Current sensor and current detection device

Abstract

A main objective of the present invention is to provide a current sensor capable of stably measuring the current value of a high-frequency current.　A current sensor 2 comprises a Rogowski coil 11 including: a rod-shaped winding core 12; a winding 13 wound clockwise from one end A side to the other end B side of the winding core 12; and a winding 14 wound counterclockwise from the one end A side to the other end B side of the winding core 12, wherein a tip part 13-2 of the winding 13 and a tip part 14-2 of the winding 14 are connected to each other on the other end B side of the winding core 12, and a base end part 13-1 of the winding 13 and a base end part 14-1 of the winding 14 are drawn out from the one end A side of the winding core 12. The Rogowski coil 11 includes a return conductor 15 which is arranged along the length direction of the winding core 12, and in which a tip part 15b is connected to the tip part 13-2 of the winding 13 and the tip part 14-2 of the winding 14, and a base end part 15a is drawn out from the one end A side of the winding core 12.

Description

Current Sensor and Current Detection Device

[0001] The present invention relates to a Rogowski coil provided with a rod-shaped core, a first winding wire wound clockwise from one end side to the other end side of the core, and a second winding wire wound counterclockwise from one end side to the other end side of the core. At the other end side of the core, the tip ends of the first winding wire and the second winding wire are connected to each other, and the base ends of the first winding wire and the second winding wire are drawn out from one end side of the core. The present invention also relates to a current sensor provided with this Rogowski coil and a current detection device provided with this current sensor.

[0002] As this type of current sensor, a Rogowski coil disclosed in Patent Document 1 below is known. This Rogowski coil includes a rod-shaped core, a first winding wire wound clockwise from one end side to the other end side of the core, and a second winding wire wound counterclockwise from one end side to the other end side of the core. At the other end side of the core, the tip ends of the first winding wire and the second winding wire are connected to each other, and the base ends of the first winding wire and the second winding wire are drawn out from one end side of the core. With this configuration, according to this Rogowski coil, an effect that it can be used for zero-phase current detection can be achieved.

[0003] Japanese Patent Application Laid-Open No. 2004-235595 (pages 2-5, FIG. 5)

[0004] However, the conventional Rogowski coil has the following problems. Specifically, in the conventional Rogowski coil, when used as a current sensor of a current detection device, for example, the first winding wire and the second winding wire are connected to a pair of input parts of an integrating circuit on the current detection device side and used. In this case, the potentials of the first winding wire and the second winding wire are in a floating state from the reference potential on the current detection device side. Therefore, when measuring the current value of a high-frequency current, the output signal of the Rogowski coil output from the first winding wire and the second winding wire is not stable with respect to the reference potential on the current detection device side. As a result, there is a problem that it is difficult to stably measure the current value of the high-frequency current.

[0005] Furthermore, as mentioned above, when the first and second windings are connected to the pair of inputs of the integrating circuit on the current detection device side, noise may enter the first and second windings due to capacitive coupling with the Rogowski coil. In this case, the entered noise becomes common-mode noise, but if it is unstable with respect to the reference potential, the current detection device cannot effectively remove this common-mode noise, which presents a problem as it becomes difficult for the current detection device to measure the current value with high accuracy.

[0006] This invention was made to solve the aforementioned problems, and its main objective is to provide a current sensor and current detection device capable of stably measuring the current value of AC current over a wide frequency band. Furthermore, it also aims to provide a current sensor and current detection device capable of measuring current values ​​with high accuracy.

[0007] To achieve the above objective, the current sensor according to the present invention comprises a rod-shaped core, a first winding wound clockwise from one end to the other of the core, and a second winding wound counterclockwise from one end to the other of the core, and a Rogowski coil in which the tip of the first winding and the tip of the second winding are connected to each other at the other end of the core, and the base end of the first winding and the base end of the second winding are drawn out from the one end of the core, wherein the Rogowski coil is arranged along the length direction of the core and has a return wire whose tip is connected to the tip of the first winding and the tip of the second winding, and whose base end is drawn out from the one end of the core.

[0008] In this current sensor and current detection device equipped with this current sensor, the Rogowski coil is arranged along the length of the winding core and has a return wire whose tip is connected to the tip of the first winding and the tip of the second winding, and whose base is drawn out from one end of the winding core. By setting the potential of the return wire and the reference potential in the current detection device to the same potential, the polarity of the first output signal output from the first winding and the polarity of the second output signal output from the second winding can be set to opposite polarities and to a stable voltage. Therefore, with this current sensor and current detection device, for example, by obtaining the difference signal of the first integrated signal and the second integrated signal obtained by integrating the first output signal and the second output signal, the output signals of the Rogowski coils output from the first winding and the second winding (first output signal and second output signal) become stable with respect to the reference potential on the current detection device side, and as a result, the current value of the measurement current, which is a high-frequency current, can be measured stably. Therefore, with this current sensor and current detection device equipped with this current sensor, the current value of AC current over a wide frequency band can be measured stably.

[0009] Furthermore, this current sensor and current detection device can sufficiently remove common-mode noise superimposed on the first and second output signals by, for example, obtaining the difference signal between the first integrated signal and the second integrated signal obtained by integrating the first and second output signals. Therefore, this current sensor and current detection device can measure the current value of the measured current with sufficiently high accuracy.

[0010] Furthermore, in the current sensor according to the present invention, the return wire is inserted inside the winding core.

[0011] This current sensor and current detection device makes it possible to eliminate or reduce the superposition of noise caused by an external magnetic field onto the first and second output signals, and as a result, the current value of the measured current can be measured with higher accuracy.

[0012] Furthermore, in the current sensor according to the present invention, the first winding and the second winding are wound in a state where their upper and lower halves are alternately reversed.

[0013] This current sensor and current detection device makes it possible to sufficiently enhance the symmetry of the first and second output signals to be detected.

[0014] Furthermore, in the current sensor according to the present invention, the first winding and the second winding are wound in a manner that prevents them from alternating between upper and lower positions.

[0015] Furthermore, in the current sensor according to the present invention, the first winding and the second winding are wound such that the average winding pitch of the upper winding of either the first winding or the second winding is greater than the average winding pitch of the lower winding of the other of the first winding or the second winding.

[0016] These current sensors and current detection devices allow for the measurement of the current value with sufficiently high accuracy.

[0017] Furthermore, in the current sensor according to the present invention, a portion of the winding of the first winding and a portion of the winding of the second winding are wound in an alternating up-and-down manner, while the other portion of the winding of the first winding and the other portion of the winding of the second winding are wound in a manner that is not alternating up-and-down, and the average winding pitch of the upper winding of either the first winding or the second winding is greater than the average winding pitch of the lower winding of the other.

[0018] This current sensor and current detection device allows for the measurement of the current value with sufficiently high accuracy.

[0019] Furthermore, the current sensor according to the present invention includes a shielding conductor that shields the Rogowski coil.

[0020] Compared to current sensors and current detection devices without shielding conductors, this current sensor and current detection device has a lower measurable frequency range, but it is less susceptible to external noise affecting the first and second output signals.

[0021] Furthermore, the current sensor according to the present invention includes a first insulated wire connected to the base end of the first winding and a second insulated wire connected to the base end of the second winding, and also includes a connecting cable in which the first insulated wire and the second insulated wire are twisted together.

[0022] With this current sensor and current detection device, when the current sensor is connected to the current detection device via a connecting cable, the superposition of external noise on the first output signal and the second output signal can be eliminated or reduced.

[0023] Furthermore, in the current sensor according to the present invention, the connecting cable is configured to be set to the same potential as the return wire and includes a shielding conductor that shields the first insulated wire and the second insulated wire.

[0024] With this current sensor and current detection device, by connecting the current sensor and the current detection device with a connecting cable, the first and second output signals can be made less susceptible to external noise, and the potential of the return wire can be set to the same potential as the reference potential of the current detection device.

