JP2526549B2 - Current transformer - Google Patents

Description

The present invention relates to a current transformer (carrent transformer) used in, for example, an electronic overcurrent relay.

(B) Conventional technology Generally, when a current more than a predetermined value flows in the motor circuit,
There is an overcurrent relay that detects this and shuts off the circuit to protect the motor. In this overcurrent relay, a current transformer is used to detect that an overcurrent has flowed into the main circuit of the motor to be protected. A conventional current transformer used for this type of overcurrent relay has a thin strip-shaped iron core wound in a donut shape, and a core wire wound around the donut-shaped iron core.

(C) Problems to be solved by the invention.

The above-mentioned conventional current transformer requires time and effort for production, and the product is expensive. Therefore, if this is incorporated into an overcurrent relay, there is a problem that the cost of the entire overcurrent relay becomes high. In addition, the current transformer has a donut shape, and the conductor of the main circuit is passed through the center of the current transformer.Therefore, when the current transformer is attached to the printed circuit board, a hole for inserting the conductive wire is formed in the printed circuit board. There has been a problem that when the lead wire is passed through the printed board, if another electronic circuit part is mounted on the printed board, a current flowing through the lead wire causes induction noise or the like in the electronic circuit part.

In view of the above, an object of the present invention is to provide a current transformer that can be manufactured at low cost and that does not easily affect other electronic circuit parts even when a lead wire is inserted into a main circuit.

(D) Means and Actions for Solving Problems The current transformer of the present invention includes an iron core (4), a spool (2) in which the iron core is inserted in an axial hollow portion, and a spool. A core wire (3), a yoke (5) forming a closed magnetic path together with the iron core, and a gap (7) for inserting a primary conductor in the closed magnetic path, wherein both ends of the yoke or the iron core are provided. PCB mounting legs [(5d, 5e)
Or (4d, 4e)] is formed.

In this current transformer, both the iron core and the yoke can be easily manufactured, and the core wire only needs to be wound around the spool, so that it can be manufactured at low cost. Further, if either the yoke or the iron core is attached to the printed circuit board, it is possible to separate the gap through which the primary conductor wire is inserted from the electronic circuit portion, and it is possible to reduce the influence of induced noise due to the current flowing through the primary conductor wire.

(E) Examples The present invention will be specifically described below with reference to Examples.

<Embodiment 1> FIG. 1 is a sectional view of a current transformer showing an embodiment of the present invention. This current transformer 1 includes a spool 2 having an axial empty portion 2a.
A core wire 3 is wound around the core 2, and an iron core 4 is attached to the shaft hollow portion 2a of the spool 2. The iron core 4 is attached to a U-shaped yoke 5, and the iron core 4 and the yoke 5 form a closed magnetic circuit. Has been done. The yoke 5 is composed of leg pieces 5a and 5b and a connecting portion 5c.
The tip portions 5d and 5e of 5a and 5b are attached to the printed circuit board 6. Further, the yoke 5 is larger than the spool 2 in height, and forms a space 7 between the yoke 5 and the spool 2 through which a conductor of the main circuit can be inserted. To detect the current of the main circuit, if a conductor is passed through this air gap 7, the closed magnetic path formed by the iron core 4 and the yoke 5 and the current path will be linked, and the core wire 3
In addition, a current corresponding to the current flowing through the conducting wire can be obtained.

In order to facilitate the assembly of the current transformer of this embodiment,
As shown in FIG. 2, the iron core 4 is made up of three plate members 41, 41, 41,
Alternatively, the spool 2 may be pierced in the shaft empty portion 2a, and the tip projections 41a and 41b of the iron core may be press-fitted and fixed in the notches 5f provided in the leg pieces 5a and 5b of the yoke 5.

<Embodiment 2> The above-mentioned Embodiment 1 is effective when the conductor wire of the main circuit is passed in parallel to the printed circuit board, but if it is desired to pass the conductor wire in the direction orthogonal to the mounting plate, Three
The current transformer 11 shown in the figure may be used. This current transformer 11
The two leg pieces 5a and 5b of the yoke 5 are configured to be connected to each other by a connecting piece 5g which is vertical to the side of the both leg pieces. In this case, the space 7 is juxtaposed with the spool 2. Others are the same as those in FIG.

<Embodiment 3> As shown in FIG.
Is formed into a U shape composed of the leg pieces 4a, 4b and the connecting portion 4c,
The tip portions 4d and 4e of the leg pieces 4a and 4b are attached to the printed circuit board 6. The spool 2 around which the core wire 3 is wound is inserted into one of the leg pieces 4a of the iron core 4, and the yoke 5 is provided so as to bridge the tip end portions of the leg pieces 4a and 4b of the iron core 4. 4 and the yoke 5 form a closed magnetic circuit. In this current transformer, the conductor wire of the main circuit is inserted into the space 7 formed between the spool 2 and the connecting portion 4c of the iron core.

(F) Effect of the Invention According to the present invention, the core wire is wound around the spool, the iron core is inserted into the axial empty portion of the spool, and the closed magnetic path is formed by the iron core and the yoke. Since the void for inserting the secondary conductor is formed, the iron core, the yoke, the core wire, etc. can be manufactured at low cost and easily, and a low-cost current transformer can be manufactured. Moreover, since the current transformer mounting part and the conductor part can be separated from each other, even if a large current is applied to the conductor,
It is possible to avoid the occurrence of induction noise or the like in the electronic circuit unit. Further, since the printed circuit board mounting leg portions are formed at both ends of the yoke or the iron core, it is possible to directly mount the printed circuit board on the printed circuit board, and it is possible to reduce the cost of an electronic device having this current transformer.

[Brief description of drawings]

FIG. 1 is a sectional view showing a current transformer according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view showing a modified example of the current transformer, and FIG. 3 is a second embodiment. FIG. 4 is an exploded perspective view showing the current transformer, and FIG. 4 is a sectional view showing the current transformer of the third embodiment. 2: Spool, 2a: Axial part, 3: Core wire, 4: Iron core, 5: Yoke, 7: Air gap.

Claims (1)

(57) [Claims] 1. An iron core, a spool in which the iron core is inserted into an axial hollow portion, a core wire wound around the spool, a yoke forming a closed magnetic path together with the iron core, and a primary conducting wire in the closed magnetic path. A current transformer comprising an air gap for inserting a coil, wherein printed circuit board mounting legs are formed at both ends of the yoke or the iron core.