Current measuring device

Abstract

The present application provides a kind of current measuring device, current measuring device (1~3) includes: first sensor (SE1), detect the direct current magnetic field and low frequency alternating current magnetic field generated by the current (I) flowing through the measured conductor (MC);Hollow magnetic shielding member (12) has the cutout portion (CP2) for the measured conductor to pass through, internally accommodates first sensor;Fixing mechanism (13) is fixed with the measured conductor in the manner that the center of the measured conductor passing through the cutout portion of magnetic shielding member is at a predetermined reference distance (r) from first sensor;And first operation part (21), according to the detection result of first sensor, the current flowing through the measured conductor is obtained.

Description

Technical Field

[0001] This invention relates to a current measuring device. Background Technology

[0002] In the past, various current measuring devices have been developed that can measure the current flowing through the conductor being measured in a non-contact manner. Representative devices for such current measuring devices include, for example, current measuring devices based on the CT (Current Transformer) method, zero-flux current measuring devices, Rogowski current measuring devices, and Hall element current measuring devices.

[0003] For example, current measuring devices using the CT (Current Transmission) and zero-flux methods place a magnetic core with a coil wound around the conductor being measured. This cancels out the magnetic flux generated in the core by the current flowing through the conductor (primary side) and detects the current flowing through the coil (secondary side), thereby measuring the current flowing through the conductor. Furthermore, current measuring devices using the Rogowski method place a Rogowski coil (air-core coil) around the conductor being measured. The current flowing through the conductor is measured by detecting the voltage induced in the Rogowski coil by the linkage of the magnetic field generated by the alternating current flowing through the conductor with the Rogowski coil.

[0004] Patent Document 1 discloses an example of a zero-flux current measuring device. Furthermore, Patent Document 2 discloses a current measuring device using multiple magnetic sensors. Specifically, the current measuring device disclosed in Patent Document 2 arranges two magnetic sensors at different distances relative to the conductor being measured, determines the distance between the magnetic sensors and the conductor being measured based on the outputs of these magnetic sensors, and uses the determined distances to calculate the magnitude of the current flowing through the conductor being measured.

[0005] Existing technical documents

[0006] Patent Document 1: Japanese Patent Publication No. 2005-55300

[0007] Patent Document 2: Japanese Patent Publication No. 2011-164019

[0008] However, when measuring the current flowing through the conductor being measured, the accuracy of the current measurement will deteriorate if it is affected by a magnetic field other than the magnetic field generated by the current flowing through the conductor (external magnetic field). Furthermore, if the current flowing through the conductor can be measured non-contactly, the current measurement can be performed simply and effectively. Also, if it is small in size, it can be installed in a small space. Summary of the Invention

[0009] In view of the above, the object of the present invention is to provide a current measuring device that can measure the current flowing through the conductor being measured with high accuracy in a small and non-contact manner.

[0010] To address the aforementioned issues, one aspect of the current measuring device of the present invention is a current measuring device (1-3) for measuring the current (I) flowing through a conductor (MC) under test, comprising: a first sensor (SE1) for detecting a DC magnetic field and a low-frequency AC magnetic field generated by the current flowing through the conductor under test; a hollow magnetic shielding member (12) having a cutout (CP2) through which the conductor under test passes, and housing the first sensor inside; a fixing mechanism (13) for fixing the conductor under test such that the distance between the center of the conductor under test passing through the cutout of the magnetic shielding member and the first sensor is a predetermined reference distance (r); and a first calculation unit (21) for calculating the current flowing through the conductor under test based on the detection result of the first sensor.

[0011] Furthermore, one embodiment of the current measuring device of the present invention includes: a sensor head (10, 10A, 10B) having the first sensor, the magnetic shielding member and the fixing mechanism; and a circuit section (20, 20A) having the first arithmetic section.

[0012] Furthermore, in one embodiment of the current measuring device of the present invention, the sensor head further includes a second sensor (SE2, SE3), which detects an alternating magnetic field from low frequency to high frequency generated by the current flowing through the conductor being measured. The circuit section further includes: a second calculation unit (23) that calculates the current flowing through the conductor being measured based on the detection result of the second sensor; and a synthesis unit (24) that synthesizes the calculation result of the first calculation unit and the calculation result of the second calculation unit.

[0013] Furthermore, in one embodiment of the current measuring device of the present invention, the second sensor includes a Rogowski sensor (SE2) which is wound around the conductor being measured through the cut portion of the magnetic shielding member.

[0014] Alternatively, in one embodiment of the current measuring device of the invention, the second sensor includes a coil (SE3) housed inside the magnetic shielding member.

[0015] In one embodiment of the current measuring device of the present invention, the coil is arranged inside the magnetic shielding member such that its magnetic induction direction is tangential to the conductor being measured passing through the cutout.

[0016] Furthermore, in one embodiment of the current measuring device of the present invention, a beam member (BM) is formed inside the magnetic shielding member between the cutout and the first sensor.

[0017] Furthermore, in one embodiment of the current measuring device of the present invention, the first sensor is disposed inside the magnetic shielding member such that its magnetic sensing direction is tangential to the conductor being measured passing through the cut-out portion.

[0018] Furthermore, in one embodiment of the current measuring device of the present invention, the thickness of the magnetic shielding member is set such that even if the maximum current that can be measured by the current measuring device flows through the conductor being measured, magnetic saturation will not occur.

[0019] Furthermore, in one aspect of the current measuring device of the present invention, the first arithmetic unit calculates the current flowing through the conductor being measured by multiplying the detection result of the first sensor with a constant uniquely determined based on the reference distance.

[0020] Furthermore, one aspect of the current measuring device of the present invention further includes an output unit that outputs the measurement result of the current flowing through the measured conductor, which is obtained by the first calculation unit, to the outside.

[0021] Furthermore, in one embodiment of the current measuring device of the present invention, the circuit section is separate from the sensor head and connected to the sensor head via a cable.

[0022] Furthermore, in one embodiment of the current measuring device of the present invention, the synthesis unit includes: a low-pass filter (24a) that removes high-frequency components from the calculation result of the first arithmetic unit and allows low-frequency components to pass through; a high-pass filter (24b) that removes low-frequency components from the calculation result of the second arithmetic unit and allows high-frequency components to pass through; a signal level adjustment unit (24c) that adjusts the level of the signal output from the low-pass filter; and an adder (24d) that adds the signal whose level has been adjusted by the signal level adjustment unit to the signal output from the high-pass filter.

[0023] Furthermore, in one embodiment of the current measuring device of the present invention, the thickness of the beam member is set to be equal to or greater than the thickness of the magnetic shielding member, so that even if the maximum current that can be measured by the current measuring device flows through the conductor being measured, magnetic saturation will not occur.

[0024] According to the present invention, it has the effect of being able to measure the current flowing through the conductor being measured with high precision in a small and non-contact manner. Attached Figure Description

[0025] Figure 1 This is a perspective view of the current measuring device according to the first embodiment of the present invention.

[0026] Figure 2 This is a perspective view of the sensor head of the current measuring device according to the first embodiment of the present invention.

