Current Measurement System

Abstract

A current measurement system includes a multi-phase open-loop current transformer for measuring phase currents (I1, I2, I3) flowing in a plurality of n primary conductors of a multi-phase electrical system, the transformer including a housing (2), a magnetic core (3) including first and second core pieces (3a, 3b), and a plurality of n+1 magnetic field detectors (4) mounted in the housing (2) between the first and second core pieces where portions of the primary conductors that cross the current transformer housing are located. The system further includes a non-volatile memory storing information on at least one coupling matrix (K) predefined by a calibration procedure, the at least one coupling matrix connecting phase currents (I1, I2, I3) flowing in the primary conductors with induced magnetic fields (B1, B2, B3, B4) detected by the magnetic field detectors, and a calculation unit configured to calculate values ​​of the n phase currents from outputs of the n+1 magnetic field detectors using the coupling matrix. The calculation unit is further configured to estimate n-phase currents in the degraded mode using the n+1 degraded-mode coupling matrix, thereby enabling to detect a fault, leakage current, or overcurrent of the magnetic field detector.

Description

Disclosure Contents

[0001] The present invention relates to a current measurement system for a polyphase electrical system, including a polyphase open-loop current transformer.

[0002] Many electrical systems are supplied by polyphase current, particularly three-phase current, including electric motors in automotive applications such as electric vehicles. Such applications require current sensors that are robust, reliable, and economical to manufacture and install.

[0003] Safety is a critical factor, and current sensors must detect faults quickly and reliably so that control systems can shut down or change the settings of the faulty system. Overcurrents and leakage currents typically indicate a faulty electrical system.

[0004] The influence of external magnetic fields, which may arise, for example, from other electrical conductors and components in the vicinity of the current sensor, should not adversely affect the accuracy and reliability of the current sensor.

[0005] Additionally, current sensors implemented in harsh environments such as those found in electric vehicles must withstand mechanical shock, vibration, and large thermal variations.

[0006] Existing sensors face challenges in meeting the high demands for safety, durability, reliability, and accurate current measurement while addressing the need for economical manufacturing and installation.

[0007] It is known to provide a three-phase open-loop current transformer that includes magnetic core components assembled on opposite sides of three primary conductors arranged in a common plane to generate current outputs in each of the phases. Furthermore, when measuring current in two of the phases, the current in the third phase can be inferred from the other two phases. However, conventional open-loop current transformers of this type are relatively costly to install and operate and may lack the response time required to quickly address a fault. Furthermore, detection of a transformer fault may not be reliable.

[0008] In view of the above, it is an object of the present invention to provide a polyphase (especially three-phase) current measurement system with an open-loop current transformer that is economical to manufacture and install, yet robust, safe and reliable, while ensuring accurate measurements.

[0009] It would be advantageous to provide a multiphase current measurement system that can very quickly detect faults, particularly leakage currents or overcurrents.

[0010] It would be advantageous to provide a compact, multi-phase open-loop current transducer for a multi-phase current measurement system.

[0011] The object of the present invention is achieved by providing a multiphase current measurement system as claimed in claim 1.

[0012] The object of the present invention is achieved by providing a method for measuring a plurality of currents flowing in a plurality of n primary conductors of a polyphase electrical system as set forth in claim 14.

[0013] Disclosed herein is a current measurement system including a multi-phase open-loop current transformer for measuring phase currents (I1, I2, I3) flowing in a plurality of n primary conductors of a multi-phase electrical system. The transformer includes a housing, a magnetic core including first and second core pieces, and a plurality of n+1 magnetic field detectors mounted in the housing between the first and second core pieces where portions of the primary conductors that cross the current transformer housing are disposed. The system further includes a non-volatile memory storing information on at least one coupling matrix (K) of dimensions n×n+1 predefined in a calibration procedure, the at least one coupling matrix connecting phase currents (I1, I2, I3) flowing in the primary conductors with induced magnetic fields (B1, B2, B3, B4) detected by the magnetic field detectors, and a calculation unit configured to calculate values ​​of the n phase currents from outputs of the n+1 magnetic field detectors using the coupling matrix. The calculation unit is further configured to estimate n-phase currents in the degraded mode using n+1 degraded-mode coupling matrices, each of dimension n×n, based on outputs of subset n of the n+1 magnetic field detectors, thereby making it possible to detect a fault, leakage current, or overcurrent in the magnetic field detector.

