JP3093532B2 - DC current sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC current sensor such as a DC earth leakage breaker, which has a relatively simple structure and has an excellent detection capability even for a minute current change. In particular, it relates to a high-sensitivity DC current sensor that prevents hysteresis of output characteristics.

[0002]

2. Description of the Related Art Recently, devices using DC such as electric devices and electric vehicles with built-in inverters have been increasing. However, the load of a DC motor incorporated in these various devices is detected and required power is detected. There has been an increasing need for sensors for controlling and DC current sensors used for DC earth leakage breakers and the like.

As a current sensor used for an AC leakage breaker or the like, a current sensor to which a current transformer is applied is widely known. However, this configuration cannot be adopted for the earth leakage breaker or the like used for the device using DC described above, and the shunt resistance method, the mag amplifier method, and the magnetic multivibrator method conventionally known as DC current sensors (Japanese Patent Application Laid-Open No. 47-1644, Japanese Unexamined Patent Publication No. 53
Japanese Patent Application Laid-Open No. 31176, JP-A-59-46859), and adoption of a Hall element system and the like are being studied.

[0004] The shunt resistance method is a method in which a shunt resistor is arranged in series with a conductor to be detected, and a potential difference generated at both ends of the shunt resistor is detected. The mag-amp system and the magnetic multivibrator system each use a core of a soft magnetic material formed by winding a detection coil in a toroidal shape, penetrate a detected wire inside the core, and apply a direct current flowing through the detected wire. Alternating magnetic flux generated by applying an alternating current to a coil wound on the core in advance by direct current demagnetization of the core of the soft magnetic material within the saturation magnetic flux density (Bs) by electric current, in the positive and negative directions In the former method, an imbalance is generated at the time of reaching saturation, and the change is detected by the detection coil. In the former method, a magnetic flux is changed in the core in advance. In the latter method, self-excited oscillation is performed by the action of a semiconductor or the like in a circuit connected to the detection coil, and according to the current to be detected. By changing the duty ratio of the oscillation waveform consists configured to oscillate.

Further, in the Hall element method, a detected wire is wound in a toroidal shape directly on a core of a soft magnetic material having a void portion in which a Hall element is disposed, and a DC current flowing through the detected wire is provided. Of the magnetic flux in the core based on the change of the magnetic field.

[0006]

However, the DC current sensor of each of the above types cannot be said to have a configuration capable of coping with a minute current change such as a DC leakage breaker for the following reasons. At present, it has not been put to practical use as a sensor. In other words, the shunt resistor method has a disadvantage that the shunt resistor itself is arranged as an electrical resistor in a circuit including the detection target wire, so that the electrical loss in the circuit increases and the electrical efficiency is poor. doing. Further, since a detection circuit for detecting a potential difference generated at both ends of the electric resistance is directly connected to the detected conductor, it is difficult to electrically insulate these detection circuits and the detected conductor. There is also a drawback that the detection circuit cannot be directly connected to an application circuit such as a microcomputer control circuit, and the versatility is poor.

[0007] In addition to having such a drawback, in order to adopt this shunt resistance method in an earth leakage breaker,
Although it is necessary to arrange two shunt resistors in the circuit of the conductor to be detected, it is practically difficult to make each shunt resistor have the same characteristics, and it is not possible to realize highly accurate potential difference measurement. . In addition, it is necessary to connect each other's detection circuits with very complicated electric circuits to detect slight leakage by comparing and comparing the potential difference measured by the detection circuits connected to each shunt resistor. Becomes
It is difficult to provide a highly practical DC current sensor.

In the mag-amp system and the magnetic multivibrator system, the detection circuit and the conductor to be detected can be electrically insulated. However, as described above, the direct current flowing through the conductor to be detected makes the soft magnetic material harder. It is necessary to perform DC bias so as to saturate the core to approximately the saturation magnetic flux density (Bs). When a known soft magnetic material such as Permalloy is used as the core, for example, when the current flowing through the detected wire is about several tens mA, the detected wire is connected to the soft magnetic material core by several tens to several hundred turns or more. It was necessary to wind the wire, and it was originally difficult to use it as a DC current sensor for an earth leakage breaker or the like that required one turn of the conducting wire to be detected.

In the Hall element system, these detection capabilities are inevitably determined by the characteristics of the Hall element. Therefore, when a currently known Hall element is used, for example, the current flowing through the conductor to be detected is several tens mA. In this case, it is necessary to wind the wire to be detected around a core of a soft magnetic material from several hundred turns to several thousand turns or more. As in the case of the above-described mag-amplifier method and magnetic multivibrator method, one turn of the detected wire is required. It has been difficult to use as a DC current sensor such as an earth leakage breaker that requires penetration.

The present invention solves the above-mentioned problems, has a relatively simple structure, and has an excellent detection capability even for a small current change such as a DC leakage breaker. It is an object of the present invention to provide a high-sensitivity DC current sensor that prevents hysteresis of output characteristics.

[0011]

Means for Solving the Problems The present inventors dispose a lead to be detected inside a detection core made of an annular soft magnetic material around which a detection coil is wound in a toroidal shape, and apply a direct current to this. , the magnetic field clockwise is generated with respect to the direction of the DC current, but the magnetic flux [Phi ₀ is generated in the detecting core, a magnetic flux [Phi ₀ since the current flowing through the lead wire being detected is the DC is constant, the detection Focusing on the fact that no electromotive force is generated in the coil, a magnetic switch is formed by forming a magnetic gap in a part of the detection core and opening and closing this part with a magnetic material. The generation of electromotive force in the detection coil by changing the magnetic flux Φ ₀ with time (ON-OFF) was studied.

Further, the present inventors have conducted various studies to make the above configuration more feasible. As a result, instead of using a mechanical magnetic switch, a DC current generated in a detection target wire is generated in a detection core. Means for periodically forming a magnetic gap in a part of the detection core by a magnetic flux generated in a substantially orthogonal direction with respect to a circumferential magnetic flux to be provided, and have substantially the same operation as the above magnetic switch. It has been confirmed that the objective can be achieved by realizing. As a specific configuration, an excitation core made of a soft magnetic material that is connected in a direction perpendicular to the circumferential direction of the detection core and forms an annular shape is integrally disposed on a part of the detection core, and the excitation core is An exciting coil is wound in a toroidal shape, and an exciting current is applied to the exciting coil to excite the exciting core in a direction perpendicular to the circumferential direction of the detecting core, and an orthogonal portion between the detecting core and the exciting core is formed. By periodically magnetically saturating, it is possible to adopt a configuration in which the magnetically saturated orthogonal portion is substantially a magnetic gap. That is,
The relative permeability μ of the magnetically saturated orthogonal portion of the detection core
Since it approaches 1 indefinitely, this magnetically saturated portion performs the same function as a magnetic gap, and the magnetic flux Φ ₀ in the detection core decreases at a fixed cycle, and the magnetic flux Φ ₀ is detected as the magnetic flux changes. This made it possible to generate an electromotive force in the coil.

