrically and/or arranged eccentrically.
6. Switching device according to claim 5, characterised in that the indents (22, 22', 23) of all extinguishing plates (20, 20', 21) form a groove with a non-straight course.
7. Switching device according to any of the preceding claims, characterised in that the arc driver assembly comprises at least two permanent magnets (15, 16) arranged outside of the housing (3).
8. Switching device according to any of the preceding claims, characterised in that the arc driver assembly comprises a first guide plate (24) and a second guide plate (25) which extend, starting from the contacts, in the direction of the at least one extinguishing device (17, 18) in such a way that the distance to each other increases.
9. Switching device according to any of the preceding claims, characterised in that a first extinguishing device (17) is provided for a first polarity of an arc and a second extinguishing device (18) is provided for a second polarity of the arc.
10. Switching device according to any of the preceding claims, characterised in that the movable electrode (5) is guided in a sealed manner out of the housing (3) via a bellows (6), and a shield sheet (30) is provided at the movable electrode (5) which partly surrounds the bellows (6).
11. Switching device according to any of the preceding claims, characterised in that one of the lids (7) is integrally formed with the fixed electrode (4).

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