Vacuum interrupter

Abstract

A vacuum interrupter (100) includes a stationary contact (110), a moveable contact (120) being moveable relative to the stationary contact along an axis (A), a vacuum-tight housing accommodating the stationary contact (110) and the moveable contact (120), and a field controller (150) including a conductive shielding part (151) and an abutment part (155) provided at a distance from the shielding part (151). The housing includes a container (130) made of an insulating material, the container (130) extending along the axis (A) and having an axial end (135), a lid part (140) made of a conductive material, the lid part (140) extending in the axial direction (A) at least up to the axial end (135) of the container (130), an outer circumferential surface (146) of the lid part (140) extending, at least in the vicinity of the axial end (135) of the container (130), at a shorter radial distance (r2) than an outer circumferential surface (136) of the container (130), thus creating a radial step (190), and a positioning surface (135, 145), The abutment part (155) abuts on the positioning surface (135, 145) such that the shielding part (151) at least partially shields the radial step (190) while being spatially separated from the axial end (135).

Description

TECHNICAL FIELD

[0001] The present disclosure generally relates to vacuum interrupters.BACKGROUND

[0002] In vacuum interrupters, in particular those for medium voltage and high voltage applications, typically multiple materials are used. For example, a gas-tight enclosure or container that houses a stationary and a moveable contact is made of a ceramic material. Lids at the axial ends of the container are typically made of a conductive material such as metal and joined to the container. On the exterior side of the lids and the container, a gas (typically air) is present. In this region, three different materials (the insulating material of the container, the conductive material of the lid and the surrounding gas) abut on each other, and a so-called "triple point" is formed. Electric field lines tend to concentrate in such a "triple point" area, i.e. the dielectric stress is comparatively high. There is a desire to alleviate the dielectric stress.SUMMARY

[0003] According to an aspect of the present disclosure, a vacuum interrupter is provided. The vacuum interrupter includes a stationary contact, a moveable contact, a vacuum-tight housing, and a field controller. The moveable contact is moveable relative to the stationary contact along an axis. The vacuum-tight housing accommodates the stationary contact and the moveable contact. The housing includes a container, a lid part, and a positioning surface. The container is made of an insulating material. The container extends along the axis. The container includes an axial end. The lid part is made of a conductive material. The lid part extends in the axial direction at least up to the axial end of the container. An outer circumferential surface of the lid part extends - at least in the vicinity of the axial end of the container - at a shorter radial distance than an outer circumferential surface of the container. By the different radial distances, a radial step is formed. The field controller includes a conductive shielding part and an abutment part. The abutment part is provided at a distance from the shielding part. The abutment part abuts on the positioning surface such that the shielding part - at least partially - shields the radial step. The shielding part is spatially separated from the axial end.

[0004] Abutting, as used herein, may include any kind of physical contact between the abutment part and the positioning surface, and may typically include a close contact between these parts.

[0005] In embodiments, the field controller has substantially a round plate shape. Round, as used herein, includes a substantially circular shape or an oval shape. For example, the field controller has a "cup" shape in which a substantially round plate having a central hole includes an annular rim extending axially away from the round plate to form the shielding part.

[0006] In embodiments, the positioning surface is formed on the lid part. For example, the field controller having a substantially round plate shape, such as a "cup" shape, is a lid part in which the substantially round plate having a central hole includes an annular rim extending axially away from the round plate, and the substantially round plate may at least partially form the positioning surface. The abutment part may then typically be formed as an abutment surface, and the abutment surface may be in close physical contact with the positioning surface. This may help to achieve a particularly precise positioning of the field controller, and in particular the shielding part thereof, relative to the positioning surface.

[0007] In embodiments, the field controller has substantially a ring shape. A ring shape, as used herein, includes a substantially circular circumferential shape or an oval circumferential shape. For example, the field controller is a ring surrounding an exterior surface, or outer circumferential surface, of the lid part.

[0008] In embodiments, the positioning surface at least partially coincides with the axial end. For example, the field controller having substantially a ring form, for example a ring surrounding the exterior surface of the lid part, abuts, at the abutment part, on the axial end, wherein the axial end functions as the positioning surface.

[0009] In embodiments, the shielding part includes a bulge. For example, the bulge protrudes, or bulges, radially outwards. Typically, a bulge has a substantially convex shape and may also be described as a round or rounded rim substantially without any sharp edges. The bulge may help to alleviate a concentration of dielectric field lines, i.e. a dielectric stress.

[0010] In embodiments, the shielding part extends beyond the radial step. That is, in the axial direction, the shielding part "climbs" over the radial step area without having a physical contact with the radial step area. In other words: When viewing the radial step substantially orthogonally in the radial direction from the outside of the vacuum interrupter, the shielding part covers the radial step without any physical contact with the radial step. Such a configuration may improve the shielding even further.

