EP3453044B1 - Double-contact switch having vacuum switching chambers - Google Patents

Description

The invention relates to a double-contact switch with vacuum switching chambers and a hybrid switching device with such a double-contact switch.

In the German Offenlegungsschrift DE 10 2013 114 260 A1 describes a double-contact switch with vacuum interrupter chambers, in which the mechanical switching component has a double vacuum interrupter chamber with two contact pairs arranged in the axial direction, which can be actuated independently of one another.

Furthermore, in the DE 10 2013 114 260 A1 describes a hybrid switching device with this double-contact switch, in which a semiconductor switch, based on an IGBT power semiconductor (Insulated Gate Bipolar Transistor), is arranged electrically in parallel with one of the two contact pairs of the double-contact switch. This hybrid switching device is primarily suitable for switching direct currents or low-frequency currents.

With the opening of a first pair of contacts of the double-contact switch, a load current can immediately commutate to the IGBT, where it is led to zero within a few milliseconds. After the load current through the IGBT is equal to zero, the second pair of contacts of the double-contact switch can then be used to create the galvanic isolation in the hybrid switching device.

Ideally, the second pair of contacts (break contacts) responsible for galvanic isolation opens with a certain delay after the opening of the first pair of contacts (commutation contacts). This prevents a vacuum arc from forming there for a short time, ie for the period in which the load current is still being conducted through the IGBT, if the isolating contacts open simultaneously or prematurely. Particularly in the case of high currents, such short-term vacuum arcs after numerous switching operations under load, such as with contactors, mean gradual contact erosion and thus a corresponding reduction in the electrical service life.

Furthermore, mechanical bouncing processes can occur when switching on conventional purely mechanical switching devices as well as hybrid switching devices. If this happens immediately after the second pair of contacts has closed, a vacuum arc may be formed briefly at the moment of rebound due to the load current flowing, which is associated with local melting of the contact material. In the event of subsequent recontacting, there is then in principle the risk of permanent contact welding, as a result of which the property of galvanic isolation is lost for a hybrid switching device, in particular a contactor.

Even with only minor welds, which are often also referred to as "capping", which can easily be broken open again by the drive of a switching device, there is still a risk, especially with contactors, that numerous direct current switching operations under load due to repetitive local melting of contact material on one of the two pairs of contacts, material migration occurs in such a way that a local accumulation of contact material gradually forms on one of the contacts, as a result of which the effective isolating distance is reduced over time. In the long term, this can also mean that the galvanic isolation capability is no longer available.

In the case of double-contact vacuum interrupters in a cylindrical arrangement with movable electrodes on the end faces, as in the case of in 1 illustrated from the DE 10 2013 114 260 A1 known embodiment, it can generally be assumed that the contact pressure forces caused by the pressure difference between vacuum and air are approximately the same for both contact pairs of the interrupter. Since in vacuum switching devices one of the electrodes of the vacuum interrupter is usually connected directly to the mechanical switching drive and the other electrode is permanently connected to the housing of the switching device, the desired time difference when opening the two contact pairs is often so small without additional design measures that with In principle, there is the possibility of welding and also a gradual migration of contact material between the isolating contacts.

In the DE 10 2013 114 260 A1 is a hybrid switching device with the in 1 shown embodiment of a double-contact vacuum tube, in which contact pressure springs with different spring constants are used in order to achieve that during a switch-off process the commutation contacts of a partial switching chamber of the vacuum tube open first, while the body of the vacuum tube is affected by the contact pressure spring with the larger spring constant is initially held in the switch-on position and so that the isolating contacts remain closed. Only when this spring with the larger spring constant relaxes does the contact pressure spring with the smaller spring constant gradually come into play, as a result of which the tubular body is moved in the axial direction until a mechanical stop is reached. During this process of movement of the tube body, the isolating contacts of the right-hand sub-interrupter chamber open with a time delay.

Interrupters with vacuum interrupters, in which bellows connected to movable electrodes are designed differently or can be, are from JP H05 67414 A and DE 10 2010 045901 A known.

