Current measuring device

Abstract

To provide a small-sized current measurement device capable of measuring the current flowing through a conductor to be measured with high accuracy without contact.SOLUTION: A current measurement device includes: a first sensor that detects DC magnetic field and low-frequency AC magnetic field generated by current flowing through a conductor to be measured; a hollow magnetic shielding member that has a notch through which the conductor to be measured is inserted and houses the first sensor inside; a fixing mechanism that fixes the conductor to be measured so that a distance between the center of the conductor to be measured inserted through the notch of the magnetic shielding member and the first sensor is a predetermined reference distance; and a first arithmetic unit that obtains the current flowing through the conductor to be measured from the detection result of the first sensor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a current measuring device. [Background technology]

[0002] Conventionally, various current measuring devices capable of contactlessly measuring the current flowing through a conductor to be measured have been developed. Representative examples of such current measuring devices include a CT (Current Transformer) type current measuring device, a zero-flux type current measuring device, a Rogowski type current measuring device, a Hall element type current measuring device, and the like.

[0003] For example, CT and zero-flux current measuring devices measure the current flowing through a conductor by placing a magnetic core with a winding around it and detecting the current flowing through the winding (secondary side) so as to cancel the magnetic flux generated in the magnetic core by the current flowing through the conductor (primary side). A Rogowski current measuring device measures the current flowing through a conductor by placing a Rogowski coil (air-core coil) around the conductor and detecting the voltage induced in the Rogowski coil when the magnetic field generated by the AC current flowing through the conductor interlinks with the Rogowski coil.

[0004] The following Patent Document 1 discloses an example of a current measuring device using the zero flux method. Also, the following Patent Document 2 discloses a current measuring device using multiple magnetic sensors. Specifically, the current measuring device disclosed in the following Patent Document 2 arranges two magnetic sensors at different distances from the conductor to be measured, obtains the distance between the magnetic sensors and the conductor to be measured from the output of these magnetic sensors, and uses the obtained distance to obtain the magnitude of the current flowing through the conductor to be measured. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-55300 A [Patent Document 2] JP 2011-164019 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when measuring the current flowing through the conductor under test, if there is an influence of a magnetic field (external magnetic field) other than the magnetic field generated by the current flowing through the conductor under test, the accuracy of the current measurement may be deteriorated. If the current flowing through the conductor under test could be measured without contact, it would be possible to measure the current easily and efficiently. Furthermore, if the device is small, it would be possible to install it in a small space.

[0007] The present invention has been made in consideration of the above circumstances, and has an object to provide a small current measuring device that can measure a current flowing through a conductor to be measured in a non-contact manner with high accuracy. [Means for solving the problem]

[0008] In order to solve the above problem, a current measuring device according to one embodiment of the present invention is a current measuring device (1-3) that measures a current (I) flowing in a measured conductor (MC), and includes: a first sensor (SE1) that detects a DC magnetic field and a low-frequency AC magnetic field generated by the current flowing in the measured conductor; a hollow magnetic shielding member (12) that has a notch (CP2) through which the measured conductor is inserted and that houses the first sensor inside; a fixing mechanism (13) that fixes the measured conductor so that the distance between the center of the measured conductor inserted in the notch of the magnetic shielding member and the first sensor is a predetermined reference distance (r); and a first calculation unit (21) that calculates the current flowing in the measured conductor from the detection result of the first sensor.

[0009] Moreover, a current measuring device according to an aspect 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 unit (20, 20A) having the first calculation unit.

[0010] In addition, in a current measuring device according to one embodiment of the present invention, the sensor head further includes a second sensor (SE2, SE3) that detects a low- to high-frequency AC magnetic field generated by a current flowing through the measured conductor, and the circuit unit further includes a second calculation unit (23) that determines the current flowing through the measured conductor from the detection result of the second sensor, and a combination unit (24) that combines the calculation result of the first calculation unit and the calculation result of the second calculation unit.

[0011] In addition, in the current measuring device according to one aspect of the present invention, the second sensor includes a Rogowski sensor (SE2) wound around the conductor to be measured that is inserted into the cutout portion of the magnetic shielding member.

[0012] Alternatively, in the current measuring device according to one aspect of the present invention, the second sensor includes a coil (SE3) housed inside the magnetic shielding member.

[0013] Here, in a current measuring device according to one aspect of the present invention, the coil is arranged inside the magnetic shielding member so that the magnetic sensing direction is tangent to the conductor to be measured inserted into the cutout portion.

[0014] Moreover, in the current measuring device according to one aspect of the present invention, a beam member (BM) is formed inside the magnetic shielding member between the notch and the first sensor.

[0015] In addition, in a current measuring device according to one aspect of the present invention, the first sensor is arranged inside the magnetic shielding member so that the magnetic sensing direction is tangent to the conductor to be measured inserted into the cutout portion. Effect of the Invention

[0016] According to the present invention, there is an advantage that a small-sized device can measure a current flowing through a conductor to be measured in a non-contact manner with high accuracy. [Brief description of the drawings]

[0017] [Figure 1] 1 is an external perspective view of a current measuring device according to a first embodiment of the present invention. [Diagram 2] 1 is a perspective see-through view of a sensor head provided in a current measuring device according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing a magnetic shield provided in the current measuring device according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing a simulation result of an S / N ratio in the first embodiment of the present invention. [Diagram 5] 1 is a block diagram showing a configuration of a main part of a current measuring device according to a first embodiment of the present invention. [Figure 6] FIG. 4 is an external view of a current measuring device according to a second embodiment of the present invention. [Figure 7] FIG. 5 is a block diagram showing a configuration of a main part of a current measuring device according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a diagram for explaining a process performed in a synthesis unit of a circuit unit in the second embodiment of the present invention. [Figure 9] FIG. 11 is an external view of a current measuring device according to a third embodiment of the present invention. [Figure 10] 13 is a cross-sectional view of a magnetic shield of a sensor head provided in a current measuring device according to a third embodiment of the present invention. FIG. [Figure 11] 13 is a diagram showing the configuration of a magnetic shield provided on a sensor head of a current measuring device according to a fourth embodiment of the present invention. FIG. [Figure 12] FIG. 13 is a diagram showing a simulation result of a magnetic flux density distribution in the fourth embodiment of the present invention. [Figure 13] FIG. 13 is a diagram showing a simulation result of an S / N ratio in the fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, a current measuring device according to an embodiment of the present invention will be described in detail with reference to the drawings. First, an overview of the embodiment of the present invention will be described, and then each embodiment of the present invention will be described in detail.

