High-precision leakage current sensor based on array type magnetic elements

Abstract

The invention belongs to the technical field of sensors, and discloses a high-precision leakage current sensor based on array type magnetic elements, which comprises a sensing module, a signal conditioning module and a signal acquisition module, and is characterized in that the sensing module is used for sensing a magnetic field generated by a detected current in a detected object and outputting a sensing signal; the sensing module comprises a magnetism gathering device and N pairs of magnetic elements, a measured object passes through the middle of the magnetism gathering device, the magnetism gathering device is provided with an air gap, the N pairs of magnetic elements are arranged in the air gap and are arranged along a linear array, and the sensitive directions of the two magnetic elements in each pair of magnetic elements are opposite; the signal conditioning module is used for acquiring the sensing signal output by the sensing module and generating a conditioning signal; and the signal acquisition module is used for acquiring the conditioning signal generated by the signal conditioning module and obtaining the value of the detected current according to the conditioning signal. According to the invention, high-precision detection of the leakage current sensor is realized.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a high-precision leakage current sensor based on arrayed magnetic elements. Background Technology

[0002] A leakage current sensor is a device used to detect leakage current signals and convert them into voltage or current signals proportional to the magnitude of the leakage current. Common leakage current sensors typically use magnetic elements such as Hall effect sensors or TMR (Tunnel Magnetoresistance) as sensing modules, and employ a magnetic ring made of soft magnetic material to improve the magnetic focusing effect, thereby increasing detection accuracy. Based on their working principle, leakage current sensors can be divided into two types: open-loop and closed-loop. Open-loop leakage current sensors have the advantages of simple structure and low cost, but are greatly affected by temperature and have low accuracy. Closed-loop leakage current sensors have high accuracy and are less affected by temperature, but are technically complex and expensive.

[0003] High detection accuracy is one of the challenges of leakage current sensors. Currently, there are three main approaches to improve detection accuracy in leakage current sensors: First, using highly sensitive magnetic elements to improve the signal-to-noise ratio; however, the sensitivity of magnetic elements is limited. Second, reducing the air gap in the magnetic core to increase the magnetic field strength; however, this is limited by the packaging of the magnetic element, meaning the air gap cannot be smaller than the package size. Third, increasing the amplification factor of the signal conditioning circuit; however, the noise from the magnetic element and the circuit will be amplified simultaneously, thus affecting detection accuracy. Therefore, the detection accuracy of current leakage current sensors remains unsatisfactory. Summary of the Invention

[0004] The purpose of this invention is to provide a high-precision leakage current sensor based on arrayed magnetic elements, thereby achieving high-precision detection of leakage current.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-precision leakage current sensor based on arrayed magnetic elements includes: a sensing module, a signal conditioning module, and a signal acquisition module, wherein:

[0007] The sensing module is used to sense the magnetic field generated by the measured current in the object under test and output a sensing signal. The sensing module includes a magnetic focusing device and N pairs of magnetic elements. The object under test passes through the middle of the magnetic focusing device. The magnetic focusing device has an air gap. The N pairs of magnetic elements are arranged in the air gap and are arranged in a straight line array. The two magnetic elements in each pair of magnetic elements have opposite sensitive directions.

[0008] The signal conditioning module is used to acquire the sensing signal output by the sensing module and generate a conditioning signal;

[0009] The signal acquisition module is used to acquire the conditioning signal generated by the signal conditioning module and obtain the measured current value based on the conditioning signal.

[0010] Several alternative methods are provided below, but they are not intended as additional limitations on the overall solution above. They are merely further additions or optimizations. Provided there are no technical or logical contradictions, each alternative method can be combined individually with respect to the overall solution above, or multiple alternative methods can be combined with each other.

[0011] Preferably, the magnetic focusing device is a magnetic ring made of soft magnetic material.

[0012] Preferably, the two magnetic elements in each pair of magnetic elements are arranged along the extension direction of the linear array.

[0013] Preferably, the extension direction of the linear array is perpendicular to the flow direction of the measured current.

[0014] Preferably, when the direction of the current being measured is in the horizontal plane, the sensitive direction of one magnetic element in each pair of magnetic elements is vertically upward and the sensitive direction of the other magnetic element is vertically downward.

[0015] Preferably, the signal conditioning module includes an operational amplifier;

[0016] The positive signal output terminals of all magnetic elements in the N pairs of magnetic elements whose sensitive direction is the first direction are connected to the non-inverting input terminal of the operational amplifier, and the negative signal output terminals are connected to the inverting input terminal of the operational amplifier.

[0017] The negative signal output terminal of all magnetic elements in the N pairs of magnetic elements whose sensitive direction is the second direction is connected to the non-inverting input terminal of the operational amplifier, and the positive signal output terminal is connected to the inverting input terminal of the operational amplifier. The first direction and the second direction are opposite directions.

