JP2011112634A - Ring core for flux gate leakage sensor, ring core unit including the ring core, and the flux gate leakage sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ring core for a flux gate leakage sensor easily saturated with flux density and having a small inductance; to provide a ring core unit including the ring core and having excellent productivity; and to provide the flux gate leakage sensor which is suitable for heightening of a sampling frequency and power saving. <P>SOLUTION: This ring core (16) is applied to the flux gate leakage sensor into which a first wire and a second wire which are measuring objects are inserted. The ring core (16) includes a low resistance part (16a) and a high resistance part (16b) connected mutually in the own circumferential direction, and having each different magnitude of the magnetic resistance per unit length in the circumferential direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ring core for a fluxgate leakage sensor for detecting leakage, a ring core unit including the ring core, and a fluxgate leakage sensor.

  As a device for detecting leakage of current supplied from a power supply to a load, Patent Literature 1 discloses a DC leakage detection device. This device includes an annular core, and a first detected conductor and a second detected conductor are inserted through the core, and a coil is wound around the core.

A high-frequency current flows from the high-frequency output circuit to the coil, and the AC voltage across the coil is converted into a DC voltage by the rectifier circuit. Then, the DC voltage is compared with the reference voltage in the comparison circuit, and it is determined that a leakage has occurred when the DC voltage is smaller than the reference voltage.
In other words, this device detects the leakage by utilizing the fact that the magnetic flux density of the core is saturated and the impedance of the coil is lowered when the leakage occurs.

  On the other hand, in the specification attached to the application of the patent application (Japanese Patent Application No. 2009-162739) by the applicant of the present application, a fluxgate leakage sensor is described. In this flux gate leakage sensor, the drive circuit applies a voltage to the coil with a positive and negative symmetrical rectangular wave so as to saturate the magnetic flux density of the coil while reversing the direction.

JP 2000-2738 A

  In the DC leakage detection device disclosed in Patent Document 1 and the flux gate leakage sensor described in the specification of Japanese Patent Application No. 2009-162739, if the magnetic flux density of the core can be saturated with a smaller current, it can be saved. Electricity is achieved. In the latter case, the frequency of the voltage applied to the coil (sampling frequency) can be increased to improve the detection accuracy of the leakage current.

The present invention has been made based on the above-described circumstances, and one of its purposes is to provide a ring core for a fluxgate leakage sensor that has a small inductance and is likely to be saturated with a magnetic flux density.
Another object of the present invention is to provide a ring core unit having the ring core and excellent in productivity.
Another object of the present invention is to provide a fluxgate leakage sensor that includes the ring core and is suitable for increasing the sampling frequency and saving power.

  In order to solve the above problem, according to one aspect of the present invention, in a ring core for a fluxgate leakage sensor through which a first electric wire and a second electric wire to be measured are inserted, in the circumferential direction of the ring core A ring core for a fluxgate leakage sensor is provided, which includes a low resistance portion and a high resistance portion, which are connected to each other and have different magnitudes of magnetoresistance per unit length in the circumferential direction. Item 1).

According to the ring core of claim 1, in addition to the low resistance portion having a small magnetic resistance, the high resistance portion having a large magnetic resistance is provided, so that the inductance becomes smaller and smaller than the case of only the low resistance portion. The magnetic flux density is saturated by the current.
According to the fluxgate leakage sensor using this ring core, the magnetic flux density of the ring core is saturated with a small current, so that power saving can be achieved and the sampling frequency can be increased.

Preferably, the high resistance portion is made of a material having a lower magnetic permeability than the low resistance portion.
According to the ring core of the second aspect, by using a material having a low magnetic permeability for the high resistance portion, the magnetic flux density of the ring core is surely saturated with a small current as compared with a case where the material is made only of a material having a high magnetic permeability.

Preferably, the high resistance portion is made of ferrite, and the low resistance portion is made of permalloy.
By using ferrite and permalloy, the ring core of claim 3 is easily available and can be provided at low cost.

