JP2024087768A - Current sensor and measuring device - Google Patents

Abstract

To raise the current detection accuracy of a current sensor.SOLUTION: A current sensor 100 includes an annular magnetic core 10, a pair of windings 11 and 21 that are composed of a plurality of winding parts connected in series and wound around the magnetic core 10 in mutually difference sections, and a plurality of resistive elements 12 and 22 that are respectively connected in parallel for each winding, and for each of winding parts of the winding. The current sensor 100 includes a return wire 13, of which one end is connected to one end 1a of the winding 11 and the other end 1c extends from the one end 1a of the winding 11 to near the position of the other end 1b along a section of the magnetic core 10 where the winding 11 is wound, and a return wire 23, of which one end is connected to one end 2a of the winding 21 and the other end 2c extends from the one end 2a of the winding 21 to near the position of the other end 2b along a section of the magnetic core 10 where the winding 21 is wound. The current sensor 100 outputs a signal indicting the difference between the outputs of the winding 11 and the return wire 13 and the outputs of the winding 21 and the return wire 23.SELECTED DRAWING: Figure 2

Description

The present invention relates to a current sensor and a measuring device.

Patent document 1 discloses a transformer in which the windings wound around a magnetic core are composed of multiple winding sections connected in series, and each winding section has a damping resistor connected in parallel.

U.S. Pat. No. 3,146,417

The winding in this transformer is made up of multiple winding sections connected in series, and as a whole the winding forms a one-turn loop in the toroidal direction. This one-turn loop detects external magnetic flux, such as magnetic fields and electromagnetic waves entering from the outside, resulting in poor current detection accuracy.

The present invention was developed to address these issues and aims to improve current detection accuracy.

According to one aspect of the present invention, the current sensor includes a ring-shaped magnetic core and a pair of windings consisting of a first winding and a second winding that are wound in the poloidal direction along the toroidal direction on different parts of the magnetic core to detect the current flowing through the measurement object, a plurality of resistance elements that are connected in parallel to each of the winding parts, a first return wire having one end connected to one end of the first winding and the other end extending from one end of the first winding to the vicinity of the position of the other end of the first winding along the toroidal direction of the part of the magnetic core around which the first winding is wound, and a second return wire having one end connected to one end of the second winding and the other end extending from one end of the second winding to the vicinity of the position of the other end of the second winding along the toroidal direction of the part of the magnetic core around which the second winding is wound, and outputs a signal indicating the difference between the output of the first winding and the first return wire and the output of the second winding and the second return wire.

In this embodiment, the first and second windings constituting a pair of windings are wound in the poloidal direction along the toroidal direction on different parts of the magnetic core. Furthermore, a first return wire connected to one end of the first winding is aligned with the toroidal direction of the wound part of the first winding and extends from one end of the first winding to the vicinity of the position of the other end of the first winding. Furthermore, a second return wire connected to one end of the second winding is aligned with the toroidal direction of the wound part of the second winding and extends from one end of the second winding to the vicinity of the position of the other end of the second winding.

Therefore, when the difference between the magnetism generated in the first winding and the first return wire and the magnetism generated in the second winding and the second return wire is taken as the difference between the output of the first winding and the first return wire and the output of the second winding and the second return wire, the external magnetic flux detected by the first winding and the first return wire can be at least partially cancelled by the magnetic flux generated by the second winding and the second return wire, and the current detection accuracy can be improved. Or, when the difference between the output of the first winding and the first return wire and the output of the second winding and the second return wire is taken as the difference between the electric signal output through the first winding and the first return wire and the electric signal output through the second winding and the second return wire, the noise due to the external magnetic flux of the electric signal output through the first winding and the first return wire can be at least partially cancelled by the noise due to the external magnetic flux of the electric signal output through the second winding and the second return wire, and the current detection accuracy can be improved.

FIG. 1 is a diagram showing the configuration of a measurement device including a current sensor according to a first embodiment. FIG. 2 is a schematic diagram illustrating a configuration example of the current sensor according to the first embodiment. FIG. 3 is a circuit diagram showing an equivalent circuit of the current sensor shown in FIG. FIG. 4 is a diagram for explaining the operation of the current sensor of the first embodiment. FIG. 5 is a diagram illustrating the flatness of the amplitude frequency characteristics of the current sensor of the first embodiment. FIG. 6 is a diagram illustrating an example of the configuration of a current sensor according to the second embodiment. FIG. 7 is a diagram illustrating an example of the configuration of a current sensor according to the third embodiment. FIG. 8 is a diagram illustrating an example of the configuration of a current sensor according to the fourth embodiment. FIG. 9 is a circuit diagram showing an equivalent circuit of the current sensor shown in FIG. FIG. 10 is a diagram illustrating an example of the configuration of a current sensor according to the fifth embodiment. FIG. 11 is a schematic diagram showing a configuration example of a current sensor according to the sixth embodiment.

Each embodiment of the present invention will be described below with reference to the accompanying drawings. In this specification, the same or equivalent elements are designated by the same reference numerals throughout.

First Embodiment
FIG. 1 is a diagram showing the configuration of a measurement device 1 according to the first embodiment.

The measuring device 1 is a device for measuring a physical quantity of a measuring object Lm. The measuring object Lm is, for example, an electric circuit through which an AC measuring current Im flows, and an example of this electric circuit is a single-phase or three-phase power cable. In addition, examples of the physical quantity of the measuring object Lm include a current value, a magnetic flux value, and a power value.

The measuring device 1 measures the magnitude of the measurement current Im, which indicates the current flowing through the measurement object Lm. The measuring device 1 includes a current sensor 100 and a measuring unit 200.

The current sensor 100 is a sensor that detects a measurement magnetic flux that indicates a magnetic flux created by an AC measurement current Im. The current sensor 100 outputs a voltage obtained by detecting the measurement magnetic flux as a detection amount to the measurement unit 200.

The current sensor 100 has a magnetic core with one or more windings housed in a case. The current sensor 100 may have a through-type structure that passes through the object to be measured Lm, or may have a clamp-type structure that can be opened and closed.

For example, the current sensor 100 is realized by a winding detection type current sensor that performs a CT (current transformer) operation to obtain the detection amount applied to the measurement current Im. Alternatively, the current sensor 100 may be realized by a winding detection type current sensor that employs an AC zero flux method (magnetic balance method) that includes a magnetic detection element such as a fluxgate or a Hall element.

The current sensor 100 is provided with a cable 110. The cable 110 is realized, for example, by a coaxial cable with a characteristic impedance of 50 [Ω] or 75 [Ω]. The tip of the cable 110 is connected to the measuring unit 200.

The measurement unit 200 calculates a measurement quantity for the measurement object Lm based on the detection quantity detected by the current sensor 100. The measurement unit 200 of the first embodiment calculates the current value of the measurement current Im flowing through the measurement object Lm based on the detection quantity indicating the magnitude of the voltage obtained by the current sensor 100. The measurement unit 200 is realized by, for example, a power analyzer, a current measuring device, or a magnetic field measuring device.

Next, the configuration of the current sensor 100 of the first embodiment will be described with reference to Figures 2 and 3.

Figure 2 is a schematic diagram showing the configuration of the current sensor 100.

The current sensor 100 comprises a magnetic core 10, a winding 11, a plurality of resistive elements 12, a return wire 13, a winding 21, a plurality of resistive elements 22, a return wire 23, and a differential circuit 30. As described in FIG. 1, these components are housed in a case (not shown).

