Double contact vacuum switch

Abstract

The invention relates to a double-contact switch (10), comprising a first and a second tubular vacuum switching chamber (12, 14), which are designed as partial switching chambers of a switching tube (16); an electrode (18), which is fixed in the switching tube (16) and which is arranged between the first and second vacuum switching chambers (12, 14) and has a first fixed contact (20) protruding into the first vacuum switching chamber (12) and a second fixed contact (22) protruding into the second vacuum switching chamber (14); a first electrode (24), which is arranged in the first vacuum switching chamber (12) and can be moved therein in the axial direction and has a region (26) that bears a contact, which region is blocked off (28) gas-tight from the exterior of the first vacuum switching chamber; a second electrode (30), which is arranged in the second vacuum switching chamber (14) and can be moved therein in the axial direction and has a region (32) that bears a contact, which region is blocked off (34) gas-tight from the exterior of the second vacuum switching chamber, the second electrode (30) being fixed relative to the switching tube (16) and the first electrode (24) being movable relative to the switching tube (16) in order to open and close the contacts, and stop means (36, 38) being provided in such a way that the axial motion (40) of the first electrode (24) for opening the switching contacts in the vacuum switching chambers (12, 14) relative to the switching tube (16) is limited to a specified distance and, when the stop means (36, 38) hit each other, a mechanical impulse acting on the switching tube (16) is produced in the direction of the axial motion (40) in order break open any weldings of the contacts.

Description

[0001] The invention relates to a double-contact switch with vacuum interrupter chambers, which is particularly suitable for use in a hybrid switching arrangement and a hybrid switching device.

[0002] From the international patent application WO 2015 / 091105 A1 a hybrid switching arrangement for a hybrid switching device is known, see therein Fig. 1 For switching high DC currents in the range above 500 amperes, while simultaneously ensuring galvanic isolation after switching operations, a hybrid switch with a mechanical contact arrangement in the form of a special vacuum interrupter chamber, as presented in WO 2015 / 091096 A1, is suitable. In this advantageous switching arrangement, two serially arranged contact pairs are switched via two independently actuated movable switching electrodes (see therein). Fig. 2During a switching operation, one of the two contact pairs ("commutation contact") commutates the load current to a semiconductor switch, preferably in the form of an IGBT, where it is then brought to zero within a very short time, while the second contact pair ("isolating contact") finally ensures the galvanic isolation of the parallel arrangement of commutation contact and semiconductor switch responsible for the current shutdown.

[0003] To ensure the highest possible functional reliability, especially when switching currents in the range of several hundred amperes, the design of such switches or switching arrangements must, among other things, ensure that permanent welding of the switching contacts does not occur when switching on such high currents. Welding of switching contacts can occur primarily during the mechanical bounce process at the moment of re-contacting.

[0004] In the hybrid switching arrangements mentioned above, welding of the commutating contacts in particular can be successfully prevented by briefly activating the parallel-arranged power semiconductor during the turn-on phase so that the load current flows exclusively through it. The commutating contact thus remains load-free during this phase, which is critical for contact welding.

[0005] Under certain circumstances, the contact pair of the first isolating switch, to which no semiconductor switch is connected in parallel, may become welded, for example, if its closure occurs approximately at the same time as the commutating contact. Because the isolating contact and the commutating contact are arranged in series both electrically and mechanically, welding of the isolating contact is generally possible during the closing bounce phase if, at the moment of its brief lifting, a load current is already flowing through the commutating contact or the semiconductor switch.

[0006] The Japanese utility model JP S52 113371 U describes a double contact switch with vacuum interrupter chambers and stop means that limit the travel of moving contacts.

[0007] The object of the present invention is to further improve the double contact switch with vacuum interrupter chambers known from WO 2015 / 091096 A1.

[0008] This object is achieved by the subject matter of the independent claims. Further embodiments of the invention are the subject matter of the dependent claims.

