JPH07333258A - Optical current sensor apparatus - Google Patents

Abstract

PURPOSE:To prevent magnetic fluxes generated in a gap section of a horseshoe shaped ferromagnatic iron core from leaking from opposing faces forming the gap and to concentrate the magnetic fluxes to a magnetooptics crystal disposed at a central section of the gap of the iron core. CONSTITUTION:A leakage-preventing plate 102 made of a first thin plate of a ferromagnetic material is provided in an inner circular section of a horseshoe shaped ferromagnatic iron core 1. A gap distance between the end sections of the leakage-preventing plate 102 is greater than a thickness of a magnetooptics crystal. A thickness of the leakage-preventing plate 102 is preferably 0.5 mm or less. A magnetic flux passing auxiliary plate 104 made of a second thin plate of a ferromagnetic material is provided to each side faces of a polarizer and an analyzer in the vicinity of the magnetooptics crystal 6 for enhancing the sensitivity. As a result, it is possible to markedly enhance the detection sensitivity of current of a penetration conductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detector for use in electronic equipment and the like, and more particularly to a detector intended to carry out current detection by an optical method. The present invention relates to a configuration in which a magneto-optical crystal is installed as a sensing unit as a magnetic sensor in a horseshoe-shaped void of an iron core formed by cutting a part of a ring-shaped ferromagnetic material.

[0002]

2. Description of the Related Art Conventionally, in such a current detector, a method of changing a material of a ferromagnetic iron core used in a portion forming a magnetic circuit or changing a composition of a magneto-optical crystal installed in a void portion of the iron core is used. Then, the detection current range is expanded to obtain a voltage or a secondary current proportional to the magnitude of the through current, and the output signals of these are amplified by the amplifier circuit to detect the current.

FIG. 5 shows a conventional structure in which a horseshoe-shaped ferromagnetic iron core 1 and an optical sensor module 3 as a magnetic sensor installed in a void 2 of the iron core 1 are installed. The optical sensor module 3 is constructed by assembling an incident optical fiber 4, a polarizer 5, a magneto-optical crystal 6, an analyzer and a reflector 7, and an outgoing optical fiber 8 in order, and light passes through in that order.

There is a through wire 9 in the center of the horseshoe-shaped ferromagnetic iron core 1, and when a current flows, a magnetic field proportional to the current to be measured is generated in the void 2, and the magneto-optical crystal inserted in the void 2 causes the current to flow. It modulates light in proportion to its size.

[0005]

In order to achieve high sensitivity with this structure, it is necessary to use an iron core material having a high saturation magnetic flux density, to improve the material sensitivity of the magneto-optical crystal, and to reduce the distance of the void portion of the iron core. Then, a method of improving the strength of the magnetic field generated in the void portion can be considered.

In order to improve the sensitivity by selecting these iron core materials and magneto-optical crystal materials, it is effective to shorten the distance between the voids of the iron core and increase the generated magnetic field strength.

However, as shown in FIG. 6, an optical sensor module having a structure of a magneto-optical crystal and an optical component is inserted, so that there is a limit in shrinking the void portion. In particular, the sensor module serves as a light passage, and since it is made of a glass material, its strength is weak and it is necessary to insert it with a margin. Therefore, when the size of the optical component is determined, the distance of the void portion of the iron core is determined.

Therefore, in order to improve the sensitivity in addition to the reduction of the iron core material, the crystal material and the air gap distance, it is considered to increase the density of the magnetic field generated in the air gap portion, and how to prevent the magnetic flux leaking from the air gap portion. However, it is described in Japanese Patent Application Laid-Open No. 1-308970, etc. that the issue is how to increase the magnetic field strength in the central portion.

FIG. 7 shows a side view of the magnetic field lines 10 in the void portion 2 of the horseshoe-shaped ferromagnetic iron core 1. The magnetic force lines 10 run linearly at the centers of the facing surfaces 11 and 12 of the void portion 2 and bend slightly outward at the end portions of the surfaces to leak. Although the magneto-optical crystal 6 is installed in such a state of magnetic field lines, only the magnetic field lines in the central portion of the facing surfaces of the iron core 6 are crystallized.
, The magnetic field lines that are generated at the end of the relative surface and bend outwards do not act on the crystal 6.

The central portion of the void has a small leakage magnetic field and leaks toward the periphery, and the strength difference is 10 to 20%.

Therefore, if it is possible to prevent the lines of magnetic force bending outside the end portions of the relative surfaces, it is possible to further improve the sensitivity. Further, if the magnetic flux lines can be concentrated in the crystal portion even in the center of the void portion of the iron core, the sensitivity can be further improved.

[0012]

In order to solve the problems, according to the present invention, a magnetic flux leakage prevention plate is installed at a portion which does not interfere with the insertion of the magneto-optical crystal in the void portion of the iron core, so that a magnetic field can be more easily generated in the crystal. It is intended to do so.

In particular, in consideration of incorporating an optical sensor module in the iron core, a thin plate made of a ferromagnetic material which is the same as or about the same as the iron core is installed on the inner circumference of the iron core to form a magnetic flux leakage prevention plate. Make the gap narrower than the gap in the iron core.

