JPH09257835A - Current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To meet detection of a large current without increasing the number of winds of a coil and a current thereof and, moreover, to attain miniaturization. SOLUTION: When a current Im flows through a conductor 1, a magnetic flux ϕ is generated in a ring core 2, a magnetic field is generated in a gap part 2a, a part thereof is impressed on a magnetoelectric element 3 and an electric signal Es corresponding to the strength of the magnetic field is outputted from the magnetoelectric element 3. A control part 9 supplies an exciting current Ic to an exciting winding 5 in accordance with this electric signal Es and a magnetic field generated in the exciting winding 5 so acts as to cancel the magnetic field impressed on the magnetoelectric element 3. Since the exciting current Ic is in proportion to the magnetic flux ϕ, the current Im flowing through the conductor 1 can be detected from the exciting current Ic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detecting device, and more particularly to a current detecting device for detecting a current flowing through a conductor penetrating an annular core.

[0002]

2. Description of the Related Art As this type of current detecting device, the one shown in FIG. 4 is used. In FIG. 4, the conductor 1 is arranged so as to penetrate the annular iron core 2, and the annular iron core 2 is provided with a void portion 2a. In the void portion 2a, a magnetoelectric element including a Hall element for converting a magnetic field into an electric signal is provided. The element 3 is provided. A coil (winding) 5 is wound around the annular core 2,
When the current Im flows through the conductor 1 as shown in the figure, a magnetic flux φ proportional to the current Im is excited in the annular core 2 as shown in the figure,
A magnetic field due to the magnetic flux φ is generated in the void 2a. Due to this magnetic field, an electric signal Es proportional to the strength of the magnetic flux φ is output from the magnetoelectric element 3. The amplifier 4 outputs an exciting current Ic proportional to the electric signal Es and supplies it to the series circuit of the coil 5 and the resistor 6. With this exciting current Ic, the coil 5 excites the magnetic flux φ ′ in the direction of canceling the magnetic flux φ as shown in the figure, the magnetic flux of the annular core 2 is reduced to φ−φ ′, and the magnetic field applied to the magnetoelectric element 3 is also reduced. In this case, assuming that the loop gain of the transmission path from the magnetic flux φ−φ ′ to the excitation magnetic flux φ ′ is A, (φ−φ ′) A = φ ′, and thus the magnetic flux φ of the annular core 2
The magnetic flux (φ−φ ′) is reduced to almost 1 / A, and when the amplification factor of the amplifier 4 is increased and the loop gain A is set to a large value, the excited magnetic flux φ ′ becomes almost the same value as the magnetic flux φ and follows the magnetic flux φ. Change. The magnetic flux φ is the current I flowing through the conductor 1.
The exciting magnetic flux φ ′ is proportional to m, the exciting magnetic flux φ ′ is proportional to the product of the exciting current Ic and the winding ratio N of the coil 5, and the exciting current Ic is proportional to the current Im flowing in the conductor 1. By multiplying the ratio N, the current Im flowing in the conductor 1 can be obtained. Therefore, the current Im flowing in the conductor 1 can be detected from the voltage drop V0 generated in the resistor 6.

[0003]

However, in the above-mentioned conventional current detecting device, when the current Im flowing through the conductor 1 increases, the exciting current Ic supplied to the coil 5 also increases, and the current capacity of the amplifier increases, resulting in power loss. And the temperature rises. If the number of turns of the coil is increased in order to reduce the exciting current Ic, the inductance increases, the coil becomes large, the detection response becomes slow, and the device becomes large. Occurs.

The present invention has been made in view of the above problems, and an object thereof is to provide a downsized current detection device which can detect a large current without increasing the number of turns of the coil and the current. To do.