[0014] Also disclosed herein is a method for measuring a plurality of currents (I1, I2, I3) flowing in a plurality of n primary conductors of a polyphase electrical system, the method comprising: - providing a current measurement system including a converter, the converter including a housing, a magnetic core including first and second magnetic core pieces, and a plurality of n+1 magnetic field detectors mounted within the housing between the first and second core pieces on which a portion of a primary conductor traversing the current converter housing is disposed, the converter being connected to a circuit of a polyphase electrical system; - prior to the operation of the converter to measure the phase currents flowing in the primary conductors, carrying out a calibration method for calculating at least one coupling matrix (K) of dimension n×n+1 that links the phase currents (I1, I2, I3) flowing in the primary conductors with the induced magnetic fields (B1, B2, B3, B4) detected by the magnetic field detectors; storing said at least one coupling matrix in a non-volatile memory of said circuit of a converter or of a polyphase electrical system; - calculating, in a calculation unit of the current measurement system, values ​​of the n phase currents from the measurement outputs of the n+1 magnetic field detectors using the at least one coupling matrix during operation of the converter to measure the phase currents flowing in the primary conductors; - in the calculation unit, calculating redundant measurements of a plurality of currents (I1, I2, I3) using a degraded mode coupling matrix of dimension n×n to detect faults of magnetic field detectors, wherein n of the n+1 magnetic field detectors for an n-phase system are calculated using the n+1 degraded mode coupling matrix (K 123 K 124 K 134 K 234 ) is used to calculate Includes.

[0015] In an advantageous embodiment, the non-volatile memory in which information relating to at least one coupling matrix (K) is stored is provided in at least one application specific integrated circuit (ASIC) forming at least one of the magnetic field detectors or is provided in a memory of a circuit of a transducer.

[0016] In an advantageous embodiment, the non-volatile memory in which information about at least one coupling matrix (K) is stored is readable by an external circuit via a connector of the current converter in order to transmit the information about the at least one coupling matrix to an external circuit and to calculate values ​​of the phase currents in the external circuit.

[0017] In an advantageous embodiment, the non-volatile memory in which information relating to at least one coupling matrix (K) is stored is located outside the converter and in the electrical system.

[0018] In an advantageous embodiment, the system further comprises a computation unit configured to perform at least two different computation methods for estimating the current, including, for example, a pseudo-inverse method such as Moore-Penrose inversion and a finite difference method.

[0019] In an advantageous embodiment, the first and second magnetic core components are in the form of substantially straight rectangular bars formed from a stack of laminated sheets of soft magnetic material.

[0020] In an advantageous embodiment, each of the magnetic core components is received in a respective housing component formed as separate components that are assembled together, one of the housing components housing a plurality of magnetic field detectors and a primary conductor portion extending through the housing.

[0021] In an advantageous embodiment, the passage through which the primary conductor extends is formed by a recess or through cavity in said one of the housing parts, the other housing part having an essentially planar mating surface.

[0022] In an advantageous embodiment, the transducer includes a circuit board arranged along a side of the housing that overlaps the connection terminals of the magnetic field detector in a plane substantially perpendicular to the plane in which the air gap between the magnetic core parts is formed.

[0023] In an advantageous embodiment, the magnetic field detector is pre-assembled to the circuit board during manufacture, whereby during assembly of the circuit board to the housing base part, the magnetic field detector is inserted into a cavity in the housing part for receiving the magnetic field detector, said cavities including cavities located outside any of the primary conductors and cavities between adjacent primary conductors.

[0024] In an advantageous embodiment, the converter is for use in a three-phase electrical system and includes four magnetic field detectors, two of which are positioned outside the three primary conductors and the remaining two are positioned between each of the adjacent primary conductors.

[0025] In an advantageous embodiment, the magnetic field detector is in the form of an ASIC.

[0026] In an advantageous embodiment, a comparator may be connected to each magnetic field detector configured to generate a control signal at a particular voltage threshold determined for each magnetic field detector in order to generate a shutdown control signal for the electrical system controlled by the current in the event of an electrical fault or overcurrent.

[0027] In an advantageous embodiment, the calculation unit of the circuit of the current measurement system performs a differential measurement of each phase current, the coupling matrix K' for the differential measurement being determined in a calibration method.

[0028] In an advantageous embodiment, the degradation mode matrix is ​​formed with nxn coefficients.

[0029] Further objects and advantageous features of the present invention will become apparent from the claims, detailed description and accompanying drawings. [Brief explanation of the drawings]

