Crosstalk-resistant sensors

Abstract

This disclosure describes a sensing capability resistant to crosstalk. A current sensor is provided for a target conductor among a plurality of conductors. The current sensor includes at least one magnetic sensor configured to provide two signals representing two different parameters of a field, the two different parameters being different components or their directional derivatives (e.g., gradients). The current sensor also includes a processor configured to derive a signal indicating a current based on a linear combination of a first signal and at least a second signal. At least one of these signals is weighted by coefficients that are constants selected based on the distance between the sensor and at least one of the plurality of conductors in at least a first or second direction. The coefficients are selected to reduce the contribution of parasitic magnetic fields to the signal indicating a current in the first conductor, wherein the parasitic magnetic field is generated by at least one other conductor.

Description

Technical Field

[0001] This invention relates to the field of current sensors. More specifically, it relates to current sensing by measuring the magnetic field induced by a current, including compensation for crosstalk components of the magnetic field. Background Technology

[0002] Current systems involving multiple conductors typically require precise measurements of the current flowing through those conductors. This is the case with multiphase current systems (such as electric motors). These currents are traditionally measured by measuring the magnetic field induced by the current flowing through the conductors. Magnetic sensors are used for non-contact magnetic sensing. The current is calculated from the measured magnetic field.

[0003] However, magnetic sensors measure the magnetic field at a given location, and this magnetic field is affected not only by the intended conductor but also by parasitic fields, stray fields, and so on. A key influence is crosstalk, which is caused by the magnetic field induced by nearby conductors other than the intended conductor carrying the measured current. Gradient measurements and common-mode magnetic sensing are affected by this source of error. Although crosstalk can be reduced by physically separating these conductors, such separation has practical limitations due to the need for compact current systems.

[0004] This effect is typically compensated for by the microcontroller using current information (e.g., using a crosstalk error matrix system).

[0005] The goal is to reduce the parasitic effects to an acceptable level without incurring significant computational costs. Summary of the Invention

[0006] The object of this invention is to provide a current sensor and sensing system according to the appended claims, wherein crosstalk contributed by adjacent magnetic field sources is reduced.

[0007] In one aspect, the present invention provides a current sensor for sensing a current passing through a first conductor or a target conductor among a plurality of conductors. The current sensor includes at least one magnetic sensor configured to provide a first signal representing a parameter (or derivative of a component of the magnetic field) of a magnetic field in a first direction, and the at least one magnetic sensor configured to provide at least a second signal representing a magnetic field (or derivative of a component of the magnetic field) in a second direction different from the first direction. The current sensor also includes a processor configured to derive a signal indicating the current based on a linear combination of the first signal and at least the second signal. At least one of these signals is weighted by coefficients selected as constants based on the distance between the sensor and at least one of the plurality of conductors in at least the first or second direction. The coefficients are selected to reduce the contribution of parasitic magnetic fields to the signal indicating the current in the first conductor, wherein the parasitic magnetic field is generated by at least one other conductor.

[0008] An advantage of embodiments of the present invention is that the current measured by a single magnetic-based current sensor can reduce crosstalk contributions without requiring additional signals from other sensors. For example, the coefficient is selected relative to the distance between the sensor and at least one conductor other than the target conductor to be measured (i.e., other than the first conductor).

[0009] In some embodiments of the invention, the processor is programmed with a coefficient selected based on the distance between the magnetic sensor and the first conductor.

[0010] The advantage of this invention is that the coefficient depends only on the air gap.

[0011] In some embodiments of the invention, the coefficient is selected based on the distance between the magnetic sensor and another conductor different from the first conductor in a direction perpendicular to the distance between the magnetic sensor and the first conductor.

[0012] The advantage of this embodiment of the invention is that the gain can be taken into account the conductor configuration.

[0013] The magnetic sensor may include a sensing element for sensing a magnetic field component in a first direction, and a sensing element for sensing a magnetic field component in a second direction different from the first direction.

[0014] The advantage of this invention is that gradient sensing, field component sensing, or a combination of both can be easily applied.

[0015] In some embodiments of the invention, the magnetic sensor includes at least two magnetic sensing elements for measuring a gradient or differential field in one direction. An advantage of these embodiments is that a gradient of the magnetic field in a given direction can be readily provided.

[0016] In some embodiments of the invention, at least one magnetic sensor and processor are integrated in a single package, such as in a single chip.

[0017] An advantage of embodiments of the present invention is that it can provide a very compact current sensor for measuring current through a conductor, the current sensor including signal processing capabilities, and optionally including an integrated magnetic concentrator.

[0018] In some embodiments of the present invention, at least one magnetic sensor includes a Hall effect sensor.

[0019] In one aspect, the present invention provides a current sensing system comprising a plurality of current conductors. Each conductor includes at least one current sensor according to an embodiment of the first aspect, each sensor being used to sense the current passing through each respective conductor and to reduce the contribution of parasitic magnetic fields generated by adjacent conductors among the plurality of conductors.

[0020] An advantage of this invention is that the device can be equipped with accurate current monitoring sensors that reduce crosstalk. Another advantage is that it can monitor the current flowing through each of the multiple conductors in the device.

[0021] In some embodiments of the invention, the coefficient of each sensor is a single coefficient optimized to minimize crosstalk between each corresponding conductor and other conductors.

[0022] The advantage of this invention is that the same gain can be used to compensate for any crosstalk field, thereby simplifying processor programming, calibration and installation.

[0023] The advantage of this invention is that the gain can be customized for each conductor, thereby obtaining very accurate current measurements with low crosstalk, including asymmetric systems.

[0024] In some embodiments of the invention, the current sensor is positioned along a portion of a conductor, wherein the portion is magnetically shielded.

[0025] The advantage of this invention is improved immunity to stray fields. Another advantage is that the sensing system is stable within mechanical tolerances.

