Patent Application
20210350989
This application claims the priority, under 35 U.S.C. § 119, of German patent application DE 10 2020 205 869.5, filed May 11, 2020; the prior application is herewith incorporated by reference in its entirety.
The invention relates to a drive unit for a moving contact of a vacuum tube, to a circuit breaker containing such a drive unit, and to a gas-insulated or air-insulated switchgear assembly containing such a circuit breaker.
Vacuum tubes are used in gas-insulated and air-insulated switchgear assemblies in order to switch currents. In particular, vacuum tubes are used in the medium-voltage sector (usually voltages of between 1 kV and 52 kV) and the high-voltage sector (usually voltages of over 52 kV), but vacuum tubes are also used in the low-voltage sector (voltages less than 1 kV) in order to switch currents above 1 kA.
A vacuum tube usually contains a fixed contact and a moving contact which is arranged at one end of a tube pin, which fixed contact and moving contact are physically remote from one another in the non-conductive switching state of the vacuum tube and lie one on the other in the conductive switching state of the vacuum tube.
The low density of ionizable particles in the interior of the vacuum tube helps to suppress arcs during switching processes. Since a complete vacuum cannot be technically generated in principle, it is however possible for an undesired arc to still be produced given high voltages and currents and a small distance between the fixed contact and the moving contact, which arc can damage the contacts due to material removal at the surfaces of the contacts and, due to the material released in the process, can promote the formation of a stronger arc. For this reason, the moving contact is moved as quickly as possible in order to keep the time period until complete contact is established as low as possible. It is customary in the art to use, with preference, spring mechanisms, but also electromagnetic drives, for this purpose.
However, on account of its high movement speed, the moving contact may bounce back from the fixed contact, so that the contact just established briefly reopens. In addition, in particular when used as a grounding switch or short-circuiting unit, forces which counteract the drive moving the moving contact may be created on account of the high short-circuiting current briefly flowing in the event of first contact between the two contacts and inductances which are always present. Each time the moving contact lifts off, intensive arcs are produced which can lead to the formation of heat and even to welding of the contacts to one another.
Therefore, the object of the invention is to introduce an improved drive unit for a moving contact of a vacuum tube, which moving contact allows contact to be made in a reliable manner between the moving contact and the fixed contact.
A first aspect of the invention achieves this object by way of a drive unit for a moving contact of a vacuum tube according to the independent claim. The dependent claims relate to preferred embodiments of the invention.
The drive unit for a moving contact of a vacuum tube has at least a tube pin which is or can be conductively connected to the moving contact, a drive which is connected to the tube pin, and a conductor bridge. The tube pin is preferably arranged such that it can move along its longitudinal axis. The drive is configured to move the tube pin along a movement direction. In this way, the drive can move the moving contact of the vacuum tube, which moving contact is connected to the tube pin, in a corresponding manner, as a result of which the vacuum tube can be switched over between a non-conductive switching state (open switch) and a conductive switching state (closed switch). The conductor bridge is directly or indirectly conductively connected to the tube pin and a stationary conductor and is configured to bridge a travel of the tube pin between the conductive switching state of the vacuum tube and the non-conductive switching state of the vacuum tube. For example, the conductor bridge can be manufactured as a stranded wire or a large number of thin sheets composed of copper or another conductive material. It is also possible to realize the conductor bridge by way of a sliding contact. Conductor bridges of this kind are well known in the technical field in question, and therefore a more detailed description can be dispensed with.
According to the invention, a magnet drive is also provided, which contains a first magnet element, which is mechanically connected to the tube pin, and a second magnet element. The second magnet element is preferably arranged in a stationary manner, but can also be mounted in a positionally variable manner, for example spring-mounted or mounted such that it can be pivoted by a drive. The two magnet elements are configured to build up a magnetic force between them when current is flowing through the vacuum tube and in this way to generate a contact-pressure force of the moving contact onto a fixed contact of the vacuum tube. In this case, one of the two magnet elements is a first coil through which a current flowing through the vacuum tube in the conductive switching state of the vacuum tube flows.
The drive unit according to the invention has the advantage that the first coil, at the moment at which the moving contact meets the fixed contact, builds up a correspondingly strong magnetic field with the incipient current through the coil, which magnetic field creates a magnetic force—an attracting or repelling magnetic force depending on the configuration—between the two magnet elements. In this case, the two magnet elements are arranged relative to one another such that the attracting or repelling magnetic force creates a contact-pressure force of the moving contact onto the fixed contact of the vacuum tube. This is therefore advantageous because this contact-pressure force exists only when current is flowing and in addition to the force provided by the drive of the drive unit, so that the magnet drive assists the drive of the drive unit with contact pressure of the moving contact. The drive of the drive unit can accordingly be produced with reduced expenditure, for example with comparatively weak springs, because it can be provided with a lower drive force, in particular spring force, than the prior art for the same contact-pressure force.
When the vacuum tube is used in a grounding switch, it is expected that the short-circuiting current will be interrupted by an interrupter or circuit breaker at another point of the current path after a short time, so that the drive can separate the now de-energized contacts of the vacuum tube from one another owing to the absence of the magnetic force once again using a low drive force, for example by a relatively weak auxiliary motor for tensioning a comparatively weak spring of the drive.
The other of the two magnet elements can be a second coil through which the current flowing through the vacuum tube in the conductive switching state of the vacuum tube flows. In this case, both magnet elements are designed as electromagnetic elements. Each of the two coils can be realized, for example, by a single conductor coil.