[0027] Figure 3A This is a diagram showing the magnetic shielding member included in the current measuring device according to the first embodiment of the present invention.

[0028] Figure 3B This is a diagram showing the magnetic shielding member included in the current measuring device according to the first embodiment of the present invention.

[0029] Figure 4 This is a graph showing the simulation results of the SN ratio in the first embodiment of the present invention.

[0030] Figure 5 This is a block diagram showing the essential components of the current measuring device according to the first embodiment of the present invention.

[0031] Figure 6 This is an external view of the current measuring device according to the second embodiment of the present invention.

[0032] Figure 7 This is a block diagram showing the essential components of the current measuring device according to the second embodiment of the present invention.

[0033] Figure 8A This diagram illustrates the processing performed by the synthesis unit of the circuit section in the second embodiment of the present invention.

[0034] Figure 8B This diagram illustrates the processing performed by the synthesis unit of the circuit section in the second embodiment of the present invention.

[0035] Figure 8C This diagram illustrates the processing performed by the synthesis unit of the circuit section in the second embodiment of the present invention.

[0036] Figure 9 This is an external view of the current measuring device according to the third embodiment of the present invention.

[0037] Figure 10 This is a cross-sectional view of the magnetic shielding of the sensor head of the current measuring device according to the third embodiment of the present invention.

[0038] Figure 11A This is a diagram showing the structure of the magnetic shielding member provided on the sensor head of the current measuring device according to the fourth embodiment of the present invention.

[0039] Figure 11B This is a diagram showing the structure of the magnetic shielding member provided on the sensor head of the current measuring device according to the fourth embodiment of the present invention.

[0040] Figure 11C This is a diagram showing the structure of the magnetic shielding member provided on the sensor head of the current measuring device according to the fourth embodiment of the present invention.

[0041] Figure 11D This is a diagram showing the structure of the magnetic shielding member provided on the sensor head of the current measuring device according to the fourth embodiment of the present invention.

[0042] Figure 12A This is a graph showing the simulation results of the magnetic flux density distribution in the fourth embodiment of the present invention.

[0043] Figure 12B This is a graph showing the simulation results of the magnetic flux density distribution in the fourth embodiment of the present invention.

[0044] Figure 13 This is a graph showing the simulation results of the SN ratio in the fourth embodiment of the present invention. Detailed Implementation

[0045] Hereinafter, with reference to the accompanying drawings, a current measuring device according to embodiments of the present invention will be described in detail. First, a general overview of embodiments of the present invention will be given, followed by a detailed description of each embodiment.

[0046] [summary]

[0047] The embodiments of the present invention enable high-precision measurement of current flowing through a conductor in a compact and non-contact manner. Specifically, it can be set up in a small space during current measurement, and can measure DC current and AC current up to tens of MHz in a non-contact manner with high precision.

[0048] In recent years, the development of hybrid vehicles (HV) and electric vehicles (EV) has created a demand for measuring large currents flowing between the battery and power unit, and between the converter and inverter. Furthermore, the pursuit of short-duration acceleration has led to higher current limits, resulting in thicker wiring. On the other hand, efforts to expand passenger space and reduce weight are driving space-saving, integrated, and miniaturized equipment. Consequently, dense wiring and connections make it difficult to secure space for current sensors. Under these circumstances, there is a need for current measurement devices that can accurately measure DC and AC currents flowing through wiring with limited surrounding space in a non-contact manner.

[0049] However, the zero-flux current measuring device disclosed in Patent Document 1 requires a magnetic core of a certain size (e.g., about 20 cm in diameter) to be placed around the conductor being measured, making it difficult to install in confined spaces. Furthermore, the Rogowski-based current measuring device detects the voltage induced in the Rogowski coil, thus it cannot theoretically measure direct current. Additionally, in the low-frequency region, the output signal is weak and phase-shifted, resulting in poor measurement accuracy. Moreover, the current measuring devices disclosed in Patent Documents 1 and 2 are affected by magnetic fields other than the magnetic field generated by the current flowing through the conductor being measured (external magnetic field), thus leading to poor measurement accuracy.

[0050] In embodiments of the present invention, the following components are provided: a first sensor for detecting a DC magnetic field and a low-frequency AC magnetic field generated by the current flowing through the conductor being measured; a hollow magnetic shielding member having a cutout through which the conductor being measured passes, and housing the first sensor inside; a fixing mechanism for fixing the conductor being measured such that the distance between the conductor being measured passing through the cutout of the magnetic shielding member and the first sensor is a predetermined reference distance; and a first arithmetic unit for calculating the current flowing through the conductor being measured based on the detection result of the first sensor. Thus, the current flowing through the conductor being measured can be measured with high precision in a compact and non-contact manner.

[0051] [First Implementation Method]

[0052] <Structure of Current Measuring Device>

[0053] Figure 1 This is a perspective view of the current measuring device according to the first embodiment of the present invention. Figure 1 As shown, the current measuring device 1 of this embodiment includes a sensor head 10 and a circuit section 20 connected by a cable CB, and measures the current I flowing through the measured conductor MC in a non-contact manner. Furthermore, the measured conductor MC can be any conductor such as a lead or busbar of a power semiconductor. For simplicity, the measured conductor MC will be described below as a cylindrical conductor.

[0054] Additionally, in the following description, the positional relationships of each component will be explained with reference to the XYZ orthogonal coordinate system set in the diagram, as needed. Figure 1 In the XYZ orthogonal coordinate system shown, the X-axis is set to the direction of the long side of the conductor MC being measured (the direction of current I), the Y-axis is set to the horizontal direction, and the Z-axis is set to the vertical direction. However, for ease of explanation, the origin of the XYZ orthogonal coordinate system shown in each figure is not fixed and its position is changed appropriately for each figure.

[0055] The sensor head 10 is a component for measuring the current I flowing through the conductor MC being measured in a non-contact manner. The sensor head 10 can be described as a probe for measuring the current I flowing through the conductor MC being measured in a non-contact manner. Furthermore, in order to be able to measure the current I even when the space around the conductor MC is limited, the sensor head 10 is preferably made as small as possible.

[0056] like Figure 1 As shown, when measuring the current I flowing through the conductor MC, the sensor head 10 is fixedly configured relative to the conductor MC. That is, the sensor head 10 is in physical contact with the conductor MC. However, the sensor head 10 is electrically insulated from the conductor MC, so the current I flowing through the conductor MC does not flow into the sensor head 10. Therefore, the sensor head 10 can be considered as a component for measuring the current I flowing through the conductor MC in a non-contact manner.

[0057] Figure 2 This is a perspective view of the sensor head included in the current measuring device according to the first embodiment of the present invention. Figure 2 As shown, the sensor head 10 includes a housing 11, a magnetic shielding member 12, and a fixing mechanism 13. The housing 11 is a hollow cuboid-shaped component formed by combining a first housing 11a and a second housing 11b, and has a cutout CP1 formed on the -Z side. The housing 11 (the first housing 11a and the second housing 11b) is made of a material that will not affect the magnetic field generated by the current I (e.g., a non-magnetic material such as resin). The housing 11 internally houses the magnetic shielding member 12 and the fixing mechanism 13.

