Current sensor

Abstract

Provided is an electric current sensor comprising: a first bus bar (10A), a second bus bar (10B), and a third bus bar (10C) through which a three-phase AC current flows; a first sensor unit (20A) having a first magnetic detection element (30A) and a second magnetic detection element (30B); and a second sensor unit (20B) having a third magnetic detection element (30C) and a fourth magnetic detection element (30D), the first sensor unit (20A) being disposed between two bus bars other than one arbitrary bus bar to be measured from among the first through third bus bars, the second sensor unit (20B) having as a measurement object one of the two bus bars other than the one bus bar to be measured, and being disposed between the one bus bar to be measured and the other of the two bus bars other than the one bus bar to be measured, the distance between the first magnetic detection element (30A) and the one of the two bus bars other than the one bus bar to be measured and the distance between the second magnetic detection element (30B) and the other of the two bus bars other than the one bus bar to be measured being substantially equal, and the distance between the third magnetic detection element (30C) and the other of the two bus bars other than the one bus bar to be measured and the distance between the fourth magnetic detection element (30D) and the one bus bar to be measured being substantially equal.

Description

[Technical Field]

[0001] This invention relates to a current sensor. [Background technology]

[0002] Japanese Patent Publication No. 2008-58035 (Patent Document 1) is a prior art document disclosing the configuration of a current measuring device. The current measuring device described in Patent Document 1 measures the current value of each of three conductors through which a current that sums to zero flows. The current measuring device comprises first and second coreless current sensors, a holding means, a calculation means, and a shielding member. The first and second coreless current sensors are positioned at predetermined relative positions with respect to the three conductors. The holding means acquires and holds the coefficients necessary for measurement in a preparation stage before measuring the current flowing through the three conductors. The calculation means calculates the current value flowing through each conductor based on the output signals of the first and second coreless current sensors and the coefficients held by the holding means, utilizing the fact that the sum of the current values ​​flowing through the three conductors is zero. The shielding member surrounds each conductor and the first and second coreless current sensors. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-58035 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In the current measuring device described in Patent Document 1, a shielding member is provided, which increases the size of the device and reduces the accuracy of current measurement due to the influence of the shielding member. Furthermore, since the current value of each conductor is calculated based on pre-acquired parameters, the device requires complex calculations. As a result, the calculation time for the current value increases, reducing the responsiveness of current measurement.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a current sensor that can improve measurement accuracy and responsiveness while reducing the overall size. [Means for solving the problem]

[0006] The current sensor according to the present invention comprises a first busbar, a second busbar, and a third busbar, a first sensor unit, a second sensor unit, and a calculation unit. The first busbar, the second busbar, and the third busbar each extend in a first direction with a distance between them and are aligned in a second direction perpendicular to the first direction, and a three-phase alternating current flows through them. The first sensor unit is positioned between two busbars other than any one of the first, second, and third busbars to be measured. The second sensor unit measures one of the two busbars other than the busbar to be measured and is positioned between the busbar to be measured and the other of the two busbars other than the busbar to be measured. The calculation unit calculates the current values ​​of the first, second, and third busbars from the output values ​​of the first and second sensor units, respectively. The first sensor unit includes a first magnetic detection element and a second magnetic detection element. The first magnetic detection element and the second magnetic detection element each have a sensitivity axis oriented in a third direction perpendicular to the first and second directions, are aligned in the second direction, and detect magnetic fields generated by currents flowing through the first, second, and third busbars. The second sensor unit includes a third magnetic detection element and a fourth magnetic detection element. The third and fourth magnetic detection elements each have a sensitivity axis oriented in a third direction, are aligned in the second direction, and detect magnetic fields generated by currents flowing through the first, second, and third busbars. Viewed from the first direction, the distance between the first magnetic detection element and one of the two busbars other than the busbar being measured, and the distance between the second magnetic detection element and the other of the two busbars other than the busbar being measured, are approximately equidistant. Viewed from the first direction, the distance between the third magnetic detection element and the other of the two busbars other than the busbar being measured, and the distance between the fourth magnetic detection element and the busbar being measured, are approximately equidistant.The calculation unit can calculate the current value flowing through the bus bar of one measurement target based on the differential output value between the measurement value of the first magnetic detection element and the measurement value of the second magnetic detection element in the first sensor unit, and based on the differential output value between the measurement value of the third magnetic detection element and the measurement value of the fourth magnetic detection element in the second sensor unit, it can calculate the current value flowing through one of the two bus bars other than the bus bar of one measurement target, and by adding the current value flowing through the bus bar of one measurement target and the current value flowing through one of the two bus bars other than the bus bar of one measurement target, it can calculate the current value flowing through the other of the two bus bars other than the bus bar of one measurement target.

Advantages of the Invention

[0007] According to the present invention, while reducing the overall size of the current sensor, the measurement accuracy and responsiveness can be improved.

