Method for measuring pressure in a vacuum switching tube

Abstract

The invention relates to a method for measuring a pressure in a vacuum switching tube (1), comprising the steps of: b) providing the vacuum switching tube (1), which has a first electrode (3) and a second electrode (4) having a contact state in which they are in contact with each other and a separation state in which they are separated from each other, and a housing (2) which defines an interior space (26) in which the first electrode and the second electrode are arranged, and which maintains a vacuum in the interior space (26) so that in the separation state the first electrode and the second electrode are electrically isolated from each other by the vacuum; c) applying an electrical ignition voltage between the first electrode and the second electrode, thereby generating a direct current arc between the first electrode and the second electrode in their separation state;d) Applying an electric field and a magnetic field to the interior space so that electrons released in the direct current arc are accelerated, generating a gas discharge that is different from the direct current arc, wherein the electric field in the interior space (26) has a different orientation than the magnetic field; e) Measuring the electric current (I) of the gas discharge. The invention also relates to a pressure measuring device (40) with the vacuum switching tube (1).

Description

[0001] The invention relates to a method for measuring pressure in a vacuum switching tube and a pressure measuring device configured to carry out the method.

[0002] A vacuum interrupter is designed to perform electrical switching operations under a vacuum. To interrupt an electric current, the two electrodes in the vacuum interrupter are moved from a contact state, in which the two electrodes are in contact, to a spaced state, in which the two electrodes are separated. In the spaced state, the vacuum electrically isolates the two electrodes from each other. To ensure the vacuum interrupter functions correctly, the vacuum pressure must be low. Conventionally, the vacuum pressure is determined using the magnetron method. In this method, electrons are accelerated in an electric field and forced by a magnetic field onto spiral paths, causing the electrons to travel a significantly longer path to the anode.Gas molecules struck by these electrons can be ionized, allowing a gas discharge to build up in the vacuum. The current intensity of the gas discharge correlates with the vacuum pressure. Devices for measuring the internal pressure of vacuum switching tubes are known from DE 33 47 176 A1 and GB 2 203 282 A.

[0003] The delay times, after which the gas discharge actually ignites following the application of the electric and magnetic fields, vary considerably and can be up to 30 minutes or longer. The delay times are longer the lower the vacuum pressure. This disadvantageously results in a long measurement time for determining the vacuum pressure. Because the pressure of each vacuum switching tube is determined during its manufacture, the long measurement time also negatively extends the production time of the vacuum switching tubes.

[0004] The object of the invention is therefore to provide a method for measuring a pressure in a vacuum switching tube and a pressure measuring device for measuring the pressure in the vacuum switching tube, in which measuring times for determining the pressure of the vacuum in the vacuum switching tube are short.

[0005] The inventive method for measuring pressure in a vacuum switching tube comprises the following steps: b) providing the vacuum switching tube, which has a first electrode and a second electrode, which have a contact state in which the first electrode and the second electrode are in contact with each other, and a separation state in which the first electrode and the second electrode are separated from each other, as well as a housing that defines an interior space in which the first electrode and the second electrode are arranged, and which maintains a vacuum in the interior space, so that in the separation state the first electrode and the second electrode are electrically isolated from each other by the vacuum; c) applying an electrical ignition voltage between the first electrode and the second electrode, thereby generating a direct current arc between the first electrode and the second electrode in their separation state;d) Applying an electric field and a magnetic field to the interior so that electrons released in the direct current arc are accelerated, producing a gas discharge that is different from the direct current arc; e) Measuring the electric current of the gas discharge.

[0006] The invention is based on the understanding that a gas discharge can only be generated if a sufficient number of free electrons are present in the interior. Conventionally, these free electrons are formed by a spontaneous charge separation of the gas particles arranged in the interior. This is a stochastic process that also requires a long time. By generating a direct current arc in the interior, the free electrons can be produced, for example, by vaporizing and ionizing a metal or alloy at the first and / or second electrode. This results in the free electrons being generated in a shorter time compared to a conventional method in which the direct current arc is not generated, thus reducing the measurement time for measuring the pressure in the vacuum interrupter.Because the pressure inside the vacuum switching tube is measured during its manufacture, the manufacturing time of the vacuum switching tube can also be shortened.

