JP2000266785A - Current measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a current to be measured with a small-sized device and in a low cost, regardless of the current capacity of a current to be measured and a shape of a current path to be measured. SOLUTION: A current to be measured 1a flowing in a current path to be measured 1 is shunted by a non-inductive shunt 2, and the current to be measured 1a is detected from the shunted current through a transformer 3. Insulation from the current path to be measured 1 can be retained by the transformer 3, and a change of a magnetic flux (ϕa) generated in a core 3a of the transformer 3 is detected, therefore, the current to be measured 1a of a direct current can also be measured. By sending a compensating current 1b in a compensating winding 5, inductance of an input winding 4 becomes zero apparently, to enable to measure correctly the current to be measured 1a. And besides, as the current path to be measured 1 is not penetrated into the core 3a, miniaturization of the whole device and cost reduction can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current measuring device for measuring a DC or AC current flowing in a current path to be measured while maintaining insulation between the current path and the current path to be measured.

[0002]

2. Description of the Related Art Conventionally, a coaxial resistor as shown in FIG. 20 has been used as a current measuring device for measuring a direct current or an alternating current flowing through a current path to be measured without maintaining insulation from the current path to be measured. There was something. The coaxial resistor includes a cylindrical conductor (cylindrical conductor) 40, a central conductor 41 disposed in the cylindrical conductor 40, an end of the cylindrical conductor 40 and the central conductor 41.
A metal resistor 42 inserted between the ends of the cylindrical conductor 40 and terminals 43 and 43 derived from the resistor 42 are provided at the ends of the cylindrical conductor 40 and the center conductor 41, respectively. The current path 1 is connected. That is,
When the measured current flows through the coaxial resistor connected in series to the measured current path 1, a potential difference (voltage drop) proportional to the measured current is generated between the terminals 43, 43. Can be measured. When the current to be measured is a high-frequency AC current, the generated magnetic flux can be canceled by reversing the direction of the current to be measured between the cylindrical conductor 40 and the center conductor 41, and the inductance can be reduced. Measurement error due to the above can be suppressed. For this reason, the coaxial resistor is sometimes called a non-inductive shunt.

On the other hand, as a current measuring device for measuring a direct current or an alternating current flowing through a current path to be measured while maintaining insulation between the current path to be measured, a substantially ring-shaped current penetrating current path 1 has conventionally been used. A transformer 43 in which a compensation winding 43b is wound around a core 43a, and a gap 43 formed in the core 43a
c, a magnetic balance circuit 45 for supplying a current to the compensation winding 43b in accordance with the detection result of the magnetic detection element 44, and a detection for detecting a current supplied from the magnetic balance circuit 45. Some include a resistor Rs.
That is, when the measured current flows, a magnetic flux generated around the measured current path 1 generates a magnetic flux proportional to the measured current in the core 43a, and the magnetic detection element 44 inserted and disposed in the gap 43c of the core 43a. An output voltage proportional to the magnetic flux generated in the core 43a is output to the magnetic balance circuit 45, and a current that cancels out the magnetic field generated by the current to be measured in the magnetic balance circuit 45 is supplied to the compensation winding 43b. The current to be measured can be measured by detecting the current proportional to the current with the detection resistor Rs.

[0004]

By the way, in the former conventional configuration using only the non-inductive shunt (coaxial resistor), the direct current or the alternating current to be measured is maintained while the insulation with respect to the current path 1 to be measured is maintained. The current cannot be measured.

In the latter conventional example, the current path 1 to be measured is passed through the core 43a of the transformer 43. Therefore, when a large current is measured, the transformer 43 becomes large in accordance with the current path 1 to be measured. I will. Further magnetic balance circuit 4
5, the current supplied to the compensation winding 43b increases in accordance with the current to be measured, so that the number of turns of the compensation winding 43b must also be increased. As a result, the current measuring device is increased in size and cost. In addition, it is necessary to change the shape of the core 43a and the specifications of the compensating winding 43b according to the shape of the current path 1 to be measured, which makes it difficult to change the design. Moreover, if the measured current path 1 is bent, an extra mounting space is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce the size of a current to be measured at a small size and at low cost regardless of the current capacity of the current to be measured and the shape of the current path to be measured. It is to provide a current measuring device capable of measuring.

[0007]

According to a first aspect of the present invention, there is provided a non-inductive shunt for shunting a current to be measured flowing through a current path to be measured and an output terminal of the non-inductive shunt. A transformer having an input winding connected thereto, magnetic detecting means for detecting a magnetic flux generated in the core of the transformer, a compensating winding wound on the core of the transformer, and A magnetic balance circuit for supplying a current to the compensation winding to cancel a change in magnetic flux generated in the core, and compensation current detection means for detecting a compensation current flowing in the compensation winding; As a result, the compensation current flowing through the compensation winding is proportional to the measured current. Therefore, the measured current can be measured by detecting the compensation current by the compensation current detecting means. Thus, measurement can be performed without penetrating the measured current path through the transformer core, and the current capacity of the measured current and the shape of the measured current path can be changed simply by changing the non-inductive shunt that shunts the measured current. As a result, the measured current can be measured at a small size and at low cost regardless of the current capacity of the measured current and the shape of the measured current path.

According to a second aspect of the present invention, in the first aspect of the present invention, the direction of the current flowing through the non-inductive shunt in a pair of opposing portions made of a metal material having a predetermined resistance value at the apex portion is a boundary. It is characterized by comprising a current detecting portion having a current path formed in a substantially U-shape in the opposite direction, and a pair of terminal plates provided at an end of each of the opposed portions and connected to a current path to be measured. In addition to the function of the invention of claim 1, the terminal plate is formed of a metal material having a lower resistance value than the metal material of the current detecting portion, so that the generation of Joule heat in the terminal plate is suppressed and the size of the non-inductive shunt is reduced. Therefore, the size of the entire current measuring device can be reduced.

