Fuse element and fuse

Abstract

The invention relates to a fuse element (10) for a fuse with an integrated measurement function, having a first receiving area (20) for receiving a melting conductor of the fuse, said first receiving area (20) being delimited in the length direction (L) of the fuse by a closure element and in a direction (R) orthogonal to the length direction (L) by the fuse element (10). Furthermore, the fuse element (10) has a second receiving area (30), which is physically separated from the first receiving area (20), for receiving a measuring device of the fuse, said second receiving area (30) being designed to receive the measuring device in a wall section (13) of the fuse element (10). The second receiving area (30) formed in the fuse element (10) protects the measuring device arranged therein against interfering environmental influences. The measuring device is used to ascertain the electric current flowing through the fuse directly on the fuse. In this manner, a fuse with an integrated measuring function can be implemented which allows the state of the fuse, and thus the state of an electric system secured by the fuse, to be directly detected in situ without requiring a visual check.

Description

[0001] The invention relates to a fuse with integrated measuring function, comprising a measuring device for determining the electrical current flowing through the fuse, wherein the fuse has a pressure body which has a first receiving space for receiving a fusible element of the fuse and a second receiving space for receiving the measuring device.

[0002] Conductors carrying an electric current heat up. Excessively high currents can cause excessive heating of the conductor and, as a result, melting of the insulation surrounding the conductor, which can lead to damage or even a cable fire. To prevent this fire hazard, if an excessively high electric current occurs, ieIn the event of an overload current or a short-circuit current, the electrical current must be switched off in a timely manner. This is ensured by so-called overcurrent protection devices.

[0003] An example of such an overcurrent protection device is a fuse that is triggered by the AwayThe melting of one or more fusible elements interrupts the circuit if the current in the circuit protected by the fuse exceeds a certain value for a certain period of time. The fuse consists of an insulating body with two electrical connections that are electrically connected to one another inside the insulating body by one or more fusible elements. The fusible element, which has a smaller cross-section than the other conductors in the circuit, is heated by the current flowing through it and melts if the relevant rated current of the fuse is significantly exceeded for a predetermined period of time. Due to its good insulating properties, ceramic is usually used as the material for the insulating body.Such a fuse link is known in principle, for example from the European patent specification EP 0 917 723 B1 or the German laid-open specifications DE 10 2014 205 871 A1 and DE 10 2016 211 621 A1.

[0004] Fuses are available in various designs. In addition to simple device fuses, which consist of a simple glass cylinder containing the fusible element, there are also designs in which the ceramic body is filled with sand – usually quartz sand. A distinction is made between types with solidified and unsolidified quartz sand. In a sand-solidified fuse, the fusible element is surrounded by quartz sand. The fuse housing is usually formed by a ceramic body in which the solidified sand, the electrical connections, and the fusible element are housed or held.The quartz sand acts as an arc extinguishing agent: if the rated current of the fuse is significantly exceeded - for example due to a high short-circuit current - this causes the fuse to blow. The fuse element initially melts and then evaporates due to the high temperature build-up. This creates an electrically conductive plasma, which initially maintains the flow of current between the electrical connections - an arc is formed. As the metal vapor of the evaporated fuse element condenses on the surface of the quartz sand grains, the arc is cooled again. As a result, the resistance inside the fuse link increases to such an extent that the arc is finally extinguished. The electrical line protected by the fuse element is thus interrupted.

[0005] In the field of fuses, low-voltage high-performance fuses, so-called NH fuses, as well as semiconductor protection fuses, so-called HLS fuses, such as those sold under the product name SITOR, are generally known from the state of the art. NH fuses typically use one or more fusible elements in the form of metal strips. The fusible elements usually have so-called narrow-point rows for selectively switching off the fuse. Furthermore, at least one solder deposit can be applied to one or more of the fusible elements, with the help of which the overload characteristic of the fuse can be influenced. The let-through energy value I 2< t, which is decisive for the breaking behavior of the fuse, is relatively high for NH fuses, which is why they have a rather slow characteristic.