[0011] In embodiments, the vacuum interrupter further includes a non-conductive housing that accommodates the container, the metal flange, and the conductive shield. It has been found that such a non-conductive housing may have an impact on the field line concentration, i.e. the dielectric stress, in the "triple point" are described above. The conductive shield may help to alleviate the dielectric stress even when such a non-conductive housing is present.

[0012] In embodiments, the container or the lid part or both have a substantially cylindrical shape. A cylindrical shape may facilitate the manufacturing, the mounting, or both, of the container and the lid part.

[0013] In embodiments, the container is made of a ceramic material. Ceramics typically have excellent insulative properties and may thus be preferable particularly in medium voltage or high voltage applications.

[0014] In embodiments, the shielding part is made of a metal material. Metals typically have excellent conductive properties and may thus be preferable when it comes to shielding dielectric stress arising from an application of the vacuum interrupter to medium voltage or high voltage.

[0015] In embodiments, the lid part has a galvanic connection with the field controller. Typically, the galvanic connection extends through a body part of the field controller to the shielding part, and the shielding part of the field controller has, via the galvanic connection, substantially the same electrical potential as the lid part. For example, when the field controller has a substantially round plate shape, such as a "cup" shape, and the positioning surface is formed on the lid part, the galvanic connection may be imparted by the positioning surface abutting on the abutment part, e.g. by being in close physical contact with each other.

[0016] In embodiments, the vacuum interrupter includes two lids, that is one at each of its axial ends. The vacuum interrupter further includes a first field controller having substantially a ring shape, as described herein. The vacuum interrupter further includes a second field controller having substantially a round plate shape, as described herein. The first field controller is arranged at one of the lids, and the second field controller is arranged at the other one of the lids. Typically, the first field controller is arranged on the moving side contact side, and the second field controller is arranged on the stationary contact side of the vacuum interrupter.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Fig. 1 shows a sectional view of main parts of a vacuum interrupter 100. Fig. 2 shows an enlarged sectional view of a part of Fig. 1. Fig. 3 shows a perspective side view of a vacuum interrupter including a first field controller and a second field controller. Fig. 4 shows a perspective oblique top-side view of a vacuum interrupter to which a first field controller is being mounted. Fig. 5 shows a perspective oblique top-side view of a vacuum interrupter after mounting of the first field controller in Fig. 4 is finished. Fig. 6 shows a perspective view of a part of a field controller. Fig. 7 shows a sectional view of the part in Fig. 6. DETAILED DESCRIPTION

[0018] Technology is described hereinafter with reference to the figures, in which aspects exemplary embodiments are shown. The claimed invention may, however, be embodied in different forms and should not be construed as being limited to the embodiments set forth herein. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with respect to the description of each figure. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the claimed invention or as a limitation on the scope of the claimed invention. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment aspect is not necessarily limited to that embodiment aspect and can be practiced in any other embodiments aspects even if not so illustrated, or if not so explicitly described. The features, functions, and advantages may be achieved independently in various embodiments manners or may be combined in yet other embodiments.

[0019] Before describing exemplary embodiments aspects illustratively depicted in the several figures, a general introduction is provided to further understanding. A vacuum interrupter (VI) is typically used in a wide variety of switchgear, e.g. compact medium and high voltage switchgear, insulated or not by gas. A part of a vacuum interrupter 100 is shown e.g. in Fig. 1.

[0020] The vacuum interrupter 100 includes a stationary contact 110 (a fixed contact) and a moveable contact 120 (a non stationary contact) opposing each other to form a contacting area. By moving the moveable contact away from the stationary contact, a space in between the contacts in the contacting area increases and interrupts a current flowing through the contacts 110, 120. The contacts 110, 120 are accommodated in a vacuum-tight housing including a container 130 of an insulating material extending along an axis A, and lid parts 140 of a conductive material on each axial-end side of the container 130. In an area where a lid part 140, the container 130, and the surrounding atmosphere along the outer circumferential surfaces of the lid part 140 and the container 130 meet, a so-called "triple point" of materials each having different dielectric properties is formed. Electric field lines tend to concentrate in these "triple point" areas.

[0021] In conventional vacuum interrupters, dielectric tests showed that discharges (lightning impulses) tend to occur at welding or brazing lines used for joining the container 130 and the lid part 140. It has been found by the inventor that mainly that part of the brazing / welding material that tends to splash / spill over the nonconductive part of the vacuum-tight housing (the container 130 made e.g. of a ceramic material) contributes to these undesired discharges in dielectric tests.

[0022] Fig. 1 shows a schematic sectional view of an embodiment of a vacuum interrupter 100 according to the present disclosure. Fig. 2 shows an enlarged view of a lower-left corner part of the vacuum interrupter 100 shown in Fig. 1; for convenience and better overview, some parts have been omitted in Fig. 2. Furthermore, for convenience, Figs. 1 and 2 are described here in common.