According to a third aspect of the present invention, in the second aspect of the present invention, the input winding of the transformer is formed of the same metal material as the current detecting portion. Since the resistance value of the current detector and the resistance value of the input winding of the transformer change at the same rate with respect to the change in ambient temperature, it is possible to improve the temperature characteristics by canceling the characteristic variation caused by the temperature change of the resistance. it can.

[0010] The invention of claim 4 is the invention of claim 1 or 2 or 3.
The invention according to claim 1, wherein the magnetic detecting means comprises a magnetic detecting element disposed in a gap provided in a core of the transformer, and has a simple configuration in addition to the operation of the invention according to claim 1, 2, or 3. The magnetic flux generated in the core can be detected.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, a shield case formed of a magnetic material and accommodating a transformer is provided. The effect of the external magnetic flux other than the magnetic flux generated by the measurement current on the magnetic detection element can be removed, and the noise immunity to external noise is improved.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the present invention, the magnetic detecting element comprises a Hall element. In addition to the functions of the fourth or fifth aspect, the cost of the magnetic detecting element is reduced. Down can be achieved.

According to a seventh aspect of the present invention, in the fourth or fifth aspect of the present invention, the magnetic sensing element comprises a magnetoresistive element. The magnetic flux can be detected.

According to an eighth aspect of the present invention, in the fourth or fifth aspect of the present invention, the magnetic detecting element comprises a magnetic impedance element. In addition, a minute magnetic flux can be detected.

According to a ninth aspect of the present invention, in the fourth or fifth aspect of the present invention, the magnetic detecting element comprises a flux gate sensor. In addition, a minute magnetic flux can be detected.

According to a tenth aspect of the present invention, in the first, second, or third aspect, the magnetic detecting means includes: an exciting winding wound around a core of the transformer; and an exciting means for supplying a current to the exciting winding. And an asymmetry detecting means for detecting the asymmetry of the current waveform flowing in the exciting winding. In addition to the effect of the invention according to claim 1, 2, 3 or 4 The magnetic flux can be detected.

According to an eleventh aspect of the present invention, in the first, second, or third aspect, the magnetic detecting means includes: an exciting winding wound around a core of the transformer; and an exciting means for supplying a current to the exciting winding. And an asymmetry detecting means for detecting the asymmetry of the voltage waveform generated between both ends of the exciting winding, wherein the core has a simple structure in addition to the function of the invention according to claim 1, 2, or 3. Can be detected, and the detection sensitivity can be improved when the change in the voltage across the exciting winding is larger than the exciting current flowing through the exciting winding.

According to a twelfth aspect of the present invention, in the first, second, or third aspect, the magnetic detecting means includes: an exciting winding wound around a core of the transformer; and an exciting means for supplying a current to the exciting winding. A detection winding wound around the core of the transformer and having a larger number of turns than the excitation winding, and asymmetric detection means for detecting the asymmetry of the voltage waveform generated between both ends of the detection winding, In addition to the effect of the invention of claim 1, the magnetic flux generated in the core can be detected with a simple configuration, and a voltage higher than the voltage applied to the excitation winding is generated in the detection winding. The detection sensitivity can be improved.

The invention of claim 13 is the invention of claim 10 or 11
Or the transformer according to claim 12, wherein the core of the transformer is formed to have a shape in which the cross-sectional area changes in a part thereof, and in addition to the effect of the invention according to claim 10 or 11, the change in magnetic flux density with respect to the magnetic field of the core Can be sharpened, and the detection sensitivity can be improved.

According to a fourteenth aspect of the present invention, in any one of the tenth to thirteenth aspects, a plurality of types of magnetic materials are laminated to form a transformer core.
In addition to the effects of any one of the inventions of (1) to (13), the detection range can be expanded because magnetic saturation of the core hardly occurs.

According to a fifteenth aspect of the present invention, in any one of the tenth to thirteenth aspects, there is provided a core formed of a different magnetic material, and the input winding and the compensation winding wound around each core are connected in series. A plurality of connected transformers are provided, and in addition to the function of any one of claims 10 to 13, as long as there is a core that is not magnetically saturated even if any core is magnetically saturated. The magnetic flux can be detected, and the detection range can be expanded.

According to a sixteenth aspect of the present invention, in any one of the tenth to fifteenth aspects, the asymmetry detecting means includes means for comparing a peak value of a current waveform or a voltage waveform every half cycle. As a feature, in addition to the effect of any one of the tenth to fifteenth aspects, the asymmetry of the voltage waveform can be detected with a simple configuration.

According to a seventeenth aspect of the present invention, in any one of the tenth to fifteenth aspects, the asymmetric detecting means outputs a waveform proportional to a difference between the current waveform or the voltage waveform and the reference waveform, A comparison means for comparing a peak value of the output waveform of the difference output means for each half cycle, wherein the voltage of the output signal is reduced by a simple configuration. The asymmetry of the waveform can be detected, and the detection sensitivity can be improved.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) As shown in FIG. 1, a current measuring apparatus according to the present embodiment includes a non-inductive shunt 2 for shunting a measured current Ia flowing through a measured current path 1, and a non-inductive shunt. A transformer 3 having an input winding 4 connected between output terminals 2a and 2b of the shunt 2, magnetic detecting means 6 for detecting a magnetic flux generated in a core 3a of the transformer 3, and a coil 3 wound around the core 3a of the transformer 3. A compensating winding 5, a magnetic balance circuit 7 for supplying a compensating current Ib to the compensating winding 5 so as to cancel a change in magnetic flux generated in the core 3 a of the transformer 3 according to the detection result of the magnetism detecting means 6, A detection resistor Rs is provided as compensation current detection means for detecting a compensation current Ib flowing through the winding 5.