[0026] In one aspect, the present invention provides a method for reducing crosstalk in a current sensor used to measure current through a target conductor, the method comprising:

[0027] - Determine the gradient of a first magnetic field parameter in a first direction and a second magnetic field parameter or magnetic field component in a second direction different from the first direction at the sensing position, wherein these parameters can be combined to obtain a value representing the current flowing through a conductor other than the target conductor when the current flows through the conductor other than the target conductor, and

[0028] - Calculate a weighting factor for which the combination of the gradients of the first and second field parameters or magnetic field components obtained when the current flows through a conductor other than the target conductor reduces the contribution of parasitic magnetic fields from one or more other conductors.

[0029] An advantage of this invention is that crosstalk from, for example, other conductors in the device can be compensated.

[0030] In some embodiments of the present invention, the method further includes placing a current sensor at the sensing location, wherein determining the first magnetic field parameter and the second magnetic field parameter includes measuring the first magnetic field parameter and the second magnetic field parameter. An advantage of embodiments of the present invention is that the current sensor can be calibrated.

[0031] In some embodiments of the invention, the method further includes determining a first magnetic field parameter and a second magnetic field parameter for a predetermined current flowing through the conductor.

[0032] In some embodiments of the present invention, the first magnetic field parameter is the gradient of a first component in the direction between the conductor and the sensing position, wherein the gradient direction is perpendicular to the first component and also perpendicular to the current, and the second magnetic field parameter is the magnetic field component in the direction perpendicular to the first magnetic field component and also perpendicular to the current.

[0033] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be suitably combined with features of the independent claims and other dependent claims, and not merely as expressly set forth in the claims.

[0034] These and other aspects of the invention will be apparent from the embodiments(s) described thereafter, and are illustrated with reference to these embodiments. Attached Figure Description

[0035] Figure 1 This is a top view of a sensor used to detect the current passing through a conductor, where the nearby conductor also carries the current.

[0036] Figure 2 yes Figure 1 The image shows a cross-section of the sensor and magnified details of the sensor's cross-section, illustrating the different components of the sensor.

[0037] Figure 3 The diagram illustrates two conductors through which current flows, each with a current sensor at its top. The magnetic field induced by the current flowing through the target conductor is shown. The current sensor measures this field. However, nearby non-target conductors also induce magnetic fields, thus affecting the current sensor readings.

[0038] Figure 4 A schematic diagram of the two conductors as described above is shown. In this case, the diagram illustrates the specific effect of the nearby conductors on differential sensing.

[0039] Figure 5 This is a schematic top view of a current sensor, which includes a horizontal Hall plate for reading the differential field, and a horizontal Hall plate combined with an MC to provide readings of the magnetic field in the horizontal and vertical directions.

[0040] Figure 6 This is a schematic top view of a current sensor, which includes a horizontal Hall plate for reading a differential field and a vertical Hall plate for providing readings of the magnetic field in the horizontal direction.

[0041] Figure 7 This is a schematic top view of a current sensor, which includes a horizontal Hall plate for reading a differential field, two vertical Hall plates for reading a horizontal field, and a vertical Hall plate for reading a vertical field.

[0042] Figure 8 It is a cross-section of a system comprising three conductors with corresponding current sensors, which obtain readings from measurements of the magnetic field.

[0043] Figure 9 It is a top view of the asymmetrical distribution of conductors, with a current sensor on top of each conductor.

[0044] These accompanying drawings are illustrative and non-limiting. In the drawings, some elements may be enlarged and not drawn to scale for illustrative purposes.

[0045] Any reference numerals in the claims should not be construed as limiting the scope.

[0046] In different accompanying drawings, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0047] The invention will be described with reference to specific embodiments and certain accompanying drawings, but the invention is not limited thereto but is defined solely by the claims. Dimensions and relative dimensions do not correspond to actual reductions in practice.

[0048] Furthermore, the terms "first," "second," etc., used in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe an order in time, space, rank, or any other way. It should be understood that the terms thus used are interchangeable where appropriate, and the embodiments of the invention described herein can operate in an order different from that described or illustrated herein.

[0049] Furthermore, the terms "top," "below," etc., used in the specification and claims are for descriptive purposes and are not necessarily used to describe relative positions. It should be understood that such terms are interchangeable where appropriate, and that embodiments of the invention described herein can operate in orientations different from those described or illustrated herein.

[0050] It should be noted that the term "comprising" as used in the claims should not be construed as limiting itself to the means listed thereafter; it does not exclude other elements or steps. Therefore, the term should be interpreted as specifying the presence of the stated features, integers, steps, or components as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the term "comprising" covers both cases where only the stated features are present and cases where these features are present along with one or more other features. Therefore, the scope of the statement "device comprising means A and B" should not be construed as limiting it to a device consisting only of components A and B. This means that, for the purposes of this invention, the relevant components in the device are only A and B.

[0051] Throughout this specification, the reference to "an embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the appearance of the phrase "in an embodiment" or "in an embodiment" throughout this specification does not necessarily refer to all of the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, as will be apparent to those skilled in the art from this disclosure, particular features, structures, or characteristics may be combined in any suitable manner.

[0052] Similarly, it should be understood that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, drawing, or description for the purpose of simplification and to aid in understanding one or more of the various inventive aspects. However, this method of disclosure should not be construed as reflecting an intention to claim more features than are expressly recited in each claim. Rather, as reflected in the appended claims, the inventive aspect lies in fewer features than all the features of a single foregoing disclosed embodiment. Thus, the claims appended to the Detailed Description are thereby explicitly incorporated into this Detailed Description, wherein each claim itself represents a separate embodiment of the invention.

[0053] Furthermore, while some embodiments described herein include features that are included in other embodiments but not others, it will be understood by those skilled in the art that combinations of features from different embodiments are intended to fall within the scope of the invention and form different embodiments. For example, any embodiment of the claimed embodiments in the appended claims may be used in any combination.

