JPH112646A - Direct current sensor and method for preventing flowing-out of direct current - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a direct current sensor which can measure a very small direct current mixed in an alternating current flowing through a conductor to be detected for forming a transformerless type inverter which can substantially prevent the flowing-out of the direct current in a non-contacting state by detecting the direct current which flows in and is mixed with the alternating current on the output side of the inverter and making the direct current zero by applying negative feedback based on the detected data. SOLUTION: A direct current sensor is composed of a direct current component detecting core 10 consisting of an annular soft magnetic material around which an exciting coil 11 and a direct current detecting coil 12 through which a conductor to be detected is arranged are wound in toroidal coil-like states and an alternating current component detecting core 20 constituting of an annular soft magnetic material around which an alternating current detecting coil 21 is wound. In addition, the direct current sensor is provided with a coil 22 for feedback current which is extendedly wound around the cores 10 and 20 and through which a feedback current is made to flow so that the electromotive force generated in the coil 21 by the alternating current may become zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct current mixed in an alternating current, which is used in the field of facilities for converting a direct current into an alternating current, such as a photovoltaic power generation system, an uninterruptible power supply, and various home appliances. Related to DC current sensors that detect current, in particular, a DC current sensor that has a relatively simple structure and can detect minute DC current with high sensitivity and uses it to prevent DC current from flowing into AC current The present invention relates to a method for preventing a direct current from flowing out.

[0002]

2. Description of the Related Art Conventionally, in a device such as a photovoltaic power generation system or an uninterruptible power supply, a direct current is converted into an alternating current through an inverter. When current flows out and direct current flows into electrical equipment using an AC power supply used on the load side, the inductance of the power transformer, reactor, motor, etc. built in the equipment decreases due to DC bias, and overcurrent occurs In this case, a transformer is disposed on the output side of the inverter in order to cause a problem such as burning due to the flow of heat.

However, in this configuration, since the insulating transformer is expensive, large, and heavy, the size and weight of the inverter can be reduced.
It is a factor that hinders cost reduction, and the use of a so-called transformerless inverter without a transformer has been considered.

[0004]

Although the above-mentioned transformerless inverter has advantages such as small size, light weight and low cost, it has a problem from the viewpoint of preventing DC current from flowing to the inverter output side as described above. It remains.

In order to put a transformerless inverter into practical use, it is essential to propose a DC current outflow prevention means which has a relatively simple structure and is inexpensive as compared with a conventional transformer arrangement. However, until now, no specific DC current outflow prevention means has been proposed, and at present, it has not been put to practical use as a transformerless inverter.

In order to prevent a DC current from flowing out to the inverter output side when realizing a transformerless inverter, the inventor firstly converts a minute DC current flowing out and mixed into an AC current into a DC current. It was necessary to detect with a sensor, and it was found that by applying a negative feedback based on the detected data and setting the DC current to zero, it was possible to substantially prevent DC current outflow. .

An object of the present invention is to provide a DC current sensor suitable for realizing a substantial DC current outflow prevention method which solves the above problems.
It is an object of the present invention to provide a DC current sensor having a relatively simple structure and capable of detecting a minute DC current with high sensitivity, and to provide a DC current outflow prevention method using the same.

[0008]

SUMMARY OF THE INVENTION The inventor has previously made various measurements used in a wide range of fields, such as current measurement for maintaining and managing a switchboard control circuit signal and current measurement for controlling various DC devices. (Japanese Patent Application Laid-Open Nos. 6-74978 and 6-1943) have been proposed.
No. 89, JP-A-6-281674, JP-A-7-493
No. 57, JP-A-7-55846, JP-A-7-1103
No. 43, JP-A-7-128373, JP-A-7-198
754, JP-A-9-5361, etc.).

In order to achieve the above-mentioned object, the present inventors have studied a configuration that can effectively use the DC current sensors having various configurations proposed above. The inventor provided a sensor for detecting a DC component flowing in the detected wire and a sensor for detecting an AC component flowing in the detected wire, and further arranged a coil for a feedback current extending over each of these sensors. It has been found that the above object can be achieved by adopting the configuration.

That is, once the AC component detection sensor detects only the AC component and applies a feedback current to the feedback current coil so that the output of the AC component detection sensor becomes zero, the AC component detection sensor In addition to making the effect of the AC component substantially zero, the effect of the AC component in the DC component detection sensor can also be made substantially zero at the same time. It has been found that it can be used effectively and that DC current mixed in AC current can be detected.

Particularly, in the DC current sensors proposed by the inventor, a detection core made of a ring-shaped soft magnetic material is disposed in each case, and the detection core is formed based on a magnetic flux in the detection core generated by a DC current flowing in a conductor to be detected. Since the configuration detects the absolute value of the DC current, when the AC current and the DC current simultaneously flow through the detected wire, the magnetic flux in the detection core generated by the AC current and the magnetic flux in the detection core generated by the DC current Are superimposed, and it becomes impossible to detect the absolute value of only the DC current. However, by installing the AC component detection sensor and the feedback current coil described earlier,
If the magnetic flux in the detection core generated by the AC current can be made substantially zero, the superior characteristics of the DC current sensor proposed earlier can be effectively used, and the absolute value of only the DC current can be highly sensitive. It is considered that it is possible to detect

That is, the present invention provides a return current for a return current in which a detected wire through which a DC current and an AC current flow is penetrated inside each of a DC component detection sensor and an AC component detection sensor, and is wound around both sensors. A coil is provided, and a return current is supplied to the return current coil so that the output of the AC component detection sensor by the AC current flowing through the detected wire becomes zero, and the DC current generated by the AC current flowing through the detected wire is applied. This is a DC current sensor in which the influence on the component detection sensor is made substantially zero and the DC component detection sensor detects the DC current flowing through the detected conductor.