[0019] 〔overview〕 The embodiment of the present invention is a small-sized device that can measure the current flowing through a conductor to be measured without contact and with high accuracy. Specifically, it can be installed in a small space when measuring the current, and can measure DC current and AC current up to several tens of MHz without contact and with high accuracy.

[0020] In recent years, in the development process of hybrid vehicles (HVs) and electric vehicles (EVs), there is a demand for measuring large currents flowing between batteries and power units, and between converters and inverters. In addition, in recent years, in pursuit of short-time acceleration, the upper limit of the current used has become higher, and therefore the wiring tends to become thicker. On the other hand, in order to expand the riding space and reduce weight, efforts are being made to reduce the space, integrate, and miniaturize devices. As a result, devices and connecting wiring are crowded together, making it difficult to secure space to place a current sensor. Under these circumstances, there is a demand for a current measuring device that can measure DC and AC currents flowing through wiring with limited surrounding space in a non-contact and highly accurate manner.

[0021] However, the zero-flux current measuring device disclosed in the above-mentioned Patent Document 1 requires a magnetic core having a certain size (for example, a diameter of about 20 cm) to be provided around the conductor to be measured, making it difficult to install in a narrow space. In addition, the above-mentioned Rogowski current measuring device detects the voltage induced in the Rogowski coil, so in principle it cannot measure direct current. In addition, in the low-frequency range, the output signal is weak and out of phase, resulting in poor measurement accuracy. In addition, the current measuring devices disclosed in the above-mentioned Patent Documents 1 and 2 are affected by magnetic fields (external magnetic fields) other than the magnetic field generated by the current flowing through the conductor to be measured, resulting in poor measurement accuracy.

[0022] In an embodiment of the present invention, a first sensor that detects a DC magnetic field and a low-frequency AC magnetic field generated by a current flowing through a conductor to be measured, a hollow magnetic shielding member having a notch through which the conductor to be measured is inserted and accommodating the first sensor inside, a fixing mechanism that fixes the conductor to be measured so that the distance between the conductor to be measured inserted into the notch of the magnetic shielding member and the first sensor is a predetermined reference distance, and a first calculation unit that calculates the current flowing through the conductor to be measured from the detection result of the first sensor. This makes it possible to measure the current flowing through the conductor to be measured in a small size, non-contact, and highly accurately.

[0023] [First embodiment] Configuration of current measuring device Fig. 1 is an external perspective view of a current measuring device according to a first embodiment of the present invention. As shown in Fig. 1, 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 a current I flowing through a conductor to be measured MC in a non-contact manner. The conductor to be measured MC is any conductor, such as a pin or a bus bar of a power semiconductor. In the following, for simplicity of explanation, the conductor to be measured MC is assumed to be a cylindrical conductor.

[0024] In the following explanation, the positional relationship of each component will be explained while referring to the XYZ Cartesian coordinate system set in the figure as necessary. In the XYZ Cartesian coordinate system shown in Fig. 1, the X axis is set in the longitudinal direction of the conductor MC to be measured (direction of current I), the Y axis is set in the horizontal direction, and the Z axis is set in the vertical direction. However, for the sake of convenience of explanation, the origin of the XYZ Cartesian coordinate system shown in each figure is not fixed, but its position is changed appropriately for each figure.

[0025] The sensor head 10 is a component for non-contact measurement of the current I flowing through the conductor MC to be measured. The sensor head 10 is used as a probe for non-contact measurement of the current I flowing through the conductor MC to be measured. It is desirable for the sensor head 10 to be as small as possible so that the current I can be measured even in a situation where the space around the conductor MC to be measured is limited.

[0026] 1, when measuring the current I flowing through the conductor MC to be measured, the sensor head 10 is fixedly disposed relative to the conductor MC to be measured. In other words, the sensor head 10 is placed in physical contact with the conductor MC to be measured. However, the sensor head 10 is electrically insulated from the conductor MC to be measured, and the current I flowing through the conductor MC to be measured does not flow into the sensor head 10. For this reason, the sensor head 10 can be said to be for measuring the current I flowing through the conductor MC to be measured in a non-contact manner.

[0027] Fig. 2 is a perspective see-through view of a sensor head included in the current measuring device according to the first embodiment of the present invention. As shown in Fig. 2, the sensor head 10 includes a housing 11, a magnetic shield 12 (magnetic shielding member), and a fixing mechanism 13. The housing 11 is a hollow member having a rectangular parallelepiped shape formed by combining a first housing 11a and a second housing 11b, and has a notch CP1 formed on the -Z side. The housing 11 (first housing 11a and second housing 11b) is made of a material (for example, a non-magnetic material such as resin) that does not affect the magnetic field generated by the current I. The housing 11 accommodates the magnetic shield 12 and the fixing mechanism 13 inside.

[0028] The cutout CP1 is formed on the -Z side of the housing 11 so as to extend from the end on the +X side to the end on the -X side. This cutout CP1 is for enabling a part of the conductor MC to be disposed inside the housing 11. The cutout CP1 illustrated in FIG. 2 has a shape that is roughly an inverted U shape when viewed in the X-axis direction. Since the cutout CP1 is formed so as to extend from the end on the +X side to the end on the -X side of the housing 11, a part of the conductor MC to be measured can be easily disposed inside the housing 11. In other words, the sensor head 10 is disposed so that the cutout CP1 faces the conductor MC to be measured so that the cutout CP1 and the conductor MC to be measured are parallel, and by simply moving the sensor head 10 toward the conductor MC to be measured, a part of the conductor MC to be measured can be easily disposed inside the housing 11.