[0058] A notch CP1 is formed on the -Z side of the housing 11, extending from the end on the +X side to the end on the -X side. This notch CP1 allows a portion of the conductor MC to be measured to be disposed inside the housing 11. Additionally, Figure 2 The illustrated cutout CP1 has an approximately inverted U-shaped shape when viewed in the X-axis direction. The cutout CP1 is formed from the +X side end of the housing 11 to the -X side end, thus allowing a portion of the conductor MC to be measured to be easily disposed inside the housing 11. That is, by simply arranging the sensor head 10 with the cutout CP1 parallel to the conductor MC, facing the conductor MC, and moving the sensor head 10 toward the conductor MC, a portion of the conductor MC to be measured can be easily disposed inside the housing 11.

[0059] Figures 3A-3B This diagram illustrates the magnetic shielding member included in the current measuring device according to the first embodiment of the present invention. Additionally, Figure 3A This is a perspective view of the magnetic shielding component 12. Figure 3B It is along Figure 3A The cross-section of line AA in the view. For example... Figure 3A As shown, the magnetic shielding member 12 is composed of a first shielding member 12a and a second shielding member 12b, and is a hollow cuboid-shaped member with a cutout CP2 formed on the -Z side. The magnetic shielding member 12 (the first shielding member 12a and the second shielding member 12b) is formed of a soft magnetic material (such as permalloy) with low holding force and high magnetic permeability. This magnetic shielding member 12 is provided to improve the measurement accuracy of the current I by shielding it from magnetic fields (external magnetic fields) other than the magnetic field (signal magnetic field) generated by the current I flowing through the conductor being measured MC.

[0060] The cutout CP2 is formed on the -Z side of the magnetic shield 12, extending from the end on the +X side to the end on the -X side. This cutout CP2 is provided so that a portion of the conductor MC being measured is disposed inside the magnetic shield 12 when measuring the current I flowing through it. In other words, the cutout CP2 is provided to house a portion of the conductor MC being measured inside the magnetic shield 12, which shields against external magnetic fields. The cutout CP2 is configured such that its shape and size, when viewed in the X-axis direction, are the same (or approximately the same) as the cutout CP1 formed in the housing 11. The magnetic shield 12 is housed within the housing 11 such that the cutout CP2 overlaps with the cutout CP1 of the housing 11 when viewed in the X-axis direction.

[0061] The thickness of the magnetic shield 12 is set in such a way that magnetic saturation will not occur even if the maximum current (upper limit current: for example, an effective value of 1000 [A]) that can be measured by the current measuring device 1 flows through the conductor MC being measured. The magnetic shield 12 can be made, for example, using a soft magnetic material with a thickness that does not cause the aforementioned magnetic saturation, or it can be made using a laminate of multiple thin soft magnetic materials stacked together to form a thickness that does not cause the aforementioned magnetic saturation. Alternatively, the magnetic shield 12 can also be made by casting or machining to achieve a thickness that does not cause the aforementioned magnetic saturation.

[0062] like Figure 3B As shown, the magnetic shield 12 internally houses the magnetic sensor SE1 (first sensor). The magnetic sensor SE1 is placed inside the magnetic shield 12 to improve the measurement accuracy of the current I by detecting the signal magnetic field in a state where the influence of external magnetic fields is eliminated. The magnetic sensor SE1 detects both the DC magnetic field generated by the current I flowing through the conductor MC being measured and the low-frequency (e.g., up to several kHz) AC magnetic field. For example, when the current I flowing through the conductor MC being measured is a DC current, it detects... Figure 3B The magnetic field H shown is illustrated.

[0063] Since the magnetic sensor SE1 is used to measure the current I flowing through the conductor MC being measured, it requires responsiveness. For example, the delay time of the magnetic sensor SE1 is preferably less than 1 msec. The magnetic sensor SE1 can be an analog sensor or a digital sensor, provided the response speed is fast enough. The detection axis of the magnetic sensor SE1 is preferably three or more axes, but it can also be one or two axes. When the magnetic sensor SE1 has two or fewer detection axes, the magnetic sensor SE1 is configured within the magnetic shield 12 such that when the sensor head 10 is fixed to the conductor MC being measured by the fixing mechanism 13, the detection axis (magnetic sensing direction) aligns with the direction of the magnetic field generated by the current I (the tangential direction of the conductor MC being measured). By configuring the magnetic sensor SE1 in this manner, the influence of the external magnetic field flowing into the magnetic shield 12 from the cutout CP2 on the magnetic sensor SE1 can be reduced.

[0064] To ensure the measurement accuracy of the current measuring device 1, the magnetic sensor SE1 is made with low noise. For example, the noise component in the detection result of the magnetic sensor SE1 is approximately 0.1% of the measurement range of the current measuring device 1. Furthermore, the magnetic sensor SE1 can be, for example, a Hall element or a magnetoresistive element.

[0065] The magnetic sensor SE1 is positioned within the magnetic shield 12 at a position where the ratio of the intensity of the signal magnetic field to the external magnetic field (signal-to-noise ratio) is approximately 100 to 1 or higher. Figure 4 This is a graph showing the simulation results of the SN ratio in the first embodiment of the present invention. Additionally, in Figure 4 In the graph shown, the horizontal axis represents the distance from the center of the measured conductor MC in the Z direction, and the vertical axis represents the SN ratio (logarithm).

[0066] In addition, like three-phase communication, Figure 4 The simulation results shown assume that other conductors exist adjacent to the measured conductor MC, and a current of equal magnitude flows through these other conductors as the current I flowing through the measured conductor MC. Figure 4 In the diagram, the curves represented by solid lines are the simulation results when the magnetic shielding element 12 is provided, while the curves represented by dashed lines are the simulation results when the magnetic shielding element 12 is omitted. Furthermore, as... Figure 4 As shown, in the simulation, the radius of the conductor MC to be measured is set to 5 [mm].

[0067] Reference Figure 4 It can be seen that the SN ratio is much higher when the magnetic shield 12 is provided than when it is omitted. Furthermore, the SN ratio gradually decreases as the distance from the measured conductor MC (the distance from the center of the measured conductor MC) increases. Figure 4In the simulation results shown, if the distance from the center of the conductor MC being measured is within 5 to 8 mm, the SN ratio is 100 to 1 or higher. The magnetic sensor SE1 is, for example, positioned within the magnetic shield 12 at a distance of 8 mm in the Z direction from the center of the conductor MC being measured.

[0068] The fixing mechanism 13 is a mechanism for fixing the sensor head 10 relative to the conductor being measured, MC, such as... Figure 2 The device shown is positioned on the +X side of the magnetic shield 12. Regardless of the diameter of the conductor MC being measured, the fixing mechanism 13 fixes the conductor MC so that the distance between the center of the conductor MC and the magnetic sensor SE1 is a predetermined reference distance r. For example, the fixing mechanism 13 fixes the conductor MC so that the distance between the center of the conductor MC and the magnetic sensor SE1 is 8 mm.

