Device for current measurement using CNB fibers

Abstract

Device (1) for measuring current, comprising - at least two external contacts (21) which are designed to electrically connect the device (1) to a circuit existing outside the device (1), - a measuring shunt (4) which is arranged with respect to an electric current flow between the at least two outer contacts (21) and is electrically connected to them, wherein the measuring shunt (4) has two measuring contacts (3) which are configured to allow a signal to be measured via the measuring contacts which is representative of the electric current flowing through the measuring shunt (4), characterized in that the measuring shunt (4) has at least one CNB fiber (Carbon Nano Based material).

Description

State of the art

[0001] The invention relates to a device for current measurement according to claim 1.

[0002] To measure current in an electrical circuit, measuring shunts are often used between the components of the circuit. A measuring shunt is usually a low-ohm resistor inserted into the signal path, at whose two terminals a voltage proportional to the current to be measured can be tapped as a measurement signal. Such measuring shunts are embedded in busbars, for example, for high currents to be measured. The busbar is split, for example, and the measuring shunt is soldered or welded into the separation point. To ensure the measurement is sufficiently accurate, the resistance of the measuring shunt must have a low tolerance and be as independent of the component temperature as possible. For this reason, a copper connection, for example, cannot be used as a measuring shunt because copper has a high resistance-temperature coefficient.

[0003] Current designs have the disadvantage that their construction is relatively rigid mechanically, requiring tight mechanical tolerances during manufacturing. Furthermore, manufacturing becomes more complex and expensive due to the many individual components, such as measuring shunts, busbars, and mechanical load-bearing devices, which are subject to stringent requirements regarding tight manufacturing tolerances. A device for measuring current is shown, for example, in DE 10 2015 218 796 A1. Advantage of the invention / Disclosure of the invention

[0004] Accordingly, it is an object of the present invention to provide a device of the type mentioned above which is mechanically more flexible and yet enables reliable current measurement, so that the above disadvantages are eliminated or minimized.

[0005] This task is performed by the current measuring device, which - at least two external contacts designed to electrically connect the device to an electrical circuit existing outside the device, - a measuring shunt, which is arranged between the at least two external contacts with respect to an electrical current flow and is electrically connected to them, wherein the measuring shunt has two measuring contacts configured to measure a signal via the measuring contacts that is representative of the electrical current flowing through the measuring shunt. This is achieved according to the invention in that the measuring shunt has at least one CNB fiber. In particular, the measuring signal is tapped over the length of the at least one CNB fiber. In other words, the CNB fiber advantageously serves as a measuring shunt.

[0006] CNB fibers are fibers based on carbon nanomaterials (carbon nano-based material), such as graphene or carbon nanotubes (CNT). CNB materials have the advantage of being very pliable and therefore flexible. Their use in the measuring shunt in the device according to the invention results in a pliable and flexible connection in the device. This creates a device for current measurement that is mechanically more flexible than devices previously known from the prior art. Thanks to this pliable and flexible connection in the device, additional mechanical relief in the device is not necessary. This also reduces the tolerance requirements for the individual components of the device and the device as a whole, and thus also reduces manufacturing costs. By incorporating the device according to the invention into an electrical circuit orbetween two components of an electrical circuit, the components are movable relative to one another and there is a greater degree of freedom in the arrangement of the components relative to one another or within a installation space. A flexible current measuring device is also easier to install than a relatively rigid current measuring device. Furthermore, a current measuring device with a measuring shunt containing CNB fibers is lighter than a conventional current measuring device with a metallic measuring shunt. Another advantage is that the resistance of the measuring shunt can be adjusted for the respective application of the measuring shunt by changing the number of CNB fibers, the length of the CNB fibers and the selected material properties, such as electrical conductivity.

[0007] Typically, the voltage between the two measuring contacts of a measuring shunt is tapped. Combined with the known electrical resistance of the measuring shunt, the electrical current flowing through the measuring shunt can be easily calculated. This calculation can, for example, be performed in a separate evaluation unit. The measured voltage signal is sent to the evaluation unit, for example, and the current is calculated together with the electrical resistance of the measuring shunt stored in the evaluation unit.

[0008] Advantageous further developments of the invention are the subject of the subclaims.