The magnetic core 10 is formed so that the measurement object Lm can be inserted therethrough. Specifically, the overall shape of the magnetic core 10 is formed in an annular shape so as to surround the measurement object Lm. The annular shape includes a circular shape, an elliptical shape, a rectangular shape, and a polygonal shape. The magnetic core 10 is made of an iron material such as permalloy. Instead of this iron material, the magnetic core 10 may have a hollow structure. The magnetic core 10 may also have a structure that can be separated.

The windings 11 and 21 are a pair of windings wound in a toroidal direction on different parts of the magnetic core 10. In the first embodiment, the different parts are composed of the first magnetic core part 10a and the second magnetic core part 10b.

Specifically, the winding 11 is a first winding wound in a poloidal direction along the toroidal direction of the magnetic core 10. The winding 21 is a second winding wound in a poloidal direction along the toroidal direction of the magnetic core 10 in a second magnetic core portion 10b of the magnetic core 10 that is different from the first magnetic core portion 10a around which the winding 11 is wound.

In the first embodiment, the pair of windings 11 and 21 are wound so that the direction from one end 1a of the winding 11 to the other end 1b of the winding 11 and the direction from one end 2a of the winding 21 to the other end 2b of the winding 21 are opposite to each other in the toroidal direction of the magnetic core 10. Specifically, the winding 11 is wound along the toroidal direction of the magnetic core 10 in the direction from one end 1a to the other end 1b of the winding 11, and the winding 21 is wound along the toroidal direction of the magnetic core 10 in the opposite direction to the direction from one end 1a to the other end 1b of the winding 11. Also, the winding 21 is wound in the opposite direction to the direction in which the winding 11 is wound in the poloidal direction of the magnetic core 10. In this way, the winding 11 and the winding 21 are in a forward winding and reverse winding relationship, respectively.

The pair of windings 11 and 21 are arranged opposite each other so as to bisect the magnetic core 10 when viewed from above, so as to improve the linear symmetry of the two in the radial direction of the magnetic core 10. In the first embodiment, the pair of semicircular windings 11 and 21 are arranged opposite each other.

One end 1a of the winding 11 is connected to the return wire 13, and the other end 1b of the winding 11 is connected to the reference potential G. Similarly, one end 2a of the winding 21 is connected to the return wire 23, and the other end 2b of the winding 21 is connected to the reference potential G.

The pair of windings 11 and 21 have multiple winding sections connected in series. The winding 11 has a resistance element 12 connected in parallel to each winding section. Similarly, the winding 21 has a resistance element 22 connected in parallel to each winding section.

The return wires 13 and 23 are a pair of return wires that return from one end of each of the pair of windings 11 and 21 to the other end in opposite directions along the toroidal direction of the portion of the magnetic core 10 on which the winding is wound.

Specifically, the return wire 13 extends from one end 1a of the winding 11 along the toroidal direction of the first magnetic core part 10a around which the winding 11 of the magnetic core 10 is wound, and returns toward the other end 1b of the winding 11. Similarly, the return wire 23 extends from one end 2a of the winding 21 along the toroidal direction of the second magnetic core part 10b around which the winding 21 of the magnetic core 10 is wound, and returns toward the other end 2b of the winding 21.

That is, the return wire 13 has one end connected to one end 1a of the winding 11, and the other end 1c of the return wire 13 constitutes a first return wire that extends from one end 1a of the winding 11 to the vicinity of the position of the other end 1b of the winding 11 along the toroidal direction of the first magnetic core part 10a around which the winding 11 is wound in the magnetic core 10. Also, the return wire 23 constitutes a second return wire that has one end connected to one end 2a of the winding 21, and the other end 2c of the return wire 23 constitutes a second return wire that extends from one end 2a of the winding 21 to the vicinity of the position of the other end 2b of the winding 21 along the toroidal direction of the second magnetic core part 10b around which the winding 21 is wound in the magnetic core 10.

The differential circuit 30 is a differential amplifier circuit that outputs the difference between the electrical signal output from the winding 11 and the return wire 13 and the electrical signal output from the winding 21 and the return wire 23.

In the first embodiment, the differential circuit 30 is realized by a differential amplifier circuit. The other end 1c of the return line 13 is connected to the inverting input terminal (-) of the differential circuit 30, and the other end 2b of the winding 21 is connected to the non-inverting input terminal (+) of the differential circuit 30. The other end 2c of the return line 23 extending from one end 2a of the winding 21 is connected to the reference potential G. The other end 1b of the winding 11 is also connected to the reference potential G.

The differential circuit 30 outputs and amplifies the difference between the voltage signal output from the winding 11 via the return line 13 and the voltage signal output from the return line 23 via the winding 21. Alternatively, the current sensor 100 may be configured so that the differential circuit 30 outputs and amplifies the difference between the voltage signal output from the return line 13 via the winding 11 and the voltage signal output from the winding 21 via the return line 23.

In this way, the differential circuit 30 outputs a signal indicating the difference between the voltage signal output through the winding 11 and the return wire 13 and the voltage signal output through the winding 21 and the return wire 23.

The differential circuit 30 generates an output signal indicating the magnitude of the difference between the voltage signal output through the winding 11 and the return wire 13 and the voltage signal output through the winding 21 and the return wire 23, and outputs the generated output signal to the measurement unit 200 as the output signal Vout of the current sensor 100.

Next, the connection relationship of the current sensor 100 will be explained with reference to FIG. 3.

Figure 3 is a circuit diagram showing an example of an equivalent circuit that simulates the electrical characteristics of the current sensor 100 of the first embodiment. In Figure 3, the four sections of the winding 11 are shown as winding sections 11a to 11d, and the four sections of the winding 21 are shown as winding sections 21a to 21d.

As shown in FIG. 3, winding sections 11a to 11d are wound with polarity opposite to that of winding sections 21a to 21d. The inductance of each of winding sections 11a to 11d and winding sections 21a to 21d is set to a value within the range of, for example, 1 nF to 10 F.

For each of the winding sections 11a to 11d, the resistive elements 12 are connected in parallel and the resistive elements 12 are connected in series.For each of the winding sections 21a to 21d, the resistive elements 22 are connected in parallel and the resistive elements 22 are connected in series.

The resistance values of the series resistor element 12 and the series resistor element 22 are set to values within the range of, for example, 1 [Ω] to 100 [Ω].

In the first embodiment, the inductances of the windings 11a to 11d are set to be equal so that the detection sensitivities of the windings are equal to each other, and similarly, the inductances of the windings 21a to 21d are also set to be equal to each other.

Furthermore, the resistance values of the four resistive elements 12 and 22 are set to be equal so that the detection sensitivity of the windings is equal to each other, and similarly, the resistance values of the four resistive elements 22 are also set to be equal.

In addition, to ensure linear symmetry between the pair of windings 11 and 21, the inductances of winding sections 11a to 11d and winding sections 21a to 21d are set equal, and the resistance values of resistive element 12 and resistive element 22 are set equal.

In the first embodiment, four resistive elements 12 are connected in parallel in the winding 11, but this is not limited to the above. For example, two, three, or five or more resistive elements 12 may be connected in parallel in the winding 11. The same applies to the winding 21.

Next, the operation of the current sensor 100 will be explained.