[0054] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0055] This invention relates to magnetic field sensing, and more specifically to current sensing by measuring magnetic field parameters, while having the potential to reduce the influence of other undesirable sources (e.g., reducing crosstalk from nearby magnetic field sources). These sources can be current conductors. The invention can be applied to current sensing of a busbar in a device such as an electric motor when current flows through a busbar other than the one being measured. However, the invention can be applied to other devices, such as transformers. In embodiments of the invention, a reference busbar is used as a conductor among multiple conductors in the device; however, the invention can be applied to any other type of conductor, such as wires, cables, rails, etc.

[0056] A magnetic field is induced by an electric current flowing through a conductor, and this magnetic field can be detected by a magnetic sensor. Since current and magnetic field are correlated through induction, the current flowing through the conductor can be derived from the measured magnetic field. The magnetic sensor provides a signal representing the magnetic field. For example, a signal indicating the magnetic field can represent its derivative, such as its gradient.

[0057] This method assumes that the only source of the magnetic field is the current flowing through the conductor. However, other sources also contribute to the magnetic field, and in some cases, this contribution is large enough that the obtained current differs from the actual current flowing through the conductor being tested by an unacceptable margin. The current in nearby conductors is the primary source of this contribution.

[0058] When “crosstalk” (or simply CT) is mentioned in the embodiments of the present invention, it refers to the contribution of current from a conductor other than the conductor being tested to the magnetic field being measured.

[0059] While CT is typically reduced by increasing the distance between conductors, when conductors are part of a device, the possibilities are limited by the device's geometry and compactness requirements.

[0060] This invention allows for the reduction of CT by measuring different field parameters (e.g., in different directions) and calculating the current based on these measurements (further including at least one weighting coefficient for correcting the current measurement). The weighting coefficient G (or simply the coefficient) is selected to reduce the contribution of CT. This selection can be made theoretically, through simulation, empirically, etc. Once the coefficient is obtained, this can be implemented directly in a programmable processor.

[0061] The sensor provides at least two signals representing the magnetic field. These signals can represent: a first parameter, which is a component of the field or a directional derivative of a predetermined order of said component; and a second parameter, which is a second component in a different direction or a directional derivative of a different order of said second component. The directional derivative can be in the horizontal direction. If both signals include derivatives, they can be derivatives in the same direction, such as a horizontal direction perpendicular to the direction between the sensor and the conductor.

[0062] This invention allows for the reduction of current transformer (CT) using measurements from a single current sensor. This coefficient depends solely on the geometry of the system, including the sensor and busbar. In other words, the sensor can be reprogrammed for different devices, taking into account only the relative positions of the components of those devices.

[0063] For example, in some embodiments, the coefficient depends only on the distance between the magnetic sensor and the conductor. This means that crosstalk can be compensated for without physically separating the busbars from each other, allowing for reduced distances between busbars and even other conductors. Devices implementing this invention can be more compact.

[0064] CT scans can be eliminated by the contribution of the combined magnetic field using the following general relationship:

[0065]

[0066] The coefficient G is a weighting factor. The dependence of CT on different parameters (e.g., in different directions) can be calculated, simulated, or obtained experimentally, for example, by testing the effect of an external magnetic source on the magnetic field parameters measured by a current sensor during calibration. The weighting factor G can then be chosen to eliminate CT. In other words, G can be determined to conform to the general relationship described above.

[0067] The above equation can be solved using expressions for magnetic fields in two different directions. In the remainder of this disclosure, these two different directions are two perpendicular directions. One is the Z direction, defined between the conductor under test and the magnetic sensor, and the other direction (or X direction) is defined perpendicular to the direction of the current flowing through the conductor and also perpendicular to the Z direction. The Z direction will be labeled "vertical direction," and the X direction will be labeled "horizontal direction." However, the magnetic field parameters can be measured in any two different directions of the magnetic field, and these directions are not necessarily perpendicular.

[0068] The expression for the magnetic field from the distant conductor is as follows:

[0069]

[0070]

[0071] Further derivatives can be obtained (the gradient in one direction, which is horizontal in this case). In a multiphase configuration, the expression can utilize x 2 >z 2 To approximate this, a weighting coefficient G can be obtained, taking into account the magnetic field. Based on the derivative (values ​​of i, j), this coefficient will depend on the distance between the sensor and the busbar (1 / z), also known as the air gap, or the coefficient can depend on the horizontal distance between the sensor and the adjacent busbar (1 / x, 1 / x). 2 ), or depends on both (e.g., z / x) 2 ).

[0072] In other words, based on the parameters being measured, the weighting coefficients can be selected according to the distance between the sensor and the source of the magnetic field being measured (the conductor under test) and / or the horizontal distance between the sensor and the CT source (adjacent conductor). When the magnetic field is provided from the distant conductor, using the previously obtained expressions Bx, Bz, dBx / dx, dBz / dx, the value of coefficient G can be obtained from the air gap (in the vertical z direction) and also from the spacing between the sensors (in the horizontal x direction). Furthermore, since x... 2 >z 2The dependence of G on x is negligible, and the coefficient G depends only on the air gap (only in the z direction). Therefore, it is always possible to find a coefficient G that reduces CT, so once calibrated, the sensor will suppress not only CT from a single source or from a single conductor, but also from other sources located at different gaps (e.g., a third current i3 through another conductor, see below for example). Figure 8 ) CT scan.

[0073] In some embodiments of the invention, more than two terms can be used to obtain multiple weighting coefficients, thereby allowing for finer adjustment. The following expressions are typically used with pairs of terms separated by one derivative order:

[0074]

[0075] The invention is not limited thereto. For example, the two terms in a pair may have the same derivative order (e.g., Bx - G Bz = 0), or they may be separated by more than one derivative order. However, the invention is not limited thereto, and the two terms may be components of a field and their derivatives, such as gradients in one direction (e.g., Bz and dBz / dx).