[0007] It is preferred that in step c) the electrical ignition voltage is first applied to the first and second electrodes in their contact state, and then the first and second electrodes are brought into the spaced state, with the electrical ignition voltage remaining applied to them. This allows the electrical ignition voltage to be chosen to be low. Alternatively, it is preferred that in step c) the first and second electrodes are first brought into the spaced state, and then the electrical ignition voltage is applied to them. This advantageously eliminates the need for a switching operation of the vacuum switching tube during the process.

[0008] The electric field and the magnetic field preferably enclose an angle in the interior that lies in the range of 70° to 90°.

[0009] It is preferred that the method comprises the step of: a) performing a calibration by setting different pressures in the interior of a calibration vacuum switching tube, which has an interior, generating a gas discharge at each of the different pressures by applying an electric field and a magnetic field to the interior, and measuring the electric current of the gas discharge. Based on the calibration, the pressure can be accurately determined using the current measured in step e). Preferably, the interior of the calibration vacuum switching tube is identical in construction to the interior of the vacuum switching tube, except for the presence of a through-hole through which the interior of the calibration vacuum switching tube can be supplied from outside the tube with a gas having the different pressures.This allows the calibration to be performed with high accuracy, enabling the pressure to be determined with particularly high precision.

[0010] In a first preferred embodiment, in step d), the electric field is a first electric field generated by applying an electric accelerating voltage between the first and second electrodes. It is preferred that the electric accelerating voltage is greater than the electric ignition voltage. It is also preferred that the distance between the first and second electrodes is further increased after the DC arc has been generated. This allows the path that the electrons must travel to reach the anode to be lengthened after the DC arc has been ignited, thereby increasing the probability of gas discharge formation.

[0011] In a second preferred embodiment, in step d), the electric field is a second electric field generated by applying an electric acceleration voltage between the housing and one or both of the first and second electrodes. In particular, the second electric field is oriented such that the housing forms the anode. It is preferred that in step b), a first electric field is generated by applying the electric ignition voltage, wherein a first magnetic field, having a different orientation than the first magnetic field, is applied to the interior in a region extending between the first and second electrodes. The first magnetic field prevents the free electrons from reaching the first or second electrode.It is particularly preferred that the first electric field and the first magnetic field in the interior enclose an angle which lies in the range of 70° to 90°.

[0012] In the second embodiment, it is particularly preferred that the electric field and the magnetic field are applied before the electrical ignition voltage is applied. This allows the free electrons generated in the direct current arc to be accelerated immediately and produce the gas discharge.

[0013] The pressure measuring device according to the invention is configured to carry out the method according to the invention or a preferred embodiment thereof.

[0014] The invention will be explained in more detail below with reference to the attached schematic drawings. These show Fig. 1 a top view of a first embodiment of a pressure measuring device with a vacuum switching tube, Fig. 2 a section through the vacuum switching tube Fig. 1, Fig. 3 a top view of a second embodiment of the pressure measuring device with a vacuum switching tube, Fig. 4 a section through the vacuum switching tube Fig. 3 and Fig. 5 an example of a current flow.

[0015] How it looks Fig. As can be seen from Figures 1 to 4, a pressure measuring device 40 has a vacuum switching tube 1. The method for measuring a pressure in the vacuum switching tube 1 comprises the steps: b) Providing the vacuum switching tube 1, which has a first electrode 3 and a second electrode 4, which has a contact state (not in Fig. 2 and Fig. 4 shown), in which the first electrode 3 and the second electrode 4 are in contact with each other, and a separation state (in Fig. 2 and Fig. 4) in which the first electrode 3 and the second electrode 4 are spaced apart from each other, and which has a housing 2 that delimits an interior space 26 in which the first electrode 3 and the second electrode 4 are arranged, and which maintains a vacuum in the interior space 26, so that in the spaced-apart state the first electrode 3 and the second electrode 4 are electrically isolated from each other by the vacuum; c) Applying an electrical ignition voltage between the first electrode 3 and the second electrode 4, thereby generating a direct current arc between the first electrode 3 and the second electrode 4 in their spaced-apart state;d) Applying an electric field and a magnetic field to the interior space 26, such that electrons released in the direct current arc are accelerated, generating a gas discharge that is different from the direct current arc, wherein the electric field in the interior space 26 has an orientation different from the magnetic field; e) Measuring the electric current I of the gas discharge.