Further, the inventor has set forth that in the above-described direct current sensor, the alternating current component detecting sensor comprises an alternating current component detecting core made of an annular soft magnetic material, and an alternating current detecting coil wound around the core in a toroidal shape. Configuration: A configuration in which a gap is formed in at least one location in the circumferential direction of an AC component detection core, a DC component detection sensor, a DC component detection core made of an annular soft magnetic material, and an excitation coil wound around the core in a toroidal shape And a DC detection coil.

Further, the inventor has set forth that, in the above-described DC current sensor, the DC component detection sensor causes a triangular wave-shaped excitation current to generate a magnetic field exceeding the coercive force of the core in the DC component detection core through the excitation coil; DC component detection A configuration in which the timing at which the direction of the magnetic flux in the core is reversed is detected by a pulse-like voltage generated in a detection coil, and the interval between the pulses is measured to detect a DC current. The sensor passes the DC component detection core to the excitation coil alternately with positive and negative pulse currents having magnetically saturable peak values, and separates the peak value of each of the positive and negative pulse-like outputs generated in the detection coil. And a DC component detection sensor that measures the average output of the peak value and detects the DC current. The magnetic flux in the DC component detecting core generated based on the DC current flowing through the lead wire being detected by flowing periodically proposed together DC current sensor having the structure for switching.

Further, as described above, the inventor needs to detect a minute DC current flowing out and mixed in an AC current in order to prevent the DC current from flowing out to the inverter output side. It has been found that by applying a negative feedback based on the detected data and setting the DC current to zero, it is possible to substantially prevent the DC current from flowing out.

According to the present invention, the direct current is converted into an alternating current through an inverter, and the direct current flowing into the alternating current on the output side of the inverter is detected by the direct current sensor. This is a DC current outflow prevention method in which negative feedback is performed based on the detection data to make the outflowing DC current substantially zero.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the DC current sensor according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing an embodiment of a DC current sensor according to the present invention. In this configuration, 2 is a DC component detection sensor, and 3 is an AC component detection sensor. Reference numeral 10 denotes a DC component detection core made of an annular soft magnetic material constituting the DC component detection sensor, and reference numeral 20 similarly denotes an AC component detection core made of an annular soft magnetic material constituting the AC component detection sensor. Inside each of the cores 10 and 20, a detected conducting wire (not shown) through which a minute DC current flowing out together with the AC current flows is arranged.

The DC component detecting core 10 includes an exciting coil 11
And the DC detection coil 12 is wound and disposed in a toroidal shape,
An AC detection coil 21 is wound around the AC component detection core 20 in a toroidal shape. 22 is a DC component detection core 1
This is a return current coil that is wound and disposed in a toroidal shape over 0 and the AC component detection core 20. A phase correction circuit 30 and an amplifier 31 are connected between the AC detection coil 21 and the return current coil 22.

In the DC current sensor having the above configuration, the DC component detection sensor 2 has the structure proposed by the inventor, and the excitation coil 11 has the DC component detection core 10 attached thereto.
A triangular wave-like exciting current for generating a magnetic field exceeding the coercive force of the core 10 flows therein, and the timing at which the direction of the magnetic flux in the DC component detecting core 10 is reversed is determined by a pulse voltage generated in the DC detecting coil 12. The basic structure is a configuration for detecting and comparing and measuring the interval between the pulses (Japanese Patent Laid-Open No. 7-128373).

In this configuration, as shown in the figure, the structure of the DC component detection core is extremely simple, and the attached electronic circuit is also simple.
It is possible to provide the most effective DC current sensor at a small size and at a low price.

Further, these configurations will be described in detail with reference to FIGS. 2, 3 and 4. FIG. 2 shows a DC component detection sensor 2
FIG. 3 is a conceptual explanatory view illustrating the principle of operation of detecting a DC component. Here, in order to explain the principle of detection and operation of DC current, it is assumed that AC current does not flow through the detected conducting wire 1, and only DC current detection will be described.

The excitation coil 11 includes a DC component detection core 10
Generating a magnetic field exceeding the coercive force of the core 10 in FIG.
A triangular waveform exciting current i as shown by the solid line of A flows. That is, the peak value of the exciting current and i _p, the exciting coil 1
1, the number of turns is N, the coercive force of the DC component detection core 10 is Hc,
Assuming that the magnetic path length of the DC component detection core 10 is l, Hc <N
so that i _p / l the peak value of the triangular waveform exciting current i to set a i _p.

When the DC current I is not flowing through the detected conductor 1 (I = 0), the exciting current i increases and Ni / l = Hc
, The exciting current i decreases and Ni / l = −
At the time of Hc, the direction of the magnetic flux in the DC component detection core 10 is rapidly reversed as shown by the solid line in FIG. 3B, and the reverse direction pulse voltage as shown by the solid line in FIG. I do.

By passing this pulse voltage through a predetermined electric circuit, it is possible to finally obtain an analog output as shown in FIG. 3D. Here, if the coercive force Hc of the DC component detection core 10 is positive / negative symmetric, the pulse intervals T ₁ and T ₂ generated on the peak side and the valley side of the triangular excitation current i are independent of the magnitude of the coercive force Hc. Become equal.

