JP3093529B2 - 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 used for a DC earth leakage breaker, etc., which has a relatively simple structure and has an excellent detection capability even for a minute change in current. It relates to a high-sensitivity DC current sensor.

[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 this method, an unbalance is generated at the time when the saturation is reached, and the change is detected by the detection coil.

The mag-amp system employs a configuration in which an exciting coil is wound around the core and an alternating current of a predetermined value is applied in order to apply a magnetic flux change in the core in advance. In the magnetic multivibrator system, a circuit connected to a detection coil is used. Self-excited oscillation by the action of the semiconductor or the like, and oscillates by changing the duty ratio of the oscillation waveform according to the current to be detected. Further, in the Hall element method, a detected wire is wound in a toroidal shape directly on a core of a soft magnetic material formed with a gap portion in which a Hall element is arranged, and a change in DC current flowing through the detected wire is obtained. This is configured to directly detect a change in magnetic flux in the core based on the Hall element.

[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 a high-sensitivity DC having excellent detection capability even for a DC leakage breaker or the like, especially even a minute change in current. The purpose is to provide a current sensor. Another object of the present invention is to provide a DC current sensor capable of reducing the hysteresis of output characteristics and improving the detection sensitivity in a minute current region.

[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. For example, as means for periodically forming a magnetic gap in a part of the detection core, a magnetic flux generated in the detection core in a direction substantially orthogonal to a circumferential magnetic flux generated in the detection core by a DC current flowing through the detected wire. It is possible to employ a configuration in which a part of the detection core is magnetically saturated by the generated magnetic flux and the magnetic path by the circumferential magnetic flux is periodically interrupted.

One of the basic constitutions of the DC current sensor proposed in the present invention is that an exciting core is provided in a part of a detecting core made of an annular soft magnetic material in a circumferential direction of the detecting core.
Provided core intersection which intersects connected, and the detecting core and the exciting core consisting of an annular soft magnetic material integrally disposed, were placed detecting coil and the exciting coil wound in a toroidal shape to each core There is a DC current sensor having a configuration in which a detection target wire through which a DC current for non-contact detection flows flows through the inside of the detection core. In particular, in the above configuration, the exciting core can be excited in a direction perpendicular to the circumferential direction of the detecting core, and the exciting core periodically connects a core orthogonal portion that is orthogonally connected to the detecting core in the circumferential direction of the detecting core. Means for applying AC current to the exciting coil that saturates the magnetic flux generated in the detection core based on the DC current flowing through the conductor to be detected during excitation. Electric power can be output to detect a direct current flowing through the detected conductor.

In other words, the direct current sensor of the present invention for detecting the direct current flowing through the detected conductor in a non-contact manner is provided with a detection core made of an annular soft magnetic material having the detected conductor penetrating therethrough. And a detection coil wound in a toroidal shape, and an excitation core made of a soft magnetic material that is connected to a part of the detection core in a direction perpendicular to the circumferential direction of the detection core to form an annular shape is integrally disposed. A DC current sensor is formed by winding an exciting coil around the exciting core in a toroidal manner, and applying an AC current to the exciting coil causes the exciting core to move in the circumferential direction of the detection core. The magnetic flux generated in the detection core based on the DC current flowing through the wire to be detected is changed by exciting in a perpendicular direction and periodically magnetically saturating the orthogonal portion between the detection core and the excitation core. And by outputting the electromotive force of twice the frequency of the excitation current in the detection coil is made of a configuration for detecting a DC current flowing through the lead wire being detected.

[0015]

The operation of the DC current sensor according to the present invention will be described below in detail with reference to the drawings. FIG. 1A is a perspective explanatory view showing an outline of an embodiment of a DC current sensor of the present invention, and FIG. 1B is a partial sectional explanatory view thereof. 2 and 3 show the relationship between the exciting current, the magnetic flux passing through the detection core, and the electromotive force generated in the detection core in this configuration. In FIG. 1, reference numeral 1 denotes a detection target wire penetratingly disposed inside a detection core 2 made of an annular soft magnetic material. 3
Is a detection coil wound in a toroidal shape at a predetermined position of the detection core 2, which is electrically insulated from the detection target wire 1 and is connected to a predetermined detection circuit (not shown). Reference numeral 4 denotes an excitation core made of an annular soft magnetic material, and an excitation coil 5 wound in a toroidal shape is disposed at a predetermined position. In addition, the exciting core 4 is connected to a part of the detecting core 2 in the circumferential direction in a direction perpendicular to the circumferential direction of the detecting core 2. And a magnetically saturated portion is formed in the core orthogonal portion 6 of the exciting core 4.