The fixing of the thin plate and the iron core should not change after the assembly is completed. In addition, a thin plate of a ferromagnetic material similar to the iron core material is installed on the sides of the polarizer, analyzer and reflector, which are optical components installed on both sides in the light passage direction near the magneto-optical crystal installed in the void. It is also possible to guide the lines of magnetic force generated on the air bearing surface of the iron core to a more central portion by a thin plate and concentrate them on the crystal.

[0015]

[Function] The magnetic flux leakage prevention plate made of a thin ferromagnetic material plate is fixedly integrated with the inner circumference of the horseshoe-shaped ferromagnetic iron core, and the gap between the prevention plates is narrower than the gap of the iron core. A magneto-optical crystal is installed in the center of the.
With this configuration, the magnetic field lines leaking inward of the iron core are prevented, and the magnetic field can be concentrated on the crystal.

Further, a magnetic flux line running in the center of the iron core is crystallized by installing a flux passing auxiliary plate made of a thin plate made of a ferromagnetic material in the polarizer, analyzer and reflector part before and after the magneto-optical crystal installed in the iron core void. Can be focused on.

Thus, by installing a thin plate on the inner circumference of the iron core as a leakage prevention plate and using a magnetic flux concentrating plate for the sensor module polarizer, analyzer and reflector portion of the iron core void, The magnetic flux lines can be concentrated and the sensitivity can be increased even if the through current is small.

[0018]

The present invention will be described in detail below. First, a brief description of the optical current sensor will be given. The optical type current sensor utilizes the magneto-optical effect, and when light passes through the magneto-optical crystal, the crystal is changed and the light is modulated by the influence of the magnetic field generated in the surroundings. Since the change is proportional to the strength of the magnetic field, the current is converted and measured by measuring the magnetic field.

Specifically, referring to FIG. 5, a case 21 has a horseshoe-shaped ferromagnetic core 1 and an optical current sensor module 3 housed in a void 2 of the core. Further, optical fibers 4 and 8 for inputting and outputting light extend from a part of the module housing portion of the case 21. The electric wire 9 penetrates through the center of the case configured as described above, and the magnetic field generated in proportion to the current flowing through the electric wire 9 is concentrated in the void portion 2 of the iron core 1.

The present invention will be described in detail below. Figure 1
FIG. 3 shows an enlarged detailed view of the void portion of the horseshoe-shaped ferromagnetic iron core with the configuration of the present invention. The horseshoe-shaped ferromagnetic iron core 1 has a void portion 2 of a fixed size, and a photocurrent sensor module 3 composed of an optical component and a magneto-optical crystal is inserted into the void portion 2 in the direction of arrow 101 into the void. To be done. An electric wire 9 penetrates through the center of the iron core 1, and the current flowing inside the electric wire 9 is measured. Photocurrent sensor module 3
It is desirable that the fixed position does not change significantly in the optical output of the sensor even if there is a slight displacement in the approximate center of the void 2.

In this structure, the magnetic field strength generated in the void portion 2 can be increased by shortening the void distance of the iron core, but this is determined by the size of the module inserted in the void portion. According to the present invention, in this structure, the leakage prevention plate 102 made of the first ferromagnetic material thin plate is installed on the inner circumferential portion of the iron core 1 to prevent the magnetic flux from leaking to the inside of the iron core. The leakage prevention plates 102 are installed at equal distances from both sides of the void 2 of the iron core 1 and the void 2
A gap 103 of only a thin plate is formed in the central portion of the. The size of the gap 103 is made narrower than that of the void portion 2 of the iron core 1. The thin plate 102 installed on the inner circumference of the iron core 1 is the iron core 1.
The effect is exerted over the entire inner circumference of the above and even only in the vicinity of the void portion 2.

If the thickness of the leakage prevention plate made of the first ferromagnetic thin plate is thin, the accuracy of the gap between the prevention plates can be accurately configured.
As the plate thickness increases, the magnetic flux concentrates on the short surface of the leakage prevention plate, which rather weakens the magnetic field strength at the cut portion of the iron core. Therefore, it is effective that the thin plate leakage prevention plate has a thickness of 0.5 mm or less. Of course, the same effect can be obtained by stacking plates of 0.5 mm or less to have a desired plate thickness.

FIG. 2 shows, from the front of the iron core, a structure in which the leakage prevention plate 102 made of the first ferromagnetic thin plate is installed on the entire inner circumference of the iron core (the case is not shown). With this structure, the gap formed by the thin plate can be obtained by subtracting a value obtained by adding the adhesive thickness to the plate thickness of the thin plate to the desired gap size from the inner circumference of the iron core.

FIG. 3 is a detailed enlarged view of a sensor module portion according to another structure of the present invention. In the structure shown in FIG. 2, a second ferromagnetic material is provided near the optical parts of the sensor module to further improve the magnetic field strength. Magnetic flux passage auxiliary plate 10 by thin body plate
4 is provided so that the magnetic flux passes through a region closer to the magneto-optical crystal 6.