The object of the present invention is now to propose a double-contact switch with vacuum interrupters that takes up less space than that from the DE 10 2013 114 260 A1 known solution for opening the contact pairs at different times.

This object is solved by the subject matter of claim 1. Further configurations of the invention are the subject matter of the dependent claims.

One idea underlying the present invention is to propose a compact double-contact switch with vacuum interrupters designed as partial interrupters of an interrupter, which is structurally designed in such a way that when a load current flowing through the switch is switched off, the two contact pairs in the interrupter open with a time offset which is dimensioned at least longer than a typical current flow time through a semiconductor switch connected in parallel to a contact pair. this will According to the invention, this is achieved in that the gas-tight barriers of the areas of the movable electrodes that carry the contacts are designed differently in such a way that the opening of the contacts of the two contact pairs is offset in time or delayed. As a result, the double-contact switch according to the invention is particularly suitable for use in a hybrid switch in which a power semiconductor switch is connected in parallel with the first contact pair that opens first. When the first pair of contacts opens, the power semiconductor switch can be switched through to prevent an arc from forming between the pair of contacts that open first. By blocking the power semiconductor switch while the first pair of contacts is opening, the load current commutated to the power semiconductor switch can be brought to zero, in particular before the second pair of contacts is opened. As a result, the load current can be switched off with almost no arcing. The invention enables a particularly compact configuration of a double-contact switch with vacuum interrupter chambers.

One embodiment of the invention now relates to double-contact switches with a first and a second tubular vacuum interrupter chamber, which are designed as partial interrupter chambers of an interrupter, an electrode which is fixed in the interrupter and is arranged between the first and second vacuum interrupter chamber and has a first electrode which projects into the first vacuum interrupter chamber Fixed contact and a second fixed contact protruding into the second vacuum interrupter chamber, a first electrode which is arranged in the first vacuum interrupter chamber and is movable in the axial direction therein and has a contact-bearing area which is sealed off in a gas-tight manner from the outside of the first vacuum interrupter chamber, one in the second Arranged vacuum interrupter chamber and movable in this in the axial direction second electrode, with a contact-carrying area which is sealed against the outside of the second vacuum interrupter chamber in a gas-tight manner, the gas-tight barrier g of the area of the first electrode carrying the contact is designed so differently from the gas-tight barrier of the area of the second electrode carrying the contact that the opening of the first fixed contact and the contact of the first electrode and the opening of the second fixed contact and the contact of the second electrode occur at different times offset. Through With this construction, the double-contact switch requires relatively little installation space, so that it is particularly suitable for constructing compact switching devices. In addition, the number of parts required for the constructive realization of the staggered contact pair opening is comparatively small, which means that the production costs are lower compared to mechanical construction with several components.

In particular, the gas-tight barrier of the contact-bearing area of the first electrode and the gas-tight barrier of the contact-bearing area of the second electrode are each formed by flexible bellows, in particular metal bellows. Diameter, wall thickness, number of waves and/or rigidity of the bellows can be different, in particular to bring about different forces acting on the contact pairs, which cause the delay in opening the contact pairs in the interrupter.

In order to provide the different forces on the contact pairs, the outer diameters of the bellows can be of different sizes. As a result, the forces acting on the contact pairs due to the vacuum pressure can be set differently, so that the opening of the contact pairs results in a time delay due to the different forces. For example, the radius R ₁ of the bellows of the first vacuum interrupter chamber can be about a quarter smaller than the radius R ₂ of the bellows of the second vacuum interrupter chamber. This allows different forces to be set by a factor of about 1.8, which act on the contact pairs in the interrupter.

Different forces acting on the pairs of contacts can also be realized in that the bellows of the first vacuum interrupter chamber has a greater corrugation number and/or a smaller wall thickness than the bellows of the second vacuum interrupter chamber. This results in a different spring stiffness of the two bellows, which can directly lead to a delayed opening of the contact pairs.

In order to be able to use the double-contact switch in particular as a component in a switching device, the first electrode can be coupled to a switching drive and the second electrode can be connected to a switch housing wall.

