Sensor device and method for measuring an electric current

Abstract

The invention relates to a sensor arrangement having a planar electrical conductor which extends from an input side to an output side in a first direction and through which an electrical current to be measured can flow, wherein the electrical conductor has a narrowing of the cross section of the conductor in a section of the input side in a second direction towards the middle of the conductor, wherein the second direction lies in the plane of the conductor and is substantially perpendicular to the first direction, wherein the conductor has a punched part in the middle section, and a magnetic field sensor arrangement comprising at least one measuring element arranged in the region of the punched part, wherein the magnetic field sensor arrangement is designed to calculate a component of the electrical current in the first direction from the measuring signals of the at least one measuring element.

Description

Technical Field

[0001] This invention relates to a sensor device and a method for measuring current. In particular, the invention also relates to a sensor device for non-contact measurement of phase current between a converter and a motor. Background Technology

[0002] Measuring phase current without contact between the converter and the motor. Determining favorable conductor geometry is of paramount importance and has been the goal of decades of research and development. The challenge lies in providing conductor conductors that not only reduce the influence of the skin effect and proximity effect on the guided current, thus enabling high-frequency measurements, but also significantly suppress the effects caused by adjacent lines.

[0003] Different conductor geometries with holes, cuts, arbitrary conductor guides, and shielding measures are known.

[0004] An electronic circuit for detecting current is known from document CN 102016606 A. The circuit board includes main surfaces facing each other and current conductors for guiding current. The current conductors contain printed wires arranged on the circuit board.

[0005] Document US 8395382 B2 relates to a nonlinear sensor, such as a sensor having a substantially linear relationship between the sensor signal and the logarithm of the feature measured by the sensor.

[0006] Document US 10161971 B2 relates to a current sensor that measures the value of a current by detecting the magnetic field generated by the current. Summary of the Invention

[0007] The present invention relates to a sensor device and a method for measuring current having features according to the invention.

[0008] The preferred implementation is the content of the corresponding optional configuration scheme.

[0009] According to a first aspect, the present invention therefore relates to a sensor device comprising a planar electrical conductor and a magnetic field sensor device. The planar electrical conductor extends from an input side to an output side along a first direction. The current to be measured flows through the electrical conductor. The electrical conductor has a tapering portion in its cross-section along a second direction toward the middle of the conductor in a section on the input side. Here, the second direction lies in the plane of the conductor and is substantially perpendicular to the first direction, i.e., transverse to the first direction. The conductor has a stamped portion in its middle section. The magnetic field sensor device has at least one measuring element arranged in a region of the stamped portion. The magnetic field sensor device calculates the component of the current along the first direction based on the measurement signal from the at least one measuring element.

[0010] According to a second aspect, the present invention therefore relates to a method for measuring current, wherein current flows through a planar electrical conductor. The conductor extends from an input side to an output side along a first direction, wherein the conductor has a section on the input side that tapers in cross-section towards the center of the conductor along a second direction. The second direction lies in the plane of the conductor and is substantially perpendicular to the first direction, and the conductor has a stamped portion in the middle section. A measurement signal is generated by at least one measuring element arranged in the region of the stamped portion. The component of the current along the first direction is calculated based on the generated measurement signal.

[0011] Advantages of this invention:

[0012] The sensor device according to the invention enables contactless phase current measurement with minimal structural space requirements, wherein the bandwidth with respect to the frequency of current flowing through a planar conductor can be significantly improved. The measuring element of the magnetic field sensor device is arranged above a planar conductor having a stamped portion and at least one tapered portion. The application of ferrite rings or shielding plates for field shielding and field formation is not necessary, thus achieving particularly small structural space requirements.

[0013] What helps to reduce structural space requirements is that the space requirement is particularly small along the current flow direction, i.e., along the first direction. Modifications to the conductor's geometry, i.e., the tapering and stamping sections, extend essentially along the second direction.

[0014] The increase in resistance due to the additional structure can be adjusted by the size and shape of the structure, especially the edge segments of the tapered section.

[0015] The sensor device is largely insensitive to crosstalk, enabling high measurement bandwidth with low power loss, and, given appropriate sensor circuitry and placement, allows for robustness against external interference fields that are not only uniform but also gradient.

[0016] By having at least one measuring element staggered above the stamping section along a third direction perpendicular to the planar electrical conductor—which is substantially perpendicular to the first and second directions—no eddy currents occur directly below the at least one measuring element because there is no conductive material present. This reduces the inductive effects of adjacent conductors acting on the conductor.