[0025] Furthermore, in order to achieve the above objective, the current detection device according to the present invention comprises the above-mentioned current sensor, a first integrating circuit configured to have a reference potential that can be set to the same potential as the return wire potential and which integrates the first output signal of the Rogowski coil output from the base end of the first winding to generate a first integrated signal, a second integrating circuit configured to have a reference potential that can be set to the same potential as the return wire potential and which integrates the second output signal of the Rogowski coil output from the base end of the second winding to generate a second integrated signal, and a difference circuit that generates a difference signal between the first integrated signal and the second integrated signal.

[0026] This current detection device allows the output signals of the Rogowski coil (first output signal and second output signal) output from the first and second windings to be stabilized relative to the reference potential on the current detection device side. As a result, the current value of the measurement current, which is a high-frequency current, can be measured stably. Therefore, this current detection device can stably measure the current value of AC currents across a wide frequency band. Furthermore, this current detection device can sufficiently remove common-mode noise superimposed on the Rogowski coil output signals (first output signal and second output signal) by obtaining the difference signal between the first and second integrated signals obtained by integrating the Rogowski coil output signals (first output signal and second output signal). Therefore, this current detection device can measure the current value of the measurement current with sufficiently high accuracy.

[0027] Furthermore, in the current detection device according to the present invention, the first integrating circuit is configured to include an active first integrator, and the second integrating circuit is configured to include an active second integrator.

[0028] This current detection device can generate the first and second integral signals with sufficient gain.

[0029] Furthermore, in the current detection device according to the present invention, the first integrating circuit is configured to include an RC-type third integrator that integrates the first output signal and outputs it to the first integrator, and the second integrating circuit is configured to include an RC-type fourth integrator that integrates the second output signal and outputs it to the second integrator.

[0030] This current detection device allows for auxiliary integration of the first and second output signals up to higher frequencies. As a result, the first and second integrating circuits as a whole can ideally integrate the first and second output signals from low frequencies to higher frequencies. Therefore, this current detection device enables current detection with excellent frequency characteristics for the measured current.

[0031] Furthermore, the current detection device according to the present invention includes a signal ratio adjustment circuit that adjusts the ratio of the magnitude of the second integral signal to the magnitude of the first integral signal.

[0032] Furthermore, in the current detection device according to the present invention, the signal ratio adjustment circuit adjusts the ratio by adjusting the magnitude of the amplification of the second integrating circuit relative to the magnitude of the amplification of the first integrating circuit.

[0033] These current detection devices allow for a good balance between the detection sensitivity of the first winding for the first integrated signal and the detection sensitivity of the second winding for the second integrated signal.

[0034] Furthermore, the current detection device according to the present invention includes a processing unit that detects the current value of the current flowing through the conductor to be measured, which is inserted into the Rogowski coil, based on the difference signal.

[0035] This current detection device allows the processing circuit to accurately and stably detect the current value of the measured current based on the difference signal.

[0036] According to the current sensor and current detection device of the present invention, for example, by obtaining the difference signal between the first integrated signal and the second integrated signal obtained by integrating the first output signal and the second output signal, the output signals of the Rogowski coil (first output signal and second output signal) output from the first winding and the second winding become stable with respect to the reference potential on the current detection device side. As a result, the current value of the measurement current, which is a high-frequency current, can be measured stably. Therefore, with this current sensor and current detection device, the current value of AC current over a wide frequency band can be measured stably. Furthermore, with this current sensor and current detection device, the current value of the measurement current can be measured with sufficiently high accuracy.

[0037] This is a configuration diagram showing the configuration of the current detection device 1. This is a side view of the Rogowski coil 11. This is a circuit diagram of the integrating circuits 33 and 34. This is an explanatory diagram showing a top view of the Rogowski coil 11 to explain the effect of noise caused by an external magnetic field H on the Rogowski coil 11. This is an explanatory diagram to explain the effect of noise caused by an external magnetic field H on the Rogowski coil 11. This is a frequency characteristic diagram of the induced electromotive forces V1 and V2 output from the Rogowski coil 11. This is a frequency characteristic diagram showing the amplification of the integrator AI. This is a frequency characteristic diagram showing the amplification of the integrators PI and AI as a whole. This is a frequency characteristic diagram of the integrated signals V1i and V2i output from the integrating circuits 33 and 34. This is a configuration diagram showing the inverter 101 of the electric vehicle 100, the axle motor 102, and the busbars 103A to 103C that connect the inverter 101 and the motor 102 and function as current passages. This is a diagram showing the state in which the Rogowski coil 11 is attached to the busbar 103B. This is a configuration diagram showing part of the configuration of the Rogowski coil 11A. This is a diagram of the current detection device 1A using a Rogowski coil 11A. This is a circuit diagram of the integrating circuits 33A and 34A. This is a diagram of the current sensor 2B. This is a diagram of the connecting cable 21B. This is a diagram of the Rogowski coil 11D. This is a diagram of the Rogowski coil 11E. This is a diagram of the Rogowski coil 11F. This is a circuit diagram of the differential integrating circuit 51.

[0038] The embodiments of the current sensor and current detection device will be described below with reference to the attached drawings.

[0039] First, the configuration of the current detection device 1 will be explained with reference to the drawings.

[0040] (First Embodiment) As shown in Figure 1, the current detection device 1 comprises a current sensor 2 and a device body 3. The current sensor 2 is connected to the device body 3, and the Rogowski coil 11 of the current sensor 2, described later, is attached to the conductor to be measured 4 so as to surround the conductor 4 and form a ring. The device is configured to measure the current value I1 of the measurement current I, which is an alternating current flowing through the conductor to be measured 4.

[0041] As shown in Figure 1, the current sensor 2 is configured to include a Rogowski coil 11 and a connecting cable 21 for connecting the Rogowski coil 11 to the main body 3 of the device. The Rogowski coil 11 is an air-core coil and is configured to include a winding core 12 shown by a dashed line in Figure 1, and windings 13 and 14 wound from one end A to the other end B of the winding core 12.

[0042] In this case, the winding core 12 is formed in a long, flexible rod shape (for example, a cylindrical body with a nearly constant diameter) using an insulating material such as a resin material. Also, as shown in Figures 1 and 2, a return conductor 15 is arranged inside the winding core 12, passing through the center of the winding core 12 from one end A to the other end B.

[0043] Winding 13 corresponds to the first winding, and is made by winding an insulated wire, formed by covering the internal conductor with an insulating material, clockwise from one end A to the other end B of the winding core 12. Winding 14 corresponds to the second winding, and is made by winding an insulated wire, formed by covering the internal conductor with an insulating material, counterclockwise from one end A to the other end B of the winding core 12, with the same number of turns as winding 13. In this case, as shown in Figure 2, windings 13 and 14 are wound alternately in an alternating top-bottom configuration. In reality, windings 13 and 14 are tightly wound in a braided manner, but in Figures 1 and 2, for ease of understanding, windings 13 and 14 are shown wound with gaps between them. Furthermore, in Figure 2, winding 13 is shown as a white wire and winding 14 as a black wire to make them easier to distinguish.

[0044] Further, at the other end B side of the bobbin 12, the tip portions 13b of the winding 13 and the tip portions 14b of the winding 14 are connected to each other, and the base end portions 13a of the winding 13 and the base end portions 14a of the winding 14 are drawn out from one end A side of the bobbin 12. In this case, the base end portions 13a of the winding 13 and the base end portions 14a of the winding 14 function as the output ends of the Rogowski coil 11. Further, the winding 13 outputs an induced electromotive voltage V1 as a first output signal, which is a differential signal whose voltage value changes in proportion to the magnitude of the time change (dI1 / dt) of the current value I1 of the measurement current I flowing through the measurement target conductor 4 to which the Rogowski coil 11 is attached, from the base end portion 13a. Further, the winding 14 outputs an induced electromotive voltage V2 as a second output signal, which is a differential signal whose voltage value changes in proportion to the magnitude of the time change (dI1 / dt) of the current value I1 of the measurement current I flowing through the measurement target conductor 4 to which the Rogowski coil 11 is attached, from the base end portion 14a.