Referring to FIG. 1, a detection coil 3 is wound in a toroidal shape on a detection core 2 made of an annular soft magnetic material through which the detection target wire 1 is disposed. An excitation core 4 made of a soft magnetic material connected in a direction perpendicular to the circumferential direction of the detection core 2 to form an annular shape is integrally disposed on a part of the 5 is wound in a toroidal shape to form a DC current sensor, and an AC current is applied to the exciting coil 5 to excite the exciting core 4 in a direction perpendicular to the circumferential direction of the detecting core 2. The magnetic flux generated in the detection core 3 is modulated based on the DC current I flowing through the detected conductor 1 by periodically magnetically saturating the core orthogonal portion 6 (the hatched portion in the figure) between the core 2 and the exciting core 4. To the detection coil By outputting the electromotive force of twice the frequency of the current, the DC current I flowing through the lead wire being detected 1
Can be detected.

More specifically, in the configuration shown in FIG. 1, when a DC current I flows through the detection target wire 1, a magnetic field clockwise in the direction of the DC current I is generated in the detection core 2. , A magnetic flux Φ ₀ is generated in the detection core. At this time, when a predetermined alternating current is applied to the exciting coil 5 to generate a magnetic flux periodically changing in the α direction in the drawing in the exciting core 4 and the exciting core 4 is periodically magnetically saturated, the detecting core The core orthogonal part 6 (the shaded part in the figure) which is a part in the circumferential direction of No. 2 has a relative magnetic permeability μ.
As r decreases, it becomes a so-called substantial magnetic gap very close to 1, and the magnetic flux Φ ₀ in the detection core is reduced to Φ ₁ . Here, the alternating current flowing through the exciting coil 5 is set to a frequency f _0, and when the exciting core 4 is saturated in the vicinity of the peak value of the current, the DC current I flowing through the detected conductor 1 becomes a positive (+) in FIG. In the case of the direction (upward in the figure), as shown in FIG. 3, the case where the DC current I flowing through the detected conductor 1 is in the minus (-) direction (downward in the figure), the exciting core 4 is rotated twice in one cycle of the exciting current. Will be saturated.

As shown in FIG. 2, when the DC current I flowing through the conductor 1 to be detected is in the plus (+) direction (upward in the figure),
Due to this saturation, the magnetic flux Φ ₀ generated by the direct current I flowing through the detected conductor 1 generated in the detection core 2 decreases to Φ ₁ at a frequency of 2f ₀ as shown in FIG. 2B. That is, modulation is performed at 2f ₀ . Accordingly, a voltage V _DET having a frequency of 2f ₀ is generated in the detection coil 3 as shown in FIG. In addition, as shown in FIG.
Is negative (-) (downward in the figure), the operation is substantially the same as the case where the DC current I is positive (+) (upward in the figure), but the direction of the DC current I is Since the direction is opposite, the direction of the magnetic flux generated in the detection core 2 is also opposite, and the frequency 2f ₀ generated in the detection coil 3
_Are 180 degrees different from each other.

However, the DC current I flowing through the detected conductor 1 is
Regardless of orientation, either case the flux [Phi ₀ alpha DC current I, the voltage from the relationship between the voltage V _DET alpha flux [Phi ₀ V
_{DET と な}り DC current I, which can be detected by the detection coil 3 in proportion to the DC current I flowing through the conductor 1 to be detected, and the DC current I flowing through the conductor 1 to be detected
You can know the absolute value of Further, since the detection core 2 and the excitation core 4 are connected at right angles to each other, basically, the excitation magnetic flux in the excitation core 4 does not leak to the detection core 2 side and passes through the detection coil 3. Therefore, no electromotive force is generated in the detection coil 3 by the excitation current applied to the excitation coil 5, and when the direct current I flowing through the detected wire 1 = 0, V _DET = 0. Also,
The frequency of the electromotive force V _DET generated in the detection coil 3 is 2f _0, which is different from the frequency f _{0 of the} excitation current applied to the excitation coil 5. even if the excitation magnetic flux of the exciting core 4 by the accuracy is detected by the detecting coil 3 is leaked, since the leakage component whose frequency is f _0, because it easily separated by a frequency discriminating filter and the like, highly sensitive It has been confirmed that it can be used as a DC current sensor.

Particularly, in the above configuration, only the orthogonal portion between the detection core and the excitation core formed in a part of the detection core is magnetically saturated, and the excitation core portion other than the orthogonal portion is magnetically unsaturated. By doing so, the core loss (iron loss) of the unsaturated portion can be reduced, and the exciting current applied to the exciting coil 5 can be reduced. Accordingly, the configuration of the excitation circuit is relatively simple, the power consumption of the entire sensor can be reduced, and the DC current sensor can be further miniaturized. Since the temperature rise in the core 4 is small, the change in the magnetic characteristics of the soft magnetic material constituting the excitation core 4 is small, the temperature drift of the output in the detection coil 3 can be reduced, and the stability of detection accuracy as a sensor is improved. can do.

However, in the DC current sensor described above, especially in detecting a minute current region (approximately ± 50 mA or less), the soft magnetic material constituting the detection core 2 has, as shown in FIG. Magnetic properties (coercive force)
However, the output voltage (output characteristic) of the detection coil 3 may cause hysteresis, and good current detection may not be performed. It has been difficult to use it for current sensors. The cause is that when the current I flowing through the through conductor (conductor to be detected) is zero, even if a soft magnetic material such as permalloy is used as the material, the material has a finite coercive force, so that a magnetic flux is generated in the core. The residual magnetic flux is
Until is canceled, a "reverse region" (a region where the output voltage decreases as the DC current increases) occurs due to the hysteresis phenomenon of the output voltage (electromotive force) at the detection coil in the minute current region. This is considered to cause level fluctuation.

According to the present invention, the measurement is performed at a level where the coercive force of the detection coil is not negligible, for example, in the case of detecting a minute current region as described above, or in the case where the magnetic path length becomes long to penetrate a thick through conductor. This is a proposal for a DC current sensor that has a configuration that prevents the occurrence of a reversal region due to the output voltage hysteresis phenomenon.A modulation coil that is wound around the detection core in the same direction as the conductor to be detected is provided. The alternating current magnetic field generated in the modulation coil is superimposed on the detection core to reduce the hysteresis of the output characteristic due to the residual magnetic flux of the core.

That is, according to the present invention, a part of the detection core made of an annular soft magnetic material is provided in the circumferential direction of the detection core.
A core orthogonal portion that is orthogonally connected to the excitation core is provided , the excitation core made of an annular soft magnetic material and the detection core are integrally disposed, and the detection coil and the excitation coil are wound around each core in a toroidal shape, respectively. A detection conductor through which a direct current for non-contact detection flows is disposed inside the detection core, and a modulation coil wound in the same direction as the detection conductor is disposed on the detection core. A DC current sensor characterized in that an alternating magnetic field generated in the DC current sensor can be superimposed on a detection core.

Here, the winding of the modulation coil around the detection core in the same direction as the detected conductor is performed by penetrating the detection core inside the detection core in the same direction as the detected conductor, as in the embodiment shown in FIG. In addition to arranging a one-turn modulation coil around the detection core, a plurality of turns of the modulation coil are wrapped around the detection core in the same direction as described above in accordance with the required strength of the alternating magnetic field. In the case of a turn, the coil is wound around the detection core in a toroidal shape substantially like the detection coil.

More specifically, in the configuration of FIG. 1, the modulation coil 43 is wound around the detection core 2 so as to penetrate in the same direction as the detection target wire 1, and a BH curve (BH curve) as shown in FIG. When an alternating current necessary for generating a magnetic field of ± Hc (coercive force) or more flows through the modulation coil 43 through the detection core 2 having a hysteresis curve), a minor loop is formed as shown in FIG. Then, the mark x of the center of the loop coincides with the origin O of the BH curve.