[0076] In a first aspect, the present invention provides a sensor for measuring current. The sensor includes a magnetic sensing system that provides signals corresponding to measurements of different magnetic field parameters (e.g., magnetic field parameters for different directions).

[0077] The sensing system can be adapted to provide measurements of magnetic field parameters in two different directions (e.g., two perpendicular directions). These parameters may include magnetic fields in two different directions, or a magnetic field in a first direction and gradients of magnetic fields (or differential fields) in different directions, or gradients of fields in two different directions across a single direction. In some embodiments, it may be adapted to provide a measurement of a parameter in one direction and the derivative of the same parameter, such as a gradient, for example, gradients in different directions.

[0078] In some embodiments, the sensing system includes at least one magnetic sensor adapted to provide the desired parameters. For example, the magnetic sensing system may include two sensors, one for each parameter. For instance, the first sensor may provide a signal representing the magnetic field in a first direction, and the second sensor may provide a signal representing the gradient of the magnetic field in the first direction in a second direction different from (e.g., perpendicular to) the first direction. Higher-order directional reciprocals may be used. For example, the second signal may be a second derivative.

[0079] Figure 1A top view of a current sensor 100 for measuring current I1 through a conductor 200 such as a busbar is shown. The direction of current I1 is indicated by an arrow in the busbar. The magnetic field measured by the magnetic sensing system of the current sensor 100 includes a CT contribution from a nearby magnetic source, such as the current through (at least one) adjacent conductor 201 (e.g., another busbar).

[0080] G can be determined through simulation, calculation, or calibration. First, the current through conductor 200 can be determined by sensor 100 using the following equation:

[0081] I1 = A*Bx1 - G*dBz1.

[0082] A can be a constant. The sensor reading may be affected by the field generated by a nearby conductor (e.g., the second conductor 201). Ideally, the current I1 measured by sensor 100 indicates the current I1 in conductor 200, and sensor 100 suppresses the contribution of the second conductor 201. In other words, if conductor 200 does not conduct current, but the second conductor 201 conducts current, then the following relationship should be obtained:

[0083] I1 = A*Bx1 - G.dBz1 = 0.

[0084] According to this relationship, when a current is applied through the second conductor 201 and the current I1 through the first conductor remains at a predetermined and characterized value (e.g., it can remain 0), the value G (G = A*Bx1 / dBz1) is obtained. As previously mentioned, this can be achieved through calibration, for example, by actually applying a current through the second conductor 201 in a real system and measuring the field parameters Bx1 and dBz1 with sensor 100. However, Bx1 and dBz1 (and therefore G) can also be determined through simulation, calculation, or calibration.

[0085] This invention stipulates that, in order to reduce or eliminate crosstalk, the value of the weighting coefficient G is less than 1.

[0086] Figure 2 It shows the result of Figure 1 The cross-section is indicated by line II-II in the diagram. In zoomed area 110, current sensor 100 shows a magnetic sensing system or magnetic sensor 111, in which case the magnetic sensing system or magnetic sensor 111 includes two different magnetic sensing elements 112, which are combined with an integrated magnetic concentrator (IMC) 113 to detect magnetic parameters in different directions. Note that a single magnetic concentrator may be used. In any case, the use of a magnetic concentrator is optional, as other techniques can be used to detect magnetic field parameters in different directions (e.g., a combination of a vertical Hall plate and a horizontal Hall plate).

[0087] The sensor can be located at a distance of approximately 0.1 mm to 10 mm from its target conductor, for example, between 0.5 mm and 3 mm.

[0088] The magnetic sensor 111 can be electrically coupled to a processor 130, which is used for signal processing and output. The weight values ​​can be programmed in the processor 130.

[0089] In some embodiments of the invention, the magnetic sensing system is configured to provide two signals representing magnetic field components in two different (e.g., perpendicular) directions.

[0090] Figure 3 Two busbars 202 and 203 are schematically shown, each with a current sensor 100 and 101. The current i1 flowing through the first busbar 203 generates a magnetic field represented by two circles 301 and 302 centered on the busbar 203. The smaller circle 301 represents the magnetic field sensed by the corresponding sensor 101, while the larger circle 302 represents the magnetic field affecting the different current sensors 100. This is the CT component affecting the current sensor 100. Therefore, the sensor 100 detects the magnetic field formed by two components: one is the principal component of the magnetic field induced by the expected current i2 of the conductor under test (represented by the smaller circle 401 centered on the busbar 202 under test), and the other is the CT component of the magnetic field generated by the first busbar 203 (represented by circle 302).

[0091] At the right side of sensor 100, the contribution of the principal component in the first direction (horizontal direction X) is Bi. 2,X (Dashed arrow). The contribution of the CT component is Bi1, which corresponds to Bi in the two vertical directions shown above, corresponding to the horizontal and vertical directions. 1,X and Bi 1,Z (The dashed arrow) is decomposed.

[0092] The horizontal component of the magnetic field induced by the current i2 in the tested conductor 202 is Bi. 2,X The magnetic field detected by the sensor on the right is Bmeas,x, and it is influenced by the horizontal direction Bi of the CT component. 1,X The impact of. Therefore, B meas,x follow:

[0093] B meas,X =Bi 2,X +Bi 1,X And therefore Bi 2,X =B meas,X –Bi 1,X .

[0094] Since the sensing system measures the field in two directions, crosstalk can be determined as follows:

[0095] Bi 1X -GB meas,Z =0, so Bi 1,X =GB meas,Z .