As shown in FIG. 2, the current sensor 100 has a pair of windings 11 and 21 arranged opposite each other so that the magnetic core 10 is divided into two equal parts when viewed from above, improving the linear symmetry of the pair of windings. In the first embodiment, the pair of semicircular windings 11 and 21 are arranged opposite each other. This ensures that the detection sensitivity of the measurement magnetic flux by the windings 11 and 21 is approximately the same.

In addition, in the current sensor 100, the pair of windings 11 and 21 each function as a current transformer. That is, the pair of windings 11 and 21 each convert the measurement magnetic flux generated in the magnetic core 10 by the measurement current Im shown in FIG. 1 into a current.

The current sensor 100 is a series impedance element in which multiple resistance elements 12 are connected in series. The multiple resistance elements 12 function as load resistors that convert the induced current flowing through the winding portions 11a to 11d of the winding 11, which are connected in parallel, into a voltage. The multiple resistance elements 12 also function as damping resistors to suppress deterioration of frequency characteristics caused by resonance between the inductance of the winding 11 and the capacitance parasitic to the winding 11. The same applies to the multiple resistance elements 22.

Figure 4 is a diagram to explain the current and magnetic flux generated in the current sensor 100.

When a current flows through winding 11, which is part of a one-turn loop, due to an external magnetic flux, etc., and flows through winding 21, which is the other part of the one-turn loop, a magnetic flux in the opposite direction to the external magnetic flux, etc. is generated, which cancels out at least a part of the in-phase component of the external magnetic flux, etc. Furthermore, when a current flows through return wire 13, which is part of a one-turn loop, due to an external magnetic flux, etc., and flows through return wire 23, which is the other part of the one-turn loop, a magnetic flux in the opposite direction to the external magnetic flux, etc. is generated, which cancels out at least a part of the in-phase component of the external magnetic flux, etc.

When the measurement object Lm is inserted into the magnetic core 10, a measurement magnetic flux φm is generated in the magnetic core 10 by a measurement current Im flowing through the measurement object Lm. The generation of the measurement magnetic flux φm causes an induced current proportional to the measurement magnetic flux φm to flow in each of the pair of windings 11 and 21.

In the following, the magnetic flux generated by the current components of the induced current flowing through the pair of windings 11 and 21, mainly in the toroidal direction of the magnetic core 10, is referred to as "parasitic magnetic flux". The magnetic flux generated by the current flowing through the pair of return wires 13 and 23 is also referred to as "parasitic magnetic flux". These parasitic magnetic fluxes are generated toward the center of the annular magnetic core 10, that is, in the direction in which the measurement object Lm is inserted. In this specification, external magnetic flux, etc. includes parasitic magnetic flux.

Then, a parasitic magnetic flux φp1 is generated in the insertion direction of the measurement object Lm due to a current component Ip1 in the toroidal direction of the magnetic core 10, which is part of the induced current flowing through the winding 11. Similarly, a parasitic magnetic flux φp2 is generated in the insertion direction of the measurement object Lm due to a current component Ip2 in the toroidal direction flowing through the winding 21.

At this time, the current component Ip1 flowing through the winding 11 generates a parasitic magnetic flux φp1 caused by the winding 11 so as to cancel out the parasitic magnetic flux φp2 caused by the winding 21. Similarly, the current Ir1 flowing through the return wire 13 of the winding 11 generates a parasitic magnetic flux φr1 caused by the return wire 13 so as to cancel out the parasitic magnetic flux φr2 caused by the return wire 23.

In this way, by arranging a pair of windings 11 and 21, the parasitic magnetic fluxes φp1 and φp2 caused by the pair of windings 11 and 21 act to cancel each other out. In addition, by arranging a pair of return wires 13 and 23, the parasitic magnetic fluxes φr1 and φr2 created by the pair of return wires 13 and 23 act to cancel each other out.

Even with this configuration, it may not be possible to cancel out the parasitic magnetic fluxes φp1 and φp2 due to misalignment of the pair of windings 11 and 21, misalignment of the pair of return wires 13 and 23, or differences in the detection sensitivity and parasitic capacitance of external magnetic flux due to differences in the number of turns of the pair of windings 11 and 21.

The residual magnetic flux of the parasitic magnetic fluxes φp1 and φp2 that could not be canceled as described above is detected in the pair of windings 11 and 21 as common mode noise.

Specifically, at both ends (1a and 1b) of the winding 11, a positive voltage (+Vm) caused by the measurement magnetic flux φm and a positive voltage ΔVn caused by the residual magnetic flux are superimposed as common mode noise. On the other hand, since the winding 11 is wound so that the direction from one end 1a of the winding 11 to the other end 1b of the winding 11 and the direction from one end 2a of the winding 21 to the other end 2b of the winding 21 are opposite to each other in the toroidal direction of the magnetic core 10, at both ends (2a and 2b) of the winding 21, a negative voltage (-Vm) caused by the measurement magnetic flux φm and a positive voltage ΔVn caused by the residual magnetic flux are superimposed as common mode noise.

Then, in the differential circuit 30, by taking the difference between the voltage (Vm + ΔVn) generated in the winding 11 and the voltage (-Vm + ΔVn) generated in the winding 21, the voltage caused by the measured magnetic flux φm is amplified and the voltage ΔVn caused by the residual magnetic flux is cancelled.

Therefore, the differential circuit 30 outputs an output signal Vout from which the in-phase noise components caused by the residual magnetic flux of the parasitic magnetic fluxes φp1 and φp2 created by the toroidal current components Ip1 and Ip2 of the pair of windings 11 and 21 have been removed.

In addition, even if the number of turns of the pair of windings 11 and 21 is set to be the same, in reality, there will be differences (individual differences) in the detection sensitivity, parasitic capacitance, etc. between windings 11 and 21. The differential circuit 30 can also remove the in-phase components of noise that are directly caused by the differences in the detection sensitivity and parasitic capacitance of the windings 11 and 21 themselves. Therefore, the differential circuit 30 outputs an output signal Vout that removes not only the in-phase components of noise caused by the residual magnetic flux described above, but also the in-phase components of noise that are directly caused by individual differences in the detection sensitivity, parasitic capacitance, etc. of the windings themselves.

Next, the output error of the current sensor 100 will be explained with reference to FIG. 5.

Figure 5 shows the frequency characteristics versus the measured output error, with the vertical axis showing the amplitude gain error and the horizontal axis showing the frequency.

In the example shown in FIG. 5, the frequency characteristic of the gain error for the output signal Vout of the current sensor 100 is shown by a solid line, the frequency characteristic of the gain error at the output of winding 11 is shown by a dotted line, and the frequency characteristic of the gain error at the output of winding 21 is shown by a dashed line.

As shown in FIG. 5, in the frequency band higher than 40 MHz, the gain error in the output of winding 11 increases to the positive side, while the gain error in the output of winding 21 increases to the negative side. The reason for the increase in gain error is due to external magnetic flux such as magnetic fields and electromagnetic waves entering from the outside, and the residual parasitic magnetic flux mentioned above.

In addition, the pair of windings 11 and 21 are wound in opposite directions, and the gain error increases in the opposite directions, which indicates that the noise is dominated by common mode noise.

Therefore, in the first embodiment, common-mode noise is reduced by adopting a differential amplifier circuit as the differential circuit 30. Therefore, the current sensor 100 can suppress the influence of external magnetic flux, etc., on the output signal Vout that cannot be completely canceled by the pair of return lines 13 and 23.