Preferably, the high resistance portion has a smaller cross-sectional area than the low resistance portion.
According to the ring core of claim 4, since the high resistance portion has a smaller cross-sectional area than the low resistance portion, the magnetic flux density of the ring core is reliably saturated with a small current with a simple configuration.

According to another aspect of the present invention, there is provided a ring core unit for a fluxgate leakage sensor comprising a bobbin penetrated by the low resistance portion and a coil wound around the bobbin ( Claim 5).
The ring core unit of claim 5 is easily assembled by attaching the bobbin around which the coil is wound to the low resistance portion.

According to still another aspect of the present invention, there is provided a fluxgate leakage sensor comprising the ring core for a fluxgate leakage sensor according to any one of claims 1 to 4. ).
According to the fluxgate leakage sensor of the sixth aspect, the magnetic flux density of the ring core is saturated with a small current, so that power saving can be achieved and the sampling frequency can be increased.

  Preferably, the fluxgate leakage sensor includes a coil wound around the ring core and a drive circuit that applies a voltage to the coil with a positive and negative symmetrical rectangular wave so as to saturate the magnetic flux density of the coil while reversing the direction. And a measured voltage that changes in response to the coil current flowing through the coil is compared with a positive and negative symmetrical reference voltage and a positive reference voltage, and the measured voltage corresponds to a positive period corresponding to a period higher than the positive reference voltage. A comparator circuit that outputs a negative side electric signal and a negative side electric signal corresponding to a period in which the measurement voltage is lower than the negative side reference voltage, and the positive side electric signal and the negative side electric signal output from the comparator circuit And a determination circuit that compares the signal (claim 7).

  According to the fluxgate leakage sensor of claim 7, the current flowing through the first electric wire and the first current based on the period in which the measured voltage is higher than the positive reference voltage and the period in which the measured voltage is lower than the negative reference voltage. The magnitude relationship between the current flowing through the two electric wires is determined. That is, leakage is detected based on a period in which the measured voltage is higher than the positive reference voltage and a period in which the measured voltage is lower than the negative reference voltage.

According to this flux gate leakage sensor, the frequency of the voltage applied to the coil by the drive circuit, that is, the sampling frequency can be increased by utilizing the saturation of the magnetic flux density of the ring core with a small current.
On the other hand, if the sampling frequency is not changed, the time required for the magnetic flux density of the ring core to saturate is shortened, and the measured voltage is higher than the positive reference voltage. Each low period becomes longer. In this case, the measurement error during these periods is reduced, and leakage is detected with high accuracy.

  Preferably, the comparator circuit includes a positive comparator having a non-inverting input terminal to which the measurement voltage is applied and an inverting input terminal to which the positive reference voltage is input, an inverting input terminal to which the measurement voltage is applied, and A negative comparator having a non-inverting input terminal to which the negative reference voltage is inputted, a positive field effect transistor having a gate electrode to which an output voltage of the positive comparator is inputted, and an output voltage of the negative comparator are A negative-side field effect transistor having a gate electrode inputted thereto, wherein the determination circuit adds the drain currents of the positive-side field-effect transistor and the negative-side field-effect transistor, and an integrated amount of the added drain current An integration circuit for outputting a voltage corresponding to the above (claim 8).

  In the fluxgate leakage sensor according to the eighth aspect, the fluctuation (ripple) of the voltage output from the integration circuit is reduced by increasing the sampling frequency, and the leakage is detected with high accuracy.

Preferably, the coil is wound over the entire circumference of the ring core.
According to the fluxgate leakage sensor of claim 9, since the coil is wound over the entire circumference of the ring core, magnetic field leakage from the ring core is suppressed, and the magnetic flux density of the ring core is reliably saturated with a small current. To do.

Preferably, the high resistance portion is made of ferrite, the low resistance portion is made of permalloy, and the coil is wound around a bobbin penetrated by the low resistance portion.
The flux-gate leakage sensor according to claim 10 is easily assembled by attaching a bobbin around which a coil is wound to the low resistance portion.