[0096] This expression can be used to calibrate the weighting coefficient G. For example, setting current i2 to zero and turning on current i1 can provide G = B. meas,X / B meas,Z This value is the value at sensor 100 facing conductor 202 through which current i2 should flow. This can also be achieved through simulation, calculation, etc. This expression is a special case of the general relation shown above, where i = j = 0, and where each Bx,z is measured in a different direction. Therefore, by choosing weighting coefficients to reduce CT contribution, the magnetic field induced by the tested current i2 can be obtained from the following measurements:

[0097] Bi 2,X =B meas,X –GB meas,Z .

[0098] Based on this expression, the current passing through the busbar under test can be obtained.

[0099] This invention can be applied to gradient magnetic sensing systems.

[0100] In some embodiments, the magnetic sensing system may include two sensors, wherein a first sensor provides a signal representing a magnetic field in a first direction, and a second sensor provides a signal representing the gradient of a magnetic field in a second direction (different from the first direction, e.g., perpendicular) in the first direction.

[0101] Figure 4 Cross-sections of the two busbars 204, 205 are schematically shown. Only the associated current sensor 400 of the conductor 204 under test is shown. The current sensor 400 includes two sensing elements 401, 402 for obtaining the gradient (specifically, dBz / dx) of the vertical component of the field in the horizontal direction, obtained from measurements of Bz in the first sensing element 401 and the second sensing element 402, which are separated from each other in the horizontal direction X. These components are indicated by arrows labeled Bi2,z_401 and Bi2,z_402. However, the gradient measurement includes an additional component from the magnetic field Bi1 induced by the adjacent busbars 205. These components are indicated by dashed arrows labeled Bi1,z_401 and Bi1,z_402.

[0102] For the general relation shown above, where i = j = 1, we get dBz / dx – GdBx / dx = 0.

[0103] Due to symmetry, the current from the busbar under test 204 does not generate a field gradient in the horizontal direction. In other words, the horizontal contributions of the field induced by the current i2 through the busbar under test 204 at each sensing element cancel each other out. Therefore, the horizontal gradient of the magnetic field at the location of sensor 400 is only induced by the adjacent CT source (i.e., busbar 205), which is not under the test of the associated sensor 400, and the current i1 flows through busbar 205, so dBx / dx = dBx_measured / dx. For each sensing element 401, 402 of sensor 400, the CT field can be separated into a vertical component Bz and a horizontal component Bi1X. Therefore, the measured dBx / dx originates from the CT.

[0104] The parasitic component of the gradient of Bz is the contribution of the field of the current passing through the untested busbar 205 (dBi). 1,Z Therefore, the relation becomes:

[0105] dBz_parasitic / dx = G dBx_measurement / dx.

[0106] The corrected gradient of Bz in the horizontal direction (dBz / dx) is a parameter of the magnetic field induced by the current in the conductor under test. It can be obtained from the measurement of the gradient of Bz, and additionally from the measurement of the gradient of Bx, which is only the CT component. For correction, weighting factors need to be included:

[0107] dBz_correction = dBz_measurement – ​​dBz_parasitic = dBz_measurement - G.dBx_measurement.

[0108] The current inducing the field can be obtained from the correction gradient of the magnetic field in the vertical direction. This current is the current flowing through the conductor 205 facing the sensor 400.

[0109] In another embodiment, the first magnetic sensor is configured to detect a parameter of the magnetic field in the vertical direction (Z) as previously defined. This parameter is the gradient in the horizontal direction (X). Therefore, the first sensor provides a value representing dB. Z The signal is / dx, so the first sensor is the so-called "gradient sensor".

[0110] The second magnetic sensor is configured to detect the magnetic field itself or magnetic induction in the X direction as defined above. Therefore, the second sensor provides a component B representing the magnetic field vector in the X direction. X The signal.

[0111] In this case, the coefficient G can be derived from the relation dB as explained earlier. Z / dx+GB X=0. This expression is a special case of the general relation shown above, where i = 1 and j = 0.

[0112] Other gradient measurements can be provided. For example, the first sensor can provide a signal representing the second derivative, such as the Laplace operator d of the magnetic field in the second direction in the first direction. 2 B Z / dx 2 The second sensor can provide the gradient dB of the magnetic field in the first direction in the same first direction. X / dx. In this case, the coefficient G can be derived from the relation d 2 B Z / dx 2 +GdB X The expression is obtained from / dx=0. This expression is a special case of the generalized expression shown above, where n=1.

[0113] The sensing system can be a gradient sensing system, a common-mode field system, a sensing system for measuring a magnetic field in a certain direction (Bx, By, Bz), or a hybrid system that combines measurements of the magnetic field and its gradient or differential magnetic field. It can include any suitable magnetic sensor, such as a GMR, AMR, or Hall sensor. For example, a magnetic sensor for providing a gradient can include two sensing elements that provide a combined differential signal. The sensing system can also include a magnetic concentrator for focusing the magnetic field and directing it to the sensing elements. The magnetic sensing system includes a signal output for further processing.

[0114] In some embodiments of the invention, the field parameters provided by magnetic sensing include two or more parameters of the magnetic field in two different directions (e.g., gradient, magnetic field itself). For example, it may include the gradient dB of the magnetic field in the vertical direction Z. Z / dX (the perpendicular component of the magnetic field Bz, in the horizontal X direction), the magnetic field B in the horizontal direction X and the magnetic field B in the vertical direction Z By setting the following equation to zero, we can obtain the two weighting coefficients G. X and G Z :

[0115]

[0116] For example, for applications in three-phase systems (such as...) Figure 8In an embodiment of the sensor for the system shown, for the first sensor 403, it can be assumed that no current flows through the conductor 205 facing the sensor, and current i2 flows through the adjacent conductor 204, and another current i3 flows through another adjacent conductor 206. Therefore, two equations for the system can be obtained and solved for Gx and Gz. As previously mentioned, this can be accomplished through measurement and calibration, through calculation and / or simulation.