[0009] In a further development, the measuring shunt is designed to have a large number of CNB fibers. In a particularly advantageous further development, the CNB fibers are combined in at least one CNB fiber bundle. For example, the measuring shunt can consist of a large number of CNB fibers combined in one or more bundles. The above-mentioned advantages are enhanced when the measuring shunt has the highest possible proportion of CNB fibers and, ideally, is even made entirely of CNB fibers.

[0010] For use in the measuring shunt, it has proven advantageous for the CNB fibers to have an electrical resistance that is as temperature-independent as possible. Studies have shown that the temperature coefficient value of the electrical resistance of the CNB fiber is preferably less than 2*10^ -3 *1 / K and in particular less than 1.7*10^ -3*1 / K. This ensures that the current measurement is reliably accurate, even if the temperature of the measuring shunt or the temperature of a component in which the measuring shunt is installed changes significantly. Ideally, the temperature coefficient is 0.

[0011] In a first advantageous embodiment, particularly for measuring shunts in high-current applications, the device has at least two measuring rails, wherein one of the at least two measuring rails is arranged between one of the at least two outer contacts and the measuring shunt and connects the measuring shunt to one of the at least two outer contacts. It is particularly advantageous here if the measuring rails also have CNB fibers. This provides a device for measuring high currents that is also mechanically more flexible than high-current measuring devices known from the prior art. Furthermore, this device is also lighter than devices with metallic measuring rails and a metallic measuring shunt.

[0012] In an advantageous further development of this first embodiment, it is provided that the measuring rails and the measuring shunt have different CNB fibers, wherein in particular the CNB fibers of the measuring rails have a higher electrical conductivity than the CNB fibers of the measuring shunt. Additionally or alternatively, it can also be provided that the CNB fibers of the measuring shunt have a higher electrical resistance and a lower temperature coefficient value of the electrical resistance than the CNB fibers of the measuring rails. The same applies to CNB fiber bundles if the CNB fibers of the measuring rails and / or the CNB fibers of the measuring shunt are combined into bundles.

[0013] This offers the advantage of using CNB fibers with properties optimized for the intended use, whether as a measuring bar or measuring shunt. This, in turn, creates a good and reliable device for current measurement.

[0014] In an alternative second embodiment of the current measuring device, the measuring shunt is connected directly to the at least two external contacts. In other words, this embodiment of the device does not have separate measuring rails. This embodiment is particularly suitable for use with lower currents. By omitting separate measuring rails, the device has fewer components and is thus simpler in design. Furthermore, this device is also cheaper to manufacture. Furthermore, power loss is reduced if the device only has one measuring shunt and the corresponding contact points.

[0015] The use of CNB fibers in the measuring shunt, or of CNB fibers or CNB fiber bundles as a measuring shunt, offers the advantage of new contact options between the CNB fiber and the other components of the device, such as the measuring rail or external contact points. In all embodiments or further developments, the measuring shunt can have internal contact points to the two measuring contacts and to the at least two measuring rails or to the external contact points, with at least one connection to the internal contact points being formed by sewing, knotting, a crimped tab, a snap fastener, or splicing. Advantageously, each internal contact point at which the CNB fibers of the measuring shunt are in contact with another component of the device is designed in one of the above-mentioned ways. A suitable contact type is selected depending on the contact partner.For example, the CNB fibers of the measuring shunt can be sewn or knotted at their contact points with the measuring rail or other components located outside the device. If the measuring rails also consist of CNB fibers, the measuring rails and the measuring shunt can be connected by splicing. To provide external contact points, tabs can be crimped onto the measuring shunt. The connection between the measuring shunt and the measuring contacts can also be created by splicing or sewing.

[0016] In a further embodiment, which can also be a development of the first two embodiments, the measuring shunt comprises a first bundle of CNB fibers, via which the measurement signal can be measured, and at least one second bundle of CNB fibers that is electrically insulated from the first bundle of CNB fibers. The measurement signal is spatially guided from the second measuring contact to the first measuring contact by the second bundle of CNB fibers. This results in the advantage that the measurement signal of the current measurement can be tapped over a closer spatial distance than the entire length of the measuring shunt and forwarded to a possible evaluation unit.

[0017] Additionally or alternatively, one embodiment may also provide for the measuring shunt to comprise a plurality of CNB fiber bundles that are electrically insulated from one another. It is particularly advantageous if the bundles are twisted together, thereby reducing parasitic inductance in the measuring shunt.