Hereinafter, the concept of the formation of the minor loop will be described in detail with reference to the drawings. As shown in FIG. 5A, for example, as shown in FIG. 5A, when a modulated AC current is not supplied to the modulation coil 43, a DC current is supplied to the detection target wire 1, and after reaching the point P on the BH plane, the DC current is cut off. , A ′ (that is, the magnetic flux density in the detection core 2 becomes −Br). In this state, when the above-described modulated AC current is applied to the modulation coil 43, the AC current waveform shifts from A to B, and A ′ → on the BH curve.
The position shifts to any position between B ′ and B ′ ₁ (usually a position near B ′ in the case of an alternating current). Hereafter, C → D →
The transition from C ′ → D ′ → E ′ is made on the BH loop with the change of E, and thereafter, the same route, that is, a minor loop Q indicated by a dotted line in the figure is drawn. The center of the minor loop Q coincides with the origin O of the BH curve. On the other hand, as shown in FIG. 5B, after the modulated AC current is not passed through the modulation coil 43, a DC current in the opposite direction is passed through the detected conductor 1, and after the detection core 2 is excited to the point R, When the DC current is cut, the point returns to the point S (that is, the magnetic flux density in the detection core 2 becomes Br). At this time, when an alternating current ABCDE... Is supplied to the modulation coil in the same manner as described above, the point S shifts to B ″ and then S ″.
Via, any position between D ′ and D′ 1 (usually,
(In the case of an alternating current, a position close to D '), and thereafter, the same route, that is, the minor loop Q indicated by a dotted line in the figure.
Will be drawn. The center of this minor loop Q is BH
It matches the origin O of the curve. The phenomena indicated by A and B in FIG. 5 indicate the same phenomena regardless of the current value and the direction of the DC current flowing through the detected conductor 1 before the modulation AC current flows. Coincides with the origin O of the BH curve.

Therefore, when a modulated AC current is passed through the modulation coil 43 and a modulation AC current is superimposed on the measured current while a DC current is flowing through the detected conductor 1, the detected conductor 1
The center mark x of this loop moves along the broken line shown in FIG. 6 while substantially maintaining the shape of the minor loop Q in accordance with the direction of the current, and by detecting this point, the hysteresis is substantially reduced. Has disappeared. Therefore, as shown in the configuration of FIG. 1, a modulation coil 43 wound around the detection core 2 in the same direction as the detection target wire 1 is disposed, and an alternating current necessary for generating a magnetic field of a coercive force or more is applied. In addition, it was confirmed that the detection sensitivity at a minute current can be improved by eliminating the hysteresis characteristic generated by the residual magnetic flux caused by the coercive force of the core material and removing the superimposed AC component by the detection circuit.

Further, as described with reference to FIGS. 2 and 3, the phases of the voltage V _DET of the frequency 2f ₀ generated in the detection coil 3 differ by 180 degrees depending on the direction of the DC current I flowing through the conductor 1 to be detected. Focusing on the excitation coil 5
To the excitation current, which is previously oscillated at twice the frequency of the excitation current from the oscillator, and halves the excitation current, and compares the phase difference between the output of the oscillator and the output of the detection coil. It has been confirmed that the detection by the circuit makes it possible to easily detect not only the absolute value of the direct current flowing through the detected wire, but also its direction. That is, the frequency of the exciting current oscillated from the oscillator connected to the exciting coil 5 and the frequency of the output V _DET from the detecting coil 3 are
In both cases, 2 of the exciting current finally applied to the exciting coil 5
Since the frequency is twice as high as 2f ₀ , these phase differences can be easily compared, and the direction and the absolute value of the DC current flowing through the detected wire can be detected.

As will be apparent from the above description, the present invention is directed to a core orthogonal portion which is orthogonally connected to the excitation core in the circumferential direction of the detection core on a part of the detection core made of the annular soft magnetic material as described above. the provided, and the detecting core and the exciting core consisting of an annular soft magnetic material integrally disposed, consisting configuration of arranging the detection coil and the excitation coil wound in each toroidally each core, the detecting core inner A detection conductor through which a direct current to be contactlessly detected flows is disposed, and a modulation coil wound in the same direction as the detection conductor is disposed on the detection core, and an alternating magnetic field generated in the modulation coil is detected by the detection core. The main feature is that the configuration can be superimposed on, further, the exciting coil, the frequency of the exciting current previously oscillated at twice the frequency of the exciting current from the oscillator, divided by 1/2,
The AC current applying means for periodically magnetically saturating the core orthogonal portion with the exciting current obtained by this is connected, and the detection core is superimposed on the DC current flowing through the conductor to be detected at the time of excitation. The output of the oscillator and the output of the detection coil is detected by a phase comparison means. Then, by detecting the direction along with the absolute value of the sum of the DC current flowing through the detected wire and the superimposed AC current, and removing the superimposed AC component from the detection signal, the output corresponding to the DC flowing through the detected wire is obtained. It is possible to provide a DC current sensor characterized in that the DC current sensor is obtained.

Further, in the above configuration, a pair of cylinders serving as excitation cores are arranged in parallel with their axial center lines parallel to each other, and the adjacent sides of the opening ends of the parallel cylinders are connected by a connection plate made of a soft magnetic material. By adopting a configuration in which the detection plate is formed integrally with the connection plate and the side surface of the cylindrical body connected to the connection plate, electromagnetic imbalance as a DC current sensor is reduced, noise generation is reduced, and S / N is reduced. It is possible to improve the ratio and the like. In addition, by adopting the configuration of the excitation core in which a pair of cylinders are arranged in parallel with the axial center line,
Compared to the configuration of FIG. 1, the width d (see FIG. 1) of the connection portion of the excitation core substantially connected to the detection core can be increased,
As a result, the ratio of the width d of the connection portion of the excitation core to the magnetic path length of the detection core (the ratio of the magnetic gap) is increased,
The effect of the demagnetizing field reduces the residual magnetic flux density in the detection core, and the effect of the coercive force of the core material can be further reduced by the synergistic effect with the arrangement effect of the modulation coil. In particular, the direct current sensor having another configuration shown in FIGS. 7 to 14 has the above-described effect, and is an effective configuration capable of realizing stable measurement. That is, FIG.
In the configuration shown in (1), the number of the excitation core 4 connected to the detection core 2 is one, and the positions of the detection coil 3, the excitation coil 5, and the modulation coil 43 are also one. Although it is difficult to balance the target, the configuration considering the electromagnetic balance arrangement of the excitation core 4, the detection coil 3, the excitation coil 5, and the modulation coil 43 is the configuration described with reference to FIGS. .