[0005]

According to the present invention, there is provided a current detecting device, wherein when a magnetic field is applied, a magnetoelectric element that outputs an electric signal corresponding to the strength of the magnetic field and a canceling magnetic field in a direction that cancels the magnetic field. When a magnetic field is applied to the magnetoelectric element by arranging the exciting winding to be generated in the void portion of the annular iron core integrally, and the magnetic flux is generated in the annular iron core by the current flowing through the conductor passing through the annular iron core, A control unit for supplying an exciting current to the exciting winding in accordance with an electric signal output from the magnetoelectric element is provided, and a current flowing through the conductor is detected from the exciting current. (Claim 1) Furthermore, the control unit includes an amplifier that proportionally and integrally amplifies the electric signal and outputs it as an exciting current, and cancels a magnetic field applied to the magnetoelectric element by a canceling magnetic field generated in the exciting winding. (Claim 2) Further, the control section further comprises an A / D conversion means for converting the electric signal into a digital signal, a microcomputer for outputting a third digital signal based on the digital signal, and the third digital signal. To a third analog signal, and an amplifier that supplies an exciting current according to the electric signal based on the third analog signal. (Claim 3) Further, the control section includes D / A conversion means for detecting the exciting current as a voltage and converting the voltage (second analog signal) into a second digital signal, and the microcomputer is provided with A detection signal of the current flowing through the conductor is output based on the second digital signal. (Claim 4) Further, when a magnetic field is applied, a plurality of magnetoelectric elements having different detection sensitivities that output an electric signal corresponding to the strength of the magnetic field, and an excitation winding that generates a canceling magnetic field in a direction of canceling the magnetic field. A wire is integrally provided in the void portion of the annular core, and when a magnetic flux is generated in each magnetoelectric element by generating a magnetic flux in the annular core by a current flowing through a conductor passing through the annular core, any one of A control unit for supplying an exciting current to the exciting winding according to an electric signal output from the magnetoelectric element is provided, and a current flowing through the conductor is detected from the exciting current. (Claim 5) Further, the control unit includes a setting unit that determines a switching signal for designating one of the magnetoelectric elements, and a switching unit that outputs a selection signal and a magnification signal based on the switching signal. A switch unit that selectively outputs a detection signal of any one of a plurality of magnetoelectric elements having different detection sensitivities based on the selection signal, and an amplification that amplifies the detection signal of the magnetoelectric element selected based on the magnification signal. And an exciting current is supplied to the exciting winding on the basis of the output of the amplifying unit, and the loop gain is kept constant even when the magnetoelectric element is switched. (Claim 6) Further, the switching unit outputs the selection signal and the magnification signal based on the switching signal and outputs a second magnification signal, and the control unit outputs the detection signal of the excitation current to the first signal. Two
A second amplifier that amplifies based on the magnification signal and outputs as a detection signal of the current flowing through the conductor is provided, and the full scale range of the detection signal is changed according to the detection sensitivity of the selected magnetoelectric element. (Claim 7) Further, the magnetoelectric element, the excitation winding, and a temperature detector for detecting the ambient temperature of the magnetoelectric element are integrally provided in a void portion of the annular iron core, and the control unit controls the ambient temperature. The temperature compensation includes a function generator that outputs a temperature correction signal based on the detection signal, and a second amplifier that corrects the detection signal of the exciting current based on the temperature correction signal and outputs a detection signal of the current flowing through the conductor. I do. (Claim 8) Furthermore, the control unit outputs a temperature correction signal of any one of a plurality of magnetoelectric elements having different detection sensitivities based on the detection signal of the ambient temperature, and a function generator for exciting current. A second amplifier that corrects a detection signal based on the temperature correction signal and outputs a detection signal of a current flowing through the conductor,
Perform temperature compensation. (Claim 9) Furthermore, the control unit converts the electric signal output from any one of the plurality of magnetoelectric elements having different detection sensitivities into an A / D conversion means, and the digital signal. A microcomputer that outputs a third digital signal based on the above, D / A conversion means that converts the third digital signal into a third analog signal, and an exciting current corresponding to the electric signal based on the third analog signal. A supply amplifier is provided. (Claim 10) Further, the control unit detects the exciting current as a voltage, converts the voltage (second analog signal) into a second digital signal, and converts the temperature detection signal into a ninth digital signal. The microcomputer is provided with D / A conversion means, and outputs the detection signal of the current flowing through the conductor based on the second digital signal and the ninth digital signal. (Claim 11)