[0045] The return conductor 15 is formed of, for example, a copper wire and functions as a return wire. As shown in FIGS. 1 and 2, the return conductor 15 is disposed along the length direction of the bobbin 12, the tip portion 15b is connected to the tip portions  13b of the winding 13 and the tip portions 14b of the winding 14, and the base end portion 15a is drawn out from one end A side of the bobbin 12.

[0046] In this case, as will be described later, by connecting the base end portion 15a of the return conductor 15 to the reference potential G of the apparatus main body 3, the induced electromotive voltages V1 and V2 output from the Rogowski coil 11 are voltages indicating voltage values with reference to the reference potential G of the apparatus main body 3. Further, since the windings 13 and 14 are wound in opposite directions to each other, the induced electromotive voltages V1 and V2 have voltage values of opposite polarities to each other, and their absolute values are equal to or substantially equal to each other.

[0047] Furthermore, in this Rogowski coil 11, since the return conductor 15 passes through the center of the coil core 12, the superposition of the induced electromotive voltages V1 and V2 of the noise caused by the external magnetic field is significantly reduced. Specifically, for example, as shown in FIG. 4, it is assumed that when viewed from above the Rogowski coil 11, the external magnetic field H acts in a direction toward the side surface of the Rogowski coil 11. In this case, due to the structure of the winding, the Rogowski coil 11 has a coil area in the side surface direction as well, and thus has a detection sensitivity to the external magnetic field H. Therefore, as shown in the upper part of FIG. 5, when the return conductor 15 passes through the center of the coil core 12, the triangular area S1 surrounded by the return conductor 15 and the winding 13 (or 14) located above the return conductor 15 when the Rogowski coil 11 is viewed from the side is equal to the triangular area S2 surrounded by the return conductor 15 and the winding 13 (or 14) located below the return conductor 15. On the other hand, as shown in the lower part of the same figure, when the return conductor 15 passes through above the center of the coil core 12, the triangular area S1 becomes smaller than the triangular area S2. That is, when the return conductor 15 passes through in a state biased upward or downward with respect to the center of the coil core 12, the triangular area S1 and the triangular area S2 are not equal.

[0048] In this case, in the Rogowski coil 11, the detection directions of the noise caused by the external magnetic field H are opposite to each other between the triangle of the area S1 above the return conductor 15 and the triangle of the area S2 below. Therefore, when the return conductor 15 passes through the center of the coil core 12 and the triangular areas S1 and S2 are equal, the noise caused by the external magnetic field H is canceled out, and the superposition of the noise on the induced electromotive voltages V1 and V2 disappears or is reduced. On the other hand, when the return conductor 15 does not pass through the center of the coil core 12, the noise that is not canceled out is superimposed on the induced electromotive voltages V1 and V2 and output. Therefore, it is preferable to adopt a configuration in which the return conductor 15 passes through the center of the coil core 12 (an example inside) as in this example.

[0049] In this Rogowski coil 11, the entire core 12 and windings 13 and 14 are not covered with insulating coating. However, when a high voltage is applied to the conductor 4 to be measured, a configuration in which they are covered with insulating coating can be adopted to ensure safety. Also, although not shown in Figures 1 and 2, the Rogowski coil 11 is equipped with a holding part that holds the Rogowski coil 11 in an annular shape by inserting the other end B of the core 12 into an opening formed on one end A. Therefore, in this Rogowski coil 11, the other end B of the Rogowski coil 11 can be detachably attached to the conductor 4 to be measured by inserting and pulling out the other end B of the Rogowski coil 11 into the one end A.

[0050] The connecting cable 21 comprises, for example, two twisted insulated conductors 22 and 23, one insulated conductor 24, and a sheath 25 covering the insulated conductors 22 to 24. Therefore, because the insulated conductors 22 and 23 are twisted, the connecting cable 21 is configured to effectively prevent the superposition of external noise onto the insulated conductors 22 and 23. Of the two insulated conductors 22 and 23 extending from one end, one insulated conductor 22 is connected to the base end 13a of the winding 13 of the Rogowski coil 11, and the other insulated conductor 23 is connected to the base end 14a of the winding 14 of the Rogowski coil 11. In addition, insulated conductor 24 functions as a reference conductor for defining the potential of the return conductor 15 of the Rogowski coil 11 to a reference potential, and is connected to the base end 15a of the return conductor 15. Furthermore, one of the two insulated conductors 22 and 23 extending from the other end is connected to the integrating circuit 33 in the main body of the device 3, as will be described later, and the other insulated conductor 23 is connected to the integrating circuit 34 in the main body of the device 3. In addition, the insulated conductor 24 is connected to the reference potential G of the main body of the device 3. Note that an uninsulated conductor can be used instead of the insulated conductor 24. It is also possible to adopt a configuration without insulation 25. Furthermore, it is also possible to adopt a configuration in which the insulated conductors 22 to 24 are twisted together. With this configuration, the superposition of external noise can be blocked even more effectively.

[0051] With the above configuration, the current sensor 2 outputs the induced electromotive force V1 from the Rogowski coil 11 to the device body 3 via the connecting cable 21, and the induced electromotive force V2 from the Rogowski coil 11 to the device body 3 via the connecting cable 21. In addition, the return conductor 15 of the Rogowski coil 11 is connected to the reference potential G of the device body 3 via the insulated conductor 24 of the connecting cable 21, so that the potential of the return conductor 15 becomes the same as the reference potential G of the device body 3.

[0052] The main body of the device 3 is configured, for example, with a case 31, a power supply circuit 32, integrating circuits 33 and 34, a difference circuit 35, an amplification circuit 36, a processing circuit 37, and an output circuit 38. The power supply circuit 32 is, for example, a DC power supply (which may be a battery) and generates an operating DC voltage (a voltage referenced to a reference potential G) for each of the circuits 33 to 38 arranged inside the case 31 and outputs it to each of the circuits 33 to 38.

[0053] Case 31 is formed, for example, as a box. Also, as shown in Figure 1, the insulated conductor 22 of the connecting cable 21 is connected to the input terminal of the integrating circuit 33 via the internal wiring of the main body 3 of the device. The insulated conductor 23 of the connecting cable 21 is connected to the input terminal of the integrating circuit 34 via the internal wiring of the main body 3 of the device. The insulated conductor 24 of the connecting cable 21 is connected to the reference potential G, which is the internal ground of the main body 3 of the device, via the internal wiring of the main body 3 of the device.

[0054] In this configuration, the induced electromotive force V1 output from the current sensor 2 is input between the reference potential G and the input terminal of the integrating circuit 33. Additionally, the induced electromotive force V2 output from the current sensor 2 is input between the reference potential G and the input terminal of the integrating circuit 34.

[0055] The integrating circuit 33 corresponds to the first integrating circuit and, for example, as shown in Figure 3, is configured with a passive integrator PI as the third integrator and an active integrator AI as the first integrator connected in series with integrator PI. In this case, integrator PI is configured with an RC type integrator consisting of a resistor 41 and a capacitor 42. Integrator AI is configured with an operational amplifier 43, resistors 41 and 44 connected in series with the negative input terminal of the operational amplifier 43, and a parallel circuit of a feedback resistor 45 and a capacitor 46 connected between the negative input terminal and the output terminal of the operational amplifier 43. The integrating circuit 34 corresponds to the second integrating circuit and, as shown in the same figure, is configured identically to the integrating circuit 33, comprising a passive integrator PI as the fourth integrator and an active integrator AI as the second integrator connected in series with integrator PI. In other words, the amplification and frequency characteristics of the integrating circuit 34 are configured to have the same characteristics as the integrating circuit 33.