The non-inductive shunt 2 is, for example, a coaxial resistor described in the related art, and is connected in series to the current path 1 to be measured. The magnetic detecting means 6 outputs a detection voltage proportional to the magnetic flux φa generated in the core 3a of the transformer 3 to the magnetic balance circuit 7. The magnetic balance circuit 7 includes, for example, DC power supplies E1, E
2, an operational power supply ± Vcc is supplied and an operational amplifier (not shown) amplifies the detection voltage.

Next, the operation of this embodiment will be described.

When the measured current Ia is supplied to the measured current path 1, a voltage drop occurs between the output terminals 2a and 2b of the non-inductive shunt 2 in proportion to the measured current Ia, and this voltage drop (potential difference) occurs. As a result, a magnetic flux φa is generated in the core 3 a of the transformer 3. The magnetic flux φa is detected by the magnetic detection means 6, and a detection voltage proportional to the magnetic flux φa is output to the magnetic balance circuit 7. The magnetic balance circuit 7 amplifies the detection voltage and cancels the magnetic flux φa.
b is supplied to the compensation winding 5.

Since the compensation current Ib supplied from the magnetic balance circuit 7 to the compensation winding 5 is proportional to the measured current Ia flowing through the measured current path 1, it is inserted into the path through which the compensation current Ib flows. A voltage drop occurs in the detected detection resistor Rs in proportion to the measured current Ia. Therefore, the current Ia to be measured can be measured by detecting the voltage drop (the voltage between both ends) of the detection resistor Rs.

In this embodiment, the measured current Ia flowing through the measured current path 1 is divided by the non-inductive shunt 2, and the measured current is detected via the transformer 3 from the divided current. Therefore, the transformer 3 can maintain insulation from the current path 1 to be measured, and can detect a change in the magnetic flux φa generated in the core 3 a of the transformer 3. That is, the DC measured current Ia can also be measured.
Further, by flowing the compensation current Ib through the compensation winding 5, the inductance of the input winding 4 is apparently eliminated, and the voltage drop between the output terminals 2a and 2b of the non-inductive shunt 2 can be accurately detected, and as a result, the measured The current Ia can be accurately measured. Further, since only the input winding 4 and the compensation winding 5 are wound around the core 3a of the transformer 3,
The diameter of the core 3a can be reduced as compared with the conventional example in which the measured current path 1 penetrates the core 3a, and the difference in the shape of the measured current path 1 and the difference in the current capacity of the measured current Ia can be reduced. This can be dealt with only by changing the non-inductive shunt 2. As a result, the size and cost of the entire apparatus can be reduced. Further, since the non-inductive shunt 2 and other circuit units including the transformer 3 can be installed separately, there is an advantage that the layout of the device is simplified.

(Embodiment 2) In this embodiment, as shown in FIG. 2, the basic configuration and operation are common to those of Embodiment 1, and the common parts are denoted by the same reference numerals and description thereof is omitted. Only the configuration of the non-inductive shunt 10 that is a feature of the present embodiment will be described.

The non-inductive shunt 10 according to the present embodiment comprises:
A current detector 11 having a substantially U-shaped current path in which the directions of currents flowing through a pair of opposing portions 11a, 11a opposing each other by a metal material having a predetermined resistance value are opposite to each other at a vertex 11b. And a pair of terminal plates 12, 12 provided at the ends of the opposed portions 11a, 11a and connected to the current path 1 to be measured, and a voltage drop (potential difference) generated between the opposed portions 11a, 11a. Output terminals 10a, 1
0b. The current paths 1, 1 to be measured are connected to the terminal plates 12, 12 by terminal screws 13.

Thus, the measured current Ia
Are supplied with electricity, the two opposing portions 11a, 11
Since a current flows in a in the opposite direction and the magnetic flux is offset, the inductance of the non-inductive shunt 10 can be suppressed to a low value. Then, a voltage drop proportional to the measured current Ia occurs between the output terminals 12 and 12, and the measured current Ia is determined based on the voltage drop of the detection resistor Rs in the same manner as in the first embodiment.
Can be measured.

Here, the terminal plates 12 and 12 and the current detector 1
1, the terminal plates 12, 12 can be formed of a metal material having a lower resistance value than the metal material forming the current detection unit 11, and thereby the terminal plates 12, 12 can be formed. , The generation of Joule heat can be suppressed. As a result, the calorific value of the entire non-inductive shunt 10 is suppressed, and the size of the non-inductive shunt 10 can be reduced.

In this embodiment, as described above, the size of the non-inductive shunt 10 is reduced by suppressing the generation of Joule heat.
Is used, the size of the entire current measuring device can be reduced.

(Embodiment 3) In this embodiment, as shown in FIG. 3, since the basic configuration and operation are common to those of Embodiment 1 or Embodiment 2, the same reference numerals are given to the common parts. The description will be omitted, and only the configuration that is a feature of the present embodiment will be described.

In the present embodiment, the current detector (the resistor 42 in the first embodiment) of the non-inductive shunt 10 (or 2) is used.
11 and the input winding 4 are formed of the same metal material. That is, since the resistance value of the current detection unit 11 and the resistance value of the input winding 4 of the transformer 3 change at the same rate with respect to the change in the ambient temperature, the variation in the characteristics caused by the temperature change of the resistance is canceled out, and the temperature characteristic is reduced. Can be improved.

(Embodiment 4) In this embodiment, as shown in FIG. 4, the basic configuration and operation are common to those of Embodiment 1, and the common parts are denoted by the same reference numerals and their description is omitted. Only the configuration of the magnetic detection means 6 which is a feature of the present embodiment will be described.