Brief Description of the Drawings

[0008] [Figure 1] It is a perspective view showing the configuration of the current sensor according to Embodiment 1 of the present invention. [Figure 2] It is a cross-sectional view showing the configuration of the current sensor according to Embodiment 1 of the present invention. [Figure 3] It is a block diagram showing the electrical connection of each component in the current sensor according to Embodiment 1 of the present invention. [Figure 4] It is a cross-sectional view showing the state where the magnetic field generated from each bus bar in the current sensor according to Embodiment 1 of the present invention is detected by the first magnetic detection element of the first sensor unit. [Figure 5] It is a cross-sectional view showing the state where the magnetic field generated from each bus bar in the current sensor according to Embodiment 1 of the present invention is detected by the second magnetic detection element of the first sensor unit. [Figure 6] It is a circuit diagram schematically showing the circuit configuration of the current sensor according to Embodiment 1 of the present invention. [Figure 7] It is a cross-sectional view showing the configuration of the current sensor according to Embodiment 2 of the present invention.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the current sensor according to each embodiment of the present invention will be described with reference to the drawings. In the following description of the embodiments, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

[0010] In the drawings, the direction in which the busbars are arranged is the X direction as the second direction, the direction in which each busbar extends is the Y direction as the first direction, and the direction along the sensitivity axis of each magnetic detection element is the Z direction as the third direction. Also, the distance between the components in the current sensor is the distance connecting the centers of the components.

[0011] (Embodiment 1) FIG. 1 is a perspective view showing the configuration of the current sensor according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the current sensor according to Embodiment 1 of the present invention. FIG. 3 is a block diagram showing the electrical connection of each component in the current sensor according to Embodiment 1 of the present invention.

[0012] As shown in FIGS. 1 to 3, the current sensor 1 according to Embodiment 1 of the present invention includes a first busbar 10A, a second busbar 10B, a third busbar 10C, a first sensor unit 20A, a second sensor unit 20B, and a calculation unit 40.

[0013] The first busbar 10A, the second busbar 10B, and the third busbar 10C are three-phase three-wire busbars. A three-phase alternating current flows through each of the first busbar 10A, the second busbar 10B, and the third busbar 10C. The currents flowing through the first busbar 10A, the second busbar 10B, and the third busbar 10C constitute alternating currents having equal amplitudes and phase-shifted from each other by 120° each.

[0014] In the first busbar 10A, the current value of the first current (I1) flowing in the first direction (Y direction), the current value of the second current (I2) flowing in the second busbar 10B in the first direction (Y direction), and the current value of the third current (I3) flowing in the third busbar 10C in the first direction (Y direction), the relationship I1 + I2 + I3 = 0 holds true. For example, the first current may be a U-phase AC current, the second current a V-phase AC current, and the third current a W-phase AC current.

[0015] The first busbar 10A, the second busbar 10B, and the third busbar 10C are arranged at intervals from each other in a second direction (X direction) perpendicular to the first direction (Y direction). In this embodiment, in the second direction (X direction), the third busbar 10C is arranged such that the distance between it and the second busbar 10B is equal to the distance between the first busbar 10A and the second busbar 10B. However, in the second direction (X direction), the distance between the first busbar 10A and the second busbar 10B and the distance between the second busbar 10B and the third busbar 10C may be different.

[0016] The first busbar 10A extends linearly along the first direction (Y direction). The current value (I1) of the first current flowing through the first busbar 10A can be positive or negative because it is an alternating current.

[0017] The second busbar 10B extends linearly along the first direction (Y direction). The current value (I2) of the second current flowing through the second busbar 10B can be positive or negative because it is an alternating current.

[0018] The third busbar 10C extends linearly along the first direction (Y direction). The current value (I3) of the third current flowing through the third busbar 10C can be positive or negative because it is an alternating current.

[0019] The first sensor unit 20A is positioned between any two busbars other than the busbar to be measured from among the first busbar 10A, the second busbar 10B, and the third busbar 10C. In this embodiment, the first sensor unit 20A measures the third busbar 10C as the busbar to be measured. Therefore, the first sensor unit 20A is positioned between the first busbar 10A and the second busbar 10B. The first sensor unit 20A is positioned on a substrate (not shown), for example. The position of the first sensor unit 20A may be fixed by a resin mold or the like.

[0020] The first sensor unit 20A includes a first magnetic detection element 30A and a second magnetic detection element 30B. Each of the first magnetic detection element 30A and the second magnetic detection element 30B is capable of detecting a magnetic field generated by the current flowing through the first busbar 10A, the second busbar 10B, and the third busbar 10C.

[0021] The first magnetic detection element 30A and the second magnetic detection element 30B each have a sensitivity axis oriented in a third direction (Z direction) that is orthogonal to the first direction (Y direction) and the second direction (X direction). Specifically, the first magnetic detection element 30A has a first sensitivity axis A1 oriented in the third direction (Z direction). The second magnetic detection element 30B has a second sensitivity axis A2 oriented in the third direction (Z direction).