[0029] FIG. 3 is a diagram showing a magnetic shield provided in the current measuring device according to the first embodiment of the present invention. FIG. 3(a) is an external perspective view of the magnetic shield 12, and FIG. 3(b) is a cross-sectional view taken along line AA in FIG. 3(a). As shown in FIG. 3(a), the magnetic shield 12 is a hollow member having a rectangular parallelepiped shape formed by combining a first shield member 12a and a second shield member 12b, and a notch CP2 is formed on the -Z side. The magnetic shield 12 (the first shield member 12a and the second shield member 12b) is made of a soft magnetic material (e.g., permalloy) having a small coercive force and a high magnetic permeability. This magnetic shield 12 is provided to shield a magnetic field (external magnetic field) other than a magnetic field (signal magnetic field) generated by a current I flowing through a measured conductor MC, and to improve the measurement accuracy of the current I.

[0030] The cutout CP2 is formed on the -Z side of the magnetic shield 12 so as to extend from the end on the +X side to the end on the -X side. This cutout CP2 is provided so that a part of the conductor MC to be measured is disposed inside the magnetic shield 12 when measuring the current I flowing through the conductor MC to be measured. In other words, the cutout CP2 is provided so that a part of the conductor MC to be measured is disposed inside the magnetic shield 12, which blocks the external magnetic field. The shape and size of the cutout CP2 when viewed in the X-axis direction are set to be the same (or approximately the same) as the shape and size of the cutout CP1 formed in the housing 11. The magnetic shield 12 is accommodated in the housing 11 so that the cutout CP2 overlaps with the cutout CP1 of the housing 11 when viewed in the X-axis direction.

[0031] The thickness of the magnetic shield 12 is set so that magnetic saturation does not occur even when the maximum current measurable by the current measuring device 1 (upper limit current: for example, 1000 [A] in effective value) flows through the conductor MC to be measured. The magnetic shield 12 may be made, for example, using a soft magnetic material having a thickness at which the above-mentioned magnetic saturation does not occur, or may be made using a laminated body having a thickness at which the above-mentioned magnetic saturation does not occur, by laminating a plurality of thin soft magnetic materials. Alternatively, the magnetic shield 12 may be made by casting, cutting, or the like to have a thickness at which the above-mentioned magnetic saturation does not occur.

[0032] As shown in Fig. 3(b), the magnetic shield 12 houses a magnetic sensor SE1 (first sensor) therein. The magnetic sensor SE1 is placed inside the magnetic shield 12 in order to improve the measurement accuracy of the current I by detecting a signal magnetic field in a state where the influence of an external magnetic field is eliminated. The magnetic sensor SE1 detects a DC magnetic field and a low-frequency (e.g., up to about a few kHz) AC magnetic field generated by the current I flowing through the measured conductor MC. For example, when the current I flowing through the measured conductor MC is a DC current, the magnetic field H shown in Fig. 2(b) is detected.

[0033] The magnetic sensor SE1 is required to have high responsiveness because it is used to measure the current I flowing through the conductor MC to be measured. For example, it is preferable that the delay time of the magnetic sensor SE1 is less than 1 [msec]. The magnetic sensor SE1 may be an analog sensor or a digital sensor as long as the response speed is sufficiently fast. The detection axes of the magnetic sensor SE1 are preferably three or more axes, but may be one or two axes. When the detection axes of the magnetic sensor SE1 are two or less axes, the magnetic sensor SE1 is disposed in the magnetic shield 12 so that the detection axis (magnetic sensing direction) is in the direction of the magnetic field generated by the current I (the tangential direction of the conductor MC to be measured) when the sensor head 10 is fixed to the conductor MC to be measured by the fixing mechanism 13. By disposing the magnetic sensor SE1 in this manner, it is possible to reduce the influence of the external magnetic field flowing into the magnetic shield 12 from the notch CP2 on the magnetic sensor SE1.

[0034] The magnetic sensor SE1 used has low noise in order to ensure the measurement accuracy of the current measuring device 1. For example, the magnetic sensor SE1 used has a noise component contained in the detection result of the magnetic sensor SE1 that is about 0.1% of the measurement range of the current measuring device 1. Note that the magnetic sensor SE1 may be, for example, a Hall element, a magnetoresistance effect element, or the like.

[0035] The magnetic sensor SE1 is installed in a position within the magnetic shield 12 where the intensity ratio (S / N ratio (signal-to-noise ratio)) between the signal magnetic field and the external magnetic field is approximately 100:1 or more. Fig. 4 is a diagram showing a simulation result of the S / N ratio in the first embodiment of the present invention. In addition, in the graph shown in Fig. 4, the horizontal axis represents the distance in the Z direction from the center of the measured conductor MC, and the vertical axis represents the S / N ratio (logarithm).

[0036] The simulation results shown in Fig. 4 are for a case where there is another conductor adjacent to the conductor MC, in which a current of the same magnitude as the current I flowing through the conductor MC, such as a three-phase AC current, flows. In Fig. 4, the graph shown by the solid line is the simulation result when the magnetic shield 12 is provided, and the graph shown by the dashed line is the simulation result when the magnetic shield 12 is omitted. In addition, as shown in Fig. 4, the radius of the conductor MC is set to 5 [mm] in the simulation.

[0037] 4, it can be seen that the SN ratio is much higher when the magnetic shield 12 is provided than when the magnetic shield 12 is omitted. It can also be seen that the SN ratio gradually decreases as the distance from the measured conductor MC (the distance from the center of the measured conductor MC) increases. In the simulation results shown in FIG. 4, if the distance from the center of the measured conductor MC is within 5 to 8 mm, the SN ratio is 100:1 or more. The magnetic sensor SE1 is installed, for example, in the magnetic shield 12 at a position 8 mm away from the center of the measured conductor MC in the Z direction.

[0038] The fixing mechanism 13 is a mechanism for fixing the sensor head 10 to the conductor MC to be measured, and is disposed on the +X side of the magnetic shield 12 as shown in Fig. 2. The fixing mechanism 13 fixes the conductor MC to be measured such that the distance between the center of the conductor MC to the magnetic sensor SE1 is a predetermined reference distance r, regardless of the diameter of the conductor MC to be measured. For example, the fixing mechanism 13 fixes the conductor MC to be measured such that the distance between the center of the conductor MC to the magnetic sensor SE1 is 8 mm.