[0069] The distance between the magnetic sensor SE1 and the conductor MC being measured is set to the aforementioned reference distance r by the fixing mechanism 13 so that the current I flowing through the conductor MC can be determined using only the detection result of the magnetic sensor SE1. That is, the current I flowing through the conductor MC is determined by multiplying the detection result of the magnetic sensor SE1 by a constant uniquely determined according to the reference distance r. If the distance between the magnetic sensor SE1 and the conductor MC being measured is set to the reference distance r by the fixing mechanism 13, then the current I flowing through the conductor MC can be determined using only the measurement result of the magnetic sensor SE1.

[0070] like Figure 2 As shown, the fixing mechanism 13 is a screw mechanism with guides, including a pair of guide members 13a, a pair of fixing arms 13b, left and right screws 13c, and a knob member 13d. Furthermore, the components constituting the fixing mechanism 13 (a pair of guide members 13a, a pair of fixing arms 13b, left and right screws 13c, and knob member 13d) are formed of, for example, non-magnetic materials such as resin.

[0071] The guide member 13a is a cylindrical member used to guide the fixing arm 13b in the Y direction. A pair of guide members 13a are spaced apart in the Z direction and arranged with their long sides along the Y direction. The fixing arm 13b is a quadrangular prism-shaped member, forming a V-groove-shaped gripping portion GR, a guide hole through which the guide member 13a passes, and a threaded hole through which the left and right screws 13c pass. A pair of fixing arms 13b are arranged with the gripping portion GR facing each other, the guide member 13a passes through the guide hole, and the left and right screws 13c are threadedly connected to the threaded hole.

[0072] The left and right screws 13c are, for example, cylindrical screws with a right screw extending to the right (+Y side) from the center and a left screw extending to the left (-Y side) from the center. The knob member 13d is a cylindrical member mounted on one end (the +Y side end) of the left and right screws 13c, allowing the left and right screws 13c to rotate about an axis via user operation. If the left and right screws 13c are rotated about the axis in one direction via the knob member 13d, a pair of fixing arms 13b move in the Y direction in a separated manner. Conversely, if the left and right screws 13c are rotated about the axis in the other direction via the knob member 13d, a pair of fixing arms 13b move in the Y direction in a closer manner.

[0073] Here, with the conductor MC to be measured fixed to the sensor head 10, the conductor MC is held by the V-groove-shaped gripping portions GR formed in a pair of fixing arms 13b. When the conductor MC is held by the gripping portions GR, its position in the Y and Z directions is restricted, and the Y and Z directions of the center of the conductor MC become the same regardless of its diameter. Thus, regardless of the diameter of the conductor MC, the conductor MC is fixed to the sensor head 10 such that the distance between the center of the conductor MC and the magnetic sensor SE1 is a predetermined reference distance r.

[0074] Figure 1 The circuit section 20 shown measures the current I flowing through the conductor MC being measured, based on the detection result output from the sensor head 10 (the detection result of the magnetic sensor SE1). The circuit section 20 outputs or displays the measurement result of the current I to the outside. Any cable can be used as the cable CB connecting the sensor head 10 and the circuit section 20, but a flexible cable is preferred. Furthermore, a cable that is easy to lay out is preferred, and a cable that is difficult to break is also preferred.

[0075] Figure 5 This is a block diagram showing the essential components of the current measuring device according to the first embodiment of the present invention. Additionally, in Figure 5 In the middle, to and Figure 1 The modules shown are labeled with the same reference numerals as those in the attached drawings. The following will primarily refer to... Figure 5 The internal structure of the circuit section 20 will be explained in detail. For example... Figure 5 As shown, the circuit section 20 includes an arithmetic section 21 (first arithmetic section) and an output section 22.

[0076] The arithmetic unit 21 calculates the current I flowing through the conductor MC to be measured based on the detection result of the magnetic sensor SE1. As described above, the magnetic sensor SE1 detects a DC magnetic field and a low-frequency AC magnetic field; therefore, the current I calculated by the arithmetic unit 21 contains both DC and low-frequency components. The arithmetic unit 21 stores distance information representing the aforementioned reference distance r in advance. The arithmetic unit 21 calculates the current I flowing through the conductor MC to be measured by multiplying the detection result (magnetic field H) of the magnetic sensor SE1 with a constant uniquely determined based on the reference distance r.

[0077] The output unit 22 outputs the measurement result of the current I calculated by the calculation unit 21 to the outside. In addition, the output unit 22 may include, for example, an output terminal that outputs a signal representing the measurement result of the current I to the outside, or it may include a display device (e.g., a liquid crystal display device) that displays the measurement result of the current I to the outside.

[0078] Here, as Figure 1 As shown, the circuit section 20 is separate from the sensor head 10 and connected to the sensor head 10 via cable CB. This structure allows for the separation of the magnetic field detection function (magnetic sensor SE1) from the computational function (computation section 21 and output section 22). This simplifies the arrangement of the sensor head 10, making it easier to place in confined spaces. Furthermore, it avoids various problems (such as temperature characteristics and insulation resistance) that arise when the computational function is located within the sensor head 10, thereby expanding the applications of the current measuring device 1.

[0079] <Operation of the current measuring device>

[0080] Next, the operation of the current measuring device 1 when measuring the current I flowing through the conductor MC will be explained. First, the user of the current measuring device 1, in order to measure the current I flowing through the conductor MC, as follows... Figure 1 As shown, the operation of fixing the sensor head 10 to the conductor MC being measured is performed.

[0081] Specifically, the user of the current measuring device 1 performs the following operations: Positioning the sensor head 10 so that the cut CP1 is parallel to the conductor MC being measured, with the cut CP1 facing the conductor MC, and then moving the sensor head 10 toward the conductor MC. Thus, a portion of the conductor MC is positioned inside the housing 11 of the sensor head 10. The user of the current measuring device 1 then operates the knob member 13d of the fixing mechanism 13, moving the pair of fixing arms 13b toward each other, so that the conductor MC is clamped by the gripping portion GR of the pair of fixing arms 13b.

[0082] If the above operations are performed, the conductor MC to be measured is fixed to the sensor head 10 by the fixing mechanism 13, and the conductor MC to be measured is in a state where it passes through the cutout CP2 of the magnetic shield 12 provided on the sensor head 10. In addition, in this state, the distance between the magnetic sensor SE1 and the conductor MC to be measured passing through the cutout CP2 of the magnetic shield 12 is set to a reference distance r.

[0083] If the above operations are completed, the process of measuring the current I flowing through the conductor MC is performed. Specifically, firstly, the magnetic field formed by the current I flowing through the conductor MC is detected by the magnetic sensor SE1. Next, the processing unit 21 calculates the current I flowing through the conductor MC based on the detection result of the magnetic sensor SE1. Specifically, the processing unit 21 performs the following processing: by calculating the product of a constant stored in itself (a constant uniquely determined based on the reference distance r) and the detection result (magnetic field H) of the magnetic sensor SE1, the current I (DC and low-frequency components) flowing through the conductor MC is calculated. If the above processing is completed, the output unit 22 outputs information representing the current I calculated by the processing unit 21. The above processing is performed continuously or repeatedly at a certain period (e.g., 1 second).