[0056] With this configuration, the integrating circuits 33 and 34 integrate the induced voltages V1 and V2 with the frequency characteristics described below to generate an integrated signal V1i corresponding to the first integrated signal and an integrated signal V2i corresponding to the second integrated signal, respectively. As shown in Figure 6, the Rogowski coil 11 outputs induced voltages V1 and V2 of differential signals whose voltage value changes in proportion to the magnitude of the time change (dI1 / dt) as described above. In this case, since the induced voltages V1 and V2 are minute voltages at low frequencies, an arithmetic circuit with low offset, low noise, and high amplification is required to integrate these induced voltages V1 and V2 to a sufficient voltage value. However, as shown in Figure 7, integrators AI using such arithmetic circuits generally have poor high-frequency characteristics, so although they integrate from low frequencies fc1 to high frequencies fc2, it is difficult to perform the ideal integration operation of integrating up to frequencies even higher than fc2. Therefore, in these integrating circuits 33 and 34, an RC-type integrator PI is provided before the integrator AI to auxiliaryly integrate the induced voltages V1 and V2. As shown in Figure 8, the integrators PI and AI as a whole integrate the induced voltages V1 and V2 up to a frequency fc3 that is even higher than frequency fc2. Consequently, as shown in Figure 9, the integrating circuits 33 and 34 as a whole ideally integrate the induced voltages V1 and V2 from the low frequency fc1 to the higher frequency fc3. In the same figure, the dashed line between frequencies fc2 and fc3 shows the frequency characteristics of an integrating circuit with only the integrator AI and no integrator PI. Therefore, it is possible to adopt a configuration without the integrator PI, but it can be seen that the integrating circuits 33 and 34 equipped with integrators PI and Ai perform excellent integration over a wide frequency band, as they also perform excellent integration in the high-frequency band.

[0057] Furthermore, when integration operation in a higher frequency range is required, an active integrator AI can be constructed using a known composite amplifier with multiple operational amplifiers.

[0058] Furthermore, the integrating circuit 33 integrates the induced voltage V1 as described above to generate an integrated signal V1i, and outputs the generated integrated signal V1i to one input of the difference circuit 35. Also, the integrating circuit 34 integrates the induced voltage V2 as described above to generate an integrated signal V2i, and outputs the generated integrated signal V2i to the other input of the difference circuit 35.

[0059] The difference circuit 35 is configured, for example, with a known circuit configuration that includes an operational amplifier, and the output terminals of the integrating circuits 33 and 34 are connected to a pair of input terminals of this operational amplifier. With this configuration, the difference circuit 35 amplifies the difference voltage of the integrating signals V1i and V2i and outputs a difference signal Vd. On the other hand, external noise may enter the Rogowski coil 11, and this noise becomes common-mode noise and is superimposed on the induced electromotive forces V1 and V2 and included in the integrating signals V1i and V2i. In this case, since the induced electromotive forces V1 and V2 are voltages in opposite phases to each other, the difference circuit 35 cancels out and reduces the common-mode noise included in the integrating signals V1i and V2i by differential amplification of the integrating signals V1i and V2i, while adding and amplifying the induced electromotive forces V1 and V2, which are current signals generated due to the measurement current I flowing through the conductor 4 under measurement, to generate a difference signal Vd. Therefore, the difference signal Vd generated in the main body of the device 3 is a current signal with a sufficiently high signal-to-noise ratio.

[0060] Furthermore, in a typical configuration where one winding is wound around a core 12, the detection sensitivity of the Rogowski coil 11 may differ depending on the conductor position of the conductor 4 being measured due to uneven winding. On the other hand, in this device body 3, the difference circuit 35 adds the induced electromotive forces V1 and V2, so the detection voltage of the Rogowski coil 11 is essentially the average voltage of the induced electromotive forces V1 and V2 output from the two windings 13 and 14. As a result, even if there are uneven windings in the windings 13 and 14, the detection sensitivity of the Rogowski coil 11 is maintained at a constant level. Therefore, this current detection device 1 is capable of measuring the current value I1 of the measurement current I flowing through the conductor 4 being measured with high accuracy.

[0061] The amplification circuit 36 ​​is configured, for example, with an operational amplifier and functions as a high-pass filter that removes noise in the low-frequency range, such as offset voltage, contained in the difference signal Vd, while allowing the difference signal Vd in the high-frequency range to pass through. The amplification circuit 36 ​​also amplifies the difference signal Vd, which has had the low-frequency range noise removed, to generate a difference signal Vda, and outputs the generated difference signal Vda to the processing circuit 37.

[0062] The processing unit 37 is configured to include, for example, an A / D converter, a CPU, and memory (none of which are shown). In the processing unit 37, the A / D converter converts the input difference signal Vda into waveform data that shows its instantaneous value, and the CPU calculates (measures) the current value I1 of the measurement current I flowing through the conductor 4 to be measured based on this waveform data. The processing circuit 37 also outputs display data Dd for displaying the calculated current value I1 to the output unit 38.

[0063] The output unit 38 is, for example, composed of a display device such as an LCD provided in the case 31, and receives the display data Dd output from the processing unit 37 to display the current value I1 on the screen. The output unit 38 may be composed of various interface circuits instead of a display device. For example, a media interface circuit can be used to store the current value I1 on removable media, or a network interface circuit can be used to transmit the current value I1 to an external device via a network.

[0064] Next, the operation of the current detection device 1 will be explained in conjunction with the operation of the current sensor 2. It will be assumed that the current sensor 2 is already connected to the main unit 3 of the device.

[0065] First, the Rogowski coil 11 of the current sensor 2 is attached to the conductor 4 to be measured. In this case, when the current sensor 2 is connected to the main body 3, the insulated conductor 24 of the connecting cable 21 is set to the same potential as the reference potential G of the main body 3. Therefore, the potential of the return conductor 15 of the Rogowski coil 11 is also set to the same potential as the reference potential G of the main body 3.

[0066] In this state, the current detection device 1 first detects the measurement current I flowing through the conductor 4 to be measured using the Rogowski coil 11, and outputs induced electromotive forces V1 and V2 from windings 13 and 14, which change in voltage in proportion to the magnitude of the time variation (time derivative) of the current value I1 of the measurement current I, and are in opposite phase to each other. At this time, these induced electromotive forces V1 and V2 are input to the integrating circuits 33 and 34 in the main body of the device 3, respectively, via the insulated conductors 22 and 23 of the connecting cable 21.

[0067] In the main unit 3, the integrator PI in the integration unit 33 integrates the input induced electromotive force V1, and the integrator AI in the integration circuit 33 integrates the integrated signal output from integrator PI. As a result, the integration circuit 33 generates an integrated signal V1i whose voltage value changes in proportion to the voltage value of the measured current I, and outputs it to one input of the difference circuit 35. Also, the integrator PI in the integration unit 34 integrates the input induced electromotive force V2, and the integrator AI in the integration circuit 34 integrates the integrated signal output from integrator PI. As a result, the integration circuit 34 generates an integrated signal V2i whose voltage value changes in proportion to the voltage value of the measured current I and whose voltage is in the opposite phase to the integrated signal V1i, and outputs it to the other input of the difference circuit 35. Next, the difference circuit 35 amplifies the difference voltage of the input integrated signals V1i and V2i and outputs the generated difference signal Vd to the amplification circuit 36. In this case, the difference circuit 35 generates a difference signal of the integral signals V1i and V2i, thereby sufficiently removing the common-mode noise superimposed on the induced voltages V1 and V2. Furthermore, since the difference circuit 35 adds the signal component corresponding to the current value I1 of the measured current I in the integral signals V1i and V2i, a difference signal Vd with a sufficiently large signal level is generated. Next, the amplification circuit 36 ​​removes noise in the low-frequency region while amplifying the difference signal Vd in the high-frequency region, which has had the noise removed, and outputs the difference signal Vda to the processing circuit 37.