The first coil preferably has a first winding direction (sense) and the second coil preferably has a second winding direction which is opposite to the first winding direction. This creates a repelling magnetic force between the two coils, as a result of which particularly space-saving arrangements are possible. If, however, the tube pin is routed through the coil which functions as the second magnet element, so that the coil which is connected to the tube pin is arranged behind the coil which functions as the second magnet element as viewed from the vacuum tube, the two coils can also have the same winding direction and therefore create an attracting magnetic force between the coils. However, this embodiment requires increased structural outlay.
The other of the two magnet elements can comprise a ferromagnetic material or consist of a ferromagnetic material. When a soft-magnetic material is used, an attracting magnetic force can be produced between the two magnet elements. A contact-pressure force of the moving contact onto the fixed contact of the vacuum tube can be created by appropriate physical arrangement of the two magnet elements. For example, the tube pin can be routed through the first coil which functions as the second magnet element in this case, and the ferromagnetic magnet element can be arranged behind the first coil as viewed from the vacuum tube. As an alternative, the first coil can be arranged on the tube pin and the ferromagnetic element which functions as the second magnet element in this case can be arranged in front of the first coil as viewed from the vacuum tube.
The other of the two magnet elements can also be a permanent magnet. Such a configuration may be expedient in DC voltage applications in which the direction of flow of the direct current is known and the orientation of the north and the south pole of the permanent magnet can be selected in a corresponding manner because, in comparison to the use of a soft-magnetic material, time required for the magnetization can be dispensed with and the magnetic force can act immediately.
The two magnet elements are preferably arranged offset in relation to one another along the longitudinal axis of the tube pin. In this case, the magnetic force which exists between the two magnet elements acts immediately in the movement direction of the tube pin and therefore of the moving contact of the vacuum tube.
The two magnet elements are preferably arranged coaxially in relation to one another. In this arrangement, the magnetic effect between the two magnet elements is at a maximum.
In particularly preferred embodiments of the invention, the two magnet elements are arranged coaxially in relation to one another, wherein a circumference of a selected magnet element of the two magnet elements and a cutout area of a remaining magnet element of the two magnet elements are selected such that the selected magnet element can be at least partially displaced through the remaining magnet element. This can create a lateral overlap between the two magnet elements, so that a particularly large magnetic force can be generated.
A further aspect of the invention introduces a circuit breaker containing at least a vacuum tube and a drive unit for a moving contact of the vacuum tube according to the first aspect of the invention.
The circuit breaker can be configured, in particular, as a grounding switch or short-circuiting device.
A further aspect of the invention relates to a gas-insulated or air-insulated switchgear assembly comprising such a circuit breaker.
All aspects of the invention are preferably used in the field of medium-voltage or high-voltage engineering applications but can also be used in low-voltage engineering if large currents (in particular greater than 1 kA) are intended to be switched.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an electromagnetic drive for a power circuit-breaker with a vacuum interrupter, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Referring now to the figures of the drawings in detail and first, particularly to
The vacuum tube 1 constitutes the central switching element of the circuit breaker 20. A low pressure prevailing in the interior of the vacuum tube 1 largely suppresses the production of arcs in this case. It is customary in the art for the vacuum tube to be dimensioned depending on the voltages and currents switched. For example, an electrode 5 can be provided for a mid-potential in order to reduce potential differences within the vacuum tube 1 and therefore to be able to switch larger voltages given the same size of vacuum tube 1.
The vacuum tube 1 is connected to first and second fixed conductors 6 and 8, wherein the connection in the case of the moving contact 3 takes place via a conductor bridge 7 which compensates for the travel of the moving contact 3 or of the tube pin 19 between the conductive and the non-conductive switching state. It is customary in the art for the conductor bridge 7 to be able to be manufactured, for example, as a stranded wire or else as a large number of thin strips composed of a conductive material, such as copper, which are laid one above the other and can be displaced in relation to one another. However, the use of a sliding contact for a conductor bridge is also conceivable.
The tube pin 19 is connected by means of an insulator 9 to a drive 10 which moves the tube pin 19 and therefore the moving contact 3 in order to switch over the vacuum tube 1 between the two switching states. In the exemplary embodiment shown, the drive 10 contains a spring mechanism 11, which can quickly drive the tube pin 19 by spring force, and an auxiliary motor 12 which is connected to the spring mechanism 11 and is intended to tension one or more springs (not illustrated) of the spring mechanism 11 for further tripping of the spring mechanism 11. However, the drive 10 can also have an electrical or electromagnetic drive instead of the spring mechanism 11 and a rechargeable electrical energy store instead of the auxiliary motor 12.
The magnet drive 30 has two magnet elements which are configured as a first coil 13 and a second coil 14 in the present case. In the example shown, the first coil 13 is electrically conductively and mechanically connected to the tube pin 19 and accordingly moves with the tube pin 19. In contrast, the second coil 14 is stationary and connected to a second fixed conductor 8. In order to compensate for a travel of the tube pin 19, a conductor bridge 7 which electrically conductively connects the first coil 13 to the second coil 14 is provided, as in the prior art.
In the example shown, the first coil 13 and the second coil 14 each comprise only one conductor coil, but can also be embodied with more conductor coils, depending on the desired magnetic and therefore contact-pressure force. In the exemplary embodiment of
In the exemplary embodiment shown in
Within the scope of the invention, it is possible to provide more than two magnet elements, for example by way of the exemplary embodiments of
Each coil can also be provided with a ferromagnetic coating which is preferably electrically isolated from the coil by an insulator. In this case, the ferromagnetic coating is magnetized by the magnetic field of the coil when a current is flowing and can therefore maintain the magnetic field and therefore the contact-pressure force for a certain time after the flow of current ends.
The invention has been described in more detail with reference to exemplary embodiments which, however, are not to be interpreted as limiting the scope of protection, which is defined solely by the following patent claims, and serve merely for better understanding of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102020205869.5 | May 2020 | DE | national |