[0084] As described above, this embodiment includes: a hollow magnetic shield 12 having a cutout CP2 through which the conductor MC to be measured passes, and a magnetic sensor SE1 housed inside; a fixing mechanism 13 that fixes the conductor MC to be measured such that the distance between the center of the conductor MC to be measured and the magnetic shield 12 is a predetermined reference distance r; and a calculation unit 21 that calculates the current flowing through the conductor MC to be measured based on the detection result of the magnetic sensor SE1. Therefore, in this embodiment, the current I (DC and low-frequency components) flowing through the conductor MC to be measured can be measured with high accuracy in a small and non-contact manner.

[0085] [Second Implementation]

[0086] <Structure of Current Measuring Device>

[0087] Figure 6 This is an external view of the current measuring device according to the second embodiment of the present invention. Figure 6 As shown, the current measuring device 2 of this embodiment includes a sensor head 10A and a circuit section 20A connected by a cable CB, and measures the current I flowing through the measured conductor MC in a non-contact manner. Furthermore, the measured conductor MC can be any conductor such as a power semiconductor pin or busbar; however, in this embodiment, for simplicity, the measured conductor MC is a cylindrical conductor.

[0088] The sensor head 10A is a structure in which a Rogowski sensor SE2 (second sensor) is added to the sensor head 10 of the first embodiment. The current measuring device 1 of the first embodiment measures the DC and low-frequency components of the current I flowing through the conductor MC being measured. In contrast, the current measuring device 2 of this embodiment can measure not only the DC and low-frequency components of the current I flowing through the conductor MC being measured, but also components ranging from low to high frequencies.

[0089] The Rogowski sensor SE2 detects alternating magnetic fields ranging from low frequencies (e.g., several kHz) to high frequencies (e.g., tens of MHz) generated by the current I flowing through the conductor MC being measured. The Rogowski sensor SE2 is a sensor using a Rogowski coil (air-core coil) configured to surround the conductor MC being measured. Furthermore, to facilitate easy placement around the conductor MC, one end E1 of the Rogowski sensor SE2 is configured to be detachable from the sensor head 10A.

[0090] The circuit section 20A measures the current I flowing through the conductor MC being measured, based on the detection results output from the sensor head 10A (the detection results of the magnetic sensor SE1 and the Rogowski sensor SE2). The circuit section 20A outputs or displays the measurement result of the current I to the outside. The cable CB is the same as in the first embodiment, preferably a flexible cable; furthermore, a cable that is easy to lay out is preferred, and a cable that is difficult to break is also preferred.

[0091] Figure 7 This is a block diagram showing the essential components of the current measuring device according to the second embodiment of the present invention. Furthermore, in Figure 7 In the middle, to and Figure 5 The modules shown are labeled with the same reference numerals as those in the attached drawings. The following will primarily refer to... Figure 7 The internal structure of the circuit section 20A will be explained in detail. For example... Figure 7 As shown, in addition to the arithmetic unit 21 and the output unit 22, the circuit unit 20A also includes an arithmetic unit 23 (second arithmetic unit) and a synthesis unit 24.

[0092] The arithmetic unit 23 calculates the current I flowing through the measured conductor MC based on the detection result of the Rogowski sensor SE2. As mentioned above, the Rogowski sensor SE2 detects alternating magnetic fields from low to high frequencies; therefore, the current I calculated by the arithmetic unit 23 represents the low-frequency to high-frequency components. The detection result of the Rogowski sensor SE2 represents the voltage induced in the Rogowski coil by the alternating magnetic field generated around the current I (alternating current) flowing through the measured conductor MC. The arithmetic unit 23 calculates the current I flowing through the measured conductor MC by performing a calculation that converts the detection result (voltage) of the Rogowski sensor SE2 into a current value.

[0093] The synthesis unit 24 synthesizes the results of the calculations by the arithmetic unit 21 and the arithmetic unit 23. Specifically, the synthesis unit 24 includes a low-pass filter 24a, a high-pass filter 24b, a signal level adjustment unit 24c, and an adder 24d. The low-pass filter 24a removes high-frequency components from the results of the arithmetic unit 21 and allows low-frequency components to pass through, resulting in a signal with the desired frequency characteristics suitable for the synthesis process described later. The high-pass filter 24b removes low-frequency components from the results of the arithmetic unit 23 and allows high-frequency components to pass through, resulting in a signal with the desired frequency characteristics suitable for the synthesis process described later.

[0094] The signal level adjustment unit 24c adjusts the level of the signal output from the low-pass filter 24a. For example, when a DC current and an AC current with the same effective value flow through the conductor MC being measured, the signal level adjustment unit 24c adjusts the signal level of the signal output from the low-pass filter 24a to be the same as the signal level of the signal output from the high-pass filter 24b. A variable resistor can be used, for example, as this signal level adjustment unit 24c.

[0095] Furthermore, this embodiment includes a signal level adjustment unit 24c that adjusts only the level of the signal output from the low-pass filter 24a, but the present invention is not limited thereto. For example, a signal level adjustment unit that adjusts the level of the signal output from the high-pass filter 24b may be provided instead of the signal level adjustment unit 24c, or may be provided in addition to the signal level adjustment unit 24c. Alternatively, a signal level adjustment unit capable of adjusting the levels of the first signal and the second signal may also be provided.

[0096] The adder 24d adds the signal whose signal level has been adjusted by the signal level adjustment unit 24c to the signal output from the high-pass filter 24b. The signal whose signal level has been adjusted by the signal level adjustment unit 24c is a signal representing the DC and low-frequency components of the current I. The signal output from the high-pass filter 24b is a signal representing the high-frequency components of the current I. Therefore, by adding them together, a signal representing the DC and AC components up to the high frequency can be obtained.

[0097] Figures 8A to 8C This diagram illustrates the process performed by the synthesis unit of the circuit section in the second embodiment of the present invention. Additionally, Figure 8A This is a diagram illustrating an example of the filter characteristics of low-pass filter 24a. Figure 8B This is a diagram illustrating an example of the filter characteristics of a high-pass filter 24b. Figure 8C This is a diagram illustrating an example of the frequency characteristics of the synthesizer.

[0098] like Figure 8A , Figure 8BAs shown, both the low-pass filter 24a and the high-pass filter 24b have a cutoff frequency of fc. That is, the low-pass filter 24a has the following characteristics: it approximately removes frequency components higher than the cutoff frequency fc, and allows frequency components lower than the cutoff frequency fc to pass through. Similarly, the high-pass filter 24b has the following characteristics: it approximately removes frequency components lower than the cutoff frequency fc, and allows frequency components higher than the cutoff frequency fc to pass through.

