Abstract
A vacuum switching device for medium or high voltages contains two contacts. At least one contact of which is mechanically movably mounted by a drive rod and thus is in electrical contact with the drive rod. The vacuum switching device has a vacuum chamber in which the contacts are arranged. The vacuum switching device has a spring contact, which is outside the vacuum chamber, and the drive rod, when the contacts are closed, is in electrical contact with a power line via the spring contact, and in that the spring contact, when the contacts are open, is electrically insulated from the drive rod.
Claims
1-11. (canceled)
12. A vacuum switching device for a medium or high voltage, comprising: a drive rod; two contacts, at least one of said two contacts is mounted so as to be mechanically movable via said drive rod and at a same time is electrically connected to said drive rod; a vacuum space in which said contacts are disposed; and a spring contact disposed outside said vacuum space, said drive rod, in a closed state of said contacts, is electrically connected to a power line via said spring contact, and in that said spring contact, in an open state of said contacts, is electrically insulated from said drive rod.
13. The vacuum switching device according to claim 12, wherein said drive rod has a cross-sectional contour that varies along a switching axis.
14. The vacuum switching device according to claim 12, wherein said drive rod has, along a switching axis, an electrically insulating region and an electrically conducting region.
15. The vacuum switching device according to claim 14, wherein said spring contact, in the open state of said contacts, bears on said electrically insulating region of said drive rod.
16. The vacuum switching device according to claim 12, wherein said spring contact, in the open state of said contacts, is disposed in a contact-free manner with regard to said drive rod.
17. The vacuum switching device according to claim 13, wherein said cross-sectional contour of said drive rod is thickened in such a way that, during a closing movement of said drive rod along the switching axis, electrical contact is made between said drive rod and said spring contact.
18. The vacuum switching device according to claim 17, wherein said spring contact is subjected to elastic deformation while the electrical contact is being made.
19. The vacuum switching device according to claim 17, wherein said cross-sectional contour of said drive rod narrows again along the switching axis on a side facing away from said contact after a maximum thickening.
20. The vacuum switching device according to claim 19, wherein, in the closed state of said contacts, said spring contact bears in an elastically deformed state against a narrowing region of said cross-sectional contour of said drive rod.
21. The vacuum switching device according to claim 13, wherein said cross-sectional contour being a varying cross-sectional contour of said drive rod is configured in a rotationally symmetric manner.
22. The vacuum switching device according to claim 14, further comprising a potential controller, said electrically conducting region of said drive rod has a defined potential being settable via said potential controller for said drive rod.
Description
[0020] In the figures:
[0021] FIG. 1 shows a vacuum switching tube in the open state of the contacts and electrical gas insulation between the drive rod and a spring contact,
[0022] FIG. 2 shows the vacuum switching tube according to FIG. 1 in a half-closed state of the contacts and bearing spring contact,
[0023] FIG. 3 shows the vacuum switching tube according to FIGS. 1 and 2 in the closed state of the contacts,
[0024] FIG. 4 shows a section through the varying cross-sectional contour of the drive rod with the respectively bearing cross sections,
[0025] FIGS. 5 to 7 show analogous illustrations to FIGS. 1 to 3 with solid-body insulation between the electrically conducting drive rod and the spring contact in the three different states as in FIGS. 1 to 3,
[0026] FIG. 8 shows a schematic illustration of an alternative illustration of the spring contact and the variation in the cross-sectional contour of the drive rod,
[0027] FIG. 9 shows a vacuum switching tube according to the prior art with corresponding contacting of the drive rod according to the prior art.
[0028] FIG. 1 depicts a vacuum switching device 20, which has a vacuum space 28 in which two contacts, a moving contact 22 and a fixed contact 24 are arranged. The moving contact 22 is connected to a drive rod 26, via which the contact 22 is also electrically contacted. The drive rod 26 of the moving contact 22 is in turn in mechanically operative engagement with a drive (not illustrated here). The vacuum switching device 20 also has a housing 60 on which vapor shields 62 are arranged, and the vacuum space 28 furthermore has insulations 64, which are generally represented in the form of rotationally symmetric ceramic components. Furthermore, to seal off the drive rod 26 with respect to the gas space 30 located outside the vacuum space 28, use is made of a vacuum bellows 66. The gas space 30 is in this case, here too, a closed-off space in which a specified insulating gas is present, wherein the insulating gas can be for example simple air or an additionally dielectrically acting insulating gas, for example a fluoroketone or a fluoronitrile. In principle, however, it is also possible for the vacuum space 28 of the vacuum switching device 20 to be in a free environment, for which reason the outside atmosphere in which the vacuum switching device is located can be considered to be the gas space 30.
[0029] To this extent, the described vacuum switching device 20 according to FIG. 1 is configured analogously to a vacuum switching device according to the prior art, which is illustrated by way of example in FIG. 9. The vacuum switching device according to FIG. 9 has in this case a conductor line 70, which is directly connected to the drive rod 26 and is thus permanently in electrical contact therewith.
[0030] In contrast to this embodiment according to FIG. 9 and the prior art, for electrical contacting of the drive rod 26, use is made of a spring contact 32, which is schematically illustrated in FIG. 1 and is in turn electrically connected to a further electric conductor, for example the above-described conductor line 70 known from the prior art. FIG. 1 illustrates an open state 34 of the contacts 22 and 24, wherein, in this state, the spring contact 32 which is located outside the vacuum space 28 in the gas space 32, is arranged at a distance from the drive rod 26. The distance of the spring contact 32 from the drive rod 26 is large enough that no electrical contact is made in this state 34. Between the spring contact 32 and the drive rod 26 there is an insulating gas, for example synthetic air.