[0022] The first magnetic detection element 30A and the second magnetic detection element 30B are aligned in the second direction (X direction). In this embodiment, the first magnetic detection element 30A and the second magnetic detection element 30B are aligned in the second direction (X direction) with substantially the same position in the third direction (Z direction).

[0023] The second sensor unit 20B measures one of the two busbars other than the first busbar to be measured. In this embodiment, the second sensor unit 20B measures the first busbar 10A as one of the two busbars other than the first busbar to be measured.

[0024] The second sensor unit 20B is positioned between the first busbar to be measured and the other of the two busbars other than the first busbar to be measured. In this embodiment, the second sensor unit 20B is positioned between the third busbar 10C and the second busbar 10B, which is the other of the two busbars other than the first busbar to be measured. The second sensor unit 20B is positioned on a substrate (not shown), for example. The position of the second sensor unit 20B may be fixed by a resin mold or the like.

[0025] The second sensor unit 20B includes a third magnetic detection element 30C and a fourth magnetic detection element 30D. Each of the third magnetic detection element 30C and the fourth magnetic detection element 30D is capable of detecting a magnetic field generated by the current flowing through the first busbar 10A, the second busbar 10B, and the third busbar 10C.

[0026] The third magnetic detection element 30C and the fourth magnetic detection element 30D each have a sensitivity axis oriented in the third direction (Z direction). Specifically, the third magnetic detection element 30C has a third sensitivity axis A3 oriented in the third direction (Z direction). The fourth magnetic detection element 30D has a fourth sensitivity axis A4 oriented in the third direction (Z direction).

[0027] The third magnetic detection element 30C and the fourth magnetic detection element 30D are aligned in the second direction (X direction). In this embodiment, the third magnetic detection element 30C and the fourth magnetic detection element 30D are aligned in the second direction (X direction) with their positions in the third direction (Z direction) being approximately the same.

[0028] In the first sensor unit 20A and the second sensor unit 20B, at least one of the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D may have a circuit consisting of at least two magnetoresistive elements. Each of the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D may have a circuit consisting of at least two magnetoresistive elements. The circuit consisting of at least two magnetoresistive elements may be a half-bridge circuit consisting of two magnetoresistive elements, or a Wheatstone bridge type bridge circuit consisting of four magnetoresistive elements.

[0029] Furthermore, the above magnetoresistive element is a tunnel magnetoresistive element (TM). It may be any of the following: a R)) element, a Giant Magneto Resistance (GMR) element, or an Anisotropic Magnetic Resistance (AMR) element.

[0030] First magnetic detection element 30A, second magnetic detection element 30B , third magnetic detection element 30C and fourth magnetic detection element 30D At least one of them may have a Hall element. Each of the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D may have a Hall element.

[0031] Each of the first busbar 10A, the second busbar 10B, the third busbar 10C, the first sensor unit 20A, and the second sensor unit 20B is positioned on a virtual plane F along the first direction (Y direction) and the second direction (X direction).

[0032] The calculation unit 40 calculates the current values ​​of the first busbar 10A, the second busbar 10B, and the third busbar 10C from the output values ​​of the first sensor unit 20A and the second sensor unit 20B, respectively.

[0033] As shown in Figure 3, the first sensor unit 20A and the second sensor unit 20B are each electrically connected to the calculation unit 40 by wiring. Specifically, the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D are each electrically connected to the calculation unit 40.

[0034] The following describes the positional relationship between each busbar and each magnetic detection element in each sensor unit.

[0035] As shown in Figure 2, when viewed from the first direction (Y direction), the distance a between the first magnetic detection element 30A and the first busbar 10A (one of the two busbars other than the busbar being measured), and the distance a between the second magnetic detection element 30B and the second busbar 10B (the other of the two busbars other than the busbar being measured) are approximately equal in distance. In this embodiment, "approximately equal in distance" includes variations in the assembly position during the manufacturing process when assembling each component of the current sensor.

[0036] When viewed from the first direction (Y direction), the distance b between the first magnetic detection element 30A and the second busbar 10B (the other of the two busbars other than the busbar being measured), and the distance b between the second magnetic detection element 30B and the first busbar 10A (the other of the two busbars other than the busbar being measured) are approximately equal in distance.

[0037] Since distance b is obtained by adding the distance between the first magnetic detection element 30A and the second magnetic detection element 30B to distance a, if the distance a between the first magnetic detection element 30A and the first busbar 10A, and the distance a between the second magnetic detection element 30B and the second busbar 10B are approximately equidistant, then the distance b between the first magnetic detection element 30A and the second busbar 10B, and the distance b between the second magnetic detection element 30B and the first busbar 10A will necessarily be approximately equidistant.