[0117] In embodiments of the present invention, different magnetic sensors can be used, such as Hall plates, magnetoresistive elements, etc. Figure 5 A first example of a magnetic sensor including horizontal Hall plates h1 and h2 is shown, which are sensitive to magnetic fields in the Z direction; the Bz component can be obtained from the sum of the signals from the horizontal Hall plates h1 and h2. A magnetic concentrator MC is added so that the Bx component of the magnetic field can be obtained by subtraction. The Bz component is obtained by summation. Optionally, two Hall plates h3 and h4 are added to extract dBz / dx.

[0118] Figure 6 An alternative magnetic sensor is shown, comprising a vertical Hall plate h1, which is sensitive in the horizontal (X) direction. Two plates h3 and h4 on either side provide signals, the difference of which provides dBz / dx.

[0119] Figure 7 An alternative magnetic sensor is shown, in which the sensing elements in the central region combine a horizontal plate h5 and a vertical plate h1. Optionally, a second vertical plate h2 is added, for example, to provide additional signals. The horizontal field component Bx can be obtained from the signals of the two vertical plates (h1+h2), while the vertical field component Bz can be provided from the signal of the horizontal plate h5. As shown in the previous figure, additional plates h3 and h4 can provide differential signals.

[0120] Combining signals (addition, etc.) can be accomplished in known ways, such as different types of connections, summation, etc.

[0121] Back Figure 2 A current sensor according to some embodiments of the present invention is shown in more detail. The current sensor 100 includes a processor 130 adapted to receive signals from a sensor of a magnetic system for providing a measurement signal adjusted using a factor G. The processed signal represents a current, wherein the current transformer (CT) from an external source is reduced. The processor can be implemented as an electronic circuit. In some embodiments, the current sensor 100 may include a semiconductor die 120 in which an integrated circuit is disposed. In some embodiments of the invention, the magnetic sensing system and the processor are integrated in the same semiconductor die, on a single chip (monolithically). However, the processor 130 may be connected to, for example, Figure 2The magnetic sensing system 111 shown is a separate unit.

[0122] The die 120 may further integrate one or more sensing elements 112, such as two additional Hall effect sensors 112 and an IMC 113. Thus, a highly integrated current sensor for a single busbar can provide a calibrated signal representing the current through that busbar without requiring a signal from an external sensor.

[0123] The processor can be programmed, and in some embodiments, can be reprogrammed, for example, with new or updated values ​​for one or more weighting coefficients. This allows the same current sensor to be used in different configurations of one or more conductors, such as busbars, and at different positions of the sensor relative to the one or more conductors.

[0124] In a second aspect, the present invention provides a system comprising a plurality of conductors. At least one sensor is configured to measure the current passing through one of the conductors. Preferably, the system includes one sensor for each conductor. The sensor may be the sensor of the first aspect of the present invention.

[0125] In some embodiments, multiple current sensors are used, and the current transformer (CT) of each sensor is reduced by including a single value for a weighting coefficient G for all current sensors. The advantage of this is that only a single coefficient is needed. Alternatively, the CT of each sensor is reduced by including a value customized for each current sensor (e.g., utilizing different weighting coefficients). Although a weighting coefficient needs to be obtained for each current sensor, the CT can be further reduced for this system. As previously mentioned, the value of coefficient G can be less than 1.

[0126] Figure 8 A system comprising three coplanar conductors 204, 205 and a current sensor overlapping each conductor is shown. Sensors 400, 403 are also arranged in the same plane and at the same distance from their respective conductors. In this particular embodiment, the system is symmetrical, so the current transformer (CT) on the first conductor of the sensor relative to the second conductor is the same as the CT on the second conductor of the sensor relative to the first conductor.

[0127] i1=f(Bx1,Bz1),i2=f(Bx2,Bz2),i3=f(Bz3,Bx3)

[0128] For example, i1 = Gx*Bx1 – Gz*Bz1, where Gz is chosen to remove crosstalk from i2 and / or i3.

[0129] Since Gx is independent of x, the same gain can be used to compensate for any CT field. Therefore, the CT contribution Bx is always proportional to the CT contribution of the gradient parameter ΔBz, which is the gradient dBz / dx in the x-direction.

[0130] Table I shows the percentage of the CT (Cross Transmission Temperature) of three sensors A, B, and C used to measure the current passing through three corresponding conductors A, B, and C. For example, the column corresponding to sensor A shows that the current through conductor A contributes 100% to the signal of sensor A because this current is the expected target current to be measured. However, the current through the nearest neighbor conductor B contributes 1.05%, and the current through the second nearest neighbor conductor C contributes 0.28%. The remaining columns are interpreted in the same way. This is the result of a gradient measurement of the change of the vertical component (Bz) of the field in the horizontal direction, i.e., dBz / dx. Since the system is symmetric, the effect of current A on sensor C is, for example, the effect of current C on sensor A is the same as the effect of current C on sensor A.

[0131] Table I. CT effects in symmetrical systems.

[0132] CT by percentage Sensor A Sensor B Sensor C Current at A 100.0 1.05 0.28 Current at B 1.05 100.0 1.05 Current at C 0.28 1.05 100.0

[0133] Table II includes a second measurement of the field parameter in the horizontal direction (Bx in this case) and its corresponding weighting coefficient Gx 0.5 in the calculation of CT. In this case, the CT from the adjacent conductor is significantly reduced, in some cases by as much as 14% (e.g., in the case of the influence of the current sensor A on C).