Note that in Figure 5, the frequency characteristics of the gain error are shown as an example of the output error of the current sensor 100, but the frequency characteristics of the phase error in the current sensor 100 also suppress the increase in phase error in the high frequency band.

Next, the effects of the first embodiment will be explained.

In the first embodiment, the current sensor 100 includes a ring-shaped magnetic core 10, a pair of windings 11 and 21 consisting of a plurality of winding sections 11a to 11d and 21a to 21d connected in series, and a plurality of resistance elements 12 and 22 connected in parallel for each winding and for each winding section of the winding. The pair of windings 11 and 21 are wound in the poloidal direction along the toroidal direction on different parts of the magnetic core 10 and output a current flowing to the measurement object Lm. Of the pair of windings 11 and 21, the winding 11 constitutes a first winding and the winding 21 constitutes a second winding.

Furthermore, the current sensor 100 includes a pair of return wires 13 and 23 for each winding that return from one end of the winding to the other end along the toroidal direction of the portion of the magnetic core 10 around which the winding is wound. Specifically, the return wire 13 is a first return wire having one end connected to one end 1a of the winding 11 as the first winding, and the other end 1c extending from one end 1a of the winding 11 to the vicinity of the position of the other end 1b of the winding 11 along the toroidal direction of the first magnetic core portion 10a around which the winding 11 is wound in the magnetic core 10. The return wire 23 is a second return wire having one end connected to one end 2a of the winding 21 as the second winding, and the other end 2c extending from one end 2a of the winding 21 to the vicinity of the position of the other end 2b of the winding 21 along the toroidal direction of the second magnetic core portion 10b around which the winding 21 is wound in the magnetic core 10.

Then, the current sensor 100 outputs a signal indicating the difference between the output of the winding 11 and the return wire 13 as the first winding and the first return wire, and the output of the winding 21 and the return wire 23 as the second winding and the second return wire.

According to this configuration, as shown in FIG. 2, in the current sensor 100 of the first embodiment, a pair of windings 11 and 21 are wound around the first magnetic core portion 10a and the second magnetic core portion 10b of the magnetic core 10, respectively, so that an increase in the parasitic capacitance of each of the windings 11 and 21 is suppressed. This suppresses the deterioration of flatness in the frequency characteristics of the amplitude and phase of each of the windings 11 and 21 due to an increase in parasitic capacitance.

In addition, the current sensor 100 has multiple resistance elements 12 and 22 connected in parallel to each of the winding sections of the pair of windings 11 and 21, so that multiple circuits consisting of each winding section and its parasitic capacitance are formed in series.

The inductance of the winding portion in the above circuit and the capacitance of the parasitic capacitance are both smaller than the inductance of the entire windings 11 and 21 and the capacitance of the parasitic capacitance. Therefore, the resonant frequency determined by the pair of windings 11 and 21 and their parasitic capacitance is sufficiently higher than the resonant frequency of a winding that does not have a series resistor element. Therefore, the flatness of the frequency characteristics of the current sensor 100 with respect to the amplitude and phase is improved in the high frequency band.

The inductance of windings 11a to 11d and windings 21a to 21d are set to be equal, and the resistance values of resistor elements 12 and 22 are set to be equal. This linearly symmetrical structure prevents the measurement accuracy from decreasing due to the misalignment of the conductor of the measurement object Lm inserted into the annular magnetic core 10.

In addition, the current sensor 100 outputs a signal indicating the difference between the magnetism from the winding 11 and the return wire 13 and the magnetism from the winding 21 and the return wire 23. In the first embodiment, the output signal Vout of the current sensor 100 includes a signal indicating the difference between the magnetism generated in the winding 11 and the return wire 13 and the magnetism generated in the winding 21 and the return wire 23.

Specifically, for the current sensor 100, the pair of windings 11 and 21 are wound such that the direction from one end of the winding 11 to the other end of the winding 11 and the direction from one end of the winding 21 to the other end of the winding 21 are opposite to each other in the toroidal direction of the magnetic core 10, and the pair of windings 11 and 12 are wound in opposite directions to each other in the poloidal direction of the magnetic core 10.

At the same time, the return wire 13, one end 1a of which is connected to one end 1a of the winding 11, is extended along the circumference (toroidal direction) of the magnetic core 10, with the other end 1b of the return wire 13 being extended to the vicinity of the position of the other end 1b of the winding 11, and the return wire 23, one end of which is connected to one end 2a of the winding 21, is extended along the circumference (toroidal direction) of the magnetic core 10 in the opposite direction to the return wire 13, with the other end 2c of the return wire 23 being extended to the vicinity of the position of the other end 2b of the winding 21. Then, the other end 2c of the return wire 23 is connected to the other end 1b of the winding 11.

With this configuration, the current flowing in winding 11, which constitutes part of the one-turn loop due to external magnetic flux, etc., flows to winding 21, which constitutes the other part (remainder) of the one-turn loop, generating a magnetic flux in the opposite direction to the external magnetic flux, etc., canceling out at least a part of the in-phase component of the external magnetic flux, etc. Furthermore, the current flowing in return wire 13, which constitutes part of the one-turn loop due to external magnetic flux, etc., flows to return wire 23, which constitutes the other part of the one-turn loop, generating a magnetic flux in the opposite direction to the external magnetic flux, etc., canceling out at least a part of the in-phase component of the external magnetic flux, etc.

As a result, when detecting the measurement current Im, the current sensor 100 can reduce noise caused by external magnetic flux, etc., thereby improving the current detection accuracy.

In addition, in the current sensor 100, the pair of return wires 13 and 23 extend in opposite directions along the toroidal direction of the magnetic core 10. That is, the pair of return wires 13 and 23 are wired so that one ends 1a and 2a of the pair of return wires 13 and 23 are adjacent to each other.

With this configuration, the other ends 1c and 2c of the pair of return lines 13 and 23 tend to be close to each other, shortening the wiring of the pair of return lines 13 and 23 to the differential circuit 30 and making it easier to design the wiring layout.

In addition, the current sensor 100 has the same number of turns of winding 11 as the number of turns of winding 21.

With this configuration, the external magnetic flux etc. detected by winding 11 and winding 21 are equivalent, so noise caused by external magnetic flux etc. can be further reduced.

In addition, the current sensor 100 is designed so that the circumferential length of the magnetic core 10 at the portion around which the winding 11 is wound is equal to the circumferential length of the magnetic core 10 at the portion around which the winding 21 is wound.

With this configuration, the length of return line 13 and the length of return line 23 are the same, so the external magnetic flux etc. detected by return line 13 and return line 23 are the same, which further reduces noise caused by external magnetic flux etc.

In addition, the current sensor 100 has a pair of windings 11 and 21 arranged on the magnetic core 10 so that the ends 1a and 2a of the pair of windings 11 and 21, which form the ends 1a and 2a of the pair of return wires 13 and 23, are adjacent to each other.

With this configuration, the other ends 1b and 2b of the pair of windings 11 and 21 are adjacent to each other, so the distance between the other ends 1c and 2c of the pair of return wires 13 and 23 that extend toward the other ends 1b and 2b of the pair of windings is also close.

This makes it possible to shorten the distance over which the pair of return lines 13 and 23 are routed to the pair of input terminals of the differential circuit 30. This makes it possible to suppress the introduction of noise into the routing lines associated with the routing of the pair of return lines 13 and 23.

The current sensor 100 also includes a differential circuit 30 that outputs an output signal Vout that includes the difference between the electrical signals output from the pair of windings 11 and 21 through the pair of return wires 13 and 23, respectively.

