Short-circuit device

Description

[0001] The present invention relates to a short-circuiting device and a converter, in particular a multilevel converter, with such a short-circuiting device.

[0002] Short-circuiting devices for short-circuiting large amounts of power, such as capacitors in multilevel converters, are subject to stringent requirements at the closing moment, i.e. the moment at which two electrical contact bodies with different electrical potentials make contact. Particularly at high voltages, such as 5000 V DC across a capacitor bank with several mF, e.g. 4-20 mF, an arc is ignited at an aluminum contact, resulting in severe burn-off of the closing element due to the arc ignited during closing. The short-circuiting device is required as a component in multilevel converters to ensure continued operation of such systems. The component, which is subjected to excessive stress at high voltages, essentially serves as a safety component.However, the burn-off caused by the arc generated has the disadvantage that a reliable electrical contact cannot be established. As a negative consequence, if not detected during system operation, a fire can occur.

[0003] A prior art short-circuiting device is described in WO 2011 / 107363 A1.

[0004] European patent application EP 1 052 665 A2 discloses a short-circuiter for use in electrical power distribution systems. A short-circuiting piston driven by a gas generator serves to electrically connect connecting busbars to a connecting busbar. When not short-circuited, an insulating membrane separates the connecting busbars from the connecting busbar.

[0005] Document CN 102 005 336 A discloses a switch with a pyrotechnic actuator. An insulating ring is arranged between a fixed contact and a moving contact.

[0006] Patent application WO 2013 / 185815 A1 discloses a bypass switch with a gas generator. This bypass switch features a thin polymer film arranged between two electrical contacts.

[0007] The document US 2013 / 255464 A1 discloses a disconnector in which a thin insulating layer is applied to a disconnecting blade. This insulating layer serves to prevent a busbar from being severed due to friction.

[0008] The task is to provide a short-circuiting device for short-circuiting high powers, in which a stable electrical contact can be established.

[0009] The invention is defined in claim 1. A short-circuiting device is provided which comprises a first electrical contact body and a second electrical contact body, which are spatially spaced from one another. Furthermore, the short-circuiting device comprises a contact element which is movable between a disconnected position and a closed position and which is arranged at least partially on or within the second electrical contact body, provides no electrically conductive connection between the first and second electrical contact bodies in the disconnected position, and electrically conductively connects the first and second electrical contact bodies to one another by means of a contact in the closed position.Furthermore, the short-circuiting device comprises a drive device which, upon triggering, moves the movable contact element from the second electrical contact body toward the first electrical contact body from the disconnected position to the closed position. According to the invention, the movable contact element comprises an insulating layer positioned on an end region of the movable contact element facing the first contact body and / or on a surface region of the first electrical contact body facing the end region of the movable contact element.

[0010] In the disconnected position, there is no physical contact. The first contact body is then electrically insulated from the contact element or the second contact body. The contact element can also be referred to as a bolt.

[0011] The short-circuiting device has the advantage that the insulating layer applied to the contact element and / or the first electrical contact body reduces or even prevents the arc. This is due to the fact that the critical insulation voltage is exceeded much later in air. The two electrical contact bodies as well as the contact element and the first electrical contact body have different potentials in the separated position or at the moment of closing, shortly before contact is formed. If the movable contact element is not provided with an insulating layer, arcing or breakdown can occur between the movable contact element and the first electrical contact body. The dielectric strength of air, for example, is approximately 3 kV / mm.By preventing the arc from burning away through the insulating layer, good electrical contact can be established between the first electrical contact body and the second contact body by means of the movable contact element. The insulating layer now prevents a breakdown or ignition of an arc when the critical distances are exceeded. In this case, an arc is only generated late or not at all. Preferably, the movable contact element is a movable, electrically conductive piston or an electrically conductive contact piston. Furthermore, the movable contact element is preferably a movable moving contact piece, and the first and second electrical contact bodies are each fixed contact pieces.

[0012] According to the invention, the insulating layer is positioned on a contact surface of the movable contact element, or preferably, the insulating layer is positioned on a contact surface of the first electrical contact body, which contacts the first electrical contact body with the movable contact element in the closed position. High electric fields are generated at the contact surfaces shortly before contact is formed, so an insulating layer applied here is particularly effective in preventing or delaying breakdown.

