阅读说明：本技术 同轴电阻器 (Coaxial resistor ) 是由 U·黑茨勒 于 2018-06-22 设计创作，主要内容包括：本发明涉及一种同轴电阻器(1),其具有用于沿相反的方向传导待测量的电流的向前导体(6)和返回导体(7),并且具有由电阻材料制成的电阻器元件,所述电阻器元件布置在向前导体(6)或返回导体(7)中,使得电流流过电阻器元件。本发明提出,相对于电流流动方向,至少内部的返回导体(7)的横截面是矩形的,这简化了同轴电阻器(1)的制造。由于该设计,消除了由热电电压、电阻器元件的TC和不均匀的电流分布引起的误差。(The invention relates to a coaxial resistor (1) having a forward conductor (6) and a return conductor (7) for conducting a current to be measured in opposite directions, and having a resistor element made of a resistive material, which is arranged in the forward conductor (6) or the return conductor (7) such that the current flows through the resistor element. The invention proposes that at least the inner return conductor (7) is rectangular in cross section with respect to the current flow direction, which simplifies the manufacture of the coaxial resistor (1). Due to this design errors caused by the thermoelectric voltage, the TC of the resistor element and the uneven current distribution are eliminated.)

1. A coaxial resistor (1) for measuring a current (I), the coaxial resistor comprising:

a) a forward conductor (6) for conducting a current (I) to be measured,

b) a return conductor (7) for conducting the current (I) to be measured located inside the forward conductor (6), the forward conductor (6) and the return conductor (7) being coaxially arranged and electrically connected in series and conducting the current (I) in opposite current flow directions, and

c) a resistor element (14) made of a resistive material, the resistor element (14) being arranged in the forward conductor (6) or the return conductor (7) such that a current (I) flows through the resistor element (14),

it is characterized in that the preparation method is characterized in that,

d) the cross section of at least the inner return conductor (7) in a sectional plane perpendicular to the current flow direction is angular, in particular rectangular, in particular square, triangular, pentagonal or polygonal.

2. Coaxial resistor (1) according to claim 1,

a) the inner return conductor (7) is formed by a plurality of flat, preferably rectangular plates, and/or

b) The outer forward conductor (6) is formed by a plurality of flat, preferably rectangular plates, and/or

c) Wherein the plates of the forward conductor (6) and the plates of the return conductor (7) are arranged in respective pairs parallel to each other.

3. Coaxial resistor (1) according to claim 1, characterized in that the outer forward conductor (6) has a rounded cross section, in particular a circular cross section.

4. Coaxial resistor (1) according to claim 2 or 3,

a) the plate of the forward conductor (6) or the plate of the return conductor (7) accommodates a resistor element (14), and/or

b) The resistor element (14) is accommodated in an insert (11) embedded in the front conductor (6) or the return conductor (7), respectively, and bridges a gap (10) in the front conductor (6) or the return conductor (7) extending transversely to the current flow direction, and/or

c) The inserts (11) each consist of a composite plate comprising two plate-shaped conductor elements (12, 13) made of a conductor material and a plate-shaped resistor element (14) located between the plate-shaped conductor elements in the direction of current flow.

5. Coaxial resistor (1) according to one of the preceding claims,

a) a first connection portion (2) made of a conductor material for supplying an electric current (I) to the coaxial resistor (1),

b) a second connection portion (3) made of a conductor material for the outflow of an electric current (I) from the coaxial resistor (1),

c) the forward conductor (6) and the return conductor (7) are each electrically and mechanically connected to one of the two connection portions (2, 3).

6. Coaxial resistor (1) according to claim 5,

a) the electrical connection between the forward conductor (6) and the return conductor (7) and the connection parts (2, 3) is a soldered connection, in particular a brazed connection (8a, 8b) or a welded connection, and/or

b) The electrical connection between the forward conductor (6) and the return conductor (7) is a brazed connection (9) or a welded connection.