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment corresponding to claims 1 to 4 of a current detecting device according to the present invention. In the figure, in the void portion 2a of the annular iron core 2, a magnetoelectric element 3 including a Hall element or the like that outputs an electric signal according to the strength of the magnetic field.
Then, an exciting winding (coil) 5 for generating a canceling magnetic field for canceling the magnetic field applied to the magnetoelectric element 3 is wound around the magnetoelectric element 3 and integrally formed with a mold resin or the like. The amplifier 4 amplifies the electric signal Es output from the magnetoelectric element 3 and outputs a voltage signal E1. The amplifier 7 amplifies the voltage drop Vf generated in the resistor 6 and outputs a voltage signal E2. The A / D converter 8 converts the voltage (analog) signals E1 and E2 output from the amplifiers 4 and 7 into digital signals S1 and S2, respectively. Microcomputer 9
Is a digital signal S1 input from the A / D converter 8,
It processes S2 and outputs a digital signal S3 and a current detection signal S4. The D / A converter 10 converts the digital signal S3 supplied from the microcomputer 9 into a voltage (analog) signal E3. The amplifier 11 amplifies the voltage signal E3 and supplies the exciting current Ic to the coil 5. Others can be configured by the same as the conventional one (FIG. 5).

In the above structure, when the current Im flows in the conductor 1 and the magnetic flux φ proportional to the current Im is excited in the annular core 2, a magnetic field is generated in the void 2a of the annular core 2, and a part of the magnetic field is generated. Is added to the magnetoelectric element 3 and the magnetic flux φ is generated from the magnetoelectric element 3.
The electric signal Es corresponding to the strength of the is output. The electric signal Es is amplified by the amplifier 4, converted into the digital signal S1 by the A / D converter 8 and input to the microcomputer 9. The microcomputer 9 performs processing such as proportional integration on the basis of the digital signal S1 and outputs a digital signal S3, and an electric signal E3 corresponding to the strength of the magnetic flux φ via the D / A converter 10. The amplifier 11 amplifies the electric signal E3 and supplies the coil 5 with an exciting current Ic corresponding to the strength of the magnetic flux φ. When the exciting current Ic flows through the coil 5, a canceling magnetic field proportional to the exciting current Ic is generated from the coil 5 in the direction of canceling the magnetic field applied to the magnetoelectric element 3, and acts to reduce the magnetic field applied to the magnetoelectric element 3. By setting a large loop gain from the magnetic field applied to the magnetoelectric element 3 to the canceling magnetic field, the canceling magnetic field becomes substantially equal to the magnetic field generated by the magnetic flux φ, and the exciting current Ic is proportional to the current Im flowing in the conductor 1. Therefore, the microcomputer 9 obtains the exciting current Ic based on the digital signal S2 input as the voltage drop Vf generated in the resistor 6, multiplies the exciting current Ic by a constant determined by the turn ratio of the coil 5, and flows to the conductor 1. The current Im can be detected. According to the present embodiment, a part of the magnetic field generated in the void 2a by the magnetic flux φ of the annular core 2 is applied to the magnetoelectric element 3, and the canceling magnetic field acts so as to cancel only part of the magnetic field. The coil 5 can be made smaller. Moreover, since the inductance of the coil 5 is reduced, the detection response time can be shortened.

