Current sensor, current measuring device, and current measuring method

Abstract

This suppresses the decrease in current measurement accuracy caused by the skin effect. [Solution] The current sensor comprises a shield having an opening for taking in a magnetic field generated by a current flowing through a conductor, a magnetic field sensor disposed inside the shield and outputting a sensor voltage corresponding to the magnetic field at that location, and a detection circuit disposed outside the shield and detecting a current based on the sensor voltage of the magnetic field sensor, wherein the magnetic field sensor includes a first magnetic field sensor for detecting low-frequency magnetic fields and a second magnetic field sensor for detecting high-frequency magnetic fields, the first magnetic field sensor being disposed closer to the opening than the second magnetic field sensor, and the second magnetic field sensor being disposed further from the opening than the first magnetic field sensor.

Description

Technical Field

[0001] The present disclosure relates to a current sensor, a current measuring device, and a current measuring method.

Background Art

[0002] In order to measure the current flowing through a conductor, there is a method of detecting the magnetic field generated by that current. When the frequency of the current increases, the skin effect occurs in the conductor, which may reduce the detection accuracy of the magnetic field and thus the measurement accuracy of the current. For example, in Patent Document 1, in order to reduce the influence of the skin effect, the output signals of two magnetoelectric conversion elements are subtracted from each other.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to prevent the influence of magnetic fields other than the magnetic field generated by the current flowing through the conductor, it is conceivable to cover the conductor with a shield. Patent Document 1 does not particularly consider countermeasures against the skin effect when using a shield.

[0005] One aspect of the present disclosure suppresses a decrease in the measurement accuracy of a current caused by the skin effect.

Means for Solving the Problems

[0006] A current sensor according to one aspect of the present disclosure comprises a shield having an opening for taking in a magnetic field generated by a current flowing through a conductor; a magnetic field sensor disposed inside the shield and outputting a sensor voltage corresponding to the magnetic field at that location; and a detection circuit disposed outside the shield and detecting a current based on the sensor voltage of the magnetic field sensor, wherein the magnetic field sensor includes a first magnetic field sensor for detecting low-frequency magnetic fields and a second magnetic field sensor for detecting high-frequency magnetic fields, the first magnetic field sensor being disposed closer to the opening than the second magnetic field sensor, and the second magnetic field sensor being disposed further from the opening than the first magnetic field sensor.

[0007] A current sensor according to one aspect of the present disclosure comprises a shield having an opening for taking in a magnetic field generated by a current flowing through a conductor; a magnetic field sensor disposed inside the shield and outputting a sensor voltage corresponding to the magnetic field at that location; a detection circuit disposed outside the shield and detecting a current based on the sensor voltage of the magnetic field sensor; and a moving mechanism for moving the magnetic field sensor. The magnetic field sensor includes a first magnetic field sensor disposed near the opening for detecting a low-frequency magnetic field and a second magnetic field sensor for detecting a high-frequency magnetic field, and the moving mechanism moves the second magnetic field sensor between a position near the opening and a position far from the opening.

[0008] A current measuring device according to one aspect of the present disclosure comprises a shield having an opening for taking in a magnetic field generated by a current flowing through a conductor; a magnetic field sensor disposed inside the shield and outputting a sensor voltage corresponding to the magnetic field at that location; a detection circuit disposed outside the shield and generating a detection voltage indicating the value of the current based on the sensor voltage of the magnetic field sensor; and an external device disposed outside the shield and correcting the detection voltage in the frequency domain.

[0009] A current measurement method relating to one aspect of the present disclosure is a current measurement method comprising: detecting a magnetic field at a location using a magnetic field sensor placed in a shield having an opening for taking in a magnetic field generated by a current flowing through a conductor; and detecting a current based on the detection result of the magnetic field sensor, wherein the magnetic field sensor includes a first magnetic field sensor for detecting a low-frequency magnetic field and a second magnetic field sensor for detecting a high-frequency magnetic field, the first magnetic field sensor being placed closer to the opening than the second magnetic field sensor, and the second magnetic field sensor being placed further from the opening than the first magnetic field sensor. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress the decrease in measurement accuracy of current caused by the skin effect. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of the schematic configuration of the current measuring device 100 according to the embodiment. [Figure 2] This figure shows an example of the schematic configuration of Shield 3. [Figure 3] This figure shows an example of detection circuit 6. [Figure 4] This figure shows an example of the schematic configuration of current sensor 1. [Figure 5] This figure shows examples of the nearby and distant regions. [Figure 6] This figure shows an example of the operation. [Figure 7] This figure shows an example of the operation. [Figure 8] This figure shows an example of frequency characteristics. [Figure 9] This flowchart shows an example of the processing (current measurement method) performed in current sensor 1. [Figure 10] This figure shows an example of the schematic configuration of current sensor 1. [Figure 11] This figure shows an example of the schematic configuration of the detection circuit 6. [Figure 12] This figure shows an example of how to determine whether or not there is an epidermal effect. [Figure 13] It is a diagram showing an example of determination of the presence or absence of the skin effect. [Figure 14] It is a flowchart showing an example of the process (current measurement method) executed in the current sensor 1. [Figure 15] It is a diagram showing an example of the schematic configuration of the current sensor 1. [Figure 16] It is a diagram showing an example of the schematic configuration of the detection circuit 6. [Figure 17] It is a flowchart showing an example of the process (current measurement method) executed in the current sensor 1. [Figure 18] It is a diagram showing an example of the schematic configuration of the current sensor 1. [Figure 19] It is a diagram showing an example of the schematic configuration of the detection circuit 6 and the external device 2. [Figure 20] It is a diagram showing an example of the waveform of the detection voltage V3 before correction. [Figure 21] It is a diagram showing an example of the frequency components of the detection voltage V3 before correction. [Figure 22] It is a diagram showing an example of the correction of the frequency components of the detection voltage V3. [Figure 23] It is a diagram showing an example of the inverse Fourier transform. [Figure 24] It is a flowchart showing an example of the process (current measurement method) executed in the current measurement device 100.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments will be described with reference to the drawings. The same elements are denoted by the same reference numerals, and overlapping descriptions will be omitted as appropriate.

[0013] FIG. 1 is a diagram showing an example of the schematic configuration of the current measurement device 100 according to the embodiment. The current measurement device 100 includes a current sensor 1 and an external device 2.

[0014] The current sensor 1 detects the current flowing through the conductor 9. The current sensor 1 is used in connection with an external device 2. In the example shown in Figure 1, the external device 2 is an oscilloscope, which displays, for example, the waveform of the current detected by the current sensor 1. In Figure 1, the input terminal 21 and the display unit 23 of the external device 2 are indicated by reference numerals.

[0015] The conductor 9 is installed in, for example, hybrid vehicles (HV) and electric vehicles (EV), and is used to carry currents of several amperes to tens of amperes or larger. Examples of conductor 9 include cables and busbars used to connect batteries and power units, or converters and inverters.

[0016] The current flowing through conductor 9 is denoted as current I and is illustrated in the diagram. The arrows in the diagram schematically indicate the direction of current I. Current I may be a direct current or an alternating current. The frequency (fundamental frequency) of current I is denoted as frequency f. A magnetic field is generated by the current I flowing through conductor 9. This magnetic field is denoted as magnetic field H and is illustrated in the diagram. The arrows in the diagram schematically indicate the direction of the magnetic field H.

