Medium or high voltage vacuum bulb
By integrating a semiconductor seal with the vacuum bulb's screen, the dielectric strength is enhanced, enabling it to handle higher voltages without size increase, addressing the challenge of dielectric stresses in vacuum bulbs.
Patent Information
- Application Number
- FR2023013866
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-12-08
- Publication Date
- 2026-02-27
- Estimated Expiration
- 2043-12-08
AI Technical Summary
Vacuum bulbs face challenges in withstanding higher voltages without increasing their size, particularly due to dielectric stresses generated by the screen's retaining flange, which counteract this objective.
Incorporating a seal made of semiconductor material surrounding the insulator, which is in electrical contact with the screen, to create two distinct interfaces and reduce electric field intensity, thereby enhancing dielectric strength.
This configuration increases dielectric strength, allowing the vacuum bulb to withstand higher voltages while maintaining or reducing its size, and can be used in medium- and high-voltage electrical distribution equipment.
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Abstract
Description
Title of the invention: Medium or high voltage vacuum bulb technical field
[0001] The present invention relates to the field of medium- and high-voltage vacuum switching devices, also known as vacuum lamps or vacuum bulbs. Vacuum lamps are used in medium- and high-voltage electrical distribution equipment, i.e., voltages above 1 kV. Vacuum lamps are associated with actuators to interrupt the current in a part of the circuit. Previous technique
[0002] As is well known, a vacuum bulb has two switching contacts arranged opposite each other. Each contact includes a rod for supplying the electric current, and a body fixed to the rod. The contacts are arranged in an insulating enclosure forming a sealed, vacuum-sealed housing. The contacts can be moved relative to each other. When the contacts are pressed together, current can flow from one contact to the other. When the contacts are separated, the current is interrupted.
[0003] A protective screen is placed inside the insulating enclosure and surrounds the electrical contacts. The screen prevents metallic particles detached from the contacts during the creation of an electric arc from being deposited on the inner surface of the insulating enclosure. To secure the screen to the insulating enclosure, it can be in two parts arranged side by side coaxially, and a portion of the screen serving as a retaining flange is clamped between the two parts of the insulating enclosure. This portion of the screen serving as a retaining flange generates dielectric stresses.
[0004] It is desirable to have vacuum tubes capable of withstanding higher voltages without increasing their size and, in particular, without increasing their diameter. The dielectric stresses generated by the portion of the screen serving as a retaining flange run counter to this objective.
[0005] There is therefore a need to have vacuum bulbs with improved dielectric strength. Summary
[0006] To this end, the invention proposes a medium or high voltage vacuum bulb, comprising: - an insulator forming a receiving enclosure, the insulator being formed of two coaxial elements, - two electrical contacts disposed in the insulation, configured to be moved relative to each other between a closed position in which the electrical contacts are pressed against each other and an open position in which the electrical contacts are separated from each other, - a screen radially surrounding the electrical contacts, configured to collect metallic particles emitted during the passage of an electric arc between the electrical contacts so as to protect the insulator from the emitted metallic particles, the screen comprising a clamping flange between the two elements of the screen, characterized in that the vacuum bulb comprises a seal of semiconductor material surrounding the insulator, the seal being in electrical contact with the screen.
[0007] The presence of the seal prevents the creation of a triple interface where the insulator, the screen, and the gas surrounding the vacuum bulb meet. Thanks to the seal, two triple interfaces are created: a first interface between the insulator, a first portion of the seal, and the gas surrounding the vacuum bulb, and a second interface between the screen, the insulator, and a second portion of the seal. This separation of the interfaces increases the dielectric strength of the vacuum bulb. The semiconducting nature of the seal material ensures that the seal is at the same electrical potential as the screen in its entirety, which allows the seal to have an electrical deflecting effect, reducing the electric field in this area. For the same performance, the size of the bulb can be reduced, or for the same size, the performance of the vacuum bulb can be improved.
[0008] The features listed in the following paragraphs can be implemented independently of each other or in any technically possible combination:
[0009] The vacuum bulb is sealed.
[0010] The vacuum bulb is generally cylindrical in shape and extends along an axis.
[0011] The insulator, the screen and the electrical contacts are coaxial.
[0012] According to one aspect of the invention, the semiconducting material seal is made of butadiene-acrylonitrile copolymers.
[0013] The joint is elastically deformable.
[0014] According to one embodiment of the vacuum bulb, the seal is in mechanical contact with the screen fixing flange.
[0015] The seal is in mechanical contact with the insulator.
[0016] According to another embodiment of the vacuum bulb, the seal is distant from the screen mounting flange, and an axial surface of at least one of the two coaxial elements of the insulator comprises an electrically conductive coating, the coating being in contact with the seal and with the mounting flange.