[0023] For example, a dielectric medium (insulating gas) used in the vacuum interrupter 100 is a gas having a global warming potential lower than that of SF 6 . For example, the dielectric medium comprises one or more of air, dry air, nitrogen (N 2 ), carbon dioxide (CO 2 ). In an example, the dielectric medium is one of air, dry air, N 2 , CO 2 . In another example, the dielectric medium is a mixture of two or three of the following: N 2 , oxygen (O 2 ), CO 2 .

[0024] The container 130 extends along the axis A and has an axial end 135. A lid part 140 on the stationary-contact side is made of a conductive material and extends in the direction of the axis A (the axial direction) to reach the container 130, i.e. it extends at least up to the axial end 135 of the container 130. An outer circumferential surface 146 of the lid part 140 extends at a shorter radial distance r2 than an outer circumferential surface 136 of the ceramic container 130. That is, when moving along any of the outer circumferential surfaces 136, 146 on the axis towards the respective other element 130, 140, a step in the radial direction (a radial step 190) is formed. Note that the radial step 190 need not necessarily be a 90° directional change, but may include slightly smoother transitions as well. At or in the vicinity of the radial step 190, a triple point is formed.

[0025] The housing includes a positioning surface. In the example of Figs. 1 and 2, a positioning surface 145 is formed as an element of the lid part 140. The vacuum interrupter 100 further includes a field controller 150. The field controller 150 has a conductive shielding part 151 and an abutment part 155. In the example of Figs. 1 and 2, the field controller is formed of one piece and is made of a metal material, and has substantially a plate shape or cup shape.

[0026] The abutment part 155 is provided at a distance from the shielding part 151. The abutment part 155 abuts on the positioning surface 145. In this way, the shielding part 151 shields the radial step 190 at least partially while being spatially separated from the axial end 135. The shielding part may be beneficial in alleviating the dielectric stress occurring in the triple point area, i.e. at or in the vicinity of the radial step 190.

[0027] In the plate-shape configuration of Figs. 1 and 2, the positioning surface 145 is in close contact with the abutment part 155, forming a low-resistant galvanic connection between the two parts. Thus, the field controller 150, and specifically the shielding part 151, has substantially the same electrical potential as the lid part 140.

[0028] In the plate-shape configuration of Figs. 1 and 2, the conductive shielding part 151 is formed as a bulge, and the bulge extends, or bulges, radially outward. Note that the bulge may also extend beyond the radial step 190 without physically contacting, or touching, the radial step 190.

[0029] The shielding part 151 may be beneficial in shielding the radial step 190 area and alleviate the dielectric stress in this triple point area.

[0030] Figs. 3 through 5 show an embodiment of a vacuum interrupter 100 according to the present disclosure. In Fig. 3, the stationary-contact-side field controller (a second field controller) as described above in connection with Figs. 1 and 2 has been given the reference numeral 150-2, while another field controller 151-1 on the moving-contact side (a first field controller) is provided (denoted simply as field controller 150 in Figs. 4 and 5).

[0031] The field controller 150 has a shielding part 151 in the form of a bulge, and an abutment part 155. In Figs. 4 and 5, the positioning surface 135 on the moving-contact side coincides with the axial end 135 of the container 130. The abutment part 155 of the field controller 150 abuts on the axial end 135, i.e. the positioning surface 135. The abutment part 155 is provided at a distance from the shielding part 151. The abutment part 155 abuts on the positioning surface 145. In this way, the shielding part shields the radial step 190 at least partially while being spatially separated from the axial end 135.

[0032] Note that it is possible to provide the vacuum interrupter 100 with both the first field controller 150-1 and the second field controller 150-2, as shown in Fig. 3. It is also possible to provide the vacuum interrupter 100 with only one of the first field controller 150-1 or the second field controller 150-2. For example, it is conceivable to provide the vacuum interrupter 100 with only one field controller 150-1 or 150-2 at a triple point that is found to be a "weaker" one of the possible triple points, e.g. one that suffers from more disadvantageous dielectric stress when field controller 150-1, 150-2 is not provided. In an example, an experiment or a simulation is carried out on a vacuum interrupter 100 without a field controller 150-1, 150-2 to find the "weakest" triple point. Then, the vacuum interrupter 100 may be equipped with only one field controller 150-1, 150-2 according to the finding.