7. Coaxial resistor (1) according to claim 5 or 6,

a) the two connecting parts (2, 3) are formed by flat, preferably rectangular plates, and/or

b) The two connection parts (2, 3) in the form of plates are oriented at right angles to the plates of the forward conductor (6) and the return conductor (7).

8. Coaxial resistor (1) according to one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

a) at least one pair of voltage taps (18, 19, 20) is provided for measuring a voltage drop across the resistor element (14), respectively, and/or

b) Provided with a plurality of pairs of voltage taps (18, 19, 20), which pairs of voltage taps (18, 19, 20) are arranged at different voltage measurement points, and/or

c) The voltage tap (18, 19, 20) has at least two contacts (18, 19) on the voltage side or ground side as a double tap in order to achieve efficient heat transfer to the printed circuit board (15) and/or

d) The voltage taps (18, 19, 20) are connected to the conductor elements (12, 13) of the composite sheet of the insert (11) by means of:

d1) a soldered connection, in particular a brazed connection,

d2) welded connections, or

d3) A sintered compound.

9. Coaxial resistor (1) according to claim 8,

a) the voltage taps (18, 19, 20) being composed of copper, or

b) The ground-side voltage tap (20) consists of the same composite material as the composite material plate of the insert (11), in particular of the same batch of composite material as the composite material of the insert (11).

10. Coaxial resistor (1) according to claim 9,

a) provided with a punch-out part (16) for forming a voltage-side voltage tap (18, 19), which punch-out part is connected to the voltage-side plate-shaped conductor element (12) of the insert (11), and

b) a stamped part (17) of the plate-shaped conductor element (13) connected to the insert (11) on the ground side is provided in order to form a voltage tap (20) on the ground side.

11. Coaxial resistor (1) according to claim 10,

a) the punch elements (16, 17) have contact lugs (18-20) for electrical connection to the printed circuit board (15) and/or

b) In at least one pair of the voltage taps (18-20), the ground-side contact lug (20) is arranged centrally between the two voltage-side contact lugs (18, 19).

12. Coaxial resistor (1) according to claim 10 or 11,

a) the punch members (16, 17) are connected to the plate-shaped conductor elements (12, 13) of the insert (11) by one of the following connections:

a1) the sintering and the connection are carried out,

a2) a soldered connection, in particular a brazed connection,

a3) welded connection, and/or

b) The sintered connection is formed by means of a silver sintering paste; and/or

c) The sintered joint comprises a sintered layer with a layer thickness of 30 μm to 70 μm.

13. The coaxial resistor (1) according to any one of claims 10-12,

a) the thickness of the stamped parts (16, 17) is greater than 0.1mm, 0.2mm or 0.25mm and/or less than 2mm, 1mm, 0.5mm, 0.4mm or 0.35mm, and/or

b) The composite material plates of one of the punch parts (16, 17) and the insert (11) consist of the same composite material, in particular of the same batch of composite material strips.

14. Coaxial resistor (1) according to one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

a) a measuring circuit is arranged between the forward conductor (6) and the return conductor (7) on the inside, said measuring circuit detecting the voltage dropping on the resistor element (14), and/or

b) The measuring circuit is arranged on a printed circuit board (15), and/or

c) The printed circuit board (15) is connected to contact lugs (18-20) of the punch elements (16, 17) and/or

d) The printed circuit board (15) is arranged transversely, in particular at right angles, to the direction of current flow in the forward conductor (6) and the return conductor (7) and/or

e) The printed circuit board (15) has terminals (21, 22, 23) on at least one lateral edge for connecting to the voltage taps (18, 19, 20) and/or

f) The printed circuit board (15) has terminals (21, 22, 23) on all lateral end edges for connection to voltage taps (18, 19, 20) of the parallel insert (11).