[0017] The electrically conductive coating on the axial surface, which is in contact on one side with the screen mounting flange and on the other with the gasket, ensures electrical contact between the two parts. The gasket and the screen are thus at the same electrical potential.
[0018] According to an alternative embodiment of the vacuum bulb, or complementaryly, a space separating the screen mounting flange and the seal includes an electrically conductive grease.
[0019] The grease is, for example, a silicone grease.
[0020] According to one aspect of the proposed vacuum bulb, the seal is removable.
[0021] According to one example of use, the seal can thus be specifically put in place for the conditioning procedure aimed at removing surface defects from the contact bodies of the vacuum bulb. The seal can then be removed for use of the bulb in an electrical device. According to another example of use, the seal can be kept for the entire duration of use of the vacuum ampoule.
[0022] The seal can be added to the vacuum bulb.
[0023] Once mounted, the seal can be removed from the vacuum bulb.
[0024] The insulator has the shape of a cylinder of revolution.
[0025] The two elements of the insulator have the shape of a hollow cylinder.
[0026] The two insulating elements are arranged side by side along an axial direction and are separated from each other by the screen mounting bracket.
[0027] The two elements of the insulator have an identical inner diameter.
[0028] The two elements of the insulation have an identical outside diameter.
[0029] The insulation is ceramic.
[0030] The screen includes a cylindrical portion surrounding the electrical contacts.
[0031] The screen is, for example, made of copper.
[0032] The screen fixing flange extends radially outwards from an outer surface of the cylindrical portion of the screen.
[0033] The screen fixing flange extends in a plane transverse to the axis of the screen.
[0034] The screen fixing flange is annular in shape.
[0035] The screen fixing flange is made of copper.
[0036] The screen mounting flange is in contact with each of the two elements of the insulation.
[0037] The screen fixing flange is compressed in an axial direction between the two elements of the insulator.
[0038] The connection between the screen fixing flange and each of the two insulating elements is sealed.
[0039] An axial surface of the first element is in contact with a first face of the screen fixing flange.
[0040] An axial surface of the second element is in contact with a second face of the screen fixing flange.
[0041] An outer lateral surface of the mounting flange is radially recessed from an outer lateral surface of the first insulation element. Similarly, the outer lateral surface of the mounting flange is radially recessed from an outer lateral surface of the second insulation element.
[0042] An outside diameter of the fixing flange is greater than an average diameter of the first element and the second element.
[0043] The joint partially covers an outer lateral surface of the first element and an outer lateral surface of the second element.
[0044] The joint partially covers an axial surface of the first element and an axial surface of the second element.
[0045] According to one embodiment of the vacuum bulb, the seal is toroidal in shape when the seal is in the free state.
[0046] According to one embodiment, a diameter of a cross-section of the joint is between 5 millimeters and 40 millimeters.
[0047] According to one embodiment, an average diameter of the joint is between 50 millimeters and 200 millimeters.
[0048] Preferably, the ratio of the diameter of a cross-section of the joint and the average diameter of the joint is between 0.05 and 0.2.
[0049] This shape factor allows the joint to closely follow the shape of the ends of the insulation elements, while also allowing sufficient overlap of the axial end portions of the elements.
[0050] According to one embodiment of the vacuum bulb, the seal comprises in the free state: - a toroidal portion, - an annular portion extending radially inwards, the annular portion being in contact with the first element and with the second element in an axial direction.
[0051] The annular part allows the seal to have a shape that facilitates the establishment of mechanical contact with the screen fixing flange.
[0052] A first face of the annular portion is in contact with an axial surface of the first element of the insulator.
[0053] A second face of the annular portion, opposite to the first face, is in contact with an axial surface of the second element of the insulator.
[0054] The annular portion extends towards the axis of the toroidal portion in an equatorial plane of the toroidal part.
[0055] According to one embodiment of the vacuum bulb, the annular portion of the seal is distant from the screen fixing flange.
[0056] More specifically, the annular portion of the seal is distant from an outer lateral surface of the screen fixing flange.
[0057] A lateral surface of the annular portion of the seal is distant from the outer lateral surface of the screen mounting flange, in a radial direction.
[0058] An outer lateral surface of the fixing flange, a lateral surface of the annular portion of the seal, an axial surface of the first element and an axial surface of the second element define a volume of annular shape.
[0059] A volume separating the annular portion of the seal and the screen fixing flange is filled at least partially with an electrically conductive grease.
[0060] The volume separating the annular portion of the seal and the screen fixing flange can be completely filled with an electrically conductive grease.