[0018] This invention provides a high-precision leakage current sensor based on arrayed magnetic elements. It employs an arrayed layout of multiple magnetic elements and combines it with a signal conditioning module to sum the vector differences of the differential outputs of the magnetic elements to improve the magnetoelectric conversion rate. The magnetoelectric conversion rate is proportional to the number of magnetic elements, thereby improving the detection accuracy of the leakage current sensor. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a high-precision leakage current sensor based on an array of magnetic elements according to the present invention;

[0020] Figure 2 This is a schematic diagram of the sensing module of the present invention;

[0021] Figure 3This is a schematic diagram showing the arrangement of N pairs of magnetic elements in this invention;

[0022] Figure 4 This is a schematic diagram of the signal conditioning module of the present invention;

[0023] Figure 5 This is a schematic diagram of the structure of the sensing module of a pair of magnetic elements according to the present invention;

[0024] Figure 6 This is a schematic diagram of the signal conditioning module for a pair of magnetic elements of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that when a component is said to be "connected" to another component, it can be directly connected to the other component or it can be connected to a component in between; when a component is said to be "fixed" to another component, it can be directly fixed to the other component or it can be connected to a component in between.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0028] like Figure 1 As shown, this embodiment provides a high-precision leakage current sensor based on arrayed magnetic elements, including: a sensing module, a signal conditioning module, and a signal acquisition module.

[0029] (1) Induction module, used to sense the magnetic field generated by the measured current in the measured object and output the induction signal.

[0030] In this embodiment, the sensing module includes a magnetic focusing device and N pairs of magnetic elements. The magnetic focusing device concentrates the weak magnetic field generated by the object under test, and the magnetic elements convert the magnetic field signal into a voltage signal, which is then connected to the signal conditioning module. The magnetic elements can be Hall effect elements, AMR (Anisotropic Magnetoresistance), GMR (Giant Magnetoresistance), TMR, or other types of magnetic elements. The magnetic focusing device is typically a magnetic ring made of soft magnetic material.

[0031] In this embodiment, the object under test is the object that generates the measured current (leakage current), such as a ground wire, or a combination of a live wire and a neutral wire. According to the right-hand screw rule, the measured current in the object under test generates a magnetic field.

[0032] like Figure 2 As shown, the measured current of the object passes through the middle of the magnetic focusing device, and the magnetic elements are placed in the air gap, numbering 2N, or N pairs. Figure 3 As shown, N pairs of magnetic elements are arranged in a linear array within the air gap. The two magnetic elements in each pair have opposite sensing directions. Specifically, when the direction of the measured current flow is in the horizontal plane, the sensing direction of one magnetic element in each pair is vertically upward, and the sensing direction of the other magnetic element is vertically downward. Magnetic elements 11 and 12 represent the first pair of magnetic elements, and magnetic elements N1 and N2 represent the Nth pair of magnetic elements. The two magnetic elements in each pair are arranged along the extension direction of the linear array.

[0033] The magnetic field at the air gap is an approximately uniform magnetic field. Therefore, the detected magnetic field is the same regardless of the distance between the magnetic element and the wire. For N pairs of magnetic elements, the extension direction of the linear array arranged along the linear array can intersect the current direction at any angle. In this embodiment, the extension direction of the linear array is perpendicular to the flow direction of the measured current (i.e., N pairs of magnetic elements are arranged radially along the air gap). In this state, the air gap size only needs to be one times the thickness of the magnetic element. That is, the air gap is small, the magnetic field strength is large, and the signal-to-noise ratio of the corresponding magnetic element will be relatively high. However, at other setting angles, the more magnetic elements there are, the larger the air gap will be, resulting in a smaller magnetic field strength at the air gap. In this case, the sensor sensitivity does not increase linearly with the increase of the number of magnetic elements.

[0034] (2) Signal conditioning module, used to acquire the sensing signal output by the sensing module and generate a conditioning signal.

[0035] The weak signal generated by the magnetic elements is vector-differentiated and amplified by the signal conditioning module before being connected to the signal acquisition module. The signal conditioning module achieves high-precision detection by summing the vector differences of the differential signals from each magnetic element. In this embodiment, the signal conditioning module includes an operational amplifier; the positive signal output terminals of all N pairs of magnetic elements whose sensitive direction is the first direction are connected to the non-inverting input terminal and the negative signal output terminals are connected to the inverting input terminal of the operational amplifier; the negative signal output terminals of all N pairs of magnetic elements whose sensitive direction is the second direction are connected to the non-inverting input terminal and the positive signal output terminals are connected to the inverting input terminal of the operational amplifier, wherein the first direction and the second direction are opposite directions.

[0036] like Figure 4As shown, taking the first direction as vertically upward and the second direction as vertically downward as an example, the positive signal V11+ of magnetic element 11 is connected to the non-inverting input terminal of the operational amplifier, and the negative signal V11- is connected to the inverting input terminal of the operational amplifier; the negative signal V12- of magnetic element 12 is connected to the non-inverting input terminal of the operational amplifier, and the positive signal V12+ is connected to the inverting input terminal of the operational amplifier. Similarly, the positive signal Vn1+ of magnetic element n1 is connected to the non-inverting input terminal of the operational amplifier, and the negative signal Vn1- is connected to the inverting input terminal of the operational amplifier; the negative signal Vn2- of magnetic element n2 is connected to the non-inverting input terminal of the operational amplifier, and the positive signal Vn2+ is connected to the inverting input terminal of the operational amplifier. When leakage current is present, the output signal of each group of magnetic elements follows the following relationship: ,but , The resistance value of the feedback resistor or matching resistor. This is the resistance value of the resistor connecting the signal terminal of the magnetic element and the input terminal of the operational amplifier. Compared with a single magnetic element, the magnetoelectric conversion efficiency is increased by 2N times, thereby improving the detection accuracy of the leakage current sensor.

