Method and device for conditioning contact pieces for electrodes of a vacuum interrupter

Abstract

The invention relates to a method for conditioning contact pieces (12, 14) for electrodes (16, 18) of a vacuum interrupter (20) by generating an arc (42) between the contact pieces (12, 14), which are arranged spaced apart along an axis (24), wherein, during the conditioning, the arc (42) is moved in a deliberate manner over a variable transverse magnetic field (40). It is provided that, during the conditioning, the arc (42) is deliberately made more diffuse by means of an adjustable longitudinal magnetic field (16). The invention also relates to a corresponding device (10) for conditioning contact pieces (12, 14) for electrodes (16, 18) of a vacuum interrupter (20), in particular for carrying out the stated method.

Description

[0001] The invention is based on a method for carrying out a device for conditioning contact pieces for electrodes of a vacuum interrupter by generating an arc between the contact pieces arranged at a distance along an axis, wherein the arc is moved in a targeted manner during conditioning via a variable transverse magnetic field.

[0002] The invention further relates to a device for conditioning contact pieces for electrodes of a vacuum interrupter by generating an arc between the contact pieces arranged at a distance along an axis. The device comprises a coil arrangement with at least one coil or a permanent magnet arrangement with at least one permanent magnet for generating a variable transverse magnetic field, by means of which the arc can be moved in a targeted manner during conditioning. Devices for conditioning contact pieces for electrodes of vacuum interrupters are known, for example, from DE 10 201 002 642 A1. B. from DE 19714 655 A1, from DE 26 00 683 A1 and from GODECHOT X ET AL: "Investigation of current conditioning process for vacuum interrupters", 2016 27TH INTERNATIONAL SYMPOSIUM ON DISCHARGES AND ELECTRICAL INSULATION IN VACUUM (ISDEIV), IEEE, Vol. 2, 18 September 2016 (2016-09-18), pages 1-4, XP033015037, DOI: 10.1109 / DEIV.2016.7763981.

[0003] In addition to the quality of the vacuum, the quality of the surfaces of the electrode contacts plays a crucial role in determining the dielectric strength of an electrode arrangement in a vacuum. Since technical surfaces typically contain defects or micro-peaks, these surfaces must be specially treated after the vacuum interrupters have been installed to achieve the desired dielectric strength. Typically, electrical voltages are applied to the vacuum interrupters and arcing is deliberately induced. The arcs created during these arcing melt or vaporize the defects on the surfaces, thereby gradually increasing the dielectric strength.

[0004] Another method for conditioning electrode surfaces is to treat the surface to be conditioned with an arc for an extended period of time (current conditioning). This typically involves using low voltages, as this eliminates the need to generate a flashover. Instead, the current flow begins when the contacts are closed, and an arc is only established after the contacts open. In this case, the externally applied voltage only needs to cover the voltage requirements of the arc.

[0005] To date, current conditioning has attempted to achieve uniform and complete melting of the contact discs by selecting suitable parameters (contact stroke, current strength, number of pulses, pulse duration, polarity reversal). The goal is not only to increase the dielectric strength of the contact gap, but also to reduce the disruptive X-ray emissions generated by the contact pairs. If the arc movement is not actively controlled, it is largely random. Therefore, a large charge transfer can occur during the current conditioning procedure until the contact surfaces have been sufficiently melted. While an arc burns in a vacuum, metal vapor is generated, which in turn precipitates on the surfaces of the vacuum switch.If this metal vapor condenses on the ceramic insulators, it can lead to a dielectric degradation of the vacuum interrupter, which counteracts the purpose of the conditioning or possibly reduces the service life of the vacuum interrupter.

[0006] The document DE 19 714 655 C2 describes a method for conditioning contact pieces of electrodes of a vacuum interrupter, in which the arc is moved in a targeted manner by means of a rotating transverse field.

[0007] This transverse magnetic field allows the position / movement of the arc on the surface of the contact piece to be conditioned to be precisely controlled. This ensures that the center of gravity of the arc traverses a selected surface area along a specific path. However, the path can only be controlled with a certain degree of precision, which limits the quality of the conditioning. This limitation is particularly noticeable with high-current arcs.

[0008] The invention is based on the object of providing a method and a device for conditioning such contact pieces which overcome the stated difficulties.

[0009] The object is achieved according to the invention by the features of the independent claims. Advantageous embodiments of the invention are the subject of the dependent claims.