[0017] The XYZ coordinate system is also shown. The Z-axis direction corresponds to the direction of extension of the conductor 9. The X-axis and Y-axis directions (XY plane direction) correspond to the cross-sectional direction of the conductor 9. The positive and negative X-axis directions are also called the left-right direction, etc. The positive and negative Y-axis directions are also called the up-down direction, etc. The positive and negative Z-axis directions are also called the front-back direction, etc.

[0018] The current sensor 1 includes a shield 3, a magnetic field sensor 4, an external unit 5, and a detection circuit 6. In the example shown in Figure 1, the shield 3 includes the magnetic field sensor 4, and the external unit 5 includes the detection circuit 6. The shield 3 corresponds to the head portion (sensor head) of the current sensor 1 and is used by being positioned near the conductor 9. The external unit 5 is connected to the input terminal 21 of the external device 2.

[0019] Shield 3 is configured to shield against magnetic fields. Shield 3 can also be called a magnetic field shield. Various known materials, including metallic materials, may be used.

[0020] The shield 3 has an opening 37. The opening 37 is used to take in (a portion of) the magnetic field H generated by the current flowing through the conductor 9. In this example, the opening 37 is formed by cutting out a portion of the lower part of the shield 3. The opening 37 can also be called a notch.

[0021] The shield 3 is attached to the conductor 9 so that the conductor 9 passes through the opening 37 of the shield 3, or the conductor 9 is fixed so that its position does not change. The method of attachment and fixing is not particularly limited. For example, a hook-shaped member, a ring-shaped member, etc. may be used near the opening 37 of the shield 3 to attach the shield 3 (sensor head) to the conductor 9, or a spring member, etc. may be used to fix the attachment.

[0022] Figure 2 shows an example of the schematic configuration of the shield 3. The shield 3 has a hollow, roughly box-like shape. The shield 3 includes a bottom plate 31, a top plate 32, side plates 33, side plates 34, side plates 35, and side plates 36. The bottom plate 31 to the side plates 36 define the shape of the shield 3, being magnetically close together or coupled to each other so that the shield 3 has an internal space 30 and an opening 37 inside it.

[0023] The bottom plate 31 and the top plate 32 are located on opposite sides of each other in the vertical direction (Y-axis direction), with the internal space 30 in between, and extend opposite each other in the XZ plane direction. In the positive Y-axis direction, the bottom plate 31, the internal space 30, and the top plate 32 are located in this order.

[0024] Side plates 33 and 34 are located on opposite sides of the internal space 30 in the left-right direction (X-axis direction), and extend opposite each other in the YZ plane direction as the plane direction. In the positive X-axis direction, side plate 33, internal space 30, and side plate 34 are located in this order.

[0025] Side plates 35 and 36 are located on opposite sides of each other in the front-to-back direction (Z-axis direction), with the internal space 30 in between, and extend so as to face each other in the XY plane direction. Side plate 35, internal space 30, and side plate 36 are located in this order in the positive Z-axis direction.

[0026] In this example, the opening 37 is formed by cutting out parts of the bottom plate 31, side plate 35, and side plate 36, and extends throughout the entire length of the shield 3 in the front-to-back direction (Z-axis direction). The area of ​​the opening 37 in the XY plane (size of the opening) is designed so that the conductor 9 can pass through the opening 37.

[0027] Unless otherwise specified, "inside Shield 3" refers to the internal space 30 of Shield 3. Within reasonable limits, "inside Shield 3" and "internal space 30" may be interpreted differently as appropriate.

[0028] Returning to Figure 1, the magnetic field H generated at the opening 37 of the shield 3, out of the current I flowing through the conductor 9, is taken into the shield 3 through the opening 37.

[0029] The magnetic field sensor 4 is placed inside the shield 3 and detects the magnetic field at that location. Since magnetic fields other than magnetic field H (magnetic fields that may cause disturbances) are blocked by the shield 3, the magnetic field sensor 4 detects magnetic field H at that location. The detection of magnetic field H includes the detection of the magnitude of magnetic field H, and may also include the detection of the direction of magnetic field H.

[0030] Specifically, the magnetic field sensor 4 outputs a sensor voltage corresponding to the magnetic field H at its location. When the shield 3 is attached to and fixed to the conductor 9, the relationship between the current I (magnitude and direction) flowing through the conductor 9 and the sensor voltage is uniquely determined. This relationship is known in advance based on, for example, the design of the shield 3 and magnetic field sensor 4, the specifications of the conductor 9, experimental data, etc.

[0031] The magnetic field sensor 4 may consist of multiple magnetic field sensors. In the example shown in Figure 1, there are two magnetic field sensors. The first magnetic field sensor is referred to and illustrated as magnetic field sensor 41. The second magnetic field sensor is referred to and illustrated as magnetic field sensor 42. Unless otherwise specified, they are simply called magnetic field sensor 4.

[0032] Magnetic field sensors 41 and 42 have different detection characteristics. Magnetic field sensor 41 detects magnetic fields of relatively low frequency (low-frequency magnetic fields). Low-frequency magnetic fields include DC magnetic fields. Magnetic field sensor 42 detects magnetic fields of relatively high frequency (high-frequency magnetic fields). The cutoff frequencies of the frequency bands of the low-frequency magnetic fields and the high-frequency magnetic fields must overlap.

[0033] Various known magnetic field sensors may be used. An example of a magnetic field sensor 41 is an integrated circuit (IC) sensor that includes a Hall element, also known as an analog Hall IC. An example of a magnetic field sensor 42 is a coil sensor that includes a coil. A Rogowski coil may also be used, and because it can be miniaturized, it becomes easier to arrange the magnetic field sensor 42 inside the shield 3.

[0034] Unless otherwise specified, the magnetic field sensor 41 shall be composed of an IC sensor. The magnetic field sensor 42 shall be composed of a coil sensor. The sensor voltage output by the magnetic field sensor 41 shall be referred to as sensor voltage V1. The sensor voltage output by the magnetic field sensor 42 shall be referred to as sensor voltage V2. When not specifically distinguished, these shall simply be referred to as sensor voltage, etc.

[0035] The sensor voltage V1 of magnetic field sensor 41 and the sensor voltage V2 of magnetic field sensor 42 are taken out of the shield 3 and supplied to the detection circuit 6 in the external unit 5. In the example shown in Figure 1, the shield 3 has terminal 38. Inside the shield 3, magnetic field sensors 41 and 42 are connected to terminal 38, for example, via wiring (not shown). Outside the shield 3, terminal 38 is connected to the detection circuit 6 in the external unit 5 via wiring W1.

[0036] The detection circuit 6 is located outside the shield 3 and detects the current I based on the sensor voltages of the magnetic field sensors 4, in this example, the sensor voltage V1 of magnetic field sensor 41 and the sensor voltage V2 of magnetic field sensor 42. See also Figure 3 for further explanation.

[0037] Figure 3 shows an example of the detection circuit 6. The detection circuit 6 combines sensor voltages V1 and V2 to generate a detection voltage V3. The detection voltage V3 is a voltage that indicates the value of the current I, and more specifically, it may be a voltage that indicates its instantaneous value. This detection voltage V3 corresponds to the detection result by the detection circuit 6, that is, the detection result of the current I by the current sensor 1, and consequently, the measurement result of the current I by the current measuring device 100.

[0038] As mentioned earlier, the relationship between the current I flowing through the conductor 9 and the sensor voltages of the magnetic field sensors 4, namely the sensor voltage V1 of magnetic field sensor 41 and the sensor voltage V2 of magnetic field sensor 42, is known in advance. Based on this relationship, the detection circuit 6 is designed to generate a detection voltage V3 from the sensor voltages V1 and V2.