[0009] One idea underlying the present invention is to structurally modify the double-contact switch known from WO 2015 / 091096 A1 in such a way that stop means are provided which limit the axial movement of a movable electrode of the switch with respect to a switching tube of the switch when the switching contacts are opened, such that when the stop means come into contact, a mechanical impulse acting on the switching tube is generated in the direction of the axial movement of the movable electrode to break any existing welds of the contacts. In other words, according to the invention, the axial movement of the movable electrode is limited by the stop means to such an extent that during a normal opening movement, in which the movable electrode is moved a predetermined distance, a stop and an associated mechanical impulse acting on the switching tube occur.The mechanical impulse is dimensioned in such a way that any existing welds between the contacts, for example between an electrode provided in the switching tube and a fixed electrode, can be broken.

[0010] According to a first embodiment, the invention now relates to a double contact switch with a first and a second tubular vacuum interrupter chamber, which are designed as partial interrupter chambers of a switching tube, an electrode which is fixed in the interrupter tube and arranged between the first and second vacuum interrupter chambers and has a first fixed contact projecting into the first vacuum interrupter chamber and a second fixed contact projecting into the second vacuum interrupter chamber, a first electrode arranged in the first vacuum interrupter chamber and movable therein in the axial direction, with a region carrying a contact which is sealed off in a gas-tight manner from the exterior of the first vacuum interrupter chamber, a second electrode arranged in the second vacuum interrupter chamber, with a region carrying a contact which is sealed off in a gas-tight manner from the exterior of the second vacuum interrupter chamber.The second electrode is fixed with respect to the interrupter, and the first electrode is movable with respect to the interrupter for opening and closing the contacts. The switch is provided with stop means such that the axial movement of the first electrode for opening the switching contacts in the vacuum interrupter chambers with respect to the interrupter is limited to a predetermined distance, and when the stop means come into contact, a mechanical impulse acting on the interrupter in the direction of the axial movement is generated to break any existing welds in the contacts. The stop means have a step in the shaft of the first electrode and a stop surface for the step formed by the inner end face of a guide sleeve for the first electrode.A guide sleeve has the advantage that, if the material is selected appropriately, shock loads when the lifting devices come into contact with each other lead to no or significantly less impairment of the other, sometimes more sensitive, components of the interrupter tube, since the step does not hit these components directly.

[0011] According to a second embodiment, the invention now relates to a double contact switch with a first and a second tubular vacuum interrupter chamber, which are designed as partial interrupter chambers of a switching tube, an electrode which is fixed in the interrupter tube and arranged between the first and second vacuum interrupter chambers and has a first fixed contact projecting into the first vacuum interrupter chamber and a second fixed contact projecting into the second vacuum interrupter chamber, a first electrode arranged in the first vacuum interrupter chamber and movable therein in the axial direction, with a region carrying a contact which is sealed off in a gas-tight manner from the exterior of the first vacuum interrupter chamber, a second electrode arranged in the second vacuum interrupter chamber, with a region carrying a contact which is sealed off in a gas-tight manner from the exterior of the second vacuum interrupter chamber.The second electrode is fixed with respect to the interrupter, and the first electrode is movable with respect to the interrupter for opening and closing the contacts. The switch is provided with stop means such that the axial movement of the first electrode for opening the switching contacts in the vacuum interrupter chambers is limited to a predetermined distance with respect to the interrupter, and when the stop means meet, a mechanical impulse acting on the interrupter in the direction of the axial movement is generated to break any existing welds between the contacts. The stop means comprise a shield of a gas-tight barrier of the first vacuum interrupter chamber and a stop surface for the shield formed by the inside of a cover of the interrupter chamber.

[0012] In particular, the specified distance is smaller than the maximum possible switching stroke of the first electrode for opening the switching contacts in the vacuum interrupters. This ensures that a mechanical impulse sufficiently strong to break welds is generated when the sling devices meet.

[0013] The switch can, in particular, comprise a housing in which the second electrode is fixed and which has an opening for movably supporting the first electrode. The maximum possible switching stroke is defined by a stop on the housing of an upper end face of the switching tube. The housing can also serve to mount an electromechanical drive for the first movable electrode.