15. Coaxial resistor (1) according to claim 14,

a) a first printed circuit board surface, in particular the upper side, of the printed circuit board (15) accommodates balancing resistors (R)_SYMRa, Rb), the balancing resistor (R)_SYMRa, Rb) are assigned to each pair of voltage taps (18, 19, 20) in order to weight the individual voltage measured values and/or

b) The first printed circuit board surface accommodates a resistor (R) for compensating for temperature dependence of the resistor element_komp) And/or

c) The second printed circuit board surface accommodates a resistor (R) made of copper serving as a temperature sensor for compensating for the temperature dependence of the resistor element (14)_CU1、R_CU2) And/or

d) Resistor (R) for temperature compensation made of copper_CU1、R_CU2) By two resistors (R) connected in parallel_Cu1、R_Cu2) Forming an average of the two measured voltages from the double tap, and/or

e) The third and fourth printed circuit boards, in particular the bottom side, of the printed circuit board (15) have a resistor (R) for copper_Cu1、R_Cu2) A copper connection surface in the region that is thermally compensated.

16. Coaxial resistor (1) according to one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

a) the coaxial resistor (1) has a continuous current carrying capacity of at least 1kA, 2kA, 3kA, 4kA or 5kA, and/or

b) The conductor material is copper or copper alloy or aluminum alloy; and/or

c) The conductive material has a higher electrical conductivity than the resistive material; and/or

d) The resistive material is a copper-manganese alloy, in particular a copper-manganese-nickel alloy, or a nickel-chromium alloy, and/or

e) The resistivity of the resistive material of the resistor element (14) is:

e1) less than 50.10^-7Ωm、20·10^-7Ωm、10·10^-7Omega m or 5.10^-7Omega m, and/or

e2) Greater than 1.10^-8Ωm、5·10^-8Ωm、1·10^-7Omega m or 2.10^-7Omega m; and/or

f) The resistance value of the coaxial resistor (1) is

f1) At least 0.1 μ Ω, 0.5 μ Ω, 1 μ Ω, 2 μ Ω, 5 μ Ω, 10 μ Ω, 20 μ Ω, and/or

f2) A maximum of 1000 μ Ω, 500 μ Ω, 250 μ Ω, 100 μ Ω or 50 μ Ω; and/or

g) The temperature coefficient of the resistance value of the coaxial resistor (1) is less than 500ppm/K, 200ppm/K or 50 ppm/K.

Technical Field

The invention relates to a coaxial resistor for measuring current.

Background

Such a coaxial resistor is known from WO 2007/068409 a1(DE 102005059561 a1) and is shown in fig. 6. The current to be measured is supplied via a tubular conductor and then flows back in the opposite direction through a return conductor, which is also tubular and arranged coaxially with the conductor. The advantage of this current flow in opposite directions is that the magnetic fields generated by the currents largely cancel each other in certain regions on the inside. The cross-section of the forward and return conductors is circular here, but is associated with relatively high manufacturing costs in the case of very low resistance values of only a few micro-ohms, mainly due to the difficulty in arranging the voltage connections and the associated additional sources of error.

For the technical background of the present invention reference is made to DE 102014011593B 4.

Disclosure of Invention

The invention is therefore based on the task of providing a correspondingly improved coaxial resistor.

This object is solved by a coaxial resistor according to the invention according to claim 1.

The invention proposes that the coaxial resistor has an angular cross section at least in the case of the inner return conductor, which greatly simplifies production, since the return conductor can be composed of an angular plate here.

As with the known coaxial resistors, the coaxial resistor according to the invention firstly has a forward conductor and a return conductor for conducting the current to be measured, wherein the forward conductor and the return conductor are arranged coaxially and are electrically connected in series such that the current flows in the forward conductor and the reverse conductor in opposite current flow directions. This current flow in the opposite direction is advantageous-as already mentioned at the outset with regard to the prior art-because the magnetic fields generated by the currents in the forward and reverse conductors cancel out to a large extent in the region of the actual resistor element (see below).

In addition, like the known coaxial resistor, the coaxial resistor according to the invention comprises a resistor element made of a resistive material (e.g. a copper-manganese-nickel alloy), wherein the resistor element is arranged in the forward conductor or the return conductor such that a current flows through the resistor element. According to ohm's law, the voltage drop across the resistor element is proportional to the current and is therefore a measure of the current to be measured. This enables current measurement according to the four-wire technique, which is also known, for example, from EP 0605800 a 1.