[0016] Fig. 2 and Fig. Figure 4 shows that the vacuum switching tube 1 can have an axial direction 31, a radial direction 32 related to the axial direction 31, and a circumferential direction 33 related to the axial direction 31. The first electrode 3 can be fixed relative to the housing 2, and the second electrode 4 can be longitudinally displaceable in the axial direction 31 relative to the housing 2. For this purpose, the vacuum switching tube 1 can have a bearing 9 on which the second electrode 4 can slide in and against the axial direction 31. It is conceivable to displace the second electrode 4 mechanically, in particular by using a spring mechanism. Starting from the contact state, the first electrode 3 and the second electrode 4 can be brought into the spaced-away state by displacing the second electrode 4 away from the first electrode 4 in the axial direction 31.The first electrode 3 can have a first contact surface 7 and the second electrode 4 can have a second contact surface 8, the first contact surface 7 and the second contact surface 8 being arranged in the interior 26. The first electrode 3 can have a thickening at its longitudinal end facing the second electrode 4, and the second electrode 4 can have a thickening at its longitudinal end facing the first electrode 3. The first contact surface 7 and the second contact surface 8 are in contact in the contact state, allowing a current to flow from the first electrode 3 to the second electrode 4, and are spaced apart from each other in the separation state, preventing the current from flowing from the first electrode 3 to the second electrode 4.

[0017] The first electrode 3 can have a first terminal 5 located outside the housing 2, and the second electrode 4 can have a second terminal 6 located outside the housing 2. Electrical conductors can be connected to the first terminal 5 and the second terminal 6 in an electrically conductive manner. The vacuum switching tube 1 can have a bellows 10 which is attached to the bearing 9 and to the second electrode 4, in particular to an electrode projection 25 extending radially 32 from the remaining second electrode 4, enclosing the second electrode 4 and sealing the interior 26 against a vacuum.

[0018] How it looks Fig. 2 and Fig. As can be seen in Figure 4, the housing 2 can be formed from several sub-housings. The housing 2 can, for example, have a switching chamber housing 14, which is made of or consists of a metal or alloy. The switching chamber housing 14 can completely enclose a switching chamber 13 in the circumferential direction 33, which is part of the interior 26. The first contact surface 7 and the second contact surface 8 are arranged in the switching chamber 13.

[0019] The housing 2 can, for example, comprise a first ceramic housing 17 arranged opposite the axial direction 31 of the switching chamber housing 14, and / or a second ceramic housing 18 arranged in the axial direction 31 of the switching chamber housing 14. The switching chamber housing 14 can be electrically isolated from other components of the vacuum switching tube 1 by means of the first ceramic housing 17 and / or the second ceramic housing 18. It is conceivable that the first ceramic housing 17 and / or the second ceramic housing 18 are formed in one piece or are formed from a plurality of partial ceramic housings 19 arranged side by side in the axial direction 31.

[0020] The housing 2 can, for example, comprise a first flange housing 15, which is arranged opposite the axial direction 31 to the first ceramic housing 17 and is attached to the first electrode 3, and a second flange housing 16, which is arranged in the axial direction 31 to the second ceramic housing 18 and is attached to the bearing 19. The first flange housing 15 and the first ceramic housing 17 can fully delimit a first flange chamber 11 in the circumferential direction 33, which is part of the interior 26. The second flange housing 16 and the second ceramic housing 18 can fully delimit a second flange chamber 12 in the circumferential direction 33, which is part of the interior 26.

[0021] The first flange chamber 11 and the second flange chamber 12 can have a smaller cross-section than the switching chamber 13, the cross-section having a normal that is parallel to the axial direction 31.