ADVANTAGE OF THE INVENTION According to this invention, the ring core for flux gate earth-fault sensors which an inductance is small and a magnetic flux density is easy to be saturated is provided.
Moreover, according to this invention, the ring core unit excellent in productivity provided with this ring core is provided.
Furthermore, according to the present invention, there is provided a fluxgate leakage sensor that includes the ring core and is suitable for increasing the sampling frequency and saving power.

It is a block diagram which shows the structural example of the fluxgate leak sensor of 1st Embodiment. FIG. 2 is an electric circuit diagram of the flux gate leakage sensor of FIG. 1. FIG. 3A is a timing chart in the electric circuit of FIG. 2 when there is no leakage, FIG. 3A is a time change of the coil current Ic detected by the current detection circuit, and FIG. 3B is a graph of the output voltage Vcp + of the positive comparator. FIG. 3C shows the time change of the output voltage Vcp− of the negative comparator, and FIG. 3D shows the time change of the output voltage Vout of the operational amplifier. 4 is a timing chart in the electric circuit of FIG. 2 when leakage occurs (when the current of one electric wire is large), FIG. 4A is a time change of the coil current Ic detected by the current detection circuit, and FIG. 4B shows the time change of the output voltage Vcp + of the positive side comparator, FIG. 4C shows the time change of the output voltage Vcp− of the negative side comparator, and FIG. 4D shows the time change of the output voltage Vout of the operational amplifier. Show. 5 is a timing chart in the electric circuit of FIG. 2 when leakage occurs (when the current of the other wire is large), FIG. 5A is a time change of the coil current Ic detected by the current detection circuit, FIG. 5B shows the time change of the output voltage Vcp + of the positive side comparator, FIG. 5C shows the time change of the output voltage Vcp− of the negative side comparator, and FIG. 5D shows the time change of the output voltage Vout of the operational amplifier. Show. It is a schematic perspective view of the ring core applied to the fluxgate leakage sensor of FIG. FIG. 7 is a schematic exploded perspective view of the ring core of FIG. 6. It is a schematic plan view of the ring core unit according to the second embodiment. It is a schematic perspective view of the ring core which concerns on 3rd Embodiment. It is a schematic perspective view of the ring core unit which concerns on 4th Embodiment. It is a schematic perspective view of the ring core which concerns on 5th Embodiment. It is a schematic plan view which shows the ring core of FIG. 11 in the state by which the coil was wound. It is a schematic perspective view of the ring core which concerns on 6th Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Flux gate leakage sensor]
FIG. 1 is a block diagram showing a schematic configuration of the fluxgate leakage sensor of the first embodiment. The fluxgate leakage sensor is applied to a set of electric wires 14 a and 14 b (hereinafter, collectively referred to simply as an electric wire 14) connecting the power source 10 and the load 12, and the electric leakage between the power source 10 and the load 12 is detected. Detect whether or not has occurred.
The power source 10 includes a power generator such as a solar power generation device, and the load 12 includes a storage battery that stores the generated electricity.

The flux gate leakage sensor has an annular ring core 16. The electric wire 14 is inserted into the center hole of the ring core 16.
A coil 18 is spirally wound around the ring core 16 so as to extend along the circumferential direction of the ring core 16, and the number of turns of the coil 18 is, for example, about 500. When a current is supplied to the coil 18, the magnetic flux extends so as to go around the inside of the ring core 16.

  A drive circuit 22 is connected to the coil 18, and the drive circuit 22 applies a voltage to the coil 18 with a positive and negative symmetrical rectangular wave in cooperation with the oscillation circuit 24. That is, the positive peak value and the negative peak value of the rectangular wave are the same, and the duty ratio of the rectangular wave is substantially 50%.

  A current detection circuit 26 is connected to the coil 18, and the current detection circuit 26 detects a current (coil current) flowing through the coil 18. The current detection circuit 26 is connected to the comparator circuit 30 and outputs a voltage (measurement voltage) corresponding to the coil current to the comparator circuit 30.