When a DC current I is flowing through the conductive wire 1 to be detected (I = I ₀ ), the DC component detection core 10 has a magnetic field other than the magnetic field generated by the increase and decrease of the exciting current i as described above.
The direct current I flowing through the detection target wire 1 causes the magnetic field I
_{Since 0/1} is formed, these magnetic fields are superimposed and change as shown by broken lines in FIGS. 3A to 3C, respectively, and finally, an analog output as shown in FIG. 3E is obtained.

In this case, even if the coercive force Hc of the DC component detection core 10 is positive / negative symmetric, the difference (T ₂ <) between the pulse intervals T ₁ and T ₂ generated on the peak side and the valley side of the triangular excitation current i.
T ₁ ) will occur.

However, when the change per unit time of the triangular excitation current i is constant and the absolute values of the gradients at the time of increase and decrease are equal, the DC current I flowing through the detected wire 1 becomes
Proportional to _{{(T 1 -T 2) /} (T 1 ten T _2)}.

Therefore, by previously measuring the correlation between the difference between the pulse intervals T ₁ and T ₂ and the DC current I flowing through the conductor 1 to be detected, the respective pulse intervals T ₁ and T ₂ can be electrically determined. Thus, the absolute value of the DC current I flowing through the detected conductor 1 can be detected.

Next, means for making the magnetic flux in the detection core generated by the alternating current substantially zero will be described with reference to FIG. FIG. 4 is an explanatory perspective view of the AC component detection sensor 3, and shows a configuration in which an AC detection coil 21 and a return current coil 22 are wound around an AC component detection core 20.

The alternating current flowing through the detected conductor 1 causes
A magnetic flux φ is generated in the AC component detection core 20, and further,
An electromotive force is generated in the AC detection coil 21 based on the temporal change of the magnetic flux φ. Here, when a predetermined return current is passed through the return current coil 22 so that the electromotive force generated in the AC detection coil 21 becomes zero, the magnetic flux in the AC component detection core 20 can be substantially reduced to zero. it can.

Therefore, as shown in FIG. 1, the return current coil 22 extends not only between the AC component detection sensor 3 and the DC component detection sensor 2, that is, the AC component detection core 20, but also over the DC component detection core 10. If it is wound and arranged, the magnetic flux generated by the alternating current flowing through the detected wire 1 generated in the DC component detection core 10 can be substantially reduced to zero. The DC detection coil 12 can detect only the DC current based on the operation principle described above without being affected by the AC current. In the figure, reference numerals 30 and 31 denote an AC detection coil 21 and a feedback current coil 22.
And a phase correction circuit and an amplifier arranged between them.

The inductance of the AC detection coil 21 and the feedback current coil 22 due to the DC bias occurs in the AC component detection core 20, and if the phase correction in the return loop circuit becomes inappropriate, the system becomes unstable. Oscillate. In order to prevent this, it is desirable to form a gap at at least one location in the circumferential direction for the purpose of stabilizing the inductance. In particular, from the viewpoint of electrical balance and manufacturability,
As shown in the figure, it is desirable to form gaps 23a and 23b at two circumferential positions that are symmetrical. It is desirable to appropriately select the gap size according to the magnetic characteristics of the detection core and the magnitude of the DC current to be measured.

The DC component detecting core and the AC component detecting core include Ni—Fe alloy (permalloy), silicon steel plate,
It is possible to use a known soft magnetic material such as soft ferrite, but as can be seen from the above description, a material having a high magnetic permeability and a small coercive force is more preferable for the DC component detection core, and an AC component detection core is preferable. Since a material having good AC magnetic characteristics is more preferable,
It is desirable that the AC component detection core is made of Mn-Zn soft ferrite with a -Fe alloy.

The excitation coil and the DC detection coil wound around the DC component detection core are not limited to the configuration provided independently as shown in the figure, but may be one coil sharing each function. Is also possible. That is, the excitation coil and the DC detection coil are wound substantially in the same direction and at the same position, and the pulse-like voltage is also generated in the excitation coil. Is added, the exciting coil can share the function of the DC detection coil.

The DC current sensor of the present invention having the structure shown in FIG. 1 has the advantages that the whole structure of the sensor is simple, and that the size and the price can be reduced. It has been found that the use of the exciting current inevitably limits the response speed. That is, when the frequency of the triangular excitation current is increased, the AC magnetic characteristic of the soft magnetic material constituting the DC component detection core becomes a loop shape unlike the DC magnetic characteristic, and a clear zero crossing and a pulse are generated from the detection coil. Therefore, a triangular current of up to about several tens of Hz is usually used.

When a triangular wave current having such a frequency is used, the response speed of the sensor is about 2 seconds.
Application to a photovoltaic power generation system that requires a high response speed within 0.5 seconds is difficult. The inventor
As a result of studying a configuration that enables a high response speed while maintaining the advantages of the DC current sensor having the configuration shown in FIG. 1, it was found that, in the configuration shown in FIG. No, DC component detection core 10
It was confirmed that high responsiveness can be realized by alternately passing positive and negative pulse currents having peak values that can be magnetically saturated.

The mechanism for generating an electromotive force to the detection coil shown in FIG. 12 will be described in more detail. In the DC current sensor having the configuration shown in FIG. 1, in a state where no DC current is flowing through the detection target wire, the excitation coil 11 has a positive / negative value having a peak value capable of magnetically saturating the DC component detection core 10. When a pulse current (the absolute value of the peak value is the same) is alternately applied, the detection core 10 changes to O → a → O and further O → b → O on the BH curve as shown in FIG. 12A. A corresponding magnetic flux is generated, and as shown in FIG. 12B, an electromotive force proportional to the amount of change of the generated magnetic flux is detected by the detection coil 12 as the outputs V ₁ and V ₂ .