In FIG. 7, reference numeral 1 denotes a conductive wire to be detected, which is disposed so as to penetrate a central portion of the inside of a rectangular frame-shaped detection core 2.
A pair of detection coils 3a and 3b are wound in a toroidal shape on the short sides of the rectangular frame-shaped detection core 2 at the opposing positions, and are electrically connected to each other. In addition, a pair of excitation cores 4a, 4b
Are arranged integrally so as to form a quadrangular cylindrical shape. Further, excitation coils 5a and 5b are wound in a toroidal shape on the outermost side surfaces of the pair of excitation cores 4a and 4b, respectively. Further, a pair of modulation coils 43 wound around the rectangular frame-shaped detection core 2 so as to penetrate in the same direction as the detection target wire 1.
a and 43b are arranged. These modulation coils 43
a and 43b are electrically connected in series by predetermined means. In other words, a pair of square cylinders serving as the excitation cores 4a and 4b are arranged in parallel with their axial center lines parallel to each other, and a connection plate made of a soft magnetic material is connected between adjacent sides of each open end of the parallel square cylinders. The connection plate and the side wall of the cylindrical body connected to the connection plate, that is, the core orthogonal portion 6, constitute the detection core 2 having a rectangular frame shape. The connection plates have detection coils 3a and 3b, respectively. The excitation coil 5 is wound in a toroidal shape, and is provided on the outermost side surface of each of the pair of excitation cores 4a and 4b.
a and 5b are wound in a toroidal shape, and a pair of modulation coils 43a and 43b are wound around the rectangular frame-shaped detection core 2 so as to penetrate in the same direction as the detected conductor 1. In such a configuration, when the DC current I flows through the detection target wire 1, a magnetic field clockwise in the direction of the DC current I is generated in the detection core 2, and the magnetic flux Φ ₀ is generated in the detection core 2. . At this time, a predetermined alternating current is applied to the exciting coils 5a and 5b to generate a magnetic flux that periodically changes in the α direction in the pair of exciting cores 4a and 4b.
Periodically magnetically saturates the detection core 2 in the form of a rectangular frame.
Is a so-called substantial magnetic gap whose relative magnetic permeability μ is very close to ₁ , and reduces the magnetic flux Φ ₀ in the detection core to Φ ₁ . .

Therefore, also in the DC current sensor described above, the mechanism of generating the electromotive force to the pair of detection coils 3a and 3b is the same as the configuration shown in FIG. 1, and the effect based on this mechanism is also obtained. Further, in this configuration, the width d of the connection portion of the excitation cores 4a, 4b connected to the detection core 2 is substantially equal to the dimension L of the sensor in the length direction in the figure, in addition to the arrangement effect of the pair of modulation coils 43a, 43b. Double (2
L), the ratio of the width d of the connection portion of the excitation core 4 to the magnetic path length of the detection core 2 becomes extremely large.
The residual magnetic flux density in the detection core 2 due to the effect of the demagnetizing field can be reduced as compared with the configuration described above, and the hysteresis phenomenon caused by the coercive force of the core material can be reduced by the synergistic effect of these. In addition, since the overall configuration of the DC current sensor is symmetrical with respect to the detection target wire 1, the electromagnetic balance is good, and stable measurement can be realized. The detection core 2 and the excitation cores 4a and 4b constituting the above-described DC current sensor are formed by punching a plate made of a predetermined soft magnetic material into a shape shown in FIG. It can be easily obtained as an integrated product by spot welding.

FIG. 9 shows another configuration, except that a pair of detection coils 3a and 3b are wound around the pair of excitation cores 4a and 4b together with the excitation coils 5a and 5b in a toroidal shape. 7 has the same structure as that of FIG. 7, and a DC current flowing through the detection target wire 1 can be detected by a mechanism basically similar to that of FIG. FIG. 10 also shows another configuration in which a pair of exciting coils 5a and 5b are
A pair of excitation cores 4 arranged to form a square tube
Except for being wound in a toroidal shape on the exciting coil winding bars 8a, 8b formed at the inner central portions of the insides a, 4b, the structure is substantially the same as that of FIG. By a similar mechanism, it is possible to detect a direct current flowing through the detected conductor 1. In the configuration shown in FIG. 9, a pair of modulation coils 43a and 43b are wound around the short sides of the rectangular frame-shaped detection core 2 at opposing positions. However, in the configuration shown in FIG. Modulation coil 4
The reference numerals 3a and 43b are wound around the long side of the detection core 2 having a rectangular frame shape. These modulation coils 43a and 43b are electrically connected in series by predetermined means.
In particular, in the configuration of FIG. 10, the excitation cores 4a and 4b are formed in advance in an E-shaped cross section as shown in FIG. 11, so that the excitation core wound in advance on the bobbin 9 having a predetermined shape and dimensions. After the coils 5a, 5b are inserted into the exciting coil winding bars 8a, 8b, they can be easily manufactured by being integrated with a rectangular frame-shaped detection core by a predetermined means. Further, in the configuration shown in FIG. 9, the magnetic flux generated in the pair of exciting coils 5a, 5b leaks to the outside of the exciting cores 4a, 4b.
When the excitation signal is mixed with b, and particularly when a minute current is detected, the level of the mixed signal becomes higher than the detection signal, and there is a possibility that the sensitivity may be reduced. However, in the configuration of FIG. 10, the magnetic flux generated in the excitation coils 5a and 5b does not leak outside the excitation cores 4a and 4b, respectively.
It works efficiently and the adverse effect on the detection coils 3a and 3b is reduced.

Further, focusing on the magnetic path in the orthogonal portion 6 of each of the detection core 2 and the excitation cores 4a and 4b in each configuration, the configuration of FIG. 9 basically includes, as shown in FIGS. Although the magnetic path of one circuit acts so that the direction of the magnetic flux changes alternately, in the configuration of FIG. 10, basically, as shown in FIGS. 8b, the magnetic paths of the two circuits act so that the direction of the magnetic flux changes alternately.
The electromagnetic balance is further improved. FIG.
When adopting the configuration described in
Since the magnetic flux concentrates on a and 8b, it is desirable to set the thickness of the exciting coil winding bars 8a and 8b to about twice as thick as the other portions in advance.

Further, in the configuration shown in FIG. 9, in order to prevent the excitation signals from being mixed into the detection coils 3a, 3b due to the capacitive coupling between the excitation coils 5a, 5b and the detection coils 3a, 3b, for example, as shown in FIG. As shown in FIG.
It is preferable that a metal foil 70 of high electrical conductivity such as Cu or Al, which is electrically grounded, is interposed between the detection coils 3a and 3b and the detection coils 3a and 3b. That is, the outer circumferences of the excitation coils 5a, 5b are covered with the above-mentioned metal foil 70 while securing the electrical insulation, and the outer circumferences of the metal foil 70 are secured with the electrical insulation, and the detection coils 3a, 3b are secured. Is wound. However, it is necessary that the metal foil 70 be electrically cut at least at one location in the winding direction (in the figure, a slit portion 71 extending in the axial direction is formed). By adopting such a configuration,
Detection with even higher accuracy is possible.

The direct current sensors shown in FIGS. 9 and 10 also have the same mechanism for generating electromotive force to the pair of detection coils 3a and 3b as the structure shown in FIG. The arrangement effect, the reduction effect of the residual magnetic flux density in the detection core 2 based on the effect of the demagnetizing field by increasing the ratio of the width d of the connection portion of the excitation core 4 to the magnetic path length of the detection core 2, and the overall configuration are as follows. The electromagnetic balance effect and the like due to the symmetry with respect to the detected conductor 1 can be obtained similarly to the configuration shown in FIG.

Further, the present inventor also proposes a DC current sensor in which the above-described configuration is further improved. That is, not only the effect of the arrangement of the modulation coil and the effect of the demagnetizing field by enlarging the width of the connection part of the excitation core, but also the demagnetization effect of the detection core by devising the arrangement of the excitation coil. The present invention proposes a DC current sensor capable of reducing the occurrence of the reverse rotation region in the minute current region described above and obtaining stable output characteristics, and has a specific configuration shown in FIG. It will be described based on.