[0061] The cavity delimited by the outer lateral surface of the fixing flange, the lateral surface of the annular portion of the seal, an axial surface of the first element and an axial surface of the second element is filled, partially or totally, with an electrically conductive grease.
[0062] A ratio between the diameter of a cross-section of the toroidal part and the outside diameter of the insulator is between 0.05 and 0.2.
[0063] A ratio between the inner diameter of the toroidal part and the outer diameter of the insulator is between 0.8 and 0.95.
[0064] A portion of the first element in contact with the joint includes a chamfer.
[0065] Similarly, a portion of the second element in contact with the joint includes a chamfer.
[0066] The invention also relates to a method of conditioning a vacuum ampoule. The process involves the following steps: (i) provide a vacuum ampoule comprising: - an insulator forming a receiving enclosure, the insulator being formed of two coaxial elements, - a pair of electrical contacts arranged in the insulation, comprising a moving contact and a fixed contact, - a screen radially surrounding the electrical contacts, configured to collect metallic particles emitted during the passage of an electric arc between the electrical contacts so as to protect the insulation from the emitted metallic particles, the screen having a clamping flange between the two elements of the screen, (ii) provide a seal, (iii) equip the vacuum bulb with a seal surrounding the insulation, the seal being in electrical contact with the screen, (iv) separate the contacts of the vacuum bulb and increase the electrical voltage between the electrical contacts until an electric arc is created between the contacts, (v) iterate the step of creating an electric arc in order to condition the surfaces of the electrical contacts, (vi) disassemble the vacuum bulb seal.
[0067] The addition of the seal for the conditioning phase of the vacuum bulb makes it possible to increase the voltage between the electrical contacts without creating a discharge between the insulator of the vacuum bulb and the external environment. Electric arcs can be preferentially created between electrical contacts, which accelerates the conditioning of the vacuum bulb.
[0068] Step (vi) is optional. According to a variant of the proposed packaging process, the seal can remain mounted on the vacuum ampoule for the entire duration of the vacuum ampoule's use. In this case, the bulb is mounted in an electrical device equipped with its seal. The presence of the seal improves the dielectric strength of the bulb under vacuum during operation.
[0069] Step (vi) of dismantling the seal is thus replaced by a step: (vi') maintain the seal on the vacuum bulb until the vacuum bulb is mounted in an electrical device. Brief description of the drawings
[0070] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:
[0071] [Fig-1] is a schematic side view of a vacuum bulb,
[0072] [Fig.2] is a side view, in cross-section, of a vacuum bulb,
[0073] [Fig.3] is a side view of a vacuum bulb according to an embodiment of the invention,
[0074] [Fig.4] is a partial, side and cross-sectional view of the vacuum bulb of [Fig.3], not equipped with its seal,
[0075] [Fig.5] is a partial, side and cross-sectional view of the vacuum bulb of [Fig.3],
[0076] [Fig.6] is a partial, side and cross-sectional view of an alternative embodiment of the vacuum bulb of [Fig.3],
[0077] [Fig.7] represents a seal fitted to a vacuum ampoule according to one embodiment,
[0078] [Fig.8] represents a seal fitted to a vacuum ampoule according to another method of realization,
[0079] [Fig.9] is a block diagram of a method for conditioning a vacuum ampoule according to the invention. Description of the implementation methods
[0080] To facilitate reading the figures, the various elements are not necessarily drawn to scale. In these figures, identical elements bear the same reference numerals. Certain elements or parameters may be indexed, that is, designated, for example, as first element or second element, or first parameter and second parameter, etc. This indexing aims to differentiate similar, but not identical, elements or parameters. This indexing does not imply any priority of one element or parameter over another, and the designations may be interchanged. When it is specified that a subsystem includes a given element, this does not exclude the presence of other elements in that subsystem. Similarly, when it is specified that a subsystem includes a given element, it is understood that the subsystem includes at least that element.
[0081] In the different figures, the X, Y, Z axes designate the three directions of space in order to identify the viewing angle of each figure.
[0082] A medium or high voltage vacuum bulb 50 is shown on [Fig.1] and on [Fig.2]. The vacuum ampoule 50 includes: - a first electrical breaking contact 2, - a second electrical breaking contact 3. At least one of the first contact 2 and the second contact 3 is configured to be moved along an axis D between an open position O in which the electrical contacts 2, 3 are separated from each other, and a closed position F in which the electrical contacts 2, 3 are pressed against each other so as to allow the passage of electric current between the first contact 2 and the second contact 3.