In the state where no DC current is flowing through the conductor to be detected, V ₁ = V ₂ as shown in the figure, and the average output of the peak value becomes zero. Here, for example, when a DC current on the + side flows through the detected wire, the DC component is detected by the DC current.
There is magnetized, moved by + [Delta] H in O point + side on the B-H curve of FIG. 12A, the position of O ₁ of FIG 12C. In such a state, when the same positive / negative pulse current is applied to the exciting coil 11 as described above, the detection core 10
As shown in FIG. 12D, a magnetic flux is generated according to the change of O ₁ -a ₁ -O ₁ on the BH curve, and further, the change of O ₁ → b ₁ → O ₁ ,
As described above, the electromotive force proportional to the amount of change in the generated magnetic flux is detected by the detection coil 12 as V ₁₁ and V ₁₂ .

In the display of A, C, and E in FIG. 12, the positions of a and b change in the H direction according to the DC current flowing through the conductor to be detected at the required BH position. For convenience, the moving position is shortened and schematically displayed.

As is apparent from the figure, the amount of change in magnetic flux based on the change in O ₁ -a ₁ -O ₁ is small. That is, the O point is +
This is because, by moving to the side by + ΔH, the saturation region on the + side is reached with a slight change in current, and the amount of magnetic flux generated substantially does not change even if the current increases thereafter. Also, O
₁ the amount of change in magnetic flux based on the change in the -b ₁ -O ₁ is large. That is, when the point O moves to the + side by + ΔH, the amount of change in magnetic flux until reaching the saturation region on the − side increases. Therefore, the electromotive forces V ₁₁ and V ₁₂ also satisfy V ₁₁ <V ₁₂ according to the change. Similarly, when a negative DC current flows through the detected conductor, the DC component magnetizes the DC component detection core 10, and the point O on the BH curve in FIG.
Moved by -ΔH to the side, the position of the O ₂ in FIG. 12E.
In such a state, when the same positive / negative pulse current as described above is applied to the exciting coil 11, the detection core 10
As shown in FIG. 2E, a magnetic flux is generated according to the change of O ₂ → a ₂ → O ₂ and further O ₂ → b ₂ → O ₂ on the BH curve.
An electromotive force proportional to the amount of change in the generated magnetic flux, such as 2F, is detected by the detection coil 12 as V ₂₁ and V ₂₂ (V ₂₁
> V _22).

As described with reference to FIGS. 12C and 12E,
According to the DC current flowing through the detected wire, the detection coil 12
Different peak values (V ₁₁ <
V ₁₂ , V ₂₁ > V ₂₂ ) are obtained, these positive and negative peak values are individually sampled and held, and the average output of the peak values is measured to obtain the average output and the absolute value of the DC current. Is confirmed in advance, the absolute value and direction of the DC current flowing through the detected conductor can be confirmed. Note that V ₁ + V ₂ , V ₁₁ + V ₁₂ , and V ₂₁ + V ₂₂ have substantially the same value.

In order to obtain the above effects, the positive and negative pulse currents flowing through the exciting coil 11 must be large enough to sufficiently saturate the detection core 10. That is, by the DC current flowing through the detected wire,
Even after the point O on the BH curve has moved, the saturation region on the BH curve (a,
It is clear from the above description that changes up to b, a ₁ , b ₁ , a ₂ , b ₂ ) need to be made.

Therefore, the required response speed, the detection core 1
It is desirable to set the frequency and the peak value of the pulse current flowing through the exciting coil 11 according to the material of 0 or the like. In addition,
According to the experiment of the inventor, in the configuration shown in FIG. 11, a pulse current having a frequency of 2 kHz and a positive and negative peak value of 25 V was passed through the exciting coil 11 and measured, and as a result, a triangular wave current was passed through the exciting coil 11. A measurement result with the same linearity as the measurement is obtained, and the response speed is about 0.1 second, which enables measurement at a response speed that is at least an order of magnitude faster than when a triangular wave current is applied. Was confirmed. In the above experiment, the excitation coil 11 was formed by winding an enamel wire having an outer diameter of 0.1 mm for 50 turns, and the detection coil 12 was formed by winding an enamel wire having an outer diameter of 0.1 mm for 500 turns.

In the configuration in which a predetermined pulse current is applied to the exciting coil 11, the AC magnetic characteristics (BH) of the detection core 10 are obtained.
If the waveform of the pulse current is sharp (short time) without being affected by the curve, the electromotive force generated in the detection coil 12 inevitably becomes sharp (short time), and the response speed can be greatly improved. Becomes

Although the principle of detecting the direct current has been described in detail above, the AC component detection core 20, the AC detection coil 21, and the feedback current coil 22 constituting the AC component detection sensor 3 also employ the same arrangement as that of FIG. Therefore, only a minute DC current flowing together with an AC current in the detected conductor can be measured with high sensitivity based on the same principle as that of the configuration in which a triangular wave current flows through the exciting coil 11.

Since any of the above-described configurations can employ a very simple configuration as the DC component detection core, it has already been described that the overall configuration as the DC current sensor can be simplified, and the size and cost can be reduced. As described above, by selecting the current to be supplied to the exciting coil according to the required response speed, the use thereof can be further expanded.
However, when the detection current becomes an eddy current and scales out, the operation as a sensor becomes unstable, so that the measurement range is relatively narrow (usually about 0.1 to 20 A).

In order to remedy such a drawback, the inventor arranged DC current sensors having the various configurations proposed above as DC component detection sensors in the DC current sensor of the present invention. In addition, it has been confirmed that various configurations according to various required characteristics can be provided. For example, it has been confirmed that the adoption of the configuration as shown in FIG. 9 enables not only expansion of the measurement range but also improvement of the response speed.