As shown in FIG. 15, a modulation coil 43 wound around the detection core 2 so as to penetrate in the same direction as the conductor 1 to be detected is arranged, and a connection portion of the excitation core 4 connected to the detection core 2 is provided. Is increased, the ratio of the width d of the connecting portion of the exciting core 4 to the magnetic path length of the detection core 2 (the ratio of the magnetic gap) is increased, and the residual of the exciting core 4 due to the effect of the demagnetizing field. Reduce the magnetic flux density,
Exciting coil 5 for generating magnetic flux in a predetermined direction in exciting core 4
Is wound around the outer periphery of the detection core 2 in the circumferential direction of the detection core 2 so that the exciting coil 5 also has a demagnetizing effect of the detection core 2, and the occurrence of the “reverse rotation region” is substantially reduced. This is a DC current sensor set to zero. The hatched portion 6 is a core orthogonal portion. Also in the DC current sensor having this configuration, the frequency 2f ₀ is applied by applying an AC current having a frequency f ₀ as an excitation current to the exciting coil 5 by the same electromotive force generation mechanism as the DC current sensor having the configuration shown in FIG. voltage V _DET of it than is to be generated in the detection coil 3.

That is, according to the present invention, a part of the detection core made of an annular soft magnetic material is provided in the circumferential direction of the detection core.
A core orthogonal portion that is orthogonally connected to the excitation core is provided , the excitation core made of an annular soft magnetic material and the detection core are integrally disposed, a detection coil is wound around the detection core in a toroidal shape, and the detection is performed. An excitation coil wound around the detection core in a circumferential direction is wound around the core, and a detection target wire through which a direct current for non-contact detection flows flows through the inside of the detection core. A DC current sensor comprising a modulation coil wound in the same direction as a detection lead wire, and an alternating magnetic field generated by the modulation coil can be superimposed on a detection core.

Also, in the DC current sensor having the configuration shown in FIG. 15, similarly to the DC current sensor having the configuration shown in FIG. 1, the excitation coil 5 previously oscillates at twice the frequency of the excitation current from the oscillator. An exciting current in a state where the frequency of the exciting current is divided by 印 加 is applied, and a phase difference between the output of the oscillator and the output of the detecting coil is detected by the phase comparing means. In addition to the absolute value, the direction can be easily detected. That is, both the frequency of the exciting current oscillated from the oscillator connected to the exciting coil 5 and the frequency of the output V _DET from the detecting coil 3 are equal to the two of the exciting current finally applied to the exciting coil 5 as described above. Since the frequency becomes twice as high as 2f ₀ , the frequency of the oscillator and the frequency of the output V _DET of the detection coil 3 become the same, so that these phase differences can be easily compared with each other. The direction can be detected together with the absolute value.

[0038] Accordingly, the present invention is provided with a core perpendicular section perpendicular connecting the exciting core with respect to the circumferential direction of the detecting core in a portion of the detecting core consisting of an annular soft magnetic material as described above, annular soft An excitation core made of a magnetic material and the detection core
And a detection coil is wound around the detection core in a toroidal shape, and an excitation coil wound in the circumferential direction of the detection core is wound around the detection core. A detection conductor through which a direct current for non-contact detection flows is penetrated inside the detection core, and a modulation coil wound in the same direction as the detection conductor is disposed on the detection core, and an alternating magnetic field generated in the modulation coil is provided. The main feature of the configuration is that it can be superimposed on the detection core.Furthermore, in the excitation coil, the frequency of the excitation current oscillated at twice the frequency of the excitation current from the oscillator in advance is divided by 1/2, thereby Obtained
AC current applying means for periodically magnetically saturating the core orthogonal portion with the exciting current is connected, and the magnetic flux generated in the detecting core based on the AC current superimposed on the DC current flowing through the detected wire at the time of excitation is connected. Modulation is possible, and the detection coil outputs an electromotive force twice the frequency of the excitation current.
The phase difference between the output of the oscillator and the output of the detection coil is detected by phase comparison means, and the direction is detected along with the absolute value of the sum of the DC current flowing through the detected wire and the superimposed AC current, and By removing the superimposed AC component, it is possible to provide a DC current sensor characterized by obtaining an output corresponding to the DC flowing through the detected conductor.

Further, in the above construction, a pair of cylinders serving as excitation cores are arranged in parallel with their axial center lines parallel, and the adjacent sides of the opening ends of the parallel cylinders are connected by a connection plate made of a soft magnetic material. By adopting a configuration in which the detection core is formed integrally with the connection plate and the side surface of the cylindrical body connected to the connection plate, a more stable measurement can be performed similarly to the DC current sensor shown in FIGS. 7 to 14 described above. Can be realized.

FIG. 16 shows an improved configuration of the DC current sensor shown in FIG. That is, reference numeral 1 denotes a conductive wire to be detected, which is disposed so as to penetrate the inner central portion of the rectangular frame-shaped detection core 2. A pair of detection coils 3a and 3b are wound in a toroidal shape on the short sides of the rectangular frame-shaped detection core 2 at the opposing positions, and are electrically connected to each other.
Further, a pair of modulation coils 43a and 43b are wound at the same position so as to penetrate in the same direction as the conductive wire 1 to be detected, and are electrically connected to each other in series by predetermined means. In addition, a pair of excitation cores 4a and 4b are integrally arranged on the long sides at the opposing positions so as to form a quadrangular cylindrical shape. Further, an exciting coil 5 is wound around the outer periphery of the rectangular frame-shaped detection core 2 in the circumferential direction. In other words, a pair of square cylinders serving as the excitation cores 4a and 4b are arranged in parallel with their axial center lines parallel to each other, and a connection plate made of a soft magnetic material is connected between adjacent sides of each open end of the parallel square cylinders. The connecting plate and the side wall of the cylindrical body connected to the connecting plate, that is, the core orthogonal portion 6, constitute the above-described rectangular frame-shaped detecting core 2. The connecting plate portion has detecting coils 3a, 3a respectively.
b is wound in a toroidal shape, the exciting coil 5 is wound around the outer periphery of the detection core 2, and the modulation coils 43 a and 43 b are respectively wound around the connection plate of the detection core 2.

In the DC current sensor having this configuration,
At construction DC current sensor similar electromotive force generation mechanism shown in FIG. 15, the frequency 2f ₀ by applying an alternating current of frequency f ₀ as the exciting current to the exciting coil 5
Voltage V _DET of it than is to be generated in the detection coil 3. Further, in this configuration, the width d of the connection portion between the excitation cores 4a and 4b connected to the detection core 2 is twice (2L) the dimension L in the length direction of the sensor in the figure.
The ratio of the width d of the connection portion of the excitation core 4 to the magnetic path length becomes extremely large, and the residual magnetic flux density in the detection core 2 further decreases due to the effect of the demagnetizing field. In addition, since the entire configuration of the DC current sensor is symmetrical with respect to the detected conductor 1, the electromagnetic balance is good and stable measurement can be realized. In the DC current sensor having the configuration shown in FIG. 16, similarly to the DC current sensor having the configuration shown in FIG. 15, the exciting coil 5 is supplied with the frequency of the exciting current previously oscillated at twice the frequency of the exciting current from the oscillator. By applying an exciting current in a 1/2 frequency divided state and detecting a phase difference between the output of the oscillator and the output of the detection coil by a phase comparison circuit, the direction and the absolute value of the DC current flowing through the wire to be detected are detected. Can also be easily detected. Further, the modulation coil 43a,
43b is wound and connected to an AC power supply to supply an AC necessary to generate a magnetic field of ± Hc or more, thereby eliminating output hysteresis characteristics caused by residual magnetic flux caused by coercive force of the core material. In detecting the direction and the absolute value of the DC current flowing through the detection target wire 1 described above,
It is possible to stably detect with high sensitivity even with a small current without generating a reverse rotation region.