[0134] Table II. CT Correction dBz / dx + GxBx

[0135] CT by percentage Sensor A Sensor B Sensor C Current at A 100.0 0.0 0.04 Current at B 0.0 100.0 0.0 Current at C 0.04 0.0 100.0

[0136] Table III shows the CT percentages of three sensors A, B, and C, which are used to measure the current passing through three corresponding conductors A, B, and C, respectively, which are the first, second, and third conductors 600, 601, and 602 as explained above. However, in this case, the system is asymmetrical. The asymmetry may stem from the distribution of the magnetic field relative to the sensors. For example, if the air gap between each sensor and its corresponding conductor is not uniform, or if the conductors are not straight near the sensors, or if the conductors are not in the same plane. For example, the busbar 600 in the system may be bent near the current sensor 601, such as... Figure 9As shown. Unlike the symmetrical case, the effect of the current A through the first conductor 600 on the third sensor C is different from the effect of the current C through the third conductor 603 on the first sensor A (this is true for the effect of the current B through the middle conductor 601 on sensor A and the effect of the current A through the first conductor 600 on sensor B, as well as for sensors B, C and the middle and right conductors 601 and 602).

[0137] This is the result of a gradient measurement of the change of the vertical component (Bz) of the field in the horizontal direction, i.e., dBz / dx.

[0138] Table III. CT effects in asymmetric systems.

[0139] CT by percentage Sensor A Sensor B Sensor C Current at A 100.0 2.22 0.56 Current at B 0.37 100.0 0.96 Current at C 0.06 0.58 100.0

[0140] Table IV shows the reduction in CT by including a second measurement in the calculation, as previously described. The weighting coefficients can be the same for each sensor. For example, the processors for each sensor A through C can be programmed to implement the same weighting coefficients optimized to reduce CT.

[0141] Table IV. In this case, the weighting coefficient is Gx = -0.27 (for three sensors).

[0142] CT by percentage Sensor A Sensor B Sensor C Current at A 100.0 0.5 0.13 Current at B 0.1 100.0 0.36 Current at C 0.02 0.15 100.0

[0143] Table V shows the CT reduction when the processor for each sensor is programmed with different weighting coefficients. In most cases, the CT is further reduced compared to the results using a single coefficient.

[0144] The coefficients used in Table V are: G A X =-0.47, G B X =-0.36, G C X =-0.17

[0145] CT by percentage Sensor A Sensor B Sensor C Current at A 100.0 0.17 0.05 Current at B 0.0 100.0 0.02 Current at C 0.01 0.29 100.0

[0146] Table VI shows the CT reduction for each sensor corrected with three field parameters and two weighting coefficients in different directions, as explained above:

[0147]

[0148] It is possible to use only Gz while keeping Gx = 0. In this case, the signal obtained by the magnetic sensor represents the gradient dBz / dx of the vertical component (on x) and the vertical component of the field Bz (i.e., a weighted combination of the field and its gradient). Three different values ​​of Gz are used for each sensor, and the results are shown in Table VI. However, CT does not decrease in every case.

[0149] Table VI. The coefficient used is G. A Z =0.049, G B Z =-0.032, G C X =-0.02

[0150] CT by percentage Sensor A Sensor B Sensor C Current at A 100.0 0.07 0.09 Current at B 0.03 100.0 0.22 Current at C 0.07 0.9 100.0

[0151] Table VII shows the reduction in CT when the same weighting coefficient (-0.22) is used for the horizontal component of the field and different coefficients are used for each sensor for the vertical component of the field.

[0152] Table VII. Coefficients used: G X = -0.22 and G A Z =0.027, G B Z =-0.016, G C Z =0.005

[0153] CT by percentage Sensor A Sensor B Sensor C Current at A 100.0 0.03 0.04 Current at B 0.02 100.0 0.06 Current at C 0.01 0.06 100.0

[0154] Table VIII shows the reduction in CT when the processor of each sensor is configured to use different weighting coefficients (-0.22) for the horizontal component of the field and different coefficients for the vertical component of the field. In this case, G A X =-0.027, G B X =-0.24,G C X = -0.13 and G A Z =0.021, G B Z =-0.015, G C Z = -0.005

[0155] Table VIII. Each sensor is configured with different optimized weighting coefficients.

[0156] CT by percentage Sensor A Sensor B Sensor C Current at A 100.0 0.03 0.04 Current at B 0.02 100.0 0.06 Current at C 0.01 0.06 100.0

[0157] Different designs of the conductor and its distribution result in different readings. However, even in asymmetric configurations, it is possible to obtain weighting coefficients that reduce CT.

[0158] On the other hand, a method for calibrating a current sensor is provided. This method aims to reduce the current crosstalk (CT) on the current sensor. The method requires determining the magnetic field at the location where the current sensor, such as a non-contact sensor, is positioned, for example, as a sensor for sensing magnetic fields. The sensor can be placed to overlap with a target conductor, for example, close to the surface of the conductor, for example, between 0.1 mm and 10 mm from the conductor, or between 0.5 mm and 3 m. Determining the magnetic field further includes providing two different parameters of the magnetic field when an external active crosstalk source is present (therefore, current flows through a conductor other than the target conductor). The parameters may alternatively include a component of the field in a predetermined direction (e.g., Bz) and the derivative of that component, for example, derivatives in different directions (e.g., dBz / dx). The field can optionally be determined by assuming a known current flowing through the conductor or no current. These parameters can be combined to obtain a value representing the current flowing through the conductor other than the target conductor. The method then includes obtaining a weighting coefficient such that the parasitic contribution of the conductor other than the target conductor is reduced when at least one of the parameters applied to the magnetic field. The sensor indicates that the current in the induced field when no active CT source is present is substantially the same as the current in the induced field when an active CT source is present (e.g., when current flows through a nearby conductor other than the target conductor). In some embodiments, the method further requires determining the magnetic field at the same location, taking into account the active CT source generating the CT field. As previously mentioned, it can be assumed that a known current flows through the conductor, for example, the same current as described above.