The magnetic detecting means 6 in this embodiment comprises a magnetic detecting element 6a disposed in a gap 3b provided in the core 3a of the transformer 3, and detects a detection voltage proportional to the magnetic fluxes φa, φb generated in the core 3a. Output to the magnetic balance circuit 7. Thus, when the measured current Ia flows through the measured current path 1, a magnetic flux φa is generated in the core 3a of the transformer 3, and
By outputting a detection voltage proportional to the magnetic flux φa from the magnetic detection element 6a to the magnetic balance circuit 7, the measured current Ia can be measured based on the voltage drop of the detection resistor Rs, as in the first embodiment.

Here, when a Hall element is used as the magnetic detection element 6a, there is an advantage that the cost of the magnetic detection element 6a can be reduced because there is a large quantity on the market. Also, when a magnetoresistive element (MR element) is used, a wider frequency range (for example,
0 to about 1 MHz). Furthermore, if a magnetic impedance element (MI element) is used,
Like the magnetoresistive element, the magnetic flux can be detected in a wide frequency range, and a minute magnetic flux (for example, about 10 ⁻¹⁰ [T]) can be detected. The magnetic sensing element 6a
The same effect as that of the magneto-impedance element can be obtained by using a flux gate sensor.

Thus, in this embodiment, the core 3a
Since the magnetic detecting means 6 can be configured simply by disposing the magnetic detecting element 6a in the gap 3b provided in the above, the magnetic flux generated in the core 3a can be detected with a simple configuration. In addition,
Non-inductive shunt 2 described in Embodiment 2
Needless to say, the same effect can be obtained even if 0 is set.

(Embodiment 5) In this embodiment, as shown in FIG. 5, the basic configuration and operation are common to those of Embodiments 1 and 4, and the common parts are denoted by the same reference numerals. The description will be omitted, and only the configuration that is a feature of the present embodiment will be described.

This embodiment is characterized in that the transformer 3 and the magnetic detecting element 6a are housed in a shield case 8 formed of a magnetic material into a substantially cylindrical shape. In addition, the lead wires of the input winding 4 and the compensating winding 5 and the output wire of the magnetic detection element 6a are drawn out through insertion holes 8b, 8b formed in the peripheral wall 8a.

In this embodiment, since the transformer 3 and the magnetic detection element 4 are housed in the shield case 8, the influence of external magnetic flux other than the magnetic flux generated by the measured current Ia on the magnetic detection element 6a. Can be eliminated, and the noise resistance performance against external noise can be improved. Needless to say, the same effect can be obtained even when the non-induction shunt 2 is used as the non-induction shunt 10 described in the second embodiment.

(Embodiment 6) In this embodiment, as shown in FIG. 6, the basic configuration and operation are common to those of Embodiment 1, and the common parts are denoted by the same reference numerals and description thereof is omitted. Only the configuration of the magnetic detection means 14 which is a feature of the present embodiment will be described.

The magnetic detecting means 14 in this embodiment is
An exciting winding 14a wound around the core 3a of the transformer 3,
An exciting unit 14b for supplying a current to the exciting winding 14a and an asymmetric detecting unit for detecting an asymmetry of a current waveform flowing through the exciting winding 14a are provided. The exciting means 14b outputs a sine wave AC voltage Vk = Vmsinωt (ω: each speed, t:
Time) is composed of an AC power supply or an oscillator. The asymmetry detecting means includes an exciting current detecting resistor Rx inserted between the exciting means 14b and the exciting winding 14a;
An asymmetry detection circuit 14c for detecting the asymmetry of the waveform of the voltage Vx generated at both ends of the exciting current detection resistor Rx.

FIG. 7 shows an example of the configuration of the asymmetrical detection circuit 14c. A positive half-wave rectifier 14d for half-wave rectifying the positive side of the voltage Vx across the exciting current detection resistor Rx, and a half-wave rectification for the negative side. Negative half-wave rectifier 14e and positive half-wave rectifier 14d
A positive-side peak hold unit 14f for holding the peak value of the output voltage of the negative side, a negative-side peak hold unit 14g for holding the peak value of the output voltage of the negative-side half-wave rectification unit 14e, and a positive-side and negative-side peak hold unit. And 14h and 14g, which add and amplify the outputs of 14f and 14g. Thus, if the waveform of the voltage Vx is symmetrical, the outputs of the positive and negative peak hold units 14f and 14g have the same absolute value and opposite signs, so that the output of the addition amplification unit 14h is zero. Becomes On the other hand, if the waveform of the voltage Vx between both ends is asymmetric, the peak hold units 14f and 14f on the positive side and the negative side
Since the absolute value of the output of g is different, a voltage (detection voltage) Vs of a level and a sign corresponding to the difference between the two is output from the addition amplification section 14h. In other words, the addition amplification unit 14h compares the peak values of the voltage waveforms every half cycle.

FIG. 8 schematically shows a magnetization curve of the core 3a, where Hs is a magnetic field required for magnetically saturating the core 3a, and Bs is a magnetic flux density. To simplify the explanation,
When the magnetic field H is in the range of −Hs <H <Hs, the differential magnetic permeability μ (= dB / dH) of the core 3a is constant at μa = Bs / Hs, and in the range of H <−Hs and Hs <H, μ = μ0 ( μ0
Is the magnetic permeability in vacuum).