Then, the comparator circuit 30 compares the measurement voltage with positive and negative symmetrical positive side reference voltages and negative side reference voltages, and the positive side electrical signal corresponding to a period when the measurement voltage is higher than the positive side reference voltage, and the measurement voltage is A negative electric signal corresponding to a period lower than the negative reference voltage is output.
Note that the absolute values of the positive reference voltage and the negative reference voltage are substantially the same, and the polarities of the positive reference voltage and the negative reference voltage are opposite to each other.

A determination circuit 32 is connected to the comparator circuit 30, and the determination circuit 32 has a magnitude relationship between a current flowing through the electric wire 14a and a current flowing through the electric wire 14b based on the positive side electric signal and the negative side electric signal. Determine. If the current flowing through the electric wire 14a is different from the current flowing through the electric wire 14b, it is determined that a leakage has occurred.
Specifically, for example, when a current of 60 A flows through the electric wire 14 and there is a leakage of 30 mA, the leakage is detected by the flux gate leakage sensor.

FIG. 2 is a schematic electric circuit diagram of the fluxgate leakage sensor.
The drive circuit 22 and the oscillation circuit 24 are constituted by, for example, an operational amplifier 40, resistors 42, 44, 46 and a capacitor 48, and an output terminal of the operational amplifier 40 is connected to one end of the coil 18. In this case, with the charging / discharging of the capacitor 48, the output voltage of the operational amplifier 40 moves discontinuously between the positive saturation output voltage Es and the negative saturation output voltage −Es, and a rectangular wave voltage is supplied to the coil 18. Is done.

  The current detection circuit 26 includes, for example, resistors 50 and 52 and a capacitor 54, and the other end of the coil 18 is grounded via the capacitor 54 and the resistor 50. The resistor 52 is parallel to the resistor 50 with respect to the capacitor 54. It is connected to the. The coil current flowing through the coil 18 is supplied to the comparator circuit 30 through the resistor 52.

  The comparator circuit 30 includes, for example, a positive side comparator 70, a negative side comparator 80, resistors 71, 72, 73, 74, 75, 81, 82, 83, 84, 85, an n-channel type positive side field effect transistor (positive side). FET) 76 and a p-channel negative field effect transistor 86.

  For example, a + 9V three-terminal regulator 77 and a -9V three-terminal regulator 87 are connected to the comparator circuit 30 as positive and negative power supplies. The input terminals and output terminals of the three-terminal regulators 77 and 87 are capacitors 78, 79, They are grounded via 88 and 89, respectively.

  The output terminal of the three-terminal regulator 77 is grounded via resistors 72 and 71 and is connected to the positive power supply terminal of the positive comparator 70. Further, the output terminal of the three-terminal regulator 77 is connected to the drain electrode of the positive-side FET 76 and is connected to the gate electrode of the positive-side FET 76 via the resistor 74.

  The non-inverting input terminal (+ input terminal) of the positive side comparator 70 is connected to the resistor 52 of the current detection circuit 26, and the inverting input terminal (−input terminal) of the positive side comparator 70 is compared to the resistor 72. Connected in parallel. The output terminal of the positive side comparator 70 is connected to the gate electrode of the positive side FET 76 via the resistor 73.

  In contrast, the output terminal of the three-terminal regulator 87 is grounded via resistors 82 and 81 and is connected to the negative power source terminal of the negative comparator 80. Further, the output terminal of the three-terminal regulator 87 is connected to the drain electrode of the negative-side FET 86 and is connected to the gate electrode of the negative-side FET 86 via the resistor 84.

  The inverting input terminal (−input terminal) of the negative side comparator 80 is connected to the resistor 52 of the current detection circuit 26 in parallel with the non-inverting input terminal (+ input terminal) of the positive side comparator 70. The non-inverting input terminal (+ input terminal) is connected to the resistor 82 in parallel with the resistor 81. Further, the output terminal of the negative side comparator 80 is connected to the gate electrode of the negative side FET 86 via the resistor 83.