[0018] In a further development, the bundles in the measuring shunt could comprise different CNB fibers, with at least one bundle containing a first type of CNB fiber and at least one other bundle containing a second type of CNB fiber, the first type of CNB fiber having a lower resistance temperature coefficient value than the second CNB fiber, the bundle with the first type of CNB fiber being configured to tap the signal for current measurement via it, and the bundle with the second type of CNB fiber being configured to measure a temperature signal via it. For example, the second type of CNB fiber can have a higher electrical resistance than the first type of CNB fiber. This offers the advantage that both the current and the temperature can be measured with one measuring shunt.This makes it possible to detect the ambient temperature of the measuring shunt or to determine the temperature of the external contact points.

[0019] The device according to the invention and its further developments or embodiments can be used, for example, as a current-carrying connection in power electronics, a control cabinet technology, an electric motor or a battery technology. drawing Fig. 1 shows a first example of a device according to the invention, in which at least one CNB fiber bundle serves as a measuring shunt Fig. 2 shows a second example of a device according to the invention, in which at least a first CNB fiber bundle serves as a measuring shunt and the measuring rails consist of a second CNB fiber bundle Fig. 3 shows a third example of a device according to the invention without measuring rails, in which at least one CNB fiber bundle serves as a measuring shunt Fig. 4 shows a fourth example of a device according to the invention, in which the measuring shunt has at least two CNB fiber bundles, wherein one CNB fiber bundle serves for the measurement signal feedback Fig. 5 shows a fifth example of a device according to the invention, in which at least two CNB fiber bundles serve as a measuring shunt, whereby two different measuring signals are tapped Description of the embodiment

[0020] Fig. 1 shows a first example of a device 1 according to the invention. The device 1 is used for current measurement. The device 1 has at least two external contacts 21, which are designed to electrically connect the device 1 to an electrical circuit existing outside the device and its components. The device 1 also has a measuring shunt 4. This measuring shunt 4 is arranged between the at least two external contacts 21 with respect to an electrical current flow and is electrically connected to them, for example via two measuring rails 2. In this example, the measuring shunt 4 has two internal contact points 22, with which the measuring shunt 4 is directly connected to the measuring rails 2. The connection is created, for example, by sewing, knotting, or a crimped tab. The measuring shunt 4 itself has a plurality of CNB fibers that are combined to form at least one bundle 45.At its outer end regions, the at least one CNB fiber bundle 45 has a measuring contact point 41 at which measuring contacts 3 tap a measuring signal 5 and forward it to a measuring amplifier 6, shown here as an example. Alternatively, the measuring amplifier 6 can also be an evaluation unit in which the measured signal 5 is converted into a value for the current intensity.

[0021] Fig. 2 shows a second example of a device 1 according to the invention. The device 1 according to Fig. 2 differs from the device 1 according to Fig. 1 in that, in this second example, the measuring rails 23 also consist of CNB fiber bundles. Advantageously, the measuring rails 23 consist of different CNB fibers than the measuring shunt 4. For example, the CNB fibers of the measuring rails 23 have a high electrical conductivity, while the CNB fibers of the measuring shunt 4 have a higher electrical resistance with a temperature coefficient that is as constant as possible.

[0022] Fig. Figure 3 shows a third example of a device 1 according to the invention. This device 1 differs from the first two examples of a device 1 in that the measuring shunt 4 is connected directly to the external contacts 21, thus eliminating the need for measuring rails. The external contacts 21 and the measuring contacts 3 are connected to the inner contact points 22, 41 of the measuring shunt 4.

[0023] Fig. 4 shows a fourth example of a device 1 according to the invention. This device 1 differs from the second example of a device 1 in that the measuring shunt 4 has at least two bundles 45, 42 of CNB fibers. The first bundle 45 serves as the measuring shunt 4. The second bundle 42 is electrically insulated from the first bundle 45 and carries the measuring signal 5 from the second measuring contact point 41b into the spatial proximity of the first measuring contact point 41a, so that the measuring signal 5 can be applied over a spatially narrower area than the entire length of the measuring shunt 4.

[0024] Alternatively, this example could also be realized with normal measuring rails 2 as in the first example or without measuring rails as in the third example.