[0006] If the fusible element is heated by an electrical overload current to a temperature above the melting temperature of the solder, the solder diffuses into the fusible element material and forms an alloy with it. This increases the electrical resistance of the fusible element, which causes it to heat up further. This accelerates the diffusion process until the fusible element is completely dissolved in the area of ​​the solder deposit and breaks, interrupting the current flow. In the event of a brief, permissible overcurrent, the NH fuse does not trip prematurely. However, if a short-circuit current occurs, the fusible element ruptures at the narrow rows. This creates several small, series-connected arcs whose voltages add up and thus lead to faster tripping of the fuse.NH fuses are used, for example, to protect systems or control cabinets from fire, for example due to overheated connecting cables.

[0007] Operators of electrical systems are increasingly expressing a desire to be able to quickly record the status of an electrical system. In the past, this was often achieved by visual inspection - in the case of fuses, for example, by equipping the fuses with an indicator that visually signals the blown fuse on the outside of the fuse housing. In the future, however, there will be increasing demands for the ability to query this information at any time and, if possible, from any location, for example via a control room. For this reason, electrical installation devices are increasingly being equipped to provide information about their operating status. Electrical switching devices, such as fire protection devices, which already have their own control logic, can be equipped to process and provide the relevant information with relatively little effort.

[0008] For fuses, there are corresponding solutions: a communication module that can be attached to the fuse captures and forwards the "tripped" information optically provided by the indicator. However, attachable solutions have the disadvantage that they require additional installation space and can therefore only be implemented in existing installations with relatively high expenditure. For a simple retrofit application, where an existing conventional fuse without a communication module is used, ie If a fuse without a measuring, evaluation and communication unit is replaced by a new fuse with a corresponding communication module in the sense of retrofitting or modernising the system, these attachable solutions are often not used because the additional installation space required for this is not available.

[0009] To solve this problem of limited installation space, which primarily occurs in retrofit applications, the international patent application WO 2017 / 078525 A1 describes a fuse in which a current sensor is integrated into the pressure body of the fuse. This current sensor can measure the current flow through the fuse during normal operation and transmit the data to a query unit located outside the fuse. However, since comparatively high temperatures can also occur in a fuse, it is questionable how reliably a sensor integrated into the pressure body of the fuse will function over the fuse's service life.

[0010] Furthermore, from the document WO 2014 / 026702 A1, a fuse holder for insertion into a fuse unit is known, which has a housing in which a fuse link, a coil device and a measuring device connected to the latter are located.

[0011] Furthermore, the document DE 3411323 A1 discloses a switching flap to which an NH fuse with a pressure body and two blade contact pieces can be fastened, wherein a ring current transformer is pushed over one of the two blade contact pieces and is held by means of an O-ring on one end side of the pressure body.

[0012] The invention is therefore based on the object of providing a fuse with an integrated measuring function which at least partially overcomes the problems mentioned above.

[0013] This object is achieved according to the invention by the fuse with integrated measuring function according to independent claim 1. Advantageous embodiments of the fuse according to the invention are the subject of the dependent claims.

[0014] The inventive fuse with integrated measuring function comprises a measuring device with a current transformer and an electronic assembly for determining the electrical current flowing through the fuse, as well as a pressure body with a first receiving space for receiving a fusible element of the fuse, wherein the first receiving space is delimited in a longitudinal direction of the fuse by a closure element and in a direction orthogonal to the longitudinal direction by the pressure body. Furthermore, the pressure body has a second receiving space, spatially separated from the first receiving space, for receiving the measuring device of the fuse, wherein the second receiving space for receiving the measuring device is formed in a wall section of the pressure body.