When the measured current Ia is zero, the core 3a is excited only by the sinusoidal exciting current Ik supplied from the exciting means 14b to the exciting winding 14a as shown in FIG. Here, the output voltage Vk of the exciting means 14b is set to a value such that the core 3a does not become magnetically saturated when the measured current Ia is zero. In this state, the excitation winding 14
Both the exciting current Ik flowing through a and the voltage Vx across the exciting current detecting resistor Rx have a positive and negative symmetric sine wave similar to the waveform of the output voltage Vk. At this time, the magnetic field H of the core 3a temporally changes in the range of -Ho <H <Ho. Ho is determined by the output voltage Vk of the exciting means 14b, the number of turns and winding resistance of the exciting winding 14a, the shape of the core 3a, and the internal impedance of the exciting means 14b.

On the other hand, when the current to be measured Ia flows through the current to be measured 1 and the current to be measured Ia flows, the input current Ic flows to the input winding 4 and
Due to this input current Ic, the core 3a causes Hc = N1 · Ic
/ L (N1: the number of turns of the input winding 4, L: the magnetic path length of the core 3a). Here, Hc + Ho> H
When s is reached, the waveforms of the exciting current Ik and the voltage Vx across the exciting current detecting resistor Rx both deviate from the sine wave, resulting in a positive and negative asymmetric waveform as shown in FIG. As described above, the detection voltage Vs corresponding to the difference between the peak value on both the positive and negative sides of the voltage Vx between both ends, that is, the detection voltage Vs proportional to the measured current Ia is output from the asymmetrical detection circuit 14c to the magnetic balance circuit 7, and the first embodiment. As described above, the compensation current Ib is adjusted, and the measured current Ia can be measured. However, when the input current Ic that generates the magnetic field Hc that satisfies Hc−Ho> Hs flows, the core 3a is always magnetically saturated, and the waveform of the exciting current Ik and the voltage Vx between both ends becomes a sine wave having positive and negative symmetry.

In this embodiment, the transformer 3
Magnetic detecting means 14 capable of detecting the magnetic flux of the core 3a with a simple configuration without increasing the size of the magnetic head. Further, since there is no need to provide the core 3a with the gap 3b for disposing the magnetic sensing element 6a as in the fourth or fifth embodiment, the shield case is hardly affected by an external magnetic field, as in the fifth embodiment. 8 is not required, and thus there is an advantage that the size and cost can be reduced. In this embodiment, the direct current to be measured Ia can be measured.
If the frequency is lower than the frequency of the output voltage Vk, the AC measured current Ia can also be detected. It should be noted that the smaller the value of Hs of the core 3a, the larger the ratio of the change of the magnetic flux to the change of the current flowing through the winding, so that the measurement sensitivity of the measured current Ia can be improved.

(Embodiment 7) In this embodiment, as shown in FIG. 11, the basic configuration and operation are common to those of Embodiments 1 and 6, and the common parts are denoted by the same reference numerals. The description will be omitted, and only the configuration that is a feature of the present embodiment will be described.

Generally, a limiting resistor Rw (for example, an internal resistance of the exciting means 14b) for limiting the exciting current Ik is required between the exciting means 14b and the exciting winding 14a. At this time, when the voltage across the excitation winding 14a is set to the detection voltage Vx, the change with respect to the measured current Ia becomes sharper than when the voltage across the limiting resistor Rw is set to the detection voltage Vx, as in the sixth embodiment. The sensitivity is improved. Therefore, the present embodiment is characterized in that the voltage across the excitation winding 14a is input to the asymmetrical detection circuit 14c as shown in FIG. The operation of each unit including the asymmetrical detection circuit 14c is common to the first and sixth embodiments, and thus the description is omitted.

According to the present embodiment, there is an advantage that the detection sensitivity can be improved as compared with the magnetic detection means 14 of the sixth embodiment.

(Embodiment 8) In this embodiment, as shown in FIG. 12, the basic configuration and operation are common to those of Embodiments 1 and 6, and the common parts are denoted by the same reference numerals. The description will be omitted, and only the asymmetric detection circuit 15 of the magnetic detection means 14 which is a feature of the present embodiment will be described.

The asymmetric detection circuit 15 in the present embodiment
Is a reference waveform output unit 15a that outputs a sine-wave reference waveform voltage at a stage preceding the positive half-wave rectification unit 14d and the negative half-wave rectification unit 14e of the asymmetrical detection circuit 14c according to the sixth embodiment.
And a phase adjusting unit 15b for adjusting the phase of the detection voltage Vx of the exciting current Ik to match the phase of the reference waveform voltage.
An amplitude adjuster 15c for adjusting the amplitude of the detection voltage Vx to match the amplitude of the reference waveform voltage; and a differential amplifier for differentially amplifying the detection voltage Vx ′ output from the amplitude adjuster 15c and the reference waveform voltage. It is characterized in that an amplifying unit 15d is provided. Here, since the detection voltage Vx has an amplitude close to the output voltage Vk of the exciting means 14b, it may not be possible to directly differentially amplify the detection voltage Vx depending on the level of the output voltage Vk. By adjusting the phase and the amplitude by the adjusting unit 15b and the amplitude adjusting unit 15c, the detection voltage Vx can be differentially amplified regardless of the level of the output voltage Vk. Note that the phase adjuster 15b and the amplitude adjuster 15c can be realized by using a conventionally known technique, and a detailed description thereof will be omitted.

As compared with the case where the asymmetry is directly detected from the detection voltage Vx, the difference from the reference waveform voltage is once amplified and the asymmetry is detected based on the difference. The detection sensitivity of the means 14 can be improved. Note that the magnetic detection means 14 of the present embodiment can be applied to any of the configurations of the sixth and seventh embodiments.

(Embodiment 9) In this embodiment, as shown in FIG. 13, the basic configuration and operation are common to Embodiment 1, and the common parts are denoted by the same reference numerals and description thereof is omitted. Only the configuration of the magnetic detection means 16 which is a feature of the present embodiment will be described.

