JPH09304445A - Photocurrent sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measurement value wherein linearity error is small in a wide dynamic range, by inserting a current sensor into core gap part of a core which a wire penetrates, and performing correction calculation process to the output value from the current sensor. SOLUTION: A sensor part 4 is provided with a ferromagnetic core 1 which a wire 2 penetrates, an optical magnetic field sensor 6 which is inserted into a core gap part 3 of the core 1, and an optical fiber 7 which carries the optical output of the sensor 6. A measuring part 5 is provided with a photo transducer 8 connected with one end of the optical fiber 7, an A/D converter 9 connected with the photo transducer 8, and a correction calculation processing part (CPU) 10 connected with the A/D converter 9. When a current flows through the wire 2, a magnetic field is generated, detected by the sensor 6, and converted to a light, which is outputted in the optical fiber 7. The light is converted to an electric signal by the photo transducer 8. The electric signal is subjected to A/D conversion 9, and inputted in the CPU 10 in which correction calculation process is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical current sensor device for inserting a current sensor into a core gap portion of a core through which an electric wire penetrates to measure a current flowing through the electric wire,
The present invention relates to a photocurrent sensor device capable of obtaining a measurement value with a small linearity error in a wide dynamic range by performing correction calculation.

[0002]

2. Description of the Related Art Generally, there is known a photocurrent sensor device in which a current sensor is inserted into a core gap of a core through which an electric wire penetrates to measure a current flowing through the electric wire.

[0003]

However, the magnetic permeability μ of the ferromagnetic material, which is the material of the core, does not always have a constant value, but changes depending on the strength of the magnetic field applied from the outside. Therefore, in a ferromagnetic material, a proportional relationship is not established between the magnetic field strength H and the magnetic flux density B, and the magnetic material has nonlinearity. If the nonlinearity of the magnetic flux density B with respect to the magnetic field strength H is relatively simple, it can be expressed mathematically, but the BH characteristic of an actual ferromagnetic material is as shown in FIG. It has a complicated shape. FIG. 7 shows a magnetization curve of a ferromagnetic material. Here, in the core part of the photocurrent sensor shown in FIG. 8, 1: ferromagnetic core 2: electric wire Hg: magnetic field of core gap part 3 (A / m) N: number of turns (turn) I: current (A) Ll Where: magnetic path length (m) Lg: gap length (m) μ _s : relative permeability, the magnetic field Hg of the core gap part 3 of the core 1 with a gap is given by the non-linear characteristic of the above-mentioned ferromagnetic material. Hg = (N · I) / {Ll [(Lg / Ll) + (1 / μ _s )]} [A / m] (1)

If Lg / Ll >> 1 / μ _s (2) holds in the above equation (1), the magnetic field Hg of the core gap portion 3 is Hg≈NI / Lg (A / m). It can be approximated as 3). However, in a low magnetic field where the above expression (2) is not satisfied, the above approximate expression (3) is not satisfied and the above expression (1) has a correct value. However, the relative permeability μ of the above formula (1) is
_{Since s} changes depending on the value of the applied magnetic field, the above (2)
The magnetic field Hg of the core gap portion 3 until the expression is established has non-linearity. Therefore, when a sensor is inserted into the core gap portion 3 to measure the current value of the electric wire 2, the above-mentioned expression (2) is satisfied in the conventional case in which the linearity can be suppressed within a certain accuracy range. It was designed to be used only within the range. Therefore, in order to insert the sensor into the core gap portion 3 and measure the current value with high accuracy, it can be used only in the range where the above equation (2) is satisfied, and the dynamic range becomes narrow. On the contrary, when trying to measure a low current in a low magnetic field, there is a problem that the non-linearity error becomes large. The present invention has been made in view of the above circumstances, and an object thereof is to provide a photocurrent sensor device capable of obtaining a measurement value with a small linearity error in a wide dynamic range by performing correction calculation. .

[0005]

To achieve the above object, the present invention provides a photocurrent sensor device for detecting a current flowing through an electric wire, wherein the core is penetrated by the electric wire and the core gap portion of the core is inserted. And a correction calculation processing unit that performs a correction calculation process on an output value from the current sensor and outputs the corrected value.
Another feature of the present invention is that the correction calculation processing means performs correction calculation processing on an output value from the current sensor so as to reduce a linearity error generated when a current flowing through the electric wire is low. Is.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments. FIG. 1 is a block diagram showing an embodiment of a photocurrent sensor device according to the present invention. As shown in FIG. 1, this photocurrent sensor device includes a sensor unit 4 and a measuring unit 5.
And consists of The sensor unit 4 is connected to the electric wire 2
A core 1 of a ferromagnetic material arranged so as to penetrate, a photomagnetic field sensor (current sensor) 6 inserted in a core gap portion 3 of the core 1, and an optical output from the photomagnetic field sensor 6 is conveyed. Optical fiber 7 for The measuring unit 5 is
An optical converter (O / O connected to one end of the optical fiber 7
E) 8 and A / D converter 9 connected to the optical converter 8
And a correction calculation processing unit (CPU) 10 connected to the A / D converter 9.