[0030] [Figure 1a] FIG. 2 is a perspective view of a current transducer of a current measurement system according to an embodiment of the present invention. [Figure 1b] FIG. 1b is a cross-sectional view through the current transducer of FIG. 1a; [Figure 1c] FIG. 1b is a perspective view of the current transformer of FIG. 1a without the primary conductor portion. [Figure 1d] 1b is a view of the transducer of FIG. 1a with the base and cover parts disassembled. [Figure 2] 1 is a perspective view of a variant of a current transformer according to an embodiment of the present invention with housing parts removed; [Figure 3a] FIG. 10 is a perspective view of a current transducer according to another embodiment of the present invention. [Figure 3b] FIG. 3b is a side view of the transducer of FIG. 3a. [Figure 4] FIG. 2 is a simplified schematic diagram illustrating a magnetic core component, a magnetic field detector, and a primary conductor of a current transformer according to an embodiment of the present invention. [Figure 5] 3 shows a flowchart of a method for calibrating a current transducer according to an embodiment of the present invention. [Figure 6] 1 is a flowchart of a safety analysis procedure for a current transformer according to an embodiment of the present invention. [Figure 7] 4 is a flowchart illustrating a measurement procedure for a current transducer according to an embodiment of the present invention. [Figure 8] 1 is a schematic representation of a portion of a signal processing circuit of a current converter according to an embodiment of the present invention, showing in particular a comparator function for detecting faults;

[0031] A current measurement system according to an embodiment of the present invention includes a current transducer 1 connected to circuitry (not shown) of an electrical system (not shown). The electrical system may be, for example, an electric motor or a controller for an electric motor or other type of electrical machine. The current measurement system includes circuitry for processing measurement signals, including a calculation unit. The calculation unit may be configured within the transducer 1 or may be part of an electrical system for processing measurement signals that is external to the transducer. In the latter embodiment, the current transducer 1 outputs a measurement signal from each magnetic field detector 4, which can then be processed by circuitry external to the transducer to calculate a current measurement of the current flowing in the primary conductor.

[0032] The computational unit may include or consist of any form of computational device (integrated circuit, FPGA, microcontroller, etc.) suitable for performing calculations and processing measurement signals.

[0033] Referring to the drawings, and in particular to Figures 1a to 4, a polyphase, in this case three-phase, open loop current transformer 1 according to an embodiment of the present invention comprises a housing 2, a magnetic core 3 comprising a first core part 3a and a second core part 3b, and a plurality of magnetic field detectors 4 mounted within the housing 2.

[0034] The current converter may optionally further include a signal processing circuit 5 connected to the magnetic field detector 4, and may optionally include a plurality of primary conductor portions 6a, 6b, 6c integrated into or pre-assembled with the current converter.

[0035] In embodiments, circuit 5 may include circuit traces for interconnecting the magnetic field detector to a connector for connecting it to an external circuit, but there are no electronic components for signal processing, so signal processing is performed in the circuitry of the electrical system to which the transducer is connected.

[0036] In one embodiment, the current transformer is configured for assembly around a primary conductor 6 of a polyphase electrical system (not shown) and may be provided without a primary conductor portion, with the current transformer housing including a passage 11 for receiving the external primary conductor 6 therethrough. In the illustrated embodiment, the current transformer is for a three-phase electrical system, e.g., for control of a three-phase electric motor. The primary conductor carries the current to be measured. However, it is also possible within the scope of the present invention to have two-, four-, five-, six-, or more-phase current transformers employing the principles described with respect to the three-phase embodiment.

[0037] The magnetic core parts 3a, 3b are made of a material with high magnetic permeability, in particular a soft magnetic material such as an FeSi alloy or FeNi, such magnetic materials being well known per se.

[0038] The magnetic core parts 3a, 3b may advantageously be in the form of straight or substantially straight rectangular bars, which are particularly economical to manufacture, for example by a stamping operation of sheets of soft magnetic material which are laminated to form the bars.

[0039] The magnetic core parts 3 a, 3 b form an air gap between them in which the primary conductor 6 and the magnetic field detector 4 are arranged. The air gap extends substantially along the plane P, whereby in an advantageous embodiment the primary conductor and the magnetic field detector can be aligned substantially along the plane P.

[0040] In an advantageous embodiment, the magnetic core components may be identical to further reduce manufacturing costs and simplify the number of components used to manufacture the current transformer.

[0041] The magnetic field detector 4 may advantageously be in the form of an application specific integrated circuit (ASIC) in which the integrated circuit constituting the magnetic field detector is overmolded and connected to connection pins for power and signal transmission; such ASICs are known per se in the field of current transducers. The ASIC may typically be based on a Hall effect detector, also known per se. In embodiments, other magnetic field detectors such as TMR (Tunnel Magneto Resistance) or GMR (Giant Magneto Resistance) may be used.

[0042] Each of the magnetic core parts 3a, 3b is received in a respective housing part 2a, 2b, which in an advantageous embodiment may be formed as separate parts that are assembled together and secured by latching elements 12 or other securing members (such as screws or clamps), or the housing parts may be secured together by welding or adhesive so that they cannot be separated after assembly.

[0043] Alternatively, as shown, the housing parts may be assembled together in situ, for example to be fitted around the primary conductor of an external system.

[0044] In variations in which the primary conductor portions 6a, 6b, 6c are directly incorporated into the current transducer, the housing parts 2a, 2b may be permanently formed, welded or placed around the primary conductor portions prior to assembly of the current transducer in an external installation for connection to an external primary conductor carrying the current to be measured.