The magnetic detecting means 16 in this embodiment is
An exciting winding 16a wound around the core 3a of the transformer 3,
An exciting means 16b for supplying a current to the exciting winding 16a, a detecting winding 16c wound around the core 3a of the transformer 3 and having a larger number of turns than the exciting winding 16a, and a voltage waveform generated between both ends of the detecting winding 16c. Asymmetry detection circuit 1 for detecting asymmetry
6d. However, the excitation means 16b
The configuration and operation of the asymmetrical detection circuit 16d are described in Embodiment 6.
Or, since they are common to the excitation means 14b and the asymmetric detection circuit 14c in the eighth embodiment, the description is omitted.

When the exciting winding 16a is excited by the exciting means 16a, a voltage (detected voltage) is applied to the detecting winding 16c in accordance with the turn ratio between the exciting winding 16a and the detecting winding 16c.
Vx occurs. Thus, the sensitivity can be improved by increasing the detection voltage Vx input to the asymmetric detection circuit 16d.

(Embodiment 10) By the way, the magnetization curves of many magnetic materials change gradually as shown in FIG. 17 when the excitation current is plotted on the horizontal axis and the magnetic flux is plotted on the vertical axis. When the core 30 having a shape (for example, rectangular frame shape) having a uniform cross-sectional area as shown in FIG. 16 is formed, the exciting current (or exciting voltage) in the magnetic detecting means 14 and 16 is formed.
And the asymmetry of the detected current may not be clear.

Therefore, the present embodiment is characterized in that the core 3a 'is formed in a shape in which the cross-sectional area changes in a part as shown in FIG. 14, and other structures and operations are the same as those of the first and second embodiments. Illustration and description are omitted because they are common to the sixth embodiment.

As shown in FIG. 14, a rectangular frame-shaped core 3a '
By reducing the partial cross-sectional area on one side of
As shown in FIG. 15, the change in the magnetization curve of the core 3a 'can be sharpened. That is, the core 3 having a uniform sectional area
Since the change in the exciting current or the detected current can be detected with higher sensitivity than in the case where a is used, the measurement sensitivity of the current to be measured can be improved.

(Embodiment 11) In order to improve the detection sensitivity, it is desirable to use a magnetic material having a high magnetic permeability for forming the core 3a. However, if the magnetic permeability is too high, the core 3a becomes magnetically saturated. As a result, the measured current Ia cannot be measured.

Therefore, in the present embodiment, as shown in FIG. 18, cores 3d, 3e, and 3f made of plural kinds of magnetic materials having different magnetization characteristics are laminated to form the core 3a 'of the transformer 3. . Other configurations and operations are the same as those of the first and sixth embodiments, so that illustration and description are omitted.

As described above, the laminated core 3a '
Is used, magnetic saturation of the core 3a 'hardly occurs, so that a wide range of magnetic flux can be detected, and as a result, the detection range of the measured current Ia can be expanded.

(Embodiment 12) In this embodiment, as shown in FIG. 19, the basic configuration and operation are common to Embodiments 1 and 6, and the same reference numerals are given to the common parts. The description will be omitted, and only the configuration that is a feature of the present embodiment will be described.

This embodiment is different from the sixth embodiment in that the core 3
a core 17a formed of a magnetic material different from that of the input winding 4 and an input winding 4 'connected in series to the input winding 4;
This is characterized in that a transformer 17 is added in which a compensation winding 5 'connected in series with the excitation winding 14a and an excitation winding 14a' connected in series with the excitation winding 14a are wound around a core 17a.

As described in the eleventh embodiment, when the core 3a is magnetically saturated, the measured current Ia cannot be measured.
In the configuration of the present embodiment, even if one of the two transformers 3 and 17 having the higher magnetic permeability is magnetically saturated, the measured current Ia can be measured if the other core is not magnetically saturated. is there.

In this embodiment, the cores 3a and 17a are formed of different magnetic materials as described above, and the input windings 4 and 4 'wound around the cores 3a and 17a, Since there are provided a plurality of transformers 3, 17 in which the windings 5, 5 'and the detection windings 14a, 14' are connected in series, even if one of the cores is magnetically saturated, as long as there is a core which is not magnetically saturated, the magnetic flux Can be detected, and the detection range of the measured current can be expanded. Note that the number of transformers is not limited to two, and the detection range can be expanded as the number of transformers increases.

[0070]

According to the first aspect of the present invention, there is provided a non-inductive shunt for shunting a measured current flowing in a measured current path, a transformer having an input winding connected between output terminals of the non-inductive shunt, and a transformer. Magnetic detecting means for detecting a magnetic flux generated in the core of
A compensating winding wound on the core of the transformer, a magnetic balance circuit for supplying a current to the compensating winding to cancel a change in magnetic flux generated in the core of the transformer according to the detection result of the magnetic detecting means, Since the compensation current detecting means for detecting the compensation current flowing in the line is provided, the compensation current flowing to the compensation winding by the magnetic balance circuit is proportional to the current to be measured. The measured current can be measured without penetrating the measured current path through the transformer core, and the current capacity of the measured current can be measured simply by changing the non-inductive shunt that shunts the measured current. And the shape of the current path to be measured can be easily accommodated. As a result, the current to be measured can be measured at a small size and at low cost regardless of the current capacity of the current to be measured and the shape of the current path to be measured. There is an effect that.

According to a second aspect of the present invention, in the non-inductive shunt, the direction of current flowing in a pair of opposing portions made of a metal material having a predetermined resistance value is opposite to the direction of the apexes. And a pair of terminal plates provided at the end of each of the opposing portions and connected to a current path to be measured. The terminal plate is made of a metal material with a lower resistance than the metal material of the current detector, thereby suppressing the generation of Joule heat in the terminal plate, miniaturizing the non-inductive shunt, and consequently miniaturizing the entire current measuring device. There is an effect that can be achieved.