[0008] Claims 5 to 7 of the current detecting device according to the present invention
An embodiment corresponding to is shown in FIG. In this embodiment, a plurality of magnetoelectric elements having different detection sensitivities are provided as the magnetoelectric elements arranged in the void portion 2a of the annular iron core 2 so that the full scale range can be switched according to the application. 2 (a) shows a configuration example in the case of using two magnetoelectric elements. In the figure, 3a and 3b are magnetoelectric elements with different detection sensitivities, and 5 is a winding that surrounds the magnetoelectric elements 3a and 3b and is wound around to generate an offset magnetic field for canceling the magnetic field applied to the magnetoelectric elements 3a and 3b. coil)
Then, it is integrally formed with the magnetoelectric elements 3a and 3b by a molding resin or the like, and is disposed in the void portion 2a of the same annular core 2 as in FIG. 4a and 4b are amplifiers for amplifying electric signals output from the magnetoelectric elements 3a and 3b and outputting voltage signals E1a and E1b,
Reference numeral 8 is an A / D converter for converting the voltage (analog) signals E1a, E1b and E2 into digital signals S1a, S1b and S2,
Reference numeral 12 is a setting unit for outputting a switching signal S5 for switching the full scale range, and the microcomputer 9 controls the digital signals S1a, S1b, S2 and the switching signal S5.
Has a function of taking in the digital signal S3 and performing the processing shown in FIG. Others are the same as those in FIG. 1 and are denoted by the same reference numerals.

The range of compensating the proportional relationship between the magnetic field and the electric signal of the magnetoelectric element varies depending on the detection sensitivity. For example, when the magnetoelectric element 3a has high sensitivity and the magnetoelectric element 3b has low sensitivity, the magnetic field strength for compensating the conversion accuracy is high. The magnetic element 3a is smaller and the magnetic element 3b is larger. Therefore, conductor 1
The maximum value for compensating the detection accuracy of the current Im flowing in the magnetic element 3a is smaller and the maximum value is larger in the magnetic element 3b.
By switching the magnetoelectric element, it is possible to switch the full-scale range of current detection and compensate for detection accuracy.

In the above configuration, the switching signal S for selecting the smaller one of the full-scale ranges for current detection in the setting section 12
When 5 is set, the microcomputer 9 outputs the selection signal S6 from the switching unit 23 to close the switch 21 as shown in FIG. 2 (b), and the digital signal S1a from the magnetoelectric element 3a is sent to the amplification unit 24 as S1. input. At the same time, magnification signals S7 and S8 determined by the detection sensitivity of the magnetoelectric element 3a are output and input to the amplifiers 24 and 25. The amplification section 24 amplifies the signal S1 based on the magnification of the magnification signal S7 and outputs a signal S3 which becomes the exciting current Ic, and the amplification section 25 outputs the magnification signal S.
The signal S2 is amplified based on the multiplication factor of 8 to obtain the current detection signal S
The full scale range of 4 is adjusted to the maximum value that compensates the detection accuracy of the magnetoelectric element 3a. As a result, the loop gain for supplying the exciting current Ic can be set to a predetermined gain, a full-scale signal can be output with a small current, and the detection accuracy can be compensated.

When the setting unit 12 sets the switching signal S5 for selecting the one having a larger full-scale range for current detection, the microcomputer 9 outputs the selection signal S6 from the switching unit 23 to close the switch 22. Magnetoelectric element 3b
The digital signal S1b by S1 is input to the amplifier 24 as S1. At the same time, magnification signals S7 and S8 determined by the detection sensitivity of the magnetoelectric element 3b are output and input to the amplifiers 24 and 25. The amplification unit 24 outputs the signal S based on the magnification of the magnification signal S7.
The signal S3 that amplifies 1 and becomes the exciting current Ic is output, and the amplifying section 25 amplifies the signal S2 based on the magnification of the magnification signal S8 to compensate the detection accuracy of the magnetoelectric element 3a for the full scale range of the current detection signal S4. Adjust to the maximum value. As a result, the loop gain for supplying the exciting current Ic is set to a predetermined gain, and the detection response time can be made constant even if the detection sensitivity of the magnetoelectric element is switched, and a full-scale signal is output with a large current, The detection accuracy can be compensated. In this case, it goes without saying that the magnetic flux of the annular core 2 is not saturated by the full-scale current.