[0039] Specifically, in the example shown in Figure 3, the detection circuit 6 includes a combining unit 61. The combining unit 61 combines the sensor voltage V1 and the sensor voltage V2 so that a detection voltage V3 is obtained. One example of combining is addition, and more specifically, it may be weighted addition. The combining unit 61 performs the operation shown in equation (1) below, for example. The coefficient α in the equation is a weighting coefficient (also called gain) that is multiplied by the sensor voltage V1. The coefficient β is a weighting coefficient that is multiplied by the sensor voltage V2. V3 = α × V1 + β × V2 (1)

[0040] Returning to Figure 1, the external unit 5 outputs the detection voltage V3 generated by the detection circuit 6. The output is directed to an external device 2 located outside the shield 3, one example of which is an oscilloscope. Based on the detection voltage V3 from the detection circuit 6, the waveform of the current I is displayed, and calculation results such as its maximum value, minimum value, and frequency are also displayed.

[0041] Here, as the frequency f of the current I increases, the likelihood of the skin effect occurring in conductor 9 increases. Hereafter, the skin effect of conductor 9 may simply be referred to as the skin effect.

[0042] When the skin effect is present, the distribution of the magnetic field H within shield 3 is different compared to when it is not present. Depending on the location within shield 3, even if the magnitude of the current I is the same, the magnitude of the magnetic field H at that location will vary depending on whether or not the skin effect is present.

[0043] Due to the skin effect, the frequency characteristics in the high-frequency range fluctuate, particularly the value of the sensor voltage V2 of the magnetic field sensor 42 that detects high-frequency magnetic fields, and consequently the value of the detected voltage V3. As a result, the measurement accuracy of the current I decreases. This problem is addressed by the disclosed technology. There are mainly two methods, which will be explained in turn.

[0044] <First Method> In the first method, the arrangement of magnetic field sensors 41 and 42 within the shield 3 is modified. This will be explained with reference to Figures 4 to 17.

[0045] Figure 4 shows an example of the schematic configuration of the current sensor 1. The arrangement of the magnetic field sensor 4 inside the shield 3 when viewed in the front-to-back direction (Z-axis direction) is schematically shown.

[0046] Magnetic field sensor 41 is positioned closer to the aperture 37 than magnetic field sensor 42. Magnetic field sensor 42 is positioned further from the aperture 37 than magnetic field sensor 41. Since the conductor 9 passes through the aperture 37, their positions can be considered almost the same. In this sense, the conductor 9 and the aperture 37 may be interpreted as appropriate. That is, it can also be said that magnetic field sensor 41 is positioned close to conductor 9. It can also be said that magnetic field sensor 42 is positioned far from conductor 9.

[0047] More specifically, the magnetic field sensor 41 is positioned in the vicinity of the conductor 9. The vicinity is the region where the magnitude of the magnetic field H fluctuates depending on the presence or absence of the skin effect. The magnetic field sensor 42 is positioned in the far region of the conductor 9. The far region is the region where the magnitude of the magnetic field H does not fluctuate depending on the presence or absence of the skin effect. Here, "the magnitude of the magnetic field H does not fluctuate" can be understood to mean including minute magnetic field fluctuations that have almost no effect (negligible) on the sensor voltage V2 of the magnetic field sensor 42. The vicinity and far regions will be explained with reference to Figure 5.

[0048] Figure 5 shows examples of the near-field and far-field regions. The horizontal axis of the graph represents the distance from the center of the conductor 9. The vertical axis of the graph represents the magnitude of the magnetic field H. Note that the magnitude of the magnetic field H may also be the magnetic flux density, and these can be interpreted as appropriate. The solid line graph shows the magnetic field H when the skin effect is not occurring (no skin effect). The dashed line graph shows the magnetic field H when the skin effect is occurring (with skin effect).

[0049] As can be understood, in the region near the surface of the conductor 9, the magnetic field H fluctuates depending on whether or not the skin effect is present. This region corresponds to the near-field region. In the region a certain distance from the surface of the conductor 9, the magnetic field H does not fluctuate depending on whether or not the skin effect is present. This region corresponds to the far-field region. In the example shown in Figure 5, the magnitude of the magnetic field H decreases in the near-field region due to the occurrence of the skin effect.

[0050] Returning to Figure 4, the magnetic field sensor 41 is positioned in the nearby region as described above and outputs a sensor voltage V1 corresponding to the magnetic field H at that location. The magnetic field sensor 42 is positioned in the distant region as described above and outputs a sensor voltage V2 corresponding to the magnetic field H at that location.

[0051] Figures 6 and 7 illustrate examples of operation. Figure 6 shows the magnetic field H inside the shield 3 when the skin effect is not occurring. The magnetic field H at the position of the magnetic field sensor 41 (nearby region) at this time is referred to as magnetic field H11 and is illustrated. The magnetic field H at the position of the magnetic field sensor 42 (far region) is referred to as magnetic field H21 and is illustrated. Figure 7 shows the magnetic field H inside the shield 3 when the skin effect is occurring. The magnetic field H at the position of the magnetic field sensor 41 at this time is referred to as magnetic field H12 and is illustrated. The magnetic field H at the position of the magnetic field sensor 42 is referred to as magnetic field H22 and is illustrated.

[0052] At the location of magnetic field sensor 41, the magnetic field H fluctuates depending on the presence or absence of the skin effect. Therefore, magnetic field H12 is different from magnetic field H11. At the location of magnetic field sensor 42, the magnetic field H does not fluctuate depending on the presence or absence of the skin effect. Therefore, magnetic field H22 is the same as magnetic field H21.

[0053] Based on the sensor voltages V1 and V2 of the magnetic field sensors 41 and 42 arranged as described above, the detection circuit 6 generates a detection voltage V3. The combining unit 61 of the detection circuit 6 combines the sensor voltages V1 and V2, for example, as shown in equation (1) described earlier, so that a detection voltage V3 can be obtained.

[0054] In one embodiment, the combining unit 61 of the detection circuit 6 may combine the sensor voltage V1 and sensor voltage V2 so that the frequency gain characteristic of the detected voltage V3 with respect to the current I is constant. This will be explained with reference to Figure 8.

[0055] Figure 8 shows an example of frequency characteristics. The horizontal axis of the graph represents the frequency f of the current I. The vertical axis of the graph represents the gain. The gain represents the gain up to the output portion of the detection circuit 6 (corresponding to the output portion of the combining unit 61) with respect to the current I.

[0056] The graph line Ce shows the frequency characteristics of the skin effect. Due to the skin effect, the detection level of the magnetic field is divided into a low-frequency region where the gain is constant and a high-frequency region where the gain decreases. The cutoff frequency is set between these two regions.

[0057] In the combining unit 61 (for example, Figure 3 above or Figure 11 below), a first-order low-pass filter is applied to the sensor voltage V1 as the cutoff frequency. Similarly, a first-order high-pass filter is applied to the sensor voltage V2 as the cutoff frequency.

[0058] Furthermore, in the combining unit 61, the gains of sensor voltages V1 and V2 are adjusted so that their detection voltages are at the same level. The signals of sensor voltages V1 and V2, whose levels have been adjusted, are added together and output as the detection voltage V3. As a result, a frequency characteristic with constant gain can be obtained, as shown by graph line V3 in Figure 8.