[0068] Next, the processing unit 37 calculates (measures) the current value I1 of the measurement current I based on the difference signal Vda. In this case, since noise is sufficiently removed from the difference signal Vda, the processing circuit 37 accurately calculates (measures) the current value I1 of the measurement current I. Also, since the induced electromotive forces V1 and V2 output from the windings 13 and 14 are stable with respect to the reference potential G on the main body 3 side, the processing circuit 37 stably measures the current value I1 of the measurement current I, which is a high-frequency current. Next, the processing circuit 37 outputs display data Dd that can display the current value I1 to the output unit 38. At this time, the output unit 38 displays the current value I1 on the screen based on the display data Dd output from the processing unit 37. This completes the current measurement of the current value I1 of the measurement current I.

[0069] Thus, in this current sensor 2 and the current detection device 1 equipped with this current sensor 2, the Rogowski coil 11 is arranged along the length direction of the winding core 12, and a return conductor 15 is provided, the tip portion 15b of which is connected to the tip portion 13b of the winding 13 and the tip portion 14b of the winding 14, and the base portion 15a of which is drawn out from one end A of the winding core 12. By setting the potential of the return conductor 15 and the reference potential G inside the device body 3 to the same potential, the polarity of the induced electromotive force V1 output from the winding 13 and the polarity of the induced electromotive force V2 output from the winding 14 can be made to be opposite polarities and stable voltages. Therefore, with this current sensor 2 and current detection device 1, for example, by obtaining the difference signal Vd of the integral signals V1i and V2i obtained by integrating the induced electromotive forces V1 and V2, the output signals (induced electromotive forces V1 and V2) of the Rogowski coil 11 output from windings 13 and 14 become stable with respect to the reference potential G on the device body 3 side. As a result, the current value I1 of the measurement current I, which is a high-frequency current, can be measured stably. Therefore, with this current sensor 2 and current detection device 1 equipped with this current sensor, the current value of AC currents over a wide frequency band can be measured stably.

[0070] Furthermore, the current sensor 2 and current detection device 1 can sufficiently remove common-mode noise superimposed on the induced voltages V1 and V2 by, for example, obtaining the difference signal Vd of the integral signals V1i and V2i obtained by integrating the induced voltages V1 and V2. Therefore, the current sensor 2 and current detection device 1 can measure the current value I1 of the measured current I with sufficiently high accuracy.

[0071] Furthermore, with this current sensor 2 and current detection device 1, by inserting the return conductor 15 into the center (inside) of the winding core 12, it is possible to eliminate or reduce the superposition of noise caused by an external magnetic field H onto the induced electromotive forces V1 and V2, for example, and as a result, the current value I1 of the measured current I can be measured with higher accuracy.

[0072] Furthermore, with this current sensor 2 and current detection device 1, by winding the windings 13 and 14 in a state where the upper and lower parts are alternately reversed, the symmetry of the detected induced voltages V1 and V2 can be sufficiently enhanced.

[0073] Furthermore, with this current sensor 2 and current detection device 1, by providing a connecting cable 21 in which insulated conductors 22 and 23 are twisted together, when the current sensor 2 is connected to the device body 3 via the connecting cable 21, the superposition of external noise on the induced electromotive forces V1 and V2 can be eliminated or reduced.

[0074] Furthermore, this current detection device 1 includes an integrating circuit 33 that generates an integrated signal V1i by integrating the induced electromotive force V1 output from the base end 13a of the winding 13, with the reference potential G set to the same potential as the return conductor 15; an integrating circuit 34 that generates an integrated signal V2i by integrating the induced electromotive force V2 output from the base end 14a of the winding 14, with the reference potential G set to the same potential as the return conductor 15; and a difference circuit 35 that generates a difference signal Vd, which is the difference signal between the integrated signals V1i and V2i. As a result, the output signals (induced electromotive forces V1, V2) of the Rogowski coils 11 output from the windings 13 and 14 can be stabilized relative to the reference potential G on the current detection device 1 (device body 3) side, and the current value I1 of the measurement current I, which is a high-frequency current, can be stably measured. Therefore, this current detection device 1 can stably measure the current value of AC currents over a wide frequency band. Furthermore, this current detection device 1 can sufficiently remove common-mode noise superimposed on the output signals (induced voltages V1, V2) of the Rogowski coil 11 by obtaining the difference signal Vd of the integral signals V1i and V2i obtained by integrating the output signals (induced voltages V1, V2) of the Rogowski coil 11. Therefore, with this current detection device 1, the current value I1 of the measured current I can be measured with sufficiently high accuracy.

[0075] Furthermore, with this current detection device 1, by configuring the integration circuits 33 and 34 with an active type integrator AI, it is possible to generate integrated signals V1i and V2i with sufficient gain.

[0076] Furthermore, this current detection device 1 incorporates an RC-type integrator PI that integrates the induced voltages V1 and V2 and outputs the result to an integrator AI, thereby configuring integration circuits 33 and 34. This allows for auxiliary integration of the induced voltages V1 and V2 up to higher frequencies. As a result, the integration circuits 33 and 34 as a whole can ideally integrate the induced voltages V1 and V2 from a low frequency fc1 to a higher frequency fc3. Therefore, this current detection device 1 enables current detection with excellent frequency characteristics for the measured current I.

[0077] Furthermore, this current detection device 1 includes a processing circuit 37 that detects the current value I1 of the measurement current I flowing through the conductor 4 to be measured, which is inserted into the Rogowski coil 11, based on a difference signal Vda. As a result, the processing circuit 37 can accurately and stably detect the current value I1 of the measurement current I based on the difference signal Vda.

[0078] Furthermore, since the current sensor 2 and current detection device 1 can sufficiently remove common-mode noise superimposed on the induced electromotive forces V1 and V2, a shielding conductor to shield the windings 13 and 14 of the Rogowski coil 11 is unnecessary. As a result, the Rogowski coil 11 can be made thinner using the current sensor 2 and current detection device 1, allowing the Rogowski coil 11 to be mounted in narrower locations for current measurement.

[0079] Specifically, this will be explained with reference to Figures 10 and 11. Figure 10 shows the configuration of the inverter 101, the axle motor 102, and the busbars 103A to 103C of the electric vehicle 100. In this electric vehicle 100, metal busbars 103A to 103C, which function as current passages, connect the inverter 101 and the motor 102 in order to supply current from the inverter 101 to the motor 102. In this case, the gap SP1 between busbar 103A and busbar 103B, and the gap SP2 between busbar 103B and busbar 103C are approximately 5 mm to 10 mm wide.

[0080] Therefore, for example, when measuring the current flowing through the busbar 103B, it is necessary to attach the Rogowski coil 11 to the busbar 103B, which is the conductor 4 to be measured. In this case, first, the other end B of the winding core 12 of the Rogowski coil 11 is passed through the gap SP2, the back side of the busbar 103B, and the gap SP1. Next, on the front side of the busbar 103B, the other end B of the winding core 12 is inserted into the opening formed on one end A, thereby attaching the Rogowski coil 11 to the busbar 103B in an annular shape. In this case, when using a Rogowski coil in which the windings 13 and 14 are shielded with a shield conductor, it becomes extremely difficult to pass the Rogowski coil through the gaps SP1 and SP2 because the gaps SP1 and SP2 are narrow. On the other hand, as shown in Figure 11, when using a Rogowski coil 11, since the Rogowski coil 11 is formed thinly without a shield conductor, the Rogowski coil 11 can be easily passed through the gaps SP1 and SP2.