The coaxial resistor according to the invention now differs from the above-described known coaxial resistor in that at least the inner return conductor is angular, in particular rectangular, in cross section in a sectional plane at right angles to the current flow direction. In a preferred embodiment of the invention the cross-section of the return conductor is square, but the cross-section may also have other rectangular shapes. In addition, the invention also provides the possibility that the cross-section of the return conductor may be triangular, pentagonal or generally polygonal. As briefly mentioned above, the angular cross-section has the following advantages: the return conductor may consist of a plurality of flat plates, which greatly simplifies the production of the coaxial resistor according to the invention.

In the case of a coaxial resistor according to the invention, the return conductor is optionally composed of a plurality of flat, preferably rectangular, plates, which can be assembled to form the forward or return conductor.

In a preferred embodiment of the invention, the forward conductor and the return conductor are each comprised of rectangular plates. Here, it is preferable to make one plate of the forward conductor parallel to one plate of the return conductor. In this embodiment both the return conductor and the forward conductor have an angular cross-section.

Alternatively, however, it is also possible that only the inner return conductor has an angular cross-section, while the outer forward conductor has a rounded cross-section. For example, the outer forward conductor may have a circular cross-section and thus be tubular. In this case, the outer forward conductor is thus conventionally designed as a tube, while the inner return conductor consists of a plurality of plates, in order to simplify the manufacturing process.

The resistor elements described above may be arranged in the outer forward conductor or in the inner return conductor. The only decisive factor is that the current to be measured flows through the resistor element, so that the voltage drop of the resistor element forms a measure of the current to be measured according to ohm's law.

In a preferred embodiment of the invention, however, the resistor element is arranged in the inner return conductor. This is advantageous because the voltage measurement at the resistor element in the field-free space is simplified by the measurement circuit located within the coaxial resistor, as is still described in detail.

In a preferred embodiment of the invention, the two connection parts for current supply and current outflow as well as the forward conductor and the return conductor are made of massive copper plates in order to reduce the power losses that are inevitable in power supply lines at high currents.

In a preferred embodiment of the invention, the resistor element is always arranged in an insert, wherein the insert is embedded in the forward conductor or the return conductor and bridges a gap in the forward conductor or the return conductor which extends transversely to the current flow direction. The current to be measured therefore flows through the insert comprising the resistor element, so that a gap in the front conductor or the return conductor extending transversely to the current flow direction can prevent an undesired shunt connection across the insert.

The inlay with the resistor element is preferably composed of a composite plate with two plate-shaped conductor elements of a conductor material, for example copper, and a plate-shaped resistor element of a resistive material, for example copper manganese nickel alloy, located between the plate-shaped conductor elements in the direction of the current flow. Such composite material plates are known, for example, from EP 0605800 a1 and can be produced inexpensively from composite material strips.

In addition, the coaxial resistor according to the invention preferably comprises a plate-like connection portion made of a conductor material (e.g. copper) for the supply or outflow of the current to be measured, wherein the forward conductor and the return conductor are each connected to one of the two connection portions.

The electrical connection between the forward conductor and the return conductor on the one hand and the connection portion on the other hand may be achieved by means of soldering (e.g. brazing) or welding, for example. In addition, the forward and return conductors and the insert may also be connected to each other by soldering (e.g., brazing) or welding to achieve the desired series connection of the forward and return conductors.

It has already been mentioned briefly above that the two connection portions for current supply and current consumption consist of flat, preferably rectangular plates. In addition, it should be noted that these plate-like connecting portions are preferably oriented at right angles to the forward and return conductors. In addition, it should be noted that the plate-like connection portions for power supply or current outflow are preferably arranged in parallel with each other. The forward conductor and the return conductor may thereby be arranged on the plate-like connection portion.

It has been mentioned above that the voltage drop across the resistor element is a measure for the current to be measured according to ohm's law. Preferably, one voltage tap contacts the voltage side conductor element of the insert and the other voltage tap of the pair contacts the ground side conductor element of the insert.

