Shunt with conductor and cooling device

Abstract

The invention relates to a shunt for measuring an electric current. The shunt has a conductor (1) with at least one input contact (3a) and at least one output contact (3b), wherein the conductor (1) has at least one measuring section (6), and at least one cooling device (5) is arranged on the conductor (1) in order to cool the conductor (1). The invention is characterized in that the conductor (1) extends along a longitudinal axis (A) along which a current substantially flows, the conductor (1) has two longitudinal segments (2a, 2b) which likewise extend along the longitudinal axis (A) and which are arranged at the same height along the longitudinal axis (A), each of the longitudinal segments (2a, 2b) has a contact point for introducing or discharging the current to be measured at a first end (4a) along the longitudinal axis (A), and the longitudinal segments (2a, 2b) are electrically connected together at a second end (4b) along the longitudinal axis (A).

Description

[0001] Shunt with current conductor and cooling device

[0002] The invention relates to a shunt for measuring electrical current, wherein the shunt has a current conductor for conducting the current to be measured with at least one input contact and at least one output contact, wherein the current conductor has at least one measuring section and wherein at least one cooling device for cooling the current conductor is arranged on the current conductor.

[0003] It also relates to a method for measuring an electric current using a shunt and to a current measuring device using a shunt.

[0004] A shunt, also called a shunt resistor or current measuring resistor, is an electrical component used for measuring electrical currents, especially larger currents such as those in the range of over 100 amperes. 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.

[0005] Such shunts suffer from the thermal stress caused by the high current, which, on the one hand, represents physical stress and, on the other hand, impairs the measurement results, as the temperature also changes the resistance of the measuring path. Therefore, many shunts are often only suitable for short periods of time, for example, less than two minutes. Furthermore, due to the high current, shunts generate strong electromagnetic fields that can interfere with other components.

[0006] US Pat. No. 6,498,499 B1 discloses a measuring device for measuring the capacitance of electrical conductors. A water bath cooling device is used for two consecutively arranged measuring sections. The measuring sections are located at different heights of the channel. However, the current is not measured. Such an arrangement is also unsuitable for measuring high currents and suffers from the problems mentioned above.

[0007] The object of the invention is to provide a shunt, a current measuring device and a method as mentioned above, which has a longer operating time with the lowest possible electromagnetic interference in its environment.

[0008] This object is achieved according to the invention in that the current conductor extends along a longitudinal axis along which current is essentially conducted, in that the current conductor has two length segments which also extend along the longitudinal axis and are arranged at the same height along the longitudinal axis, in that at a first end along the longitudinal axis the length segments each have the input contact or the output contact and in that the length segments are electrically connected to one another at a second end along the longitudinal axis.

[0009] It is also solved by the fact that the procedure has the following steps:

[0010] Providing at least one shunt according to the invention or one current measuring device according to the invention;

[0011] Conducting the current to be determined through a first length segment of the current conductor of the shunt along a longitudinal axis and through a second length segment of the current conductor of the shunt along the longitudinal axis in the opposite direction and at the same height along the longitudinal axis as the first length segment;

[0012] Calculation of the current to be determined taking into account the voltage drop along the measuring section and the resistance of the measuring section.

[0013] The process steps can sometimes be performed simultaneously or in a different order. Steps can also be performed in between, before, or after.

[0014] The electrical resistance of the test section is usually known very precisely. Thus, using Ohm's law, the current flowing can be determined by measuring the voltage drop along the test section. The current to be determined can be calculated using the formula I = U / R, where I is the current to be determined, U is the measured voltage drop, and R is the electrical resistance of the test section.

[0015] By arranging the length segments at the same height, the electromagnetic radiation generated by the two length segments is at least partially canceled out. This results in a significant reduction in electromagnetic radiation and thus less disturbance to the environment. Furthermore, the arrangement of the cooling device results in a significantly lower thermal load. Both of these effects mean that the shunt can be operated for longer periods or even continuously, even at high currents. The measuring section extends along at least part of the current conductor, preferably along part of the current conductor, but it can also encompass the entire current conductor.