[0010] In the device according to the invention for conditioning contact pieces for electrodes of a vacuum interrupter by generating an arc between the contact pieces arranged at a distance along an axis, in which the device has a coil arrangement with at least one coil or a permanent magnet arrangement with at least one permanent magnet for generating a variable transverse magnetic field, by means of which the arc can be moved in a targeted manner during conditioning, it is provided that the device further has a coil arrangement with at least one coil or a permanent magnet arrangement with at least one permanent magnet for generating a variable longitudinal magnetic field, by means of which the arc can be made more diffuse in a targeted manner during conditioning.

[0011] The variable transverse magnetic field allows the device to precisely control the position / movement of the arc on the surface of the contact piece to be conditioned. This ensures that the arc traverses a selected surface area along a specific path. For a more diffuse, i.e., wider, arc, an overlap area of ​​the path can be adjusted. This ensures that the surface of the contact piece in question is traversed as completely as possible by the arc, while at the same time ensuring a fairly uniform melting.

[0012] Finally, the device according to the invention advantageously further comprises a direct current source for generating the arc. The resulting arc is preferably a high-current arc with a current intensity I in the range of 2 kA ≤ I ≤ 100 kA. Especially for such high-current arcs, it is important to have a lower arc diffusion in an overlapping edge region. The direct current source is designed for a corresponding current intensity (2 kA ≤ I ≤ 100 kA).

[0013] The device is, in particular, a device for carrying out a method described below. The features mentioned in connection with the embodiments of the method shall also apply to the device, and vice versa.

[0014] In the method according to the invention for implementation on a device for conditioning contact pieces for electrodes of a vacuum interrupter by generating an arc between the contact pieces arranged at a distance along an axis, in which the arc is deliberately moved during conditioning via a variable transverse magnetic field, it is provided that the arc is deliberately made more diffuse during conditioning via an adjustable longitudinal magnetic field.

[0015] The variable transverse magnetic field precisely controls the position / movement of the arc on the surface of the contact piece to be conditioned. This ensures that the arc traverses a specific surface area along a specific path. The contact area of ​​the arc with the surface of the contact piece to be conditioned can be larger than the length of the path.

[0016] With a more diffuse, i.e., wider, arc, the contact area of ​​the arc with the surface of the contact piece is also larger. This ensures that the surface of the contact piece is covered / traversed by the arc as completely as possible, while at the same time, the melting is fairly uniform.

[0017] In particular, the arc can be set so diffuse that an almost complete coverage - and thus melting - of the contact surfaces occurs during the conditioning process.

[0018] The terms "longitudinal field" and "transverse field" refer to the (imaginary) axis on which the contact pieces are arranged. For many vacuum interrupters, this coincides with their longitudinal axis.

[0019] According to a preferred embodiment of the invention, the arc is a high-current arc with a current intensity I in the range of 2 kA ≤ I ≤ 100 kA. Such a high-current arc preferably has a current intensity I of a few kA to several tens of kA (kA: kiloamperes). Such high-current arcs generally have a smaller contact area with the contact piece to be conditioned. This contact area can now be enlarged using the longitudinal field.

[0020] According to a further preferred embodiment of the invention, the variable transverse magnetic field is a rotating transverse magnetic field. Such a rotating transverse magnetic field is well known from the aforementioned patent specification DE 19 714 655 C2.

[0021] According to yet another preferred embodiment of the invention, the transverse magnetic field and / or the longitudinal magnetic field is generated by means of a coil arrangement comprising at least one coil. The at least one coil can be an air-core coil and / or a cored coil.

[0022] In particular, it is intended that the rotating transverse magnetic field be a two-phase or three-phase rotating magnetic field. Two or three coil arrangements are required to generate such rotating fields. For example, in a two-phase rotating magnetic field, two coil arrangements are arranged so that the center axes of the two coil arrangements are at an angle of 90° to each other. The currents flowing in both coil arrangements can be 90° out of phase with each other, creating the two-phase rotating magnetic field.

[0023] Alternatively or additionally, it is advantageously provided that the transverse magnetic field and / or the longitudinal magnetic field is generated by means of a permanent magnet arrangement with at least one permanent magnet.

[0024] Furthermore, it is preferably provided that the current flow begins when the contacts are closed, and the arc only establishes after the contacts open. This is typical of the so-called current conditioning described above.

[0025] According to yet another preferred embodiment of the invention, at least one of the contact pieces is designed as a contact disk. The use of contact disks for the electrodes of vacuum interrupters has proven successful.

[0026] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of an embodiment, which is explained in more detail in connection with the drawing. Fig. a device for conditioning contact pieces for electrodes of a vacuum interrupter according to an embodiment of the invention in a schematic representation.