[0038] Viewed from the first direction (Y direction), the first magnetic detection element 30A and the third busbar 10C (a busbar of one measurement target) are positioned at a distance c1. Also, viewed from the first direction (Y direction), the second magnetic detection element 30B and the third busbar 10C (a busbar of one measurement target) are positioned at a distance c2.

[0039] With respect to the third magnetic detection element 30C and the fourth magnetic detection element 30D, the distance between the third magnetic detection element 30C and the second busbar 10B (the other of the two busbars other than the busbar being measured), and the distance between the fourth magnetic detection element 30D and the third busbar 10C (the busbar being measured), are approximately equal when viewed from the first direction (Y direction).

[0040] Viewed from the first direction (Y direction), the distance between the third magnetic detection element 30C and the third busbar 10C (one of the busbars being measured), and the distance between the fourth magnetic detection element 30D and the second busbar 10B (the other of the two busbars other than the one being measured) are approximately equal.

[0041] When viewed from the first direction (Y direction), the distances between the third magnetic detection element 30C and the fourth magnetic detection element 30D and the first busbar 10A (one of the two busbars other than the busbar being measured) are different from each other.

[0042] In this embodiment, no magnetic shielding plate made of a highly permeable magnetic material, nor a magnetic core made of a soft magnetic material for collecting magnetic fields, is provided between each busbar and each sensor unit. As a result, the overall size of the current sensor 1 according to this embodiment can be reduced.

[0043] The following explains how each sensor unit can measure only the current value of the busbar being measured, even if it detects a magnetic field that includes busbars other than the busbar being measured.

[0044] In this embodiment, the first sensor unit 20A can measure the current value (I3) flowing through the third busbar 10C. The second sensor unit 20B can measure the current value (I1) flowing through the first busbar 10A. The current value (I2) flowing through the second busbar 10B is calculated from the current values ​​measured by the first sensor unit 20A and the second sensor unit 20B. The measurement of the current value flowing through the corresponding busbar by each sensor unit will be explained using the example of measuring the current value I3 flowing through the third busbar 10C by the first sensor unit 20A.

[0045] Figure 4 is a cross-sectional view showing the state in which the magnetic field generated from each busbar in the current sensor according to Embodiment 1 of the present invention is detected by the first magnetic detection element of the first sensor unit. Figure 5 is a cross-sectional view showing the state in which the magnetic field generated from each busbar in the current sensor according to Embodiment 1 of the present invention is detected by the second magnetic detection element of the first sensor unit.

[0046] First, as shown in Figure 4, the magnetic field B detected by the first magnetic detection element 30A 11 This is the sum of the magnetic fields generated by each busbar and the external magnetic field. When the first current flows, a first magnetic field B1 is generated around the first busbar 10A. When the second current flows, a second magnetic field B2 is generated around the second busbar 10B. When the third current flows, a third magnetic field B3 is generated around the third busbar 10C. In addition, an external magnetic field B is generated due to external influences. ex This is occurring. Therefore, the magnetic field B detected by the first magnetic detection element 30A 11 B 11 =B1+B2+B3+B ex It is expressed as follows.

[0047] As shown in Figures 2 and 4, the first magnetic field B1 is expressed as B1 = μ(1 / 2πa)I1, using permeability μ and distance a, based on the relationship between magnetic flux density and magnetic field strength. If we assume that μ(1 / 2π) is a constant k in the above equation, then B1 can be expressed as B1 = (k / a)I1.

[0048] Similarly, when the second magnetic field B2 of the second bus bar 10B is detected by the first magnetic detection element 30A, the second magnetic field B2 is expressed as B2 = μ(1 / 2πb)I2. Assuming μ(1 / 2π) as a constant k, it is expressed as B2 = (k / b)I2. Further, when the third magnetic field B3 of the third bus bar 10C is detected by the first magnetic detection element 30A, the third magnetic field B3 is expressed as B3 = μ(1 / 2πc1)I3. Assuming μ(1 / 2π) as a constant k, it is expressed as B3 = (k / c1)I3.

[0049] The magnetic field B detected by the first magnetic detection element 30A 11 is, for example, when the direction in which the first sensitivity axis A1 points is taken as the positive direction, B 11 = B1 + B2 + B3 + B ex is expressed by Equation (1) by substituting the above respective equations. Further, as shown in FIGS. 2 and 5, the magnetic field B 12 of the second magnetic detection element 30B is also expressed by Equation (2) according to the respective relational expressions, similar to the case of the first magnetic detection element 30A.

[0050]

Number

[0051] In the first sensor unit 20A, the measured value of the magnetic field B11 detected by the first magnetic detection element 30A and the measured value of the magnetic field B 12 detected by the second magnetic detection element 30B can be processed by the calculation unit 40. Specifically, the calculation unit 40 can calculate the current value flowing through the third bus bar 10C (one of the measured bus bars) based on the differential output value between the measured value of the first magnetic detection element 30A and the measured value of the second magnetic detection element 30B in the first sensor unit 20A. The current value I3 of the third current flowing through the third bus bar 10C is calculated by the following formula.