[0022] The vacuum switching tube 1 can have two chamber shields 20 attached to the switching chamber housing 14 and projecting into the interior 26, one of the two chamber shields 20 electrically shielding the first flange chamber 11 from switching chamber 13 and against metal vapor, and the other chamber shield 20 electrically shielding the second flange chamber 12 from switching chamber 13 and against metal vapor. The chamber shields 20 can be electrically connected to the switching chamber housing 14. Furthermore, for electrical shielding and shielding against metal vapor, a flange shield 21 can be attached to the first flange housing 15, which projects into the interior 26, and another flange shield 21 can be attached to the second flange housing 16, which also projects into the interior 26.In the area where the partial ceramic housings 19 meet, an intermediate shield 22 can be arranged for electrical shielding and for shielding against metal vapor, with the intermediate shield 22 projecting into the interior 26.

[0023] It is conceivable that in step c) the electrical ignition voltage is first applied to the first electrode 3 and the second electrode 4 in their contact state, and then the first electrode 3 and the second electrode 4 are brought into the spaced state, whereby the electrical ignition voltage remains applied to the first electrode 3 and the second electrode 4 while the first electrode 3 and the second electrode 4 are brought from the contact state to the spaced state. Alternatively, it is conceivable that in step c) the first electrode 3 and the second electrode 4 are first brought into the spaced state and then the electrical ignition voltage is applied to the first electrode 3 and the second electrode 4.

[0024] The electric field and the magnetic field can, for example, enclose an angle in the interior 26 which lies in a range of 70° to 90°, in particular from 80° to 90° or from 85° to 90°.

[0025] The procedure can include the following step: a) Performing a calibration by setting different pressures in the interior of a calibration vacuum switching tube, which has an interior. At each of the different pressures, a gas discharge is generated by applying an electric field and a magnetic field to the interior 26, and the electric current I of the gas discharge is measured. It is conceivable to perform the calibration with or without the direct current arc. The calibration vacuum switching tube can be a component different from the vacuum switching tube. The interior of the calibration vacuum switching tube can be identical in construction to the interior 26 of the vacuum switching tube 1, except for the presence of a through-hole through which the interior of the calibration vacuum switching tube can be supplied from outside the tube with a gas having the different pressures.The walls that define the interior of the calibration vacuum switching tube can be made of the same material or materials as the walls that define the interior 26 of the vacuum switching tube 1. The different pressures can, for example, be in a range of 10. -9 mbar up to 10 -3 mbar

[0026] Fig. 1 and Fig. Figure 2 illustrates a first embodiment for the pressure measuring device 40 and for the method. In the first embodiment, in step d), the electric field is a first electric field 23a, which is generated by applying an electric accelerating voltage between the first electrode 3 and the second electrode 4. This creates an anode, towards which the electrons released in the DC light source are accelerated, formed by either the first electrode 3 or the second electrode 4. The magnetic field can be a first magnetic field 24a. It is conceivable that no further electric field and / or magnetic field is provided. The first electric field 23a can, for example, be oriented in the axial direction 31, and the first magnetic field 24a can, for example, be oriented in the radial direction 32. It is conceivable that the electric accelerating voltage is greater than the electric ignition voltage.Furthermore, it is conceivable that the distance between the first electrode 3 and the second electrode 4 is further increased after the direct current arc has been generated. The pressure measuring device 40 can have a first voltage source 41, which is electrically conductively connected to the first electrode 3 and the second electrode 4 and is configured to generate the first electric field 23a. The pressure measuring device 40 can have a first magnet comprising a first coil 42 and / or a permanent magnet, wherein the first magnet is configured to generate the first magnetic field 24a.

[0027] Fig. 3 and Fig. Figure 4 illustrates a second embodiment for the pressure measuring device 40 and for the method. According to the second embodiment, in step d), the electric field is a second electric field 23b, which is formed by applying an electric accelerating voltage between the housing and one or both of the first electrode 3 and the second electrode 4. The magnetic field can be a second magnetic field 24b. The second electric field 23b can, for example, be oriented in the radial direction 32, and the second magnetic field 24b can, for example, be oriented in the axial direction 31.