Next, the operation of the photocurrent sensor device will be described with reference to the flow chart of FIG. First, in step 100 of FIG. 2, when a current flows through the electric wire 2, a magnetic field is generated in the core gap portion 3 of the core 1, and in step 101, the magnetic field sensor 6 detects the magnetic field and converts it into light. And is output to the optical fiber 7. Then, in step 102, the light from the optical fiber 7 is converted into an electric signal by the optical converter 8, and then in step 103, the A / D
It is converted into a digital signal by the converter 9. Next, in step 104, the digital signal from the A / D converter 9 is input to the correction calculation processing unit (CPU) 10, and the following correction calculation processing is performed and output. That is, in the CPU 10, the corrected output value: T output value of the optical converter 8: M current value (including error): A (A = M / (262.26 / 6
0)) Output value at 60 A: 262.26 (mV) When correction coefficient: 0.045, T = M · [0.045 · (1 / A) +1] (4) The value T is obtained and output.

FIG. 3 shows an example of measured values before and after correction by the CPU 10 in the photocurrent sensor device, and FIG. 4 similarly shows input before and after correction by the CPU 10. It is a graph showing the change in linearity error with respect to the current, the solid line shows the one after correction,
The dotted line shows the one before correction. FIG. 5 is an enlarged graph showing the change in the linearity error with respect to the input current corrected by the CPU 10. FIG. 3, FIG. 4,
Further, as is clear from FIG. 5, especially when the input current is low (that is, when the core gap 3 has a low magnetic field), the linearity error is remarkable after the correction is completed as compared with before the correction is performed. You can see that it is decreasing. FIG. 6 shows an embodiment in which the photocurrent sensor device according to the present invention is applied when measuring three-phase currents. As shown in FIG. 6, this photocurrent sensor device includes a core 1 and an optical magnetic field sensor 6.
The optical sensor unit 4 having the optical fiber 7 and the optical fiber 7 is provided for each phase, and the optical converter 8 connected to the optical fiber 7 is also provided for each phase. Then, the output from the optical converter 8 for each of the three phases is input to the multiplexer (MUX) 11 to be combined, converted into a digital signal by the A / D converter 12, and input to the CPU 13. CP above
In U13, the correction calculation as shown in the above equation (4) is performed, and the active power and the reactive power are calculated based on the corrected values and output to the outside via the optical relay unit 14. It The CPU 13 is designed to detect and output a device abnormality.

[0009]

As described above, according to the present invention, since the correction value is calculated for the detection value in the photocurrent sensor device, the linearity error of the sensor is reduced, the dynamic range of the sensor is widened, and the core is widened. There are effects such as reducing the gap and improving the linearity error without changing the core material to a high magnetic permeability material.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a photocurrent sensor device according to the present invention.

FIG. 2 is an operation flowchart of the photocurrent sensor device shown in FIG.

FIG. 3 is a CPU of the photocurrent sensor device shown in FIG.
It is a figure which shows the example of a measured value before and after performing correction by.

FIG. 4 is a CPU of the photocurrent sensor device shown in FIG.
6 is a graph showing a change in linearity error with respect to an input current before and after correction by.

5 is a CPU of the photocurrent sensor device shown in FIG.
6 is a graph showing an enlarged change in linearity error with respect to an input current after correction by.

FIG. 6 is a configuration diagram showing another embodiment in which the photocurrent sensor device according to the present invention is applied when measuring three-phase currents.

FIG. 7 is a graph showing a magnetization curve of a ferromagnetic material.

FIG. 8 is a configuration diagram of a core portion of a photocurrent sensor.

[Explanation of symbols]

1 ... Ferromagnetic core, 2 ... Electric wire,
3 ... Core gap part, 4 ... Sensor part, 5 ... Measuring part, 6 ... Optical magnetic field sensor, 7 ... Optical fiber,
8 ... Optical converter (O / E), 9, 12 ... A / D converter,
10, 13 ... Correction calculation processing unit (CPU), 11 ... Multiplexer (MUX), 14 ... Optical relay unit,

Claims (2)

[Claims] 1. A photocurrent sensor device for detecting a current flowing through an electric wire, comprising: a core through which the electric wire penetrates; a current sensor inserted into a core gap portion of the core; and an output value from the current sensor. A photocurrent sensor device, comprising: a correction calculation processing unit that performs a correction calculation process and outputs the corrected calculation process. 2. The correction calculation processing means performs correction calculation processing on an output value from the current sensor so as to reduce a linearity error generated when a current flowing through the electric wire is low. The photocurrent sensor device according to claim 1.