According to the third aspect of the present invention, the input winding of the transformer is formed of the same metal material as the current detecting section.
In addition to the effects of the invention, the resistance value of the current detection unit and the resistance value of the input winding of the transformer change at the same rate with respect to the change in the ambient temperature. Thus, the temperature characteristics can be improved.

According to a fourth aspect of the present invention, in addition to the effect of the first, second, or third aspect, the magnetic detecting means comprises a magnetic detecting element provided in a gap provided in the core of the transformer. There is an effect that the magnetic flux generated in the core can be detected with a simple configuration.

According to a fifth aspect of the present invention, since a shield case formed of a magnetic material and accommodating a transformer is provided, in addition to the effect of the fourth aspect, an external magnetic flux other than the magnetic flux generated by the current to be measured is provided. Has an effect of improving the anti-noise performance against external noise.

According to the sixth aspect of the present invention, since the magnetic detecting element is formed of a Hall element, there is an effect that the cost of the magnetic detecting element can be reduced in addition to the effect of the fourth or fifth aspect.

According to the seventh aspect of the present invention, since the magnetic detecting element is composed of a magnetoresistive element, in addition to the effect of the fourth or fifth aspect, there is an effect that a magnetic flux in a wide frequency range can be detected.

According to the eighth aspect of the present invention, since the magnetic detecting element comprises a magnetic impedance element, in addition to the effect of the fourth or fifth aspect, it is possible to detect a minute magnetic flux in a wide frequency range. There is.

According to the ninth aspect of the present invention, since the magnetic detecting element comprises a flux gate sensor, in addition to the effect of the fourth or fifth aspect, an effect that a minute magnetic flux can be detected in a wide frequency range. There is.

According to a tenth aspect of the present invention, the magnetism detecting means includes: an exciting winding wound around a core of the transformer; an exciting means for supplying a current to the exciting winding; and an asymmetry of a current waveform flowing through the exciting winding. And asymmetric detection means for detecting
In addition to the effects of the first, second or third aspect of the invention, there is an effect that a magnetic flux generated in the core can be detected with a simple configuration.

According to an eleventh aspect of the present invention, the magnetic detecting means includes: an exciting winding wound around the core of the transformer; an exciting means for supplying a current to the exciting winding; and a voltage waveform generated between both ends of the exciting winding. And an asymmetry detecting means for detecting the asymmetry of (1), in addition to the effect of the invention of claim 1, 2, or 3,
The magnetic flux generated in the core can be detected with a simple configuration, and the detection sensitivity can be improved when the voltage at both ends of the exciting winding is larger than the exciting current flowing through the exciting winding.

According to a twelfth aspect of the present invention, the magnetism detecting means is an exciting winding wound around a transformer core, an exciting means for supplying a current to the exciting winding, and an exciting winding wound around the transformer core. In addition to the effect of the invention according to claim 1 or 2, there is provided a detection winding having a larger number of turns and an asymmetric detection means for detecting the asymmetry of the voltage waveform generated between both ends of the detection winding. In addition, the magnetic flux generated in the core can be detected with a simple configuration, and a voltage higher than the voltage applied to the excitation winding is generated in the detection winding, so that the detection sensitivity can be improved.

According to a thirteenth aspect of the present invention, the core of the transformer is formed in a shape having a partially variable cross-sectional area. In addition to the effects of the tenth, eleventh and twelfth aspects, the magnetic flux density of the core with respect to the magnetic field can be reduced. There is an effect that the change can be sharpened and the detection sensitivity can be improved.

According to a fourteenth aspect of the present invention, a plurality of types of magnetic materials are laminated to form a transformer core.
In addition to the effects of any one of the inventions of (1) to (13), there is an effect that the detection range can be expanded because the magnetic saturation of the core hardly occurs.

According to a fifteenth aspect of the present invention, there are provided a plurality of transformers each having a core formed of a different magnetic material, and having an input winding and a compensation winding wound around each core connected in series. In addition to the effects of any one of claims 10 to 13, magnetic flux can be detected as long as there is a core that is not magnetically saturated even if any core is magnetically saturated, and the detection range can be expanded. This has the effect of becoming

According to a sixteenth aspect of the present invention, the asymmetry detecting means comprises:
Since means for comparing the peak value of each half cycle of the current waveform or the voltage waveform is provided, in addition to the effect of any one of claims 10 to 15, the asymmetry of the voltage waveform can be detected with a simple configuration. There is an effect that can be.

According to a seventeenth aspect of the present invention, the asymmetry detecting means comprises:
Claims include: a difference output means for outputting a waveform proportional to a difference between a current waveform or a voltage waveform and a reference waveform; and a comparison means for comparing peak values of output waveforms of the difference output means for each half cycle. In addition to the effects of the invention of any one of Items 10 to 15, there is an effect that the asymmetry of the voltage waveform can be detected with a simple configuration and the detection sensitivity can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment.

FIG. 2 is a schematic configuration diagram of a second embodiment.

FIG. 3 is a schematic configuration diagram of a third embodiment.

FIG. 4 is a schematic configuration diagram of a fourth embodiment.

FIGS. 5A and 5B are schematic configuration diagrams of a fifth embodiment.

FIG. 6 is a schematic configuration diagram of a sixth embodiment.

FIG. 7 is a block diagram of the asymmetry detection circuit in the above.

FIG. 8 is an operation explanatory view of the above.

FIG. 9 is an operation explanatory view of the above.

FIG. 10 is an operation explanatory view of the above.

FIG. 11 is a schematic configuration diagram of a seventh embodiment.