  The positive side comparator 70, the resistors 71, 72, 73, 74, 75 and the positive side field effect transistor (positive side FET) 76 described above constitute a positive side portion of the comparator circuit 30, and the negative side comparator 80, the resistance 81, 82, 83, 84, 85 and the negative side field effect transistor 86 constitute a negative side portion of the comparator circuit 30 that is symmetrical with the positive side portion.

The determination circuit 32 includes, for example, an addition / integration / amplification circuit 32A and a comparison circuit 32B.
The addition / integration / amplification circuit 32A includes an operational amplifier 90, resistors 91, 92, 93, and 94, and capacitors 95 and 96. The source electrode of the positive side FET 76 and the source electrode of the negative side FET 86 are connected via the resistors 91 and 92. In addition, the operational amplifier 90 is connected to the inverting input terminal and grounded through the resistor 91 and the capacitor 95.

  The non-inverting input terminal of the operational amplifier 90 is grounded via a resistor 93, and the inverting input terminal and the output terminal of the operational amplifier 90 are connected by a resistor 94 and a capacitor 96 that are parallel to each other. The output terminal of the operational amplifier 90 is connected to the comparison circuit 32B, and the comparison circuit 32B detects the occurrence of electric leakage based on the output voltage of the operational amplifier 90.

Hereinafter, the operation of the flux gate leakage sensor described above will be described.
FIG. 3 is a timing chart showing the operation when there is no electric leakage. FIG. 3A is a time change of the coil current Ic detected by the current detection circuit 26, and FIG. FIG. 3C shows the time change of the output voltage Vcp− of the negative-side comparator 80, and FIG. 3D shows the time change of the output voltage Vout of the operational amplifier 90.

  As shown in FIG. 3A, when there is no leakage, the magnetic field generated by the currents flowing through the wires 14a and 14b cancel each other, so that the coil current Ic is symmetric. The positive side comparator 70 compares the measured voltage corresponding to the coil current Ic with the positive side reference voltage, and outputs a constant voltage during a period when the measured voltage is higher than the positive side reference voltage, as shown in FIG. To do.

  Similarly, the negative-side comparator 80 compares the measured voltage corresponding to the coil current Ic with the negative-side reference voltage and, as shown in FIG. 3C, is constant for a period during which the measured voltage is lower than the negative-side reference voltage. Output voltage.

  When the absolute values of the constant voltages output by the positive comparator 70 and the negative comparator 80 are substantially equal and there is no leakage, the output voltage Vcp + of the positive comparator 70 and the output voltage Vcp− of the negative comparator 80 are also positive and negative symmetric. become.

  Since the drain voltage (9V) of the positive side FET 76 and the drain voltage (−9V) of the negative side FET are symmetrical with each other, the drain current (positive side electric signal) of the positive side FET 76 and the drain current of the negative side FET 86 ( The negative side electrical signal) is also symmetrical. Since the output voltage Vout of the operational amplifier 90 is obtained by adding these drain currents and amplifying a voltage corresponding to the sum of the added drain currents, the output voltage Vout is substantially zero as shown in FIG. Become.

On the other hand, FIG. 4 shows a timing chart in the case where leakage occurs and one of the currents flowing through the electric wires 14a and 14b becomes relatively large.
Specifically, in FIG. 4A, due to the occurrence of electric leakage, the magnetic field generated by the current flowing through the electric wires 14a and 14b does not cancel each other, and the positive side of the coil current Ic increases relative to the negative side. .

  For this reason, as shown in FIGS. 4B and 4C, the period in which the positive comparator 70 outputs a constant voltage is longer than the period in which the negative comparator 80 outputs a constant voltage. As a result, as shown in FIG. 4D, the output voltage Vout of the operational amplifier 90 becomes a finite value substantially larger than zero.

Similarly, FIG. 5 shows a timing chart in the case where a leakage occurs, but FIG. 5 shows a case where the other of the currents flowing through the wires 14a and 14b becomes relatively large, contrary to FIG. A timing chart is shown. In this case, as shown in FIG. 5D, the output voltage Vout of the operational amplifier 90 becomes a finite value substantially smaller than zero.
Therefore, the comparison circuit 32B of the determination circuit 32 can detect the occurrence of electric leakage based on the output voltage Vout.