[0033] Fig. 4 illustrates a top-side view of a vacuum interrupter 100 to which a ring-shaped field controller 150 is being mounted. In the transition area from the lid 140 to the container 130, the radial step 190 is formed, as described above and visible, e.g., in Fig. 2. In Fig. 4, the axial end 135 of the container 130 (here, an axial end 135 surface) serves as the positioning surface for ensuring a proper positioning of the field controller 150. The field controller 150 in Fig. 4 is composed of two half-ring parts, one of which is shown in Fig. 6, but this is only an example and not a limitation. A split pin 157 (see Fig. 4) is inserted in a pin hole 156 (see Fig. 6) for assembling the two half-ring parts, resulting in the assembly shown in Fig. 5. Note that the split pin 157 and the pin hole 156 are merely examples, and any other suitable way of assembling the half-ring parts is possible, e.g., but not limited to, a bolt and a bolt hole. As shown e.g. in the perspective view of Fig. 6 and in the cross-sectional view of Fig. 7, the conductive shielding part 151 is formed as a bulge, and the bulge extends, or bulges, radially outward. Note that the bulge may also extend beyond the radial step 190 without physically contacting, or touching, the radial step 190.

[0034] The abutment part 155 is provided at a distance from the shielding part 151. In the ring-type configuration of Figs. 4 through 7, the abutment part 155 abuts on the axial end 135 functioning as the positioning surface. In contrast to the shielding part 155, the abutment part 155 has no or only a minute influence on the electric field lines in the radial step 190 area. For example, the abutment part 155 has a comparatively thin or narrow configuration compared with the shielding part 151, whereas the shielding part 151, e.g. formed as a bulge, contributes significantly to the shaping of the electric field lines in the radial step 190 area, i.e. alleviating the dielectric stress.

[0035] As an example, configuring a vacuum interrupter 100 as described herein may create about 0.2 bar pressure margin for conducting lightning impulse tests in dry air. In some test configurations, the vacuum interrupter was equipped with a field controller 150 as described herein, and in some other test configurations, the vacuum interrupter was not equipped with such a field controller. It was found that the vacuum interrupter that was equipped with the field controller 150 passed the lightning impulse tests while the vacuum interrupter without the field controller did not pass some of the tests.

[0036] Although particular embodiments have been shown and described, it will be understood that it is not intended to limit the claimed inventions to the preferred embodiments, and it will be obvious to those skilled in the art that various changes and modifications may be made without department from the spirit and scope of the claimed inventions. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed inventions are intended to cover alternatives, modifications, and equivalents.

Claims

1. A vacuum interrupter (100), comprising - a stationary contact (110); - a moveable contact (120) being moveable relative to the stationary contact along an axis (A); - a vacuum-tight housing accommodating the stationary contact (110) and the moveable contact (120), the housing comprising - a container (130) made of an insulating material, the container (130) extending along the axis (A) and having an axial end (135); - a lid part (140) made of a conductive material, the lid part (140) extending in the axial direction (A) at least up to the axial end (135) of the container (130), an outer circumferential surface (146) of the lid part (140) extending, at least in the vicinity of the axial end (135) of the container (130), at a shorter radial distance (r2) than an outer circumferential surface (136) of the container (130), thus creating a radial step (190); and - a positioning surface (135, 145), the vacuum interrupter (100) further comprising: - a field controller (150) including a conductive shielding part (151) and an abutment part (155) provided at a distance from the shielding part (151), wherein the abutment part (155) abuts on the positioning surface (135, 145) such that the shielding part (151) at least partially shields the radial step (190) while being spatially separated from the axial end (135).

2. The vacuum interrupter (100) according to claim 1, wherein the field controller (150) has substantially a round plate shape.

3. The vacuum interrupter (100) according to any one of the preceding claims, wherein the positioning surface (145) is formed on the lid part (140).

4. The vacuum interrupter (100) according to claim 1, wherein the field controller (150) has substantially a ring shape.

5. The vacuum interrupter (100) according to any one of claims 1 or 4, wherein the positioning surface (135) at least partially coincides with the axial end (135).

6. The vacuum interrupter (100) according to any one of the preceding claims, wherein the shielding part (151) includes a bulge.

7. The vacuum interrupter (100) according to any one of the preceding claims, wherein the shielding part (151) extends, in the axial direction (A), beyond the radial step (190).

8. The vacuum interrupter (100) according to any one of the preceding claims, further comprising a non-conductive housing (180) accommodating the container (130), the metal flange (140) and the conductive shield (150).

9. The vacuum interrupter (100) according to any one of the preceding claims, wherein the container (130) and / or the lid part (140) has a substantially cylindrical shape.

10. The vacuum interrupter (100) according to any one of the preceding claims, wherein the container (130) is made of a ceramic material.

11. The vacuum interrupter (100) according to any one of the preceding claims, wherein the shielding part (151) is made of a metal material.

12. The vacuum interrupter (100) according to any one of the preceding claims, wherein the lid part (140) has a galvanic connection with the field controller (150).

13. The vacuum interrupter (100) according to any one of the preceding claims, including, at each axial end, a respective lid (140), and including a first field controller (150-1) having substantially a ring shape at one of the lids (140) and including a second field controller (150-2) having substantially a round plate shape at the other one of the lids (140).

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