[0099] like Figure 8C As shown, the frequency characteristics of the synthesis unit 24 can be described as follows: Figure 8A The characteristics shown and Figure 8B The characteristics shown are synthesized into a flat characteristic at and around the cutoff frequency fc. That is, the frequency characteristic of the synthesis unit 24 becomes a flat characteristic of the effective value of the alternating current from low frequency to high frequency, and the effective value of the direct current (current value) becomes a value that is approximately the same as the effective value of the flat alternating current in this frequency characteristic.

[0100] Here, in order to make the signal synthesized by the synthesis unit 24 (the measurement result of current I) a signal that reproduces the current I flowing through the measured conductor MC, the delay time t of the magnetic sensor SE1 is... delay The relationship with the cutoff frequency fc mentioned above needs to satisfy t delay The relationship is <(1 / fc)×(1 / 100). Additionally, the aforementioned delay time t... delay It is the time required from the change in current flowing through the conductor MC being measured (i.e., from the change in the magnetic field applied to the magnetic sensor SE1) to the output of the detection result by the magnetic sensor SE1.

[0101] The output unit 22 outputs the signal (measurement result of current I) synthesized by the synthesis unit 24 to the outside. In addition, similar to the first embodiment, the output unit 22 may include, for example, an output terminal that outputs the signal representing the measurement result of current I to the outside, or a display device (e.g., a liquid crystal display device) that displays the measurement result of current I to the outside.

[0102] Here, as Figure 7 As shown, the circuit section 20A is separate from the sensor head 10A and connected to the sensor head 10A via cable CB. This structure allows for the separation of the magnetic field detection function (magnetic sensor SE1, Rogowski sensor SE2) from the computational function (computation units 21, 23, synthesis unit 24, and output unit 22). This simplifies the arrangement of the sensor head 10A, making it easier to place in confined spaces. Furthermore, it avoids various problems (such as temperature characteristics and insulation resistance) that arise when the computational function is located within the sensor head 10A, thereby expanding the applications of the current measuring device 2.

[0103] <Operation of the current measuring device>

[0104] Next, the operation of measuring the current I flowing through the conductor MC using the current measuring device 2 will be explained. First, in order to measure the current I flowing through the conductor MC, the user of the current measuring device 2 performs the operation of fixing the sensor head 10A to the conductor MC using the fixing mechanism 13, similar to the first embodiment. If the above operation is performed, the conductor MC is fixed to the sensor head 10A by the fixing mechanism 13, just like in the first embodiment, and the distance between the magnetic sensor SE1 and the conductor MC is set to the reference distance r.

[0105] In addition, such as Figure 6 As shown, the user of the current measuring device 2 configures the Rogowski sensor SE2 to surround the conductor MC being measured. At this time, the user of the current measuring device 2 performs the following operations as needed: detaching one end E1 of the Rogowski sensor SE2 from the sensor head 10A and fixing the sensor head 10A to the conductor MC being measured. Alternatively, after the operation is completed, the Rogowski sensor SE2 can be configured in the above-described state, and then one end E1 of the Rogowski sensor SE2 can be installed back onto the sensor head 10A.

[0106] If the above operations are completed, the process of measuring the current I flowing through the conductor MC to be measured is performed. Specifically, firstly, the following process is performed: the magnetic field formed by the current I flowing through the conductor MC to be measured is detected by the magnetic sensor SE1 and the Rogowski sensor SE2. Next, the calculation units 21 and 23 perform the following process: the current I flowing through the conductor MC to be measured is calculated based on the detection results of the magnetic sensor SE1 and the Rogowski sensor SE2. Specifically, the following process is performed in the calculation unit 21: the current I flowing through the conductor MC to be measured (DC and low-frequency components) is calculated by multiplying a constant stored in itself (a constant uniquely determined according to the reference distance r) with the detection result (magnetic field H) of the magnetic sensor SE1. Furthermore, the following process is performed in the calculation unit 23: the current I flowing through the conductor MC to be measured (from low frequency to high frequency components) is calculated by converting the detection result (voltage) of the Rogowski sensor SE2 into a current value.

[0107] Next, the synthesis unit 24 performs a synthesis process on the currents calculated by the arithmetic units 21 and 23. Specifically, first, the calculation result of the arithmetic unit 21 is input to the low-pass filter 24a to remove high-frequency components, and the calculation result of the arithmetic unit 23 is input to the high-pass filter 24b to remove low-frequency components. Next, the signal level adjustment unit 24c performs the following process: adjusting the levels of the signal output from the low-pass filter 24a (the low-frequency components that have passed through the low-pass filter 24a) and the signal output from the high-pass filter 24b (the high-frequency components that have passed through the high-pass filter 24b).

[0108] Furthermore, the addition unit 24d adds the signal whose signal level has been adjusted by the signal level adjustment unit 24c to the signal output from the high-pass filter 24b. This synthesizes the current calculated by the arithmetic units 21 and 23. Once the above processing is complete, the current synthesized by the synthesis unit 24 is output from the output unit 22. This processing is performed continuously or repeatedly at a certain period (e.g., 1 second).

[0109] As described above, this embodiment includes: a magnetic sensor SE1 housed in a magnetic shield 12, which detects a DC magnetic field and a low-frequency AC magnetic field generated by the current flowing through the conductor MC being measured; and a Rogowski sensor SE2, which detects AC magnetic fields ranging from low to high frequencies generated by the current flowing through the conductor MC being measured. Furthermore, based on the detection results of the magnetic sensor SE1, the current flowing through the conductor MC being measured (DC current and low-frequency AC current) is calculated, and based on the detection results of the Rogowski sensor SE2, the current flowing through the conductor MC being measured (from low to high frequency) is calculated, and the various calculation results are combined. Therefore, in this embodiment, the current I flowing through the conductor MC being measured (DC and low-frequency components, as well as components ranging from low to high frequency) can be measured with high precision in a compact and non-contact manner.

[0110] [Third Implementation Method]

[0111] <Structure of Current Measuring Device>

[0112] Figure 9 This is an external view of the current measuring device according to the third embodiment of the present invention. Figure 9 As shown, the current measuring device 3 in this embodiment is a device that... Figure 6 The sensor head 10A of the current measuring device 2 shown is replaced with a sensor head 10B. The current measuring device 3 of this embodiment is similar to the current measuring device 2 of the second embodiment; in addition to being able to measure the DC and low-frequency components of the current I flowing through the conductor MC being measured, it can also measure components from low frequency to high frequency.

[0113] Figure 10This is a cross-sectional view of the magnetic shielding of the sensor head in the current measuring device according to the third embodiment of the present invention. Additionally, Figure 10 Equivalent to Figure 3B The cross-sectional view shown. The sensor head 10B has the following structure: the Rogowski sensor SE2 of the sensor head 10A in the second embodiment is omitted, and a coil SE3 (second sensor) is provided instead.

[0114] Like the Rogowski sensor SE2, coil SE3 detects alternating magnetic fields ranging from low frequencies (e.g., several kHz) to high frequencies (e.g., tens of MHz) generated by the current I flowing through the measured conductor MC. Coil SE3 is designed based on the maximum current (upper limit current) and the maximum frequency that can be measured by the current measuring device 3, such as... Figure 10 As shown, it is housed inside the magnetic shield 12.