[0015] A pressure body, which can also be referred to as a pressure housing or fuse body, primarily serves to absorb the pressure that occurs when the fuse is heated or triggered, which is why high demands are placed on the mechanical strength and stability of the pressure body. The pressure body according to the invention for a fuse with integrated measuring function also serves to accommodate a measuring device of the fuse and protect it from damage. For this purpose, the pressure body has, in addition to the first receiving space for accommodating a fusible element, a second receiving space for accommodating the measuring device, which is advantageously closable in the longitudinal direction, for example by the closure element. The second receiving space is oriented both outwards and inwards in a direction orthogonal to the longitudinal direction. ieThe pressure hull is spatially separated from the first receiving chamber by the pressure hull. This effectively protects the measuring device, which can be arranged in the second receiving chamber, against disruptive environmental influences such as dust, moisture, or dirt, as well as against damage to the measuring device caused by a pressure increase inside the pressure hull due to the triggering of the fuse.

[0016] This allows for the realization of a fuse with an integrated measuring function, in which the electrical current flowing through the fuse can be measured directly at the fuse, without significantly affecting the design or size – and thus the technical properties of the fuse. This makes it possible to create a fuse with the external dimensions of a conventional NH fuse, which can also be used for retrofit applications and enables the status of both the fuse and the electrical system it protects without the need for an on-site visual inspection.

[0017] In an advantageous further development of the fuse, the pressure body has a substantially hollow cylinder-like shape, which can be closed at each end with a closure element.

[0018] A hollow cylindrical shape, which can also be referred to as a prism-like shape, represents a three-dimensional form consisting of a base area and a height oriented orthogonally to it. Such three-dimensional forms have the advantage that, with the right choice of material, they can be easily manufactured using extrusion. However, other manufacturing processes, particularly additive manufacturing processes, colloquially known as 3D printing, are also possible.

[0019] In a further advantageous development, the second receiving space has an annular first section for receiving a current transformer and a second section for receiving an electronic assembly.

[0020] The second receiving chamber, which serves to accommodate the measuring device and represents a cavity formed in a wall section of the pressure hull, can be divided into two partitions: an annular first section for accommodating the current transformer of the measuring device and a second section for accommodating the electronic assembly of the measuring device. The two sections do not necessarily have to be separated by a partition wall or similar, but can be arranged directly adjacent to each other or even merge into one another.

[0021] In a further advantageous development, the first section and / or the second section can be closed by at least the closure element or other closure elements.

[0022] Advantageously, both the first section and the second section can be closed with the aid of the at least one closure element, effectively protecting the components of the measuring device arranged in the sections from environmental influences such as dust, dirt, or moisture. This can reduce the assembly effort.

[0023] In a further advantageous development, the pressure body is formed in one piece.

[0024] The one-piece design—particularly with regard to the production of the pressure hull using an additive manufacturing process—has the advantage of eliminating downstream assembly steps. This can further reduce assembly costs.

[0025] In a further advantageous development, the pressure body is made of a ceramic material or a thermostable plastic.

[0026] Ceramic materials are particularly suitable for the production of pressure vessels due to their high compressive strength. Thermostable plastics, on the other hand, are characterized by their simplified processing and comparatively low manufacturing costs, provided they are sufficiently heat-stable.

[0027] In a further advantageous development of the fuse, the current transformer is arranged in the first section of the second receiving space, while the electronic assembly is arranged in the second section of the second receiving space.

[0028] The current transformer located in the second housing serves, on the one hand, as a current sensor, which transmits the recorded current values ​​to the electronic module, where the measured values ​​are further processed. On the other hand, the energy required for this is also generated by the current transformer through electromagnetic induction from the primary current, i.e., the operating current of the fuse. The current transformer thus also serves as an energy source for the electronic module. In order to provide sufficient energy for the electronic module even at low operating currents of the fuse, and thus ensure the reliability of the measuring device, the current transformer must be comparatively large.

