Shunt comprising a reference conductor

Abstract

The invention relates to a shunt (1) for measuring an electric current. The shunt (1) has an input region (2) with at least one input contact (2a), and the shunt (1) has an output region (4) with at least one output contact (4a), wherein the shunt has at least one measuring section (3) which is electrically connected between the input region (2) and the output region (4), and the measuring section (3) has an outer surface. The invention is characterized in that at least one electrically conductive reference conductor (5) is arranged on the outer surface, said reference conductor being electrically insulated from the measuring section (3), and the reference conductor (5) covers at least an eighth of the outer surface.

Description

[0001] Shunt with reference conductor

[0002] The invention relates to a shunt for measuring electrical current, wherein the shunt has an input region with at least one input contact and the shunt has an output region with at least one output contact, wherein the shunt has at least one measuring section which is electrically connected between the input region and the output region and wherein the measuring section has an outer surface.

[0003] It also relates to a method for measuring electric current using a shunt through which the current to be determined flows.

[0004] A shunt, also called a shunt resistor or current measuring resistor, is an electrical component used to measure electrical currents, especially larger currents such as those in the range of over 100 amperes. For this purpose, the current to be measured is passed through the shunt. A measuring section of the shunt has a defined resistance, and by measuring the voltage drop along this measuring section, the current strength can be determined. Such shunts suffer from the thermal stress caused by the high current, which impairs the measurement result because the resistance of the measuring section also changes with temperature. Therefore, complex cooling devices are often provided, but these inadequately solve the problem.

[0005] WO 2022144586 A1 discloses a device in which the temperature is monitored via multiple sensors. Knowledge of the temperature and the associated change in resistance can be incorporated into the calculation of the current to be determined. However, this method is complex and requires precise knowledge of the influence of temperature on the resistance.

[0006] The object of the invention is therefore to provide a shunt, a current measuring device and a method as mentioned above which has a lower temperature dependence and is of simple construction.

[0007] This object is achieved according to the invention in that at least one electrically conductive reference conductor is arranged in or on the measuring section, which is electrically insulated from the measuring section.

[0008] "Arranged in or on the measuring section" means that the reference conductor can be arranged on the outer surface of the measuring section and / or also arranged within the measuring section. It can therefore, for example, be fully or partially embedded in the material of the measuring section. It is essential that the reference conductor and the measuring section are electrically insulated from each other.

[0009] It is also solved by passing the current through a measuring section of the shunt and measuring the voltage drop along the measuring section, a reference conductor arranged in or on the measuring section, which is electrically insulated from the measuring section, has a reference current flowing through it and the voltage drop along the reference conductor and / or the current strength of the reference current is measured and that the calculation of the current to be determined takes into account the voltage drop along the measuring section, the voltage drop along the reference conductor and the reference current.

[0010] This allows the resistance of the reference conductor to change with that of the measurement section. This allows the relationship between the reference current and the voltage drop across the reference conductor to be included in the calculation of the current to be measured, allowing the current to be determined in a simple and independent manner. Temperature measurement is then no longer necessary.

[0011] Resistance refers to electrical resistance unless explicitly stated otherwise.

[0012] It is preferably provided that the measuring section has an outer surface and the reference conductor is arranged on the outer surface and that the reference conductor preferably covers at least one eighth of the outer surface. Covering means that the reference conductor covers a certain proportion of the outer surface, for example at least one eighth. In other words, the reference conductor lies against at least the proportion of the outer surface. The contact area between the reference conductor and the outer surface is therefore at least the proportion, i.e. at least one eighth. Accordingly, it is also advantageous if the reference conductor is arranged on the outer surface of the measuring section and preferably covers at least one eighth of the outer surface of the measuring section.

[0013] The term outer surface refers to the outward-facing outer areas of the measuring section, i.e. its outer surface without the connecting surfaces with the entrance and exit areas.

[0014] Preferably, the reference conductor covers at least a quarter, particularly preferably at least a third.

[0015] The reference conductor is preferably thermally coupled to the measuring section. This means that the reference conductor is arranged on the measuring section such that it has essentially the same temperature as the measuring section. The reference conductor preferably has a length that corresponds to at least five times, particularly preferably at least seven times, and most particularly preferably at least ten times the length of the measuring section. Length refers to the length along which the current flows through the reference conductor or the measuring section.

[0016] In a preferred embodiment, the reference conductor is designed as at least one cable line and is routed along its longitudinal extent along the outer surface. A cable line extends along its longitudinal extent, along which current usually flows. It typically has a substantially constant cross-section, preferably round or flat. A cable line can ensure that the contact surface extends along the longitudinal extent, thus achieving particularly good thermal coupling.