[0059] Since the sensor voltage V1 of the magnetic field sensor 41 is blocked in the frequency range higher than the cutoff frequency affected by the skin effect, the magnetic field sensor 41 is not affected by the skin effect even when placed near the aperture 37. Based on the sensor voltage V1 of the magnetic field sensor 41 placed near the conductor 9, the magnetic field H is detected accurately, and therefore the current I is measured accurately.

[0060] The sensor voltage V2 of the magnetic field sensor 42 is not affected by the skin effect because the magnetic field sensor 42 is located far from the aperture 37. The high-frequency range is secured by blocking the frequency range below the cutoff frequency and interpolating the frequency range blocked by the sensor voltage V1 of the magnetic field sensor 41. Since the position of the magnetic field sensor 42 (far region) is not affected by the skin effect, the magnetic field H is detected with greater accuracy than when it is located in the nearby region, and therefore the current I is measured with greater accuracy.

[0061] As explained above, by devising the arrangement of magnetic field sensors 41 and 42 within the shield 3, the decrease in measurement accuracy of the current I caused by the skin effect can be suppressed.

[0062] Figure 9 is a flowchart illustrating an example of the processing (current measurement method) performed in the current sensor 1. Explanations of content that overlaps with previous explanations will be omitted as appropriate.

[0063] In step S1, the magnetic field H is detected using magnetic field sensors 41 and 42. Magnetic field sensor 41 outputs a sensor voltage V1 corresponding to the magnetic field H at its location within the shield 3. Magnetic field sensor 42 outputs a sensor voltage V2 corresponding to the magnetic field H at its location within the shield 3.

[0064] In step S2, the current I is detected based on the detection results of the magnetic field sensor 41 and the magnetic field sensor 42. The detection circuit 6 located outside the shield 3 generates a detection voltage V3 indicating the current I based on the sensor voltage V1 from the magnetic field sensor 41 and the sensor voltage V2 from the magnetic field sensor 42.

[0065] <Determination of the presence or absence of epidermal effects> If it is possible to determine whether or not the skin effect is occurring in the conductor 9 (presence or absence of the skin effect), this could be a useful technology. An example of a determination method will be explained with reference to Figures 10 to 14.

[0066] Figure 10 shows an example of the schematic configuration of the current sensor 1. In this example, the magnetic field sensor 41 is configured to detect not only low-frequency magnetic fields but also high-frequency magnetic fields, and includes both an IC sensor and a coil sensor. The sensor voltage V1 of the magnetic field sensor 41 includes the sensor voltage V11 output by the IC sensor and the sensor voltage V12 output by the coil sensor. The magnetic field sensor 42 is configured to include a coil sensor as before and outputs a sensor voltage V2.

[0067] Figure 11 shows an example of the schematic configuration of the detection circuit 6. In addition to the synthesis unit 61, the detection circuit 6 further includes a determination unit 62.

[0068] The determination unit 62 determines whether or not the skin effect is occurring based on the sensor voltage V1 of the magnetic field sensor 41 and the sensor voltage V2 of the magnetic field sensor 42. More specifically, the determination unit 62 determines the presence or absence of the skin effect based on the ratio of the sensor voltage V12 of the coil sensor included in the magnetic field sensor 41 and the sensor voltage V2 of the coil sensor included in the magnetic field sensor 42. This ratio is referred to as ratio R. As an example, ratio R is assumed to be the ratio of sensor voltage V2 to sensor voltage V12 (i.e., R = V2 / V12).

[0069] Figures 12 and 13 show examples of determining the presence or absence of the skin effect. The horizontal axis of the graph in Figure 12 shows measurements under different conditions. Examples of conditions include the type of conductor 9 and the frequency f of the current I. In this example, five measurements under different conditions are shown as Measurements N1 to N5. The vertical axis of the graph shows the ratio R. The plots in the graph show the ratio R for each measurement.

[0070] The value of the ratio R is broadly classified into two values ​​depending on whether or not the skin effect is present. This is because the sensor voltage V12 of the magnetic field sensor 41 fluctuates depending on whether or not the skin effect is present, while the sensor voltage V2 of the magnetic field sensor 42 does not fluctuate. The value of the ratio R when the skin effect is not occurring is called the reference value R0.

[0071] When the skin effect occurs, the magnitude of the magnetic field H in the surrounding region fluctuates, and therefore the sensor voltage V12 of the magnetic field sensor 41 also fluctuates. The ratio R deviates from the reference value R0. For example, as explained earlier in Figure 5, when the magnitude of the magnetic field H in the surrounding region decreases, the ratio R increases and deviates from the reference value R0.

[0072] If the ratio R is close to (including identical to) the reference value R0, the detection circuit 6 determines that the skin effect is not occurring. Otherwise, i.e., if the ratio R is far from the reference value R0, the detection circuit 6 determines that the skin effect is occurring. To determine whether the ratio R is close to the reference value R0, for example, a threshold determination on the absolute difference between the ratio R and the reference value R0 (|R-R0|) may be used.

[0073] As shown in Figure 13, in measurements N1, N3, and N4, the ratio R is close to the reference value R0, so it is determined that no skin effect has occurred. Conversely, in measurements N2 and N5, the ratio R is far from the reference value R0, so it is determined that a skin effect has occurred.

[0074] Returning to Figure 11, we will now describe an example of how the determination result of the determination unit 62 can be used. In one embodiment, the detection circuit 6 may selectively use the sensor voltage V1 of the magnetic field sensor 41 and the sensor voltage V2 of the magnetic field sensor 42, depending on the determination result of the determination unit 62.

[0075] Specifically, when the skin effect is not occurring, the composite unit 61 generates a detection voltage V3 based on the sensor voltage V1 of the magnetic field sensor 41. The sensor voltage V2 of the magnetic field sensor 42 does not need to be used. By using the sensor voltage V1 of the magnetic field sensor 41, which is placed near the conductor 9, the magnetic field H is detected accurately, and therefore the current I is measured accurately.

[0076] On the other hand, when the skin effect occurs, the synthesis unit 61 generates a detection voltage V3 based on the sensor voltage V2 of the magnetic field sensor 42. The sensor voltage V1 of the magnetic field sensor 41 does not need to be used. Since the magnetic field sensor 42 is not affected by the skin effect, the magnetic field H is detected with high accuracy, and therefore the current I is measured with high accuracy.

[0077] Figure 14 is a flowchart illustrating an example of the process (current measurement method) performed in the current sensor 1. Explanations of content that overlaps with previous explanations will be omitted as appropriate.

[0078] In step S11, the magnetic field H is detected using magnetic field sensors 41 and 42. Magnetic field sensor 41 outputs sensor voltage V1, more specifically sensor voltages V11 and V12. Magnetic field sensor 42 outputs sensor voltage V2.

[0079] In step S12, it is determined whether or not the skin effect of the conductor 9 is occurring based on the detection results of the magnetic field sensor 41 and the detection results of the magnetic field sensor 42. The determination unit 62 of the detection circuit 6 determines the presence or absence of the skin effect based on the ratio R of the sensor voltages V12 and V2.

[0080] In step S13, the process branches according to the result of the determination in step S12. If the skin effect of conductor 9 occurs (step S13: Yes), the process proceeds to step S15. Otherwise (step S13: No), the process proceeds to step S14.