That is, as the DC component detection sensor 2, a pair of DC detection coils 33 electrically connected
a and 33b are wound in a toroidal shape on the short side of the rectangular frame-shaped soft magnetic material opposite to the DC component detection core 32, and flow out together with the AC current into the DC component detection core 32. The detecting conductor 1 through which a minute DC current flows flows through the detecting conductor 1. Further, as means for switching the magnetic flux Φ ₀ in the DC component detecting core 32 generated based on the DC current I flowing through the detecting conductor 1, A pair of exciting cores 34 made of a soft magnetic material forming a quadrangular cylindrical shape on the long sides at positions opposing the detection core 32
a, 34b and the DC component detection core 32
A configuration in which the exciting coil 35 is wound around the outer circumference (Japanese Patent Laid-Open No. 6-74978) can be employed.

In the DC component detection sensor 2 having the above-described configuration, when the DC current I flows through the wire 1 to be detected, a magnetic flux Φ ₀ is generated in the DC component detection core 32. When an alternating current (frequency f ₀ ) flows, an alternating magnetic flux is generated in the excitation cores 34a and 34b in the α direction in the figure, and the alternating magnetic flux causes the DC component detecting core 32 to rotate.
And the excitation cores 34a and 34b are magnetically saturated, and the magnetic flux Φ ₀ in the DC component detection core 32 is switched, so that the frequency of the alternating magnetic flux is twice (2f ₀ ) the excitation frequency. Is modulated. With the change of the magnetic flux Φ ₀ , an electromotive force (V _DET ) having a frequency of 2f ₀ proportional to the DC current I flowing through the wire 1 to be detected is applied to the DC detection coils 33 a, 3.
3b, and as a result, the absolute value of the DC current I flowing through the detected conductor 1 can be known.

Further, as the AC component detection sensor 3,
Rectangular component AC component detection core 40 made of soft magnetic material
By arranging a return current coil 42 so as to straddle the DC component detection core 32 and the AC component detection core 40 while arranging an AC detection coil 41 in the same manner as in FIG. The magnetic flux generated in the DC component detection core 32 due to the AC current flowing through the detected conductor I can be made substantially zero. Therefore, the DC component detection sensor 2 can realize detection of only the DC current based on the operation principle described above. In the drawings, 43a and 43b are gaps for preventing a change in inductance.

In the figure, the configuration in which the feedback current coil 42 is arranged at only one place is shown. However, in consideration of the electromagnetic balance, each side portion of the DC component detection core 32 and the AC component detection core 40 is provided. It is most preferable to dispose them at four locations. Further, although the AC component detection core 40 is shown as a rectangular plate-shaped configuration, the shape is not limited to the shape, and a disk-shaped or the like may be used in consideration of required measurement accuracy, winding workability of various coils, and the like. It is also possible to adopt the configuration described above.

According to the configuration shown in FIG. 9, there is no need to use a triangular excitation current, and the responsiveness can be greatly improved as compared with the configuration shown in FIG. Further, although the structure of the DC component detection core 32 is slightly more complicated than that of the configuration of FIG. 1, the detection current becomes an eddy current, and the operation as a sensor is relatively stable even when scaled out. Since high-sensitivity and high-accuracy measurement can be performed, the measurement range is also as wide as about 1 mA to 100 A. In addition, since noise can be easily removed on an electronic circuit, noise resistance is improved.

In the configuration shown in FIG. 10, characteristics equal to or higher than the configuration shown in FIG. 9 can be obtained. The DC component detection sensor 2 constituting the DC current sensor shown in FIG. 10 simplifies the configuration of the DC component detection core and enables the S / N ratio to be improved, and the DC detection coil 53 is formed in a toroidal shape. A configuration in which a DC component detection core 52 made of an annular soft magnetic material to be wound and disposed is formed in a tubular shape, and an excitation coil 55 is wound and disposed in a hollow portion communicating with the detection core 52 in a circumferential direction (Japanese Patent Laid-Open No. 7-198754). No.).

In such a configuration, when the DC current I flows through the conductive wire 1 to be detected, the magnetic flux Φ
₀ occurs, but this time, alternating magnetic flux in the figure α direction is generated and flow excitation coil 55 in a predetermined excitation current (AC current) in the DC component detecting core 52, the DC component detecting core by the alternating magnetic flux Almost the entire region 52 is periodically magnetically saturated, and the magnetic flux Φ ₀ in the DC component detection core 52 is switched. In this configuration, the DC component detection core 52 also serves as the excitation core in the DC component detection sensor described with reference to FIG. It is possible to know the absolute value of the DC current I flowing through the detection conductor 1.

In the figure, reference numeral 3 denotes an AC component detection sensor 3.
The configuration is substantially the same as that of the DC current sensor of FIG. That is, in the figure, reference numeral 60 denotes an AC component detection core made of a ring-shaped soft magnetic material, 61 denotes an AC detection coil, 62 denotes a feedback current coil, and 63a and 63b.
Is a gap for preventing inductance change. Therefore,
The operating principle similar to that of FIG. 1 makes it possible to make the magnetic flux generated in the DC component detection core 52 by the AC current flowing through the detected wire substantially zero, and the DC component detection sensor 2 described earlier. Based on the working principle
Detection of only DC current can be realized.