However, in a preferred embodiment, not only one pair of voltage taps is provided, but a plurality of pairs of voltage taps are spatially distributed. Each pair of voltage taps thus provides a voltage measurement value, so that an average value can be calculated from the voltage measurement values here. In this way, non-uniformities in the current distribution in the coaxial resistor may be accounted for. Basically, this principle of voltage measurement at different points is known from DE 102013005939 a1, so that the content of this patent application can be fully attributed to this description.

The voltage tap can have at least two contacts made of conductor material on the voltage side or ground side (i.e. a double tap) in order to achieve good thermal contact with the printed circuit board. This is advantageous for compensating for undesired thermoelectric voltages.

The connection between the voltage tap on the one hand and the conductor element of the composite plate (inlay) on the other hand can be made, for example, by soldering (e.g. brazing), welding or sintering.

It should also be mentioned that the voltage tap may be made of copper or the same composite material as the composite material of the insert, in particular of the same batch of composite material as the composite material of the insert.

To form a voltage-side tap or a ground-side voltage tap, the invention may comprise a stamped part, which is connected to the voltage-side or ground-side conductor element of the inlay (composite plate).

For electrical connection to the printed circuit board, the punch member may have contact tabs, which may also be bendable. In a preferred embodiment, it is advantageous if, in a pair of voltage taps made of one conductor material, a narrower and possibly thinner contact lug made of a composite material is arranged centrally between two contact lugs of the voltage side on the ground side. This has the advantage that, due to the significantly larger cross section of the contact tabs (double, thicker, wider and more heat conductive), the temperature of the high voltage side (voltage side) can be efficiently transferred to the printed circuit board via good heat conduction, so that the temperature at the soldering connection of the printed circuit board is the same as the temperature at the voltage side soldering connection of the insert. The complete temperature difference of the shunt structure is thus applied to the composite material sheet, so that the temperature-voltage compensation can function correctly.

The stamped part is electrically and mechanically connected to the conductor elements of the inlay (composite plate). This may be, for example, a sintered connection, a brazed connection (e.g., a brazed connection), or a welded connection. For example, in the case of a sintered joint, this can be achieved by means of a silver sintering paste which has been printed and dried in a structured manner on the copper conductor element beforehand. The sintering layer can, for example, consist of pure silver, the thickness of which is between 30 μm and 70 μm, depending on the printing density of the sintering paste.

In a preferred embodiment of the invention the thickness of the punch member is about 0.3mm, but other thicknesses of the punch member are possible within the scope of the invention.

It should also be mentioned here that the at least one (e.g. mass-produced) stamping part and the associated composite plate (insert) preferably consist of the same composite material, in particular the same batch of composite material strips. This is advantageous for compensating the thermoelectric voltage.

It has been briefly mentioned above that the voltage drop across the resistor element is a measure for the current to be measured according to ohm's law. For measuring this voltage drop, a measuring circuit is preferably provided which can be arranged inside the return conductor. The measuring circuit is preferably located on a printed circuit board which is coupled to the contact tabs of the punch member, wherein the printed circuit board is preferably arranged transversely, in particular at right angles, with respect to the direction of current flow in the forward and return conductors. The printed circuit board preferably has terminals (e.g. pads) at its front edge for connection to voltage taps in order to measure the voltage drop across the resistor element. The connection between the voltage tap on the one hand and the printed circuit board on the other hand can be made using the contact tabs of the above-mentioned punch member.

The outer cross section of the printed circuit board is preferably matched to the inner cross section of the inner return conductor, so that the printed circuit board fills the free inner cross section of the inner return conductor until a circumferential gap is formed. The contact tabs of the punch element can bridge the circumferential gap between the printed circuit board and the return conductor and contact the printed circuit board. If the inner return conductor has a square cross-section, the printed circuit board is also preferably square. In the case of a triangular cross-section of the inner return conductor, the printed circuit board is also preferably triangular. It is therefore preferred to assign a front edge of the printed circuit board to each plate of the return conductor, so that the printed circuit board can easily contact all the inserts in the plate of the return conductor.