[0028] It is conceivable that in step b) the application of the electrical ignition voltage creates a first electric field 23a, whereby a first magnetic field 24a, which has a different orientation than the second magnetic field 24b, is applied to the interior 26 in a region extending between the first electrode 3 and the second electrode 4, the first electric field 23a having a different orientation than the first magnetic field 24a. This prevents the electrons released in the DC light base from reaching the first electrode 3 or the second electrode 4 (depending on whether the first electrode 3 or the second electrode 4 forms the anode of the first electric field 23a) and thus from being available for the gas discharge. The first electric field 23a can have a different orientation than the second electric field 23b.The first electric field 23a can, for example, be oriented in the axial direction 31 and the first magnetic field 24a can, for example, be oriented in the radial direction 32.

[0029] The first electric field 23a and the first magnetic field 24a can enclose an angle in the interior 26 that lies in the range of 70° to 90°, in particular 80° to 90° or 85° to 90°. It is conceivable that the second electric field 23b and the second magnetic field 24b are applied before the electrical ignition voltage is applied. It is also conceivable that the first magnetic field 24a is applied before the electrical ignition voltage is applied.

[0030] The pressure measuring device 40 according to the second embodiment can have a first voltage source 41, which is electrically conductively connected to the first electrode 3 and the second electrode 4 and is configured to generate the first electric field 23a. Furthermore, the pressure measuring device 40 can have a second voltage source 43, which is electrically connected to the housing 2 and conductively connected to one or both of the first electrode 3 and the second electrode 4, and is configured to generate the second electric field 23b. The pressure measuring device 40 can have a first magnet comprising a first coil 42 and / or a first permanent magnet, wherein the first magnet is configured to generate the first magnetic field 24a.The pressure measuring device 40 can have a second magnet which has a second coil 44 and / or a second permanent magnet, wherein the second magnet is configured to generate the second magnetic field field 24b.

[0031] For both embodiments, the following applies: The first electric field 23a can, for example, form an angle with the axial direction 31 that lies in a range of 0° to 30°, in particular in a range of 0° to 15° or from 0° to 5°. The first magnetic field 24a can, for example, form an angle with the radial direction 32 that lies in a range of 0° to 30°, in particular in a range of 0° to 15° or from 0° to 5°. For the second embodiment, the following applies: The second electric field 23b can, for example, form an angle with the radial direction 32 that lies in a range of 0° to 30°, in particular in a range of 0° to 15° or from 0° to 5°. The second magnetic field 24b can, for example, enclose an angle with the axial direction 31 which lies in a range of 0° to 30°, in particular in a range of 0° to 15° or from 0° to 5°.

[0032] Fig. Figure 5 shows an example of a time-resolved current I, measured in step e). The current (in amperes) is plotted against time t. The time-resolved current I is characterized by the fact that, during the generation of the gas discharge, the current I rises steeply to a maximum and then falls more gradually. It is conceivable to determine the current at the maximum for evaluation purposes. It is also conceivable to filter the time-resolved current beforehand, for example, using a low-pass filter. Furthermore, it is conceivable to fit the time-resolved current I with one or more functions and to use one or more fitting parameters for the current. Fig.Figure 3 shows a time zero point t0, which is the first time at which both the electric field and the magnetic field are applied to the interior space 26. A rise time t1 is also shown, which is the first time at which the current I begins to rise. The difference t1-t0 represents a delay with which the gas discharge forms. In step c), when the ignition voltage is applied and the DC arc is generated, this delay is reduced. Reference symbol list 1 vacuum switching tube 2 cases 3 first electrode 4 second electrode 5 first connection 6 second connection 7 first contact surface 8 second contact surface 9 warehouses 10 bellows 11 first flange chamber 12 second flange chamber 13 Switching chamber 14 Switch chamber housings 15 first flange housing 16 second flange housing 17 first ceramic housing 18 second ceramic housing 19 partial ceramic housings 20-chamber screen 21 Flange screen 22 Intermediate screen 23a electric field 23b electric field 24a Magnetic field 24b Magnetic field 25 electrode protrusion 26 Interior 31 Axial direction 32 Radial direction 33 Circumferential direction 40 Pressure measuring device 41 first voltage source 42 first coil 43 second voltage source 44 second coil I electric current t time t0 Time zero t1 Rise time