[0081] Furthermore, this current sensor 2 and current detection device 1 eliminate the need for a shielding conductor to shield the windings 13 and 14, thus reducing the capacitance between the conductor 4 being measured and the windings 13 and 14. Consequently, the resonance frequency caused by the capacitance between the conductor 4 being measured and the windings 13 and 14, as well as the inductance of the windings 13 and 14, can be shifted to a higher frequency range, enabling current value measurement up to a higher frequency range.

[0082] Furthermore, this current sensor 2 and current detection device 1 eliminate the need for a shielding conductor to shield the windings 13 and 14, thereby improving the productivity of the Rogowski coil 11. As a result, the manufacturing cost of the Rogowski coil 11 can be significantly reduced, and furthermore, the manufacturing cost of the current sensor 2 and current detection device 1 can also be significantly reduced.

[0083] (Second Embodiment) In the Rogowski coil 11 described above, one winding 13 and one winding 14 are wound around the outer circumference of the core 12 with their upper and lower ends alternately reversed, but the configuration is not limited to this. For example, a configuration can be adopted in which two or more windings 13, 13... and two or more windings 14, 14... the same number as the winding 13 are wound around the outer circumference of the core 12 with their upper and lower ends alternately reversed. For example, a Rogowski coil 11A with the configuration shown in Figure 12 can be adopted. In this Rogowski coil 11A, as an example of multiple windings, two windings 13-1 and 13-2 are wound clockwise from one end A to the other end B of the core 12, and similarly, as an example of multiple windings, two windings 14-1 and 14-2 are wound counterclockwise from one end A to the other end B of the core 12. In this case, the windings 13-1, 13-2, 14-1, and 14-2 are connected at their tips on the other end B side of the core 12, and their base ends are drawn out from one end A side of the core 12. The return conductor 15 is arranged along the length of the core 12, and its tip 15b is connected to the tips of the windings 13-1, 13-2, 14-1, and 14-21, and its base end 15a is drawn out from one end A side of the core 12. In this Rogowski coil 11A as well, the two windings 13-1, 13-2 and the two windings 14-1, 14-2 are wound around the outer circumference of the core 12 in an alternating top-and-bottom arrangement. In Figures 12, 13 and Figures 15 to 19 described later, components having the same function as the components of the current detection device 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0084] As shown in Figures 12 and 13, the current sensor 2A equipped with the Rogowski coil 11A, and the current detection device 1A equipped with the current sensor 2A, are equipped with a connecting cable 21A. The connecting cable 21A is equipped with, for example, two sets of insulated conductors 22-1, 23-1, 22-2, 23-2, the same number as the number of windings 13-1, 13-2 and windings 14-1, 14-2 of the Rogowski coil 11A, one insulated conductor 24, and a covering 25 that covers each of the insulated conductors 22-1, 23-1, 22-2, 23-2, 24. In this case, the insulated conductors 22-1, 23-1 are twisted together, and the insulated conductors 22-2, 23-2 are also twisted together. Therefore, the connecting cable 21 is configured such that the insulated conductors 22-1, 23-1 and insulated conductors 22-2, 23-2 are twisted together, effectively preventing the superposition of external noise on the insulated conductors 22-1, 23-1, 22-2, 23-2. Of the two sets of insulated conductors 22-1, 23-1, 22-2, 23-2 extending from one end, one set of insulated conductors 22-1, 23-1 is connected to the windings 13-1, 14-1 of the Rogowski coil 11, and the other set of insulated conductors 22-2, 23-2 is connected to the windings 13-2, 14-2 of the Rogowski coil 11. In addition, insulated conductor 24 functions as a reference conductor for defining the potential of the return conductor 15 of the Rogowski coil 11 to a reference potential and is connected to the return conductor 15. Furthermore, two sets of insulated wires 22-1, 23-1, 22-2, and 23-2 extending from the other end are connected to the integrating circuits 33A and 34A within the main body of the device 3, as will be described later. In addition, insulated wire 24 is connected to the reference potential G of the main body of the device 3. Note that an uninsulated wire can be used instead of insulated wire 24.

[0085] Furthermore, as shown in Figure 13, the current detection device 1A is equipped with a device body 3A instead of the device body 3. The device body 3A is configured to be equipped with integrating circuits 33A and 34A instead of the integrating circuits 33 and 34 in the device body 3. The integrating circuit 33A corresponds to the first integrating circuit and is configured, for example, as shown in Figure 14, to be equipped with passive integrators PIa and PIb as the third integrator, and an active integrator AIA as the first integrator connected in series with integrators PIa and PIb. In this case, integrator PIa is, for example, an RC type integrator consisting of a resistor 41a and a capacitor 42a. Similarly, integrator PIb is an RC type integrator consisting of, for example, a resistor 41b and a capacitor 42b, and is configured with the same components as integrator PIa. Furthermore, the integrator AIA is configured, for example, with an operational amplifier 43, resistors 41a and 44a connected in series with the negative input terminal of the operational amplifier 43, resistors 41b and 44b connected in series with the negative input terminal of the operational amplifier 43, and a parallel circuit of a feedback resistor 45 and a capacitor 46 connected between the negative input terminal and the output terminal of the operational amplifier 43. In this case, the integrator AIA has an addition function and adds the induced electromotive force output from winding 13-1 of the Rogowski coil 11A and the induced electromotive force output from winding 14-1 of the Rogowski coil 11A to obtain an induced electromotive force V1, and then integrates it to output an integrated signal V1i. Furthermore, the integration circuit 34A corresponds to the second integration circuit and, as shown in the figure, is configured identically to the integration circuit 33A, comprising passive integrators PIa and PIb as the fourth integrator, and an active integrator AIA connected in series with integrators PIa and PIb as the second integrator. In other words, the amplification and frequency characteristics of the integrating circuit 34A are configured to have the same characteristics as those of the integrating circuit 33A.

[0086] In this current detection device 1A, windings 13-1 and 14-1 of the Rogowski coil 11A are connected to a pair of insulated conductors 22-1 and 23-1 of the connecting cable 21A, windings 13-2 and 14-2 are connected to a pair of insulated conductors 22-2 and 23-2, and the return conductor 15 is connected to the insulated conductor 24 of the connecting cable 21A. In addition, the insulated conductors 22-1 and 23-1 of the connecting cable 21A are connected to the two inputs of the integrating circuit 33A, and the insulated conductors 22-2 and 23-2 are connected to the two inputs of the integrating circuit 34A, and the insulated conductor 24 is connected to the reference potential G of the current detection device 1A.

[0087] When using this current detection device 1A to detect the measurement current I flowing through the conductor 4 to be measured, the integrating circuit 33A adds the induced electromotive force output from winding 13-1 of the Rogowski coil 11A and input via resistors 41a and 44a, and the induced electromotive force output from winding 14-1 of the Rogowski coil 11A and input via resistors 41b and 44b to obtain the induced electromotive force V1, and then integrates the induced electromotive force V1 to output the integrated signal V1i. In addition, the integrating circuit 34A adds the induced electromotive force output from winding 13-2 of the Rogowski coil 11A and input via resistors 41a and 44a, and the induced electromotive force output from winding 14-2 of the Rogowski coil 11A and input via resistors 41b and 44b to obtain the induced electromotive force V2, and then integrates the induced electromotive force V2 to output the integrated signal V2i. By using the Rogowski coil 11A with this configuration, even if there are winding irregularities in the windings 13-1, 14-1, 13-2, and 14-2, the detection sensitivity of the Rogowski coil 11A can be maintained at a constant level.

[0088] (Third Embodiment) Alternatively, instead of current sensor 2, current sensor 2B shown in Figure 15 can be used. Current sensor 2B is configured with a Rogowski coil 11B instead of the Rogowski coil 11. In this case, in addition to the configuration of the Rogowski coil 11, the Rogowski coil 11B is configured with a mesh-like shielding conductor 16 that shields the windings 13, 14 and return conductor 15 wound around the core 12, and a covering 17 that covers the shielding conductor 16.