[0014] In the first embodiment, the step can be incorporated into the shaft of the first electrode. However, in the first embodiment, the step can also be formed by a separate component fixed to the shaft of the first electrode.

[0015] In the first embodiment, the outer diameter of the step is particularly dimensioned such that an axial movement of the first electrode cannot result in contact with the inside of the gas-tight barrier.

[0016] In the first embodiment, the distance between the step and the stop surface in the closed state of the contacts can be dimensioned such that it substantially corresponds to a predetermined nominal opening distance of the first fixed contact and the contact-bearing region of the first electrode.

[0017] Further advantages and possible applications of the present invention will become apparent from the following description in conjunction with the embodiments shown in the drawings.

[0018] The drawings show in Fig. 1a to 1c various phases of a switching-off process in a double-contact switch with vacuum interrupter chambers according to a first embodiment of the invention; and Fig. 2 to 4 Sectional views of double-contact switches with vacuum interrupter chambers according to three different embodiments of the invention.

[0019] In the following description, identical, functionally identical, and functionally related elements may be provided with the same reference numerals. Absolute values ​​are given below only as examples and are not to be understood as limiting the invention.

[0020] The basic operation of the double contact switch according to the invention will now be explained using the Fig. 1a to 1c which shows the double contact switch during a switching-off sequence with previously welded isolating contacts.

[0021] Fig. 1a shows the double-contact switch 10 and the state of its switching tube 16 when switched on. The switching tube 16 has a first vacuum switching chamber 12 and a second vacuum switching chamber 14, both of which are designed as sub-switching chambers of the switching tube 16.

[0022] A fixed electrode 18 is arranged approximately centrally in the interrupter 16, which separates the interrupter 16 into the two sub-interrupter chambers 12 and 14. The fixed electrode 18 has a first fixed contact 20 and a second fixed contact 22. The two fixed contacts 20 and 22 can be implemented, for example, by the two end faces of the fixed electrode 18. The first fixed contact 20 projects into the first vacuum interrupter chamber 12, and the second fixed contact projects into the second vacuum interrupter chamber 14.

[0023] A first electrode 24, which is movable in the axial direction, is arranged in the first vacuum interrupter chamber 12. The electrode 24 has a region 26 carrying a contact that serves to make contact with the first fixed contact 20 of the electrode 18 and forms a first isolating contact, which can serve, for example, as a commutation contact in a hybrid switching arrangement, of the switch 10. The region 26 and a portion of the electrode 24 are sealed off in a gas-tight manner by means of a metal bellows 28. For this purpose, the metal bellows 28 is connected on the one hand to the shaft of the electrode 24 and on the other hand to the front end of the first vacuum interrupter chamber 12.

[0024] Likewise, in the second vacuum interrupter chamber 14, a second electrode 30 is arranged with a region 32 that carries a contact, which, in principle, is movable in the axial direction like the first electrode 24, but in the switch 10 shown, is fixed with respect to the switching tube 16. The fixing of the second electrode 30 can be achieved in different ways, in which Fig. 1a In the switch 10 shown, the second electrode 30 is fixed to a housing 42 of the switch 10. A portion 32 of the second electrode 30, like the first electrode 24, is sealed gas-tight by a metal bellows 34. Contacts 22 and 32 form a second isolating contact of the switch 10.

[0025] The switch is provided with a housing (42), wherein the second electrode 30 is fixed to a housing 42 of the switch 10, the switching tube 16 is movably mounted relative to the fixed second electrode 30, and the first electrode 24 is also movably mounted relative to the switching tube 16 and the second electrode 30. The possible axial direction of movement of the first electrode 24 is indicated by the double arrow 40.