[0115] Specifically, the coil SE3 is configured within the magnetic shield 12 such that when the sensor head 10B is fixed to the measured conductor MC by the fixing mechanism 13, the detection axis (magnetic sensing direction) aligns with the direction of the magnetic field generated by the current I (the tangential direction of the measured conductor MC). By configuring the coil SE3 in this manner, the influence of the external magnetic field flowing into the magnetic shield 12 from the cutout CP2 on the coil SE3 can be reduced. Figure 10 In the example shown, coil SE3 is located inside magnetic shield 12 at a distance from the center of the measured conductor MC that is greater than the distance between magnetic sensor SE1 and the center of the measured conductor MC. Furthermore, the position of coil SE3 inside sensor head 10B is not limited to... Figure 10 The example location can also be set to... Figure 10 The positions shown are different.

[0116] The circuit section 20A has the same structure as the circuit section 20A of the current measuring device 2 in the second embodiment. The circuit configuration of the current measuring device 3 in this embodiment only requires... Figure 7 The Rogowski sensor SE2 shown can be replaced with coil SE3, and sensor head 10A can be replaced with sensor head 10B. The cable CB is the same as in the first and second embodiments, preferably a flexible cable; furthermore, a cable that is easy to lay out is preferred, and a cable that is difficult to break is also preferred.

[0117] <Operation of the current measuring device>

[0118] The operation of the current measuring device 3 in this embodiment is basically the same as that of the current measuring device 2 in the second embodiment, so detailed description is omitted. In addition, the Rogowski sensor SE2 included in the current measuring device 2 of the second embodiment is omitted in this embodiment, so the configuration operation of the Rogowski sensor SE2 performed in the second embodiment (the operation of configuring the Rogowski sensor SE2 to surround the measured conductor MC) is omitted.

[0119] As described above, in this embodiment, the magnetic shield 12 houses: a magnetic sensor SE1, which detects a DC magnetic field and a low-frequency AC magnetic field generated by the current flowing through the conductor MC being measured; and a coil SE3, which detects an AC magnetic field ranging from low frequency to high frequency generated by the current flowing through the conductor MC being measured. Furthermore, based on the detection results of the magnetic sensor SE1, the current flowing through the conductor MC being measured (DC current and low-frequency AC current) is calculated, and based on the detection results of the coil SE3, the current flowing through the conductor MC being measured (from low frequency to high frequency) is calculated, and the various calculation results are combined. Therefore, in this embodiment, the current I flowing through the conductor MC being measured (DC and low-frequency components, as well as components ranging from low frequency to high frequency) can be measured with high precision in a compact and non-contact manner.

[0120] Furthermore, in this embodiment, a coil SE3 housed inside the magnetic shield 12 is used instead of the Rogowski sensor SE2 included in the current measuring device 2 of the second embodiment. Therefore, the configuration work of the Rogowski sensor SE2 required in the second embodiment (the work of configuring the Rogowski sensor SE2 to surround the measured conductor MC) can be omitted, and the sensor head can be further miniaturized.

[0121] [Fourth Implementation Method]

[0122] The current measuring device of the fourth embodiment of the present invention has a beam member BM provided inside the magnetic shielding 12 of the sensor heads 10, 10A, and 10B provided in the current measuring devices 1 to 3 of the first to third embodiments. This current measuring device improves the SN ratio within the magnetic shielding 12, thereby improving measurement accuracy. Furthermore, the following description will take the structure of the current measuring device 1 of the first embodiment, in which the beam member BM is provided inside the magnetic shielding 12 of the sensor head 10, as an example.

[0123] Figures 11A to 11D This is a diagram showing the structure of the magnetic shielding member provided on the sensor head of the current measuring device according to the fourth embodiment of the present invention. Figure 11A This is a perspective view of the magnetic shielding component 12. Figure 11B This is a cross-sectional view of the magnetic shielding component 12. Figure 11C , Figure 11D This is a perspective view illustrating the beam member BM disposed inside the magnetic shield 12. Additionally, Figure 11B Equivalent to Figure 3B The cross-section shown is in view.

[0124] The beam member BM is formed, for example, from the same material as the magnetic shield 12 (e.g., permalloy). The thickness of the beam member BM is set to be equal to or greater than the thickness of the magnetic shield 12, so that even if the maximum current (upper limit current) that can be measured by the current measuring device 1 flows through the measured conductor MC, magnetic saturation will not occur. Alternatively, the beam member BM can also be manufactured using the same method as the magnetic shield 12.

[0125] Furthermore, the beam member BM can be integrally formed with the magnetic shield 12, or it can be formed separately from the magnetic shield 12. In the case where the beam member BM and the magnetic shield 12 are formed separately, for example, it is possible to use... Figure 11C or Figure 11D The beam member BM is shown. Figure 11C The beam member BM shown is composed of a quadrangular prism-shaped beam section bm and a pair of columnar support sections sp located at both ends of the beam section bm. Figure 11D The beam member BM shown is composed of a quadrangular prism-shaped beam bm, a pair of columnar support parts sp located at both ends of the beam bm, and a connecting part cn that connects the other ends of the support parts sp to each other.

[0126] The beam member BM is disposed inside the magnetic shield 12, for example, as a quadrangular prism-shaped beam portion bm extending in the X direction on the -Z side of the magnetic sensor SE1 (between the magnetic sensor SE1 and the cutout portion CP2). In this case, the two ends (a pair of columnar support portions sp) of the beam portion bm of the beam member BM contact the inner walls of the first shielding member 12a and the second shielding member 12b, respectively. Furthermore, the beam member BM does not necessarily need to be configured so that the beam portion bm extends in the X direction. For example, the beam member BM can also be configured so that the beam portion bm extends in the Y direction.

[0127] Figure 12A and Figure 12B This is a graph showing the simulation results of the magnetic flux density distribution in the fourth embodiment of the present invention. Specifically, the simulation results shown in FIG12 are the results of obtaining the magnetic flux density within the magnetic shield 12 when an external magnetic field EM in the Z-axis direction is present through simulation. Figure 12A This represents an example where beam member BM is not specified. Figure 12B This represents an example of a beam member BM.

[0128] Reference Figure 12AWithout the beam member BM, the magnetic flux density distribution within the magnetic shield 12 is approximately an elliptical distribution centered on the measured conductor MC, gradually decreasing with distance from the conductor MC. In contrast, refer to... Figure 12B In the magnetic flux density distribution within the magnetic shield 12 when the beam member BM is provided, a region R1 with reduced magnetic flux density appears on the +Z side of the beam member BM.

[0129] Figure 13 This is a graph showing the simulation results of the SN ratio in the fourth embodiment of the present invention. Additionally, Figure 13 The curve shown is Figure 4 Similarly, the graph shown has the horizontal axis representing the distance from the center of the measured conductor MC in the Z direction, and the vertical axis representing the SN ratio (logarithm). Additionally, as... Figure 13 As shown, in the simulation, the radius of the conductor MC to be measured is set to 5 [mm], and the beam member BM with a diameter of 2 [mm] is set at a position 6 [mm] away from the center of the conductor MC to be measured.