[0083] The vacuum bulb 50 is part of a medium voltage switching device, such as a circuit breaker or a disconnector. In part A of [Fig. 1], the electrical break contacts 2 and 3 are in contact with each other, and an electric current can flow. In part A of [Fig. 1], the symbol C represents the flow of electric current. When contacts 2, 3 are separated from each other, the flow of electric current is interrupted, generally after a transient period during which an electric arc is present between the two electrical contacts 2, 3. In part B of [Fig.1], the electrical contacts are separated by a distance schematically represented by the sign g, and the flow of electric current from one contact to the other is interrupted.
[0084] The first electrical contact 2 comprises a cylindrical rod 22 and a disc-shaped contact body 21. The contact body 21 is integral with the rod 22 and extends transversely to the cylindrical rod 22. Similarly, the second electrical contact 3 comprises a cylindrical rod 32 and a disc-shaped contact body 31, integral with the cylindrical rod 32 and extending transversely to the cylindrical rod 32. Each contact body 21, 31 is fixed respectively to the cylindrical rod 22, 32, for example by brazing. When the electrical contacts 2 and 3 are in contact, the contact body 21 and the contact body 31 are pressed against each other. In the closed position, a spring (not shown) maintains a preload between the contact bodies 21 and 31. In other words, a contact pressure is applied between the contact bodies 21 and 31 in the closed position, this contact pressure being determined by the force applied by the spring. The pre-charge spring is part of the control mechanism of the vacuum bulb 50. The electrical contacts 2,3 are arranged in an insulating envelope, also called insulator 1. A protective screen 4 is arranged inside the insulator 1, radially positioned between the electrical contacts 2,3 and the inner wall of the insulator 1. The protective screen 4 prevents metallic particles detached from the contacts 2,3 during the creation of electric arcs from being deposited on the inner surface of the insulator 1.
[0085] Fig. 3 is an external view of the proposed vacuum bulb 50.
[0086] The medium or high voltage 50 vacuum bulb comprises: - an insulator 1 forming a receiving enclosure, the insulator 1 being formed of two coaxial elements la, 1b, - two electrical contacts 2, 3 disposed in the insulator 1, configured to be moved relative to each other between a closed position F in which the electrical contacts 2, 3 are in contact with each other and an open position O in which the electrical contacts 2, 3 are separated from each other, - a screen 4 radially surrounding the electrical contacts 2, 3, configured to collect metallic particles emitted during the passage of an electric arc between the electrical contacts 2, 3 so as to protect the insulator 1 from the emitted metallic particles. The screen 4 has a fixing flange 5 tightened between the two elements la, 1b of the screen 4. The vacuum bulb 50 includes a seal 7 made of semiconductor material surrounding the insulator 1, the seal 7 being in electrical contact with the screen 4.
[0087] The presence of the seal 7 prevents the creation of a triple interface where the insulator 1, the screen 4, and the gas surrounding the vacuum bulb 50 would meet. Thanks to the presence of the seal 7, two distinct triple interfaces are created: a first triple interface between the insulator 1, a first portion of the seal 7, and the gas surrounding the vacuum bulb 50, and a second triple interface between the screen 4, the insulator 1, and a second portion of the seal 7. This separation of the triple interfaces increases the dielectric strength of the vacuum tube 50. The semiconducting nature of the material of the seal 7 ensures that the seal 7 is at the same electrical potential as the screen 4 in its entirety, thus enabling the seal 7 to act as an electrical deflector, reducing the electric field in this area. For the same performance, the size of the tube can be reduced, or for the same size, the performance of the vacuum tube can be improved.
[0088] The vacuum bulb 50 is generally cylindrical in shape and extends along an axis D. The insulator 1 has the shape of a cylinder of revolution.
[0089] The two elements la, 1b of the insulator 1 have the shape of a hollow cylinder. The two elements a, 1b of the insulator 1 are arranged side by side along an axial direction and are separated from each other by the fixing flange 5 of the screen 4. Insulator 1, screen 4, and electrical contacts 2 and 3 are coaxial. Axis D is the common axis of the first element 1a of insulator 1, the second element 1b of insulator 1, screen 4, the first electrical contact 2, and the second electrical contact 3.
[0090] Figure 4 shows a vacuum bulb 50 in which the seal 7 is not mounted. The two elements 1a, 1b of the insulator 1 have the same inner diameter. This inner diameter is designated by the symbol Di-1 in Figure 4. The two elements a, 1b of the insulator 1 have the same outside diameter. This outside diameter is designated by the symbol De-1 on [Fig.4].
[0091] The insulator 1 is ceramic. Insulator 1, for example, is made of alumina (chemical formula A12O3). More specifically, each element 1a, 1b is made of ceramic, for example alumina.