Claims

[1] Method for measuring a pressure in a vacuum switching tube (1), comprising the steps: b) Providing the vacuum switching tube (1) which has a first electrode (3) and a second electrode (4) which have a contact state in which the first electrode (3) and the second electrode (4) are in contact with each other and a separation state in which the first electrode (3) and the second electrode (4) are separated from each other, and a housing (2) which defines an interior space (26) in which the first electrode (3) and the second electrode (4) are arranged and which maintains a vacuum in the interior space (26) so that in the separation state the first electrode (3) and the second electrode (4) are electrically isolated from each other by the vacuum; c) Applying an electrical ignition voltage between the first electrode (3) and the second electrode (4), thereby generating a direct current arc between the first electrode (3) and the second electrode (4) in their spaced state; d) Applying an electric field and a magnetic field to the interior (26) such that electrons released in the direct current arc are accelerated, producing a gas discharge that is different from the direct current arc, wherein the electric field in the interior (26) has an orientation different from the magnetic field; e) Measuring the electric current (I) of the gas discharge. [2] Method according to claim 1, wherein in step c) the electrical ignition voltage is first applied to the first electrode (3) and the second electrode (4) in their contact state and subsequently the first electrode (3) and the second electrode (4) are brought into the spaced-away state, whereby the electrical ignition voltage remains applied to the first electrode (3) and the second electrode (4). [3] Method according to claim 1, wherein in step c) first the first electrode (3) and the second electrode (4) are brought into the spaced-away state and then the electrical ignition voltage is applied to the first electrode (3) and the second electrode (4). [4] Method according to any one of claims 1 to 3, wherein the electric field and the magnetic field in the interior (26) enclose an angle which is in a range of 70° to 90°. [5] Method according to any one of claims 1 to 4, wherein in step d) the electric field is a first electric field (23a) formed by applying an electric accelerating voltage between the first electrode (3) and the second electrode (4). [6] Method according to claim 5, wherein the electrical acceleration voltage is greater than the electrical ignition voltage. [7] Method according to claim 5 or 6, wherein a distance between the first electrode (3) and the second electrode (4) is further extended after the direct current arc has been generated. [8] Method according to any one of claims 1 to 4, wherein in step d) the electric field is a second electric field (23b) formed by applying an electric accelerating voltage between the housing and one or both of the first electrode (3) and the second electrode (4). [9] Method according to claim 8, wherein in step b) a first electric field (23a) is formed by applying the electric ignition voltage, wherein a first magnetic field (24a) having an orientation different from the magnetic field is applied to the interior (26) in a region extending between the first electrode (3) and the second electrode (4), wherein the first electric field (23a) has an orientation different from the first magnetic field (24a). [10] Method according to claim 9, wherein the first electric field (23a) and the first magnetic field (24a) in the interior (26) enclose an angle which is in a range of 70° to 90°. [11] Method according to any one of claims 8 to 10, wherein the electric field and the magnetic field are applied before the electrical ignition voltage is applied. [12] Method according to any one of claims 1 to 11, wherein the method comprises the step: a) Performing a calibration by setting different pressures in the interior of a calibration vacuum switching tube having an interior, generating a gas discharge at each of the different pressures by applying the electric field and the magnetic field to the interior (26) and measuring the electric current (I) of the gas discharge. [13] Method according to claim 12, wherein the interior of the calibration vacuum switching tube is identical in construction to the interior (26) of the vacuum switching tube (1) except for the presence of a through-hole, via which the interior of the calibration vacuum switching tube can be supplied from outside the calibration vacuum switching tube with a gas having different pressures. [14] Pressure measuring device configured to perform a method according to any one of claims 1 to 13.

Images