For example, the first electrode can be provided with a connection for a switching drive, and the second electrode can be designed in such a way that it can be attached to a switch housing wall, for example by means of a screw connection.

Another embodiment of the invention relates to a hybrid switching device with a first and a second power connection, a double-contact switch according to the invention and, as described herein, a switching drive with an electromechanical drive for moving switching contacts in the direction of the axis of the vacuum interrupter chambers of the double-contact switch , and a power semiconductor switch connected in parallel to a contact pair of the double-contact switch that opens first in time and having a first and a second connection, the first connection of the power semiconductor switch and the first movable electrode of the double-contact switch being connected to the first current connection of the hybrid -Switching device are connected and the first movable electrode is firmly connected to a housing wall of the hybrid switching device, wherein the fixed electrode of the double-contact switch is connected to the second terminal of the power semiconductor switch, the second movable electrode of the double-contact switch is electrically connected to a movable part of the switching drive, and wherein the switching tube of the double-contact switch is mounted displaceably along its longitudinal axis up to a stop in the housing of the hybrid switching device.

Further advantages and application possibilities of the present invention result from the following description in connection with the exemplary embodiments illustrated in the drawings.

In the description, in the claims, in the summary and in the drawings, the terms used in the list of reference symbols and associated reference symbols are used.

• Fig. 1 eine perspektivische Ansicht einer Schnittdarstellung eines Doppelkontakt-Schalters mit Vakuumschaltkammern gemäß dem Stand der Technik;
• Fig. 2 das Blockschaltbild eines Ausführungsbeispiels eines Hybrid-Schaltgeräts gemäß dem Stand der Technik;
• Fig. 3 eine Schnittansicht eines ersten Ausführungsbeispiels eines Doppelkontakt-Schalters mit Vakuumschaltkammern gemäß der Erfindung, der insbesondere zum Einsatz in dem Hybrid-Schaltgerät von Fig. 2 geeignet ist; und
• Fig. 4 eine Schnittansicht eines zweiten Ausführungsbeispiels eines Doppelkontakt-Schalters mit Vakuumschaltkammern gemäß der Erfindung, der insbesondere zum Einsatz in dem Hybrid-Schaltgerät von Fig. 2 geeignet ist.

The drawings show in

• 1 a perspective view of a sectional representation of a double-contact switch with vacuum interrupter chambers according to the prior art;
• 2 the block diagram of an embodiment of a hybrid switching device according to the prior art;
• 3 a sectional view of a first embodiment of a double-contact switch with vacuum interrupter chambers according to the invention, in particular for use in the hybrid switching device of 2 suitable is; and
• 4 a sectional view of a second embodiment of a double-contact switch with vacuum interrupter chambers according to the invention, in particular for use in the hybrid switching device of 2 suitable is.

In the following description, identical, functionally identical and functionally related elements can be provided with the same reference symbols. Absolute values are given below only as examples and are not to be understood as limiting the invention.

1 shows a longitudinal section through a double-contact switch with a vacuum interrupter, which has a rotationally symmetrical, cylindrical shape with two separate partial switching chambers 1, 3, in particular of a similar or identical structure, for mechanical contact pairs 10, 30 of the switch. Both sub-interrupter chambers 1, 3 can either be designed as completely separate vacuum chambers or also be partially connected to one another, so that they have a shared vacuum.

As in 1 shown, both partial interrupter chambers 1 and 3 are separated in the middle of the vacuum interrupter by a partition wall 4, which consists of an electrically conductive material and carries two centrally arranged, fixed switching contacts 41, 42 of the mechanical contact pairs 10 and 30, the end faces of which Inside one of the switching chambers facing.

Likewise, the partition wall can be designed in a geometry such that it itself serves as a double contact arrangement. The contact surface of the partition wall can be designed in such a way that it consists of a low-erosion material with good resistance to welding at the same time. When used in a hybrid contactor that works completely without arcing, the use of a low-erosion contact material is not absolutely necessary; in this case, a material with good electrical conductivity and sufficient resistance to welding is advisable.