[0130] Reference Figure 13 It can be seen that when the beam member BM is omitted, the SN ratio gradually decreases as the distance from the measured conductor MC (distance from the center of the measured conductor MC) increases. In contrast, it can be seen that when the beam member BM is provided, at a distance of approximately 11.5 [mm] from the center of the measured conductor MC, the SN ratio increases sharply, reaching a point greater than 100:1. Therefore, by placing the magnetic sensor SE1 at this location, the measurement accuracy can be improved.

[0131] The above describes a current measuring device according to an embodiment of the present invention. However, the present invention is not limited to the above embodiments and can be freely modified within the scope of the present invention. For example, in the above embodiments, the current measuring device connects the sensor head and the circuit section via a cable CB, but the function of the circuit section can also be set in the sensor head, making the sensor head and the circuit section integrated.

[0132] Furthermore, in the above embodiment, the example described is a screw mechanism with a guide for fixing the sensor head 13; however, the fixing mechanism 13 is not limited to a screw mechanism with a guide. Regardless of the diameter of the conductor MC being measured, any mechanism can be used as long as the fixing mechanism 13 can fix the conductor MC being measured in such a way that the distance between the center of the conductor MC and the magnetic sensor SE1 is a predetermined reference distance r. For example, a resin leaf spring or the like, which is configured to clamp the side of the conductor MC being measured, can be used.

[0133] Furthermore, in the above embodiment, an example was described where the sensor head fixing mechanism 13 is disposed on the +X side of the magnetic shield 12. However, the fixing mechanism 13 may be disposed on the -X side of the magnetic shield 12, or it may be disposed inside the magnetic shield 12.

[0134] In this specification, terms indicating direction such as "front," "back," "up," "down," "right," "left," "vertical," "horizontal," "longitudinal," "horizontal," "row," and "column" refer to these directions in the device of the present invention. Therefore, these terms in the specification of the present invention should be interpreted relative to the device of the present invention.

[0135] The term "constituent" is used to describe the function of performing the invention, or to indicate the structure, elements, or parts of a device.

[0136] Furthermore, the term “means plus function” in the claims should include any structure capable of performing the functions contained in the present invention.

[0137] The term "unit" is used to refer to a constituent element, a unit, hardware, or a part of software programmed to perform a desired function. Typical examples of hardware are devices and circuits, but are not limited to these.

[0138] The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications to the structure can be made without departing from the spirit of the present invention. The present invention is not limited by the foregoing description but only by the appended claims.

[0139] Explanation of reference numerals in the attached figures

[0140] 1-3 Current measuring devices

[0141] 10, 10A, 10B sensor heads

[0142] 12 magnetic shielding components

[0143] 13 Fixed Mechanisms

[0144] 20, 20A Circuit Section

[0145] 21, 23 Arithmetic Units

[0146] 24Synthetic Department

[0147] BM beam components

[0148] CP2 incision

[0149] I current

[0150] MC is the conductor being measured

[0151] r reference distance

[0152] SE1 magnetic sensor

[0153] SE2 Rogowski sensor

[0154] SE3 coil

Claims

1. A current measuring device for measuring the current flowing through a conductor being measured, the current measuring device being characterized by comprising: The first sensor detects the DC magnetic field and the low-frequency AC magnetic field generated by the current flowing through the conductor being measured; A hollow magnetic shielding member has a cutout through which the conductor being measured passes, and internally houses the first sensor; The measuring conductor is fixed in such a way that the distance between the center of the conductor being measured, which passes through the cut portion of the magnetic shielding member, and the first sensor is a predetermined reference distance; as well as The first arithmetic unit calculates the current flowing through the conductor being measured based on the detection result of the first sensor. The cutout is formed on one side of the magnetic shielding member in a first direction, extending from one end of a second direction intersecting the first direction to the other end. The first sensor is configured on a straight line extending from the center of the conductor being measured through the cutout to the other side of the first direction of the magnetic shielding member and parallel to the first direction, and is configured inside the magnetic shielding member such that the magnetic sensing direction is orthogonal to the first direction.

2. The current measuring device according to claim 1, characterized in that... include: The sensor head includes the first sensor, the magnetic shielding component, and the fixing mechanism. as well as The circuit section includes the first arithmetic section.

3. The current measuring device according to claim 2, characterized in that, The sensor head also includes a second sensor that detects alternating magnetic fields ranging from low to high frequencies generated by the current flowing through the conductor being measured. The circuit section also includes: The second arithmetic unit calculates the current flowing through the measured conductor based on the detection result of the second sensor; and The synthesis unit synthesizes the calculation results of the first arithmetic unit and the calculation results of the second arithmetic unit.

4. The current measuring device according to claim 3, characterized in that, The second sensor includes a Rogowski sensor, which is wound around the conductor being measured through the cut-out portion of the magnetic shielding member.

5. The current measuring device according to claim 3, characterized in that, The second sensor includes a coil housed inside the magnetic shielding member.

6. The current measuring device according to claim 5, characterized in that, The coil is arranged inside the magnetic shielding member such that its magnetic induction direction is tangential to the measured conductor passing through the cut.

7. The current measuring device according to any one of claims 1 to 6, characterized in that, Inside the magnetic shielding member, a beam member is formed between the cutout and the first sensor.

8. The current measuring device according to any one of claims 1 to 6, characterized in that, The first sensor is disposed inside the magnetic shielding member such that its magnetic sensing direction is tangential to the conductor being measured passing through the cut.

9. The current measuring device according to any one of claims 1 to 6, characterized in that, The thickness of the magnetic shielding component is set such that even if the maximum current that can be measured by the current measuring device flows through the conductor being measured, magnetic saturation will not occur.

10. The current measuring device according to claim 1, characterized in that, The first arithmetic unit calculates the current flowing through the measured conductor by multiplying the detection result of the first sensor with a constant uniquely determined based on the reference distance.

11. The current measuring device according to claim 1, characterized in that, The current measuring device further includes an output unit, which outputs the measurement result of the current flowing through the measured conductor, which is obtained by the first calculation unit, to the outside.

12. The current measuring device according to claim 2, characterized in that, The circuit section is separate from the sensor head and is connected to the sensor head via a cable.

13. The current measuring device according to claim 3, characterized in that, The synthesis unit includes: A low-pass filter removes high-frequency components from the calculation results of the first arithmetic unit and allows low-frequency components to pass through; A high-pass filter removes low-frequency components from the calculation results of the second arithmetic unit and allows high-frequency components to pass through; The signal level adjustment unit adjusts the level of the signal output from the low-pass filter; and The addition unit adds the signal whose level has been adjusted by the signal level adjustment unit to the signal output from the high-pass filter.

14. The current measuring device according to claim 7, characterized in that, The thickness of the beam member is set to be equal to or greater than the thickness of the magnetic shielding member, so that even if the maximum current that can be measured by the current measuring device flows through the conductor being measured, magnetic saturation will not occur.

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