[0052]

Number

[0053] In order to calculate the differential output value between the measurement value of the first magnetic detection element 30A and the measurement value of the second magnetic detection element 30B, the external magnetic field B measured in the first magnetic detection element 30A and the second magnetic detection element 30B ex These cancel each other out. Also, (c1-c2), which is shown by the coefficient of the current value I3, is equal to (ba) due to the positional relationship of the first magnetic detection element 30A with respect to each busbar. Therefore, as shown in equation (3) above, by replacing (c1-c2) with (ba), the current value of each busbar can be expressed by an equation that includes (ba) as a coefficient.

[0054] Furthermore, the current flowing through each busbar is three-phase alternating current, and the relationship I1 + I2 + I3 = 0 holds true. Therefore, by using I1 + I2 = -I3 in the above equation, it can be expressed by equation (4).

[0055] From the above equation, by calculating the differential output value between the measured value of the first magnetic detection element 30A and the measured value of the second magnetic detection element 30B in the first sensor unit 20A, the difference between the measured value of the first magnetic detection element 30A and the measured value of the second magnetic detection element 30B can be expressed by multiplying the current value I3 of the third current flowing through the third busbar 10C by a coefficient. Therefore, the difference between the measured value of the first magnetic detection element 30A and the measured value of the second magnetic detection element 30B, that is, the measured value V1 detected and calculated in the first sensor unit 20A, can be expressed in a proportional relationship with the current value I3 as shown in equation (5), and thus it is possible to measure the current value I3 flowing through the third busbar 10C in the first sensor unit 20A.

[0056] In the second sensor unit 20B, the measured magnetic field value detected by the third magnetic detection element 30C and the measured magnetic field value detected by the fourth magnetic detection element 30D are processed by the calculation unit 40. Specifically, based on the differential output value of the measured value of the third magnetic detection element 30C and the measured value of the fourth magnetic detection element 30D in the second sensor unit 20B, the current value flowing through the first busbar 10A (one of the two busbars other than the busbar being measured) can be calculated.

[0057] The current value flowing through the first busbar 10A is calculated in the same way as the calculation method used in the first sensor unit 20A. As a result, the measured value V2 detected and calculated in the second sensor unit 20B can be expressed in a proportional relationship with the current value I1, as shown in equation (6) below, and thus the second sensor unit 20B can measure the current value I1 flowing through the first busbar 10A.

[0058]

number

[0059] Furthermore, the calculation unit 40 can calculate the current value flowing through the other of the two busbars other than the busbar being measured by adding the current value I3 flowing through the third busbar 10C (one of the busbars being measured) and the current value I1 flowing through the first busbar 10A (one of the two busbars other than the busbar being measured).

[0060] Specifically, the calculation unit 40 adds the measured value V1 detected and calculated by the first sensor unit 20A and the measured value V2 detected and calculated by the second sensor unit 20B, and using the relationship I1+I2+I3=0, the following equation (7) can be obtained. Thus, the current value I2 flowing through the second busbar 10B can be calculated using the measured value V1 detected and calculated by the first sensor unit 20A and the measured value V2 detected and calculated by the second sensor unit 20B.

[0061]

number

[0062] As described above, in this embodiment, by measuring the magnetic fields in the first busbar 10A, the second busbar 10B, and the third busbar 10C using the first sensor unit 20A and the second sensor unit 20B, the current value I3 flowing through the third busbar 10C is calculated based on the magnetic field measurement value measured by the first sensor unit 20A, the current value I1 flowing through the first busbar 10A is calculated based on the magnetic field measurement value measured by the second sensor unit 20B, and the current value I2 flowing through the second busbar 10B can be calculated based on the calculated current values ​​I3 and I1. This makes it possible to measure the current values ​​of each busbar of a three-phase AC without providing shielding between each busbar.

[0063] Next, the circuit configuration of the current sensor 1 according to this embodiment will be described, but the circuit configuration of the current sensor 1 according to this embodiment is not limited to the following configuration.

[0064] Figure 6 is a schematic circuit diagram showing the circuit configuration of a current sensor according to Embodiment 1 of the present invention. As shown in Figure 6, in this embodiment, the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 30C, and the fourth magnetic detection element 30D each have a Wheatstone bridge type bridge circuit consisting of four tunnel-type magnetoresistive elements 31.