That is, the current sensor 100 includes a differential circuit 30 that outputs a signal indicating the difference between the electrical signals from both the winding 11 and the return wire 13 and the winding 21 and the return wire 23, and the output of the differential circuit 30 indicates the difference between the outputs from both. In this way, the current sensor 100 outputs a signal indicating the difference between the electrical signal from the winding 11 and the return wire 13 and the electrical signal from the winding 21 and the return wire 23.

Specifically, in the current sensor 100, a pair of windings 11 and 21 are wound in opposite directions in the toroidal direction of the magnetic core 10. The other end 1c of the return wire 13 extending from one end 1a of the winding 11 included in the pair of windings is connected to an inverting input terminal (-) serving as a first input terminal of the differential circuit 30, and the other end 2b of the winding 21 is connected to a non-inverting input terminal (+) serving as a second input terminal of the differential circuit 30. The other end 2c of the return wire 23 extending from one end 2a of the winding 21 and the other end 1b of the winding 11 are each connected to a reference potential G.

With this configuration, the pair of return wires 13 and 23 cancels external magnetic flux, etc., while the differential circuit 30 removes the in-phase components of noise caused by the external magnetic flux, etc., that cannot be canceled. Specifically, due to differential amplification in the differential circuit 30, the level of the signal proportional to the measurement current Im among the output signals of the pair of windings 11 and 21 increases, and the noise voltage level decreases. As a result, the current detection accuracy of the current sensor 100 can be improved.

In this way, in the current sensor 100, the outputs of both are input to the differential circuit 30 to obtain the difference between the magnetism generated in the winding 11 and return wire 13 as the first winding and first return wire, and the magnetism generated in the winding 21 and return wire 23 as the second winding and second return wire. The differential circuit 30 then generates an output signal Vout that includes the difference between the magnetic fields generated in both windings as well as the difference between the electrical signals from both windings.

Therefore, the output signal Vout of the current sensor 100 contains the magnetic difference occurring in the pair of configurations including the return wires 13 and 23 arranged to cancel external magnetic flux, etc., and the difference in the electrical signal output from the pair of configurations obtained by the differential circuit 30 provided to remove the in-phase components of noise caused by external magnetic flux, etc. that cannot be canceled by the pair of return wires 13 and 23. In other words, the difference between the output of the first winding and first return wire and the output of the second winding and second return wire contains the magnetic difference and the electrical signal difference.

Therefore, with the above configuration, the external magnetic flux etc. generated by the pair of windings 11 and 21 can be cancelled by the pair of return wires 13 and 23, and the in-phase components of noise caused by the external magnetic flux etc. that cannot be cancelled can be suppressed by the differential circuit 30. Therefore, the current detection accuracy of the current sensor 100 can be improved.

In addition, the current sensor 100 has multiple resistive elements 12 and 22 each having the same resistance value.

With this configuration, the windings connected in parallel for each resistive element 12 and the windings connected in parallel for each resistive element 22 each have the same detection sensitivity. This makes it possible to suppress fluctuations in detection accuracy due to the positional relationship of the measurement target Lm inserted into the magnetic core 10.

Therefore, it is possible to suppress a decrease in detection accuracy caused by a positional shift of the measurement object Lm relative to the magnetic core 10 while raising the upper limit of the detectable frequency band.

The measurement device 1 of the first embodiment also includes the above-mentioned current sensor 100 and a measurement unit 200 that calculates a measurement amount for the measurement object Lm based on the amount detected by the current sensor.

With this configuration, the measurement quantity of the measurement object Lm is calculated based on the output signal of the current sensor 100, so the upper limit of the measurable frequency band can be made higher than in a general measurement device equipped with a current sensor that does not have a pair of return lines 13 and 23 and a differential circuit 30. Therefore, the measurement object Lm can be measured with high accuracy in a higher frequency band.

Second Embodiment
6 is a diagram showing a configuration of a current sensor 101 according to a second embodiment. In the second embodiment, it is assumed that the difference circuit 30 and other components such as the pair of windings 11 and 21 are spaced apart from each other.

In addition to the configuration of the current sensor 100 of the first embodiment, the current sensor 101 includes a pair of transmission lines 14 and 24 and a pair of resistive elements 15 and 25. Here, the configuration of the current sensor 101 of the second embodiment that is the same as or equivalent to the current sensor 100 shown in FIG. 2 is given the same reference numerals as those given to the configuration of the current sensor 100, and duplicated explanations are omitted.

The pair of transmission paths 14 and 24 are transmission paths for transmitting the output signals of the pair of windings 11 and 21 to the differential circuit 30. The pair of transmission paths 14 and 24 are, for example, coaxial transmission paths, and as a specific example, are realized by a coaxial cable with a characteristic impedance of 50 [Ω] or 75 [Ω].

Each transmission line 14 and 24 is composed of an inner conductor, an outer conductor, and an insulator disposed between them.

In the transmission line 14, the input end of the internal conductor is connected to the other end 1c of the return line 13, and the input end of the external conductor is connected to the reference potential G and the other end 1b of the winding 11. In the transmission line 24, the input end of the internal conductor is connected to the other end 2b of the winding 21, and the input end of the external conductor is connected to the reference potential G and the other end 2c of the return line 23.

The pair of resistor elements 15 and 25 has the function of performing impedance matching with a termination resistance equivalent to the characteristic impedance of the pair of transmission lines 14 and 24. The pair of resistor elements 15 and 25 connects resistor elements of, for example, 50 [Ω] or 75 [Ω].

One end of the resistive element 15 is connected to the output end of the internal conductor of the transmission line 14 and the inverting input terminal (-) of the differential circuit 30. The other end of the resistive element 15 is connected to the reference potential G and the output end of the external conductor of the transmission line 14.

One end of the resistive element 25 is connected to the output end of the internal conductor of the transmission line 24 and the non-inverting input terminal (+) of the differential circuit 30. The other end of the resistive element 25 is connected to the reference potential G and the output end of the external conductor of the transmission line 24.

In such a configuration, the sum of the resistance values of the four resistive elements 12 connected in parallel to the winding 11 is set to be equal to the characteristic impedance of the transmission line 14. Similarly, the sum of the resistance values of the four resistive elements 22 connected in parallel to the winding 21 is set to be equal to the characteristic impedance of the transmission line 14.

Next, the effects of the second embodiment will be explained.

The current sensor 101 of the second embodiment has a configuration equivalent to that of the current sensor 100 of the first embodiment, and can achieve the same effects as those of the first embodiment.

In addition, the current sensor 101 includes transmission paths 14 and 24 for transmitting the output signals of the windings 11 and 21 to the differential circuit 30 as a pair of transmission paths for transmitting the output of the winding 11 and the return line 13 and the output of the winding 21 and the return line 23 to the differential circuit 30, respectively. The sum of the resistance values of the series resistance elements 12 or 22 connected in parallel to at least one of the windings 11 or 21 is approximately the same as the characteristic impedance of the transmission path 14 or 24 corresponding to at least one of the windings 11 or 21.

With this configuration, the characteristic impedance of the transmission line 14 or 24 is equivalent to the sum of the resistance values of the series resistor elements 12 or 22, so that the output signal of the winding 11 or 21 can be prevented from being reflected at one end of the transmission line 14 or 24. This makes it possible to reduce detection errors caused by reflections on the transmission line 14 or 24.

