Patent Application
20080302765
The invention relates to a vacuum-insulated switching device having a grounded vacuum vessel and having a contact system comprising a fixed contact and a moving contact, which are each connected by vacuum-tight bushings, which provide insulation from the housing, to electrical connecting lines, with the moving contact being coupled to a drive apparatus by means of an insulating transmission element and in a vacuum-tight manner.
A switching device such as this is known from EP 09 44 105 B1. The switching device disclosed there has a grounded vacuum vessel in which a fixed contact is connected via a vacuum-tight bushing, which provides insulation from the housing, to an electrical connecting line, and a moving contact is connected by means of an insulating transmission element to a drive apparatus, and via a flexible conductor via a further vacuum bushing, which provides insulation from the housing, to a further connecting line. The fixed contact and the moving contact form a contact system in the switching device in order to make and break a conductive connection between the connecting lines. In order to ensure switching operation and an adequate withstand voltage for the switching device, a pressure of <10−4 hPa is required within the vacuum vessel. Furthermore, an arrangement such as this requires measures in order to shield the grounded vacuum vessel from the arc which occurs during a switching process.
The object of the present invention is to develop a vacuum-insulated switching device of the type mentioned initially so as to reduce the requirements for the vacuum while still having an adequate withstand voltage and high switching functionality.
According to the invention, this object is achieved in that a further vacuum vessel is arranged in the grounded vacuum vessel, and the fixed contact and the moving contact are arranged in the further vacuum vessel and are passed out of the further vacuum vessel by means of further vacuum-tight bushings.
A switching device such as this advantageously makes it possible to achieve a high switching capacity in the further vacuum vessel because it prevents any interaction between an arc, which occurs between the moving contact and the fixed contact during a switching process, and the grounded vacuum vessel and with other elements arranged in the switching device, such as the connecting lines. Furthermore, a hard vacuum is required only in a small volume of the further vacuum vessel, with a less-hard vacuum being adequate in the grounded vacuum vessel.
In one preferred embodiment, the pressure in the grounded vacuum vessel is less than 10−2 hPa, and the pressure in the further vacuum vessel is less than 10−4 hPa. A pressure of <10−4 hPa in the second vacuum vessel advantageously ensures that the switching device has an adequate switching capacity, with a pressure of <10−2 hPa in the first vacuum vessel being sufficient to ensure the dielectric insulation of the switching device.
In a further preferred refinement of the invention, a vacuum monitoring device with a pump apparatus is provided on the grounded vacuum vessel. Such a vacuum monitoring device with a pump apparatus advantageously makes it possible to monitor and maintain the pressure required for dielectric insulation in the grounded vacuum vessel.
In one particularly preferred embodiment, the pump apparatus comprises an ion getter pump. An ion getter pump such as this offers a simple and low-cost capability to maintain the pressure in the first vacuum vessel.
In one preferred embodiment, the moving contact is coupled to the drive apparatus by means of a movable drive rod which is sealed by means of a bellows on the grounded vacuum vessel, and a conductive connection is formed between the moving contact and one of the connecting lines by means of a flexible electrical conductor.
An arrangement such as this makes it possible, in a simple manner, to transmit a movement from a drive apparatus to the moving contact in order to close the connection between the fixed contact and the moving contact, and to make an electrical connection by closing the contact system comprising the fixed contact and the moving contact. Further switching functions of the switching device, such as a disconnection function and a grounding function, can be provided in a switching device such as this either outside the grounded vacuum vessel by means of suitable arrangements, or else in the further vacuum vessel if, for example, a vacuum interrupter as described in PCT/DE2005/001613 is advantageously used as the further vacuum vessel.
In another preferred embodiment, the moving contact is coupled to the drive apparatus by means of a transmission element which can pivot and is sealed by means of a bellows on the grounded vacuum vessel, and a conductive connection is formed between the moving contact and one of the connecting lines by means of a flexible electrical conductor.
An arrangement such as this likewise advantageously makes it possible to transmit a movement of a drive apparatus to the moving contact in order to close the contact system comprising the fixed contact and the moving contact.
In one expedient refinement, the transmission element can be pivoted to an intermediate position, which represents a disconnected position, with the flexible electrical conductor being decoupled from the moving contact. In an arrangement such as this, an isolating gap is advantageously formed in the grounded vacuum vessel.
In a further development of the invention, the transmission element can be pivoted to a limit position, in which a conductive connection is formed to the grounded vacuum vessel. This allows the switching device to be grounded in a simple manner.
In a further refinement of the invention, the vacuum-tight bushings are formed from a ceramic material, with joints to the grounded vacuum vessel being metalized. Bushings such as these advantageously allow insulation from the connecting lines, and at the same time the formation of a vacuum-tight connection, for example by means of a soldered joint, to the grounded vacuum vessel.
In a further expedient refinement, the insulating transmission element is formed from a ceramic material. A ceramic material advantageously offers the insulating characteristics for the transmission element.
In one particularly preferred embodiment, the ceramic material is Al2O3. Al2O3 is particularly advantageous for making vacuum-tight bushings.
In a further expedient refinement of the invention, the vacuum-tight connection of the drive apparatus and transmission element is formed by a bellows. A bellows such as this offers a simple capability to make a connection for transmission of a movement of the drive apparatus to the moving contact piece.
The invention will be explained in more detail in the following text using the drawing and one exemplary embodiment, with reference to the attached figures, in which:
In the vacuum-insulated switching device 1, an electrically conductive connection is formed between the connecting lines 3 and 4, wherein the drive rod 13 causes the moving contact 9 (which is firmly connected to it via the transmission element 15) to move in the direction of the fixed contact 8 via the drive apparatus, which is not illustrated. Once the contact position has been reached, in which the fixed contact 8 and the moving contact 9 are connected to one another, then current flows via the connecting line 3, the fixed contact 8, the moving contact 9, the flexible electrical conductor 12 to the connecting line 4. In order to interrupt the electrical connection between the connecting lines 3 and 4, the drive apparatus causes the moving drive rod 13 to move, and the moving contact 9 is disconnected from the fixed contact 8 during this movement. When the moving contact 9 and the fixed contact 8 are disconnected, an arc is struck in the further vacuum vessel 7, and is quenched at the next current zero crossing. The quenching of this arc is ensured by the vacuum formed in the further vacuum vessel 7, so that the vacuum-insulated switching device has an adequate switching capacity. At the same time, the hermetically sealed separation of the further vacuum vessel 7 prevents ions from the arc being able to enter the area of the grounded vacuum vessel 2. The pressure in the grounded vacuum vessel 2 is in a range of ≦10−2 hPa, and therefore, with appropriate housing dimensions, is in a range below the so-called Paschen minimum, which occurs at about 1 Pa*m, ensuring adequate dielectric insulation in the grounded vacuum vessel 2, with the pressure in the further vacuum vessel 7 being in a range of ≦10−4 hPa.
In the arrangement shown in
In this exemplary embodiment, the contact system comprising the fixed contact 8 and the moving contact 9 is closed and opened by pivoting the transmission element 15′, with a connection being made between the connecting lines 3 and 4′ via the contact system comprising the fixed contact 8 and the moving contact 9, as well as the flexible electrical conductor 12′, when the contact system is closed. The further vacuum vessel 7 is used to shield the arc, which occurs during the process of disconnecting the fixed contact 8 and the moving contact 9, from the grounded vacuum vessel 2 and the components arranged in it.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE05/01982 | 11/2/2005 | WO | 00 | 4/30/2008 |