[0065] The detection signal from the first magnetic detection element 30A is transmitted via the first amplifier 32A to the first output value (V A The detection signal from the second magnetic detection element 30B is output as a first voltage signal indicating ). The detection signal from the second magnetic detection element 30B is output via the second amplifier 32B to the second output value (V B The detection signal from the third magnetic detection element 30C is output as a second voltage signal indicating the third output value (V) via the third amplifier 32C. C The detection signal from the fourth magnetic detection element 30D is output as a third voltage signal indicating ). The detection signal from the fourth magnetic detection element 30D is output via the fourth amplifier 32D to the fourth output value (V D It is output as a fourth voltage signal indicating ). The first amplifier 32A, the second amplifier 32B, the third amplifier 32C, and the fourth amplifier 32D are each composed of operational amplifiers that perform differential amplification.

[0066] The calculation unit 40 is an analog circuit formed by connecting circuit elements such as an amplifier. The calculation unit 40 calculates the first output value (V A ) First voltage signal, second output value (V B The second voltage signal and the third output value (V) are shown. C ) indicates the third voltage signal, fourth output value (V D A fourth voltage signal indicating ) is input, and in response to these input signals, a first output voltage signal (V) corresponding to the current (detected) value (I3) of the third current is input. 1OUT ), the second output voltage signal (V) corresponding to the current (detection) value (I2) of the second current 2OUT ), the third output voltage signal (V) corresponding to the current (detection) value (I1) of the first current. 3OUT Outputs ).

[0067] The calculation unit 40 includes a first differential amplifier 41A, a second differential amplifier 41B, and an adder amplifier 42.

[0068] The non-inverting input terminal (+) of the first differential amplifier 41A is connected to the first output value (V A A first voltage signal indicating ) is input, and the inverting input terminal (-) receives the second output value (V B A second voltage signal (V) is input. The first differential amplifier 41A receives the first output voltage signal (V) 1OUT ) outputs. Here, in this embodiment, since the above equation (5) is true, the calculation unit 40 outputs the first output voltage signal (V 1OUT This can be output as a voltage signal corresponding to the current (detection) value (I3) of the third current.

[0069] The non-inverting input terminal (+) of the second differential amplifier 41B is connected to the third output value (V C A third voltage signal indicating ) is input, and the inverting input terminal (-) receives the fourth output value (V D A fourth voltage signal (V) is input. The second differential amplifier 41B receives the third output voltage signal (V) 3OUT ) outputs. Here, in this embodiment, since the above equation (6) is true, the calculation unit 40 outputs the third output voltage signal (V 3OUTThis can be output as a voltage signal corresponding to the current (detection) value (I1) of the first current.

[0070] The summing amplifier 42 receives the first output voltage signal (V 1OUT ) and the third output voltage signal (V3 OUT The following is input: The summing amplifier 42 receives the second output voltage signal (V 2OUT ) outputs. Here, in this embodiment, since the above equation (7) is true, the calculation unit 40 outputs the second output voltage signal (V 2OUT This can be output as a voltage signal corresponding to the current (detection) value (I2) of the second current.

[0071] In the current sensor 1 according to Embodiment 1 of the present invention, when measuring each busbar of a three-phase AC current, a first sensor unit 20A and a second sensor unit 20B, each containing two magnetic detection elements, are placed between each busbar of the three-phase AC current. The two magnetic detection elements are positioned such that the distance between one magnetic detection element and one of the two busbars other than the one being measured, and the distance between the other magnetic detection element and the other of the two busbars other than the one being measured, are approximately equal. The magnetic field generated from the current flowing through each busbar is detected by the two magnetic detection elements, and the calculation unit 40 calculates the differential output value of the current values ​​measured by the two magnetic detection elements. This makes it possible to express the measured value of the magnetic field detected by each sensor unit as a value proportional to the current value of the busbar being measured among the busbars. The current values ​​of the two busbars being measured are measured by each of the two sensor units. The measured value of the remaining busbar is calculated from the current values ​​measured by each sensor unit based on the relationship of the three-phase AC current. This eliminates the need for shielding members to block external magnetic fields, canceling out their effects. As a result, the measured values ​​at each sensor unit can be represented solely by the current value being measured, eliminating the need for prior preparation such as measuring the current value of each busbar and obtaining parameters. Furthermore, it eliminates the need for complex calculations based on these parameters. Consequently, the overall size of the current sensor 1 can be reduced while improving measurement accuracy and responsiveness.

[0072] In the current sensor 1 according to Embodiment 1 of the present invention, since there is no need to provide a shielding member to block external magnetic fields for each busbar and each sensor unit, a simpler configuration and a low-cost current sensor can be constructed compared to the case in which a shielding member is provided.

[0073] In the current sensor 1 according to Embodiment 1 of the present invention, the overall size of the current sensor 1 can be reduced while improving measurement accuracy and responsiveness by using a TMR element, GMR element, AMR element, or Hall element.

[0074] In the current sensor 1 according to Embodiment 1 of the present invention, the busbars and sensor units can be arranged on a single plane to form a current sensor 1 with a reduced height.