[0017] According to a preferred extension of the sensor device, the relative positions and shapes of the tapered portion and the stamped portion are selected such that the region of highest current density extends from the outer region of the conductor at the tapered portion along the cross-sectional direction to the inner region of the conductor at the stamped portion along the cross-sectional direction. The term "relative positions and shapes of the tapered portion and the stamped portion" may specifically include the interval between the tapered portion and the stamped portion. Additionally or alternatively, the thickness, width, and / or height of the conductor may also be matched such that the region of highest current density extends from the outer region of the conductor at the tapered portion along the cross-sectional direction to the inner region of the conductor at the stamped portion along the cross-sectional direction.

[0018] Advantageously, the design of planar electrical conductors can be chosen in such a way that a 3-dB bandwidth greater than 100 kHz can be achieved, enabling the operation regulation algorithm to regulate harmonics in the motor current.

[0019] According to a preferred extension of the sensor device, the electrical conductor has a cross-section that tapers toward the middle of the conductor in the output side section.

[0020] According to a preferred extension of the sensor device, at least one measuring element of the magnetic field sensor device includes at least one Wheatstone bridge composed of magnetic field-sensitive resistors, such as tunneling magnetoresistance (TMR). The magnetic field and thus the current can be determined by measuring the change in resistance.

[0021] A full-bridge resistor can be configured such that the two magnetically sensitive resistors are located in opposite magnetic field regions and additionally have opposite sensitivities in pairs. This achieves resistance to scattering fields relative to a uniform magnetic field. This also multiplies the output signal.

[0022] According to a preferred extension of the sensor device, the measuring element of the magnetic field sensor device includes two Wheatstone bridges whose positions are identical along a first direction and different along a second direction. This allows for compensation of interference fields with gradients along the second direction.

[0023] According to a preferred extension of the sensor device, the measuring element of the magnetic field sensor device includes two Wheatstone bridges whose positions are identical along a second direction but different along a first direction. This allows for compensation of interference fields with gradients along the first direction.

[0024] According to a preferred extension of the sensor device, the magnetic field sensor device includes four measuring elements. A magnetic field with a high quadrupol-antieil component along the current flow direction is generated by a current-circulating stamping section. Compensation for external disturbance fields with gradients can thus be achieved using the four measuring elements. Preferably, a Wheatstone bridge with four measuring elements is used.

[0025] According to a preferred extension of the sensor device, the magnetic field sensor device is configured to eliminate the influence of a gradient-based interfering magnetic field by comparing the measurement signal of the Wheatstone full bridge when calculating the component of the current along a first direction.

[0026] According to a preferred extension, the sensor device has conductive elements arranged in a region of the stamped portion and staggered along a third direction perpendicular to the first and second directions. The conductive elements comprise a plurality of ferromagnetic structures extending along the second direction and spaced apart from each other along the first direction. Under high current conditions, the principal component of the magnetic field extending along the second direction (i.e., perpendicular to the current flow direction) perpendicular to the component to be measured achieves a high amplitude. By arranging conductive elements above and / or below the sensor elements, these sensor elements can effectively guide the field along the direction of the principal field component, thus interrupting it but not along the measurement direction, i.e., the first direction. This reduces the ratio of the magnetic field strength along the principal field direction to the magnetic field strength along the measurement direction. This simplifies the measurement of the magnetic field along the measurement direction. The conductive elements can, in particular, be laminated strips.

[0027] According to one embodiment of the sensor device, the conductive element can be directly separated by the measuring element in the separation method.

[0028] According to a preferred extension of the sensor device, the circumferential guidance of the main field component along the first direction can be achieved by means of a laminated stack (Blechpaket) that completely or partially surrounds the planar electrical conductor.

[0029] According to a preferred extension of the sensor device, the conductor has rounded edges in the region where the conductor's cross-section tapers. Attached Figure Description

[0030] The attached diagram shows:

[0031] Figure 1: A schematic perspective view of a planar electrical conductor used in a sensor device according to an embodiment of the present invention;

[0032] Figure 2 : A schematic perspective view of a planar electrical conductor with conductive elements used in a sensor device according to an embodiment of the present invention.

[0033] Figure 3 A schematic top view of a planar electrical conductor flowing through a current at a first frequency or a second frequency of the current in a sensor device according to an embodiment of the present invention.

[0034] Figure 4 A schematic top view of a sensor device according to an embodiment of the present invention;

[0035] Figure 5 : A flowchart of a method for measuring current according to one embodiment of the present invention.

[0036] In all the accompanying drawings, the same or functionally identical elements and devices are given the same reference numerals. Detailed Implementation

[0037] Figure 1 A schematic perspective view of a planar electrical conductor 2 used in a sensor device is shown. A first direction x corresponds to the current flow direction through the planar electrical conductor 2 from the input side 11 to the output side 12. A second direction y extends perpendicularly to the first direction in the conductor plane. A third direction z is perpendicular to the conductor plane.

[0038] The planar conductor 2 has a reduced conductor cross-section at three locations. Here, the planar conductor 2 has a stamped portion 4 in the middle section. In addition, the planar conductor 2 has a first tapered portion 3 of the conductor 2's cross-section in the input side section and another tapered portion 5 of the conductor 2's cross-section facing the middle of the conductor 2 in the output side section.