FIG. 17 is also a perspective explanatory view showing an embodiment of the present invention in which the DC current sensor having the structure shown in FIG. 15 is improved. In particular, the structure can be reduced in size as compared with other embodiments. Although the direct current sensor shown in FIG. 17 is basically not different from the configuration of FIGS. 15 and 16, a cylindrical core is formed so as to be orthogonal to the opening direction of a rectangular parallelepiped core having two opposing surfaces opened in one direction. It is arranged so as to penetrate through the rectangular parallelepiped core, the cylindrical core is used as the detection core 2 and the rectangular core is used as the excitation core 4, at a symmetric position of the detection core 2 made of a cylindrical soft magnetic material (in FIG. , The detection coils 3a, 3b, 3c, 3d are respectively wound and arranged in a toroidal shape, and the exciting coil 5 is wound around the outer periphery of the detection core 2; A direct current sensor is configured by arranging the penetrated conducting wires 1. A pair of modulation coils 43a and 43b wound around the detection core 2 having a cylindrical shape so as to penetrate in the same direction as the detection target wire 1 is disposed. Also in this configuration, the same operation and effect as in FIG. 16 can be obtained.

When the DC current sensor of the present invention having the various configurations described above is used by being incorporated in an inverter device, in particular, in order to prevent switching noise from being mixed in, the power supply line of the detection circuit has a noise. Although it is effective to insert a filter, as shown in FIG. 18, a DC current sensor of the present invention is replaced with a shield case (51a in the figure) made of permalloy, non-oriented silicon steel plate or the like.
Is a case main body, and 51b and 51c are case lids.)
It is desirable to cover with a to prevent mixing of induction noise.

The DC current sensor of the present invention described above is constituted by effectively disposing an annular soft magnetic material as the detection core and the excitation core. The magnitude of the current flowing through the conductor to be detected, that is, the sensor, It is preferable to select the material of each soft magnetic material according to the detection sensitivity required for the above. Normally, permalloy is preferable in consideration of workability and the like together with magnetic properties, but other known soft magnetic materials such as silicon steel plate, amorphous, soft magnetic iron, and soft ferrite can be used, and these may be used in combination. Further, in the DC current sensor described above, the annular soft magnetic material is not limited to the soft magnetic material having a so-called ring shape, and the soft magnetic material can form an electromagnetic closed circuit. And various configurations such as an elliptical ring, a rectangular frame, and the like can be adopted in addition to the ring shape as shown in the figure.

The magnetic gap formed in the detection core is not limited to one location in the detection core, but may be at a plurality of locations. As shown in the various configurations described above, It is desirable to set the formation location in consideration of a proper balance. In the DC current sensor of the present invention based on the configuration of FIG. 1, regarding the magnetic saturation in the orthogonal section of the core between the detection core and the exciting core, for example, the orthogonal section of the core does not realize perfect geometric orthogonality. If it is possible to achieve a substantially saturated state even if complete saturation is not achieved, the intended detection can be achieved. Therefore, by selecting the optimum conditions such as the shape and size of the soft magnetic material, the number of turns of the detection coil and the number of turns of the exciting coil together with the material of the soft magnetic material, it is possible to provide a sensor with higher practicality.

Further, in any of the above configurations,
The number of conductors passing through the detection core is not limited to one, and a plurality of conductors may be penetrated according to the required size of the sensor. The effect of the DC current sensor having the configuration described above can be exhibited most effectively.

The modulation coil, which is one of the main features of the present invention, is wound in the same direction and at substantially the same place as the detection coil wound toroidally on the detection core. It can be shared by coils. That is, since the frequency of the current flowing through the detection coil and the frequency of the current flowing through the modulation coil are significantly different from each other, even when they are shared, a filter that appropriately passes a current having a frequency that realizes each function is appropriately arranged. Thus, the electric signal can be easily separated, and the object of the present invention can be achieved even if a configuration in which the modulation coil and the detection coil are integrated is adopted.

[0048]

The operation of the DC current sensor of the present invention will be described with reference to FIG.
The description will be made based on the most compact configuration shown in FIG. The direct current sensor shown in FIG. 17 is, as described above,
A cylindrical core is penetrated through the rectangular parallelepiped core so as to be orthogonal to the opening direction of the rectangular parallelepiped core having two opposing surfaces opened in one direction, and the cylindrical core is used as the detection core 2 and the rectangular core is used as the exciting core 4. The detection coils 3a, 3b, 3c, and 3d are respectively wound in a toroidal shape at symmetrical positions (four places in the figure) of the detection core 2 made of a cylindrical soft magnetic material. An excitation coil 5 is wound around the outer periphery of the detection core 2, and a detection target wire 1 penetrating through the inside of the cylindrical detection core 2 is arranged to constitute a DC current sensor. A pair of modulation coils 43a and 43b wound around the cylindrical detection core 2 so as to penetrate in the same direction as the detection target wire 1 are arranged and connected to a predetermined AC power supply.

Here, an exciting current is applied to the exciting coil 5 in a state where the frequency of the exciting current oscillated at twice the frequency of the exciting current 2 f ₀ from the oscillator is halved in advance. For example, the exciting coil 5 is connected to an alternating current applying means 10 as shown in FIG. The AC current applying means 10 has a frequency 2f which is twice the exciting current finally applied to the exciting coil 5.
An OSC (oscillation circuit, oscillation circuit) that oscillates an exciting current of ₀ , and a T-FF (trigger flip-flop) that divides the frequency of the exciting current by half are arranged. The AC current obtained by dividing the frequency from 2f ₀ to f ₀ is connected to the excitation coil 5 via an LPF (Low Pass Filter) and a buffer amplifier. Alternating current necessary for generating a magnetic field of ± Hc or more of the detection core 2 made of the soft magnetic material having the above-described configuration is applied to the modulation coils 43a and 43b by an alternating current applying means (not shown) separately connected. In this case, an alternating magnetic field is generated to eliminate the hysteresis characteristic generated by the residual magnetic flux caused by the coercive force of the core material.

When a DC current I flowing in a predetermined direction flows through the conductive wire 1 to be detected, the above-described mechanism for generating an electromotive force is generated by the excitation current applied to the excitation coil 5 and having the frequency f ₀ divided by １ ／. Similarly to the above, the magnetic flux generated in the detection core 2 is modulated, and the exciting current is twice as large as the exciting current proportional to the sum of the direct current I flowing through the detected wire 1 through the detecting coil 3 and the alternating current flowing through the modulating coils 43a and 43b. It is possible to output an electromotive force having a frequency of 2f _0, and it is possible to know the absolute value of the DC current I flowing through the detected conductor 1 by removing the AC component from the output generated in the detection coil. . 2 and 3 that the phases of the voltage V _DET of the frequency 2f ₀ generated in the detection coil 3 differ by 180 degrees depending on the direction of the DC current I flowing through the detection target wire 1.
As described above. Output (electromotive force) consisting of frequency 2f ₀ generated in detection coil 3 in this way
Is input to the phase comparison circuit 20 (see FIG. 19).