[0013] The insulation layer has a thickness of 10-100 µm, more preferably 10-50 µm, and particularly preferably 10-30 µm. The thickness of the insulation layer is thus very thin. Such thin insulation layers, as used, for example, in semiconductor construction, can be applied to the movable contact element using various processes, for example, by spraying, dipping, or printing, although the invention is not limited to these processes. Printing methods that can be used include, for example, screen printing or stencil printing, jetting, or inkjetting. The thin insulation layer also allows for good and secure electrical contacts to the first electrical contact body.

[0014] The insulation layer preferably comprises at least one of the following materials: thermoplastic, thermoset, siloxane compound, or ceramic compound. Examples of suitable thermoplastics include polyimides, polyamides, or polyetheretherketones (PEEK). Examples of suitable thermosets include epoxy resin or poly(p-phenylene-2,6-benzobisoxazole) (PPBO). Other inorganic or organic insulation materials besides siloxane compounds and ceramic compounds are also possible.

[0015] The drive device is preferably a pyrotechnic drive device. Pyrotechnics can be used to achieve the accelerations particularly suitable for such applications. Alternatively, other drive devices, such as spring-loaded actuators, can also be used.

[0016] The drive device is preferably designed to accelerate the movable contact element during transfer from the disconnected position to the closed position to a predetermined minimum speed at which the insulation layer is degraded, in particular abraded, scraped off, or burned, during the establishment of the contact, so that the movable contact element contacts the first contact body in the closed position. Advantageously, this allows good electrical contact to be established between the first contact body and the movable contact element despite the insulation layer present in the disconnected position.

[0017] Preferably, the drive device can be configured to accelerate the movable contact element to a minimum speed of more than 50 m / s, more preferably more than 75 m / s, and particularly preferably more than 100 m / s. At such speeds, in particular at speeds above 100 m / s, the degradation, i.e., in particular, the abrasion, scraping, or burning of the insulation layer can occur.

[0018] The first electrical contact body can preferably comprise a recess complementary in shape to the end region of the movable contact element, into which the movable contact element is retracted with at least part of the end region in the closed position. This enables the formation of a stable contact between the contact element and the first electrical contact body.

[0019] Preferably, the insulation layer is positioned at those locations on the movable contact element and / or the first electrical contact body where, in the case of a movable contact element and a first electrical contact body without an insulation layer, an electric field strength above the dielectric strength is generated during movement between the disconnected position and the closed position. For example, for a specific geometric configuration of the contact element and / or the first electrical contact body, those locations or regions on the contact element can be advantageously identified where increased electric fields exceeding the dielectric strength occur.For example, by quantitatively detecting the electric fields of a similar reference short-circuiting device but without an insulating layer during closing, the critical points can be determined which are to be covered with an insulating layer in accordance with the invention.

[0020] The invention further encompasses a converter, in particular a multilevel converter, which comprises a short-circuiting device according to one of the above embodiments. Such short-circuiting devices are required for converters, for example. The advantages of the converter can be derived from the above advantages of the short-circuiting device.

[0021] 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 the embodiments, which are explained in more detail in conjunction with the drawings. Figure 1 shows a cross-sectional view of a short-circuiting device according to the invention in the disconnected position according to a first embodiment; Figure 2 shows a cross-sectional view of a short-circuiting device according to the invention in the closed position according to a first embodiment; Figure 3 shows a cross-sectional view of a short-circuiting device according to the invention in the disconnected position according to a second embodiment; Figure 4 shows a cross-sectional view of a short-circuiting device according to the invention in the disconnected position according to a third embodiment; Figure 5 shows a cross-sectional view of an end region of a contact element according to a first embodiment; Figure 6 shows a cross-sectional view of an end region of a contact element according to a second embodiment; Figure 7 shows a cross-sectional view of an end region of a contact element according to a third embodiment; and Figure 8 shows a cross-sectional view of an end region of a contact element according to a fourth embodiment.

[0022] In theFigure 1 and the Figure 2 A cross-sectional view of a short-circuiting device 1 according to a first embodiment is shown in a disconnected position and a closed position, respectively. The following description refers to both figures.

[0023] The short-circuiting device 1 comprises a first electrical contact body 10 and a second electrical contact body 20, which are spatially spaced apart from one another. The short-circuiting device 1 further comprises a movable contact element 30. The movable contact element 30 is movable between a separation position, which is in the Figure 1 shown and a closed position, which is shown in the Figure 2The two electrical contact bodies 10, 20 are formed from an electrically conductive material. The movable contact element 30, at least in the area between the contact bodies 10, 20, is also formed from an electrically conductive material.