Also in the DC current sensor having this configuration,
Although high-speed response, high sensitivity, and high precision can be realized similarly to the configuration shown in FIG. 9, the manufacture of the DC component detection core 52 is particularly easy to mechanize, and a lower price can be realized. Further, if a ferrite core is used for the DC component detection core 52, the AC magnetic characteristics are originally good, so that a higher speed response can be further improved. Further, although the electronic circuit is slightly complicated, it is possible to obtain superior noise resistance characteristics as compared with the configurations shown in FIGS.

The DC component detecting sensor constituting the DC current sensor having the configuration shown in FIGS. 9 and 10 described above has a magnetic flux Φ ₀ in the DC component detecting core generated based on the DC current I flowing through the conductive wire 1 to be detected. Is configured to form a magnetically saturated region due to the alternating magnetic flux in a part or all of the DC component detection core 52 in the circumferential direction to periodically cut off the magnetic flux Φ _0. The DC component detection sensor having the configuration shown in FIG. 11 differs in the means for switching the magnetic flux Φ ₀ .

The DC component detection sensor 2 constituting the DC current sensor shown in FIG. 11 is adapted to apply a circumferential magnetic field in the DC component detection core 72 generated based on the DC current I flowing through the conductive wire 1 to be detected. By applying a magnetic field whose direction changes periodically orthogonal to the magnetic field, the magnetization direction in the DC component detection core 72 based on these synthetic magnetic fields is rotated,
The magnetic flux Φ ₀ in the DC component detection core 72 generated based on the DC current I flowing through the detected conductor 1 is modulated to perform magnetic switching. Also in this configuration, the mechanism of generating an electromotive force to the DC detection coil 73 is substantially the same as that of the DC current sensor of FIG. 9 although the switching means is different (Japanese Patent Application No. Hei 7-180721).
issue).

More specifically, the DC component detection core 72 includes:
A plurality of through holes 7 formed on the side surface of the detection core 72
8 (shown in a rectangular shape in the figure, but may be a circular shape, etc.) so that the direction of the current in the same through-hole is the same and the direction of the current in the adjacent through-hole is opposite.
a, 75b are wound and the DC detection coil 73 is wound around the outer periphery in a toroidal shape. By applying a predetermined exciting current (AC current) to the exciting coils 75a and 75b, the DC component detecting core 7
2, the absolute value of the DC current I flowing through the target wire 1 to be detected can be known as described above.

In the figure, reference numeral 3 denotes an AC component detection sensor 3, which has substantially the same configuration as that of the DC current sensor of FIG. That is, in the drawing, reference numeral 80 denotes an AC component detection core made of a ring-shaped soft magnetic material, 81 denotes an AC detection coil, 82 denotes a feedback current coil, and 83a and 83b denote inductance change preventing gaps. Therefore, the magnetic flux generated in the DC component detection core 72 due to the AC current flowing through the detected wire can be made substantially zero by the operation principle similar to that of FIG. Based on the operation principle described above, detection of only DC current can be realized.

With the DC current sensor having this configuration, it is possible to obtain almost the same characteristics as the configuration shown in FIG. 9. However, when the detection current is an eddy current and scales out, the DC component detection core 72 Although the rotation of the magnetization direction within the sensor is not performed smoothly and the operation as a sensor becomes unstable, the measurement range is slightly narrowed, but is usually 1 mA.
Within the range of about 10 to 10 A, high-speed response, high sensitivity, and high accuracy can be realized. Further, since the structure of the DC component detection core 72 is very simple, it is an effective configuration from the viewpoint of size reduction and cost reduction.

FIGS. 9 to 11 show a direct current component detection sensor, in which a predetermined alternating current is applied to an exciting coil to generate a direct current generated based on a direct current mixed in an alternating current flowing in a conductor to be detected. Although an example of a configuration in which the magnetic flux in the component detection core is synchronously switched has been described,
Not limited to the illustrated embodiment, for example, vary with the repulsion between the direction of the alternating magnetic flux perpendicular to the direction of the magnetic flux [Phi ₀ in the detecting core which occurs on the basis of the DC current flowing in the lead wire being detected relative to the magnetic flux [Phi ₀ By doing so, it is possible to use sensors having various configurations proposed previously, such as a configuration in which the magnetic flux Φ ₀ is periodically interrupted and the magnetic flux Φ ₀ is switched as a result (Japanese Patent Laid-Open No. 7-55846). .

Further, as a DC component detection sensor,
It is also possible to adopt a configuration in which a gap is formed in a part of a DC component detection core made of an annular soft magnetic material, and a Hall element is arranged in the gap.

Further, as a configuration of a DC component detection sensor which is excellent in zero point accuracy and temperature characteristics and can measure a wide range of DC current from a small current to a large current, an annular soft coil having a detection coil wound in a toroidal shape is provided. A direct current sensor having a means for switching a magnetic flux in a detection core generated based on a direct current flowing through the detected conductor, wherein the detected conductor through which a direct current flows is disposed through a detection core made of a magnetic material, A feedback coil that generates a magnetic flux in a direction to cancel the magnetic flux in the detection core generated based on the DC current flowing through the detected wire and makes the output of the detection coil substantially zero is disposed in a toroidal shape around the detection core. A configuration for detecting a direct current flowing through a detection target wire by measuring an applied current to the feedback coil (Japanese Patent Application No. Hei 8 54454 No.) can be adopted.

A similar structure of a direct current component detecting sensor includes a detecting core made of an annular or polygonal annular soft magnetic material through which a detected wire through which a direct current flows flows, and an outer peripheral portion of the detecting core. An exciting core made of a soft magnetic material connected at right angles to the circumferential direction of the detecting core at a position symmetrical with respect to the axial center of the detecting core at least at four or more locations to form an annular shape; A detection coil wound around the detection core, an excitation coil wound around the detection core in the circumferential direction, and a toroidal winding around the detection core, which is generated based on a DC current flowing through the detected conductor. A feedback coil that generates a magnetic flux in a direction to cancel the magnetic flux in the detection core and makes the output of the detection coil substantially zero (Japanese Patent Application No. 8-35445).
No. 3) can be adopted.