The switching contacts are opened and closed via axially moveable copper electrodes 11, 31, on the inner faces of which are attached switching contacts 12, 32 of the mechanical contact pairs 10 and 30 made of a suitable material, above all of sufficient resistance to welding and good electrical conductivity. The areas of the two movable electrodes 11, 31 that carry the switching contacts are each sealed by a flexible metal bellows 13, 33 from the outside of the respective switching chamber. Each metal bellows 13, 33 is soldered on the one hand to the respective electrode 11 or 31, on the other hand to a respective cover 14 or 34, which closes the respective partial switching chamber 1, 3, in particular via two circumferential, vacuum-tight soldered connections.

The bellows 13, 33 form gas-tight barriers between the areas of the electrodes 11, 31 that carry the switching contacts 12, 32 and the outside of the partial switching chambers 1, 3, so that a vacuum is maintained in these chambers.

Opposite the two movable electrodes 11, 31 is a common fixed electrode in the form of the above-mentioned disc-shaped switching chamber partition 4, which is connected along its entire peripheral side to the wall of the respective partial switching chamber 1, 3 either as a separate part or preferably as a part in the peripheral area itself the switching chamber wall 43 represents.

To conduct the load current, the fixed electrode 4 has an appropriately dimensioned, sufficient wall thickness. For electrical insulation from the two movable electrodes 11, 31, the fixed electrode 4 is at its peripheral end faces 43 in the direction of their respective switching chamber 1, 3 with an annular ring of insulating material 15, 35, for example made of ceramic, connected in a vacuum-tight manner.

In a hybrid switching device, this double-contact switch can be used with vacuum interrupters - as in 2 shown - be integrated in such a way that one of the two movable electrodes, for example the electrode 11 is rigidly connected via a flat power connection to a power connection of the hybrid switching device. The stationary electrode 4 of the vacuum interrupter is also connected to the hybrid switching device via a flat electrical connection in such a way that the mechanical contacts 10 of the first partial switching chamber 1 connected in this way are arranged electrically in parallel with a power semiconductor switch 20 of the hybrid switching device. The second movable electrode 31 is connected to the movable part of the electromechanical hybrid switching device drive via a further flat electrical connection. Electrically, the mechanical contacts 30 of the second switching chamber part 3 are connected in series with the parallel arrangement of the power semiconductor switch 20 and the mechanical contacts 10 of the first switching chamber part 1 . During switching operations, the electromechanical drive 40 of the hybrid switching device ensures that the moving contacts move in the direction of the interrupter axis. The power semiconductor switch 20 is controlled via switching electronics 50 which in turn exchanges signals with the electromechanical drive 40 . The electronic switching system 50 is configured in such a way that it regulates the timing of the switching through and blocking of the power semiconductor switch 20 depending on the switching states of the double-contact switch depending on corresponding signals from the electromechanical drive 40 .

In 3 a double-contact switch with a vacuum tube is shown, in which the outer diameters of the bellows for the two partial switching chambers 1 and 3 were chosen to be different. For example, if the radius R ₁ of the bellows 13' of the right-hand interrupting chamber 1 is 1/4 smaller than the radius R ₂ of the bellows 33' of the left-hand interrupting chamber 3, then due to the vacuum pressure p _Vak on the contacts 32, 4 of the left-hand interrupting chamber 3 acting force F ₂ = p _Vak × πR ₂ ² approximately 1.8 times higher than the vacuum force F ₁ = p _Vak × 9/16πR _{2 2} acting on the contacts 12, 4 of the right partial switching chamber ¹ .

When the switching drive is actuated to open the contacts, which is directly connected, for example, to the switching electrode 31 of the left partial switching chamber 3, the force F 1 acting on the contacts 12, 4 of the right partial switching chamber 1 is then first compensated, while the force F ₁ acting on the contacts 32, 4 of the left sub-interrupter chamber 3 burdensome greater force F ₂ keeps the contacts 32, 4 closed.