[Ring core]
The ring core 16 has an annular shape, and includes a low resistance portion 16a having a low magnetic resistance per unit length and a high resistance portion 16b having a high magnetic resistance per unit length. The low resistance portion 16 a and the high resistance portion 16 b are connected in series with each other in the circumferential direction of the ring core 16.

FIG. 6 shows the ring core 16, which has a quadrangular ring shape with a side length of, for example, several centimeters.
Preferably, the high resistance portion 16b is made of a material having a lower magnetic permeability than the low resistance portion 16a. More preferably, the high resistance portion 16b is made of ferrite, and the low resistance portion 16a is made of permalloy.
In the present embodiment, the low resistance portion 16 a made of permalloy constitutes one side of the ring core 16. That is, the low resistance portion 16a has an I shape. The high resistance portion 16 b is made of ferrite having a smaller magnetic permeability than that of permalloy, and constitutes the remaining three sides of the ring core 16. That is, the high resistance portion 16b has a U shape or an angular C shape.

The coil 18 is wound over the entire circumference of the ring core 16, and thus is wound around each of the low resistance portion 16a and the high resistance portion 16b.
FIG. 7 shows the ring core 16 in an exploded manner. The low resistance portion 16a and the high resistance portion 16b are preferably bonded to each other by a powdered adhesive made of a magnetic material.

  According to the ring core 16 of the first embodiment described above, the high resistance portion 16b having a large magnetic resistance is provided in addition to the low resistance portion 16a having a small magnetic resistance, so that the case is made of only the low resistance portion 16a. The inductance of the ring core 16 itself is small, and the magnetic flux density of the ring core 16 is saturated with a small current.

And according to the ring core 16, the magnetic flux density of the ring core 16 is reliably saturated with a small electric current compared with the case where it consists only of a material with high magnetic permeability by using a material with low magnetic permeability for the high resistance part 16b.
Furthermore, the ring core 16 is provided at a low cost because it is easy to obtain the raw materials by using ferrite and permalloy as the raw materials.
In addition, according to the fluxgate leakage sensor using the ring core 16 of the first embodiment described above, the magnetic flux density of the ring core 16 is saturated with a small current, so that power saving is achieved and the drive circuit 22 is applied. The frequency of the voltage (sampling frequency) can be increased.

  Moreover, according to the flux gate leakage sensor of the first embodiment described above, the first electric wire is based on the period in which the measured voltage is higher than the positive reference voltage and the period in which the measured voltage is lower than the negative reference voltage. The magnitude relationship between the current flowing through and the current flowing through the second electric wire is determined. That is, leakage is detected based on a period in which the measured voltage is higher than the positive reference voltage and a period in which the measured voltage is lower than the negative reference voltage.

According to this flux gate leakage sensor, the sampling frequency can be increased by utilizing the fact that the magnetic flux density of the ring core 16 is saturated with a small current. By increasing the sampling frequency, when the current to be measured flowing through the electric wire 14 is an alternating current, it is possible to detect a leakage of a current having a higher frequency. That is, the frequency range to be measured is widened.
If the sampling frequency is not changed, the time required for the magnetic flux density of the ring core 16 to be saturated is shortened, and the measurement voltage is higher than the positive reference voltage and the measurement voltage is lower than the negative reference voltage. Since the low periods become longer, the measurement error during these periods is reduced, and the leakage is detected with high accuracy.

  Further, in the fluxgate leakage sensor, the voltage output from the addition / integration / amplification circuit 32A shown in FIGS. 3 (d), 4 (d) and 5 (d) is increased by increasing the sampling frequency. Fluctuation (ripple) is reduced, and leakage is detected with high accuracy.

  FIG. 8 shows a ring core unit according to the second embodiment, that is, the ring core 16 and the coil 100. The ring core 16 is the same as that of the first embodiment, but the coil 100 is wound only around the low resistance portion 16a of the ring core 16. That is, the coil does not need to be wound over the entire circumference of the ring core 16 and may be partially wound. However, in order to prevent the occurrence of a leakage magnetic field, the coil is preferably wound over the entire circumference.