FIG. 4 is a view as seen from the direction of the input / output optical fiber of the optical sensor module, and the numbers in the figure are the same as those in FIG. A leak prevention plate 102 made of a first ferromagnetic thin plate is provided on the inner circumference of the iron core 1 with the optical sensor module 3 inserted in the void 2 of the iron core 1. A magnetic flux passage auxiliary plate 104 made of a second ferromagnetic thin plate on both surfaces perpendicular to the polarizer 5, the analyzer, and the penetrating electric wire (not shown in FIG. 4) of the cube mirror 7 which are the optical components constituting the optical sensor module 3. To provide. This magnetic flux passage auxiliary plate 104
The space 103 on both sides sandwiching the magneto-optical crystal is constructed so as to be separated from the thickness of the magneto-optical crystal 6. By doing so, the magnetic flux running on the cut surface of the iron core in the void portion 2 of the iron core 1 is guided to the magnetic flux passing auxiliary plate once inside the iron core so as to be concentrated and run on the other magnetic flux passing auxiliary plate that opposes. . The thickness of the second ferromagnetic thin plate is more effective when it is thin, and is preferably 0.3 mm or less.

In FIG. 4, a leakage prevention plate made of the first ferromagnetic thin plate and a magnetic flux passage auxiliary plate made of the second ferromagnetic thin plate are used.
The drawings in which three configurations are implemented and adopted are shown, but it is effective whether each invention is implemented alone or implemented.

In the present embodiment, the description has been made with only one through wire, but the same effect can be obtained in the case where all three-phase wires of a general distribution wire are penetrated together.

[0028]

The magnetic flux leakage prevention plate of the first ferromagnetic thin plate is installed on the inner circumference of the horseshoe-shaped ferromagnetic iron core of the present invention, so that the magnetic flux leaking from the void portion of the horseshoe-shaped iron core is installed. It is possible to direct the running direction of the magnetic lines of force between the prevention and leakage prevention plates to the center of the gap, and it is possible to improve the magnetic field strength to the optical current sensor installed in the gap.

Also, by installing the magnetic flux passage auxiliary plate by the second ferromagnetic thin plate in the vicinity of the optical parts of the optical current sensor of the present invention, the running direction of the magnetic force lines in the iron core void portion is set in the magneto-optical crystal direction. The magnetic field strength to the optical current sensor can be improved.

Due to these effects, a weak current flowing through the through wire can be detected with high sensitivity.

[Brief description of drawings]

FIG. 1 is a partially detailed enlarged view of a void portion of a horseshoe-shaped ferromagnetic core according to a first embodiment of the present invention.

FIG. 2 is a view from the front of the iron core with the configuration shown in FIG. 1, showing a state in which an optical current sensor is inserted in the void of the iron core.

FIG. 3 is a detailed enlarged view of an iron core void portion current sensor module portion in a second embodiment of the present invention.

FIG. 4 is a configuration diagram of the current sensor module from the light input / output side in the embodiment shown in FIG.

FIG. 5 is a block diagram of an optical current sensor that combines a conventional horseshoe-shaped iron core and an optical sensor module.

FIG. 6 is a side view of a conventional combination of a horseshoe-shaped iron core and an optical sensor module.

FIG. 7 is a diagram showing how magnetic lines of force are generated in the void portion of the iron core.

[Explanation of symbols]

1 Horseshoe-shaped ferromagnetic core 2 Void of horseshoe-shaped ferromagnetic core 3 Optical current sensor module 4 Light incident fiber to sensor module 5 Polarizer 6 Magneto-optical crystal 7 Analyzer 8 Light emission fiber from sensor module 9 Through wire 10 Magnetic force 11 and 12 Faces of voids of iron core facing each other 21 Case 101 Direction of inserting sensor module into void of iron core 102 Leakage prevention plate 103 made of first ferromagnetic thin plate installed on inner circumference of iron core 103 First Gap between leakage prevention plates made of ferromagnetic thin plate 104 Second magnetic flux passing auxiliary plate made of ferromagnetic thin plate

Claims (3)

[Claims] 1. An inner circumference of a horseshoe-shaped ferromagnetic iron core having voids, an enclosure formed by a first ferromagnetic thin plate is formed in the vicinity of a degree of integration or contact, and the iron core is provided between the end portions of the thin plate. The optical current sensor device is characterized in that the distance is narrower than the distance of the horseshoe-shaped air gap portion. 2. A magneto-optic crystal is installed in the void of a horseshoe-shaped ferromagnetic iron core having a void, and a second ferromagnetic thin plate is placed parallel to the light passage direction in an optical component near the crystal. An optical current sensor device characterized by the above. 3. A magneto-optic of an optical current sensor, wherein a first ferromagnetic thin plate is installed at a position close to the inner circumference of a horseshoe-shaped ferromagnetic iron core having an air gap, and the central part of the iron core is installed. The optical current sensor device according to claim 1 or 2, wherein a second ferromagnetic thin plate is installed in a gap in parallel with the light passage direction of the crystal so as to avoid the side surface of the magneto-optical crystal.