The printed circuit board preferably has a plurality of printed circuit board surfaces and is thus multilayered. Balancing resistors may be located in the first printed circuit board surface (e.g. on the upper side), wherein the balancing resistors are each assigned a separate pair of voltage taps in order to weight the individual voltage measurements, as is known, for example, from DE 102013005939 a 1.

In addition, the first printed circuit board surface may also accommodate a resistor for compensating for the temperature dependence of the resistor element and/or the temperature sensor.

The second printed circuit board surface accommodates a resistor made of copper which is also used for temperature compensation. This may also consist of, for example, two resistors connected in parallel, which may average the two measured voltages from the double tap. In addition, the circuit board may have third and fourth printed circuit board surfaces. For example, a copper connection surface for thermal compensation can be located in the region of the copper resistor on the underside of the printed circuit board.

Compensation of thermoelectric voltages is known, for example, from DE 102016008415.4, and the content of this earlier patent application is therefore also fully incorporated in the present description.

It should also be mentioned that the coaxial resistor according to the invention preferably has a relatively high continuous current carrying capacity, which may be at least 1kA, 2kA, 3kA, 4kA or even 5 kA.

The preferred conductor material is copper or a copper alloy. Alternatively, the conductor material may also be aluminum or an aluminum alloy.

It should also be mentioned that the conductor material preferably has a higher electrical conductivity than the resistive material.

For example, within the scope of the invention, copper-manganese-nickel alloys, such as Cu82Mn12Ni4 (e.g., Cu-Mn-Ni-O-

) Can be used as a resistive material. Alternatively, nichrome or other resistive alloys may be used as the resistive material.

However, the resistive material of the resistor element preferably has a resistivity in the range of 1 · 10^-8Omega m to 50.10^-7Resistivity in the range of Ω m.

On the other hand, the resistance value of the entire coaxial resistor is preferably in the range of 0.1 μ Ω to 1m Ω.

It should also be mentioned that the resistance value of the coaxial resistor is preferably very constant over temperature with a temperature coefficient of less than 500ppm/K, 200ppm/K or even 50 ppm/K.

Drawings

Further advantageous developments of the invention are given in the dependent claims or are explained in more detail below with the aid of the figures together with the description of preferred embodiments of the invention. The figures show:

figure 1A is a cross-sectional view of a coaxial resistor according to the present invention along section line a-a in figure 1B,

figure 1B is a view of the coaxial resistor according to figure 1A,

fig. 1C shows a part of a coaxial resistor according to the invention, with a connection portion and an attached plate of a return conductor,

figure 1D is a view of a plate-like return conductor with an embedded insert,

figure 1E is a cross-sectional view through the return conductor with an insert shown in figure 1D,

figure 2A is a simplified cross-sectional view through an insert and a printed circuit board with stamped-out components for contacting,

figure 2B is a view of the structure according to figure 2A,

figure 3A is a view of a printed circuit board for a measurement circuit having twelve pairs of voltage taps,

figure 3B is an enlarged detail view of a pair of voltage taps of figure 3A,

figure 4 shows a schematic diagram illustrating the weighting of the voltage measurements for each pair of voltage taps,

FIG. 5 is a simplified circuit diagram illustrating compensation of thermal stress and compensation of TC of the resistor element, an

Fig. 6 is a perspective view of a conventional coaxial resistor according to the prior art.

Detailed Description

The figure shows a coaxial resistor 1 according to the invention for measuring a current I according to the known four-wire technique.

The current I to be measured is introduced into the coaxial resistor 1 via a plate-shaped connection part 2 made of a conductor material, for example copper, and is again led out of the coaxial resistor 1 via a plate-shaped connection part 3 made of the same conductor material.

The two connection parts 2 and 3 each have a hole 4 and 5 for the passage of a screw, so that, for example, the two connection parts 2 and 3 can be screwed together with a current bar.