[0027] The figure shows a schematic representation of a device 10 for conditioning contact pieces 12, 14 (in short: conditioning device) for electrodes 16, 18 of vacuum interrupters 20. In the example shown here, the contact pieces 12, 14 can be conditioned using the conditioning device 10 in fully assembled vacuum interrupters 20. The contact pieces 12, 14, which are only shown schematically here, are designed in particular as contact disks. Alternatively, it would also be conceivable for the individual contact piece 12 to be conditioned to be mounted in a corresponding vacuum chamber of the device 10.

[0028] The vacuum interrupter 20 shown here essentially comprises a cylindrical housing 22 made of insulating material, which extends along a longitudinal axis 22 and is closed at each of the two corresponding ends by a metal cover 26, 28. One of the electrodes 16 is fixedly attached to one of the metal covers 26. This electrode 16 is the fixed electrode with the fixed contact piece 12.

[0029] Attached to the lower cover 28 is one end of a bellows 30, the other end of which is connected to the electrode 18, which is designed as a movable electrode and supports the movable contact piece 14. An approximately cylindrical shield 32 is located within the housing 22.

[0030] A current source 34 is electrically connected to the two electrodes 16, 18, with which direct current of both polarities can be generated (direct current source).

[0031] The device 10 further comprises a coil arrangement configured as a pair of coils. Coils 36, 38 of this pair of coils are located on both sides of the housing 22. These coils run parallel to each other or their axes are aligned, thereby generating a transverse field 40 that runs from the left coil 36 to the right coil 38 in the direction of the arrow.

[0032] When a diffuse arc 42 is created between the open contact pieces 12, 14 with a suitable current intensity I, the diffuse arc 42 melts and vaporizes any type of dirt particles located on the surface of the corresponding contact piece 12 or contact pieces 12, 14, and moves them outward onto the shield 32, which has a gettering effect, where they precipitate. Furthermore, parts of the contact surface of the two contact pieces 12, 14 are also melted and vaporized, through which metal vapor the pure copper parts, for example, of the electrodes 16, 18, are coated with the contact material. In a particularly advantageous embodiment, the contact material is Cu / Cr, which is present as a sintered structure.

[0033] For conditioning, the electrodes 16, 18 of the vacuum interrupter 20 are supplied with a direct current, first with one polarity and then with the other, so that the current flow in the arc 42 runs in one direction and then in the other direction - one after the other.

[0034] Due to the transverse field 40, the individual arc sections of the diffuse arc 42 are moved over the surface of the corresponding contact piece 15, thereby enabling a systematic removal of the dirt particles over the entire surface.

[0035] The coils 36, 38 can also be arranged in the vacuum interrupter 20 such that the center axes of the two coils 36, 38 are at an angle of 90° to each other. The currents flowing in both coils can be phase-shifted by 90° to each other, creating the "two-phase" rotating magnetic field. Such an arrangement of the coils 36, 38 is known from the aforementioned DE 197 14 655 C2. A three-phase rotating field can also be generated in a corresponding manner. In this case, the coils 36, 38 are arranged in a fixed (stationary) manner, unlike the illustration in the figure.

[0036] In the example shown in the figure, the coils 36, 38 of the coil pair are arranged on a base 44 rotatably mounted about the axis 24 and rotatably mounted about the vacuum interrupter 20 via corresponding arms 46, 48. The base 44 is fixedly mounted on a rotary support 50, which in turn is rotatably mounted via a rotary bearing 52 and driven by a drive motor 54.

[0037] By means of such a mechanical rotating arrangement with the components base 44, arms 46, 48, rotating support 50, rotating bearing 52, and drive motor 54, a correspondingly rotating transverse field 40 can be generated not only by means of a coil arrangement with coils 36, 38 but also by means of a permanent magnet arrangement (not shown here) with at least one permanent magnet. A corresponding structure is also known from the aforementioned DE 197 14 655 C2.

[0038] In the patent specification DE 197 14 655 C2 mentioned at the beginning, it is further mentioned that good conditioning results can be achieved with a current intensity of the direct current generated by the direct current source 34 of approximately 0.1 kA to 2 kA, an exposure time at which the arc 24 is to burn of between 0.5 seconds and 200 seconds and a distance between the two contact pieces 12, 14 of between 1 mm and 3 mm.

[0039] If you now want to use a high-current arc 42 with significantly more than 2 kA, e.g. with 2.5 kA ≤ I ≤ 100 kA, you have to increase the diffusivity of this high-current arc 42 for conditioning.