In the second embodiment, an example in which the differential circuit 30 is disposed in the current sensor 101 has been described, but the differential circuit 30 may be disposed in the measurement unit 200 shown in FIG. 1. In this case, the cable 110 shown in FIG. 1 is provided with a pair of transmission paths 14 and 24 shown in FIG. 6.

Third Embodiment
FIG. 7 is a diagram showing a configuration of a current sensor 102 according to the third embodiment.

The current sensor 102 of the third embodiment includes an impedance adjustment circuit 40 in addition to the configuration of the current sensor 101 of the second embodiment. Here, the configuration of the current sensor 102 of the third embodiment that is equivalent to that of the current sensor 101 shown in FIG. 6 is given the same reference numerals and redundant description is omitted.

The impedance adjustment circuit 40 adjusts the impedance seen from the input end of the transmission line 14 to the characteristic impedance of the transmission line 14. Furthermore, the impedance adjustment circuit 40 adjusts the impedance seen from the input end of the transmission line 24 to the characteristic impedance of the transmission line 24. In this way, the impedance adjustment circuit 40 adjusts the impedance seen from at least one input end of the pair of transmission lines 14 and 24 to the characteristic impedance of at least one of the transmission lines.

Next, the effects of the third embodiment will be explained.

The current sensor 102 of the third embodiment has a configuration equivalent to that of the current sensor 101 of the second embodiment, and can achieve the same effects as those of the second embodiment.

In addition, in the second embodiment, the current sensor 102 includes an impedance adjustment circuit 40 that adjusts the impedance seen from the input end of the transmission line 14 or 24 to the characteristic impedance of the transmission line 14 or 24. The transmission line 14 or 24 constitutes a pair of transmission lines for transmitting the output of the winding 11 and the return line 13 and the output of the winding 21 and the return line 23 to the differential circuit 30, respectively.

With this configuration, the current sensor 102 can adjust the impedance seen from the input end of the transmission line 14 or 24 and the characteristic impedance of the transmission line 14 or 24 to be equal in the impedance adjustment circuit 40.

Therefore, even if the sum of the resistance values of the series resistor elements 12 or 22 connected in parallel to the winding 11 or 21 is not equal to the characteristic impedance of the transmission line 14 or 24, it is possible to suppress the output signal of the winding 11 or 21 from being reflected at one end of the transmission line 14 or 24. This makes it possible to reduce detection errors caused by reflections at the transmission line 14 or 24.

(Fourth embodiment)
Next, a current sensor according to a fourth embodiment will be described with reference to FIGS.

Figure 8 is a diagram showing the configuration of a current sensor 103 according to the fourth embodiment. Figure 9 is a circuit diagram showing an example of an equivalent circuit of the current sensor 103 shown in Figure 8.

As shown in FIG. 8, the current sensor 103 has a pair of windings 111 and 112 and a differential circuit 30A, instead of the pair of windings 11 and 21 and the differential circuit 30 constituting the current sensor 100 of the first embodiment. The other configurations are the same as those of the current sensor 100 shown in FIG. 2, so the same reference numerals are used and duplicated explanations are omitted.

The pair of windings 111 and 112 are wound in the same direction in the toroidal direction of the magnetic core 10. The other ends 1b and 2b of the pair of windings 111 and 112 are connected to a reference potential G, respectively.

One end 1a of the winding 111 is one end of the return wire 13, and one end 2a of the winding 112 is one end of the return wire 23. The other end 1b of the winding 111 is connected to the other end 2b of the winding 112. The other ends 1c and 2c of the pair of return wires 13 and 23 are connected to the inverting input terminal (-) and non-inverting input terminal (+) of the differential circuit 30A, respectively.

As shown in FIG. 9, the winding 111 is divided into winding sections 111a to 111d, which correspond to the winding sections 111a to 111d shown in FIG. 3. For each of the winding sections 111a to 111d, a resistive element 12 is connected in parallel, and each resistive element 12 is connected in series.

The winding 112 is divided into winding sections 112a to 112d, which correspond to the winding sections 112a to 112d shown in FIG. 3. For each of the winding sections 112a to 112d, the resistive elements 22 are connected in parallel and in series.

Differential circuit 30A corresponds to differential circuit 30 shown in FIG. 2. Differential circuit 30A generates and outputs an output signal Vout that is proportional to the magnitude of the difference between the electrical signals output from the pair of windings 111 and 112 through the pair of return lines 13 and 23, respectively.

Next, we will explain the effects of the fourth embodiment.

In the current sensor 103 of the fourth embodiment, the pair of windings 111 and 112 are wound in the same direction in the toroidal direction of the magnetic core 10. The windings 111 and 112 are also wound in the same poloidal direction. The other ends 1c and 2c of the pair of return wires 13 and 23 are respectively connected to the inverting input terminal (-) as the first input terminal of the differential circuit 30A and the non-inverting input terminal (+) as the second input terminal. The other ends 1b and 2b of the pair of windings 111 and 112 are respectively connected to the reference potential G.

That is, the current sensor 103 includes a pair of windings 111 and 112 that detect the measurement current Im, and a plurality of resistance elements 12 and 22 that are connected in parallel to a plurality of portions of each winding. The pair of windings 111 and 112 are wound in a toroidal direction on different portions of the magnetic core 10. The plurality of resistance elements 12 are connected in series, and similarly, the plurality of resistance elements 22 are also connected in series.

The current sensor 103 further includes a differential circuit 30A that outputs an output signal Vout as a signal indicating the difference between the electrical signals output from the winding 111 and the return wire 13 and the winding 112 and the return wire 13. The pair of return wires 13 and 23 return from one end 1a and 2a of the windings 111 and 112 to the other end 1b and 2b along the toroidal direction of the portion of the magnetic core 10 where the windings 111 and 112 are wound.

The current sensor 103 differs from the first embodiment in that the pair of windings 111 and 112 are wound in the same poloidal direction, and a signal indicating the difference between the current passing through the return line 13 and the current passing through the return line 23 is output by the differential circuit 30A.

With this configuration, the current sensor 103 cancels at least a portion of the in-phase noise components of the noise due to external magnetic flux etc. output through the winding 111 and the return wire 13 by using the noise due to external magnetic flux etc. output through the winding 111 and the return wire 23. In addition, the current sensor 103 cancels at least a portion of the negative-phase components of the external magnetic flux etc. due to the winding 112 which constitutes the other part (remainder) of the one-turn loop by the winding 111 which constitutes part of the one-turn loop, and cancels at least a portion of the negative-phase components of the external magnetic flux etc. due to the return wire 23 which constitutes the other part of the one-turn loop by the return wire 13 which constitutes part of the one-turn loop.

As a result, when detecting the measurement current Im, the current sensor 103 can reduce noise caused by external magnetic flux, etc., thereby improving the current detection accuracy.

In addition, since the pair of windings 111 and 112 are wound in the same direction, the pair of windings 111 and 112 can be constructed more simply than the pair of windings 11 and 21 of the first embodiment. In addition, wiring from the pair of return wires 13 and 23 to the differential circuit 30A is simplified.

Fifth Embodiment
FIG. 10 is a diagram showing a configuration of a current sensor 104 according to the fifth embodiment.

The current sensor 104 is a current sensor that employs a zero-flux method, and is capable of detecting currents in the low-frequency band, which is lower than the high-frequency band and includes direct current, in addition to currents in the high-frequency band.