[0039] The reason why the fixing mechanism 13 sets the distance of the magnetic sensor SE1 from the conductor to be measured MC to the reference distance r is to obtain the current I flowing through the conductor to be measured MC using only the detection result of the magnetic sensor SE1. In other words, the current I flowing through the conductor to be measured MC is obtained by multiplying the detection result of the magnetic sensor SE1 by a constant that is uniquely determined from the reference distance r. If the fixing mechanism 13 sets the distance of the magnetic sensor SE1 from the conductor to be measured MC to the reference distance r, the current I flowing through the conductor to be measured MC can be obtained using only the measurement result of the magnetic sensor SE1.

[0040] 2, the fixing mechanism 13 is a guided screw mechanism including a pair of guide members 13a, a pair of fixing arms 13b, left and right screws 13c, and a knob member 13d. The members constituting the fixing mechanism 13 (the pair of guide members 13a, the pair of fixing arms 13b, the left and right screws 13c, and the knob member 13d) are formed of a non-magnetic material such as resin.

[0041] The guide member 13a is a cylindrical member for guiding the fixing arm 13b in the Y direction. The pair of guide members 13a are arranged at a fixed interval in the Z direction with their longitudinal direction aligned with the Y direction. The fixing arm 13b is a rectangular prism-shaped member having a V-groove-shaped gripping portion GR, a guide hole through which the guide member 13a is inserted, and a screw hole through which the left and right screws 13c are inserted. The pair of fixing arms 13b are arranged so that the gripping portions GR face each other, the guide member 13a is inserted into the guide hole, and the left and right screws 13c are screwed into the screw holes.

[0042] The left-right screw 13c is, for example, a cylindrical screw with a right-handed thread provided on the right side (+Y side) from the center and a left-handed thread provided on the left side (-Y side) from the center. The knob member 13d is a cylindrical member attached to one end (end on the +Y side) of the left-right screw 13c, and is used to rotate the left-right screw 13c around its axis by a user's operation. When the left-right screw 13c rotates in one direction around its axis by operating the knob member 13d, the pair of fixing arms 13b move in the Y direction so as to move away from each other. In contrast, when the left-right screw 13c rotates in the other direction around the axis by operating the knob member 13d, the pair of fixing arms 13b move in the Y direction so as to move closer to each other.

[0043] Here, when the conductor to be measured MC is fixed to the sensor head 10, the conductor to be measured MC is sandwiched between the V-groove-shaped gripping portions GR formed on the pair of fixing arms 13b. When the conductor to be measured MC is sandwiched between the gripping portions GR, the positions in the Y direction and the Z direction are restricted, and the positions in the Y direction and the Z direction of the center of the conductor to be measured MC are the same regardless of the diameter of the conductor to be measured MC. In this way, the conductor to be measured MC is fixed to the sensor head 10 so that the distance between the center of the conductor to be measured MC and the magnetic sensor SE1 is the predetermined reference distance r, regardless of the diameter of the conductor to be measured MC.

[0044] 1 measures a current I flowing through a conductor to be measured MC based on a detection result (detection result of the magnetic sensor SE1) output from the sensor head 10. The circuit section 20 outputs or displays the measurement result of the current I to the outside. Any cable CB can be used as the cable CB connecting the sensor head 10 and the circuit section 20, but a cable that is flexible, easy to handle, and unlikely to break is preferable.

[0045] Fig. 5 is a block diagram showing the main configuration of a current measuring device according to a first embodiment of the present invention. In Fig. 5, blocks corresponding to the configuration shown in Fig. 1 are given the same reference numerals. Below, the internal configuration of the circuit section 20 will be described in detail, mainly with reference to Fig. 5. As shown in Fig. 2, the circuit section 20 includes a calculation section 21 (first calculation section) and an output section 22.

[0046] The calculation unit 21 determines the current I flowing through the measured conductor MC from 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, so the current I determined by the calculation unit 21 is a DC and low-frequency component. The calculation unit 21 prestores distance information indicating the reference distance r described above. The calculation unit 21 determines the current I flowing through the measured conductor MC by calculating the product of the detection result (magnetic field H) of the magnetic sensor SE1 and a constant uniquely determined from the reference distance r.

[0047] The output unit 22 outputs to the outside the measurement result of the current I calculated by the calculation unit 21. Note that the output unit 22 may include, for example, an output terminal that outputs a signal indicating the measurement result of the current I to the outside, and may include a display device (for example, a liquid crystal display device) that displays the measurement result of the current I to the outside.

[0048] 1, the circuit unit 20 is separate from the sensor head 10 and is connected to the sensor head 10 via a cable CB. With this configuration, the magnetic field detection function (magnetic sensor SE1) and the calculation function (calculation unit 21 and output unit 22) can be separated. This makes it easier to handle the sensor head 10, and makes it easier to install the sensor head 10 in a small space, for example. In addition, it is possible to avoid various problems (for example, temperature characteristics, insulation resistance) that arise when the calculation function is provided within the sensor head 10, thereby expanding the range of uses of the current measuring device 1.

[0049] <Operation of the current measuring device> Next, a description will be given of the operation when measuring the current I flowing through the conductor to be measured MC using the current measuring device 1. First, in order to measure the current I flowing through the conductor to be measured MC, a user of the current measuring device 1 fixes the sensor head 10 to the conductor to be measured MC as shown in FIG.

[0050] Specifically, the user of the current measuring device 1 places the sensor head 10 with the notch CP1 facing the conductor to be measured MC so that the notch CP1 and the conductor to be measured MC are parallel, and moves the sensor head 10 toward the conductor to be measured MC. As a result, a part of the conductor to be measured MC is placed inside the housing 11 of the sensor head 10. The user of the current measuring device 1 operates the knob member 13d of the fixing mechanism 13 to move the pair of fixing arms 13b in directions approaching each other, so that the conductor to be measured MC is sandwiched between the gripping portions GR of the pair of fixing arms 13b.

[0051] When the above operations are performed, the conductor to be measured MC is fixed to the sensor head 10 by the fixing mechanism 13, and the conductor to be measured MC is inserted into the notch CP2 of the magnetic shield 12 provided on the sensor head 10. In this state, the distance of the magnetic sensor SE1 from the conductor to be measured MC inserted into the notch CP2 of the magnetic shield 12 is set to the reference distance r.