  FIG. 9 shows a ring core 102 according to the third embodiment. The ring core 102 includes a low resistance portion 102a made of permalloy and a high resistance portion 102b made of ferrite, and the low resistance portion 102a and the high resistance portion 102b are fixed to each other by a powdered adhesive made of a magnetic material. .

  The ring core 102 is different from the ring core 16 in that the thickness, that is, the cross-sectional area of the low resistance portion 102a is smaller than that of the high resistance portion 102b. The ring core 102 is also different from the ring core 16 in that both ends of the high resistance portion 102b connected to the low resistance portion 102a are tapered. That is, the high resistance portion 102b has tapered portions at both ends that gradually become narrower as it approaches the low resistance portion 102a. According to the ring core 102, both ends of the high resistance portion 102b are formed in a tapered shape, so that the low resistance portion 102a and the high resistance portion 102a can be obtained even if the cross-sectional areas of the low resistance portion 102a and the high resistance portion 102b are different. Generation of a leakage magnetic field in the vicinity of the joint portion 102b is suppressed.

FIG. 10 shows the ring core unit, that is, the ring core 102, the bobbin 104, and the coil 106 according to the fourth embodiment. The bobbin 104 is made of a nonmagnetic material and is attached to the low resistance portion 102a. The bobbin 104 extends over substantially the entire region of the low resistance portion 102 a, and the coil 106 is wound around the outer peripheral surface of the bobbin 104.
When assembling this ring unit, preferably, a bobbin 104 around which a coil 106 is wound is prepared first. Then, the low resistance portion 102a is inserted into the prepared bobbin 104, and then the low resistance portion 102a and the high resistance portion 102b are bonded. In this case, the ring unit can be easily assembled by attaching the bobbin 104 around which the coil 106 is wound to the low resistance portion 102a.

FIG. 11 shows a ring core 108 according to the fifth embodiment. The ring core 108 is made of one type of magnetic material. The ring core 108 has a quadrangular ring shape, and a notch 109 is formed at the center of each side. Each notch 109 is formed on the inner peripheral side of the ring core 108. The part (reduced diameter part) where the notch 109 is formed has a smaller cross-sectional area than the other part (main body part). In the ring core 108, the main body part constitutes the low resistance part 108a, and The diameter portion constitutes the high resistance portion 108b.
In FIG. 11, the boundary between the low resistance portion 108 a and the high resistance portion 108 b is shown by a one-dot chain line for the sake of explanation, and the low resistance portion 108 a and the high resistance portion 108 b are alternately connected in the circumferential direction of the ring core 108. ing.

FIG. 12 shows a state where the coil 110 is wound around the ring core 108, and the coil 110 is wound around the entire circumference of the ring core 108. That is, the coil 110 is wound around each of the low resistance portion 108a and the high resistance portion 108b.
According to the ring core 108 of the fifth embodiment, since the high resistance portion 108b has a smaller cross-sectional area than the low resistance portion 108a, the inductance of the ring core 108 is reduced with a simple configuration, and the ring core 108 is reduced with a small current. The magnetic flux density is surely saturated.
The shape of the notch 109 is set so that the cross-sectional area of the high resistance portion 108b changes gently so that a leakage magnetic field is not generated.

FIG. 13 shows a ring core 112 according to the sixth embodiment. The ring core 112 has an annular shape, and notches 113 and 114 are formed on the inner peripheral side and the outer peripheral side. The cross-sectional area of the part (reduced diameter part) where the notches 113 and 114 are formed is smaller than that of the other part (main body part). In the ring core 112, the main body part constitutes the low resistance part 112a. The reduced diameter portion constitutes the high resistance portion 112b.
That is, the outer shape of the ring core 112 is not limited to a square shape, and the shape of the cutout portion forming the reduced diameter portion is not particularly limited as long as the generation of a leakage magnetic field is prevented.
In FIG. 13, the boundary between the low resistance portion 112a and the high resistance portion 112b is indicated by a one-dot chain line for explanation.