Claims 8 to 1 of the current detecting device according to the present invention
An embodiment corresponding to No. 1 is shown in FIG. This example is
This is an example of temperature compensation when the detection characteristics of the magnetoelectric element change depending on the ambient temperature. As shown in FIG. 3 (a), the magnetoelectric elements 3a and 3b and the coil 5 are
A temperature detector 13 for detecting the ambient temperature of the magnetoelectric element is provided,
These are integrally formed with a molding resin or the like and arranged in the same void 2a of the annular core 2 as in FIG. Temperature detector 13
The temperature detection signal output from the amplifier is amplified by the amplifier 14 into a voltage signal E4, which is converted into a digital signal S9 via the A / D converter 8 and input to the microcomputer 9. The microcomputer 9 uses the digital signal S1a,
S1b, S2, S9 and switching signal S5 are taken in, and FIG.
It has a function of outputting the digital signal S3 and the current detection signal S4 by performing the processing shown in FIG. Others are shown in Figure 2 (b)
And the same reference numerals are used.

In the above-mentioned structure, the switching unit 23 has the structure shown in FIG.
Similar to the case of (b), the selection signal S6 and the magnification signals S7 and S8 are output based on the switching signal S5 set by the setting unit 12, and either the switch 21 or 22 is closed based on the selection signal S6. Then, the detection signals S1a of the magnetoelectric elements 3a and 3b,
One of S1b is input to the amplifier 24 as S1.
The function generator 26 measures the temperature characteristics for each of the magnetoelectric elements 3a and 3b in advance and holds temperature compensation data for the ambient temperature for each of the magnetoelectric elements 3a and 3b, and the temperature for the magnetoelectric element designated by the selection signal S6. The compensation signal S10 is output based on the digital signal (temperature detection signal) S9. The amplification unit 24 amplifies the signal S1 based on the magnification of the magnification signal S7 and outputs the digital signal S3, and the amplification unit 25 amplifies the signal S2 based on the magnification of the magnification signal S8 to obtain the full scale range of the current detection signal S4. Is adjusted to the maximum value for compensating the detection accuracy of the selected magnetoelectric element, and the value amplified based on the temperature compensation signal S10 is multiplied by the correction magnification to perform temperature compensation. According to this embodiment, the detection accuracy can be compensated even when the ambient temperature changes.

[0014]

According to the current detecting device of the present invention, it is possible to cope with the detection of a large current without increasing the number of turns of the coil and the current, and it is possible to reduce the size, and when the maximum value of the detected current is switched. Can maintain a predetermined detection accuracy and can compensate the detection accuracy even when the ambient temperature changes.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment corresponding to claims 1 to 4 of a current detector of the present invention.

2A and 2B are diagrams showing an embodiment corresponding to claims 5 to 7 of the current detector of the present invention, wherein FIG. 2A is a configuration diagram and FIG. 2B is a configuration diagram of a main function of the microcomputer 9.

3A and 3B show an embodiment of the current detector of the present invention corresponding to claims 8 to 11, wherein FIG. 3A is a configuration diagram and FIG. 3B is a configuration diagram of a main function of a microcomputer 9.

FIG. 4 is a configuration diagram of a conventional current detector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Conductor 2 ... Annular iron core 2a ... Voids 3, 3a, 3b
... Magnetoelectric element 4, 4a, 4b, 7, 14 ... Amplifier 5 ... Excitation winding (coil) 6 ... Resistor 8 ... A / D converter 9 ... Microcomputer 10 ... D / A converter 11 ... Amplifier 12 ... Setting Part 13 ... Temperature detector 21, 22 ... Switch 23 ... Switching part 24, 25 ... Amplifying part 26 ... Function generating part

Claims (11)