If the switching electrode 11 of the right-hand partial switching chamber 1 is mechanically firmly connected to the housing of the switching device, the entire vacuum tube body is set in motion as a result, so that the contacts 12, 4 provided in the hybrid switch for commutation to the power semiconductor open first.

When the vacuum tube reaches a mechanical stop, the end position of the vacuum tube body and thus also the desired contact opening distance for the commutation contacts 12, 4 is reached. With the further movement of the switching drive, the vacuum force F ₂ acting on the contacts 32, 4 of the left partial switching chamber 3 is compensated with a time delay, so that finally the contact pair 32, 4 provided for the galvanic isolation of the hybrid switch also opens.

Differently high contact pressure forces in the two partial interrupter chambers of a double-contact vacuum interrupter can also be realized via different wall thicknesses of the bellows and also via their number of corrugations.

In the 4 a double-contact switch with a vacuum tube is shown, in which the bellows 33" of the left-hand partial switching chamber 3 has a greater wall thickness and a lower number of corrugations (three corrugations 36) than the bellows 13" of the right-hand partial switching chamber 1 (four corrugations 37). As a result, the bellows 33" of the switching chamber section 3 has a higher spring stiffness than the bellows 13" of the switching chamber section 1.

The vacuum forces acting on the contact pairs 12, 4 and 32, 4 of the two partial interrupter chambers 1 and 3, which due to the same diameter of the bellows 13" and 33" are the same size in this example, another component in the form of the spring forces of the bellows 13" and 33" comes into play, which is different for the two partial switching chambers 1 and 3.

wobei F_Vak die Vakuumkraft und F_Balg die Federkraft eines Balgs bezeichnen.The effective contact pressure force F _eff is thus made up as $${\mathrm{f}}_{\mathrm{eff}}={\mathrm{f}}_{\mathrm{vac}}+{\mathrm{f}}_{\mathrm{bellows}}$$

where F _Vak denotes the vacuum force and F _bellows denotes the spring force of a bellows.

F _{eff_1} <F _{eff_3} then applies to the effective contact pressure forces in the two partial switching chambers 1 and 3 of the double-contact switch shown, so that due to the different spring constants of the two bellows 13", 33" the contact opening movement is analogous to that in FIG 3 case shown expires. The contact pairs 32, 4 of the left partial switching chamber 3 thus open again with a time delay compared to the contact pairs 12, 4 of the right partial switching chamber 1.

The time delay in the opening of the contact pairs 32, 4 and 12, 4 can also be brought about by a different choice of material for the bellows or generally the gas-tight barriers, for example by using one bellows made of spring steel with a high spring stiffness and another bellows made of spring steel with a low spring stiffness is produced.

The present invention is particularly suitable for switching high DC and low-frequency currents with virtually no arcing. Switching processes can be carried out with almost no burn-up, which leads to an extended service life of the switch. The double-contact switch according to the invention can be used in contactors, circuit breakers, motor protection switches, in particular for switching direct currents and low-frequency currents.

Reference sign

1

first partial switching chamber

10

mechanical contacts (disconnecting contacts) first partial switching chamber

11

movable electrode first partial switching chamber

12

moving contact first partial switching chamber

13

bellows

13'

Smaller diameter bellows

13''

Bellows with reduced wall thickness

14

Cover of the first partial switching chamber

15

Insulating material ring first partial switching chamber

2

vacuum interrupter

20

Power semiconductor switch

3

second partial switching chamber

30

mechanical contacts (separation contacts) second partial switching chamber

31

movable electrode second partial switching chamber

32

moving contact second partial switching chamber

33

bellows

33'

Larger diameter bellows

33''

Bellows with greater wall thickness

34

Cover second partial switching chamber

35

Insulating material ring second partial switching chamber

36

three shafts of bellows 33"

37

four shafts of bellows 13"

4

Partition / fixed electrode

40

electromechanical drive

41

Fixed contact first partial switching chamber

42

Fixed contact second partial switching chamber

43

Switching chamber wall fixed electrode

50

switching electronics

Claims (8)