On the other hand, O constituting the AC current applying means
Some of the exciting current consisting of the frequency 2f ₀ oscillated from SC, without being connected to the exciting coil 5 via the T-FF and the like, while LPF (low pass filter) frequencies 2f _0, the phase shifter (phase shifter ), And input to the phase comparison circuit 20 (see FIG. 19) via a Schmitt trigger or the like. The phase comparison circuit 20 detects a phase difference between the output from the oscillator input to the circuit 20 and the output from the detection coil 3, and finally detects the phase difference corresponding to the direction of the DC current I flowing through the detected wire 1. An output voltage V _OUT as shown in FIG. 22 is output. Since the detection coil has an output in which the DC current I to be measured and the AC current flowing through the modulation coils 43a and 43b are combined, it is necessary to remove the AC component. As a method for removing this AC component, 1) a bandpass filter having a high Q with a passing frequency of 2fo is used, and 2) a phase detection is performed as it is, and a superimposed AC component is removed from the obtained output by a low-pass filter or the like. Is valid. That is, as can be understood from FIGS. 2 and 3, the output from the oscillator 11 and the detection coil 3
If there is no phase difference from the output from the control unit 1, it is determined that the direction of the DC current I flowing through the detected conductor 1 is flowing in the plus (+) direction (upward in FIG. 1), and the phase difference is 180. If there is a certain degree, it is determined that the direction of the DC current I flowing through the conductive wire 1 to be detected is flowing in a minus (-) direction (downward in FIG. 1), and the absolute value of the DC current I is output together with those directions. It becomes possible.

In particular, in the DC current sensor of the present invention, both the frequency of the exciting current oscillated from the oscillator connected to the exciting coil 5 and the frequency of the output V _DET from the detecting coil 3 finally become the same. Since the frequency becomes 2f _{0 which} is twice the frequency of the exciting current applied to the output, the phase difference between the outputs having the same frequency can be easily compared. For example, the configuration is relatively simple as shown in FIG. It is possible to detect the direction of the direct current flowing through the detected wire by using a known phase comparison circuit. The operation of the present invention described above is similar not only to the DC current sensor having the configuration shown in FIG. 17 but also to the DC current sensor having another configuration according to the present invention. It is possible to realize an effect utilizing the characteristics that have been obtained.

[0053]

【Example】

Example 1 Permalloy C (78% Ni-5% Mo-4% Cu-ba
A core assembly shown in FIG. 16 was obtained by punching out a 0.35 mm-thick thin plate made of 1Fe) into a predetermined shape, bending a predetermined portion and assembling the same, and spot welding. Where L
= 20 mm, H = 10 mm, W ₁ = 21 mm, W ₂ = 3 m
m. The above assembly was placed in a hydrogen gas atmosphere for 1100
After the heat treatment of 3 hours at a temperature of 600C to 400C, the heat treatment of multi-stage cooling at a rate of 100C / hour between 600C and 400C was completed to obtain a DC current sensor. After winding an insulating protective vinyl tape around a required position of the detection core 2 having a rectangular frame shape, a formal wire having an outer diameter of 0.1 mm is wound around each short side of the detection core 2 by 40 turns. The detection coils 3a and 3b were formed, and a formal wire having an outer diameter of 0.3 mm was wound around the outer circumference of the detection core 2 for 20 turns to form the excitation coil 5. A detection conductor 1 made of vinyl coating having an outer diameter of 8 mm was penetrated inside the detection core 2. Further, a formal wire having an outer diameter of 0.1 mm was wound around each short side of the rectangular frame-shaped detection core 2 by 10 turns to form modulation coils 43a and 43b.

As the DC current sensor of the present invention, the excitation coil 5 and the detection coil 3
And an AC current applying means and a phase comparison circuit for arranging an oscillator for generating an exciting current having a frequency twice as high as the exciting current to be applied to the oscillator.
An alternating current of 14.2 kHz and 300 mA flows, and 100 Hz and 5 mA (peak time) are applied to the modulation coils 43a and 43b.
Sinusoidal AC current of ± 5
When the DC current I is increased or decreased in the range of 0 mA and flows, the detection coil 3 (3 in FIG.
out of the electromotive force (output) V _OUT of
FIG. 20 shows a change in output after the 00 Hz AC component is removed by the low-pass filter. The output voltage V
_OUT is a value output via an amplification circuit having an amplification effect.

FIG. 21 shows a comparative example, in which the DC current sensor of the present invention was measured under the same conditions except that the modulation coils 43a and 43b, which are the features of the present invention, were not arranged. . When FIG. 20 which is the measurement result by the DC current sensor of the present invention is compared with FIG. 21 which is the measurement result by the DC current sensor of the comparative example, the electromotive force of the detection coil 3 based on the DC current flowing through the detection target wire ( Output direction can be detected, that is, the direction can be detected together with the absolute value of the DC current flowing through the conductor to be detected. It is clear that large differences occur in the measurements at. That is, in the DC current sensor of the comparative example, a large hysteresis phenomenon appears in the output characteristics, and the error output due to the reciprocating current is very large. On the other hand, in the DC current sensor of the present invention, the S / N is small even at a very small current of 10 mA. It is clear that the measurement can be performed at a ratio of 10 times or more, the difference detection sensitivity does not decrease due to the magnitude of the reciprocating current, and the error output due to the reciprocating current is small.

Example 2 Permalloy C (78% Ni-5% Mo-4% Cu-ba
A core assembly shown in FIG. 17 was obtained by punching out a thin plate made of 1Fe) having a thickness of 0.1 mm into a predetermined shape, bending a predetermined portion and assembling the same, and spot welding. Where L =
35 mm, H = 15 mm, W ₁ = 35 mm, W ₂ = 10 m
m. The above assembly was placed in a hydrogen gas atmosphere for 1100
After the heat treatment of 3 hours at a temperature of 600C to 400C, the heat treatment of multi-stage cooling at a rate of 100C / hour between 600C and 400C was completed to obtain a DC current sensor. After winding an insulating protective vinyl tape around a required position of the cylindrical detection core 2, an outer diameter of 0.2 is applied to each of the symmetric positions of the detection core 2.
The detection coil 3 is formed by winding a formal wire having a diameter of 0.5 mm on the outer periphery of the detection core 2 to form an exciting coil 5. Outside diameter of 8m inside the detection core 2
The detection conductor wire 1 made of m vinyl coating was penetrated.
Further, a formal wire having an outer diameter of 0.1 mm was wound around each of the cylindrical detection cores 2 at opposing positions for 10 turns to form modulation coils 43a and 43b.