In the configuration shown in FIG. 1, when a DC current I flows through the detected conductor 1, a magnetic field clockwise in the direction of the DC current I is generated in the detection core 2, and a magnetic flux Φ ₀ is generated in the detection core. Occur. 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 portion 6 (shaded portion in the figure), which is a part in the circumferential direction of 2, has a reduced relative magnetic permeability μ, and becomes a so-called substantial magnetic gap extremely close to 1, resulting in a magnetic flux Φ ₀ in the detection core.
To Φ ₁ . Here, when an alternating current flowing through the exciting coil 5 is set to a frequency f ₀ and the exciting core 4 is saturated near a peak value of the current, the direct current I flowing through the detected conducting wire 1 becomes as shown in FIG. In the case of the plus (+) direction (upward in the figure), the DC current I flowing through the detected wire 1 is in the minus (-) direction (downward in the figure) as shown in FIG. The excitation core 4 is saturated twice. As shown in FIG. 2, when the DC current I flowing through the detected conductor 1 is in a positive (+) direction (upward in the drawing), the saturation causes the DC current I generated in the detection core 2 and flowing through the detected conductor 1. Generated magnetic flux Φ
₀ 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.

Further, as shown in FIG. 3, the DC current I flowing through the conductor 1 to be detected is negative (-) (downward in the figure).
In this case, the operation is substantially the same as that in the case where the DC current I is in the plus (+) direction (upward in the figure).
Are opposite, the direction of the magnetic flux generated in the detection core 2 is also opposite, and the phases of the voltage V _DET of the frequency 2f ₀ generated in the detection coil 3 are different from each other by 180 degrees. However, regardless of the direction of the DC current I flowing through the lead wire being detected 1, a magnetic flux in both cases [Phi ₀ alpha DC current I, voltage V _DET from the relationship between the voltage V _DET alpha flux [Phi ₀
(4) The DC current I is generated, and an electromotive force proportional to the DC current I flowing through the detected wire 1 can be detected by the detection coil 3, and the absolute value of the DC current I flowing through the detected wire 1 can be known.

Further, since the detecting core 2 and the exciting core 4 are connected at right angles to each other, basically, the exciting magnetic flux in the exciting core 4 does not leak to the detecting core 2 side, and the detecting coil 3, the detection coil 3
Does not generate an electromotive force due to the exciting current applied to the exciting coil 5, and the DC current I = 0 flowing through the conductive wire 1 to be detected.
At this time, V _DET = 0. The frequency of the electromotive force V _DET generated in the detection coil 3 is 2f ₀ ,
Is different from the frequency f _{0 of the} excitation current applied to the detection coil 3, the excitation magnetic flux in the excitation core 4 is leaked and detected by the detection coil 3 due to the accuracy of the shape and dimensions of the detection core 2 and the excitation core 4. Since the frequency of the leak component is f ₀ , the leak component can be easily separated by a frequency discriminating filter or the like, so that it has been confirmed that the leak component can be used as a highly sensitive DC current sensor.

Further, the present inventors have studied the miniaturization of the DC current sensor shown in FIG.
The present invention also proposes a DC current sensor having a configuration in which only the orthogonal portion of the above is magnetically saturated and the exciting core 4 other than the orthogonal portion is magnetically unsaturated. That is, when the width W of the excitation core 4 is fixed as shown in FIG. 4, the magnetic core 4 is required to magnetically saturate an orthogonal portion between the detection core 2 and the excitation core 4, a so-called hatched portion 6 in the drawing. It is necessary to saturate the whole, and the exciting current becomes large, the exciting circuit becomes large, and heat generation due to the core loss (iron loss) of the exciting core 4 becomes large, which may cause a temperature drift of the output of the detection coil 3 and the like. Is done. The arrows in the figure schematically show the distribution state of the magnetic flux. Therefore, the present inventor proposes a configuration in which only the core orthogonal portion 6 between the detection core 2 and the excitation core 4 is magnetically saturated by various configurations as shown in FIGS.