[0016] The current conductor is a part of the shunt along which the current to be measured is conducted. It is usually limited along the current flow by the input and output contacts and forms the measuring section. The measuring section can also extend over the entire length of the current conductor.

[0017] In this document, resistance refers to electrical resistance unless explicitly stated otherwise.

[0018] The measuring section has a defined resistance so that the exact amount of current can be determined using the voltage drop between the measuring points.

[0019] By arranged at the same height, we mean that the longitudinal segments at least partially overlap each other along the longitudinal axis, i.e. are arranged at least partially one above the other.

[0020] The longitudinal segments preferably extend essentially in the same direction along their longitudinal extent and are arranged at the same height. The longitudinal extent is the extent along which the current flows. It is harmless if the longitudinal extents are at small angles to one another or if the longitudinal segments have irregularities such as waves at an angle to the longitudinal axis. It is essential that the main direction, i.e., the longitudinal extent, of the two longitudinal segments is essentially the same, which results in at least partial mutual cancellation of the electromagnetic radiation.

[0021] Preferably, the current flows through each of the length segments along their length. The arrangement as described above ensures that the current flows through one length segment in the opposite direction to that flowing through the other length segment.

[0022] The longitudinal segments can consist of two different pieces or can be made of one piece. The longitudinal segments can also be electrically connected to each other at one end via a connecting unit. At least one longitudinal segment is preferably connected to the cooling device along at least most of its longitudinal extent, particularly preferably along substantially its entire longitudinal extent. This allows for good heat transfer.

[0023] Preferably, the measuring section is part of a length segment and the cooling device is arranged on another length segment.

[0024] The longitudinal segments are electrically connected to each other at one end. By electrically connecting the two ends of the longitudinal segments, the current can flow through the longitudinal segments in opposite directions.

[0025] One contact point can represent the input contact and / or another contact point can represent the output contact of the shunt. In this sense, it is preferably provided that the input contact and / or the output contact are arranged at the ends of the longitudinal segments that are not electrically connected to each other.

[0026] Preferably, the longitudinal segments have substantially the same longitudinal extent. Thus, the unconnected ends are located at approximately the same height along the cooling channel. The cooling channel preferably extends parallel to the longitudinal axis.

[0027] Furthermore, it can be provided that the longitudinal segments lie adjacent to one another along their longitudinal extent and are preferably separated from one another exclusively by an electrical insulator. This results in a compact embodiment that enables good heat transfer between the longitudinal segments. The insulator preferably comprises an insulating layer arranged between the longitudinal segments.

[0028] It is also advantageous if the measuring section is designed as part of at least one of the length segments. This allows for particularly good cooling of the measuring section. It can also be provided that the measuring section extends over more than one length segment.

[0029] It is particularly advantageous if the length segments are at least partially designed as tubes arranged essentially coaxially, and if the measuring section is preferably located on the outer length segment. This achieves particularly good attenuation of the electromagnetic radiation. Arranging the measuring section on the outer length segment facilitates access to the measuring points. It can also be provided that the measuring section is located on the inner length segment. This results in better cooling of the measuring section.

[0030] Furthermore, an unwanted discharge of the current is prevented if it is provided that the cooling device is electrically insulated from the length segment on which it is arranged and / or that the cooling channel is electrically insulated from the coolant.

[0031] In order to achieve a measurement with as little loss as possible, the measuring section can be designed to have a greater resistance than the rest of the current conductor.

[0032] The measuring section may be made of a different material than the rest of the current conductor. The rest of the current conductor may have a lower resistance than the measuring section.