As a DC current sensor according to the present invention, an AC current in which an oscillator or the like for generating an exciting current having a frequency twice as high as the exciting current finally applied to the exciting coil is arranged in each of the exciting coil 5 and the detecting coil 3. An application means, a phase comparison circuit, and the like are arranged, and f = 1 as an exciting current from the oscillator.
An alternating current of 8 kHz and 300 mA flows, and the modulation coil 4
A sine-wave alternating current of 100 Hz and 30 mA (at the peak) is passed through 3a and 43b, and ± 50 m
A detection coil 3 (3a, 3a in the figure) output via the phase comparison circuit when the DC current I is increased or decreased in the range A
3b, 3c, 3d) (electromotive force (output) V)
FIG. 22 shows an output change after removing a 100 Hz AC component from the _OUT with a low-pass filter. Note that the output voltage V _OUT is a value output via an amplifier circuit having _an amplification effect. From FIG. 22, according to the DC current sensor of the present invention, it is possible to detect the direction of the electromotive force (output) of the detection coil 3 based on the DC current flowing through the detected wire, that is, the DC current flowing through the detected wire. In addition to the absolute value of the current, the direction can be detected stably with good sensitivity, and a small current of about 10 mA
It is apparent that the measurement can be performed at a / N ratio of 10 times or more, the difference detection sensitivity does not decrease due to the magnitude of the reciprocating current, and the error output due to the reciprocating current is small.

[0058]

The direct current sensor according to the present invention has a modulation coil wound around a detection core so as to penetrate in the same direction as the conductor to be detected, and the detection is performed by an alternating magnetic field generated in the modulation coil. Since the residual magnetic flux in the core has been reduced,
Because it has excellent detection capability even for minute changes in current, when used in direct current leakage breakers, etc.
The required high-sensitivity detection can be achieved simply by penetrating the conductor to be detected, which is disposed in the detection core, without winding it around the core. The structure is relatively simple, and the DC current sensor can be downsized. . In addition, since it is possible to detect not only the absolute value of the DC current flowing through the detected wire, but also the direction of the DC current, a technique that requires control such as forward ← → reverse and forward ← → return depending on the direction of the DC current is required. In the field, for example, control of an actuator using a DC motor, it can be more effectively utilized.

[Brief description of the drawings]

FIG. 1 is a perspective explanatory view showing an outline of an embodiment of a DC current sensor according to the present invention.

FIG. 2 is a graph showing a relationship between an applied frequency and a frequency in the DC current sensor configuration of FIG. 1, where A is a frequency and an exciting current, B is a frequency and a magnetic flux passing through a detection core, C is a frequency and a detection coil. The relationship with the electromotive force is shown.

3 is a graph showing a relationship between an applied frequency in the DC current sensor configuration of FIG. 1, where A is the frequency and the exciting current, B is the frequency and the magnetic flux passing through the detection core, C is the frequency and the detection coil. The relationship with the electromotive force is shown.

FIG. 4A is a line graph showing a relationship between a detected current and an output in a very small area in a DC current sensor;
Is a line graph showing a BH curve (hysteresis curve) of the detection core.

FIGS. 5A and 5B show minor loops in which after a core is excited by applying a DC current to a detection target wire without applying a modulation AC current to a modulation coil, the DC current is cut off, and then an AC current is applied to the modulation coil. 6 is a line graph showing a state in which is formed.

FIG. 6 is a diagram showing a movement state of a center point of a minor loop when a modulation AC current is supplied to a modulation coil and a modulation AC current is superimposed on a current to be measured in a state where a DC current is flowing through a detection target wire; It is a graph.

FIG. 7 is an explanatory perspective view showing the outline of another embodiment of the direct current sensor of the present invention.

FIG. 8 is an explanatory plan view showing an outline of an embodiment of a core material for producing the direct current sensor of the present invention shown in FIG. 7;

FIG. 9 is a perspective explanatory view showing an outline of another embodiment of the direct current sensor of the present invention.

FIG. 10 is a perspective explanatory view showing an outline of another embodiment of the direct current sensor of the present invention.

11 is a partial explanatory view of the DC current sensor of the present invention shown in FIG.

12A and 12B are detailed explanatory diagrams of a magnetic path generated by an exciting coil of the DC current sensor of the present invention shown in FIG.

FIGS. 13A and 13B are detailed explanatory diagrams of magnetic paths generated by exciting coils of the DC current sensor of the present invention shown in FIG.

14 is a partial cross-sectional explanatory view illustrating an arrangement configuration of a high electrical conductivity metal foil for preventing capacitive coupling between an excitation coil and a detection coil in the DC current sensor of FIG. 9;

FIG. 15 is a perspective explanatory view showing an outline of another embodiment of the direct current sensor of the present invention.

FIG. 16 is a perspective explanatory view showing an outline of another embodiment of the direct current sensor of the present invention.

FIG. 17 is an explanatory perspective view showing an outline of another embodiment of the direct current sensor of the present invention.

FIG. 18 is an explanatory perspective view showing one embodiment of a shield case used in the DC current sensor of the present invention.

FIG. 19 is an explanatory diagram showing an outline of an embodiment of an electric circuit connected to the DC current sensor of the present invention.

FIG. 20 is a line graph showing a relationship between a DC current (a minute area) flowing through a detected conductor 1 and an output in the DC current sensor of the present invention.

FIG. 21 is a line graph showing a relationship between a DC current (ultra-micro area) flowing through a detected conductor 1 and an output in a DC current sensor of a comparative example.

FIG. 22 is a line graph showing a relationship between a DC current (a minute area) flowing through a detected conductor 1 and an output in the DC current sensor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor to be detected 2 Detecting core 3, 3a, 3b, 3c, 3d Detecting coil 4, 4a, 4b Exciting core 5 Exciting coil 6 Core orthogonal part 10 AC current applying means 11 OSC 12 T-FF 13, 31 LPF 14 Buffer amplifier Reference Signs List 20 phase comparison circuit 32 phase shifter 33 Schmitt trigger 51a, 51b shield case member 70 metal foil 71 slit portion 43, 43a, 43b modulation coil

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 15/18 H01F 38/20-38/40

Claims (4)

(57) [Claims] 1. A provided core orthogonal section perpendicular connecting the exciting core with respect to the circumferential direction of the detecting core in a portion of the detecting core consisting of an annular soft magnetic material, wherein an exciting core consisting of an annular soft magnetic material It consists of a detection core and a detection coil and an excitation coil, which are wound in a toroidal shape on each core, and the detection conductor through which a direct current for non-contact detection flows flows inside the detection core. And a modulation coil wound in the same direction as the conductor to be detected on the detection core, so that an alternating magnetic field generated in the modulation coil can be superimposed on the detection core. 2. A core orthogonal portion which is orthogonally connected to an exciting core in a circumferential direction of the detecting core at a part of a detecting core made of an annular soft magnetic material, and the exciting core made of an annular soft magnetic material and The detection core is integrally arranged, the detection coil is wound around the detection core in a toroidal shape, and the excitation coil wound around the detection core in the circumferential direction of the detection core is wound around the detection core. , A detection wire through which a direct current for non-contact detection flows passes through the inside of the detection core, a modulation coil wound in the same direction as the detection wire is disposed on the detection core, and an alternation generated in the modulation coil is provided. A direct current sensor characterized in that a magnetic field can be superimposed on the detection core. 3. A pair of cylinders serving as excitation cores are arranged in parallel with their axial center lines parallel to each other, and adjacent sides of the respective open ends of the parallel cylinders are connected and integrated by a connection plate made of a soft magnetic material. DC current sensor according to claim 1 or claim 2, wherein in that without the detecting core by the plate and the cylindrical side face connected thereto. 4. The method of claim 1 and one detection coil in coil, characterized in that the share function of the modulation coil or claim 2
DC current sensor as described.