FIG. 5 shows a configuration of the detection core 2 on the excitation core 4 side.
The cross-sectional area of the connecting portion is reduced by narrowing the plate width of the connecting portion, so that only the core orthogonal portion 6 in the hatched portion in the drawing is magnetically saturated and the other portions are not saturated. The arrows in the figure schematically show the distribution state of the magnetic flux as in FIG. 4, and the core orthogonal part 6 has a large magnetic flux density and is magnetically saturated as in FIG. The other portions indicate that the magnetic flux density is small and not saturated, that is, it is not saturated. In the configuration of FIG. 6, a plurality of through-holes 7 having a predetermined inner diameter are provided in a core orthogonal portion 6 indicated by oblique lines in the figure, and the cross-sectional area of the core orthogonal portion 6 in a direction perpendicular to the circumferential direction of the detection core 2 is partially reduced. FIG. 5
The same effect as the configuration described above can be obtained. A, B in FIG.
5 has a substantially same effect as the configuration shown in FIG. 5 by fixing an annular soft magnetic material 8 inside the excitation core 4 except for the core orthogonal portion 6 and changing the thickness of the excitation core 4. Obtainable. The configuration of A and B in FIG.
The purpose of the present invention is to obtain substantially the same effect as the configuration shown in FIG.
A material having a relatively low saturation magnetic flux density Bs (the detection core 2 side) is pressed in a striped shape in advance to the center of a thin plate of a material having a high saturation magnetic flux density Bs (the excitation core 4 side) in a striped manner, for example, by punching from a clad material. A cross-shaped core material as shown in FIG. A similar effect can be obtained by partially pressing a material having a lower saturation magnetic flux density Bs than other portions only in the orthogonal portion between the detection core 2 and the excitation core 4. In any of the configurations described above, only the core orthogonal portion 6 between the detection core 2 and the excitation core 4 is magnetically saturated, and the other portion of the excitation core 4 is unsaturated, so that the unsaturated portion is Core loss (iron loss) can be reduced.

Therefore, in the configurations shown in FIGS. 5 to 8, the excitation current applied to the excitation coil 5 can be reduced as compared with the configuration shown in FIG. 4, and the configuration of the excitation circuit can be simplified and the size can be reduced. . That is, the power consumption of the entire sensor can be reduced, and the range of application to small devices and the like is widened. Further, since the temperature rise in the excitation 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 of the detection coil 3 can be reduced, and the stability of detection accuracy as a sensor is improved.

The present invention proposes a further improved direct current sensor. In the DC current sensor having the above-described configuration, a study was conducted to enable detection of a very small current. As a result, permalloy C (78% Ni-5Mo-4Cu-balFe) known as a high magnetic permeability material was used as the detection core 2.
Is used, the DC current flowing through the detection target wire 1 is, for example, ± 5.
In a minute current region of about 0 mA or less, a so-called hysteresis phenomenon occurs in which the output voltage (electromotive force) of the detection coil differs, even when the DC current increases or decreases, even when the DC current increases or decreases. In the vicinity (± 20 mA), it was confirmed that a “reverse region” in which the output voltage decreased with an increase in the DC current occurred. Due to the occurrence of the reverse region, the reference level at the time of measurement fluctuates, and in the measurement in the minute current region, the measured value is different each time, and an inconvenience that an accurate value cannot be obtained occurs. Above "reversal area"
Is considered to be caused by the coercive force of the soft magnetic material constituting the detection core 2. To reduce this effect, it is necessary to reduce the radius r of the detection core 2 (see FIG. 1B). However, it is not preferable because the outer diameter of the conductor to be detected and the number of through conductors are limited.

The inventor has made further improvements to the DC current sensor having the above-described structure, and in particular, has increased the width d (see FIG. 1B) of the connection portion of the excitation core 4 connected to the detection core 2 to detect the current. The ratio of the width of the connecting portion of the exciting core 4 to the magnetic path length of the core 2 is increased.
By reducing the residual magnetic flux density of the excitation core 5 and winding the excitation coil 5 for generating a magnetic flux in a predetermined direction on the excitation core 4 around the detection core 2 in the circumferential direction of the detection core 2,
The configuration also has the demagnetizing effect of the detection core 2 by the exciting coil 5, and it is possible to provide a DC current sensor in which the occurrence of the "reverse rotation region" is significantly reduced. That is,
The present invention provides an exciting core made of an annular soft magnetic material , wherein a core intersecting portion that cross-connects with an exciting core in a circumferential direction of the detecting core is provided on a part of the sensing core made of an annular soft magnetic material. A core is integrally disposed, a detection coil is wound around the detection core in a toroidal shape, and an excitation coil wound around the detection core in the circumferential direction of the detection core is arranged around the detection core, Further, the DC current sensor has a configuration in which a detection conducting wire through which a DC current for non-contact detection flows is penetrated inside the detection core.

In particular, in the above configuration, the exciting core can be excited in a direction perpendicular to the circumferential direction of the detecting core, and the exciting core has a period perpendicular to the core orthogonally connected to the detecting core in the circumferential direction of the detecting core. Means for applying an alternating current to the exciting coil that magnetically saturates the magnetic field, and the magnetic flux generated in the detecting core can be modulated based on the direct current flowing through the wire to be detected during excitation. The DC current flowing through the conductor to be detected can be detected by outputting an electromotive force having a frequency of. In other words, the direct current sensor according to the present invention, which detects the direct current flowing through the detected conductor in a non-contact manner, includes a detecting coil made of an annular soft magnetic material having the detected conductor penetrating therethrough. Is wound in a toroidal shape, and an excitation core made of a soft magnetic material that is connected to a direction perpendicular to the circumferential direction of the detection core and forms an annular shape is arranged integrally with a part of the detection core. A DC current sensor is formed by winding an excitation coil wound in the circumferential direction of the detection core on the outer periphery of the detection core, and the excitation core is formed by applying an AC current to the excitation coil. The magnetic flux generated in the detection core based on the DC current flowing through the wire to be detected is excited by exciting in a direction perpendicular to the circumferential direction and periodically magnetically saturating an orthogonal portion between the detection core and the excitation core. Tone, and by outputting the electromotive force of twice the frequency of the excitation current in the detection coil is made of a configuration for detecting a DC current flowing through the lead wire being detected.