[0092] The screen 4 comprises a cylindrical portion 6 surrounding the electrical contacts 2, 3. The cylindrical portion 6 extends along the rods 22, 32 and is opposite the contact bodies 21, 31. Screen 4, for example, is made of copper. The fixing flange 5 of the screen 4 extends radially outwards from an outer surface 6e of the cylindrical portion 6 of the screen 4.
[0093] The fixing flange 5 of the screen 4 extends in a plane P transverse to the axis D of the screen 4. The fixing flange 5 of the screen 4 is annular in shape. The mounting flange 5 of the screen 4 is made of copper. The mounting flange 5 of the screen 4 is fixed to the cylindrical portion 6 surrounding the electrical contacts 2,3 by brazing. The fixing flange 5 and the cylindrical part 6 of the screen 4 are thus at the same electrical potential.
[0094] The fixing flange 5 of the screen 4 is in contact with each of the two elements la, 1b of the insulator 1. The fixing flange 5 of the screen 4 is compressed in an axial direction between the two elements la, 1b of the insulator 1. The connection between the fixing flange 5 of the screen 4 and each of the two elements la, 1b of the insulation is watertight.
[0095] An axial surface 10a of the first element la is in contact with a first face 15 of the fixing flange 5 of the screen 4. An axial surface 10b of the second element 1b is in contact with a second face 16 of the fixing flange 5 of the screen 4.
[0096] The vacuum bulb 50 is sealed. The pressure inside the vacuum bulb 50 is, for example, less than 10⁴ millibars. The gaseous medium in which the vacuum ampoule 50 is placed is, for example, ambient air. The ambient air in which the vacuum ampoule is placed is represented schematically by the symbols A in figures 4, 5, 6.
[0097] An outer lateral surface 17 of the fixing flange 5 is radially recessed from an outer lateral surface 1 of the first element 1 of the insulator 1. Similarly, the outer lateral surface 17 of the fixing flange 5 is radially recessed from an outer lateral surface 11b of the second element 1b of the insulation 1. An outside diameter De-5 of the fixing flange 5 is greater than an average diameter Dm-1 of the first element la and of the second element 1b. The average diameter Dm-1 of the first element is the average between the inner diameter Di-1 and the outer diameter De-1.
[0098] Fig. 5 and Fig. 6 are views of the area designated by the sign F on Fig. 4. In these figures, the vacuum bulb 50 is equipped with a seal 7.
[0099] The seal 7 made of semiconductor material is made of butadiene-acrylonitrile copolymers. This material is also called nitrile rubber, and is commonly referred to by the English acronym NBR for "nitrile butadiene rubber". Joint 7 is elastically deformable.
[0100] The seal 7 in the illustrated example is a single piece. For example, joint 7 is obtained by molding.
[0101] According to an embodiment of the vacuum bulb 50 illustrated in [Fig.5], the seal 7 is in mechanical contact with the fixing flange 5 of the screen 4. Electrical contact between the seal 7 and the fixing flange 5 of the screen 4 is then obtained by establishing direct mechanical contact between the two parts.
[0102] The seal 7 is in mechanical contact with the insulator 1. More specifically, joint 7 is in mechanical contact with the first element 1a of the insulation 1. Joint 7 is also in mechanical contact with the second element 1b of the insulation 1. The joint 7 surrounds the insulation 1 and partially covers the outer surface 1la of the first element la of the insulation 1, as well as the outer surface 11b of the second element 1b.
[0103] The joint 7 partially covers an outer lateral surface 1la of the first element la and an outer lateral surface 11b of the second element 1b. The joint 7 partially covers an axial surface 10a of the first element 1a and an axial surface 10b of the second element 1b.
[0104] Fig. 6 illustrates an embodiment of the vacuum bulb 50 in which the seal 7 is distant from the mounting flange 5 of the screen 4. A space designated by the sign V radially separates the fixing flange 5 and the screen 4. The seal 7 is not in mechanical contact with the fixing flange 5 of the screen 4.
[0105] An axial surface 10a, 10b of at least one of the two coaxial elements la, 1b of the insulator 1 comprises an electrically conductive coating 14, the coating 14 being in contact with the joint 7 and with the fixing flange 5.
[0106] The electrically conductive coating 14 is present on an axial surface of at least one element la, 1b, this axial surface being in contact on one side with the fixing flange 5 of the screen 4 and on the other side with the seal 7. The coating 14 makes it possible to ensure electrical continuity between the seal 7 and the fixing flange 5. The seal 7 and the screen 4 are thus placed at the same electrical potential.