[0017] In order to be able to attach a particularly long length of reference conductor to the outer surface, it can be provided that the reference conductor is arranged at least partially in a meandering, spiral and / or helical shape on the outer surface. In this way, the outer surface and different regions of the outer surface can be covered as evenly as possible. It can also be provided that the reference conductor has a cross-section that is adapted to the shape of the region of the outer surface on which it is arranged. If, for example, the outer surface is cuboid-shaped and has an upper side on which the reference conductor is arranged, the reference conductor can have substantially the same width as the upper side and extend along the length of the upper side. In this way, the majority of the upper side is covered by the reference conductor.

[0018] To achieve a particularly simple calculation of the current to be determined, the reference conductor can be provided with the same resistivity, preferably the same material, as the measuring section. By using the same material, the current to be determined can be calculated independently of the resistances. This can also be achieved if the material of the reference conductor has essentially the same temperature dependence as the material of the measuring section.

[0019] To enable simple determination, the reference conductor can be configured to be supplied with and / or flowed through by a constant current. Thus, the current is already known, and only the voltage needs to be measured. For example, the reference conductor can be configured to be connected to a constant current source. The same applies if the reference conductor is configured to be supplied with a constant current. Alternatively, the reference conductor can also be configured to be supplied with a constant voltage. Thus, only the current needs to be measured.

[0020] The invention also relates to a current measuring device with a shunt for the current to be determined to flow through. According to the invention, the shunt is designed according to the invention, wherein the current measuring device has a first voltmeter for measuring the voltage drop along the measuring section, which is electrically connected to measuring points of the shunt, wherein the current measuring device has a, preferably constant, current source, which is electrically connected to the reference conductor for supplying the reference conductor, and wherein the current measuring device has at least a second voltmeter for measuring the voltage drop along the reference conductor and / or at least one ammeter for measuring the current flowing through the reference conductor. In this way, all measured values ​​required to calculate the current to be determined can be determined in a simple manner.

[0021] The second voltmeter is preferably electrically connected to both ends of the reference wire and connected in parallel to measure the voltage. Similarly, the ammeter is electrically connected in series with the reference wire.

[0022] To directly determine the current to be measured, the current measuring device can be provided with an evaluation unit for calculating the current flowing through the shunt, and the evaluation unit can be connected to the first voltmeter, as well as to the second voltmeter and / or the ammeter to receive their measurement signals. Of course, the connection between the evaluation unit and the second voltmeter is only possible if one is available. The same applies to the connection between the evaluation unit and the ammeter.

[0023] It is particularly advantageous if the current is calculated based on the following formula:

[0024] IsH= y * Iref * USH / Uref where ISH is the current to be determined, I re f is the reference current, U re f is the voltage drop along the reference conductor and y is the resistance ratio between the electrical resistance of the reference conductor and the electrical resistance of the measuring section (R re f / RsH where R re f is the resistance of the reference conductor and RSH is the resistance of the measuring section. This can be achieved in particular if the resistances of the reference conductor and the measuring section change essentially the same. In this case, y represents a constant that is not temperature-dependent.

[0025] If the reference current is constant and known, it does not necessarily need to be measured, but it can be provided for measurement anyway, or an ammeter can be included. This increases the accuracy of the calculation. Accordingly, the voltage drop across the reference conductor does not necessarily need to be measured if a constant and known voltage is applied to the reference conductor. However, it can be provided for measurement anyway, or a second voltmeter can be included.

[0026] The invention will be explained in more detail below with reference to the non-limiting embodiment shown in the figure. The figure shows an embodiment of a current measuring device according to the invention with a shunt according to the invention, which implements the method according to the invention.

[0027] The current measuring device shown comprises a shunt 1, which has an input section 2, an output section 4 and a measuring section 3 arranged between them. The majority of the input section is designed as an input contact 2a and the majority of the output section 4 as an output contact 4a. Holes allow a connection to the current-carrying terminals, which supply the shunt 1 with the current I to be determined. SH take care of.

[0028] The measuring section 3 has a substantially rectangular shape, being connected at both ends to the input region 2 or the output region 4. Thus, its outer surface is essentially formed by a top side, a bottom side, and two thin edges.

[0029] A measuring point 6 is arranged in the area of ​​the connection between measuring section 3 and input area 2, and a measuring point 6 is also arranged in the area of ​​the connection between measuring section 3 and output area 4.

[0030] The measuring points 6 are electrically connected to a first voltmeter 10, which is shown only schematically.