The DC current sensor according to the present invention having the above configuration will be described in detail with reference to FIG. FIG. 10 is a perspective explanatory view showing an outline of a DC current sensor having another basic configuration of the present invention. In FIG. 10, reference numeral 1 denotes a conductor to be detected, which is penetrated inside a detection core 2 made of a soft magnetic material having a substantially elliptical ring shape. Reference numeral 3 denotes a detection coil, which is wound around the detection core 2 in a toroidal shape. Reference numeral 4 denotes an excitation core made of a soft magnetic material that is connected to a part of the detection core 2 in a direction perpendicular to the circumferential direction of the detection core 2 to form a substantially elliptical ring and to be integrally disposed. In this configuration, by increasing the width d of the connection portion of the excitation core 4 connected to the detection core 2, the width d of the core orthogonal portion 6 of the excitation core 4 with respect to the magnetic path length of the detection core 2 as compared with the configuration shown in FIG. To increase the ratio. In the configuration shown in FIG. 1, the excitation coil 5 is wound around the excitation core 4 in a toroidal shape. However, in the configuration of the present invention, as shown in FIG. It is wound around.

In such a configuration, when a DC current I flows through the conductive wire 1 to be detected, a magnetic field clockwise in the direction of the DC current I is generated in the detection core 2, and a magnetic flux Φ ₀ is generated in the detection core 2. Occurs. 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 2 is a so-called substantial magnetic gap whose relative magnetic permeability μ is extremely close to 1, and the magnetic flux Φ ₀ in the detection core is changed to Φ _1.
Reduce to. Here, when the alternating current flowing through the exciting coil 5 is set to the frequency f ₀ and the exciting core 4 is saturated near the peak value of the current, the detection coil of the DC current sensor having the configuration of FIG. By the same mechanism as that for generating electromotive force to
The voltage V _{DET of} f ₀ is generated in the detection coil 3. Further, as described above, by increasing the width d of the core orthogonal portion 6 of the excitation core 4 connected to the detection core 2, the core orthogonal portion 6 of the excitation core 4 with respect to the magnetic path length of the detection core 2 is increased.
Are increased, the ratio of the magnetic gap is increased, and the detection core 2
Thus, the occurrence of the "reverse rotation region" can be greatly reduced by the demagnetizing effect of the exciting coil wound around the outer periphery of the detection core 2.

By further improving the basic configuration of the present invention shown in FIGS. 1 and 10, electromagnetic imbalance and the like can be reduced, and noise can be reduced and the S / N ratio can be improved. be able to. In particular, the other embodiments of the present invention shown in FIGS. 11, 13, 14, 18, and 19 have the above-mentioned effects and have an effective configuration capable of realizing stable measurement. That is, in the basic configuration of the present invention shown in FIGS. 1 and 10, the number of the excitation cores 4 connected to the detection core 2 is one, and the position of the detection coil 3 is one. Although the electromagnetic balance of the current sensor is difficult to achieve, the configuration considering the electromagnetic balance arrangement of the excitation core 4 and the detection coil 3 is the configuration described with reference to FIGS.

In FIG. 11, reference numeral 1 denotes a lead to be detected;
It is disposed so as to penetrate the inside 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. 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. 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. In such a configuration, when the DC current I flows through the detected conductor 1,
A magnetic field clockwise with respect to the direction of the DC current I is generated in the detection core 2, and a 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 periodically generate a magnetic flux that changes in the α direction in the pair of exciting cores 4a and 4b, and the exciting cores 4a and 4b are periodically cycled. When magnetically saturated, the core orthogonal portion 6 on the long side, which is a part of the rectangular frame-shaped detection core 2 in the circumferential direction, has a relative magnetic permeability μ of extremely 1
, And reduces the magnetic flux Φ ₀ in the detection core to Φ ₁ .