[0024] The movable contact element 30 is in the disconnected position, see Figure 1 , at least partially arranged on or in the second contact body 20. In particular, for example, already in the separated position, see Figure 1 , an electrical connection must exist between the movable contact element 30 and the second contact body 20. Then, in the disconnected position, the movable contact element 30 has the same electrical potential as the second contact body 20.

[0025] In the disconnected position, see Figure 1, no electrically conductive connection is provided between the first and second electrical contact bodies 10, 20. In the closed position, see Figure 2 , the first and second electrical contact bodies 10, 20 are electrically conductively connected to one another by a touch contact.

[0026] The movement of the movable contact element 30 is generated by a drive device 40. When triggered by the drive device 40, the movable contact element 30 is moved from the disconnected position by the second electrical contact body 20 towards the first electrical contact body 10, see Figure 1 , in the closed position, see Figure 2 , moved.

[0027] In this first embodiment, the movable contact element 30 further comprises an insulation layer 50, see Figure 1This insulation layer 50 is positioned on an end region 35 of the movable contact element 30 facing the first electrical contact body 10. The end region 35 is a region of the movable contact element 30 where high electric fields are generated when the movable contact element 30 moves toward the first contact body 10. The insulation layer 50 can advantageously prevent the occurrence of an arc or a breakdown, or at least delay or reduce it. As a result, good electrical contact can be established between the first electrical contact body 10 and the second contact body 20 by means of the movable contact element 30.

[0028] In the disconnected position, see Figure 1, there is no contact or no contact between the movable contact element 30 and the first electrical contact body 10. Rather, in this embodiment, an insulating gas path 90 is provided between the movable contact element 30 and the first electrical contact body 10 in the disconnected position, see Figure 1 , is provided. The gas line 90 can be filled with air, for example, although the invention is not limited thereto.

[0029] In the disconnected position of this embodiment, see Figure 1 , a contact surface 37 is formed on the end region 35 of the movable contact element 30 on outwardly directed side surfaces of the movable contact element 30, on which the insulation layer 50 is positioned or applied. This contact surface 37 is in the closed position, see Figure 2, flat on the first electrical contact body 10 and thus establishes a contact with the first electrical contact body 10. The contact surface 37 thus contacts in the closed position, see Figure 2 , the first electrical contact body 10. The positioning of the insulation layer 50 on the contact surface 37 is advantageous since it is precisely on these surfaces that high electrical fields arise shortly before contact, which can lead to an arc or breakdown, which is prevented or at least reduced or delayed by the insulation layer 50.

[0030] The insulation layer 50 can have a thickness D of 10-100 µm, more preferably 10-50 µm, and particularly preferably 10-30 µm. The following materials are preferably suitable for the insulation layer 50: thermoplastic, thermoset, siloxane compound, ceramic compound. Combinations of these materials are also encompassed by the invention, although the invention is not limited to these insulation materials and thicknesses D.

[0031] In this embodiment, a pyrotechnic drive device is used as the drive device 40. When triggered by escaping gases, this generates a thrust force to move the movable contact element 30 toward the first electrical contact body 10. Drive electronics can be provided for this purpose. A pyrotechnic drive device is particularly suitable for achieving the required speeds. However, other suitable drive devices 40 are also encompassed by the invention. For example, spring-loaded devices can also be used.

[0032] In this embodiment, the drive device 40 is designed, for example, to move the movable contact element 30 during transfer from the disconnected position, see Figure 1 , in the closed position, see Figure 2, to a predetermined minimum speed. At this minimum speed, the insulation layer 50 is degraded during the establishment of the contact. For example, the insulation layer 50 can be abraded, scraped off, or burned during the movement of the movable contact element 30 into the closed position, for example by friction, so that the movable contact element 30 in the closed position makes direct electrical contact with the first electrical contact body 10. In particular, in this embodiment, the insulation layer 50 is in the closed position, see Figure 2 , as described above, is used up, i.e., no longer present. This creates a high-quality conductive contact between the movable contact element 30 and the second electrical contact body 20, which is not impaired by residues of insulating material.

[0033] The speeds generated by the drive device 40, at which the movable contact element 30 is moved toward the first contact body 10, can accelerate to over 50 m / s, more preferably over 75 m / s, and particularly preferably over 100 m / s. Especially at minimum speeds of over 100 m / s, it can be ensured that a sufficiently thin insulation layer 50 is removed as described above.