[0052] After the above operations are completed, a process for measuring the current I flowing through the conductor MC to be measured is performed. Specifically, first, a process for detecting a magnetic field formed by the current I flowing through the conductor MC to be measured is performed by the magnetic sensor SE1. Next, a process for calculating the current I flowing through the conductor MC to be measured from the detection result of the magnetic sensor SE1 is performed by the calculation unit 21. Specifically, the calculation unit 21 performs a process for calculating the product of a constant (a constant uniquely determined from the reference distance r) stored in itself and the detection result (magnetic field H) of the magnetic sensor SE1, thereby calculating the current I (DC and low-frequency components) flowing through the conductor MC to be measured. After the above processes are completed, a process for outputting information indicating the current I calculated by the calculation unit 21 is performed by the output unit 22. The above processes are performed continuously or repeatedly at a fixed cycle (for example, 1 second).

[0053] As described above, this embodiment includes the hollow magnetic shield 12 having the notch CP2 through which the conductor to be measured MC is inserted and accommodating the magnetic sensor SE1 inside, the fixing mechanism 13 that fixes the conductor to be measured MC so that the distance between the center of the conductor to be measured MC and the magnetic shield 12 is the predetermined reference distance r, and the calculation unit 21 that determines the current flowing through the conductor to be measured MC from the detection result of the magnetic sensor SE1. Therefore, this embodiment is small and can measure the current I (DC and low-frequency components) flowing through the conductor to be measured MC with high accuracy and in a non-contact manner.

[0054] Second Embodiment Configuration of current measuring device Fig. 6 is an external view of a current measuring device according to a second embodiment of the present invention. As shown in Fig. 6, 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 a conductor MC to be measured in a non-contact manner. The conductor MC to be measured may be any conductor, such as a pin or a bus bar of a power semiconductor, but in this embodiment, the conductor MC to be measured is assumed to be a cylindrical conductor to simplify the explanation.

[0055] The sensor head 10A has a configuration 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 described above measures the DC and low frequency components of the current I flowing through the measured conductor MC. In contrast, the current measuring device 2 of the present embodiment is capable of measuring low to high frequency components in addition to the DC and low frequency components of the current I flowing through the measured conductor MC.

[0056] The Rogowski sensor SE2 detects low-frequency (e.g., several kHz) to high-frequency (e.g., several tens of MHz) AC magnetic fields generated by a current I flowing through the measured conductor MC. The Rogowski sensor SE2 is a sensor that uses a Rogowski coil (air-core coil) and is arranged to surround the measured conductor MC. Note that the Rogowski sensor SE2 is configured such that one end E1 is detachable from the sensor head 10A to facilitate arrangement around the measured conductor MC.

[0057] The circuit unit 20A measures the current I flowing through the measured conductor MC based on the detection results (detection results of the magnetic sensor SE1 and the Rogowski sensor SE2) output from the sensor head 10A. The circuit unit 20A outputs or displays the measurement result of the current I to the outside. As in the first embodiment, the cable CB is preferably flexible, easy to handle, and resistant to breakage.

[0058] Fig. 7 is a block diagram showing the main configuration of a current measuring device according to a second embodiment of the present invention. In Fig. 7, blocks corresponding to the configuration shown in Fig. 5 are given the same reference numerals. Below, the internal configuration of the circuit section 20A will be described in detail, mainly with reference to Fig. 7. As shown in Fig. 7, the circuit section 20A includes a calculation section 23 (second calculation section) and a synthesis section 24 in addition to a calculation section 21 and an output section 22.

[0059] The calculation unit 23 determines the current I flowing through the measured conductor MC from the detection result of the Rogowski sensor SE2. As described above, the Rogowski sensor SE2 detects AC magnetic fields from low to high frequencies, so the current I determined by the calculation unit 23 is a component from low to high frequencies. The detection result of the Rogowski sensor SE2 indicates the voltage induced in the Rogowski coil by the AC magnetic field generated around the current I (AC current) flowing through the measured conductor MC. The calculation unit 23 determines the current I flowing through the measured conductor MC by performing a calculation to convert the detection result (voltage) of the Rogowski sensor SE2 into a current value.

[0060] The synthesis unit 24 synthesizes the calculation result of the calculation unit 21 and the calculation result of the calculation 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 calculation result of the calculation unit 21 and passes low-frequency components to obtain a signal with desired frequency characteristics suitable for the synthesis process described below. The high-pass filter 24b removes low-frequency components from the calculation result of the calculation unit 23 and passes high-frequency components to obtain a signal with desired frequency characteristics suitable for the synthesis process described below.

[0061] 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 measured conductor MC, 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. For example, a variable resistor can be used as the signal level adjustment unit 24c.

[0062] In this embodiment, the signal level adjustment unit 24c that adjusts only the level of the signal output from the low-pass filter 24a is provided, but the present invention is not limited to this. 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 that can adjust the level of the first signal and the level of the second signal may be provided.

[0063] The adder 24d adds the signal whose signal level has been adjusted by the signal level adjuster 24c and the signal output from the high-pass filter 24b. The signal whose signal level has been adjusted by the signal level adjuster 24c is a signal that represents the DC and low-frequency components of the current I. The signal that is output from the high-pass filter 24b is a signal that represents the high-frequency components of the current I. Therefore, by adding these together, a signal that represents the DC and AC components up to high frequencies can be obtained.

[0064] Fig. 8 is a diagram for explaining the processing performed in the synthesis unit of the circuit unit in the second embodiment of the present invention. Fig. 8(a) is a diagram showing an example of the filter characteristics of the low-pass filter 24a. Fig. 8(b) is a diagram showing an example of the filter characteristics of the high-pass filter 24b. Fig. 8(c) is a diagram showing an example of the frequency characteristics of the synthesis unit.

[0065] 8(a) and 8(b), the cutoff frequencies of the low-pass filter 24a and the high-pass filter 24b are both fc. That is, the low-pass filter 24a generally has a characteristic of removing frequency components higher than the cutoff frequency fc and passing frequency components lower than the cutoff frequency fc. The high-pass filter 24b generally has a characteristic of removing frequency components lower than the cutoff frequency fc and passing frequency components higher than the cutoff frequency fc.