[0107] The coating 14 is for example a metallic layer deposited on the axial end of an element of the insulator 1. According to the example in [Fig.6], only the first element of the insulator 1 comprises the electrically conductive coating 14. According to an example not shown, the first element 1a and the second element 1b each comprise an electrically conductive coating deposited on their respective axial end.
[0108] A space V separating the mounting flange 5 from the screen 4 and the seal 7 includes an electrically conductive grease. Electrical contact between the seal 7 and the fixing flange 5 of the screen 4 can be obtained, or completed, by means of the electrical conduction of the grease interposed between the seal 7 and the fixing flange 5 of the screen 4.
[0109] In addition, the grease disposed in the annular space V between the seal 7 and the fixing flange 5 of the screen 4 helps to prevent the presence of air bubbles in this space separating the two parts. The grease is, for example, silicone grease.
[0110] Seal 7 is removable.
[0111] According to one example of use, the seal 7 can thus be put in place specifically for the conditioning procedure carried out during the manufacture of the vacuum ampoule 50. This conditioning procedure aims to remove surface defects from the contact bodies 21, 31 of the vacuum ampoule 50. To achieve this, electric arcs are created between the contacts, and these electric arcs melt and eliminate surface defects forming angular singularities on the surface of the new contact bodies. The seal 7 can then be removed once the vacuum ampoule 50 conditioning procedure is complete. The seal 7 is therefore absent from the vacuum ampoule 50 when the vacuum ampoule 50 is used in an electrical device.
[0112] According to another example of use, the seal 7 can be retained for the entire duration of use of the vacuum ampoule 50. Seal 7, for example, is installed before the packaging procedure and is then left in place.
[0113] The seal 7 can be added to the vacuum bulb 50. Once assembled, the seal 7 can be removed from the vacuum bulb 50.
[0114] Multiple successive assembly and disassembly cycles can be carried out without damaging the seal 7. The seal 7 can, for example, be disassembled to facilitate the assembly of the vacuum bulb 50 in an electrical device.
[0115] According to one embodiment of the vacuum bulb 50, the seal 7 is toroidal in shape when the seal 7 is in the free state. In other words, the joint has the shape of a torus in the absence of mechanical stress likely to deform the joint. Fig. 7 represents the seal 7 in its free state, i.e. not mounted on the vacuum bulb 50.
[0116] According to one embodiment, a diameter Dt-7 of a cross-section of the joint 7 is between 5 millimeters and 40 millimeters. The diameter Dt-7 of a cross-section of seal 7 is the diameter in its free state, that is, without deformation. It is therefore the dimension when seal 7 is not mounted on the vacuum bulb 50. The diameter Dt-7 is also called the torus diameter.
[0117] According to an example embodiment, an average diameter Dm-7 of the joint 7 is between 50 millimeters and 200 millimeters. The average diameter of the torus is understood to be the average between the inner diameter Di-7 of the torus and the outer diameter De-7 of the torus. As before, the average diameter Dm-7 of joint 7 is the diameter in the free state, i.e. without deformation. The inner diameter Di-7 and the outer diameter De-7 are measured parallel to the equatorial plane P7 of joint 7.
[0118] Preferably, a ratio of the diameter Dt-7 of a cross-section of the joint 7 and the average diameter Dm-7 of the joint 7 is between 0.05 and 0.2. This shape factor allows the joint 7 to fit well with the shape of the ends of the lateral surface of the elements la, 1b of the insulation 1, while also allowing sufficient overlap of the axial end portions 10a, 10b of the elements la, 1b.
[0119] According to the embodiments illustrated in Figures 5 and 6, the joint 7 comprises in its free state: - a toroidal portion 8, - an annular portion 9 extending radially inwards, the annular portion 9 being in contact with the first element la and with the second element 1b in an axial direction.
[0120] The annular part 9 allows the seal 7 to have a shape facilitating the establishment of mechanical contact with the fixing flange 5 of the screen 4.
[0121] A first face 19 of the annular portion 9 is in contact with an axial surface 10a of the first element la of the insulator 1. A second face 20 of the annular portion 9, opposite the first face 19, is in contact with an axial surface of the second element 1b of the insulator 1.
[0122] The annular portion 9 extends towards the axis D of the toroidal portion 8 in an equatorial plane P8 of the toroidal part 8. The thickness of the annular part 9 is less than the diameter of the toroidal part 8. The annular part 9 can therefore easily fit into the space separating the axial surface 10a of the first element 1a from the axial surface 10b of the second element 1b.
[0123] On [Fig.5] and on [Fig.6], the toroidal part 8 is represented taking into account, schematically, the deformation undergone in contact with the outer surface lia, 11b of the insulator 1.
[0124] According to the embodiment of [Fig.6], the annular portion 9 of the seal 7 is distant from the fixing flange 5 of the screen 4.