[0034] By producing the thickness D of the insulation layer 50, it must be ensured that it can be consumed even at the speeds generated by the drive device 40 as described above, so that a good electrical contact can be formed. The thickness D is therefore subject to optimization, as it must be sufficiently insulating, but also be consumed during movement.

[0035] In this embodiment, the first electrical contact body 10 further comprises a recess 12 complementary in shape to the end region 35 of the movable contact element 30. In the closed position, see Figure 2 , the movable contact element 30 is retracted with at least a portion of the end region 35 into the recess 12. In this embodiment, the end region 35 of the movable contact element 30 is conical, as is the recess 12, which is complementary in shape. Appropriate insertion aids can be provided within the recess 12 to establish secure contact.

[0036] In this embodiment, the short-circuiting device 1 further comprises an insulating round tube 80, 85 arranged coaxially with the contact bodies 10, 20, which connects the electrical contact bodies 10, 20 to one another and thus stabilizes the entire assembly. For this purpose, screw connections 70, 75 are provided, for example, in the insulating round tube 85.

[0037] In this embodiment, the movable contact element 30 is expediently composed of various piston-shaped pieces, although the invention is not limited thereto. For example, the movable contact element 30 can also be constructed as a single unit. In this purely exemplary embodiment, a base-like piston piece 32 is facing the drive device 40, against which the drive device 40 directly engages and, when triggered, ensures a pushing effect of the entire movable contact element 30 in the direction of the first contact body 10. Furthermore, in this purely exemplary embodiment, a support piece 33 is provided, to which a contact piece 34 is connected. The base-like piston piece 32 serves to insulate the drive device 40 from the movable contact element 30. In other embodiments, such insulation and thus the support piece 33 and piston piece 32 can be dispensed with.The electrical contacts with the electrical contact bodies 10, 20 are made at the contact piece 34 of the movable contact element 30, which is electrically conductive.

[0038] Furthermore, the movable contact element 30 comprises in a certain section an outwardly directed widening 31 on the side surfaces below the end region 35, which in the closed position, see Figure 2 , contacted with an inwardly directed portion of the second electrical contact body 20, so that a secure connection to the second electrical contact body 20 can also be established.

[0039] In Figure 3 a cross-sectional view of a short-circuiting device 1 in the disconnected position according to a second embodiment is shown.

[0040] Compared to the Figure 1An insulation layer 50' is also positioned on a surface region 14 of the first electrical contact body 10 facing the end region 35 of the movable contact element 30. Alternatively, in yet another embodiment, the insulation layer 50 on the end region 35 of the movable contact element 30 can be omitted, so that only one insulation layer 50' is provided on the first electrical contact body 10. Purely by way of example, the insulation layer 50' in this embodiment is positioned within the recess 12. In particular, the insulation layer 50' is positioned on a contact region 37' of the first electrical contact body 10. This contact region 37' contacts the first electrical contact body 10 with the movable contact element 30 in the closed position, see Figure 2. The insulation layer 50' can also alternatively be positioned at those locations of the first electrical contact body 10 at which, in the case of a movable contact element without an insulation layer, an electric field strength above the dielectric strength is generated during movement between the disconnected position and the closed position. For the functionality and more precise details of the insulation layer 50', reference is also made to the description. Figure 1 and 2 referred to.

[0041] In the Figure 4 is a cross-sectional view of a short-circuiting device 1 according to the invention in the disconnected position according to a third embodiment. In comparison to Figure 1 The short-circuiting device 1 is shown without an insulated drive device 40. In comparison to Figure 1 purely as an example, no piston piece 32 is provided.

[0042] The Figures 5 to 8show, in cross-sectional view, various embodiments for positioning insulation layers 50 on the movable contact element 30. The position at which the insulation layer 50 is applied can depend on the receiving geometry of the first electrical contact body for receiving the movable contact element 30, i.e. the corresponding fixed bearing, and on the geometric shape of the movable contact element 30 itself.

[0043] In particular, the insulating layer 50 can be positioned at those locations on the movable contact element 30 where, in a movable contact element without an insulating layer, an electric field strength above the dielectric strength is generated during movement between the disconnected position and the closed position. This does not necessarily have to coincide with the contact surface 37 during the movement of the movable contact element from the disconnected position to the closed position. By detecting the electric fields during the movement of a contact element, these locations can be localized and then provided with the insulating layer 50 accordingly.