[0066] As shown in Fig. 8(c), the frequency characteristic of the combiner 24 is, so to speak, a characteristic obtained by combining the characteristic shown in Fig. 8(a) and the characteristic shown in Fig. 8(b) so that they are flat at the cutoff frequency fc and in the vicinity thereof. In other words, the frequency characteristic of the combiner 24 is such that the effective value of the AC current from low frequency to high frequency is flat, and the effective value (current value) of the DC current is a value that is approximately equal to the effective value of the AC current that is flat in this frequency characteristic.

[0067] Here, in order for the signal (measurement result of the current I) synthesized by the synthesis unit 24 to reproduce the current I flowing through the measured conductor MC, the delay time t delay The relationship between the above cutoff frequency fc and t delay <(1 / fc)×(1 / 100). Note that the above delay time t delay is the time required for the magnetic sensor SE1 to output a detection result after the current flowing through the conductor to be measured MC changes (that is, after the magnetic field applied to the magnetic sensor SE1 changes).

[0068] The output unit 22 outputs the signal (measurement result of the current I) combined by the combiner 24 to the outside. Note that, similarly to the first embodiment, the output unit 22 may include, for example, an output terminal that outputs a signal indicating the measurement result of the current I to the outside, and may include a display device (for example, a liquid crystal display device) that displays the measurement result of the current I to the outside.

[0069] Here, as shown in FIG. 7, the circuit unit 20A is separated from the sensor head 10A and is connected to the sensor head 10A via a cable CB. With this configuration, the magnetic field detection function (magnetic sensor SE1, Rogowski sensor SE2) and the calculation function (calculation units 21, 23, synthesis unit 24, and output unit 22) can be separated. This makes it easier to handle the sensor head 10A, and for example, makes it easier to install the sensor head 10A in a narrow space. In addition, it is possible to avoid various problems (for example, temperature characteristics, insulation resistance) that arise when the calculation function is provided inside the sensor head 10A, and thus the applications of the current measuring device 2 can be expanded.

[0070] <Operation of the current measuring device> Next, an operation for measuring the current I flowing through the conductor MC to be measured using the current measuring device 2 will be described. First, in order to measure the current I flowing through the conductor MC to be measured, a user of the current measuring device 2 performs an operation of fixing the sensor head 10A to the conductor MC to be measured using the fixing mechanism 13, as in the first embodiment. When the above operation is performed, the conductor MC to be measured is fixed to the sensor head 10A using the fixing mechanism 13, as in the first embodiment, and the distance of the magnetic sensor SE1 from the conductor MC to be measured is set to the reference distance r.

[0071] 6, the user of the current measuring device 2 arranges the Rogowski sensor SE2 so that it surrounds the conductor to be measured MC. At this time, if necessary, the user of the current measuring device 2 removes one end E1 of the Rogowski sensor SE2 from the sensor head 10A and fixes the sensor head 10A to the conductor to be measured MC. After completing this work, the user may arrange the Rogowski sensor SE2 in the above-mentioned state and then attach one end E1 of the Rogowski sensor SE2 to the sensor head 10A.

[0072] After the above operations are completed, a process for measuring the current I flowing through the conductor MC to be measured is performed. Specifically, first, a process for detecting a magnetic field formed by the current I flowing through the conductor MC to be measured is performed by the magnetic sensor SE1 and the Rogowski sensor SE2. Next, a process for calculating the current I flowing through the conductor MC to be measured from the detection results of the magnetic sensor SE1 and the Rogowski sensor SE2 is performed by the calculation units 21 and 23. Specifically, the calculation unit 21 performs a process for calculating the current I (DC and low-frequency components) flowing through the conductor MC to be measured by calculating the product of a constant (a constant uniquely determined from the reference distance r) stored in the calculation unit 21 and the detection result (magnetic field H) of the magnetic sensor SE1. In addition, the calculation unit 23 performs a process for calculating the current I (low- to high-frequency components) flowing through the conductor MC to be measured by performing a calculation for converting the detection result (voltage) of the Rogowski sensor SE2 into a current value.

[0073] Next, a process of combining the currents calculated by the calculation units 21 and 23 is performed by the combination unit 24. Specifically, first, the calculation result of the calculation unit 21 is input to the low-pass filter 24a to remove high-frequency components, and the calculation result of the calculation unit 23 is input to the high-pass filter 24b to remove low-frequency components. Next, a process of adjusting the levels of the signal output from the low-pass filter 24a (low-frequency components that have passed through the low-pass filter 24a) and the signal output from the high-pass filter 24b (high-frequency components that have passed through the high-pass filter 24b) is performed by the signal level adjustment unit 24c.

[0074] Then, the signal whose signal level has been adjusted by the signal level adjustment unit 24c and the signal output from the high-pass filter 24b are added by the addition unit 24d. In this manner, the currents calculated by the calculation units 21 and 23 are combined. When the above processing is completed, the current combined by the combination unit 24 is output from the output unit 22. The above processing is performed continuously or repeatedly at regular intervals (for example, one second).

[0075] As described above, in this embodiment, the magnetic sensor SE1 is housed in the magnetic shield 12 and detects the DC magnetic field and the low-frequency AC magnetic field generated by the current flowing through the conductor MC to be measured, and the Rogowski sensor SE2 detects the low-frequency to high-frequency AC magnetic field generated by the current flowing through the conductor MC to be measured. The current (DC current and low-frequency AC current) flowing through the conductor MC to be measured is obtained from the detection result of the magnetic sensor SE1, and the current (low-frequency to high-frequency) flowing through the conductor MC to be measured is obtained from the detection result of the Rogowski sensor SE2, and the respective calculation results are combined. Therefore, in this embodiment, the current I (DC and low-frequency components, and low-frequency to high-frequency components) flowing through the conductor MC to be measured can be measured in a small size with high accuracy without contact.

[0076] Third Embodiment Configuration of current measuring device Fig. 9 is an external view of a current measuring device according to a third embodiment of the present invention. As shown in Fig. 9, the current measuring device 3 of this embodiment has a configuration in which the sensor head 10A of the current measuring device 2 shown in Fig. 6 is replaced with a sensor head 10B. Like the current measuring device 2 of the second embodiment, the current measuring device 3 of this embodiment is capable of measuring low- to high-frequency components in addition to the DC and low-frequency components of the current I flowing through the conductor to be measured MC.