[0081] In step S14, the current I is detected based on the detection result of the magnetic field sensor 41. The determination unit 62 of the detection circuit 6 generates a detection voltage V3 based on the sensor voltage V1 of the magnetic field sensor 41 (for example, only the sensor voltage V11 of the IC sensor).

[0082] In step S15, the current I is detected based on the detection result of the magnetic field sensor 42. The determination unit 62 of the detection circuit 6 generates a detection voltage V3 based on the sensor voltage V2 of the magnetic field sensor 42.

[0083] <Sensor movement> In one embodiment, the magnetic field sensor 42 may be dynamically positioned near or far from the opening 37 within the shield 3. This will be explained with reference to Figure 15.

[0084] Figure 15 shows an example of the schematic configuration of the current sensor 1. The magnetic field sensor 41 is positioned near the opening 37. The magnetic field sensor 42 is movable within the shield 3 and can be positioned near the opening 37 or farther away from the opening 37.

[0085] The current sensor 1 includes a moving mechanism 7 for moving the magnetic field sensor 4, more specifically, the magnetic field sensor 42. The moving mechanism 7 moves the magnetic field sensor 42 between a position near the opening 37 and a position far from the opening 37. The specific configuration of the moving mechanism 7 is not particularly limited, and any configuration that can physically move the magnetic field sensor 42 may be employed. For example, the moving mechanism 7 may include a support part for supporting the magnetic field sensor 42 and a drive part (actuator, etc.) for moving the support part.

[0086] The moving mechanism 7 moves the magnetic field sensor 42 so that when the skin effect is not present, the magnetic field sensor 42 is positioned near the opening 37, and when the skin effect is present, the magnetic field sensor 42 is positioned far from the opening 37. The presence or absence of the skin effect is determined by the detection circuit 6, as described above.

[0087] The movement of the magnetic field sensor 42 by the moving mechanism 7 may be controlled by the detection circuit 6. See also Figure 16 for further explanation.

[0088] Figure 16 shows an example of the schematic configuration of the detection circuit 6. The detection circuit 6 further includes a control unit 63. The control unit 63 controls the moving mechanism 7. For example, the control unit 63 generates a control signal and transmits it to the moving mechanism 7, and the moving mechanism 7 moves the magnetic field sensor 42 according to that control signal.

[0089] The determination result of the determination unit 62 may also be used in the control of the moving mechanism 7 by the control unit 63. In that case, the control unit 63 controls the moving mechanism 7 based on the determination result of the determination unit 62. Specifically, the control unit 63 controls the moving mechanism 7 so that the magnetic field sensor 42 is positioned near the opening 37 when the skin effect is not occurring, and the magnetic field sensor 42 is positioned at the opening 37 when the skin effect is occurring.

[0090] Figure 17 is a flowchart illustrating an example of the process (current measurement method) performed in the current sensor 1. Explanations of content that overlaps with previous explanations will be omitted as appropriate.

[0091] In step S21, it is determined whether or not the skin effect of the conductor 9 is occurring. This determination is made by the determination unit 62 of the detection circuit 6. If the skin effect is occurring (step S21: Yes), the process proceeds to step S22. Otherwise (step S21: No), the process proceeds to step S23.

[0092] In step S22, the magnetic field sensor 42 is positioned near the opening 37. The control unit 63 of the detection circuit 6 generates a control signal for this purpose and transmits it to the moving mechanism 7. The moving mechanism 7 moves the magnetic field sensor 42 so that it is positioned near the opening 37. If the magnetic field sensor 42 is already positioned near the opening 37, this step S22 may be skipped.

[0093] In step S23, the magnetic field sensor 42 is positioned far from the opening 37. The control unit 63 generates a control signal for this purpose and transmits it to the moving mechanism 7. The moving mechanism 7 moves the magnetic field sensor 42 so that it is positioned far from the opening 37. If the magnetic field sensor 42 is already positioned far from the opening 37, this step S23 may be skipped.

[0094] After the processing in step S22 or step S23 is completed, the processing proceeds in the order of steps S24 and S25. These processes may be the same as the processes in steps S1 and S2 of Figure 9, which will be explained earlier. That is, the magnetic field H is detected using magnetic field sensors 41 and 42, and the current I is detected based on the detection results of magnetic field sensor 41 and magnetic field sensor 42.

[0095] As explained above, in the first method, the reduction in measurement accuracy of the current I caused by the skin effect can be suppressed by devising the arrangement of the magnetic field sensors 41 and 42 within the shield 3.

[0096] <Second Method> In the second method, the detection voltage V3 output by the detection circuit 6 is corrected. This will be explained with reference to Figures 18 to 24.

[0097] Figure 18 shows an example of the schematic configuration of the current sensor 1. The magnetic field sensor 41, which detects low-frequency magnetic fields, and the magnetic field sensor 42, which detects high-frequency magnetic fields, are both positioned near the aperture 37. The sensor voltage V2 of the magnetic field sensor 42 is affected by the skin effect.

[0098] Figure 19 shows an example of the schematic configuration of the detection circuit 6 and the external device 2. The detection circuit 6 includes a combining unit 61 and generates a detection voltage V3 based on sensor voltages V1 and V2. Since the sensor voltage V2 fluctuates depending on the presence or absence of the skin effect, the detection voltage V3 also fluctuates. The detection voltage V3 is corrected by the external device 2 to eliminate this fluctuation in the detection voltage V3.

[0099] External device 2 corrects the detected voltage V3. External device 2 includes a processing unit 22 in addition to the input terminal 21 and display unit 23 mentioned above.

[0100] The detection voltage V3 from the detection circuit 6 is input to input terminal 21. As mentioned earlier, the detection voltage V3 represents the value of the current I, more specifically, its instantaneous value. The detection voltage V3 corresponding to the instantaneous value of the constantly changing current I is input to input terminal 21.

[0101] The processing unit 22 corrects the detected voltage V3 so as to remove the skin effect, i.e., the fluctuations in the detected voltage V3 caused by fluctuations in the sensor voltage V2. For example, in the processing unit 22, the detected voltage V3 is converted into digital data, and various data processing is performed on it. A storage unit for storing the various data necessary for processing may also be included in the external device 2.

[0102] The processing unit 22 may be configured to include, for example, a general-purpose or dedicated processor, memory, etc. The functions of the processing unit 22 may be realized by hardware design, by software design, or by both hardware and software design. A program for causing the processing unit 22 to perform various processes is also one of the disclosed technologies.

[0103] Specifically, the processing unit 22 corrects the detected voltage V3 in the frequency domain. In the example shown in Figure 19, the processing unit 22 includes a waveform generation unit 221, a Fourier transform unit 222, a correction unit 223, and an inverse Fourier transform unit 224.

[0104] The waveform generation unit 221 generates the waveform of the detected voltage V3. This waveform of the detected voltage V3 is the waveform before correction by the processing unit 22. An example will be explained with reference to Figure 20.

[0105] Figure 20 shows an example of the waveform of the detected voltage V3 before correction. The horizontal axis of the graph represents time. The vertical axis of the graph represents the detected voltage V3. This waveform of the detected voltage V3 is affected by the skin effect (for example, the waveform is degraded), so it does not accurately represent the waveform of the current I.

[0106] Returning to Figure 19, the Fourier transform unit 222 performs a Fourier transform on the waveform of the detected voltage V3 generated by the waveform generation unit 221. This yields the frequency components of the detected voltage V3. The frequency components may include the amplitude values ​​for each frequency, and may also include the phase for each frequency. These frequency components of the detected voltage V3 are the frequency components before correction by the processing unit 22. An example will be explained with reference to Figure 21.