[0044] Figure 5 shows, by way of example, a rectangular end region 35 of the movable contact element 30, which is coated with an insulating layer 50. The contact surface 37 can be located both in the side region and on the front surface of the movable contact element 30.

[0045] Figure 6 shows an example of a conically shaped end region 35 similar to Figure 1 of the movable contact element 30, which is coated with an insulating layer 50. The contact surface 37 can be located both in the side region and on the front surface of the movable contact element 30.

[0046] Figure 7 shows, by way of example, a rounded end region 35 of the movable contact element 30, which is coated with an insulating layer 50. The contact surface 37 can be located both in the side region and on the front surface of the movable contact element 30.

[0047] Figure 8 shows an example of a conical end region 35 of the movable contact element 30. Here, the insulation layer 50 is compared to the Figures 5 to 7applied only to the lateral contact surfaces 37. The tip or front surface remains free in this exemplary embodiment.

[0048] Although the invention has been illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. List of reference symbols

[0049] 1Short-circuiting device 10First electrical contact body 12Recess 14Surface area 20second electrical contact body 30movable contact element 31expansion 32piston piece 33support piece 34contact piece 35End area 37, 37'Contact surface 40Drive device 50, 50'Insulation layer 70Screw connection 75Screw connection 80insulating round pipe 85insulating round pipe 90Gas line Thickness

Claims

1. Short-circuiting device (1), comprising: - a first electrical contact body (10) and a second electrical contact body (20) which are physically spaced apart from each other; - a contact element (30) movable between a separation position and a closed position, which contact element is arranged at least partially on or within the second electrical contact body (20), in the separation position provides no electrically conductive connection between the first and second electrical contact bodies (10, 20) and in the closed position electrically conductively connects the first and second electrical contact bodies (10, 20) to each other by way of touch contact; - a drive device (40) which, when triggered, moves the movable contact element (30) from the second electrical contact body (20) in the direction of the first electrical contact body (10) from the separation position to the closed position, - an insulating layer (50, 50') which is positioned on an end region (35) of the movable contact element (30), which end region faces the first electrical contact body (10), characterized in that - the insulating layer (50, 50') has a thickness (D) of 10-100 µm, more preferably 10-50 µm, particularly preferably 10-30 µm, and - the insulating layer is applied to the movable contact element.

2. Short-circuiting device (1) according to one of the preceding claims, wherein the insulating layer (50) is positioned on a contact surface (37, 37') of the movable contact element (30) and / or of the first electrical contact body (10), which contact surface ensures that the first electrical contact body (10) makes contact with the movable contact element (30) in the closed position.

3. Short-circuiting device (1) according to one of the preceding claims, wherein the insulating layer (50, 50') comprises at least one of the following materials: thermoplastic, thermoset, siloxane compound, ceramic compound.

4. Short-circuiting device (1) according to one of the preceding claims, wherein the drive device (40) is a pyrotechnic drive device.

5. Short-circuiting device (1) according to one of the preceding claims, wherein the drive device (40) is designed to accelerate the movable contact element (30) to a predetermined minimum speed when transferring the latter from the separation position to the closed position, at which minimum speed the insulating layer (50, 50'), when making the touch contact, is degraded, in particular abraded, scraped or burnt, so that the movable contact element (30) makes contact with the first electrical contact body (10) in the closed position.

6. Short-circuiting device (1) according to one of the preceding claims, wherein the drive device (40) is configured to accelerate the movable contact element (30) to a minimum speed of over 50 m / s, more preferably over 75 m / s, particularly preferably over 100 m / s.

7. Short-circuiting device (1) according to one of the preceding claims, wherein the first electrical contact body (10) comprises a recess (12) which is complementary in terms of shape to the end region (35) of the movable contact element (30) and into which at least part of the end region (35) of the movable contact element (30) is brought into the closed position.

8. Short-circuiting device (1) according to one of the preceding claims, wherein the insulating layer (50, 50') is positioned at those points of the movable contact element (30) and / or of the first electrical contact body (10) at which, in the case of a movable contact element and a first electrical contact body without an insulating layer, an electrical field strength above the breakdown strength is generated during the movement between the separation position and the closed position.

9. Converter, in particular multi-level converter, comprising a short-circuiting device (1) according to one of the preceding claims.