[0033] Furthermore, it is advantageous if the cooling device comprises a cooling channel which extends along at least one of the longitudinal segments and if the cooling channel is preferably electrically insulated from the coolant. The cooling channel is a channel through which coolant flows. In this case, the cooling channel can have a supporting shell, for example in the form of a tube, which is connected to the longitudinal segment. It can also be provided that the cooling channel itself has no supporting function and that the supporting function is at least partially taken over by the longitudinal segment. For example, the longitudinal segment can be designed as a tube and the cooling channel is formed by an inner side of the longitudinal segment. In this way, coolant can flow through the cooling channel and the most direct cooling possible can be achieved.

[0034] Preferably, the cooling channel is guided in one of the two tubes.

[0035] Furthermore, at least one measuring point can be arranged at each end of the measuring section. This allows the voltage drop along the measuring section to be accurately determined, for example, by connecting a voltmeter to the measuring points.

[0036] The cooling device serves to cool the shunt. This is important to prevent the temperature from fluctuating too greatly, which would result in changes in resistance. For this purpose, the cooling device can be designed or configured to dissipate heat from at least one length segment. For example, the cooling device can be arranged at least partially on at least one length segment. The cooling device can comprise a passive cooling device, for example at least one heat sink such as cooling fins. Finally, the cooling device can be an active cooling device. With an active cooling device, preferably a fan or a pump, the heat energy is transported away from the component to be cooled. An active cooling device is superior in terms of performance to a passive cooling device based on natural convection and can regulate a target temperature more precisely.This makes it possible to use the shunt in a wide range of outside temperatures without reducing its measurement accuracy.

[0037] Furthermore, it can be provided that the length segments are arranged one inside the other, preferably essentially concentrically. It can also be provided that the cooling device, preferably the cooling channel, is arranged inside both length segments. This results in a particularly compact design with particularly efficient cooling. "One inside the other" means that one length segment at least partially encompasses or covers another length segment.

[0038] The invention also relates to a current measuring device with a shunt for the current to be determined to flow through, wherein the shunt is designed according to the invention, and wherein the current measuring device has a voltmeter for measuring the voltage drop along the measuring path, which is electrically connected to measuring points of the shunt. The current measuring device has an evaluation unit for calculating the current flowing through the shunt, and the evaluation unit is connected to the voltmeter. This connection between the voltmeter and the evaluation unit is designed to transmit measurement data from the voltmeter to the evaluation unit.

[0039] The invention will now be explained in more detail with reference to a non-limiting embodiment shown in the figure. The figure shows a schematic longitudinal section of an embodiment of a shunt according to the invention as part of a current measuring device according to the invention.

[0040] The embodiment of a shunt according to the invention shown in the figure has a current conductor 1, which essentially consists of two longitudinal segments 2a and 2b. A first longitudinal segment 2a has an input contact 3a at a first end 4a, via which the current to be measured is introduced. It extends, like a second longitudinal segment 2b, along a longitudinal axis A. Along the longitudinal extent 10a along the longitudinal axis A, the current then flows through the first longitudinal segment to the second end 4b of the first longitudinal segment 2a, where it is electrically connected to one end of the second longitudinal segment 2b. The first longitudinal segment 2a rests along its entire longitudinal extent 10a against a cooling device 5, which has a cooling tube 5a and an insulating layer 5b. The cooling tube 5a forms a cooling channel 5c in its interior. Coolant flows through the cooling channel 5c during operation.

[0041] The longitudinal extension 10a of the first length segment 2a extends along the flow direction of the cooling channel 5c.

[0042] The second longitudinal segment 2b extends from the first end 4a along the first longitudinal segment 2a to its second end 4b, which is opposite the first end 4a. Thus, the longitudinal segments 2a, 2b are arranged at the same height of the cooling channel 5c and at the same height along the longitudinal axis A. The second longitudinal segment 2b also ends at the level of the input contact 3a, and has an output contact 3b there. The longitudinal segments 2a, 2b are arranged one above the other, separated by a thermally conductive insulator 7. The insulator is preferably designed as an insulating layer. This can be made of air, plastic, or another material, for example.

[0043] The second length segment 2b has a measuring section 6 in a central area, which has a defined resistance. At both ends, the measuring section has measuring points 6a, 6b. By measuring the voltage drop between these points, the current can be easily determined, provided the defined resistance is known.