[0089] With this current sensor 2B and current detection device 1B equipped with the current sensor 2B, although the measurable frequency range is lower compared to the current sensor 2 and current detection device 1 without the shield conductor 16, the current sensor 2 and current detection device 1 are less susceptible to external noise interference.

[0090] (Fourth Embodiment) Alternatively, instead of the connection cable 21, the connection cable 21B shown in Figure 16 can be used. The connection cable 21B has a mesh-like shielding conductor 26 that shields the insulated conductors 22 and 23, instead of the insulated conductor 24 in the connection cable 21. In this connection cable 21B, the insulation 25 covers the shielding conductor 26. In this case, when using the connection cable 21, the return conductor 15 of the Rogowski coil 11 and the reference potential G of the device body 3 are connected by the insulated conductor 24, but when using this connection cable 21B, the return conductor 15 and the reference potential G can be connected by the shielding conductor 26.

[0091] With a current sensor 2C equipped with a connecting cable 21B instead of the connecting cable 21, and a current detection device 1C equipped with a current sensor 2C instead of the current sensor 2, the inclusion of a shield conductor 26 allows the current sensor 2C (Rogowski coil 11) and the current detection device 1C (device body 3) to be connected by the connecting cable 21B, making them less susceptible to external noise interference to the induced electromotive forces V1 and V2, and allowing the potential of the return conductor 15 to be set to the same potential as the reference potential G of the current detection device 1C (device body 3). Alternatively, a connecting cable having both a covered conductor 24 and a shield conductor 26 can be used instead of the connecting cable 21B.

[0092] (Fifth Embodiment) In addition, instead of the configurations of the Rogowski coils 11, 11A, and 11B in which windings 13, 14 and windings 13-1, 13-2, 14-1, and 14-2 are wound with the top and bottom alternating, the Rogowski coil 11D shown in Figure 17 can also be used. In this Rogowski coil 11D, windings 13 and 14 are wound without the top and bottom alternating, and the average winding pitch of the upper winding of either winding 13 or winding 14 is larger (wider) than the average winding pitch of the lower winding of the other winding 13 or winding 14.

[0093] Specifically, in Figure 17, as an example, the Rogowski coil 11D is constructed by first winding winding 13 as the lower winding, and then winding 14, the other winding, is wound on top of winding 13 as the upper winding. In this case, windings 13 and 14 are wound such that the average winding pitch t2 of winding 14 is greater than the average winding pitch t1 of winding 13. In other words, in this Rogowski coil 11D, the number of turns of winding 13 is greater than the number of turns of winding 14. The ratio of average winding pitches t1 and t2 is specified such that, for example, when the average winding pitch t1 is set to a value of "1", the average winding pitch t2 is between a value of "1.1" and a value of "10".

[0094] Generally, when measuring the current of an inverter device, there is a signal component due to the measured current I and a noise component that enters the Rogowski coil from the outside through capacitive coupling. When external noise enters the Rogowski coil, the upper winding is more susceptible to noise than the lower winding. For this reason, in the Rogowski coil 11D and the current sensor 2D equipped with the Rogowski coil 11D, the winding of windings 13 and 14 is adjusted so that the amount of external noise received by the upper winding 14 and the amount of external noise received by the lower winding 13 are the same. Specifically, in the Rogowski coil 11D and the current sensor 2D, the average winding pitch t2 of winding 14 is larger than the average winding pitch t1 of winding 13, thereby adjusting the number of turns (winding method) of each winding 13 and 14 so that the amount of external noise received by winding 14 and the amount of external noise received by winding 13 are the same.

[0095] On the other hand, in the connecting cable 21, since the insulated conductors 22 and 23 are twisted together, the same amount of external noise is superimposed. In this case, the signals output from the two insulated conductors 22 and 23 have induced voltages V1 and V2, which are differential signals due to the measured current I, in opposite phase, while the external noise is in phase. Therefore, the integrating circuits 33 and 34 and the difference circuit 35 on the main body 3 cancel out and reduce the common-phase noise, while adding and amplifying the induced voltages V1 and V2, which are current signals generated due to the measurement current I flowing through the conductor 4 under measurement, to generate a difference signal Vd. Consequently, the current sensor 2D and the current detection device 1D equipped with the current sensor 2D can generate a difference signal Vd, which is a current signal with a sufficiently high S / N ratio, and as a result, the current value I1 of the measured current I can be measured with sufficiently high accuracy.

[0096] (Sixth Embodiment) Alternatively, the Rogowski coil 11E shown in Figure 18 can be used. In this Rogowski coil 11E, the windings 13 and 14 are wound in such a way that the upper and lower windings do not alternate, and the average winding pitch of the upper winding of either winding 13 or winding 14 is equal to the average winding pitch of the lower winding of the other winding.

[0097] Furthermore, the integrating circuits 33 and 34 shown in Figure 3 can also be configured to allow for the modification of the resistance ratio RR1 between the resistance value of resistor 45 and resistor 44 in integrating circuit 33, and the resistance ratio RR2 between the resistance value of resistor 45 and resistor 44 in integrating circuit 34. In this configuration, the integrating circuits 33 and 34 function as signal ratio adjustment circuits.

[0098] Specifically, in the integrating circuits 33 and 34, when the magnitudes of the integrated signal V1i (first integrated signal) and the integrated signal V2i (second integrated signal) differ due to differences in the magnitude of the induced electromotive force V1 output from the base end 13a and the magnitude of the induced electromotive force V2 output from the base end 14a, the magnitudes of the integrated signals V1i and V2i can be adjusted to be the same by adjusting the resistance ratio RR1 and RR2 to match the amplification of the integrating circuit 34 relative to the amplification of the integrating circuit 33. In other words, the ratio of the magnitude of the integrated signal V2i to the magnitude of the integrated signal V1i (in this case, the same ratio) can be adjusted. Therefore, it is possible to configure the current detection device 1 without a signal ratio adjustment circuit. However, with current sensors 2, 2A to 2D equipped with the integration circuits 33 and 34 in this configuration, and current detection devices 1, 1A to 1D equipped with these current sensors 2, 2A to 2D, as well as current sensors 2E and 2F described later, and current detection devices 1E and 1F equipped with these current sensors 2E and 2F, it is possible to substantially balance the detection sensitivity of the winding 13 for the integrated signal V1i and the detection sensitivity of the winding 14 for the integrated signal V2i.

[0099] Furthermore, in the Rogowski coil 11E, the current sensor 2E equipped with the Rogowski coil 11E, and the current detection device 1E equipped with the current sensor 2E, when the magnitudes of the induced electromotive force V1 and the induced electromotive force V2 output from the Rogowski coil 11E differ due to the winding of the windings 13 and 14 being wound so that the upper and lower parts do not alternate, the magnitudes of the integral signal V1i (first integral signal) and the integral signal V2i (second integral signal) can be adjusted to be the same by adjusting the resistance ratios RR1 and RR2.

[0100] Furthermore, the configuration of the signal ratio adjustment circuit is not limited to the above example; any configuration that allows for individual setting of the amplification (or attenuation) of induced voltage V1 and induced voltage V2 can be adopted. For example, the signal ratio adjustment circuit can be configured by providing an amplification circuit that amplifies induced voltage V1 and an amplification circuit that amplifies induced voltage V2, and changing the gain of both amplification circuits. Alternatively, the signal ratio adjustment circuit can be configured by amplifying only one of induced voltages V1 or V2, and not amplifying the other of induced voltages V1 or V2. In addition, the location where the signal ratio adjustment circuit is installed can be arbitrarily determined; it may be on the current sensor 2, 2A to 2F side, or on the device body 3, 3A side.