[0125] More specifically, the annular portion 9 of the seal 7 is distant from an outer lateral surface 17 of the fixing flange 5 of the screen 4. A lateral surface 18 of the annular portion 9 of the joint 7 is thus distant from the outer lateral surface 17 of the fixing flange 5 of the screen 4, in a radial direction.
[0126] In other words, a radial play is present between the annular portion 9 of the seal 7 and the fixing flange 5 of the screen 4.
[0127] An outer lateral surface 17 of the fixing flange 5, a lateral surface 18 of the annular portion 9 of the seal 7, an axial surface 10a of the first element 1a and an axial surface 10b of the second element 1b define a volume V of annular shape.
[0128] The volume V separating the annular portion 9 of the seal 7 and the mounting flange 5 of the screen 4 is at least partially filled with electrically conductive grease. The volume V separating the annular portion 9 of the seal 7 and the mounting flange 5 of the screen 4 may be completely filled with electrically conductive grease.
[0129] The cavity delimited by the outer lateral surface 17 of the fixing flange 5, the lateral surface 18 of the annular portion 9 of the seal 7, an axial surface 10a of the first element 1a and an axial surface 10b of the second element 1b is filled, partially or totally, with an electrically conductive grease.
[0130] A ratio between the diameter of a cross-section of the toroidal part 8 and the outside diameter De-1 of the insulator 1 is between 0.05 and 0.2. A ratio between the inner diameter of the toroidal part 8 and the outer diameter De-1 of the insulator 1 is between 0.8 and 0.95.
[0131] A portion of the first element in contact with the joint 7 includes a chamfer 14a. Similarly, a portion of the second element 1b in contact with the joint 7 includes a chamfer 14b. The chamfer 14a of the first element la connects a portion of the axial surface 10a of the first element la and a portion of the outer lateral surface 1 la of the first element la. The same applies to the chamfer 14b of the second element 1b.
[0132] The chamfers 14a, 14b facilitate the insertion of the joint 7 between the axial surfaces 10a, 10b of the first element 1a and the second element 1b.
[0133] A conditioning process can be applied to a vacuum ampoule. This conditioning is applied when the ampoule is new, before it is mounted on an electrical device.
[0134] The invention also relates to a method of conditioning a vacuum ampoule 50. The packaging process for a 50 vacuum ampoule includes the following steps: (i) supply a 50 vacuum ampoule comprising: — an insulator 1 forming a receiving enclosure, the insulator 1 being formed of two coaxial elements la, 1b, — a pair of electrical contacts 2, 3 arranged in the insulator 1, comprising a movable contact 2 and a fixed contact 3, — a screen 4 radially surrounding the electrical contacts 1, 2, configured to collect the metallic particles emitted during the passage of an electric arc between the electrical contacts 2, 3 so as to protect the insulator 1 from the emitted metallic particles, the screen 4 having a fixing flange 5 tightened between the two elements, 1b of the screen 4, (ii) provide a seal 7, (iii) equip the vacuum bulb 50 with a seal 7 surrounding the insulator 1, the seal 7 being in electrical contact with the screen 4, (iv) separate the contacts of the vacuum bulb 50 and increase an electrical voltage between the electrical contacts 2, 3 until an electric arc is created between the contacts 2,3, (v) iterate step (iv) of creating an electric arc so as to condition the surfaces of the electrical contacts 2,3, (vi) disassemble the seal 7 of the vacuum bulb 50.
[0135] The addition of the seal 7 for the conditioning phase of the vacuum bulb 50 makes it possible to increase the voltage between the electrical contacts 2, 3 without creating a discharge between the insulator of the vacuum bulb 50 and the external environment. Electric arcs can be preferentially created between electrical contacts 2 and 3, thereby increasing the voltage at which conditioning is performed. The duration of the conditioning phase of the vacuum bulb 50 can thus be shortened.
[0136] Step (vi) is optional. According to a variant of the proposed conditioning process, the seal 7 can remain mounted on the vacuum ampoule 50 for the entire duration of use of the vacuum ampoule 7. The bulb is thus mounted in an electrical device equipped with its seal 7. The presence of the seal 7 improves the dielectric strength in service of the vacuum bulb 50, and further allows the conditioning phase to be accelerated.
[0137] Step (vi) of dismantling seal 7 is thus replaced by a step: (vi') maintain the seal 7 on the vacuum bulb 50 until the vacuum bulb 50 is mounted in an electrical device. The electrical device could be, for example, a circuit breaker.