[0077] Fig. 10 is a cross-sectional view of a magnetic shield of a sensor head provided in a current measuring device according to a third embodiment of the present invention. Fig. 10 corresponds to the cross-sectional view shown in Fig. 3(b). The sensor head 10B is configured such that the Rogowski sensor SE2 of the sensor head 10A of the second embodiment is omitted and a coil SE3 (second sensor) is provided instead.

[0078] Similar to the Rogowski sensor SE2, the coil SE3 detects an AC magnetic field of low frequency (e.g., several kHz) to high frequency (e.g., several tens of MHz) generated by the current I flowing through the measured conductor MC. The coil SE3 is designed according to the maximum current (upper limit current) measurable by the current measuring device 3 and the maximum frequency measurable by the current measuring device 3, and is housed inside the magnetic shield 12 as shown in FIG.

[0079] Specifically, the coil SE3 is disposed in the magnetic shield 12 so that the detection axis (magnetic sensing direction) is in the direction of the magnetic field generated by the current I (the tangential direction of the measured conductor MC) when the sensor head 10B is fixed to the measured conductor MC by the fixing mechanism 13. By disposing the coil SE3 in this manner, it is possible to reduce the influence of the external magnetic field flowing into the magnetic shield 12 from the cutout portion CP2 on the coil SE3. In the example shown in FIG. 10, the coil SE3 is disposed in a position inside the magnetic shield 12 such that the distance from the center of the measured conductor MC is longer than the distance between the magnetic sensor SE1 and the center of the measured conductor MC. The position of the coil SE3 inside the sensor head 10B is not limited to the position illustrated in FIG. 10, and may be disposed in a position different from the position illustrated in FIG. 10.

[0080] The circuit section 20A has a configuration similar to that of the circuit section 20A included in the current measuring device 2 according to the second embodiment. The circuit configuration of the current measuring device 3 of this embodiment can be obtained by replacing the Rogowski sensor SE2 shown in Fig. 7 with the coil SE3 and the sensor head 10A with the sensor head 10B. As with the first and second embodiments, the cable CB is preferably flexible, easy to handle, and resistant to breakage.

[0081] <Operation of the current measuring device> The operation of the current measuring device 3 of this embodiment is basically the same as that of the current measuring device 2 of the second embodiment, and therefore a detailed description thereof will be omitted. Note that, in this embodiment, the Rogowski sensor SE2 included in the current measuring device 2 of the second embodiment is omitted, and therefore the arrangement work of the Rogowski sensor SE2 (the work of arranging the Rogowski sensor SE2 so that it surrounds the periphery of the measured conductor MC) performed in the second embodiment is omitted.

[0082] As described above, in this embodiment, the magnetic sensor SE1, which detects the DC magnetic field and low-frequency AC magnetic field generated by the current flowing through the measured conductor MC, and the coil SE3, which detects the low- to high-frequency AC magnetic field generated by the current flowing through the measured conductor MC, are housed inside the magnetic shield 12. The current (DC current and low-frequency AC current) flowing through the measured conductor MC is obtained from the detection result of the magnetic sensor SE1, and the current (low- to high-frequency) flowing through the measured conductor MC is obtained from the detection result of the coil SE3, and the respective calculation results are combined. Therefore, in this embodiment, the current I (DC and low-frequency components, and low- to high-frequency components) flowing through the measured conductor MC can be measured in a small size with high accuracy without contact.

[0083] Furthermore, in this embodiment, instead of the Rogowski sensor SE2 included in the current measuring device 2 of the second embodiment, a coil SE3 is provided inside the magnetic shield 12. Therefore, it is possible to omit the arrangement work of the Rogowski sensor SE2 required in the second embodiment (the arrangement work of the Rogowski sensor SE2 in a state where it surrounds the conductor to be measured MC), and to further reduce the size of the sensor head.

[0084] [Fourth embodiment] A current measuring device according to a fourth embodiment of the present invention is configured by providing a beam member BM inside the magnetic shield 12 of the sensor heads 10, 10A, 10B included in the current measuring devices 1 to 3 according to the first to third embodiments described above. Such a current measuring device aims to improve the signal-to-noise ratio in the magnetic shield 12 and thereby improve the measurement accuracy. In the following, an example in which a beam member BM is provided inside the magnetic shield 12 of the sensor head 10 included in the current measuring device 1 according to the first embodiment will be described.

[0085] Fig. 11 is a diagram showing the configuration of a magnetic shield provided in a sensor head of a current measuring device according to a fourth embodiment of the present invention. Fig. 11(a) is an external perspective view of a magnetic shield 12, Fig. 11(b) is a cross-sectional view of the magnetic shield 12, and Figs. 11(c) and (d) are perspective views illustrating beam members BM provided inside the magnetic shield 12. Fig. 11(b) corresponds to the cross-sectional view shown in Fig. 3(b).

[0086] The beam member BM is formed of, for example, the same material (for example, permalloy) as the magnetic shield 12. 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 the beam member BM is not magnetically saturated even when the maximum current (upper limit current) measurable by the current measuring device 1 flows through the measured conductor MC. The beam member BM may be produced by the same manufacturing method as the magnetic shield 12.

[0087] Moreover, the beam member BM may be formed integrally with the magnetic shield 12, or may be formed separately from the magnetic shield 12. When the beam member BM is formed separately from the magnetic shield 12, for example, the beam member BM shown in FIG. 11(c) or FIG. 11(d) can be used. The beam member BM shown in FIG. 11(c) is a member consisting of a rectangular prism-shaped beam portion bm and a pair of columnar support portions sp provided at both ends of the beam portion bm. The beam member BM shown in FIG. 11(d) is a member consisting of a rectangular prism-shaped beam portion bm, a pair of columnar support portions sp provided at both ends of the beam portion bm, and a connection portion cn that connects the other ends of the support portions sp.