Therefore, also in the DC current sensor of the present invention 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 between the excitation cores 4a and 4b connected to the detection core 2 is substantially twice (2L) the dimension L in the length direction of the sensor in the drawing. The ratio of the width d of the connection portion of the excitation core 4 to the magnetic path length of the magnetic core 2 becomes extremely large, and 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 of FIG. , The hysteresis phenomenon caused by the coercive force can be reduced. In addition, since the overall configuration of the DC current sensor is symmetrical with respect to the detection target wire 1, it is possible to achieve stable electromagnetic measurement with good electromagnetic balance. Detection core 2 and excitation core 4 constituting the above-described DC current sensor
a and 4b denote plate members made of a predetermined soft magnetic material as shown in FIG.
2, it can be easily obtained as an integrated product by assembling by bending at the broken line portion in the figure and spot welding at the hatched portion.

FIG. 13 shows another embodiment, in which a pair of detection coils 3a, 3b are wound in a toroidal shape around the outer circumference of a pair of excitation cores 4a, 4b together with the excitation coils 5a, 5b. It has a configuration similar to that of FIG. 11, and it is possible to detect a DC current flowing through the detection target wire 1 by a mechanism basically similar to that of FIG. FIG. 14 also shows another embodiment, in which a pair of exciting coils 5a and 5b are
A pair of excitation cores 4 arranged to form a square tube
1 and 4b, except that they are wound in a toroidal shape around the exciting coil winding bars 8a and 8b formed at the inner central portions of the insides of FIGS.
3 and a mechanism similar to that of FIG. 1 can detect a DC current flowing through the conductive wire 1 to be detected. In particular, in the configuration shown in FIG. 14, the excitation cores 4a and 4b are formed in advance into an E-shaped cross section as shown in FIG. 15, so that the excitation core wound in advance on the bobbin 9 having a predetermined shape and dimensions. Coil 5a, 5b
Is inserted into the exciting coil winding bars 8a and 8b, and then integrated with a rectangular frame-shaped detection core by a predetermined means, thereby making it easy to manufacture. Further, in the configuration of FIG. 13, the magnetic flux generated in the pair of excitation coils 5a and 5b leaks to the outside of the excitation cores 4a and 4b, and the leakage magnetic flux causes an excitation signal to be mixed into the detection coils 3a and 3b. When detecting a current, the level of the mixed signal becomes higher than the detection signal, which may cause a reduction in sensitivity. However, in the configuration shown in FIG. 14, the magnetic fluxes generated in the excitation coils 5a and 5b operate efficiently without leaking to the outside of the excitation cores 4a and 4b.
The adverse effects on a and 3b are 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. 13 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.
As shown in FIGS. 17A and 17B, the magnetic paths of the two circuits basically act via the exciting coil winding bars 8a and 8b such that the directions of the magnetic fluxes alternately change. The electromagnetic balance is further improved. In adopting the configuration of FIG. 14, since the magnetic flux concentrates on the exciting coil winding bars 8a, 8b, the thickness of the exciting coil winding bars 8a, 8b is about twice as thick as the other portions in advance. It is desirable to set.

In the configuration shown in FIG. 13, in order to prevent the excitation signals from being mixed into the detection coils 3a and 3b due to the capacitive coupling between the excitation coils 5a and 5b and the detection coils 3a and 3b, for example, It is preferable to interpose a metal foil (not shown) having high electrical conductivity, such as Ca or Al, which is electrically grounded, between the detection coils 3a, 3b and the detection coils 3a, 3b. That is, the exciting coils 5a, 5a
The outer periphery of b is secured with electrical insulation,
The detection coils 3a and 3b are wound while winding and covering the metal foil and ensuring electrical insulation around the metal foil. However, it is necessary that the metal foil is electrically cut at least at one position in the winding direction. By adopting such a configuration, detection with higher accuracy is possible.

An embodiment in which the basic configuration of FIG. 10 is improved to obtain the same effect as the DC current sensor having the above configuration will be described with reference to perspective explanatory views of FIGS. 18 and 19. In FIG. 18, 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. Also,
A pair of exciting cores 4 are provided on the long sides at the opposing positions.
a and 4b are integrally arranged 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 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. It is wound in a toroidal shape, and the exciting coil 5 is wound around the outer periphery of the detection core 2.

In such a configuration, 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, and a magnetic flux Φ ₀ is generated in the detection core 2. Occurs. At this time, a predetermined alternating current is applied to the exciting coil 5 to generate a magnetic flux that periodically changes in the α direction in the pair of exciting cores 4a, 4b, and the exciting cores 4a, 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, in the DC current sensor of the present invention shown in FIG. 18, 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. 10, 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 and 4b connected to the detection core 2 is twice (2L) the dimension L in the length direction of the sensor in the figure, and therefore the magnetic field of the detection core 2 is changed. The ratio of the width d of the connecting portion of the exciting core 4 to the path length becomes extremely large, and the residual magnetic flux density in the detecting core 2 due to the effect of the demagnetizing field is further reduced.
The occurrence of the "reverse region" can be greatly reduced. In addition, since the overall configuration of the DC current sensor is symmetrical with respect to the detection target wire 1, it is possible to achieve stable electromagnetic measurement with good electromagnetic balance.