[0040] For this purpose, the device 10 has a further coil arrangement, which in this example is also designed as a coil pair. The coil arrangement / coil pair has two coils 56, 58 for generating a variable longitudinal magnetic field 60, by means of which the arc 42 can be made more diffuse, i.e., expanded, during conditioning. The axes of the coils 56, 58 of this further coil arrangement are aligned with each other and with the axis 24 of the vacuum interrupter 20.

[0041] The diffusivity of the high-current arc 42 is adjusted for conditioning via the strength of the generated longitudinal field 60.

[0042] In addition to the illustrated and previously mentioned components, the device 10 further includes power sources (not shown) for the coils 36, 38; 56, 58 and a control device (also not shown) for the coordinated execution of the conditioning. Such a control device is also referred to as a control unit. This control device controls the various power sources, including the direct current source 34.

[0043] In the following, key aspects of the invention will be summarized once again in other words: In order to achieve uniform conditioning in a relatively short time, the arc movement is specifically controlled by external magnetic fields 40. Particularly suitable for this purpose are rotating magnetic fields (two-phase or three-phase) directed radially to the desired direction of the arc. This method is particularly advantageous because the converted charge (current I x time) is significantly reduced during conditioning, and consequently, the vapor deposition of ceramic insulators is also significantly reduced.

[0044] Furthermore, the diffusivity of a high-current arc 42 (a few kA to several tens of kA) for conditioning the contact pieces 12, 14 is increased by an additional axial magnetic field 60. A higher diffusivity of the arc 42 results in almost complete coverage (and thus melting) of the contact surfaces during the conditioning process.

[0045] The conditioning is in particular a so-called current conditioning. List of reference symbols:

[0046] 10Conditioning device 12Contact piece 14Contact piece 16Electrode (fixed) 18Electrode (movable) 20Vacuum interrupter 22Housing 24Shaft 26Cover 28Cover 30Bellows 32Shielding 34DC source 36Radial coil 38Radial coil 40Transverse field 42Arc 44Base 46Arm 48Arm 50Rotary support 52Rotary bearing 54Drive motor 56Axial coil 58Axial coil 60Longitudinal field

Claims

1. Device (10) for conditioning contact pieces (12, 14) for electrodes (16, 18) of a vacuum interrupter (20) by generating an arc (42) between the contact pieces (12, 14) arranged spaced apart along an axis (24), wherein the device (10) has a coil arrangement with at least one coil (36, 38) or a permanent magnet arrangement with at least one permanent magnet for generating a variable transverse magnetic field (40), by means of which the arc (42) is specifically movable during the conditioning, characterized in that the device (10) also has a coil arrangement with at least one coil (56, 58) or a permanent magnet arrangement with at least one permanent magnet for generating a variable longitudinal magnetic field (60), by means of which the arc (42) can be specifically made more diffuse during the conditioning.

2. Device according to Claim 1, characterized by a direct current source (34) for generating the arc (42).

3. Method performed on a device for conditioning contact pieces (12, 14) according to one of the preceding claims, for electrodes (16, 18) of a vacuum interrupter (20) by generating an arc (42) between the contact pieces (12, 14) arranged spaced apart along an axis (24), wherein the arc (42) is specifically moved by way of a variable transverse magnetic field (40) during the conditioning, wherein the arc (42) is specifically made more diffuse by way of an adjustable longitudinal magnetic field (60) during the conditioning.

4. Method according to Claim 3, characterized in that the arc is an arc with a current strength I in the range of 2 kA ≤ I ≤ 100 kA.

5. Method according to Claim 3 or 4, characterized in that the variable transverse magnetic field (40) is a rotating transverse magnetic field (40).

6. Method according to Claim 5, characterized in that the rotating transverse magnetic field (40) is a two-phase or three-phase rotating magnetic field.

7. Method according to one of Claims 3 to 6, characterized in that the transverse magnetic field (40) and / or the longitudinal magnetic field (60) is generated by means of a coil arrangement with at least one coil (36, 38, 56, 58).

8. Method according to one of Claims 3 to 7, characterized in that the transverse magnetic field (40) and / or the longitudinal magnetic field (60) is generated by means of a permanent magnet arrangement with at least one permanent magnet.

9. Method according to one of Claims 3 to 8, characterized in that the current flow begins when the contact pieces (12, 14) are closed and the arc is only established when the contact pieces have opened.

10. Method according to one of Claims 3 to 9, characterized in that at least one of the contact pieces (12, 14) is formed as a contact disc.

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