[0107] Figure 21 shows an example of the frequency components of the detected voltage V3 before correction. The horizontal axis of the graph represents frequency. The vertical axis of the graph represents component A3. Component A3 can be understood to include both amplitude and phase components. Because the frequency components of this detected voltage V3 are affected by the skin effect, they do not accurately represent the frequency components of the current I.

[0108] Returning to Figure 19, the correction unit 223 corrects the frequency components of the detected voltage V3 obtained by the Fourier transform in the Fourier transform unit 222. Specifically, the correction unit 223 corrects the frequency components of the detected voltage V3 by adding or multiplying them with a correction value. The correction value may include an amplitude correction value for correcting the amplitude and a phase correction value for correcting the phase. For example, the amplitude correction value is multiplied by the amplitude component of the detected voltage V3, and the phase correction value is added to the phase component of the detected voltage V3. An example will be explained with reference to Figure 22.

[0109] Figure 22 shows an example of correcting the frequency components of the detected voltage V3. The graph in the upper left of Figure 22 shows the frequency components of the detected voltage V3 before correction, which is the same as the graph in Figure 21 explained earlier.

[0110] The graph in the lower left of Figure 22 shows the correction values ​​(amplitude correction value and phase correction value). The correction values ​​are determined based on the frequency characteristics of the detected voltage V3 due to the skin effect. For example, the amount of fluctuation (amplitude and phase fluctuation) of the detected voltage V3 in the frequency domain when the skin effect occurs is measured in advance. A correction value to cancel out this fluctuation is calculated and stored in the memory unit of the external device 2 so that it can be used in the correction unit 223. The frequency components of the detected voltage V3 are corrected using this correction value. The graph on the right of Figure 22 shows the frequency components of the corrected detected voltage V3. Since the effect of the skin effect has been removed, the frequency components of this detected voltage V3 accurately represent the frequency components of the current I.

[0111] Returning to Figure 19, the Fourier inverse transform unit 224 performs an inverse Fourier transform on the frequency components of the detected voltage V3 after correction by the correction unit 223. This yields the waveform of the detected voltage V3. This waveform of the detected voltage V3 is free from the effects of the skin effect and accurately represents the waveform of the current I. An example will be explained with reference to Figure 23.

[0112] Figure 23 shows an example of the inverse Fourier transform. The graph on the left of Figure 23 shows the frequency components of the corrected detection voltage V3, which is the same as the graph on the right of Figure 22 described earlier. The right side of Figure 23 shows the waveform of the detection voltage V3 obtained by the inverse Fourier transform. This waveform of the detection voltage V3 is the waveform of the corrected detection voltage V3, and is different from the waveform of the detection voltage V3 before correction shown in Figure 20 described earlier (for example, the waveform degradation has been eliminated).

[0113] Returning to Figure 19, the display unit 23 displays the waveform of the detected voltage V3 after correction by the processing unit 22 as the waveform of the current I. The accurate measurement result of the current I, with the effects of the skin effect removed, is displayed.

[0114] As explained above, correcting the detected voltage V3 with the external device 2 can also suppress the decrease in measurement accuracy of the current I caused by the skin effect.

[0115] Figure 24 is a flowchart illustrating an example of the process (current measurement method) performed in the current measuring device 100. Explanations of content that overlaps with previous explanations will be omitted as appropriate.

[0116] In step S31, the magnetic field H is detected using the magnetic field sensor 4. Magnetic field sensors 41 and 42, positioned near the opening 37, output sensor voltages V1 and V2, respectively, corresponding to the magnetic field H at their respective locations.

[0117] In step S32, a waveform is generated based on the detection result of the magnetic field sensor 4. The detection circuit 6 generates a detection voltage V3 based on the sensor voltages V1 and V2. The waveform generation unit 221 of the processing unit 22 of the external device 2 generates the waveform of the detection voltage V3.

[0118] In step S33, the waveform is Fourier transformed. The Fourier transform unit 222 of the processing unit 22 of the external device 2 performs a Fourier transform on the waveform of the detected voltage V3. The frequency components of the detected voltage V3 are obtained.

[0119] In step S34, the frequency components are corrected. The correction unit 223 of the processing unit 22 of the external device 2 corrects the frequency components of the detected voltage V3 using the correction value.

[0120] In step S35, the corrected frequency components are subjected to an inverse Fourier transform. The inverse Fourier transform unit 224 of the processing unit 22 of the external device 2 performs an inverse Fourier transform on the frequency components of the corrected detected voltage V3. The waveform of the corrected detected voltage V3 is obtained.

[0121] In step S36, the waveform is displayed. The display unit 23 of the external device 2 displays the waveform of the corrected detected voltage V3.

[0122] As explained above, in the second method, the decrease in measurement accuracy of the current I caused by the skin effect can be suppressed by correcting the detection voltage V3 output by the detection circuit 6.

[0123] <Summary> The technology described above can be identified, for example, as follows. One of the disclosed technologies is a current sensor 1. As described with reference to Figures 1 to 17, the current sensor 1 comprises a shield 3 having an opening 37 for taking in a magnetic field H generated by a current I flowing through a conductor 9, a magnetic field sensor 4 disposed inside the shield 3 and outputting a sensor voltage corresponding to the magnetic field H at its location, and a detection circuit 6 disposed outside the shield 3 and detecting the current I based on the sensor voltage of the magnetic field sensor 4. The magnetic field sensor 4 includes a magnetic field sensor 41 (first magnetic field sensor) for detecting low-frequency magnetic fields and a magnetic field sensor 42 (second magnetic field sensor) for detecting high-frequency magnetic fields. The magnetic field sensor 41 is positioned closer to the opening 37 than the magnetic field sensor 42, and the magnetic field sensor 42 is positioned further from the opening 37 than the magnetic field sensor 41. More specifically, the magnetic field sensor 41 is positioned in the vicinity of the conductor 9, and the magnetic field sensor 42 is positioned in the far region of the conductor 9. The vicinity is a region where the magnitude of the magnetic field H fluctuates depending on the presence or absence of the skin effect of the conductor 9, while the far region may be a region where the magnitude of the magnetic field H does not fluctuate depending on the presence or absence of the skin effect of the conductor 9.

[0124] According to the current sensor 1 described above, the magnetic field sensor 42, which detects high-frequency magnetic fields, is positioned further away from the aperture 37 than the magnetic field sensor 41, which detects low-frequency magnetic fields. The magnetic field sensor 42 is not affected by the skin effect of the conductor 9. When the frequency f of the current I is high and the skin effect occurs, the sensor voltage V2 of the magnetic field sensor 42, which detects high-frequency magnetic fields, becomes dominant in the sensor voltage of the magnetic field sensor 4. The current I is detected based on this sensor voltage. Therefore, the decrease in the measurement accuracy of the current I due to the skin effect can be suppressed.

[0125] As explained with reference to Figures 10 to 14, the detection circuit 6 determines whether or not the skin effect of the conductor 9 is occurring based on the sensor voltage of the magnetic field sensor 4. If the skin effect of the conductor 9 is not occurring, it detects the current I based on the sensor voltage V1 of the magnetic field sensor 41. If the skin effect of the conductor 9 is occurring, it may detect the current I based on the sensor voltage V2 of the magnetic field sensor 42. This allows the current I to be measured by selectively using the sensor voltage V1 of the magnetic field sensor 41 and the sensor voltage V2 of the magnetic field sensor 42, depending on the presence or absence of the skin effect.