[0029] At the same time, the fuse must be kept compact in order to be suitable for retrofitting or modernising existing systems where a conventional fuse without a measuring device is replaced. Since the fuse ideally has the dimensions of a standardised NH fuse, the second accommodation space in which the measuring device is accommodated and held is very limited, particularly in the axial direction, i.e. in the longitudinal direction. In order to be able to arrange the largest possible current transformer in a first section of the second accommodation space, the electronics module is arranged laterally, i.e. in the radial direction, next to the current transformer in a second section of the second accommodation space.In this way, the current transformer's dimensions can be optimized to maximize the energy supplied to the electronic assembly. This makes it possible to construct a fuse with integrated measuring functionality that does not require an external power source to supply the measuring device.

[0030] In a further advantageous development of the fuse, the electronic assembly has a transmission device for transmitting a measurement signal detected by the measuring device to a receiving device arranged outside the fuse.

[0031] Using the transmission device, the measured data or further processed data based on this data can be transmitted to an external unit, such as a data collection device or a control room. This makes it possible to determine the operating status of the fuse at any time without requiring a technician or installer to inspect the fuse on-site.

[0032] In a further advantageous development of the fuse, the transmission of the measuring signal from the transmitting device to the receiving device is wireless.

[0033] Wireless transmission of data to the external receiving device significantly simplifies the installation effort of the fuse. Common transmission methods such as Bluetooth, RFID (both active and passive), ZigBee, etc. can be used for wireless transmission of data—measured values ​​or preprocessed data based on measured values—from the transmitting device to the receiving device. The energy required for the transmission is advantageously recovered from the primary current using electromagnetic induction with the help of the current transformer.

[0034] In a further advantageous development of the fuse, the total installation space required for the fuse corresponds to the installation space of a standardized NH fuse.

[0035] Since the fuse according to the invention with integrated measuring function corresponds in terms of its size to the size of a conventional NH fuse, it is also suitable for retrofit applications in the context of retrofitting or modernizing existing systems in which a conventional fuse without measuring device is replaced by a fuse with integrated measuring function.

[0036] In the following, an embodiment of the pressure body of the fuse according to the invention is explained in more detail with reference to the attached figures. In the figures: Figure 1 shows a schematic representation of a NH fuse known from the prior art; Figures 2 to 4 show schematic representations of the pressure body of the fuse according to the invention with integrated measuring function in various views.

[0037] In the various figures of the drawing, identical parts are always provided with the same reference symbol. The description applies to all drawing figures in which the corresponding part can also be seen.

[0038] Figure 1shows a schematic diagram of the basic structure of a standardized NH fuse, as is already known from the prior art. The fuse 1 has two connection elements 3, which are made of an electrically conductive material, for example copper. In the illustrations, the connection elements 3 are designed as blade contacts - this, however, is not essential to the invention. The connection elements 3 are mechanically firmly and tightly connected to a protective housing 2 with a height H, which is made of a solid, non-conductive and, if possible, heat-resistant material, for example a ceramic, and serves as a pressure body for the fuse 1. The protective housing 2 generally has a tubular or hollow cylindrical basic shape and is closed pressure-tight to the outside, for example with the help of two closure caps 4.The connection elements 3 each extend through an opening formed in the closure caps 4 into the cavity of the protective housing 2. In this cavity, at least one so-called fusible element 5 is arranged, which electrically connects the two connection elements 3 to one another.

[0039] The remaining cavity is usually completely filled with an extinguishing agent 6, which serves to extinguish and cool the fuse 1 in the event of a triggering and completely surrounds the fusible element 5. Quartz sand, for example, is used as the extinguishing agent 6. Instead of the Figure 1In addition to the one fuse element 5 shown, it is also possible to arrange several fuse elements 5 electrically connected in parallel to one another in the protective housing 2 and to contact them accordingly with the two contact elements 3. The type, number, arrangement, and design of the fuse elements 3 can influence the tripping characteristic—and thus the tripping behavior—of the fuse 1.