[0031] On a side of the spring contact facing away from the contacts 22 and 24 there is a variation in the cross-sectional contour 38 of the drive rod 26. If, as illustrated in FIG. 2, a movement takes place along the arrow F.sub.a, mechanical engagement of the spring contact 32 with the drive rod 26, or the varying cross-sectional contour 38-I thereof, occurs. Thus, the spring contact 32 is elastically deformed, this being expressed by the spring force Fs. Furthermore, as a result, a further force Fb occurs, which can be referred to as braking force and counteracts a closing movement 46 along a switching axis 36.
[0032] The braking force Fb that arises on account of the described engagement prevents the moving contact 22 from striking the fixed contact 24 too heavily, this considerably reducing undesired bouncing, known from the prior art, of the two contacts 22 and 24.
[0033] Furthermore, FIG. 3 illustrates a closed state 44 of the contacts 22 and 24, wherein the cross-sectional contour 38 narrows again after a region of the maximum thickening 50 (FIG. 4) such that the spring contact 32 bears against the drive rod 26 in such a way that the contact system with the contacts 22 and 24 is pressed closed, this again preventing bouncing in a closed state since reopening of the contacts 22 and 24 is prevented by the pressure force F.sub.b.
[0034] FIG. 4 shows an enlarged schematic illustration of the drive rod 26 and the cross-sectional contour 38-I to IV thereof, explaining the individual stations from FIGS. 1 to 3 in more detail. In this case, the spring contact (not illustrated in FIG. 4 for the sake of clarity) is located, in the open state 34 of the contacts 22 and 24, as is illustrated in FIG. 1, approximately at the level of the cross-sectional contour 38-I. In this case, there is also electrical insulation between the spring contact 32 and the drive rod 26. Subsequently, the drive rod 26 moves upward along the switching axis 36 in the illustration according to FIG. 4, with the result that, in the cross-sectional contour 38-11, contact of the spring contact 32 with the drive rod 26 occurs. In the process, the drive rod 26 completes a closing movement in the direction of the arrow 46. In this state, deceleration of the drive rod 26 occurs on account of the elastic deformation and the pressing of the spring contact 32 in the region 38-II. The region 38-II is followed along the closing movement 46 by a region 38-III, which represents a maximum cross-sectional contour of the drive rod 26. This is where the region of the maximum thickening 50 is located. As the closing movement 46 continues, the spring contact 32 slides over the region 50 and arrives in a region 52 which again has a narrowing cross-sectional structure, which is provided with the reference sign 38-IV. In this region 52, the spring contact 32 bears, still in an elastically deformed state, against the drive rod 26 and brings about a force on the contacts 22 and 24 that keeps them closed.
[0035] The vacuum switching device 20 described in FIGS. 1 to 4 has the following advantages compared with the prior art. Firstly, the current path is doubly interrupted, namely between the contacts 22 and 24 and between the drive rod 26 and the spring contact 32. This allows the NSDD to be virtually ruled out statistically. In addition, on account of the specific construction of the drive rod and the engagement thereof in the spring contact 32 in the form described, bouncing of the contacts 22 and 24 when they meet is reduced so greatly that fusing and damage of contact faces 58 of the contacts 22 and 24 are considerably reduced.
[0036] In FIGS. 5, 6 and 7, an analogous movement of the contacts 22 and 24 toward one another is described, as has already been explained in detail with respect to FIGS. 1 to 3. The difference of FIGS. 5 to 7 from FIGS. 1 to 3 resides in the fact that the electrical insulation between the spring contact 32 and the drive rod 26 in the open state 34 of the contacts 22 and 24 is effected by solid insulation, for example by polytetrafluoroethylene. The electrically insulating region 40 at the drive rod 26 is thus surrounded for example by a sleeve made of this solid insulation material and the spring contact 32 bears in an insulating manner there. During the movement of the drive rod 26, the spring contact moves analogously to FIG. 2 out of the electrically insulating region 40 and into an electrically conducting region 42. Thus, the drive rod 26 is brought into contact with the electric current path.
[0037] FIGS. 5 to 7 illustrate a similar cross-sectional variation 38-I to 38-IV to the case in FIGS. 1 to 3. In principle, this is not absolutely necessary in order to achieve a braking action of the drive rod 26 and of the contact 24 before meeting the contact 22. To this end, other measures would also be used, for example an increase in the force F.sub.s by which the spring contact 32 is pressed against the drive rod 26.
[0038] A further alternative configuration is illustrated very schematically in FIG. 8; FIG. 8 shows only the contacts 22 and 24 and the drive rod 26 and the spring contact 32 of the vacuum switching device 20, which is not illustrated fully here. When the closing movement takes place in the direction of the arrow 46, the spring contact 32, configured in the form of a flat spring, is pressed against a disk attached to the drive rod 26, wherein this construction also exhibits a variation in the cross-sectional contour 38-I to 38-IV. The narrowing region 52 and the thickening region 54 can in this case be configured to be very short along the switching axis and be reduced to zero. What is important is that the spring contact 32 is configured such that deliberate braking of the drive rod 26 and of the contact 22 can take place.
[0039] In principle, it should be noted that, in the open state 34 of the contacts, a defined potential, which results from the grid environment, should be applied to the drive rod. Moreover, it should be noted that the design of the contacts that are described in FIGS. 1 to 9 is purely by way of example, and in principle is also possible for pot contacts or pin-tulip contacts to be used for the described technological implementation.