[0126] As explained with reference to Figures 10 to 14, the magnetic field sensor 41 also detects high-frequency magnetic fields, and each of the magnetic field sensors 41 and 42 includes a coil sensor for detecting high-frequency magnetic fields. The detection circuit 6 may determine whether or not the skin effect of the conductor 9 is occurring based on the sensor voltage V12 of the coil sensor of the magnetic field sensor 41 and the sensor voltage V2 of the coil sensor of the magnetic field sensor 42 (for example, based on their ratio R). For example, the presence or absence of the skin effect of the conductor 9 can be determined in this way.

[0127] The current sensor 1, described with reference to Figures 1 to 3 and Figures 15 to 17, is also one of the disclosed technologies. The current sensor 1 comprises a shield 3 having an opening 37 for taking in a magnetic field H generated by a current I flowing through a conductor 9; a magnetic field sensor 4 disposed inside the shield 3 and outputting a sensor voltage corresponding to the magnetic field H at that location; a detection circuit 6 disposed outside the shield 3 and detecting the current I based on the sensor voltage of the magnetic field sensor 4; and a moving mechanism 7 for moving the magnetic field sensor 4. The magnetic field sensor 4 is disposed near the opening 37 and includes a magnetic field sensor 41 (first magnetic field sensor) for detecting low-frequency magnetic fields and a magnetic field sensor 42 (second magnetic field sensor) for detecting high-frequency magnetic fields. The moving mechanism 7 moves the magnetic field sensor 42 between a position near the opening 37 and a position far from the opening 37. In this case, the detection circuit 6 determines whether or not the skin effect of the conductor 9 is occurring based on the sensor voltage of the magnetic field sensor 4, and the moving mechanism 7 may move the magnetic field sensor 42 so that when the skin effect of the conductor 9 is not occurring, the magnetic field sensor 42 is positioned near the opening 37, and when the skin effect of the conductor 9 is occurring, the magnetic field sensor 42 is positioned far from the opening 37. This configuration, in which the magnetic field sensor 42 is movable, also allows the magnetic field sensor 42 to be positioned far from the opening 37, thereby suppressing the decrease in measurement accuracy of the current I caused by the skin effect, as explained above.

[0128] The current measuring device 100, described with reference to Figures 1 to 3 and Figures 18 to 24, is also one of the disclosed technologies. The current measuring device 100 comprises a shield 3 having an opening 37 for taking in a magnetic field H generated by a current I flowing through a conductor 9, a magnetic field sensor 4 disposed inside the shield 3 and outputting a sensor voltage corresponding to the magnetic field H at its location, a detection circuit 6 disposed outside the shield 3 and generating a detection voltage V3 indicating the value of the current I based on the sensor voltage of the magnetic field sensor 4, and an external device 2 disposed outside the shield 3 and correcting the detection voltage V3 in the frequency domain. More specifically, the sensor voltage (for example, the sensor voltage V2 of the magnetic field sensor 42) fluctuates due to the skin effect of the conductor 9, the detection voltage V3 fluctuates due to the fluctuation of the sensor voltage, and the external device 2 may correct the detection voltage V3 to eliminate the fluctuation of the detection voltage V3. The external device 2 may include a waveform generation unit 221 that generates the waveform of the detected voltage V3, a Fourier transform unit 222 that performs a Fourier transform on the waveform of the detected voltage V3, a correction unit 223 that corrects the frequency components of the detected voltage V3 obtained by the Fourier transform, and an inverse Fourier transform unit 224 that performs an inverse Fourier transform on the frequency components of the corrected detected voltage V3. For example, by correcting the detected voltage V3 output by the detection circuit 6 in the frequency domain in this way, the decrease in measurement accuracy of the current I caused by the skin effect can be suppressed.

[0129] A current measurement method is also one of the disclosed technologies. The current measurement method includes detecting a magnetic field H at a given location using a magnetic field sensor 4 placed inside a shield 3 having an opening 37 for taking in the magnetic field H generated by the current I flowing through the conductor 9 (for example, step S1 in Figure 9), and detecting the current I based on the detection result of the magnetic field sensor 4 (for example, step S2 in Figure 9). The magnetic field sensor 4 includes magnetic field sensor 41 and magnetic field sensor 42, as described above. Such a current measurement method also makes it possible to suppress the decrease in measurement accuracy of the current I caused by the skin effect, as described above.

[0130] Some examples of the combinations of technical features that will be disclosed are listed below. (1) A shield having an opening for taking in the magnetic field generated by the electric current flowing through the conductor, A magnetic field sensor, which is placed inside the shield and outputs a sensor voltage corresponding to the magnetic field at that location, A detection circuit, located outside the shield, detects the current based on the sensor voltage of the magnetic field sensor, Equipped with, The aforementioned magnetic field sensor is A first magnetic field sensor for detecting low-frequency magnetic fields, A second magnetic field sensor for detecting high-frequency magnetic fields, Includes, The first magnetic field sensor is positioned closer to the opening than the second magnetic field sensor. The second magnetic field sensor is positioned further away from the aperture than the first magnetic field sensor. Current sensor. (2) The first magnetic field sensor is positioned in the vicinity of the conductor, The second magnetic field sensor is positioned in the far region of the conductor, The aforementioned neighboring region is a region in which the magnitude of the magnetic field fluctuates depending on the presence or absence of the skin effect of the conductor. The aforementioned far-field region is a region in which the magnitude of the magnetic field does not fluctuate depending on the presence or absence of the skin effect of the conductor. (1) The current sensor described above. (3) The detection circuit is Based on the sensor voltage of the magnetic field sensor, it is determined whether or not the skin effect of the conductor is occurring. When the skin effect of the conductor is not occurring, the current is detected based on the sensor voltage of the first magnetic field sensor. When the skin effect of the conductor occurs, the current is detected based on the sensor voltage of the second magnetic field sensor. (1) or (2) the current sensor described above. (4) The first magnetic field sensor also detects high-frequency magnetic fields. Each of the first magnetic field sensor and the second magnetic field sensor includes a coil sensor for detecting a high-frequency magnetic field. The detection circuit determines whether or not the skin effect of the conductor is occurring based on the sensor voltage of the coil sensor of the first magnetic field sensor and the sensor voltage of the coil sensor of the second magnetic field sensor. (3) The current sensor described above. (5) The detection circuit determines whether or not the skin effect of the conductor is occurring based on the ratio of the sensor voltage of the coil sensor of the first magnetic field sensor and the sensor voltage of the coil sensor of the second magnetic field sensor. (4) The current sensor described above. (6) A shield having an opening for taking in the magnetic field generated by the electric current flowing through the conductor, A magnetic field sensor, which is placed inside the shield and outputs a sensor voltage corresponding to the magnetic field at that location, A detection circuit, located outside the shield, detects the current based on the sensor voltage of the magnetic field sensor, A moving mechanism for moving the magnetic field sensor, Equipped with, The aforementioned magnetic field sensor is A first magnetic field sensor is positioned near the aforementioned opening and detects low-frequency magnetic fields, A second magnetic field sensor for detecting high-frequency magnetic fields, Includes, The moving mechanism moves the second magnetic field sensor between a position near the opening and a position far from the opening. Current sensor. (7) The detection circuit determines whether or not the skin effect of the conductor is occurring based on the sensor voltage of the magnetic field sensor. The moving mechanism moves the second magnetic field sensor such that when the skin effect of the conductor is not occurring, the second magnetic field sensor is positioned near the opening, and when the skin effect of the conductor is occurring, the second magnetic field sensor is positioned far from the opening. (6) The current sensor described above. (8) A shield having an opening for taking in the magnetic field generated by the electric current flowing through the conductor, A magnetic field sensor, which is placed inside the shield and outputs a sensor voltage corresponding to the magnetic field at that location, A detection circuit, positioned outside the shield, generates a detection voltage indicating the value of the current based on the sensor voltage of the magnetic field sensor, An external device, positioned outside the shield, for correcting the detected voltage in the frequency domain, Equipped with, Current measuring device. (9) The sensor voltage fluctuates due to the skin effect of the conductor. The detected voltage fluctuates due to fluctuations in the sensor voltage. The external device corrects the detected voltage to eliminate fluctuations in the detected voltage. (8) The current measuring device described above. (10) The external device is, A waveform generation unit that generates the waveform of the detected voltage, A Fourier transform unit that performs a Fourier transform on the waveform of the detected voltage, A correction unit for correcting the frequency component of the detected voltage obtained by the Fourier transform, A Fourier inverse transform unit that performs an inverse Fourier transform on the frequency components of the corrected detected voltage, including, (8) or (9) The current measuring device described above. (11) This involves detecting the magnetic field at a given location using a magnetic field sensor placed inside a shield that has an opening for capturing the magnetic field generated by the electric current flowing through the conductor, and Based on the detection result of the magnetic field sensor, the current is detected, including, A method for measuring electric current, The magnetic field sensor is A first magnetic field sensor for detecting low-frequency magnetic fields, A second magnetic field sensor for detecting high-frequency magnetic fields, Includes, The first magnetic field sensor is positioned closer to the opening than the second magnetic field sensor. The second magnetic field sensor is positioned further away from the aperture than the first magnetic field sensor. Current measurement method. [Explanation of Symbols]