[0037] For ease of understanding, this embodiment uses Figure 5 The layout of the magnetic elements and focusing device shown is further illustrated using an example. The focusing device is a C-shaped magnetic ring with a single air gap. Magnetic elements 11 and 12 are placed in the air gap, with the sensitive direction of magnetic element 11 facing upwards and the sensitive direction of magnetic element 12 facing downwards. According to the right-hand screw rule, the measured current generates an upward uniform magnetic field in the air gap. Therefore, magnetic elements 11 and 12 can detect magnetic induction intensities of equal magnitude but opposite direction. The magnetic elements used can be Hall effect elements, AMR, GMR, TMR, or other types of magnetic elements. The focusing ring can be C-shaped, U-shaped, E-shaped, or other shapes.

[0038] like Figure 6 As shown, the positive signal V11+ of magnetic component 11 is connected to the non-inverting input of the operational amplifier through resistor R1, and the negative signal V11- is connected to the inverting input of the operational amplifier through resistor R3; the positive signal V12+ of magnetic component 12 is connected to the inverting input of the operational amplifier through resistor R4, and the negative signal V12- is connected to the non-inverting input of the operational amplifier through resistor R2. R5 is the feedback resistor, and R6 is the matching resistor. To simplify calculations, the values ​​of all resistors in the circuit satisfy the following relationship: , Then the output signal It is evident that the magnetoelectric conversion efficiency is increased by 2 times compared to a single magnetic element, thereby improving the detection accuracy of the leakage current sensor.

[0039] (3) Signal acquisition module, used to acquire the conditioning signal generated by the signal conditioning module and obtain the measured current value based on the conditioning signal.

[0040] In this embodiment, the signal output by the signal conditioning module is acquired and analyzed by the ADC (Analog-to-Digital Converter) interface of the MCU (microcontroller) to calculate the magnitude of the measured current.

[0041] To support the normal operation of the sensor, the sensor also includes a power module, which supplies power to the magnetic components, signal conditioning module, and signal acquisition module.

[0042] The leakage current sensor of this invention uses common components and employs an array of multiple magnetic elements. By using a signal conditioning module to sum the differences between the magnetic elements, the detection accuracy of the leakage current sensor is improved. It is applicable to both open-loop and closed-loop schemes.

[0043] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0044] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A high-precision leakage current sensor based on arrayed magnetic elements, characterized in that, The high-precision leakage current sensor based on arrayed magnetic elements includes: a sensing module, a signal conditioning module, and a signal acquisition module, wherein: The sensing module is used to sense the magnetic field generated by the measured current in the object under test and output a sensing signal. The sensing module includes a magnetic focusing device and N pairs of magnetic elements. The object under test passes through the middle of the magnetic focusing device. The magnetic focusing device has an air gap. The N pairs of magnetic elements are arranged in the air gap and are arranged in a straight line array. The two magnetic elements in each pair of magnetic elements have opposite sensitive directions. The signal conditioning module is used to acquire the sensing signal output by the sensing module and generate a conditioning signal; The signal acquisition module is used to acquire the conditioning signal generated by the signal conditioning module and obtain the measured current value based on the conditioning signal.

2. The high-precision leakage current sensor based on arrayed magnetic elements according to claim 1, characterized in that, The magnetic focusing device is a magnetic ring made of soft magnetic material.

3. The high-precision leakage current sensor based on arrayed magnetic elements according to claim 1, characterized in that, Two magnetic elements in each pair are arranged along the extension direction of the linear array.

4. The high-precision leakage current sensor based on arrayed magnetic elements according to claim 1, characterized in that, The extension direction of the linear array is perpendicular to the flow direction of the measured current.

5. The high-precision leakage current sensor based on arrayed magnetic elements according to claim 1, characterized in that, When the direction of the current being measured is in the horizontal plane, the sensitive direction of one magnetic element in each pair of magnetic elements is vertically upward and the sensitive direction of the other magnetic element is vertically downward.

6. The high-precision leakage current sensor based on arrayed magnetic elements according to claim 1, characterized in that, The signal conditioning module includes an operational amplifier; The positive signal output terminals of all magnetic elements in the N pairs of magnetic elements whose sensitive direction is the first direction are connected to the non-inverting input terminal of the operational amplifier, and the negative signal output terminals are connected to the inverting input terminal of the operational amplifier. The negative signal output terminal of all magnetic elements in the N pairs of magnetic elements whose sensitive direction is the second direction is connected to the non-inverting input terminal of the operational amplifier, and the positive signal output terminal is connected to the inverting input terminal of the operational amplifier. The first direction and the second direction are opposite directions.

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