FIG. 12 is a block diagram of the asymmetry detection circuit in the above.

FIG. 13 is a schematic configuration diagram of an eighth embodiment.

FIG. 14 is a schematic diagram of a transformer according to a ninth embodiment.

FIG. 15 is an explanatory diagram of the operation of the above.

FIG. 16 is a schematic diagram of a transformer in the comparative example.

FIG. 17 is an operation explanatory view of the above.

FIG. 18 is a schematic diagram of a transformer according to the tenth embodiment.

FIG. 19 is a schematic configuration diagram of an eleventh embodiment.

FIG. 20 is a side sectional view of a conventional coaxial resistor.

FIG. 21 is a schematic configuration diagram of another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current path to be measured 2 Non-inductive shunt 3 Transformer 4 Input winding 5 Compensation winding 6 Magnetic detection means 7 Magnetic balance circuit

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 2, 1999 (1999.6.2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0032

[Correction method] Change

[Correction contents]

Thus, the measured current Ia
Are supplied with electricity, the two opposing portions 11a, 11
Since a current flows in the direction a in the opposite direction to cancel the magnetic flux, the inductance of the non-inductive shunt 10 can be suppressed to a low value. Then, a voltage drop proportional to the measured current Ia occurs between the output terminals 10a and 10b , and the measured current Ia can be measured based on the voltage drop of the detection resistor Rs in the same manner as in the first embodiment.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Change

[Correction contents]

In this embodiment, the cores 3a and 17a are formed of different magnetic materials as described above, and the input windings 4 and 4 'wound around the cores 3a and 17a, Since there are provided a plurality of transformers 3 and 17 in which the windings 5 and 5 'and the detection windings 14a and 14a' are connected in series, even if one of the cores is magnetically saturated, as long as there is a core that is not magnetically saturated, the magnetic flux Can be detected, and the detection range of the measured current can be expanded. The number of transformers is 2
The detection range can be expanded as the number of transformers increases, instead of limiting the number of transformers.

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yoshiaki Kobe 1048 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd. F-term (reference) 2G025 AA05 AA17 AB01 AB02 AB04 AB16 AC04 EB02 EB04 2G035 AA01 AB01 AB05 AB07 AC03 AC13 AC21 AD19 AD54 AD66 5E081 AA02 AA18 CC30 GG03 GG06

Claims (17)

[Claims] A non-inductive shunt for shunting a current to be measured flowing in a current path to be measured, a transformer having an input winding connected between output terminals of the non-inductive shunt, and a magnetic flux generated in a core of the transformer. A magnetic detecting means for detecting, a compensation winding wound around a core of the transformer, and a current for canceling a change in magnetic flux generated in the core of the transformer according to a detection result of the magnetic detecting means is supplied to the compensation winding. A current measuring device comprising: a magnetic balance circuit; and a compensation current detecting means for detecting a compensation current flowing through a compensation winding. 2. The non-inductive shunt according to claim 1, wherein the direction of the current flowing through the pair of opposing portions is a U-shaped current formed by a metal material having a predetermined resistance value. 2. The current measuring device according to claim 1, further comprising: a current detecting unit having a path; and a pair of terminal plates provided at an end of each of the opposed parts and connected to a current path to be measured. 3. The current measuring device according to claim 2, wherein the input winding of the transformer is formed of the same metal material as the current detecting unit. 4. The current measuring device according to claim 1, wherein the magnetic detecting means comprises a magnetic detecting element disposed in a gap provided in a core of the transformer. 5. A shield case formed of a magnetic material and accommodating a transformer.
The current measuring device as described. 6. The current measuring device according to claim 4, wherein the magnetic detecting element comprises a Hall element. 7. The current measuring device according to claim 4, wherein the magnetic detecting element comprises a magnetoresistive element. 8. The current measuring device according to claim 4, wherein the magnetic detecting element comprises a magnetic impedance element. 9. The current measuring device according to claim 4, wherein the magnetic detecting element comprises a flux gate sensor. 10. A magnetism detecting means comprising: an exciting winding wound around a core of a transformer; an exciting means for supplying a current to the exciting winding; and an asymmetric detection detecting an asymmetry of a current waveform flowing through the exciting winding. 4. The current measuring device according to claim 1, wherein the current measuring device comprises: 11. A magnetism detecting means for detecting an asymmetry of a voltage waveform generated between both ends of an exciting winding wound around a core of a transformer, an exciting means for supplying a current to the exciting winding, and both ends of the exciting winding. 4. The current measuring device according to claim 1, further comprising: asymmetric detecting means for detecting the current. 12. The magnetism detecting means includes: an exciting winding wound around a core of the transformer; an exciting means for supplying current to the exciting winding; and a winding having a larger number of turns than the exciting winding wound on the core of the transformer. 4. The current measuring device according to claim 1, further comprising: a detection winding; and asymmetric detection means for detecting asymmetry of a voltage waveform generated between both ends of the detection winding. 13. The transformer core according to claim 10, wherein a part of the core of the transformer has a cross-sectional area that changes.
Or the current measuring device according to 11 or 12. 14. A transformer core formed by laminating a plurality of types of magnetic materials.
The current measuring device according to any one of the above. 15. A plurality of transformers having cores formed of different magnetic materials and comprising an input winding and a compensation winding wound around each core connected in series. The current measuring device according to claim 10. 16. The current measuring device according to claim 10, wherein the asymmetry detecting means includes means for comparing a peak value of the current waveform or the voltage waveform every half cycle. . 17. An asymmetry detecting means for comparing a difference output means for outputting a waveform proportional to a difference between a current waveform or a voltage waveform and a reference waveform with a peak value for each half cycle of an output waveform of the difference output means. The current measuring device according to any one of claims 10 to 15, comprising means.