[0045] The magnetic core parts 3a, 3b, located on either side of the magnetic field detector 4, have a width and length sufficient to completely cover and extend beyond the surface area of ​​the magnetic field detector when viewed in a direction D orthogonal to the plane P in which the primary conductor 6 and the magnetic field detector are aligned, so that external magnetic fields, e.g., due to electrical components in close proximity to the current transducer, are substantially uniformly distributed in the air gap between the two core parts 3a, 3b. The magnetic core parts 3a, 3b have a cross-section configured to be sufficient so that they do not reliably saturate at the specified maximum current measured by the transducer.

[0046] As will be described later, magnetic field values ​​resulting from external fields can be removed by differential measurements using a magnetic field detector.

[0047] The passages 11 through which the primary conductors 6, 6a, 6b, 6c extend may be formed by recesses or through cavities in one of the housing parts 2a (the base part 2a), while the other housing part 2b has an essentially planar mating surface that mates with the mating surface of the base part 2a. The primary conductors 6a, 6b, 6c may be provided, for example, in the form of rectangular bars as shown, although primary conductor bars of cylindrical, elliptical, trapezoidal or other profile shapes may also be provided.

[0048] The mating surface of the second housing part 2b in which the magnetic core part 3b is assembled may be coated with or provided with an insulating layer for insulatingly isolating the magnetic core part 3b from the primary conductors 6a, 6b, 6c.

[0049] The circuit 5 includes a circuit board 7, which may advantageously be arranged along a side 13 of the housing overlapping the connection terminals of the magnetic field detector 4 in a plane substantially perpendicular to the plane P in which the air gap is aligned.

[0050] The magnetic field detectors 4 may be pre-assembled to the circuit board 7 during manufacture, whereby during assembly of the circuit board to the housing base part 2a, the magnetic field detectors 4 are inserted into cavities 13 in the housing part for receiving the magnetic field detectors, said cavities including cavities 13a, 13d located outside either of the primary conductors and cavities 13b, 13c between adjacent primary conductors. Thus, for a three-phase electrical system, there will be four magnetic field detectors 4a, 4b, 4c, 4d, which in a particular advantageous embodiment are in the form of ASICs (referred to herein as ASIC1, ASIC2, ASIC3, ASIC4).

[0051] The housing 2 may include other elements, for example mounting projections 14 for fixing the current transformer to an external support.

[0052] The circuit 5 further includes a connector 8 for connecting to external circuitry including the signal processing circuitry of the current transducer and a power supply for driving the magnetic field detector, and for receiving the current measurement output from the current transducer.

[0053] In the illustrated embodiment, the connector 8 comprises a housing portion, which is directly integrated into the housing base part 2a and which includes pin terminals for connection to an external circuit board or for plugging into an external connector. Other types of contacts may be provided for plugging in or for clamping or soldering, as known per se in the art of connection systems.

[0054] In one embodiment, circuit board 7 of circuit 5 includes contacts 16 for the magnetic field detector, which are interconnected via circuit traces to electronic components on the circuit board that allow processing or pre-processing of the measurement signal before output via connector 8. A microcontroller for signal processing may, for example, be mounted on circuit board 7. In another embodiment, circuit board 7 of circuit 5 includes contacts 16 for the magnetic field detector, which are interconnected via circuit traces to connector 8, whereby processing of the measurement signal output by the magnetic field detector is performed in an external circuit to which the transducer is connected.

[0055] Depending on the embodiment, a computing unit implemented in the converter or external to the circuitry of the electrical system to which the converter is connected may advantageously be configured to perform several methods for processing the currents measured by the multiple magnetic field detectors to obtain accurate primary current values ​​for each of the phases, as shown, for example, in FIG. 7 .

[0056] In an advantageous embodiment, the method includes a pseudo-inverse method and a difference method. For both methods, and other methods that may be used within the scope of the present invention, a calibration procedure such as that shown in Figure 5 is performed to determine a coupling matrix K that links the phase currents I1, I2, I3 flowing in the primary conductors with the induced magnetic fields B1, B2, B3, B4 seen by the magnetic field detectors 4a, 4b, 4c, 4d (ASIC1, ASIC2, ASIC3, ASIC4). The coupling matrix may be a rectangular matrix with n x n+1 coefficients, where n is the number of phases to be measured and n+1 is the number of magnetic field detectors.

[0057] The pseudo-inverse method can advantageously perform calculations using the well-known Moore-Penrose inverse, which is useful for inverting non-invertible matrices, including rectangular matrices. In this method, the pseudo-inverse matrix K of the coupling matrix K of the induced magnetic fields {B1, B2, B3, B4} seen by the magnetic field detectors ASIC1, ASIC2, ASIC3, and ASIC4 is calculated. + Note that this method is expressed as the actual magnetic flux density measured by the ASIC, and may be expressed as the output signal of the ASIC (which may be a voltage V1, V2, V3, V4 signal, or a current signal, which may not include an offset in the signal).

