JPH04315059A - Current detector - Google Patents

Abstract

PURPOSE:To enhance the adjustment or replacement workability of a magnetic field sensor to a large extent by making the magnetic field sensor incorporated in a core detachable and to prevent the lowering of detection accuracy caused by the large wall thickness of the resin coating the core. CONSTITUTION:In a current detector detecting the current flowing to an electric wire to be measured, a ring-shaped iron core 1 in which the electric wire to be measured is inserted, the coating resin 2 coating the iron core 1 so as to provide the cavity 8 communicating with the outside to the gap part 7 formed to the iron core 1 and the magnetic field sensor 3 inserted in the cavity 8 of the coating resin 2 from the outside to be fixed thereto in a freely detachable manner are mounted. Further, the wall thickness of the part corresponding to the inner peripheral surface of the core in the resin coating the whole of the iron core is made as thin as possible.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in current detectors for detecting current flowing through electric wires and the like.

0002

2. Description of the Related Art A magnetic field sensor type current detector for detecting current flowing in a conductor such as an electric wire is conventionally known as shown in FIG.

The current detector shown in this figure has an annular iron core 1 through which a wire to be measured (not shown) is inserted into a central hole.
01 and the secondary coil 1 wound around this iron core 101.
02 and each end 102a, 10 of this secondary coil 102.
2a and external cables 103, 103, a part of this connector 104 and iron core 10
It is equipped with a ring-shaped resin mold 105 that covers the entire surface of the primary and secondary coils 102, and by inserting the wire to be measured into the center hole of the resin mold 105, the wire to be measured flows into the iron core 101. A magnetic field corresponding to the current is generated, an electromotive current flows through the secondary coil 102, and this is output from the external cable 103 via the connector 104.

However, in the conventional current detector described above, since an electric wire is used as the external cable 103, there is a problem in that noise is superimposed on the current output from the external cable 103 due to electromagnetic noise.

Furthermore, when the electrical circuit to be measured is a high-voltage power transmission line, it is difficult to ensure dielectric strength between the current sensor and the power transmission line.

Therefore, as a means to solve such a problem, a part of the iron core 101 is cut out and a magnetic field sensor (not shown) is embedded therein, and the current value detected by the magnetic field sensor is converted into an optical signal and used to transmit the magnetic field. A current detector that outputs an output from an optical fiber connected to the sensor, a so-called photocurrent detector, has been developed, but in this photocurrent detector as well, the resin mold 105 is used as a magnetic field sensor, similar to the current detector shown in FIG. Since the magnetic field sensor was integrated with the iron core 101, workability was poor when it became necessary to adjust or replace the magnetic field sensor.

[0007] In addition, it is preferable for detection accuracy that the distance between the magnetic field sensor embedded in the notch of the iron core and the wire to be measured inserted into the central hole be as short as possible, and the inner diameter of the iron core should be measured. However, since the resin mold covering the iron core covers the entire outer surface including the inner peripheral surface of the core with a relatively thick wall thickness, the inner diameter of the iron core The peripheral surface and the wire to be measured face each other through a thick resin, and the magnetic flux density generated on the core side decreases, resulting in a decrease in detection accuracy.

[0008] In particular, since current detectors attached to power transmission lines detect large currents, they often use a heavy object of about 1 kg as a core. Therefore, the coating resin that protects such a core needs to have a thick structure with sufficient strength, which causes the above-mentioned problems.

[0009]

OBJECTS OF THE INVENTION In view of the above circumstances, the present invention makes it possible to greatly improve the workability of adjusting and replacing the magnetic field sensor by making the magnetic field sensor incorporated in the core removable. An object of the present invention is to provide a current detector that can prevent a decrease in detection accuracy caused by a large value.

0010

SUMMARY OF THE INVENTION In order to achieve the above object, a current detector according to the present invention detects a current flowing through a wire to be measured, the current detector having a C-shaped iron core through which the wire to be measured is inserted; an annular covering resin part that covers the iron core so that the gap part of the iron core becomes a cavity communicating with the outside; a resin arm part having an opening communicating with the cavity and protruding from the annular covering resin part; and a magnetic field sensor that is detachably inserted into the cavity through the opening of the resin arm, and the annular covering resin part is thinner on the inner peripheral surface side of the iron core, and the annular covering resin part is thinner on the inner peripheral surface side of the iron core, Further, the magnetic sensor includes a polarizer and a Faraday element, and includes means for guiding light input from two optical fibers to the other optical fiber via the magnetic sensor. The magnetic sensor is characterized in that the amount of light transmitted through the magnetic sensor is varied depending on the strength of the magnetic field generated in the gap portion of the iron core.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on embodiments shown in the drawings.

FIG. 1 is a partially exploded perspective view showing an embodiment of a current detector according to the present invention.

The current detector shown in this figure includes a C-shaped iron core 1 having a gap 7 in a part, a coating resin 2 covering the outer periphery of the iron core 1, and a resin coating 2 disposed within the gap 7 to adjust the magnetic flux density. It is equipped with a magnetic field sensor 3 for detection, a cable 4 for externally transmitting a signal corresponding to the magnetic flux density detected by the magnetic field sensor 3, and a fixing pin 5 for fixing the magnetic sensor in a gap 7. When an electric wire to be measured (not shown) is inserted into the central hole 6 formed in the central portion, a signal corresponding to the current flowing through the electric wire to be measured is outputted to the outside.