[0025] Fig.Figure 5 shows a fifth example of a device 1 according to the invention. This device 1 differs from the first example of the device 1 in that the measuring shunt 4 has at least two CNB fiber bundles 45, 46, wherein the bundles 45, 46 consist of different CNB fibers and are optimized for different functions. The first CNB fiber bundle 45 serves as the measuring shunt 4 for current measurement. The second CNB fiber bundle 46 serves as the measuring shunt 4 for a second measurement signal 7, such as the temperature.

[0026] Alternatively, this example could also be realized with measuring rails 2 made of a third type of CNB fibers as in the second example or without measuring rails as in the third example.

Claims

[1] Device (1) for current measurement, comprising - at least two external contacts (21) which are designed to electrically connect the device (1) to an electrical circuit existing outside the device (1), - a measuring shunt (4) which is arranged with respect to an electrical current flow between the at least two external contacts (21) and is electrically connected thereto, wherein the measuring shunt (4) has two measuring contacts (3) which are arranged so that a signal can be measured via the measuring contacts which is representative of the electrical current flowing through the measuring shunt (4), characterized by that the measuring shunt (4) has at least one CNB fiber (Carbon Nano Based material). [2] Device (1) according to claim 1, characterized by that the measuring shunt (4) has a plurality of CNB fibers, in particular which are combined in at least one CNB fiber bundle (45). [3] Device (1) according to one of the preceding claims, characterized by that an absolute value of a temperature coefficient of an electrical resistance of the CNB fiber is less than 2*10^-3 1 / K, in particular less than 1.7*10^-3 1 / K. [4] Device (1) according to one of the preceding claims, characterized by that the device (1) has at least two measuring rails (2), wherein one of the at least two measuring rails (2) is arranged between one of the at least two external contacts (21) and the measuring shunt (4) and connects the measuring shunt (4) to one of the at least two external contacts (21). [5] Device (1) according to claim 4, characterized by that the measuring rails (2) have CNB fibers (23). [6] Device (1) according to claim 5, characterized bythat the measuring rails (2) and the measuring shunt (4) have different CNB fibers (23), wherein in particular the CNB fibers (23) of the measuring rails (2) have a higher electrical conductivity than the CNB fibers of the measuring shunt (4) and / or the CNB fibers of the measuring shunt (4) have a higher electrical resistance and a smaller temperature coefficient value of the electrical resistance than the CNB fibers (23) of the measuring rails (2). [7] Device (1) according to one of the preceding claims 1 to 3, characterized by that the measuring shunt (4) is directly connected to at least two external contacts (21). [8] Device (1) according to one of the preceding claims, characterized bythat the measuring shunt (4) has inner contact points (22, 41) to the two measuring contacts (3) and to the at least two measuring rails (2) or to the outer contact points (21), wherein at least one connection to the inner contact points (22, 41) is formed by means of sewing, knotting, a crimped tab, a snap fastener or splicing. [9] Device (1) according to one of the preceding claims, characterized by that the measuring shunt (4) has a first bundle (45) of CNB fibers, via which the signal (5) can be measured, and at least one second bundle (42) of CNB fibers which is electrically insulated from the first bundle (45) of CNB fibers, wherein the measured signal (5) is spatially guided by the second bundle (42) of CNB fibers from the second measuring contact (41b) to the first measuring contact (41a). [10] Device (1) according to one of the preceding claims, characterized bythat the measuring shunt (4) has a plurality of CNB fiber bundles (45) which are electrically insulated from one another. [11] Device (1) according to claim 10, characterized by that the bundles (45) are twisted together, whereby a parasitic inductance in the measuring shunt (4) is reduced. [12] Device (1) according to claim 10 or claim 11, characterized bythat the bundles (45, 46) have different CNB fibers, wherein at least one bundle (45) contains a first type of CNB fibers and at least one other bundle (46) contains a second type of CNB fibers, wherein the first type of CNB fibers has a lower resistance temperature coefficient value than the second CNB fibers, wherein the bundle (45) with the first type of CNB fibers is set up so that the signal (5) for the current measurement is tapped therethrough, and wherein the bundle (46) with the second type of CNB fibers is set up so that a temperature signal (6) can be measured therethrough. [13] Device (1) according to one of the preceding claims, characterized by that the CNB fibers are graphene or CNT fibers (Carbon Nano Tube).

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