[0075] (Embodiment 2) The current sensor according to Embodiment 2 of the present invention will now be described with reference to the figures. Since the arrangement of the second sensor unit in the current sensor according to Embodiment 2 of the present invention differs from that of the current sensor 1 according to Embodiment 1 of the present invention, the same configuration as that of the current sensor 1 according to Embodiment 1 of the present invention will not be repeated in the description.

[0076] Figure 7 is a cross-sectional view showing the configuration of a current sensor according to Embodiment 2 of the present invention. As shown in Figure 7, the current sensor 1A according to Embodiment 2 of the present invention comprises a first busbar 10A, a second busbar 10B, a third busbar 10C, a first sensor unit 20A, a second sensor unit 50B, and a calculation unit. The first sensor unit 20A measures the third busbar 10C as one of the busbars to be measured.

[0077] The second sensor unit 50B measures one of the two busbars other than the first busbar to be measured. In this embodiment, the second sensor unit 50B measures the second busbar 10B as one of the two busbars other than the first busbar to be measured.

[0078] The second sensor unit 50B is positioned between the first busbar to be measured and the other of the two busbars other than the first busbar to be measured. In this embodiment, the second sensor unit 50B is positioned between the third busbar 10C and the first busbar 10A, which is the other of the two busbars other than the first busbar to be measured.

[0079] The second sensor unit 50B includes a third magnetic detection element 60C and a fourth magnetic detection element 60D.

[0080] The third magnetic detection element 60C and the fourth magnetic detection element 60D each have a sensitivity axis oriented in the third direction (Z direction). Specifically, the third magnetic detection element 60C has a third sensitivity axis A3 oriented in the third direction (Z direction). The fourth magnetic detection element 60D has a fourth sensitivity axis A4 oriented in the third direction (Z direction).

[0081] The third magnetic detection element 60C and the fourth magnetic detection element 60D are aligned in the second direction (X direction). In this embodiment, the third magnetic detection element 60C and the fourth magnetic detection element 60D are aligned in the second direction (X direction) with their positions in the third direction (Z direction) being approximately the same.

[0082] Each of the first magnetic detection element 30A, the second magnetic detection element 30B, the third magnetic detection element 60C, and the fourth magnetic detection element 60D is capable of detecting the magnetic field generated by the current flowing through the first busbar 10A, the second busbar 10B, and the third busbar 10C.

[0083] The calculation unit calculates the current values ​​of the first busbar 10A, the second busbar 10B, and the third busbar 10C from the output values ​​of the first sensor unit 20A and the second sensor unit 50B, respectively.

[0084] The positional relationship between each busbar and each magnetic detection element will be explained below. As shown in Figure 7, when viewed from the first direction (Y direction), the distance d between the third magnetic detection element 60C and the first busbar 10A (the other of the two busbars other than the busbar being measured), and the distance d between the fourth magnetic detection element 60D and the third busbar 10C (the busbar being measured) are approximately equidistant.

[0085] Viewed from the first direction (Y direction), the distance e between the third magnetic detection element 60C and the third busbar 10C (one of the busbars being measured), and the distance e between the fourth magnetic detection element 60D and the first busbar 10A (the other of the two busbars other than the one being measured), are approximately equidistant.

[0086] Viewed from the first direction (Y direction), the third magnetic detection element 60C and the second busbar 10B (one of the two busbars other than the busbar being measured) are positioned at a distance f1. Also, viewed from the first direction (Y direction), the fourth magnetic detection element 60D and the second busbar 10B are positioned at a distance f2. Note that distances f1 and f2 may be different from each other.

[0087] In this embodiment, the first sensor unit 20A can measure the current value (I3) flowing through the third busbar 10C. The second sensor unit 50B can measure the current value (I2) flowing through the second busbar 10B. The current value (I1) flowing through the first busbar 10A is calculated from the current values ​​measured by the first sensor unit 20A and the second sensor unit 50B.

[0088] Similar to Embodiment 1, the first sensor unit 20A, the second sensor unit 50B, and the calculation unit detect and calculate the measured value V1 in the first sensor unit 20A and the magnetic field B detected by the third magnetic detection element 60C of the second sensor unit 50B based on the following equations (8) to (14). 21 and the magnetic field B detected by the fourth magnetic detection element 60D 22 Based on the measured value V2 calculated using this method, the current value flowing through each busbar 10 can be calculated.