[0058]

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[0059] This method allows one to directly find the unique matrix that makes the link between I and B, whereby the coupling matrix can be determined during a calibration process, which is preferably carried out during or after the manufacture of the transducer, before operating the transducer for current measurements when connected to a circuit in an electrical system.

[0060] According to an advantageous aspect of the invention, the coupling matrix may be stored in a non-volatile memory of the circuit 5 or in one or more non-volatile memories of the ASIC. In this way, the converter includes information about the coupling matrix, which may be used in a first embodiment to calculate current measurements in the converter in the case of an embodiment that includes a signal processing circuit having a calculation unit configured to output current measurements.

[0061] In another embodiment, information about the coupling matrix stored in the transducer may be transmitted to circuitry (not shown) of an electrical system to which the transducer is connected for processing of current measurement signals in the electrical system.

[0062] In another embodiment, information about the coupling matrix may be stored in a circuit of the electrical system external to the transducer, the coupling matrix being specific to the transducer and loaded into the memory of the circuit after performing a calibration procedure on said transducer.

[0063] The values ​​of the coupling matrix, which are determined during a calibration process for each transducer, or each production batch of transducers, prior to use of the transducer for current measurement in an electrical system to which the transducer is connected, advantageously provide matrix values ​​that are adjusted for each transducer, or each production batch of transducers, in this way accounting for manufacturing and material tolerances and variations in each transducer and therefore providing accurate measurements of each transducer when used to measure current in an electrical system.

[0064] In most cases, an external magnetic field will produce a substantially identical magnetic flux along the entire central air gap between the magnetic core parts 3a and 3b. In such cases, it is possible to eliminate the influence of this magnetic field on the current measurement, for example, using the method described below. The principle is to perform a differential measurement for each current, and the coupling matrix K' for the differential measurement can be determined using the same calibration method as described above (except that in the following equation, the ASIC output voltage signals V1, V2, V3, V4, which are images of the measured magnetic inductions B1, B2, B3, B4, are used instead).

[0065]

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[0066]

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[0067] The advantages of this method are: · Has a square K' matrix (easy to calculate) · Have differential measurements for each current (eliminates the influence of external fields on the measurement results) After analyzing the differential coupling matrix K', the coefficients representing the output of the ASICs closest to the phase conductor are significantly higher than the other coefficients of the ASICs further away from the phase conductor, for example by a factor of about 1000. This means that to perform a differential measurement, it is sufficient to use the two closest ASICs surrounding the phase conductor, and there is no need to use other ASICs to have a good measurement. In other words, the coupling coefficients from the more distant ASICs can be ignored with respect to the coupling coefficients from the closer ASICs.

[0068] Therefore, it is possible to simplify the problem to only three coefficients:

[0069]

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[0070] To provide measurement redundancy and detect failures of magnetic field detectors 4, a number n of the n+1 magnetic field detectors for an n-phase system, e.g., in this example, three of the four magnetic field detectors (for a three-phase system), can be used to define n+1 new degraded mode matrices (i.e., four in this example), which can then be used to estimate phase currents in another mode, referred to herein as the degraded mode:

[0071]

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[0072] n+1 reduced mode coupling matrix K abc may be a square matrix of n×n coefficients, where n is the number of phases to be measured and n+1 is the number of magnetic field detectors.

[0073] Each degraded mode coupling matrix K abc Since is a square matrix, it can be directly inverted. abc Although it cannot provide an accurate estimate of the current, it is possible to detect faults in the magnetic field detector. The degraded mode coupling matrix K abc is composed of n lines (Moore-Penrose K matrix):

[0074]

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[0075] If the magnetic field detector is faulty, the error will affect the calculated value of a particular phase current I1, I2, or I3, depending on which degraded mode coupling matrix is ​​used. Therefore, by comparing these phase currents I1, I2, and I3 calculated using the degraded mode coupling matrix, it is possible to identify the cause of the fault. Furthermore, this method can detect leakage currents. The safety analysis method, shown in Figure 6, is described below: 1. The phase currents I1, I2, and I3 are calculated using the degraded mode coupling matrix K 123 K 124 K 134 K 234 K Pseudo and K. Diff is estimated using 2. The sum of the three phase currents in each matrix is ​​calculated. 3. If all of these sums (S1) are null,

[0076]

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[0077]

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[0078]

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[0079]

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[0080]

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[0081]

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[0082]

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[0083] To improve safety, electrical faults need to be detected quickly, but estimating current takes too much time. To achieve faster detection, a comparator, as shown in Figure 8, can be implemented in the signal processing circuit to generate a control signal, such as a switch-off signal, at a specific voltage threshold. When high currents flow through the current transformers, each current can only be roughly estimated using the magnetic field detector closest to the corresponding primary conductor. Therefore, a voltage threshold can be determined for each magnetic field detector to generate a shutdown control signal for an external control system in the event of an electrical fault or overcurrent. For example, if I1 is high TIFF0007735280000014.tif618 (relative error 5-10%); the maximum current that stops the external system is I 1MAX If so, The file is TIFF0007735280000015.tif927.