In addition to the configuration of the current sensor 100 of the first embodiment, the current sensor 104 includes a magnetic detection element 50, a pair of feedback circuits 51 and 52, and capacitance elements 60 to 67 between each of the windings and the resistance elements 12 and 22, which are connected in parallel. For convenience, the additional configuration is conceptually shown in FIG. 10 so that the connection relationship can be easily understood. The other configuration is the same as the configuration of the current sensor 100 shown in FIG. 2, so the same reference numerals are used and duplicated explanations are omitted.

The magnetic detection element 50 is attached to the magnetic core 10 and detects the magnetic flux generated within the magnetic core 10. The magnetic detection element 50 is realized, for example, by a flux gate built into the magnetic core 10, a Hall element inserted into a gap provided in the magnetic core 10, or a detection winding wound around the magnetic core 10.

The magnetic detection element 50 of the fifth embodiment is a fluxgate formed in the gap of the magnetic core 10. The magnetic detection element 50 outputs a detection signal whose amplitude is proportional to the magnitude of the detected magnetic flux to a pair of feedback circuits 51 and 52.

The pair of feedback circuits 51 and 52 constitute a supply circuit that supplies a signal to the pair of windings 11 and 21 to excite the magnetic core 10 so as to cancel out the magnetic flux detected by the magnetic detection element 50.

The feedback circuit 51 amplifies the output signal output from the magnetic detection element 50 and supplies the amplified output signal to the other end 1b of the winding 11. That is, the feedback circuit 51 supplies a signal to the other end 1b of the winding 11 for exciting the first magnetic core portion 10a of the magnetic core 10 so as to cancel the measurement magnetic flux created by the measurement current Im.

As a result, in the low frequency band, a magnetic flux in the opposite direction to the measurement magnetic flux created by the measurement current Im is generated in the first magnetic core portion 10a of the magnetic core 10 wound around the winding 11. Therefore, in the low frequency band, the first magnetic core portion 10a of the magnetic core 10 is in a zero flux state.

The feedback circuit 52 inverts the phase of the detection signal output from the magnetic detection element 50, amplifies it, and supplies the inverted and amplified output signal to one end 2a of the winding 21. That is, the feedback circuit 52 supplies a signal to one end 2a of the winding 21 for exciting the second magnetic core portion 10b of the magnetic core 10 so as to cancel the measurement magnetic flux created by the measurement current Im.

As a result, in the second magnetic core portion 10b of the magnetic core 10 wound around the winding 21, a magnetic flux is generated in the opposite direction to the measurement magnetic flux generated by the measurement current Im. Therefore, in the low frequency band, the second magnetic core portion 10b of the magnetic core 10 is in a zero flux state.

The multiple capacitive elements 60 to 67 are passive elements that block signal components from DC to the low frequency band.

The capacitance element 60 connects one end 1d of the multiple resistance elements 12 connected in series to the other end 1b of the winding 11, which is composed of multiple winding sections, and the capacitance elements 61 to 63 each connect between a connection point between adjacent resistance elements of the multiple resistance elements 12 and a division point between the corresponding winding sections of the winding 11. The division point corresponds to a connection point to which one end of the capacitance element is connected.

Capacitive element 64 connects one end 2d of the multiple resistive elements 22 connected in series to one end 2a of the winding 21 composed of multiple winding sections, and capacitive elements 65 to 67 each connect between the connection points between adjacent resistive elements of the multiple resistive elements 22 and the division points between the corresponding winding sections of the winding 21.

That is, the connection points between adjacent resistance elements among the multiple resistance elements 12 and the winding portion of the winding 11, and the connection points between adjacent resistance elements among the multiple resistance elements 12 and the connection points between adjacent winding portions of the winding 21 are connected via capacitance elements 61 to 63 and 65 to 67, respectively. Furthermore, the output terminals of the feedback circuits 51 and 52 that constitute the supply circuit are connected to the connection terminals (1b and 2a) of the resistance elements to which the outputs are connected, respectively, via capacitance elements 60 and 64.

In this way, the multiple capacitance elements 60 to 67 are connected between the connection points between adjacent resistance elements among the multiple resistance elements 12 and the connection points between adjacent winding portions of the windings 11 and 21, and between each output end of the supply circuit and the connection ends (1b and 2a) of the resistance elements connected to each output end.

The capacitance elements 60 to 67 prevent a portion of the DC signal output from the feedback circuits 51 and 52 to the windings 11 and 12 from returning to the reference potential G through the resistance elements 12 and 22.

In this way, by adding a magnetic detection element 50 and a pair of feedback circuits 51 and 52, the current sensor 104 is able to detect current in the low frequency band using the zero flux method.

In the fifth embodiment, an example is described in which a magnetic detection element 50 is added to the configuration of the current sensor 100 shown in FIG. 2 in order to perform current detection using the zero flux method, but this is not limiting, and a magnetic detection element 50 may be added to the configuration of the current sensor 103 shown in FIG. 8.

In this case, instead of the pair of feedback circuits 51 and 52, a supply circuit is added that supplies a signal to the other ends 1b and 2b of the pair of windings 111 and 112 shown in FIG. 8 to excite a magnetic flux in the opposite direction to the measured magnetic flux based on the detection signal of the magnetic detection element 50.

Next, we will explain the effects of the fifth embodiment.

The current sensor 104 of the fifth embodiment has a configuration equivalent to that of the current sensor 101 of the first embodiment, and can obtain the same effect as the first embodiment. That is, the current sensor 104 can increase the upper limit of the high frequency band in which the current can be detected.

In addition, the current sensor 104 includes a magnetic detection element 50 that detects the magnetic flux generated in the magnetic core 10. The current sensor 104 further includes a pair of feedback circuits 51 and 52 that serve as a supply circuit that supplies a signal to the pair of windings 11 and 21 to excite the magnetic core 10 so as to cancel out the magnetic flux detected by the magnetic detection element 50.

This configuration enables current detection using the zero flux method, so the lower limit of the low frequency band can be lowered to DC. Therefore, the lower limit of the low frequency band in which the current sensor 104 can detect current can be lowered, while the upper limit of the high frequency band can be raised.

Sixth Embodiment
FIG. 11 is a diagram showing a configuration of a current sensor 105 according to the sixth embodiment.

The current sensor 105 has a configuration in which the differential circuit 30 has been removed from the configuration of the current sensor 100 of the first embodiment shown in FIG. 2. The same components as those of the current sensor 100 shown in FIG. 2 are given the same reference numerals and redundant explanations are omitted.

In the sixth embodiment, the pair of windings 11 and 21 are wound so that the direction from one end 1a to the other end 1b of the winding 11 and the direction from one end 2a to the other end 2b of the winding 21 are opposite to each other in the toroidal direction of the magnetic core 10, and are also opposite to each other in the poloidal direction of the magnetic core 10. The other end 2c of the return wire 23 is connected to the other end 1b of the winding 11 without being connected to the reference potential G, and the other end 2b of the winding 21 is connected to the reference potential G.

Therefore, the signal output from the other end 1c of the return wire 13 is a signal indicating the difference between the magnetism generated in the winding 11 and the return wire 13 and the magnetism generated in the winding 21 and the return wire 23, and is output to the measurement unit 200 as the output signal Vout of the current sensor 105.