[0089]

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[0090] In the current sensor 1A according to Embodiment 2 of the present invention, when measuring each busbar of a three-phase AC current, a first sensor unit 20A and a second sensor unit 50B, each containing two magnetic detection elements, are placed between each busbar of the three-phase AC current. The two magnetic detection elements are positioned such that the distance between one magnetic detection element and one of the two busbars other than the one being measured, and the distance between the other magnetic detection element and the other of the two busbars other than the one being measured, are approximately equal. The magnetic field generated from the current flowing through each busbar is detected by the two magnetic detection elements, and the calculation unit calculates the differential output value of the current values ​​measured by the two magnetic detection elements. This makes it possible to express the measured value of the magnetic field detected by each sensor unit as a value proportional to the current value of the busbar being measured among the busbars. The current values ​​of the two busbars being measured are measured by each of the two sensor units. The measured value of the remaining busbar is calculated from the current values ​​measured by each sensor unit based on the relationship of the three-phase AC current. This eliminates the need for shielding materials to block external magnetic fields, canceling out their effects while allowing each sensor unit's measurements to be represented solely by the current value being measured. This eliminates the need for prior preparation, such as measuring the current values ​​of each busbar and obtaining parameters. Furthermore, it eliminates the need for complex calculations based on these parameters. As a result, the overall size of the current sensor 1A can be reduced while improving measurement accuracy and responsiveness.

[0091] Furthermore, it is desirable that the cross-sectional areas of the first, second, and third busbars be approximately the same in order to facilitate the uniform distribution of current.

[0092] In the description of the embodiments described above, the combinable configurations may be combined with each other.

[0093] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope of equivalents of the claims are intended. [Explanation of symbols]

[0094] 1,1A Current sensor, 10A First busbar, 10B Second busbar, 10C Third busbar, 20A First sensor unit, 20B,50B Second sensor unit, 30A First magnetic detection element, 30B Second magnetic detection element, 30C,60C Third magnetic detection element, 30D,60D Fourth magnetic detection element, 31 Tunnel-type magnetoresistive element, 32A First amplifier, 32B Second amplifier, 32C Third amplifier, 32D Fourth amplifier, 40 Calculation unit, 41A First differential amplifier, 41B Second differential amplifier, 42 Adding amplifier, A1 First sensitivity axis, A2 Second sensitivity axis, A3; third sensitivity axis, A4; fourth sensitivity axis, F; virtual plane.

Claims

1. A first busbar, a second busbar, and a third busbar, each extending in a first direction with a distance between them and aligned in a second direction perpendicular to the first direction, through which a three-phase alternating current flows, A first sensor unit is positioned between two busbars other than any one of the first busbar, the second busbar, and the third busbar that is to be measured, A second sensor unit is positioned between the first busbar to be measured and the other of the two busbars other than the first busbar to be measured, with the latter being the target of measurement. The system includes a calculation unit that calculates the current values ​​of the first busbar, the second busbar, and the third busbar from the output values ​​of the first sensor unit and the second sensor unit, respectively. The first sensor unit each has a sensitivity axis oriented in a third direction perpendicular to the first and second directions, and includes a first magnetic detection element and a second magnetic detection element that are aligned in the second direction and detect magnetic fields generated by currents flowing through the first busbar, the second busbar, and the third busbar. The second sensor unit includes a third magnetic detection element and a fourth magnetic detection element, each having a sensitivity axis oriented in the third direction, and arranged in the second direction, which detect magnetic fields generated by currents flowing through the first busbar, the second busbar, and the third busbar. Viewed from the first direction, the distance between the first magnetic detection element and one of the two busbars other than the first busbar to be measured, and the distance between the second magnetic detection element and the other of the two busbars other than the first busbar to be measured, are approximately equal in distance. Viewed from the first direction, the distance between the third magnetic detection element and the other of the two busbars other than the first busbar to be measured, and the distance between the fourth magnetic detection element and the first busbar to be measured are approximately equal. The calculation unit is capable of calculating the current value flowing through one of the busbars to be measured based on the differential output value between the measurement value of the first magnetic detection element and the measurement value of the second magnetic detection element in the first sensor unit, and is capable of calculating the current value flowing through one of the two busbars other than the one of the busbars to be measured based on the differential output value between the measurement value of the third magnetic detection element and the measurement value of the fourth magnetic detection element in the second sensor unit, and is capable of calculating the current value flowing through the other of the two busbars other than the one of the busbars to be measured by adding the current value flowing through the one of the busbars to be measured and the current value flowing through one of the two busbars other than the one of the busbars to be measured.

2. The current sensor according to claim 1, wherein each of the first sensor unit and the second sensor unit has a circuit including a tunnel-type magnetoresistive element.

3. The current sensor according to claim 1, wherein each of the first sensor unit and the second sensor unit has a circuit including a giant magnetoresistive element.

4. The current sensor according to claim 1, wherein each of the first sensor unit and the second sensor unit has a circuit including an anisotropic magnetoresistive element.

5. The current sensor according to claim 1, wherein each of the first sensor unit and the second sensor unit has a circuit including a Hall element.

6. The current sensor according to any one of claims 1 to 5, wherein each of the first busbar, the second busbar, the third busbar, the first sensor unit, and the second sensor unit is arranged on a virtual plane along the first direction and the second direction.

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