FIG. 19 is also a perspective explanatory view showing a DC current sensor according to an embodiment of the present invention in which the basic configuration of FIG. 10 is improved. In particular, the DC current sensor can be downsized compared to other embodiments. is there. Although the direct current sensor shown in FIG. 19 is basically the same as the configuration shown in FIGS. 10 and 18, the cylindrical core is orthogonal to the opening direction of the 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. Are four places),
The detection coils 3a, 3b, 3c, and 3d are respectively wound in a toroidal shape, and the exciting coil 5 is wound around the detection core 2, and a detection target wire penetrating into the cylindrical detection core 2. 1 are arranged to form a DC current sensor.

In the DC current sensor according to the present invention comprising the above-described FIGS. 1 and 10 and a number of embodiments having the basic configuration, the orthogonal portion 6 between the detection core 2 and the excitation core 4 is provided. The configuration is such that a magnetic gap is formed by periodically magnetically saturating, and a minute current change can be detected with high sensitivity. As described above, the DC current sensor according to the present invention is configured by effectively disposing an annular soft magnetic material as the detection core and the excitation core. 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 present invention, the annular soft magnetic material is not limited to the soft magnetic material having a so-called ring shape, but is connected so that the soft magnetic material can form an electromagnetic closed circuit. Various configurations such as an oval ring shape, a rectangular frame shape, and the like can be adopted in addition to the ring shape as shown in the drawing.

Further, the magnetic gap formed in the detection core is not limited to one location in the detection core, but may be a plurality of locations. As shown in the various embodiments described above, It is desirable to set the formation location in consideration of a natural balance. In the DC current sensor according to the present invention based on FIG. 1 or FIG. 10 and their configurations, the magnetic saturation at the core intersection of the detection core and the excitation core is complete without orthogonality, for example. The object of the present invention can be achieved if the state can be substantially saturated without achieving the saturation. 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.

Furthermore, in the present invention, the number of conductors to be detected penetrating the detection core is not limited to one, and a plurality of conductors may be penetrated according to the required size of the sensor. By using only one conductor, the effect of the present invention can be exhibited most effectively. When these DC current sensors are incorporated in an inverter device and used, it is particularly effective to insert a noise filter in the power supply line of the detection circuit in order to prevent switching noise from being mixed. As shown in FIG. 20, a DC current sensor of the present invention having various configurations is connected to a shield case made of permalloy, a non-oriented silicon steel plate or the like (51a is a case body, 51b, 51c).
Is a case lid) to prevent the intrusion of induction noise. According to the DC current sensor of the present invention, a magnetic gap is generated periodically in a part of the detection core by a magnetic flux generated in a substantially orthogonal direction with respect to a magnetic flux generated in a circumferential direction of the detection core by a DC current flowing through the detected wire. Is not limited to the embodiment described above, and various configurations can be selected according to required characteristics and the like.

[0039]

【Example】

Example 1 Permalloy C (78% Ni-5% Mo-4% Cu-ba
A cross-shaped core material having the shape shown in FIG. 9 was obtained by punching a thin plate made of 1Fe) having a thickness of 0.2 mm. Where L
₁ = 75 mm, L ₂ = 50 mm, W ₁ = 10 mm, W ₂ = 1
3 mm. Each end of the core material was overlapped by 10 mm and integrated by spot welding to assemble into the configuration shown in FIG. Furthermore, 1100 ° C. × 3 h in a hydrogen gas atmosphere
r, heat treatment at 600 ° C. to 400 ° C. for 10 hours.
Complete the heat treatment of performing multi-stage cooling at 0 ° C./hr,
The DC current sensor of the present invention was obtained. After the small diameter side (about 12.5 mm diameter) of the pair of annular cores is used as the detection core 2 and the large diameter side (about 20 mm diameter) is used as the excitation core 4, an insulating protective vinyl tape is wound around each of these cores. A formal wire having an outer diameter of 0.2 mm is wound around the detecting core 2 for 40 turns to form a detecting coil 3, and the exciting core 4 has an outer diameter of 0.5 m.
The excitation coil 5 was formed by winding a formal wire having a length of 20 m for 20 turns. Further, a detection target wire 1 made of vinyl coating having an outer diameter of 9.0 mm was disposed inside the detection core 2. F = 10 kHz, 50
When an alternating current of 0 mA was applied, when a direct current was not supplied to the detection target wire 1, an output of V _DET = 10 mV was detected in the detection coil 3. When a direct current I of 50 mA was passed through the conducting wire 1, an output of V _DET = 60 mV was detected in the detection coil 3, confirming that the direct current sensor of the present invention was excellent in practicality.