The present invention is not limited to the first to sixth embodiments described above and can be variously modified. For example, the configurations of the first to sixth embodiments may be combined as appropriate.
In addition, the circuit configuration described with reference to the first embodiment is only a preferable example, and the present invention can be suitably implemented even if various elements are added to the basic circuit configuration or a part thereof is replaced. Needless to say.
Furthermore, the ring core according to the present invention can be applied to other fluxgate leakage sensors as long as the leakage is detected using saturation of the magnetic flux density of the ring core.

DESCRIPTION OF SYMBOLS 10 Power supply 12 Load 14a, 14b Electric wire 16,102,108,112 Ring core 16a, 102a, 108a, 112a Low resistance part 16b, 102b, 108b, 112b High resistance part 18,100,106,110 Coil 22 Drive circuit 24 Oscillation circuit 26 Current detection circuit 30 Comparator circuit 32 Judgment circuit 70 Positive side comparator 76 Positive side field effect transistor (positive side FET)
80 Negative side comparator 86 Negative side field effect transistor (negative side FET)
104 Bobbins 109, 113, 114 Notch

Claims (10)

In the ring core for a fluxgate leakage sensor through which the first electric wire and the second electric wire to be measured are inserted,
A flux gate leakage sensor comprising a low resistance portion and a high resistance portion that are mutually connected in a circumferential direction of the ring core and differ in magnitude of magnetic resistance per unit length in the circumferential direction. Ring core.   The ring core for a fluxgate leakage sensor according to claim 1, wherein the high resistance portion is made of a material having a low magnetic permeability as compared with the low resistance portion. The high resistance portion is made of ferrite,
The flux gate leakage sensor according to claim 2, wherein the low resistance portion is made of permalloy.   The ring core for a fluxgate leakage sensor according to any one of claims 1 to 3, wherein the high resistance portion has a smaller cross-sectional area than the low resistance portion. A ring core for a fluxgate leakage sensor according to claim 2 or 3,
A bobbin penetrated by the low resistance part;
A ring core unit for a fluxgate leakage sensor, comprising a coil wound around the bobbin.   A fluxgate leakage sensor comprising a ring core for the fluxgate leakage sensor according to any one of claims 1 to 4. A coil wound around the ring core;
A drive circuit that applies a voltage to the coil with a positive and negative symmetrical rectangular wave so as to saturate the magnetic flux density of the coil while reversing the direction;
A measured voltage that changes in response to a coil current flowing through the coil is compared with a positive and negative symmetric positive reference voltage and a negative reference voltage, and the positive voltage corresponding to a period when the measured voltage is higher than the positive reference voltage. A comparator circuit that outputs a negative electric signal corresponding to a signal and a period in which the measured voltage is lower than the negative reference voltage;
The flux gate leakage sensor according to claim 6, further comprising a determination circuit that compares the positive electric signal output from the comparator circuit with the negative electric signal. The comparator circuit is
A positive comparator having a non-inverting input terminal to which the measurement voltage is applied and an inverting input terminal to which the positive reference voltage is input;
A negative comparator having an inverting input terminal to which the measurement voltage is applied and a non-inverting input terminal to which the negative reference voltage is input;
A positive-side field effect transistor having a gate electrode to which the output voltage of the positive-side comparator is input;
A negative-side field effect transistor having a gate electrode to which an output voltage of the negative-side comparator is input,
The determination circuit includes an integration circuit that adds drain currents of the positive-side field effect transistor and the negative-side field effect transistor and outputs a voltage corresponding to an integration amount of the added drain current. The fluxgate leakage sensor according to claim 7.   The fluxgate leakage sensor according to claim 7 or 8, wherein the coil is wound over the entire circumference of the ring core. The high resistance portion is made of ferrite,
The low resistance portion is made of permalloy,
The fluxgate leakage sensor according to claim 7 or 8, wherein the coil is wound around a bobbin penetrated by the low resistance portion.

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