[0101] (Seventh Embodiment) Furthermore, the winding method of windings 13 and 14 is not limited to the above example. For example, as shown in Figure 19, the Rogowski coil 11F is constructed such that a portion of the winding of winding 13 and a portion of the winding of winding 14 are wound alternately in an alternating pattern, as shown in the left figure of the same figure, similar to the Rogowski coil 11 shown in Figure 2, while the other portions of the winding of winding 13 and a portion of the winding of winding 14 are wound alternately in an alternating pattern, as shown in the right figure of the same figure, similar to the Rogowski coil 11D shown in Figure 17, and the average winding pitch of the upper winding of either winding 13 or winding 14 is greater than the average winding pitch of the other lower winding of winding 14. In this case, the portions of winding 13 and 14, and the other portions of winding 13 and 14, may be defined at any location along the length of the winding core 12. With the current sensor 2F equipped with the Rogowski coil 11F in this configuration, and the current detection device 1F equipped with the current sensor 2F, it is possible to generate a difference signal Vd, which is a current signal with a sufficiently high S / N ratio, in the same manner as the current detection devices 1, 1A to 1E. As a result, the current value I1 of the measured current I can be measured with sufficiently high accuracy.

[0102] Alternatively, instead of the configuration shown in the right-hand figure of Figure 19, a configuration can be adopted in which the Rogowski coil 11E is wound in a manner similar to that shown in Figure 18, where the upper and lower windings are not alternately reversed, and the average winding pitch of the upper winding of either winding 13 or winding 14 is equal to the average winding pitch of the lower winding of the other winding of winding 13 or winding 14. With a current sensor 2F equipped with a Rogowski coil 11F of this configuration, and a current detection device 1F equipped with a current sensor 2F, by making the integrating circuits 33 and 34 function as signal ratio adjustment circuits, a difference signal Vd, which is a current signal with a sufficiently high S / N ratio, can be generated in the same manner as the current detection devices 1, 1A to 1E, and as a result, the current value I1 of the measured current I can be measured with sufficiently high accuracy.

[0103] Furthermore, as described above, the Rogowski coil can be constructed using not only one or two windings 13 and 14, but also three or more windings. In addition, although the Rogowski coils 11, 11A, and 11B have been described in which windings 13 and 14 or windings 13-1, 13-2, 14-1, and 14-2 are wound in a single layer, Rogowski coils can also be constructed in which windings 13 and 14 or windings 13-1, 13-2, 14-1, and 14-2 are wound in two or more layers using the same winding method.

[0104] Furthermore, as shown in Figure 20, instead of the configuration of integrating circuits 33, 34 and difference circuit 35, a differential integrating circuit 51 can be adopted, which uses a single operational amplifier to integrate an integrating circuit that integrates the induced electromotive forces V1 and V2, and a difference circuit that amplifies the difference voltage of the integrated signal to generate a difference signal Vd. This differential integrating circuit 51 is configured with a single operational amplifier 52, a resistor 53 connected to the negative input terminal of the operational amplifier 52, a parallel circuit of a feedback resistor 54 and a capacitor 55 connected between the negative input terminal and the output terminal of the operational amplifier 52, a resistor 56 connected to the positive input terminal of the operational amplifier 52, and a parallel circuit of a resistor 57 and a capacitor 58 connected between the positive input terminal of the operational amplifier 52 and the reference potential G.

[0105] Furthermore, while we have described a current detection device equipped with a current sensor as an example of a current detection device that measures the current value I1 of the measured current I, a current detection device equipped with a current sensor can also be configured as various other measuring devices, such as a power detection device.

[0106] According to the present invention, the polarities of the first and second output signals output from the first and second windings can be made opposite to each other and stable voltages. By obtaining the difference signals of the first and second integral signals obtained by integrating the first and second output signals, the first and second output signals become stable with respect to the reference potential on the current detection device side. As a result, the current value of the measurement current, which is a high-frequency current, can be measured stably. Therefore, according to the present invention, the current value of AC currents over a wide frequency band can be measured stably. Consequently, the present invention can be widely applied to current sensors and current detection devices for measuring the current value of such measurement currents.

[0107] 1. 1A to 1F Current detection device 2. 2A to 2F Current sensor 3. 3A Device body 4 Conductors to be measured 11. 11A to 11F Rogowski coil 12 Core 13. 13-1, 13-2, 14. 14-1, 14-2 Winding 15 Return conductor 21. 21A, 21B Connecting cable 22. 22-1, 22-2, 23. 23-1, 23-2, 24 Insulated conductor 26 Shield conductor 33. 33A, 34, 34A Integrating circuit 35 Differential circuit 37 Processing circuit I Measured current I1 Current value V1, V2 Induced electromotive force V1i, V2i Integrating signal Vd Differential signal

Claims

1. A current sensor comprising a Rogowski coil having a rod-shaped core, a first winding wound clockwise from one end to the other of the core, and a second winding wound counterclockwise from one end to the other of the core, wherein the tip of the first winding and the tip of the second winding are connected to each other at the other end of the core, and the base end of the first winding and the base end of the second winding are drawn out from the one end of the core, wherein the Rogowski coil is arranged along the length direction of the core and has a return wire whose tip is connected to the tip of the first winding and the tip of the second winding, and whose base end is drawn out from the one end of the core.

2. The current sensor according to claim 1, wherein the return wire is inserted inside the winding core.

3. The current sensor according to claim 1, wherein the first winding and the second winding are wound in an alternating up-and-down manner.

4. The current sensor according to claim 1, wherein the first winding and the second winding are wound in a manner that does not alternate between upper and lower positions.

5. The current sensor according to claim 4, wherein the first winding and the second winding are wound such that the average winding pitch of the upper winding of either the first winding or the second winding is greater than the average winding pitch of the lower winding of the other of the first winding or the second winding.

6. The current sensor according to claim 1, wherein some winding portions of the first winding and some winding portions of the second winding are wound with their upper and lower sides alternating, and other winding portions of the first winding and other winding portions of the second winding are wound without their upper and lower sides alternating, and the average winding pitch of the upper winding of either the first winding or the second winding is greater than the average winding pitch of the lower winding of the other of the first winding or the second winding.

7. The current sensor according to claim 1, further comprising a shielding conductor for shielding the Rogowski coil.

8. The current sensor according to claim 1, comprising a first insulated wire connected to the base end of the first winding and a second insulated wire connected to the base end of the second winding, and further comprising a connecting cable in which the first insulated wire and the second insulated wire are twisted together.

9. The current sensor according to claim 7, wherein the connecting cable is configured to be set to the same potential as the return line and includes a shielding conductor that shields the first insulated wire and the second insulated wire.

10. A current detection device comprising: the current sensor according to any one of claims 1 to 9; a first integrating circuit configured to have a reference potential set to the same potential as the return wire potential and to integrate a first output signal of the Rogowski coil output from the base end of the first winding to generate a first integral signal; a second integrating circuit configured to have a reference potential set to the same potential as the return wire potential and to integrate a second output signal of the Rogowski coil output from the base end of the second winding to generate a second integral signal; and a difference circuit to generate a difference signal between the first integral signal and the second integral signal.

11. The current detection device according to claim 10, wherein the first integrating circuit is configured to include an active first integrator, and the second integrating circuit is configured to include an active second integrator.

12. The current detection device according to claim 11, wherein the first integrating circuit is configured to include an RC-type third integrator that integrates the first output signal and outputs it to the first integrator, and the second integrating circuit is configured to include an RC-type fourth integrator that integrates the second output signal and outputs it to the second integrator.

13. The current detection device according to claim 10, further comprising a signal ratio adjustment circuit for adjusting the ratio of the magnitude of the second integral signal to the magnitude of the first integral signal.

14. The current detection device according to claim 13, wherein the signal ratio adjustment circuit adjusts the ratio by adjusting the magnitude of the amplification of the second integrating circuit relative to the magnitude of the amplification of the first integrating circuit.

15. The current detection device according to claim 10, further comprising a processing unit that detects the current value of the current flowing through the conductor to be measured, which is inserted through the Rogowski coil, based on the difference signal.

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