[Claims] 1. A ring-shaped iron core integrally including a magnetoelectric element that outputs an electric signal corresponding to the strength of the magnetic field when a magnetic field is applied, and an excitation winding that generates a canceling magnetic field in a direction of canceling the magnetic field. When a magnetic flux is generated in the annular core by a current flowing through a conductor passing through the annular core and disposed in the void, and a magnetic field is applied to the magnetoelectric element, depending on an electric signal output from the magnetoelectric element. A current detecting device comprising a control unit for supplying an exciting current to the exciting winding, and detecting a current flowing through the conductor from the exciting current. 2. The current detection device according to claim 1,
The said control part is equipped with the amplifier which proportionally-integrally amplifies the said electric signal, and outputs it as an exciting current, The current detection apparatus characterized by canceling the magnetic field added to the said magnetoelectric element by the cancellation magnetic field which arises in the said excitation winding. 3. The current detection device according to claim 1,
The control unit includes an A / D conversion unit that converts the electric signal into a digital signal, and a microcomputer that outputs a third digital signal based on the digital signal.
A current detecting device comprising D / A converting means for converting the third digital signal into a third analog signal, and an amplifier for supplying an exciting current according to the electric signal based on the third analog signal. . 4. The current detection device according to claim 3,
The control section includes D / A conversion means for detecting the exciting current as a voltage and converting the voltage (second analog signal) into a second digital signal, and the microcomputer is based on the second digital signal. A current detection device, which outputs a detection signal of a current flowing through the conductor. 5. A plurality of magnetoelectric elements having different detection sensitivities for outputting an electric signal corresponding to the strength of the magnetic field when a magnetic field is applied, and an exciting winding for generating a canceling magnetic field in a direction of canceling the magnetic field. Is disposed in the void portion of the annular iron core as a unit, and when a magnetic flux is generated in each of the magnetoelectric elements by the magnetic flux generated in the annular iron core by the current flowing through the conductor passing through the annular iron core, any one of the magnetoelectric elements A current detecting device, comprising: a control unit that supplies an exciting current to the exciting winding in accordance with an electric signal output from the exciting coil, and detects a current flowing through the conductor from the exciting current. 6. The current detection device according to claim 5,
The control unit determines a switching signal for designating one of the magnetoelectric elements, a switching unit that outputs a selection signal and a magnification signal based on the switching signal, and a detection unit that detects based on the selection signal. A switch unit that selectively outputs a detection signal of any one of a plurality of magnetoelectric elements having different sensitivities, and an amplification unit that amplifies the detection signal of the magnetoelectric element selected based on the magnification signal, the amplification unit An exciting current is supplied to the exciting winding on the basis of the output of, and the loop gain is kept constant even if the magnetoelectric element is switched. 7. The current detecting device according to claim 6,
The switching unit outputs the selection signal and the magnification signal based on the switching signal and also outputs a second magnification signal, and the control unit amplifies the detection signal of the exciting current based on the second magnification signal. And a second amplifier for outputting as a detection signal of the current flowing through the conductor, and changing the full-scale range of the detection signal according to the detection sensitivity of the selected magnetoelectric element. 8. The current detecting device according to claim 1, wherein the magnetoelectric element, the excitation winding, and a temperature detector for detecting an ambient temperature of the magnetoelectric element are integrated into an annular core. The function generator that outputs a temperature correction signal based on the ambient temperature detection signal, and the excitation current detection signal that is corrected based on the temperature correction signal. A current detection device comprising a second amplifier that outputs a detection signal of a flowing current, and performing temperature compensation. 9. The current detection device according to claim 8,
The controller is a function generator that outputs a temperature correction signal of any one of a plurality of magnetoelectric elements having different detection sensitivities based on an ambient temperature detection signal, and an excitation current detection signal that is the temperature correction signal. A current detection device comprising a second amplifier that corrects the current based on the above, and outputs a detection signal of the current flowing through the conductor, and performs temperature compensation. 10. The current detection device according to claim 8, wherein the control unit converts an electric signal output from any one of a plurality of magnetoelectric elements having different detection sensitivities into a digital signal. D conversion means, a microcomputer that outputs a third digital signal based on this digital signal, D / A conversion means that converts this third digital signal into a third analog signal, and based on the third analog signal A current detecting device comprising an amplifier for supplying an exciting current according to the electric signal. 11. The current detecting device according to claim 8, wherein the control unit detects the exciting current as a voltage,
The microcomputer is provided with D / A conversion means for converting the voltage (second analog signal) into a second digital signal and also for converting the temperature detection signal into a ninth digital signal, and the microcomputer includes the second digital signal and the ninth digital signal. A current detection device, which outputs a detection signal of a current flowing through the conductor based on the signal.