The current I to be measured flows in the direction of the arrow from the connection part 2 first through the forward conductor 6 and then in the opposite direction through the return conductor 7 to the connection part 3. The forward conductor 6 and the return conductor 7 are each composed of a conductor material, for example copper, and guide the current I to be measured in opposite directions. This is advantageous because the magnetic field generated by the current I in the forward conductor 6 on the one hand and the current I in the return conductor 7 on the other hand cancel each other out on the inside.

The forward conductor 6 consists of four rectangular plates oriented at right angles to the connection part 2 and arranged on the upper side of the connection part 2. The rectangular plates of the return conductor 7 and the forward conductor 6 are connected to the upper side of the upper connecting portion 2 or the connecting portion 3 by a soldered connection 8a or 8 b.

The rectangular plate of the forward conductor 6 is also connected at its upper side to the rectangular plate of the return conductor 7 by means of a soldered connection 9.

It should be noted that the rectangular plate of the return conductor 7 is divided in two and separated by a gap 10, said gap 10 preventing current from flowing between two adjacent portions of the return conductor 7.

The gap 10 is bridged by inserts 11, each of which is embedded in and connected to a shoulder in an adjacent plate of the return conductor 7.

The insert 11 is shown in detail in fig. 1D and 1E and is composed of two plate-shaped conductor elements 12, 13 made of a conductor material (e.g. copper) and a resistive material (e.g. copper) located in between) The resistor element 14 is made. The inserts 12, 13 can be made, for example, from a composite material strip, as is known, for example, from EP 0605800 a 1. The current I to be measured therefore flows through the insert 11 and thus also through the resistor element 14 when flowing through the return conductor. The voltage drop U (see fig. 2A) over the resistor element 14 of the insert 11 thus forms a measure of the current to be measured according to ohm's law. This voltage drop is measured via a measuring circuit arranged on a printed circuit board 15, wherein the printed circuit board 15 is arranged inside the return conductor 7 and is oriented at right angles to the current flow direction.

Due to the expected inhomogeneity of the current distribution within the resistor, a large number of pairs of voltage taps are formed, the measured values of which are averaged in a suitable manner.

In a simplified version of a lower current or higher resistance value, the insert may form a complete return conductor including the return conductor 7.

Two punch-out elements 16, 17 are provided for the electrical connection of the printed circuit board 15 to the two plate-like connecting sections 12, 13 of the inlay 11, as can be seen in particular from fig. 2A and 2B.

Preferably, the two stamped parts 16, 17 are connected to the two plate-like connecting portions 12 and 13 of the insert 11 by a sintered connection. For this purpose, a silver sintering paste is first printed on the conductor elements 12 and 13 and dried. The stamped parts 16, 17 are then precisely applied in a low temperature sintering process (250-260 ℃). The sintered connection layer consists of pure silver and has a thickness of between 30 μm and 70 μm, depending on the pressing density of the sintering paste. This connection between the stamped parts 16, 17 on the one hand and the conductor elements 12, 13 on the other hand has not been subjected to a subsequent soldering process without damage, in which the entire coaxial resistor 1 is soldered. The connection becomes more stable by the strong diffusion of copper and silver. However, the connection can also be made as a welded connection or a brazed connection.

The voltage side punch 16 has two adjacent contact lugs 18, 19, wherein a contact lug 20 is formed on the ground side punch 17, which contact lug 20 is centered between the two contact lugs 18, 19 of the voltage side punch 16. As shown in fig. 2A, the contact tabs 18-20 are correspondingly bent to contact the printed circuit board 15. During assembly, the printed circuit board 15 rests on the shoulders of the bent contact tabs 18-20 as positioning aids. The contact tabs 18, 19 together form a voltage tap on the high voltage side (voltage side), while the contact tab 20 forms a voltage tap on the low voltage side (ground side).

The large number of solder connections between the printed circuit board 15 and the inlay 11 ensures a good strength of the connection between the printed circuit board 15 and the coaxial resistor 1, so that the curved contact tabs 18-20 allow a certain mechanical compensation in case of tension due to temperature changes.