In the DC current sensor according to the present invention, the feedback current coil includes a DC component detection sensor (DC component detection core) and an AC component detection sensor (AC component detection core).
The configuration in which the coils are wound and arranged means that the winding is such that the same magnetomotive force (ampere turn) is applied to each of the two sensors (cores). Instead, it is possible to employ a configuration in which each sensor (core) is independently wound and arranged, and then connected in series with each other.

In the present invention, the ring-shaped soft magnetic material is not limited to the soft magnetic material having a so-called ring shape, but may be any other material as long as the soft magnetic material can form an electromagnetic closed circuit. Various configurations such as an annular shape, a rectangular frame shape and the like can be adopted as shown in the figure, and the DC component detection core and the AC component detection core do not necessarily have to have the same shape and the same dimensions.

[0068]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The direct current component detection core is a permalloy C (78% Ni-5% Mo-4% C) made of a thin plate having a thickness of 0.5 mm.
u-balFe) was punched into an outer diameter of 45 mm and an inner diameter of 33 mm, and was subjected to a predetermined heat treatment to complete it.

The AC component detecting core is formed by laminating ten permalloy C punched products having the same material and dimensions as those of the DC component detecting core described above, and cutting them in half so as to have a symmetrical shape. Further, after performing a predetermined heat treatment, these pair of core pieces are integrated into a ring shape such that an inductance change prevention gap is formed at two places in the circumferential direction via a gap spacer having a thickness of 50 μm,
completed.

After placing each of the DC component detection core and the AC component detection core in an insulating case, as shown in FIG. 1, the excitation coil, the DC detection coil, the AC detection coil, and the return current coil are toroidally placed at predetermined positions. Winding arrangement. Each of these coils was wound with an enamel wire having an outer diameter of 0.2 mm for 300 turns.

Further, the electronic circuit shown in FIG. 5 was connected to each coil, and the characteristics of the DC current sensor of the present invention were measured. The results are shown in FIGS. L ₂₁ is the alternating-current detection coil in FIG. 5A, L ₂₂ is Kikan current coil, L ₁₂ in FIG. 5B is a DC detection coil, Aout the sensor output, L in FIG. 5C
Reference numeral ₁₁ denotes an exciting coil.

The detected conductor penetrating inside the DC component detecting core and the AC component detecting core is a vinyl-coated wire having an outer diameter of 8 mm, and the triangular waveform exciting current flowing through the exciting coil is 90 Hz, l _p = ± 15 mA.

FIG. 6 shows the input / output characteristics when only the DC current is applied to the detected conductor while no AC current is applied. FIG. 7 shows the state in which the AC current of 15 A is superimposed on the detected conductor. FIG. 8 shows the input / output characteristics obtained by measuring the DC current, and FIG. 8 shows the input / output characteristics in which the measurement results of FIGS. 6 and 7 are described on the same graph. Note that black circles in FIG.
The mark indicates the input / output characteristic corresponding to FIG. 6, and the mark ○ indicates the input / output characteristic corresponding to FIG.

FIG. 8 shows that the DC current sensor according to the present invention can measure a minute DC current with high sensitivity regardless of the presence or absence of the AC current flowing through the conductor to be detected. That is, it is possible to measure, with high sensitivity, a minute DC current flowing out and mixed in an AC current, and to achieve the object of realizing the practical use of a transformerless inverter.

Since the AC component detection core forms a gap for stabilizing inductance as described above, the magnetic resistance increases and the amount of magnetic flux generated substantially decreases. Output cannot be obtained. For this reason, a plurality of punched permalloy thin sheets as in the embodiment are laminated on the AC component detection core, and by increasing the cross-sectional area of the detection core, the substantial amount of magnetic flux generated is increased and good AC magnetic field is obtained. Characteristics can be secured.

When the Mn—Zn-based ferrite is used, since the AC magnetic properties are essentially good, the C
Since it can be made into a mold integrated product, it is easy to assemble and has a preferable configuration in terms of productivity and the like.

Further, it was confirmed that substantially the same results can be obtained with respect to the measurement sensitivity and the like of the entire DC current sensor as well as the configuration using the above-described integrated product of the permalloy laminate and the Mn-Zn-based ferrite.

Further, in the configurations shown in FIGS. 9, 10 and 11, similarly to the previous embodiment, it is possible to measure a minute or relatively large DC current flowing out and mixed into the AC current with high sensitivity. It was confirmed that the transformer-less inverter could be put to practical use.

[0079]

The DC current sensor according to the present invention is capable of non-contact and highly sensitive measurement of a minute DC current flowing and mixing into an AC current in a detected conductor. In an inverter or the like, a minute DC current flowing out and mixed into the AC current on the inverter output side is detected, a negative return is performed based on the detected data, and the DC current is substantially reduced to zero. It is possible to prevent the leakage of a direct current.

Therefore, the DC current sensor according to the present invention and the DC current outflow prevention method using the same can prevent DC current from flowing into AC electric equipment on the load side of the inverter, and connect a transformer to the conventional inverter output side. A transformerless inverter having a simpler configuration and a lower cost can be put into practical use without causing a problem such as burnout of the inverter as compared with the configuration in which the inverters are arranged.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing one embodiment of a DC current sensor of the present invention.