[0084] Current transformers according to embodiments of the present invention advantageously enable the provision of compact and simple multi-phase current sensors (eg, three-phase current sensors).

[0085] The signal processing circuitry of the converter or in an external circuit connected to the current converter may advantageously be configured with at least two calculation methods for accurately estimating the current, which may advantageously include a pseudo-inverse method and a difference method.

[0086] The signal processing circuitry of the converter or in an external circuit connected to the current converter may advantageously further include a degraded mode of calculation for estimating the current, which allows for the detection of faults, leakage currents or overcurrents in the magnetic field detector.

[0087] [List of reference symbols used] Current Measurement System Current Transducer 1 Housing 2 Housing parts Base 2a Cover 2b Latch element 12 Passage for primary conductors 11 Mounting protrusion 14 Magnetic Core 3 First core part 3a and second core part 3b Magnetic field detector 4, 4a, 4b, 4c, 4d, 4e, 4f ASIC ASIC1, ASIC2, ASIC3, ASIC4 Hall Effect Detector Circuit 5 Circuit board 7 Contacts for the detector 16 Circuit Trace Contacts for connectors 18 Connector 8 Primary conductor 6 Phase conductors 6a, 6b, 6c Computational Unit

[0088] [Embodiment] (1) A current measurement system including a multi-phase open-loop current transformer for measuring phase currents (I1, I2, I3) flowing in a plurality of n primary conductors of a multi-phase electrical system, the transformer including a housing (2), a magnetic core (3) including a first core part (3a) and a second core part (3b), and a plurality of n+1 magnetic field detectors (4) mounted within the housing (2) between the first core part and the second core part where portions of the primary conductors that traverse the current transformer housing are located; the system further comprises: a non-volatile memory storing information about at least one coupling matrix (K) of dimension n×n+1 predefined in a calibration procedure, the at least one coupling matrix linking the phase currents (I1, I2, I3) flowing in the primary current with the induced magnetic fields (B1, B2, B3, B4) detected by the magnetic field detectors; and a calculation unit configured to calculate values ​​of the n phase currents from outputs of the n+1 magnetic field detectors using the coupling matrix; the calculation unit is further configured to estimate n-phase currents in a degraded mode using n+1 degraded-mode coupling matrices, each of dimension n×n, based on outputs of subset n of the n+1 magnetic field detectors, thereby making it possible to detect a fault, leakage current, or overcurrent in the magnetic field detector. (2) A current measurement system as described in embodiment 1, wherein the non-volatile memory in which information regarding at least one coupling matrix (K) is stored is provided in at least one application specific integrated circuit (ASIC) forming at least one of the magnetic field detectors or is provided in a memory of the circuit (5) of the converter. (3) The current measurement system of embodiment 2, wherein the non-volatile memory storing information about at least one coupling matrix (K) is readable by an external circuit via a connector (8) of the current converter to transmit the information about the at least one coupling matrix to an external circuit and calculate values ​​of the phase currents in the external circuit. (4) A current measurement system as described in embodiment 1, wherein the non-volatile memory in which information regarding at least one coupling matrix (K) is stored is located outside the converter within the electrical system. (5) The current measurement system of embodiment 1, further comprising a calculation unit configured to perform at least two different calculation methods for estimating current, including, for example, a pseudo-inverse method such as Moore-Penrose inversion and a difference method.

[0089] (6) A current measurement system as described in embodiment 1, wherein the first magnetic core component and the second magnetic core component are in the form of substantially straight rectangular bars formed from a stack of laminated soft magnetic material sheets. (7) A current measurement system as described in embodiment 1, wherein each of the magnetic core components is received in a respective housing component (2a, 2b) formed as a separate component that is assembled together, and one of the housing components (2a) houses the plurality of magnetic field detectors and the primary conductor portion extending through the housing. (8) A current measuring system as described in embodiment 1, wherein the passage (11) through which the primary conductor extends is formed by a recess or through cavity in one of the housing parts (2a), and the other housing part (2b) has an essentially planar mating surface. (9) A current measurement system as described in embodiment 1, wherein the converter includes a circuit board (7) arranged along a side (13) of the housing that overlaps with the connection terminals of the magnetic field detector in a plane substantially perpendicular to a plane (P) in which the air gap between the magnetic core parts is formed. (10) The current measurement system of embodiment 1, wherein the magnetic field detector is pre-assembled to the circuit board during manufacturing, whereby during assembly of the circuit board to the housing base part, the magnetic field detector is inserted into a cavity (13) in the housing part for receiving the magnetic field detector, the cavity including cavities (13a, 13d) positioned outside either of the primary conductors and cavities (13b, 13c) between adjacent primary conductors.