[0088] The beam member BM is disposed inside the magnetic shield 12 so that, for example, the rectangular prism-shaped beam portion bm extends in the X direction on the -Z side of the magnetic sensor SE1 (between the magnetic sensor SE1 and the cutout portion CP2). At this time, the beam member BM is disposed so that both ends of the beam portion bm (a pair of columnar support portions sp) are in contact with the inner walls of the first shield member 12a and the second shield member 12b, respectively. Note that the beam member BM does not necessarily need to be disposed so that the beam portion bm extends in the X direction. For example, the beam member BM may be disposed so that the beam portion bm extends in the Y direction.

[0089] Fig. 12 is a diagram showing a simulation result of the magnetic flux density distribution in the fourth embodiment of the present invention. Specifically, the simulation result shown in Fig. 12 is obtained by simulating the magnetic flux density in the magnetic shield 12 when an external magnetic field EM in the Z-axis direction is present. Fig. 12(a) shows the case where the beam member BM is not provided, and Fig. 12(b) shows the case where the beam member BM is provided.

[0090] 12(a), the magnetic flux density distribution in the magnetic shield 12 when the beam member BM is not provided is approximately an elliptical distribution centered on the measured conductor MC, with the magnetic flux density gradually decreasing with increasing distance from the measured conductor MC. In contrast, when the beam member BM is provided, the magnetic flux density distribution in the magnetic shield 12 has an area R1 where the magnetic flux density decreases on the +Z side of the beam member BM.

[0091] Fig. 13 is a diagram showing a simulation result of the S / N ratio in the fourth embodiment of the present invention. In the graph shown in Fig. 13, the horizontal axis represents the distance in the Z direction from the center of the conductor MC to be measured, and the vertical axis represents the S / N ratio (logarithmic), as in the graph shown in Fig. 4. In the simulation, as shown in Fig. 13, the radius of the conductor MC to be measured is set to 5 [mm], and a beam member BM having a thickness of 2 [mm] is set at a position 6 [mm] away from the center of the conductor MC to be measured.

[0092] 13, when the beam member BM is omitted, the SN ratio gradually decreases as the distance from the measured conductor MC (the distance from the center of the measured conductor MC) increases. In contrast, when the beam member BM is provided, a location appears where the SN ratio suddenly increases to 100:1 or more at a distance of about 11.5 mm from the center of the measured conductor MC. Therefore, by placing the magnetic sensor SE1 at this location, the measurement accuracy can be improved.

[0093] Although the current measuring device according to the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be freely modified within the scope of the present invention. For example, in the current measuring device in the above embodiment, the sensor head and the circuit unit are connected by a cable CB, but the function of the circuit unit may be provided in the sensor head, and the sensor head and the circuit unit may be integrated.

[0094] In the above embodiment, the fixing mechanism 13 of the sensor head is a screw mechanism with a guide, but the fixing mechanism 13 is not limited to a screw mechanism with a guide. The fixing mechanism 13 can be any mechanism as long as it can fix the conductor MC to be measured such that the distance between the center of the conductor MC and the magnetic sensor SE1 is a predetermined reference distance r, regardless of the diameter of the conductor MC. For example, a resin leaf spring configured to clamp the side of the conductor MC can be used.

[0095] In the above-described embodiment, an example has been described in which the fixing mechanism 13 of the sensor head 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 may be disposed inside the magnetic shield 12. [Explanation of symbols]

[0096] 1~3 Current measuring device 10, 10A, 10B Sensor head 12 Magnetic shielding 13 Fixing mechanism 20,20A circuit section 21,23 Arithmetic unit 24 Synthesis section BM Beam member CP2 Notch I current MC Conductor under test r Reference distance SE1 Magnetic Sensor SE2 Rogowski Sensor SE3 Coil

Claims

1. A current measuring device for measuring a current flowing through a conductor to be measured, a first sensor for detecting a DC magnetic field and a low-frequency AC magnetic field generated by a current flowing through the conductor to be measured; a hollow magnetic shielding member having a substantially rectangular parallelepiped shape, a notch through which the conductor to be measured is inserted, and accommodating the first sensor therein; a fixing mechanism that fixes the conductor to be measured such that a distance between a center of the conductor to be measured, which is inserted into the notch of the magnetic shielding member, and the first sensor is a predetermined reference distance; a first calculation unit that calculates a current flowing through the conductor to be measured from a detection result of the first sensor; Equipped with the notch is formed on one side of the magnetic shielding member in a first direction, and extends from one end to the other end in a second direction intersecting the first direction, the first sensor is disposed on a straight line parallel to the first direction, extending from a center of the conductor to be measured inserted through the notch to the other side of the magnetic shielding member in the first direction, and is disposed inside the magnetic shielding member such that its magnetic sensing direction is perpendicular to the first direction. Current measuring device.

2. The current measuring device as described in claim 1, wherein the fixing mechanism is configured to be movable away from or toward each other along a third direction intersecting the first direction and the second direction, and has a pair of fixing arms that fix the conductor to be measured inserted into the notch by clamping it in the third direction.

3. a sensor head including the first sensor, the magnetic shielding member, and the fixing mechanism; a circuit unit having the first calculation unit; 3. The current measuring device according to claim 1, further comprising:

4. The sensor head further includes a second sensor for detecting a low-frequency to high-frequency AC magnetic field generated by a current flowing through the conductor to be measured, The circuit unit includes a second calculation unit that calculates a current flowing through the conductor to be measured based on a detection result of the second sensor; a synthesis unit that synthesizes a calculation result of the first calculation unit and a calculation result of the second calculation unit; The current measurement device of claim 3 further comprising:

5. 5. The current measuring device according to claim 4, wherein the second sensor comprises a Rogowski sensor wound around the conductor to be measured that is inserted into the notch of the magnetic shielding member.

6. The current measuring device according to claim 4 , wherein the second sensor includes a coil housed inside the magnetic shielding member.

7. 7. The current measuring device according to claim 6, wherein the coil is disposed inside the magnetic shielding member so that the magnetic sensing direction is tangent to the conductor to be measured inserted into the notch.

8. The current measuring device according to claim 1 , wherein a beam member is formed inside the magnetic shielding member between the notch and the first sensor.

9. 9. The current measuring device according to claim 1, wherein the first sensor is disposed inside the magnetic shielding member such that a magnetic sensing direction is a tangential direction of the conductor to be measured inserted into the cutout portion.

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