[0039] Preferably, the tapering portions 3 and 5 are symmetrical about the first axis A1 of the conductor 2, which extends along the first direction x in the middle. Therefore, the cross-section of the conductor 2 tapers from the edge to the middle.

[0040] Furthermore, preferably, the tapered portions 3 and 5 are arranged symmetrically with respect to the stamping portion 4. Therefore, the planar electrical conductor 2 is preferably symmetrical about a second axis A2 extending along the second direction y through the stamping portion 4.

[0041] However, the invention is not limited thereto. In particular, conductor 2 may also have an asymmetrical shape with respect to at least one of axes A1 and A2.

[0042] The stamping part 4 can be designed as circular or substantially elliptical.

[0043] Especially when the measurement bandwidth requirement is small, the tapered section 5 on the output side can be omitted, thereby further reducing the required structural space.

[0044] The planar electrical conductor 2 may, for example, have a geometry of 5 mm wide, 0.5 mm high, and 8 mm long. Preferably, the edges in the regions of the gaps 3 and 5 and the stamped portion 4 are rounded.

[0045] Figure 2 A schematic perspective view of a planar electrical conductor 2 with conductive elements 13 for use in a sensor device is shown. The conductive element 13 is designed as a stamped grid and extends at least above the stamping portion 4, and is arranged offset from the planar electrical conductor 2 along a third direction z. The conductive element 13 includes a plurality of ferromagnetic structures, i.e., laminated strips, which extend along a second direction y and are spaced apart from each other along a first direction x. The conductive element 13 is thus interrupted along the first direction x.

[0046] Figure 3 A schematic top view is shown showing the flow of current through a planar electrical conductor 2 used in a sensor device. The left side shows the current flowing at a frequency of 1 kHz, while the right side shows the current flowing at a frequency of 100 kHz.

[0047] As can be seen, by appropriately selecting the relative positions and shapes of the tapered portions 3 and 5 and the stamping portion 4, the following can be achieved: the region of highest current density extends from the outer region of conductor 2 in the tapered portion 3 (region A) along the cross-sectional direction to the inner region of conductor 2 in the stamping portion 4 (region B) along the cross-sectional direction. Region C describes the region that is crucial for sensing.

[0048] Figure 4 A schematic top view of sensor device 1 is shown. Sensor device 1 can be particularly installed in a frequency converter used for measuring phase current.

[0049] In addition to the planar electrical conductor 2 mentioned above, the sensor device 1 also includes a magnetic field sensor device 6.

[0050] The magnetic field sensor device 6 includes four Wheatstone bridges 7, 8, 9, and 10. Two of the Wheatstone bridges, 9 and 10, have the same coordinate along the second direction y, but are offset from each other along the first direction x. The remaining two Wheatstone bridges, 7 and 8, have the same coordinate along the first direction x, but are offset from each other along the second direction y.

[0051] Wheatstone bridges 7, 8, 9, and 10 are each magnetic field sensors, sensitive to the field component (along the first direction x) perpendicular to the main field component (along the second direction y) and parallel to the conductor surface. The magnetic field-sensitive measuring elements 7, 8, 9, and 10 are placed above the non-conductive section of the planar conductor 2, i.e., above the stamping section 4. Advantageously, Wheatstone bridges 7, 8, 9, and 10 include magnetoresistive elements. The sensitivity of the elements is preferably opposite in pairs. The elements are arranged above the conductor in such a way that they achieve a high signal level while remaining unaffected by a uniform scattered field. Preferably, Wheatstone bridges 7, 8, 9, and 10 are arranged above the planar conductor 2 with a 90-degree rotation relative to each other, as shown below. Figure 4 As shown. This allows for unaffectedness relative to a gradient-based interference field by calculating the difference and sum of the measured signals via signal processing from the magnetic field sensor device 6. The difference or sum corresponds to the interference field and the field to be measured.

[0052] Wheatstone bridges 7, 8, 9, and 10 can be arranged such that the two magnetically sensitive resistors are located in opposite field regions and additionally have opposite sensitivities in pairs.

[0053] Sensor device 1 may also have at least one in Figure 2 The conductive element 13 is shown in the figure.

[0054] Figure 5 A flowchart of a method for measuring the current passing through a planar conductor 2 is shown. This method can be implemented using the aforementioned sensor device 1. Specifically, the conductor 2 is designed such that a first tapering portion 3 of its cross-section along the second direction y is provided in the input section. A stamping portion 4 is provided in the intermediate section. Another tapering portion 5 of the conductor's cross-section along the second direction y can be provided in the output section.

[0055] In the first step S1, a measurement signal is generated by at least one measuring element 7-10 arranged in the area of ​​the stamping section 4.