[0090] (11) The current measurement system of embodiment 1, wherein the converter is for a three-phase electrical system and includes four magnetic field detectors (4a, 4b, 4c, 4d), two of which (4a, 4d) are arranged outside the three primary conductors (6a, 6b, 6c), and the remaining two (4b, 4c) are each arranged between the respective adjacent primary conductors (6a, 6b; 6b, 6c). (12) A current measurement system as described in embodiment 1, wherein the magnetic field detector is in the form of an ASIC. (13) The current measurement system of embodiment 1, including a comparator connected to each magnetic field detector configured to generate a control signal at a particular voltage threshold determined for each magnetic field detector to generate a shutdown control signal for the current-controlled electrical system in the event of an electrical fault or overcurrent. (14) A method for measuring multiple currents (I1, I2, I3) flowing in multiple n primary conductors of a polyphase electrical system, comprising: a current measurement system including a transducer, the transducer including a housing (2), a magnetic core (3) including a first core part (3a) and a second magnetic core part (3b), and a plurality of n+1 magnetic field detectors (4) mounted within the housing (2) between the first core part and the second core part where a portion of the primary conductor that traverses the current transducer housing is located, the transducer being connected to a circuit of the polyphase electrical system; Prior to operating the converter to measure the phase currents in the primary conductors, performing a calibration method for calculating at least one coupling matrix (K) of dimension n×n+1 that couples the phase currents (I1, I2, I3) in the primary conductors with the induced magnetic fields (B1, B2, B3, B4) detected by the magnetic field detectors; storing said at least one coupling matrix in a non-volatile memory of said converter or of said circuit of said polyphase electrical system; in a calculation unit of the current measurement system, during operation of the converter to measure the phase currents flowing in the primary conductors, calculating values ​​of the n phase currents from measurement outputs of the n+1 magnetic field detectors using the at least one coupling matrix; In the calculation unit, calculating redundant measurements of the plurality of currents (I1, I2, I3) using a degraded mode coupling matrix of dimension n×n to detect faults in the magnetic field detectors, wherein n of the n+1 magnetic field detectors for an n-phase system are calculated using the n+1 degraded mode coupling matrix (K 123 K 124 K 134 K 234 ) is used to calculate A method comprising: (15) The method described in embodiment 14, wherein a calculation unit of the circuit of the current measurement system performs differential measurements of each phase current, and the coupling matrix K' for the differential measurements is determined by the calibration method.

Claims

1. The phase currents (I) flowing in multiple n primary conductors of a polyphase electrical system １ , I ２ , I ３ a multi-phase open-loop current transformer for measuring a current flowing through the housing, the multi-phase open-loop current transformer including a housing (2), a magnetic core (3) including a first core part (3a) and a second core part (3b), and a plurality of n+1 magnetic field detectors (4) mounted in the housing (2) between the first core part and the second core part, where a portion of the primary conductor that traverses the housing is disposed; The current measurement system includes a non-volatile memory storing information about at least one coupling matrix (K) of dimensions n×n+1, which is predefined in a calibration procedure, and the at least one coupling matrix is ​​used to calculate the phase currents (I) flowing through the plurality of n primary conductors. １ , I ２ , I ３ ) to the induced magnetic field (B １ , B ２ , B ３ , B ４ a non-volatile memory configured to store a rectangular matrix of coupling coefficients indicating degrees of coupling between the n+1 magnetic field detectors and the n+1 magnetic field detectors; and a calculation unit configured to calculate values ​​of phase currents flowing through the n primary conductors from outputs of the n+1 magnetic field detectors using the coupling matrix, the calculation unit is further configured to estimate, based on outputs of n of the plurality of n+1 magnetic field detectors, phase currents flowing in the plurality of n primary conductors in a degraded mode using n+1 degraded-mode coupling matrices of dimension n×n, each ignoring the coupling coefficient for a magnetic field detector farthest from a corresponding magnetic field detector, thereby making it possible to detect a fault, leakage current, or overcurrent in the magnetic field detector.

2. A current measurement system as described in claim 1, wherein the non-volatile memory in which information regarding the at least one coupling matrix (K) is stored is provided in at least one application specific integrated circuit (ASIC) forming at least one of the magnetic field detectors or is provided in a memory of a circuit (5) of the multi-phase open loop current converter.