Embodiment 2 In the DC current sensor according to Embodiment 1, ±
FIG. 21 shows a change in the electromotive force (output) V _DET output to the detection coil when the DC current I is increased or decreased in the range of 100 mA.

Third Embodiment In the DC current sensor of the first embodiment, the width of the exciting core 4 is the same as that of the connection portion with the detection core 2 (10 mm), and the width of the other portions is 15 mm, as shown in FIG. However, the exciting current applied to the exciting coil 5 is f = 10
An output similar to that of Example 1 was detected even with an alternating current of 300 mA at kHz. That is, only the orthogonal portion between the detection core 2 and the excitation core 4 is magnetically saturated so that the other excitation cores 4
It was confirmed that it was possible to reduce the exciting current by making the portion unsaturated.

Example 4 Permalloy C (78% Ni-5% Mo-4% Cu-ba
1Fe) is punched out of a thin plate having a thickness of 0.1 mm into a shape shown in FIG. 12, bent at a broken line in the figure, and assembled by spot welding at a hatched portion to form a core assembly constituting a DC current sensor shown in FIG. 18. Obtained. However, L = 25 mm, H
= 10 mm, W ₁ = 30 mm, and W ₂ = 10 mm. After the above assembly was subjected to a heat treatment at 1100 ° C. × 3 hr in a hydrogen gas atmosphere, the temperature was changed from 600 ° C. to 400 ° C. to 100 ° C.
At / hr, the heat treatment for performing the multi-stage cooling treatment was completed to obtain the DC current sensor of the present invention. After winding an insulating protective vinyl tape around a required position of the detection core 2, a formal wire having an outer diameter of 0.2 mm is wound around each short side of the detection core 2 by 20 turns to form detection coils 3a and 3b. Further, a formal wire having an outer diameter of 0.5 mm was wound around the outer periphery 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. When an alternating current of f = 9 kHz and 300 mA was applied as an exciting current to the exciting coil 5, when a direct current was not passed through the detection target wire 1, it is considered that this was caused by residual noise. 3
The output of V _DET = 3 mV of each sum) of a and 3b is detected, when the lead wire being detected 1 was supplied a direct current I of 50mA, the output of V _DET = 40 mV is detected in the detection coil 3 Thus, it was confirmed that the DC current sensor of the present invention was excellent in practicality.

Fifth Embodiment In the DC current sensor of the fourth embodiment, ± 1
FIG. 22 shows the change in the electromotive force (output) V _DET output to the detection coil 3 (the total value of each of 3a and 3b in the figure) when the DC current I is increased or decreased in the range of 100 mA and flowed. From FIG. 22, it has been confirmed that even in a small area where the DC current flowing through the conductive wire 1 to be detected is small, there is no phenomenon that the output decreases as the current increases (“generation of reverse area”), and stable measurement can be realized. In particular, when compared with the change in the electromotive force (output) V _DET shown in the second embodiment (see FIG. 21), the effect becomes more clear.

[0044]

The DC current sensor according to the present invention has an excellent detection capability even for a small change in current. Therefore, when the DC current sensor is used for a DC earth leakage breaker or the like, it is penetrated into the detection core. The required high-sensitivity detection can be achieved simply by penetrating the conductor to be detected without winding it around the core, the structure is relatively simple, and the DC current sensor can be downsized. In particular, in the configuration in which the exciting coil is wound in the circumferential direction of the detection core, even when the DC current flowing through the detection target wire 1 is in a very small area, there is no phenomenon that the output decreases as the current increases (“generation of reverse rotation area”). , Stable measurement can be realized.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a basic structure of a DC current sensor according to the present invention, and FIG.

FIG. 2 is a graph showing the relationship between the frequency of the excitation power applied to the excitation core, the magnetic flux passing through the detection core, and the electromotive force of the detection coil in the DC current sensor configuration of the present invention shown in FIG. B represents the temporal displacement of the exciting current, B represents the temporal displacement of the magnetic flux passing through the detecting core, and C represents the relationship between the electromotive force of the detecting coil and the temporal displacement.

FIG. 3 is a graph showing the relationship between the frequency of the excitation power applied to the excitation core, the magnetic flux passing through the detection core, and the electromotive force of the detection coil in the DC current sensor configuration of the present invention shown in FIG. B represents the temporal displacement of the exciting current, B represents the temporal displacement of the magnetic flux passing through the detecting core, and C represents the relationship between the electromotive force of the detecting coil and the temporal displacement.

FIG. 4 is a partial detailed view illustrating an outline of a configuration in which only a core orthogonal portion between a detection core and an excitation core is magnetically saturated in the DC current sensor configuration of the present invention illustrated in FIG. 1;

FIG. 5 schematically shows a configuration of the DC current sensor according to the present invention shown in FIG. 1 in which the width of the core orthogonal to the excitation core is narrowed in order to magnetically saturate only the core orthogonal to the detection core and the excitation core. FIG.