[0131] 1 Current sensor 2 External device 3 Shields 30 internal space 31 Bottom plate 32 Top plate 33 Side panel 34 Side panel 35 Side panel 36 Side panels 37 Opening 38 terminals 4. Magnetic field sensor 41 Magnetic field sensor 42 Magnetic field sensor 5 External Units 6. Detection circuit 61 Synthesis section 62 Judgment section 63 Control Unit 7 Moving mechanism 9 Conductors H magnetic field H11 Magnetic Field H12 Magnetic Field H21 Magnetic Field H22 Magnetic Field I current V1 Sensor Voltage V11 Sensor Voltage V12 Sensor Voltage V2 sensor voltage W1 Wiring

Claims

1. A shield having an opening for taking in the magnetic field generated by the electric current flowing through the conductor, A magnetic field sensor, which is placed inside the shield and outputs a sensor voltage corresponding to the magnetic field at that location, A detection circuit, located outside the shield, detects the current based on the sensor voltage of the magnetic field sensor, Equipped with, The magnetic field sensor is A first magnetic field sensor for detecting low-frequency magnetic fields, A second magnetic field sensor for detecting high-frequency magnetic fields, Includes, The first magnetic field sensor is positioned closer to the opening than the second magnetic field sensor. The second magnetic field sensor is positioned further away from the opening than the first magnetic field sensor. Current sensor.

2. The first magnetic field sensor is positioned in the vicinity of the conductor, The second magnetic field sensor is positioned in the far region of the conductor, The aforementioned neighboring region is a region in which the magnitude of the magnetic field fluctuates depending on the presence or absence of the skin effect of the conductor. The aforementioned far-field region is a region in which the magnitude of the magnetic field does not fluctuate depending on the presence or absence of the skin effect of the conductor. The current sensor according to claim 1.

3. The detection circuit is Based on the sensor voltage of the magnetic field sensor, it is determined whether or not the skin effect of the conductor is occurring. When the skin effect of the conductor is not occurring, the current is detected based on the sensor voltage of the first magnetic field sensor. When the skin effect of the conductor occurs, the current is detected based on the sensor voltage of the second magnetic field sensor. The current sensor according to claim 1 or 2.

4. The first magnetic field sensor also detects high-frequency magnetic fields. Each of the first magnetic field sensor and the second magnetic field sensor includes a coil sensor for detecting a high-frequency magnetic field. The detection circuit determines whether or not the skin effect of the conductor is occurring based on the sensor voltage of the coil sensor of the first magnetic field sensor and the sensor voltage of the coil sensor of the second magnetic field sensor. The current sensor according to claim 3.

5. The detection circuit determines whether or not the skin effect of the conductor is occurring based on the ratio of the sensor voltage of the coil sensor of the first magnetic field sensor to the sensor voltage of the coil sensor of the second magnetic field sensor. The current sensor according to claim 4.

6. A shield having an opening for taking in the magnetic field generated by the electric current flowing through the conductor, A magnetic field sensor, which is placed inside the shield and outputs a sensor voltage corresponding to the magnetic field at that location, A detection circuit, located outside the shield, detects the current based on the sensor voltage of the magnetic field sensor, A moving mechanism for moving the magnetic field sensor, Equipped with, The magnetic field sensor is A first magnetic field sensor is positioned near the opening and detects low-frequency magnetic fields, A second magnetic field sensor for detecting high-frequency magnetic fields, Includes, The moving mechanism moves the second magnetic field sensor between a position near the opening and a position far from the opening. Current sensor.

7. The detection circuit determines whether or not the skin effect of the conductor is occurring based on the sensor voltage of the magnetic field sensor. The moving mechanism moves the second magnetic field sensor such that when the skin effect of the conductor is not occurring, the second magnetic field sensor is positioned near the opening, and when the skin effect of the conductor is occurring, the second magnetic field sensor is positioned far from the opening. The current sensor according to claim 6.

8. A shield having an opening for taking in the magnetic field generated by the electric current flowing through the conductor, A magnetic field sensor, which is placed inside the shield and outputs a sensor voltage corresponding to the magnetic field at that location, A detection circuit, positioned outside the shield, generates a detection voltage indicating the value of the current based on the sensor voltage of the magnetic field sensor, An external device, positioned outside the shield, for correcting the detected voltage in the frequency domain, Equipped with, Current measuring device.

9. The sensor voltage fluctuates due to the skin effect of the conductor. The detected voltage fluctuates due to fluctuations in the sensor voltage. The external device corrects the detected voltage to eliminate fluctuations in the detected voltage. The current measuring device according to claim 8.

10. The external device is, A waveform generation unit that generates the waveform of the detected voltage, A Fourier transform unit that performs a Fourier transform on the waveform of the detected voltage, A correction unit for correcting the frequency component of the detected voltage obtained by the Fourier transform, A Fourier inverse transform unit that performs an inverse Fourier transform on the frequency components of the corrected detected voltage, including, The current measuring device according to claim 8 or 9.

11. This involves detecting the magnetic field at a given location using a magnetic field sensor placed inside a shield that has an opening for capturing the magnetic field generated by the electric current flowing through the conductor, and Based on the detection result of the magnetic field sensor, the current is detected, including, A method for measuring electric current, The magnetic field sensor is A first magnetic field sensor for detecting low-frequency magnetic fields, A second magnetic field sensor for detecting high-frequency magnetic fields, Includes, The first magnetic field sensor is positioned closer to the opening than the second magnetic field sensor. The second magnetic field sensor is positioned further away from the opening than the first magnetic field sensor. Current measurement method.

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