Therefore, the current sensor 105 of the sixth embodiment has the same effect as the first embodiment, except for the effect of the arrangement of the differential circuit 30 in the first embodiment. In particular, the current sensor 105 of the sixth embodiment has a configuration in which the other end 2c of the return wire 23 is connected to the other end 1b of the winding 11, and outputs an output signal Vout indicating the difference between the magnetism generated in the winding 11 and the return wire 13 and the magnetism generated in the winding 21 and the return wire 23 as the difference between the output of the winding 11 and the return wire 13 and the output of the winding 21 and the return wire 23. With this configuration, the current sensor 105 can raise the upper limit of the high frequency band in which current can be detected.

Although the embodiments of the present invention have been described above, the above embodiments merely show some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

In the above embodiment, the pair of wirings (11 and 13, 21 and 23) consisting of the pair of windings 11 and 21 and the pair of return wires 13 and 23 are both configured to be linearly symmetrical in the radial direction of the magnetic core 10, but they may also be configured to cancel out both parasitic magnetic fluxes. In other words, the pair of windings and the pair of return wires may be configured to be substantially linearly symmetrical.

In the above embodiment, an example was described in which the entire toroidal portion of the magnetic core 10 is wound with the windings 11 and 21, but this is not limited thereto, and the windings 11 and 21 may be wound around a portion of the toroidal portion of the magnetic core 10. Also, in addition to the windings 11 and 21, one or more other pairs of windings that function in a similar manner may be wound around the magnetic core 10 in the toroidal direction.

For example, in the above embodiment, an example was described in which two semicircular windings are wound around the magnetic core 10 so as to face each other, but this is not limited thereto, and a pair of windings may be wound so as to bisect the semicircular portion of the magnetic core 10.

In the above embodiment, a configuration is adopted in which the pair of return wires 13 and 23 extend in opposite directions along the toroidal direction of the magnetic core 10. Alternatively, a configuration may be adopted in which the pair of return wires 13 and 23 extend in the same direction along the toroidal direction of the magnetic core 10. Even with such a configuration, the same effect as the above embodiment can be obtained.

1 Measuring device 1a, 2a One end of winding, one end of return wire 1b, 2b Other end of winding 1c, 2c Other end of return wire 10 Magnetic core 10a, 10b First magnetic core portion, second magnetic core portion (different parts from each other)
11, 21, 111, 112 Windings (first winding, second winding, pair of windings)
12, 22 Resistance element 13, 23 Return line 14, 24 Transmission line 15, 25 Resistance element 30, 30A Differential circuit 40 Impedance adjustment circuit 50 Magnetic detection element 51, 52 Feedback circuit (supply circuit)
60 to 67 Capacitive element 100 to 104 Current sensor 200 Measurement unit Lm Measurement object Im Measurement current

Claims (15)

An annular magnetic core;
A pair of windings including a first winding and a second winding, each of which is composed of a plurality of winding parts connected in series and wound in a poloidal direction along a toroidal direction on different parts of the magnetic core, for detecting a current flowing through a measurement object;
A plurality of resistance elements connected in parallel to each of the winding portions;
a first return wire having one end connected to one end of the first winding and the other end extending from the one end of the first winding to a position near the other end of the first winding along a toroidal direction of a portion of the magnetic core around which the first winding is wound;
a second return wire having one end connected to one end of the second winding and the other end extending from the one end of the second winding to a position near the other end of the second winding along a toroidal direction of a portion of the magnetic core around which the second winding is wound,
A current sensor that outputs a signal indicating a difference between an output of the first winding and the first return line and an output of the second winding and the second return line. 2. The current sensor according to claim 1,
The difference includes a magnetic difference.
Current sensor. 2. The current sensor according to claim 1,
a differential circuit that outputs a signal indicating the difference;
The difference includes a difference in an electrical signal.
Current sensor. 2. The current sensor according to claim 1,
a differential circuit that outputs a signal indicating the difference;
The difference includes a magnetic difference and an electrical signal difference.
Current sensor. 2. The current sensor according to claim 1,
The number of turns of the first winding and the number of turns of the second winding are equal to each other.
Current sensor. 2. The current sensor according to claim 1,
the different portions of the magnetic core are comprised of a first magnetic core portion and a second magnetic core portion,
The circumferential length of the first magnetic core portion and the circumferential length of the second magnetic core portion are equal to each other.
Current sensor. 2. The current sensor according to claim 1,
The other end of the first winding and the other end of the second winding are adjacent to each other.
Current sensor. 2. The current sensor according to claim 1,
The pair of windings are wound such that a direction from one end of the first winding to the other end of the first winding and a direction from one end of the second winding to the other end of the second winding are opposite to each other in the toroidal direction of the magnetic core, and are also opposite to each other in the poloidal direction of the magnetic core;
the other end of the second return wire is connected to the other end of the first winding;
Current sensor. 2. The current sensor according to claim 1,
a differential circuit that outputs a signal indicating the difference;
The pair of windings are wound such that a direction from one end of the first winding to the other end of the first winding and a direction from one end of the second winding to the other end of the second winding are opposite to each other in the toroidal direction of the magnetic core, and are wound in opposite directions to each other in the poloidal direction of the magnetic core,
the other end of the first return line is connected to a first input terminal of the differential circuit, and the other end of the second winding is connected to a second input terminal of the differential circuit;
The other end of the second return line and the other end of the first winding are each connected to a reference potential.
Current sensor. 2. The current sensor according to claim 1,
a differential circuit that outputs a signal indicating the difference;
The pair of windings are wound such that a direction from one end of the first winding to the other end of the first winding and a direction from one end of the second winding to the other end of the second winding are opposite to each other in the toroidal direction of the magnetic core, and are wound in the same direction to each other in the poloidal direction of the magnetic core,
the other end of the first return line and the other end of the second return line are respectively connected to a first input terminal and a second input terminal of the differential circuit;
The other end of the first winding and the other end of the second winding are each connected to a reference potential.
Current sensor. 2. The current sensor according to claim 1,
The resistance values of the plurality of resistive elements are equal to each other.
Current sensor. 2. The current sensor according to claim 1,
a differential circuit that outputs a signal indicating the difference;
a pair of transmission paths for transmitting the output of the first winding and the first return line and the output of the second winding and the second return line to the differential circuit,
a sum of resistance values of the plurality of resistive elements connected in parallel to at least one of the first winding and the second winding is approximately equal to a characteristic impedance of the transmission line;
Current sensor. 2. The current sensor according to claim 1,
a differential circuit that outputs a signal indicating the difference;
a pair of transmission paths for transmitting the outputs of the first winding and the first return line and the outputs of the second winding and the second return line to the differential circuit, respectively;
an impedance adjustment circuit that adjusts an impedance seen from an input end of at least one of the pair of transmission lines to a characteristic impedance of the transmission line;
2. A current sensor including: 2. The current sensor according to claim 1,
a magnetic detection element for detecting a magnetic flux generated in the magnetic core;
a supply circuit that supplies a signal to the pair of windings for exciting the magnetic core so as to cancel out the magnetic flux based on the magnetic flux detected by the magnetic detection element;
A plurality of capacitance elements that block signal components ranging from direct current to low frequency bands;
Including,
the plurality of capacitance elements are connected between a connection point between adjacent resistance elements among the plurality of resistance elements and a connection point between adjacent winding portions, and between each output end of the supply circuit and the resistance element connected to each output end,
Current sensor. A current sensor according to any one of claims 1 to 14;
a measurement unit that calculates a measurement amount for the measurement object based on the amount detected by the current sensor;
A measuring device comprising:

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