1. A double-contact switch comprising

   - a first and a second tubular vacuum switching chamber (1, 3), which are designed as partial switching chambers of a switching tube (2),

   - an electrode (4), which is stationary in the switching tube, is arranged between the first and second vacuum switching chambers, and comprises a first fixed contact (41) projecting into the first vacuum switching chamber (1) and a second fixed contact (42) projecting into the second vacuum switching chamber (3),

   - a first electrode (11), which is arranged in the first vacuum switching chamber (1), is movable therein in the axial direction, and comprises a region, which carries a contact (12) and is sealed off in a gas-tight manner from the exterior of the first vacuum switching chamber (1),

   - a second electrode (31), which is arranged in the second vacuum switching chamber (3), is movable therein in the axial direction, and comprises a region, which carries a contact (32) and is sealed off in a gas-tight manner from the exterior of the second vacuum switching chamber (3), characterized in that

   - the gas-tight sealing-off device (13`; 13") of the region, carrying the contact (12), of the first electrode (11) is designed to be different from the gas-tight sealing-off device (33`; 33") of the region, carrying the contact (32), of the second electrode (31) in such a way that the opening of the first fixed contact (41) and of the contact (12) of the first electrode (11) and the opening of the second fixed contact (42) and of the contact (32) of the second electrode (31) take place at staggered times, wherein the gas-tight sealing-off devices (13`; 33`; 13", 33") are designed to be different with regard to their material properties and/or shape, and the different design causes the time-staggered opening of the contacts (12, 32, 41, 42) during a movement of one of the electrodes (31) with a switching drive (40) while the other electrode (11) is stationary.
2. The switch according to Claim 1,
   characterized in that
   the gas-tight sealing-off device (13`; 13") of the region, carrying the contact (12), of the first electrode (11) and the gas-tight sealing-off device (33`; 33") of the region, carrying the contact (32), of the second electrode (31) are each formed by a flexible bellows, in particular a metal bellows (13`, 33`; 13" 33").
3. The switch according to Claim 2,
   characterized in that
   the diameters, wall thicknesses, wave numbers and/or stiffnesses of the bellows (13`, 33'; 13" 33") are different.
4. The switch according to Claim 3,
   characterized in that
   the outer diameters of the bellows (13`, 33`) are different.
5. The switch according to Claim 4,
   characterized in that
   the radius R₁ of the bellows (13`) of the first vacuum switching chamber (1) is approximately one quarter smaller than the radius R<sub>2</sub> of the bellows (33`) of the second vacuum switching chamber (3`).
6. The switch according to Claim 3, 4 or 5,
   characterized in that
   the bellows (13") of the first vacuum switching chamber (1) has a larger wave number and/or a smaller wall thickness than the bellows (33") of the second vacuum switching chamber (3).
7. The switch according to one of the preceding claims,
   characterized in that
   the second electrode (31) can be coupled to a switching drive (40) and the first electrode (11) can be connected to a switch housing wall.
8. A hybrid switching device comprising

   - a first and a second power terminal,

   - a double-contact switch according to one of the preceding claims,

   - a switching drive comprising an electromechanical drive (40) for moving switch contacts in the direction of the axis of the vacuum switching chambers (1, 3) of the double-contact switch, and

   - a power semiconductor switch (20), which is connected to a contact pair (12, 41), opening first, of the double-contact switch and comprises a first and a second terminal,

   - wherein the first terminal of the power semiconductor switch (20) and the first movable electrode (11) of the double-contact switch are connected to the first power terminal of the hybrid switching device, and the first movable electrode (11) is fixedly connected to a housing wall of the hybrid switching device,

   - wherein the stationary electrode (4) of the double-contact switch is connected to the second terminal of the power semiconductor switch (20),

   - wherein the second movable electrode (31) of the double-contact switch is electrically connected to a movable part of the switching drive, and

   - wherein the switching tube of the double-contact switch is mounted displaceably along its longitudinal axis up to a stop in the housing of the hybrid switching device.

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