[0040] The fusible element 5 is generally made of a highly conductive material such as copper or silver and has, along its length, i.e. in its longitudinal direction L, several rows of constrictions 7 and one or more solder deposits 8 - so-called solder points. The longitudinal direction L is therefore parallel to an imaginary connecting line between the two connecting elements 3. The tripping characteristic of the fuse 1 can also be influenced and adapted to the respective application via the rows of constrictions 7 and the solder points 8. At currents that are lower than the nominal current of the fuse 1, only so much power loss is converted in the fusible element 5 that it can be quickly dissipated to the outside in the form of heat via the quenching sand 6, the protective housing 2 and the two connecting elements 3. The temperature of the fusible element 5 does not rise above its melting point.If a current flows that lies within the overload range of fuse 1, the temperature inside fuse 1 continues to rise until the melting point of fuse element 5 is exceeded and it melts at one of the narrow rows 7. In the case of high fault currents—such as those that occur due to a short circuit—so much energy is converted in fuse element 5 that it is heated practically along its entire length and, as a result, melts simultaneously at all narrow rows 7.

[0041] Since liquid copper or silver still has good electrical conductivity properties, the current flow is not interrupted at this point. The melt formed from the fusible element 5 is consequently heated further until it finally changes to a gaseous state, forming a plasma. This creates an arc to maintain the current flow via the plasma. In the final stage of a fuse shutdown, the conductive gases react with the extinguishing agent 6, which in conventional fuses 1 usually consists of quartz sand. This is melted due to the extremely high temperatures in the vicinity of the arc caused by the arc, which leads to a physical reaction between the molten fusible element material and the surrounding quartz sand 6. Since the resulting reaction product is electrically non-conductive, the current flow between the two connecting elements 3 quickly drops to zero.However, it should be noted that a certain mass of fusible element material also requires a corresponding mass of extinguishing agent. This is the only way to ensure that sufficient extinguishing agent 6 is still available at the end of the safety shutdown to effectively bind the entire conductive plasma.

[0042] In the Figures 2 to 4An embodiment of the pressure body 10 of the fuse according to the invention with integrated measuring function is shown schematically. The pressure body 10 is formed in one piece from a suitable material, for example a ceramic or a thermostable plastic. It is shaped as a hollow body, the essentially cylindrical inner wall 11 of which delimits a first receiving space 20, which extends along a longitudinal direction L, in a radial direction R oriented orthogonally to the longitudinal direction L. In the longitudinal direction L and in the opposite direction, the pressure body 10 is delimited by an end face 12-1 and 12-2, respectively, on each of which a closure element (not shown) of the fuse can be mounted in order to close the first receiving space 10 in the longitudinal direction L and in the opposite direction.The height H of the pressure hull 10 corresponds to the height of a standardized NH fuse, as shown in . Figure 1 shown and described above.

[0043] The first receiving space 10 serves to accommodate and secure a fusible element (not shown) of the fuse. Furthermore, the first receiving space 10 can be filled with a suitable extinguishing agent, such as quartz sand, to improve the triggering properties of the fuse. The first receiving space 10 thus corresponds to the cavity of the above-mentioned Figure 1 described fuse.

[0044] In addition, the pressure body 10 has a second receiving space 30 formed in a wall 13 of the pressure body 10. The second receiving space 30 is intended to accommodate a measuring device (not shown) of the fuse in order to measure the electrical current flowing through the fuse, process the measured signal if necessary, and transmit it to a higher-level location, for example a data collector or a control room. Structurally, the second receiving space 30 represents a pocket-like depression formed in the first end face 12-1. The second receiving space 30 is delimited by the pressure body 10 towards the other end face 12-2, as well as outwards and inwards towards the first receiving space 31.