[0026] To open the Fig. 1a When the switching contacts 20, 26 and 22, 32 are in the closed state, the first electrode 24 is moved upwards out of the housing 42, as shown in Fig. 1bThe axial movement of the first electrode 24 is typically generated by an electromechanical switching drive of a switching device into which the switch 10 with the housing 42 is installed. The switching drive can be connected directly to the shaft of the first electrode 24, for example, via a clamp connection. The movement of the first electrode 24 opens the first contact pair 20, 26 or the first isolating contact of the switch 10, while the contact pair 22, 32 or the second isolating contact initially remains firmly closed, for example due to prior welding. As a result, no movement of the switching tube 16 occurs during this phase of the contact opening process.

[0027] The axial movement of the first electrode 24 with respect to the switching tube 16 is limited by stop means 36, 38. The stop means have a step 36 in the shaft of the first electrode 24 and a stop surface 38 formed by the upper cover of the switching tube 16. Thus, when the first electrode 24 is moved out or axially to open the isolating contact comprising the contacts 20 and 26, the step 36 strikes the stop surface 38 or the cover of the switching tube 16 after a predetermined distance D. This collision or impact generates a mechanical impulse, particularly when the first electrode 24 connected to the switching drive has not yet reached its end position. The mechanical impulse subjects the switching tube 16 to an impact load, which is directly transmitted to the contact pair 22, 32.Depending on the power reserve and the electromechanical switching drive as well as the contact material of the contact pair 20, 32, the shock or impulse load is generally sufficient to break any welding of the contacts 22 and 32. Separating the contacts 22 and 32 thus initiates a movement of the switching tube 16 in such a way that it also moves in the direction of action of the electromechanical drive and thereby causes the contacts 22, 32 of the second isolating contact to open further, see . Fig. 1c .

[0028] The opening movement of the contacts of the switch 10 is stopped as soon as the outer end face of the upper cover of the switching tube 16 hits the inner wall of the housing 42 serving as a stop surface for the switching tube 16, from which the contact opening distances of the two contact pairs of the switch 10 result after switching off.

[0029] Figure 2shows a double contact switch 10', which is structurally similar to the Fig. 1a to 1cshown switch 10 and in which the stop means are also formed by a step 36' and the upper cover 38' of the switching tube 16. The step 36' can be incorporated into the shaft of the first electrode 24', for example by turning. Alternatively, the step 36' can also be designed as a separate component, for example by a spring ring that is mounted in a groove surrounding the shaft of the first electrode 24'. The outer diameter of the step 36' is generally selected such that there is no contact with the sensitive metal bellows 28 during a movement of the first electrode 24'. The relative movement of the first electrode 24' with respect to the switching tube 16 is limited by the stop means 36', 38' to the predetermined distance D', which is in particular smaller than a maximum possible switching stroke of the first electrode 24'.The specified distance D' corresponds to the distance between the step 36' and the inside of the upper cover 38' when the contacts 20 and 26 are closed, i.e., the first electrode 24' is not moved out of the switching tube 16, i.e., when the two isolating contacts 20, 26 of the switch 10' are closed. In particular, the specified distance D' corresponds to a nominal opening distance of the two contacts 20, 26.

[0030] Figure 3 shows a double contact switch 10" according to the first embodiment, in which, in contrast to the one in Figure 2shown switch 10', it is not the upper cover 38" of the switching tube 16 that is used as a stop surface for a step 36" of the shaft of the first electrode 24", but a guide sleeve 39", which is inserted into the upper cover 38" and is made in particular of a plastic. The guide sleeve 39" thus fulfills two functions: on the one hand, it serves as an exact guide for the first movable electrode 24", and on the other hand, its inner end face forms a stop surface for the step 36". The switch 10" is in Figure 3with both isolating contacts in the closed state, in which the specified distance D" corresponds to the distance between the step 36" and the inside end face of the guide sleeve 39", which is used as a stop surface. The guide sleeve 39" can in particular be made of a special plastic with which vacuum interrupters are usually equipped in order to ensure centered axial guidance of the movable electrode 24" during the switching process. A permanent fixation of the guide sleeve 39" to the interrupter 16, even for additional shock loads, can be achieved, for example, by a suitable screw connection on the cover 38" of the interrupter 16. Fixation of the guide sleeve 39" via welded connections or by snap-in hooks integrated into the sleeve is also conceivable.