The double contact lugs 18, 19 on the voltage side (high voltage side) have the following advantages: the temperature of the voltage side is efficiently transferred to the printed circuit board 15 by good heat conduction via the contact tabs 18, 19 (double, short length, wide contact and extremely high thermal conductivity). Thereby, the entire temperature difference of the shunt structure is applied on the composite terminal 20, so that the thermoelectric voltage compensation can function properly.

The ground-side punch 17 consists of the same composite material strip as the insert 11, in order to be able to compensate for the unavoidable thermoelectric voltage in the insert as optimally as possible. Preferably, the mass-produced stamping parts 17 even consist of the same composite material strips of the same batch.

Fig. 3A and 3B show details of the printed circuit board 15. Fig. 3A shows that in the case of implementation, each insert 11 forms three pairs of voltage taps. Fig. 3B shows that for each pair of voltage taps, the printed circuit board 15 has two connection pads 21, 22 for the contact tabs 18, 19 and a central connection pad 23 for the contact tab 20.

It should also be mentioned that the printed circuit board 15 is multi-layered and has R on its top side_SYMSymmetrical resistor, wherein R_SYMThe task of the symmetrical resistors is to weight the voltage measurement of the individual voltage tap pairs, as is known, for example, from DE 102013005939 a 1.

In addition, the top side of the printed circuit board 15 is provided with a compensation resistor R_KOMPTo compensate for the temperature dependence of the resistor elements, as is known, for example, from DE 102016008415.4.

Fig. 4 shows a simplified equivalent circuit diagram to illustrate the weighting of the voltage measurements of each voltage tap pair. The resistors R0, R1, … …, Rn are resistor elements 14 in each of the inlays 11. The resistors Ra, Rb correspond to the balancing resistor R in FIG. 3B_SYM. The function of this circuit is described, for example, in DE 102013005939 a1, to which reference is hereby made.

Finally, fig. 5 shows an equivalent circuit diagram to illustrate the compensation thermal voltage Uth across the composite terminal 20. The function of such thermal voltage compensation is described, for example, in DE 102016008415.4, so reference is also made to this earlier patent application.

The figure also shows two copper resistors R connected in parallel_CU1And R_CU2Two copper resistors R_CU1And R_CU2Arranged in a second plane of the printed circuit board 15 and emanating from the copper terminals on the voltage side and acting as temperature sensors for TC compensation. In addition, two resistors R_CU1And R_CU2The average of the two potential values on the voltage side is calculated.

The invention is not limited to the preferred embodiments described above. Rather, a number of variations and modifications are possible which likewise make use of the inventive idea and thus fall within the scope of protection. The invention also claims the subject matter and features of the dependent claims, in particular independently with respect to the respectively cited claims. Accordingly, the present invention includes inventive aspects that enjoy protection independently of one another.

List of reference numerals

1 coaxial resistor

2 plate-like connecting part for current supply

Plate-like connection part for current consumption

4 holes in the connecting part for fastening the connecting contacts

5 holes in the connecting part for fastening the connecting contacts

6 forward conductor

7 return conductor

8a solder connection between the front conductor and the plate-like connection portion

8b solder connection between return conductor and plate-like connection portion

9 brazed connection between the forward conductor and the return conductor

10 gap in return conductor

11 composite material insert in return conductor

12. 13 plate-shaped conductor element of insert

14-embedded plate-shaped resistor element

15 printed circuit board

16 Voltage side punch component for voltage tapping

17 ground side punch member for voltage tapping

18. Contact tab for contacting a printed circuit board of a 19-voltage side stamped component

20 contact tab of ground side punch member for contacting printed circuit board

21. 22 connection pad for voltage side contact in printed circuit board

23 connection pad for ground side contact tab in printed circuit board

I current through a coaxial resistor

Balancing resistor in Ra, Rb printed circuit board

R_CU1、R_CU2Resistor for compensating temperature dependence

R_KOMPCompensating resistor on printed circuit board

R0, … …, Rn resistor element

R_MESSResistor element

R_SYMBalancing resistor on printed circuit board

Voltage drop across a U-resistor element

U_THThermoelectric voltage in ground side stamped parts made of composite material

U1, … …, voltage drop across Un resistor element R0, … …, Rn