[0045] The measuring device (not shown) to be arranged in the second receiving space 30 essentially consists of a current transformer and an electronic assembly electrically connected to it. Therefore, the second receiving space 30 is divided into a ring-shaped first section 31, which serves to accommodate the ring-shaped current transformer, and a second section 32, which is designed to accommodate the electronic assembly. The two sections 31 and 32 do not have to be separated from each other by a partition or the like, but can rather be arranged directly adjacent to each other or even merge into one another.

[0046] The current transformer primarily serves as a current sensor, detecting the electrical current flowing through the fuse. The detected current values ​​are then transmitted to the electronic assembly. Furthermore, the energy required for the electronic assembly can also be generated from the primary current, i.e., the operating current of the fuse, using the current transformer through electromagnetic induction. In addition to its measuring function, the current transformer also serves as a power source for the electronic assembly. This makes it possible to construct a fuse with an integrated measuring function that does not require an external power source to supply the measuring device with energy.

[0047] The electronic assembly must be designed to be as compact as possible, as the available space in the second section 32 of the second receiving space 30 is severely limited. A compact design is possible, for example, through the use of a compact circuit board with integrated circuits. In order to transmit the measurement data acquired by the measuring device, or further processed data based on this measurement data, to a receiving device located outside the fuse—for example, a data collection device or a control room—the electronic assembly has a suitable transmission device. All common transmission methods, such as Bluetooth, RFID (both active and passive), ZigBee, etc., are suitable for this transmission.In this way, it is possible to determine the operating status of the fuse at any time without the need for a technician or installer to visually inspect the fuse on site.

[0048] The fuse according to the invention is characterized by the fact that the measuring and communication technology is not located in a separate housing, but rather in a recess formed in the pressure vessel. This has the advantage that no additional space is required for the measuring device, which would lead to a shortening of the pressure vessel and thus a reduction in the achievable nominal voltage of the fuse. List of reference symbols

[0049] 1Fuse 2Protective housing / pressure hull 3Connection element 4Closing cap 5Fusible element 6Extinguishing agent / extinguishing sand 7Narrow point row 8Solder deposit 10Pressure hull 11Inner wall 12-1First end face 12-2Second end face 13Wall 20first recording room 30second recording room 31first section 32second section HHeight LLongitudinal direction Rradial direction

Claims

1. Fuse with an integrated measurement function, comprising a measurement device having a transformer and an electronics assembly for determining the electric current flowing through the fuse, having a pressure body (10), comprising - a first reception space (20) for receiving a fuse element of the fuse, wherein the first reception space (20) is limited in a direction of longitudinal extent (L) of the fuse by way of a closure element and in a direction (R) orthogonal to the direction of longitudinal extent (L) by way of the pressure body (10), - a second reception space (30) physically delimited from the first reception space (20) for receiving the measurement device of the fuse, characterized in that the second reception space (30) is designed to receive the measurement device in a wall section (13) of the pressure body (10).

2. Fuse according to Claim 1, wherein the pressure body (10) has a substantially hollow-cylindrical shape, which can be closed at the ends using a respective closure element.

3. Fuse according to either one of the preceding claims, wherein the second reception space (30) has an annular first section (31) for receiving a transformer and a second section (32) for receiving an electronics assembly.

4. Fuse according to Claim 3, wherein the first section (31) and / or the second section (32) can be closed by at least the closure element or other closure elements.

5. Fuse according to any one of the preceding claims, wherein the pressure body (10) is designed in one part.

6. Fuse according to any one of the preceding claims, wherein the pressure body (10) is formed from a ceramic material or a thermostable plastic.

7. Fuse according to Claim 3, - wherein the transformer is arranged in the first section (31) of the second reception space (30), and - wherein the electronics assembly is arranged in the second section (32) of the second reception space (30).

8. Fuse according to Claim 7, wherein the electronics assembly has a transmission device in order to transmit a measurement signal detected by the measurement device to a reception device arranged outside of the fuse.

9. Fuse according to Claim 8, wherein the measurement signal is transmitted wirelessly by the transmission device to the reception device.

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