3. 3. The current measurement system of claim 2, wherein the non-volatile memory storing information about the at least one coupling matrix (K) is readable by an external circuit via a connector (8) of the multi-phase open-loop current converter to transmit the information about the at least one coupling matrix to an external circuit and calculate values ​​of phase currents flowing in the plurality of n primary conductors in the external circuit.

4. A current measurement system as described in claim 1, wherein the non-volatile memory in which information regarding the at least one coupling matrix (K) is stored is located outside the multi-phase open-loop current converter within the multi-phase electrical system.

5. A current measurement system as described in claim 1, further comprising a calculation unit configured to perform at least two different calculation methods for estimating current, including a pseudo-inverse method and a difference method.

6. 2. The current measurement system of claim 1, wherein the first core piece and the second core piece are in the form of straight rectangular bars formed from a stack of laminated sheets of soft magnetic material.

7. 2. The current measurement system of claim 1, wherein each of the core parts is received in a respective housing part (2a, 2b) formed as separate parts that are assembled together, one of the housing parts (2a) containing the plurality of n+1 magnetic field detectors and the primary conductor portion extending through the housing.

8. 8. The current measuring system of claim 7, wherein the passage (11) through which the primary conductor extends is formed by a recess or through cavity in said one of the housing parts (2a), the other housing part (2b) having a planar mating surface.

9. 2. The current measurement system of claim 1, wherein the multiphase open-loop current converter includes a circuit board (7) arranged along a side (13) of the housing that overlaps with a connection terminal of the magnetic field detector in a plane perpendicular to a plane (P) in which the air gap between the core parts is formed.

10. 2. The current measurement system of claim 1, wherein the magnetic field detector is pre-assembled to a circuit board during manufacture, whereby during assembly of the circuit board to a housing part, the magnetic field detector is inserted into a cavity (13) in the housing part for receiving the magnetic field detector, the cavity including cavities (13a, 13d) arranged outside either of the primary conductors and cavities (13b, 13c) between adjacent primary conductors.

11. 2. The current measurement system of claim 1, wherein the multiphase open-loop current converter is for a three-phase electrical system and includes four magnetic field detectors (4a, 4b, 4c, 4d), two of which (4a, 4d) are arranged outside the three primary conductors (6a, 6b, 6c) and the remaining two (4b, 4c) are each arranged between a respective adjacent primary conductor (6a, 6b; 6b, 6c).

12. 10. The current measurement system of claim 1, wherein the magnetic field detector is in the form of an ASIC.

13. 10. The current measurement system of claim 1, including a comparator connected to each magnetic field detector configured to generate a control signal at a particular voltage threshold determined for each magnetic field detector to generate a shutdown control signal for the current-controlled polyphase electrical system in the event of an electrical fault or overcurrent.

14. The phase currents (I) flowing in multiple n primary conductors of a polyphase electrical system １ , I ２ , I ３ ) a method for measuring A current measurement system is provided, comprising a converter, the converter comprising: a housing (2); a magnetic core (3) including a first core part (3a) and a second core part (3b); and a plurality of n+1 magnetic field detectors (4) mounted within the housing (2) between the first core part and the second core part, where a portion of the primary conductor traversing the housing is disposed, the converter being connected to a circuit of the polyphase electrical system; Prior to operation of the converter to measure phase currents flowing through the plurality of n primary conductors, a phase current (I １ , I ２ , I ３ ) to the induced magnetic field (B １ , B ２ , B ３ , B ４ Executing a calibration method for calculating at least one coupling matrix (K) of dimension n×n+1, which is a rectangular matrix of coupling coefficients indicating the degree of coupling between the storing said at least one coupling matrix in a non-volatile memory of said converter or of said circuit of said polyphase electrical system; in a calculation unit of the current measurement system, during operation of the converter to measure phase currents flowing in the plurality of n primary conductors, calculating values ​​of phase currents flowing in the plurality of n primary conductors from measurement outputs of the n+1 magnetic field detectors using the at least one coupling matrix; In the calculation unit, a phase current (I) flowing through the plurality of n primary conductors is calculated using a reduced mode coupling matrix of dimension n×n to detect a fault in the magnetic field detector. １ , I ２ , I ３ ), wherein n of the plurality of n+1 magnetic field detectors for the polyphase electrical system each calculate a redundant measurement of n+1 reduced mode coupling matrices (K) of dimension n×n ignoring the coupling coefficients for the magnetic field detectors furthest from the corresponding magnetic field detector. １２３ K １２４ K １３４ K ２３４ ) is used to calculate A method comprising:

15. 15. The method of claim 14, wherein a calculation unit of a circuit of the current measurement system performs differential measurements of phase currents flowing in each of the plurality of n primary conductors, and a differential coupling matrix K′ for the differential measurements is determined by the calibration method.

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