[0031] A reference conductor 5 in the form of a cable is arranged on the upper side of the measuring section 3, essentially covering the entire upper side in a meandering shape. The majority of its longitudinal extension thus extends along the length of the measuring section 3 between the input area 2 and the output area 4.

[0032] The reference conductor 5 is supplied with a constant current of known magnitude by a constant current source 11. A second voltmeter 12 is connected in parallel to the reference conductor 5, which can be used to measure the voltage drop across the reference conductor 5.

[0033] The first voltmeter 10, the second voltmeter 12, and the current source 11 are connected to an evaluation unit 13. This can be achieved via data lines, radio, or other connection types. The evaluation unit 13 receives the measured values ​​and preferably also the current from the current source 11 and preferably controls the voltmeters 10, 12, and the current source 11. This allows the evaluation unit 13 to calculate the current to be determined.

Claims

PATENT CLAIMS 1. Shunt (1) for measuring electrical current, wherein the shunt (1) has an input region (2) with at least one input contact (2a) and the shunt (1) has an output region (4) with at least one output contact (4a), wherein the shunt has at least one measuring section (3) which is electrically connected between the input region (2) and the output region (4), characterized in that at least one electrically conductive reference conductor (5) is arranged in or on the measuring section (3) and is electrically insulated from the measuring section (3).

2. Shunt (1) according to claim 1, characterized in that the reference conductor (5) is thermally coupled to the measuring section (3).

3. Shunt (1) according to claim 1 or 2, characterized in that the measuring section (3) has an outer surface and the reference conductor (5) is arranged on the outer surface and that preferably the reference conductor (5) covers at least one eighth of the outer surface.

4. Shunt (1) according to one of claims 1 to 3, characterized in that the reference conductor (5) is designed as at least one cable line and is preferably guided along its longitudinal extent along the outer surface.

5. Shunt (1) according to one of claims 1 to 4, characterized in that the reference conductor (5) is arranged at least partially in meander shape, spiral shape and / or snail shape.

6. Shunt (1) according to one of claims 1 to 5, characterized in that the reference conductor (5) has the same specific resistance, preferably the same material, as the measuring section (3).

7. Shunt (1) according to one of claims 1 to 6, characterized in that the reference conductor (5) is designed to be supplied with a constant current.

8. Current measuring device with a shunt (1) for the flow of the current to be determined, wherein the shunt (1) is designed according to one of the preceding claims, wherein the current measuring device has a first voltmeter (10) for measuring the voltage drop along the measuring section (3), which is electrically connected to measuring points (6) of the shunt (1), wherein the current measuring device has a, preferably constant, current source (11) which is electrically connected to the reference conductor (5) for supplying the reference conductor (5), and wherein the current measuring device has at least a second voltmeter (12) for measuring the voltage drop along the reference conductor (5) and / or at least one ammeter for measuring the current flowing through the reference conductor (5).

9. Current measuring device according to claim 8, characterized in that the current measuring device has an evaluation unit (13) for calculating the current flowing through the shunt (1), and that the evaluation unit (13) is connected to the first voltmeter (10), as well as to the second voltmeter (12) and / or the ammeter for receiving their measurement signals.

10. Method for measuring electrical current with a shunt (1) through which the current to be determined flows, wherein the current is guided through a measuring section (3) of the shunt (1) and the voltage drop along the measuring section (3) is measured, a reference conductor (5) arranged in or on the measuring section (3), which is electrically insulated from the measuring section (3), has a reference current flowing through it and the current intensity of the reference current is measured and wherein the calculation of the current to be determined takes into account the voltage drop along the measuring section (3) and the reference current.

11. Method according to claim 10, characterized in that the reference conductor (5) is thermally coupled to the measuring section (3).

12. Method according to claim 10 or 11, characterized in that the reference conductor (5) is supplied with a constant current.

13. Method according to claim 8 or 9, characterized in that the reference conductor (5) is arranged on the outer surface of the measuring section (3) and preferably covers at least one eighth of the outer surface of the measuring section (3).

14. Method according to one of claims 10 to 13, characterized in that the calculation of the current is based on the following formula: IsH= y * Iref * USH / Uref where ISH is the current to be determined (ISH), Iref is the reference current, Uref is the voltage drop along the reference conductor (5) and y is the resistance ratio between the electrical resistance of the reference conductor (5) and the electrical resistance of the measuring section (3).

15. Method according to one of claims 10 to 14, characterized in that the method is carried out using a shunt (1) according to one of claims 1 to 7 and / or using a current measuring device according to claim 8 or 9.

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