[0159] For example, the corrected parameters can be calculated as a linear combination of defined parameters including a weighting coefficient G. The corrected parameters of the field can be used to obtain the corrected current through the conductor. In embodiments of the invention, the weighting coefficient G is less than 1.

[0160] The result can be the same, for example, within a negligible margin, such as when there are no other active sources, it can approach the value within a 1% margin.

[0161] Determining the magnetic field can be accomplished through design (e.g., through calculation, simulation, etc.). In some embodiments, determining the magnetic field can be accomplished by providing a current sensor for measuring the current flowing through the conductor, and using a magnetic sensing system to measure the magnetic field, further providing two parameters of the magnetic field in corresponding different directions. This measurement is performed when no external active CT source generates the field. Optionally, in the absence of an external active CT source, for example, in the absence of other nearby conductors carrying current, a known current may flow through the conductor. The measurement is repeated when an external active CT source generates a CT field (optionally, a known current (e.g., the same current as in the previous step) may flow through the conductor under test). For example, the external active source can be one or more conductors other than the conductor under test.

[0162] The method involves calculating weighting coefficients such that repeated measurements including CT active sources yield measurements similar to those without CT active sources.

[0163] This invention can be applied to DC battery monitoring relative to stray fields. Reducing the current transformer (CT) may be particularly advantageous in three-phase systems with several busbars (such as in electric motors, transformers, and coreless motors).

[0164] Note that the sensor provides two different parameters representing the magnetic field component, which can be in different directions, and the field is sensed by a current. Therefore, the processor can be programmed to combine the two signals representing the field in a linear combination to amplify the signal, for example, in different directions, such as the field component (e.g., Bx) and the derivative of a gradient (e.g., dBz / dx). The features and combination of this device are the same as those described above in this invention. However, the processor can be programmed to provide an increased signal by a weighting coefficient to obtain the current sensed by the field. For example, the weighting coefficient G can be set to 1 or higher. Thus, the resulting relationship is the same as before, however, where G is 1. Even if crosstalk is not reduced by the processing, the signal can be increased. This also allows for an increase in the signal-to-noise ratio. In cases where crosstalk is less important (due to shielding, large distance from other magnetic sources, etc.), this sensor can be used alone to provide the current through the conductor.

Claims

1. A current sensor (100) for sensing current through a first conductor (200) of a plurality of conductors, the sensor comprising: At least one magnetic sensor (111) is configured to provide a first signal representing a magnetic field parameter including a magnetic field component in a first direction or a directional derivative of the magnetic field component, and the at least one magnetic sensor (111) is configured to provide at least a second signal representing a magnetic field parameter including a magnetic field component in a second direction different from the first direction or a directional derivative of the magnetic field component in the second direction. A processor (130) is configured to derive a signal indicating the current based on a linear combination of the first signal and the at least second signal, wherein one of the first signal or the at least second signal is weighted by coefficients, wherein the coefficients are constants selected based on the distance between the sensor and at least one of the plurality of conductors (200, 201), at least in the first direction or the second direction, to reduce the contribution of a parasitic magnetic field to the signal indicating the current in the first conductor (200), wherein the parasitic magnetic field is generated by at least the other conductor (201).

2. The current sensor of the preceding claim, characterized in that The coefficient is selected based on the distance between the magnetic sensor (111) and the first conductor (200).

3. The current sensor as claimed in any of the preceding claims, characterized in that, The coefficient is selected based on the distance between the magnetic sensor and another conductor different from the first conductor in a direction perpendicular to the distance between the magnetic sensor and the first conductor.

4. The current sensor as described in any one of claims 1-2, characterized in that, The magnetic sensor includes at least two magnetic sensing elements for measuring a gradient or differential field in one direction.

5. The current sensor as described in any one of claims 1-2, characterized in that, The at least one magnetic sensor and the processor are integrated into a single chip.

6. The current sensor as described in any one of claims 1-2, characterized in that, The at least one magnetic sensor includes a Hall effect sensor.

7. A current sensing system comprising a plurality of current conductors, each conductor including at least one current sensor according to any one of the preceding claims, each sensor being configured to sense current through each respective conductor and to reduce the contribution of parasitic magnetic fields generated by adjacent conductors among the plurality of conductors.

8. The current sensing system as described in claim 7, characterized in that, The coefficients for each sensor are individual coefficients optimized to minimize crosstalk between each corresponding conductor and other conductors.

9. The current sensing system as described in any one of claims 7 or 8, characterized in that, The current sensor is positioned along a portion of the conductor, wherein the portion is magnetically shielded.

10. A method for reducing crosstalk in a current sensor used to measure current through a target conductor, the method comprising: A first signal and a second signal are determined. The first signal represents a first magnetic field parameter including a magnetic field component or a component directional derivative of the magnetic field component in a first direction at the sensing position. The second signal represents a second magnetic field parameter including a magnetic field component or a component directional derivative of the magnetic field component in a second direction different from the first direction. The first and second signals can be linearly combined to obtain a value representing the current flowing through a conductor other than the target conductor when the current flows through the conductor other than the target conductor. Calculate the weighting coefficients, for which the combination of the first and second signals obtained when the current flows in a conductor other than the target conductor reduces the contribution of the parasitic magnetic field from the conductor other than the target conductor.

11. The method of claim 10, further comprising placing a current sensor at the sensing location, wherein determining the first signal and the second signal comprises measuring the first magnetic field parameter and the second magnetic field parameter.

12. The method of claim 10 or 11, further comprising determining the first signal and the second signal for a predetermined current flowing through the conductor.

13. The method according to any one of claims 10 to 11, characterized in that, The first magnetic field parameter is the gradient of a first component in the direction between the conductor and the sensing position, wherein the gradient direction is perpendicular to the first component and also perpendicular to the current, and the second magnetic field parameter is the magnetic field component in the direction perpendicular to the first magnetic field component and also perpendicular to the current.

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