Claims
Demands
1. A medium or high voltage vacuum lamp (50) comprising: - an insulator (1) forming a receiving enclosure, the insulator (1) being formed of two coaxial elements (la, 1b), - two electrical contacts (2, 3) disposed in the insulator (1), configured to be displaced relative to each other between a closed position (F) in which the electrical contacts (2, 3) are in contact with each other and an open position (O) in which the electrical contacts (2, 3) are separated from each other, - a screen (4) radially surrounding the electrical contacts (2, 3), configured to collect metallic particles emitted during the passage of an electric arc between the electrical contacts (2, 3) so as to protect the insulator (1) from the emitted metallic particles, the screen (4) having a mounting flange (5) compressed in an axial direction between the two elements (la, 1b) of the insulation (1),characterized in that the vacuum bulb (50) comprises a removable seal (7) made of semiconductor material surrounding the insulator (1), the seal (7) being in electrical contact with the screen (4).
2. Vacuum ampoule (50) according to claim 1, wherein the seal (7) in semiconductor material is made of butadiene-acrylonitrile copolymers.
3. Vacuum bulb (50) according to claim 1 or 2, wherein the seal (7) is in mechanical contact with the fixing flange (5) of the screen (4).
4. Vacuum bulb (50) according to claim 1 or 2, wherein the seal (7) is distant from the mounting flange (5) of the screen (4), and wherein an axial surface (10a, 10b) of at least one of the two coaxial elements (la, 1b) of the insulator (1) comprises an electrically conductive coating (14), the coating (14) being in contact with the seal (7) and with the mounting flange (5).
5. Vacuum bulb (50) according to any one of the preceding claims, wherein a space (V) separating the fixing flange (5) from the screen (4) and the seal (7) comprises an electrically conductive grease.
6. Vacuum ampoule (50) according to any one of the preceding claims, wherein: - the joint (7) partially covers an outer lateral surface (lia) of the first element (la) and an outer lateral surface (11b) of the second element (1b), and - the joint (7) partially covers an axial surface (10a) of the first element (la) and an axial surface (10b) of the second element (1b).
7. Vacuum ampoule (50) according to any one of claims 1 to 6, wherein the seal (7) is toroidal in shape when the seal (7) is in the free state.
8. Vacuum ampoule (50) according to any one of the preceding claims, wherein a ratio of a diameter (Dt-7) of a cross-section of the seal (7) and an average diameter (Dm-7) of the seal (7) is between 0.05 and 0.
2.
9. Vacuum ampoule (50) according to any one of claims 1 to 6, wherein the seal (7) comprises in the free state: - a toroidal portion (8), - an annular portion (9) extending radially inwards, the annular portion (9) being in contact with the first element (la) and with the second element (1b) in an axial direction.
10. Vacuum bulb (50) according to the preceding claim, wherein the annular portion (9) extends towards the axis of the toroidal portion (8) in an equatorial plane (P8) of the toroidal part (8).
11. Vacuum bulb (50) according to claim 9 or 10, wherein a ratio between a diameter (Dt-8) of a cross-section of the toroidal part (8) and an outside diameter (De-1) of the insulator (1) is between 0.05 and 0.
2.
12. Vacuum bulb (50) according to any one of claims 9 to 11, wherein a ratio between an inner diameter (Di-8) of the toroidal part (8) and an outer diameter (De-1) of the insulator (1) is between 0.8 and 0.
95.
13. Vacuum ampoule (50) according to any one of the preceding claims, wherein: - a portion of the first element (la) in contact with the seal (7) includes a chamfer (14a), and - a portion of the second element (1b) in contact with the seal (7) includes a chamfer (14b).
14. A method for packaging a vacuum ampoule, comprising the steps: (i) providing a vacuum ampoule (50) comprising: - an insulator (1) forming a receiving enclosure, the insulator (1) being formed of two coaxial elements (la, 1b), - a pair of electrical contacts (2, 3) disposed in the insulator (1), comprising a movable contact (2) and a fixed contact (3), - a screen (4) radially surrounding the electrical contacts (1, 2), configured to collect the metallic particles emitted during the passage of an electric arc between the electrical contacts (2, 3) so as to protect the insulator (1) from the emitted metallic particles, the screen (4) having a fixing flange (5) compressed in an axial direction between the two elements (la, 1b) of the insulator (1), (ii) provide a seal (7), (iii) equip the vacuum bulb (50) with a seal (7) surrounding the insulator (1), the seal (7) being in electrical contact with the screen (4), (iv) separate the contacts of the vacuum bulb (50) and increase an electrical voltage between the electrical contacts (2, 3) until an electric arc is created between the contacts (2,3), (v) iterate the step of creating an electric arc so as to achieve conditioning of the surfaces of the electrical contacts.