[0044] In addition to the shunt, the current measuring device also includes a voltmeter 14, which is electrically connected to the measuring points 6a, 6b. The voltmeter 14 is further connected to an evaluation unit 13 and configured to transmit data concerning the measured voltage drop to the evaluation unit 13. This can be achieved via data lines, radio, or other connection types. The evaluation unit 13 can calculate the current to be determined based on this data.

Claims

P A T E N T A N S P R Ü C H E 1. A shunt for measuring electrical current, wherein the shunt comprises a current conductor (1) for conducting the current to be measured, having at least one input contact (3a) and at least one output contact (3b), wherein the current conductor (1) has at least one measuring section (6), and wherein at least one cooling device (5) for cooling the current conductor (1) is arranged on the current conductor (1), characterized in that the current conductor (1) extends along a longitudinal axis (A), along which current is essentially conducted, that the current conductor (1) has two longitudinal segments (2a, 2b) which also extend along the longitudinal axis (A) and are arranged at the same height along the longitudinal axis (A), that at a first end (4a) along the longitudinal axis (A), the longitudinal segments (2a, 2b) each have the input contact (3a) or the output contact (3b), and that the longitudinal segments (2a,2b) are electrically connected to one another at a second end (4b) along the longitudinal axis (A).

2. Shunt according to claim 1, characterized in that the length segments (2a, 2b) have substantially the same longitudinal extent (10a, 10b) along the longitudinal axis (A).

3. Shunt according to claim 1 or 2, characterized in that the length segments (2a, 2b) lie against one another along their longitudinal extent (10a, 10b) along the longitudinal axis (A) and are preferably separated from one another exclusively by an electrical insulator (7).

4. Shunt according to one of claims 1 to 3, characterized in that the measuring section (6) is designed as part of at least one of the length segments (2a, 2b).

5. Shunt according to one of claims 1 to 4, characterized in that the length segments (2a, 2b) are at least partially designed as tubes (5a) which are arranged substantially coaxially and that preferably the measuring section (6) is arranged on the outer length segment (2a, 2b).

6. Shunt according to one of claims 1 to 5, characterized in that the cooling device (5) is electrically insulated from the length segment (2a, 2b) on which it is arranged.

7. Shunt according to one of claims 1 to 6, characterized in that the measuring section (6) has a greater resistance than the remaining current conductor (1).

8. Shunt according to one of claims 1 to 7, characterized in that the cooling device (5) comprises a cooling channel (5c) which extends along at least one of the length segments (2a, 2b) and that preferably the cooling channel (5c) is electrically insulated from the coolant.

9. Shunt according to claim 8 in combination with claim 5, characterized in that the cooling channel (5c) is guided in one of the two tubes (5a).

10. Shunt according to one of claims 1 to 9, characterized in that at least one measuring point (6a, 6b) is arranged at each end of the measuring section.

11. Shunt according to one of claims 1 to 10, characterized in that the cooling device (5) is an active cooling device.

12. Current measuring device with a shunt for the current to be determined to flow through, wherein the shunt is designed according to one of the preceding claims, and wherein the current measuring device has a voltmeter (14) for measuring the voltage drop along the measuring section (6), which is electrically connected to measuring points (6a, 6b) of the shunt and 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 voltmeter (14).

13. A method for measuring an electric current with a shunt, comprising the following steps: Providing at least one shunt according to one of claims 1 to 11 or a current measuring device according to claim 12; Conducting the current to be determined through a first length segment (2a) of the current conductor (1) of the shunt along a longitudinal axis (A) and through a second length segment (2b) of the current conductor (1) of the shunt along the longitudinal axis (A) in the opposite direction and at the same height along the longitudinal axis (A) as the first longitudinal segment (2a); Calculation of the current to be determined taking into account the voltage drop along the measuring section (3) and the resistance of the measuring section (2). 2024 06 28 MT

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