The iron core 1 has a gap 7 in a part, for example.
It is formed by laminating ring-shaped thin silicon steel plates having a 3-dimensional structure formed therein, and when the electric wire to be measured is inserted into the central hole 6, a magnetic flux is generated by the current flowing through the electric wire to be measured.

[0015] Furthermore, the coating resin 2 is arranged so that the thickness of the portion covering the inner circumferential surface of the iron core 1 is thin and
An annular covering resin part 9 is formed to have a cavity 8 in the gap 7 part of the iron core 1 so that the thickness of the part covering the part other than the inner circumferential surface of the iron core 1 is thicker, and communicates with the cavity 8. The arm part 10 has a rectangular cylindrical shape integrally projecting from the side surface of the annular covering resin part 9, and a pin insertion hole 11 is formed at a suitable position on the upper surface of the arm part 10. This pin insertion hole 11 is for inserting the magnetic field sensor 3 into the arm portion 10 and then press-fitting the stop pin 5 to hold down the outer surface 3a of the magnetic field sensor 3 and prevent it from falling off.

The magnetic field sensor 3 is connected to the opening 10a of the arm portion 10.
The sensor housing 12 is inserted into the gap 7 and placed in the gap 7.
and a magnetic field sensor main body (not shown) housed in the sensor housing 12, and measures the magnetic flux density in the gap 7 portion of the iron core 1, and transmits the measurement results to a cable connected to the magnetic sensor main body 13. Output from 4.

The magnetic sensor 3 may be an optical magnetic sensor comprising, for example, one or two polarizers and a Faraday element, and the cable may be an optical fiber.

That is, although not shown in the drawings, the structure is such that light guided from one of the two optical fibers is outputted to the other optical fiber via a polarizer and a Faraday element,
When the magnetic field generated in the iron core gap acts on the Faraday element, the rotation angle of the polarization plane of the Faraday element changes depending on the magnetic field strength.

Therefore, for example, if the polarization plane of the Faraday element and the transmission polarization plane of the polarizer are made to match when there is no magnetic field in the iron core gap, the laser beam will be affected by the magnetic field due to the current flowing through the electric wire. When the plane of polarization rotates in response to this, the amount of transmitted light decreases.

[0020] The current detector of the present invention can be attached to an electric wire by directly fitting it onto the power transmission line or by fixing it to an insulator that supports the electric wire to be measured.

As described above, in this embodiment, the iron core 1 is covered with the resin-made annular coating resin part 9, and the square cylindrical arm having the opening 10a communicating with the gap 7 of the ring-shaped iron core 1 is provided. A portion 10 is provided to protrude from the side wall of the annular coating resin portion in the outer diameter direction, and with the magnetic field sensor 3 inserted from the opening 10a of the arm portion 10 seated in the gap 7, the stop pin 5 is inserted into the pin insertion hole 11. Since the magnetic field sensor 3 is fixed at the center of the gap of the iron core 1 by inserting it into the core 1, it is easy to attach and detach the magnetic field sensor 3, which greatly improves work efficiency when adjusting and replacing the magnetic field sensor. . Further, since the optical fiber is protected by the arm portion 10, the mechanical load applied to the optical fiber can be reduced.

Furthermore, in the above-described embodiment, the thickness of the resin covering the inner peripheral surface of the iron core 1 is reduced.
In addition, since the coating resin 2 is formed so that the thickness of the resin covering the parts other than the inner circumferential surface (the outer circumferential surface and both upper and lower surfaces) is thick,
The current measurement sensitivity can be improved by making the gap between the central hole 6 inserted into the central hole 6 and the iron core 1 as small as possible, and the required strength of the coating resin 2 portion can be sufficiently ensured. can do.

[0023]

As explained above, according to the present invention, it is possible to obtain a resin mold structure that can ensure necessary and sufficient strength without reducing the current measurement sensitivity. Further, since the magnetic field sensor can be easily removed, work efficiency can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a partially exploded perspective view showing one embodiment of a current detector according to the present invention.

FIG. 2 is a perspective view showing an example of a conventionally known current detector.

[Explanation of symbols]

1 Iron core 2 Coated resin part 3 Magnetic field sensor 4 Optical fiber 5 Locking pin 7 Gap 8 Cavity

Claims (3)

[Claims] 1. A current detector for detecting a current flowing through an electric wire to be measured, comprising a C-shaped iron core through which the electric wire to be measured is inserted, and a gap portion between the iron core forming a cavity communicating with the outside. an annular covering resin part that covers the iron core; a resin arm part having an opening communicating with the hollow part and protruding from the annular covering resin part; and a resin arm part that can be detachably inserted into the hollow part from the opening of the resin arm part. A current detector comprising: a magnetic field sensor inserted therein; 2. The current detector according to claim 1, wherein the annular coating resin portion is formed thinly on the inner circumferential surface side of the iron core, and thickly formed on a portion other than the inner circumferential surface side. 3. The magnetic sensor includes a polarizer and a Faraday element, and includes means for guiding light input from two optical fibers to the other optical fiber via the magnetic sensor, and includes means for guiding light input from two optical fibers to the other optical fiber through the magnetic sensor. 2. The current detector according to claim 1, wherein the amount of light transmitted through said magnetic sensor is changed depending on the strength of the magnetic field.