FIG. 2 is a perspective explanatory view of a DC component detection sensor of the DC current sensor according to the present invention.

FIG. 3 is a conceptual explanatory view for explaining the operating principle of the DC component detection sensor of the DC current sensor according to the present invention, wherein A is a triangular excitation current, B is the direction of magnetic flux, C is a pulse voltage,
D represents an analog output, and E represents an analog output.

FIG. 4 is an explanatory perspective view of an AC component detection sensor of the DC current sensor according to the present invention.

FIGS. 5A, 5B, and 5C are circuit diagrams of electronic circuits connected to the DC current sensor of the present invention.

FIG. 6 is a graph showing a relationship between a through DC current and an output voltage in the example, and shows input / output characteristics when only a DC current is passed in a state where an AC current is not passed through a detected conductor.

FIG. 7 is a graph showing a relationship between a through DC current and an output voltage in the example, and shows input / output characteristics obtained by measuring a DC current in a state in which a 15 A AC current is superimposed on a detected conductor.

FIG. 8 is a graph showing input / output characteristics in which the measurement results of FIGS. 6 and 7 are described on the same graph.

FIG. 9 is an explanatory perspective view showing a combination of an AC component detection sensor and a DC component detection sensor that constitute another DC current sensor according to the present invention.

FIG. 10 is an explanatory perspective view showing a combination of an AC component detection sensor and a DC component detection sensor that constitute another DC current sensor according to the present invention.

FIG. 11 is an explanatory perspective view showing a combination of an AC component detection sensor and a DC component detection sensor that constitute another DC current sensor according to the present invention.

FIG. 12 shows an electromotive force generation mechanism for a detection coil when a positive / negative pulse current having a peak value that magnetically saturates a DC component detection core is alternately applied to an excitation coil of the DC current sensor of FIG. 1; To explain, A,
C and D are BH curves, and B, D and F are graphs showing the electromotive force output to the detection coil.

[Explanation of symbols]

DESCRIPTION OF REFERENCE NUMERALS 1 detected conductor 2 DC component detection sensor 3 AC component detection sensor 10, 32, 52, 72 DC component detection core 11, 35, 55, 75a, 75b Exciting coil 12, 33a, 33b, 53, 73 DC detection coil 20, 40, 60, 80 AC component detection cores 21, 41, 61, 81 AC detection coils 22, 42, 62, 82 Return current coils 23a, 23b, 43a, 43b, 63a, 63b, 8
3a, 83 b gap 30 the phase correction circuit 31 amplifiers 34a, 34b exciting core 36 perpendicular portion 78 through hole L ₁₁ exciting coil L ₁₂ DC detection coil L ₂₁ AC detection coil L ₂₂ Kikan current coil

Claims (9)

[Claims] 1. A coil for a return current which is disposed inside each of a DC component detection sensor and an AC component detection sensor, through which a detection target wire through which a DC current and an AC current flow is penetrated, and which is wound and arranged over both sensors. A return current is passed through the return current coil so that the output of the AC component detection sensor due to the AC current flowing through the detected wire becomes zero, and a DC component detection sensor is generated by the AC current flowing through the detected wire. A DC current sensor for substantially eliminating the influence of the above and detecting a DC current flowing through the detected conductor with a DC component detection sensor. 2. The direct current sensor according to claim 1, wherein the alternating current component detecting sensor comprises an alternating current component detecting core made of an annular soft magnetic material and an alternating current detecting coil wound around the core in a toroidal shape. 3. The direct current sensor according to claim 2, wherein a gap is formed in at least one circumferential position of the alternating current component detection core. 4. A DC current sensor according to claim 2, wherein the DC component detection sensor comprises a DC component detection core made of an annular soft magnetic material, an excitation coil wound around the core in a toroidal shape, and a DC detection coil. . 5. The DC component detection sensor according to claim 4, wherein the DC component detection sensor supplies a triangular wave-like exciting current for generating a magnetic field exceeding a coercive force of the DC component detection core to the excitation coil. A DC current sensor having a configuration in which a timing at which the direction of a magnetic flux is reversed is detected by a pulse-like voltage generated in a detection coil, and an interval between the pulses is compared and measured to detect a DC current. 6. The DC component detecting sensor according to claim 4, wherein the DC component detecting core flows through the exciting coil alternately a positive / negative pulse current having a peak value which can be magnetically saturated, and is generated in the detecting coil. A direct current sensor comprising a configuration in which the peak value of each of positive and negative pulse-shaped outputs is individually sampled and held, and an average output of the peak values is measured to detect a direct current. 7. A DC component detecting sensor according to claim 4, wherein the DC component detecting sensor periodically generates a magnetic flux in the DC component detecting core based on the DC current flowing through the detected conductor by flowing a predetermined AC current through the exciting coil. DC current sensor consisting of a switching device. 8. A DC current, which is obtained by converting a DC current into an AC current via an inverter and flowing out into the AC current on the output side of the inverter, is detected by a DC current sensor, and based on data detected by the DC current sensor. A DC current outflow prevention method for applying negative feedback to make the outflow DC current substantially zero. 9. The return current according to claim 7, wherein a detected wire through which a DC current and an AC current flow is penetrated inside each of the DC component detection sensor and the AC component detection sensor, and is wound and arranged over both sensors. A return current is passed through the return current coil so that the output of the AC component detection sensor due to the AC current flowing through the detected wire becomes zero, and the AC current flowing through the detected wire is used. By making the effect on the DC component detection sensor substantially zero,
A DC current outflow prevention method using a DC current sensor for detecting a DC current flowing through the detected conductor with a DC component detection sensor.