[0056] In the second step S2, the component of the current along the first direction x is calculated based on the generated measurement signal. Specifically, a sensor device 1 can be used for this purpose, wherein four Wheatstone bridges 7, 8, 9, and 10 are arranged above the stamping section 4 and offset from each other by 90 degrees. By processing the measurement signals of the four Wheatstone bridges 7, 8, 9, and 10, interfering magnetic fields with gradients can be eliminated.

[0057] Furthermore, the sensor device used may have a conductive element 13, which is arranged in the region of the stamping part 4 and offset along a third direction z. The conductive element 13 includes a plurality of ferromagnetic structures that extend along a second direction y and are spaced apart from each other along a first direction x.

Claims

1. A sensor device (1), the sensor device comprising: A planar electrical conductor (2) extends from the input side (11) to the output side (12) along a first direction (x), and the current to be measured can flow through the planar electrical conductor, the first direction (x) corresponding to the current flow direction, wherein, The electrical conductor (2) has a tapering portion (3) in the input side section, the cross-section of the electrical conductor (2) being tapered towards the middle of the electrical conductor (2) along a second direction (y), wherein the second direction (y) is located in the plane of the electrical conductor (2) and is perpendicular to the first direction (x), wherein the electrical conductor (2) has a stamped portion (4) in the middle section, wherein the relative positions and shapes of the tapering portion (3) and the stamped portion (4) are selected such that the region of highest current density extends from the outer region of the electrical conductor (2) in the tapering portion (3) along the cross-sectional direction to the inner region of the electrical conductor (2) in the stamped portion (4) along the cross-sectional direction; A magnetic field sensor device (6) having at least one measuring element (7-10) arranged in the region of the stamping part (4), wherein the magnetic field sensor device (6) is configured to calculate the component of the current along the first direction (x) based on the measurement signal of the at least one measuring element (7-10).

2. The sensor device (1) according to claim 1, wherein, The electrical conductor (2) has another tapering portion (5) in the output side section, with the cross-section of the electrical conductor (2) facing the middle of the electrical conductor (2).

3. The sensor device (1) according to claim 1 or 2, wherein, At least one measuring element (7-10) of the magnetic field sensor device (6) includes at least one Wheatstone full bridge.

4. The sensor device (1) according to claim 3, wherein, The measuring element (7-10) of the magnetic field sensor device (6) includes two Wheatstone bridges (7, 8), the positions of which are the same along the first direction (x) and different along the second direction (y).

5. The sensor device (1) according to claim 3, wherein, The measuring elements (7-10) of the magnetic field sensor device (6) include two Wheatstone bridges (9, 10), which are in the same position along the second direction (y) and different from each other along the first direction (x).

6. The sensor device (1) according to claim 4, wherein, The measuring elements (7-10) of the magnetic field sensor device (6) include two Wheatstone bridges (9, 10), which are in the same position along the second direction (y) and different from each other along the first direction (x).

7. The sensor device (1) according to any one of claims 4 to 6, wherein, The magnetic field sensor device (6) is configured to eliminate the influence of a gradient-based interfering magnetic field by comparing the measurement signals of the Wheatstone full bridge (7-10) when calculating the component of the current along the first direction (x).

8. The sensor device (1) according to claim 1 or 2, wherein the sensor device has a conductive element (13) arranged in the region of the stamping portion (4) and offset along a third direction (z) perpendicular to the first direction (x) and the second direction (y), wherein, The conductive element (13) includes a plurality of ferromagnetic structures that extend along the second direction (y) and are spaced apart from each other along the first direction (x).

9. The sensor device (1) according to claim 1 or 2, wherein, The electrical conductor (2) has rounded edges in the region of the tapering portion (3) of the cross-section of the electrical conductor (2).

10. A method for measuring current, wherein, The current flows through a planar conductor (2), wherein the conductor (2) extends from the input side (11) to the output side (12) along a first direction (x), the first direction corresponding to the current flow direction, wherein the conductor (2) has a tapering portion (3) in the input side section, the cross-section of the conductor (2) extending along a second direction (y) toward the middle of the conductor (2), wherein the second direction (y) is located in the plane of the conductor (2) and is perpendicular to the first direction (x), wherein the conductor (2) has a stamped portion (4) in the middle section, wherein the relative positions and shapes of the tapering portion (3) and the stamped portion (4) are selected such that the region of highest current density extends from the outer region of the conductor (2) in the tapering portion (3) along the cross-sectional direction to the inner region of the conductor (2) in the stamped portion (4) along the cross-sectional direction; the method has the following steps: A measurement signal (S1) is generated by at least one measuring element (7-10), the at least one measuring element being arranged in the area of ​​the stamping part (4); The component of the current along the first direction (x) is calculated (S2) based on the generated measurement signal.

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