FIG. 6 outlines a configuration in which a hole is provided in the core orthogonal portion in order to magnetically saturate only the core orthogonal portion between the detection core and the excitation core in the DC current sensor configuration of the present invention shown in FIG. FIG.

FIG. 7 is a partial plan view illustrating an outline of a configuration in which only a core orthogonal portion between a detection core and an excitation core is magnetically saturated in the DC current sensor configuration of the present invention shown in FIG. 1;
B is a sectional view taken along the line BB.

8 is a partial plan view illustrating an outline of a configuration in which only a core orthogonal portion between a detection core and an excitation core is magnetically saturated in the DC current sensor configuration of the present invention illustrated in FIG. 1;
B is a sectional view taken along the line BB of FIG.

FIG. 9 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. 1;

FIG. 10 is a perspective explanatory view showing another basic structure of the direct current sensor of the present invention.

FIG. 11 is a perspective explanatory view showing another embodiment of the direct current sensor of the present invention.

12 is a development explanatory view for obtaining a core assembly in the DC current sensor configuration of the present invention shown in FIG. 11;

FIG. 13 is a perspective explanatory view showing another embodiment of the direct current sensor of the present invention.

FIG. 14 is a perspective explanatory view showing another embodiment of the direct current sensor of the present invention.

FIG. 15 is a partial explanatory view of the DC current sensor of the present invention shown in FIG.

FIGS. 16A and 16B are detailed illustrations of a magnetic path generated by an exciting coil of the DC current sensor of the present invention shown in FIG.

17A and 17B 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.

FIG. 18 is an explanatory perspective view showing another embodiment of the direct current sensor of the present invention.

FIG. 19 is a perspective explanatory view showing another embodiment of the direct current sensor of the present invention.

FIG. 20 is a perspective explanatory view showing another embodiment of the direct current sensor of the present invention.

FIG. 21 is a line graph showing a relationship between a DC current flowing through a detected conductor 1 and an output in the DC current sensor of the present invention shown in FIG.

FIG. 22 is a line graph showing a relationship between a DC current flowing through a detected conductor 1 and an output in the DC current sensor of the present invention shown in FIG. 18;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 detected conductor 2 detection core 3, 3 a, 3 b, 3 c, 3 d detection coil 4, 4 a, 4 b excitation core 5, 5 a, 5 b excitation coil 6 core orthogonal part 7 through hole 8 soft magnetic material 8 a, 8 b excitation coil winding Bar 9 for bobbin 51a Case body 51b, 51c Case lid

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

Claims (5)

(57) [Claims] 1. A detection conductor, comprising: a detection core made of an annular soft magnetic material; and a detection coil wound in a toroidal shape on the detection core, wherein a direct current for non-contact detection flows inside the detection core. In a DC current sensor, a magnetic flux is generated periodically in a part of the detection core by a magnetic flux generated in a substantially orthogonal direction with respect to a circumferential magnetic flux generated in the detection core by a DC current flowing through the detection target wire. DC current sensor having means for forming a specific gap. 2. A means for periodically forming a magnetic gap in a part of a detection core is provided in a direction substantially orthogonal to a circumferential magnetic flux generated in the detection core by a DC current flowing through a detected wire. 2. The DC current sensor according to claim 1, wherein the DC current sensor has a configuration in which a part of the detection core is magnetically saturated by the magnetic flux generated in the magnetic field, and a magnetic path due to the circumferential magnetic flux is periodically interrupted. 3. A provided a core intersection which intersects connecting the exciting core with respect to the circumferential direction of the part to the detecting core 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. 3. The direct current sensor according to claim 2, having a configuration as described above. 4. A provided a core intersection which intersects connecting the exciting core with respect to the circumferential direction of the part to the detecting core of the detecting core consisting of an annular soft magnetic material, wherein an exciting core consisting of an annular soft magnetic material 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. 3. The direct current sensor according to claim 2, wherein a detection conductor through which a direct current for contactless detection flows flows through the inside of the detection core. 5. An exciting core is capable of being excited in a direction perpendicular to a circumferential direction of a detecting core, and the exciting core periodically and magnetically forms a core orthogonal portion orthogonally connected to the detecting core in a circumferential direction of the detecting core. It has a means for applying AC current to the exciting coil to saturate, and it can modulate the magnetic flux generated in the detection core based on the DC current flowing through the conductor to be detected at the time of excitation. 5. The DC current sensor according to claim 3, wherein the DC current sensor has a configuration of outputting a DC current and detecting a DC current flowing through the conductive wire to be detected.