[0031] In the Figure 4The switch 10‴ shown in the second embodiment is, in contrast to the switches shown in the Figures 2 and 3In the switches shown, a shield 36‴ is provided as a stop means, which at least partially encloses the metal bellows 28. The shield 36‴ is fastened to the end of the metal bellows 28 that is fastened to the shaft of the first electrode 24‴, and is moved by a movement of the first electrode 24‴, while at the same time the metal bellows 28 is compressed by the movement of the electrode 24‴ out of the switching tube 16. The inside of the upper cover 38‴ of the switching tube 16 serves as the stop surface for the shield 36‴. As soon as the movable electrode 24‴ is moved out of the switching tube 16 by the nominal opening distance or predetermined distance D‴, an impact process occurs between the shield 36‴ and the inside of the upper cover 38‴ of the switching tube 16.The shield 36‴ (also called a "bellows shield") primarily serves to shield the bellows 28, which is very sensitive due to its thin wall thickness, against the metal vapor and hot contact particles typically emitted during a vacuum arc-induced shutdown process. To enable its use as a stop device, the shield 36‴ is extended to such an extent that the frontal distance of the shield from the inside of the cover 38‴, when the isolating contacts 20, 26 of the switch 10‴ are closed, corresponds to the nominal opening distance of the contacts 20, 26 or the specified distance D‴. To distribute the energy of a shock pulse required to break a contact weld over a larger area, the frontal side of the shield 36‴ can be flanged parallel to the cover 38‴. As with the device shown in . Figure 3 In the switch shown, this switch 10‴ is provided with a guide sleeve 39‴ for the exact guidance of the first electrode 24‴.

[0032] Some design options for the switches described above are explained below: With regard to the repetitive shock loads in the case of welded contacts, the upper cover of the interrupter tube, if it serves as a stop surface for a stage or shield, can be made of stainless steel of sufficient wall thickness, for example. The edge surface of the cover facing the first vacuum interrupter chamber can be soldered to a ceramic ring 16' serving as an electrical insulator via a special metallization layer. This can ensure sufficiently high strength of this vacuum-tight solder connection, even with high switching frequencies, as in the case of contactors.

[0033] The cover edge facing the first vacuum interrupter chamber can be soldered to the ceramic ring 16', which serves as an electrical insulator, via a special metallization layer. In practice, this can ensure a sufficiently high strength of this vacuum-tight solder joint even at high switching frequencies, as in the case of contactors.

Claims

1. Double contact switch (10; 10'; 10"), having - a first and a second tubular vacuum switching chamber (12, 14), which are designed as partial switching chambers of a switching tube (16), - an electrode (18), which is fixed in the switching tube (16) and arranged between the first and second vacuum switching chambers (12, 14), having a first fixed contact (20) protruding into the first vacuum switching chamber (12) and a second fixed contact (22) protruding into the second vacuum switching chamber (14), - a first electrode (24; 24'; 24"), which is arranged in the first vacuum switching chamber (12) and movable in the axial direction therein, having a contact-bearing region (26), which is sealed off in a gas-tight manner from the exterior of the first vacuum switching chamber (28), - a second electrode (30), which is arranged in the second vacuum switching chamber (14), having a contact-bearing region (32) which is sealed off in a gas-tight manner (34) from the exterior of the second vacuum switching chamber (14), - a housing (42), wherein - the second electrode (30) is fixed to the housing (42) and the switching tube (16) is moveably mounted in relation to the fixed second electrode (30) and the first electrode (24) is also moveably mounted in relation to the switching tube (16) and the second electrode (30) and the first electrode (24; 24'; 24") is moveable in relation to the switching tube (16) for opening and closing the contacts, and characterised in that the double contact switch further has the following features: - stop means (36, 38; 36', 38'; 36', 38"; 39") are provided such that the axial movement (40) of the first electrode (24; 24'; 24"; 24‴) for opening the switching contacts in the vacuum switching chambers (12, 14) in relation to the switching tube (16) is limited to a predetermined distance (D; D'; D") and, when the stop means (36, 38; 36', 38'; 36", 38"; 39") meet, a mechanical impulse acting on the switching tube (16) is generated in the direction of the axial movement (40) to break any existing welding of the contacts, wherein the stop means have a step (36'') in the shaft of the first electrode (24") and a stop surface for the step (36") formed by the inner end face of a guide collar (39") for the first electrode (24").

2. Double contact switch (10‴), having - A first and a second tubular vacuum switching chambers (12, 14), which are designed as partial switching chambers of a switching tube (16), - an electrode (18), which is fixed in the switching tube (16) and arranged between the first and second vacuum switching chambers (12, 14), having a first fixed contact (20) protruding into the first vacuum switching chamber (12) and a second fixed contact (22) protruding into the second vacuum switching chamber (14), - a first electrode (24‴), which is arranged in the first vacuum switching chamber (12) and movable in the axial direction therein, having a contact-bearing region (26), which is sealed off in a gas-tight manner from the exterior of the first vacuum switching chamber (28), - a second electrode (30), which is arranged in the second vacuum switching chamber (14), having a contact-bearing region (32) which is sealed off in a gas-tight manner (34) from the exterior of the second vacuum switching chamber (14), wherein - and the first electrode (24‴) is moveable in relation to the switching tube (16) for opening and closing the contacts, and characterised in that the double contact switch further has the following features: - stop means (36‴, 38‴) are provided such that the axial movement (40) of the first electrode (24‴) for opening the switching contacts in the vacuum switching chambers (12, 14) in relation to the switching tube (16) is limited to a predetermined distance (D‴) and, when the stop means (36‴, 38‴) meet, a mechanical impulse acting on the switching tube (16) is generated in the direction of the axial movement (40) to break any existing welding of the contacts, wherein the stop means have a shield (36‴) of a gas-tight barrier (28) of the first vacuum switching chamber (12) and a stop surface (387‴) for the shield (36‴) formed by the inside of a cover of the switching tube.

3. Switch according to claim 1 or 2, characterized in that the predetermined distance (D; D'; D‴; D‴) is smaller than a maximum possible switching stroke of the first electrode (24; 24'; 24‴; 24‴) for opening the switching contacts in the vacuum switching chambers (12, 14).

4. Switch according to claim 1 or claim 1 in conjunction with claim 3, characterized in that the housing (42) has an opening for movable mounting of the first electrode (24), wherein the maximum possible switching stroke is defined by a stop of an end face of the switching tube (16) on the housing (42).

5. Switch according to claim 2 or claim 2 in conjunction with claim 3, characterized in that said switch has a housing (42), in which the second electrode (30) is fixed and which housing has an opening for moveable mounting of the first electrode (24), wherein the maximum possible switching stroke is defined by a stop of an end face of the switching tube (16) on the housing (42).

6. Switch according to claim 1 in conjunction with any one of claims 3 or 4, characterized in that the step (36'; 36") is incorporated into the shaft of the first electrode (24'; 24").

7. Switch according to claim 1 in conjunction with any one of claims 3 or 4, characterized in that the step is formed by a separate component fixed to the shaft of the first electrode (24'; 24").

8. Switch according to claim 1 in conjunction with any one of claims 3, 4, 6 or 7, characterized in that the outer diameter of the step (36'; 36") is dimensioned such that an axial movement of the first electrode (24'; 24") cannot result in contact with the inside of the gas-tight barrier (28).

9. Switch according to claim 1 in conjunction with any one of claims 3, 4 or 6 to 8, characterized in that the distance between the step (36'; 36") and the stop surface (39'; 39") in the closed state of the contacts is dimensioned such that it substantially corresponds to a predetermined nominal opening distance of the first fixed contact (20) and the contact-bearing region (26) of the first electrode (24'; 24").

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