JP2019009289A - Core for current-limiting reactor, current-limiting reactor and manufacturing method of core for current-limiting reactor - Google Patents

Abstract

To generate many eddy currents in a core for current-limiting reactor.SOLUTION: A core 10 is formed of a magnetic substance. Multiple embedded members 30 are embedded in the core 10. The embedded members 30 are formed of a material having an electrical resistivity lower than that of the magnetic substance. The embedded member 30 has a through hole penetrating from the first principal surface to a second principal surface facing the first principal surface. The embedded member 30 functions as a short circuit coil. When a current flowing to a coil wound around the core 10 for current-limiting reactor changes, magnetic flux Φm in the core 10 changes. At this time, eddy currents flow to individual embedded members 30. Magnetic flux is generated in a direction for restraining change of the magnetic flux Φm, by the eddy current. Consequently, the magnetic flux Φm is less likely to saturate, compared with the case where there is no embedded member 30. When a large voltage is applied abruptly, a current-limiting reactor using the core 10 increases the current of a coil (current of a DC cable way) rapidly to near a predetermined current value, and restrains increase of current when that current value is exceeded.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a current-limiting reactor core, a current-limiting reactor, and a method for manufacturing a current-limiting reactor core included in a current-limiting reactor that limits a current flowing through a DC circuit.

There is known a DC circuit breaker in which a contact provided with an electromagnetic trip device and a current limiting reactor are connected in series (for example, see Patent Document 1).
The trip device opens the contact when the current flowing through the DC circuit exceeds a predetermined current value. When the contact opens, the current is cut off.
In this current-limiting reactor, the main coil and the short-circuit coil are wound around a common core. The main coil is inserted in the DC circuit. The shorting coil is short-circuited at the beginning and end of winding. The main coil and the short-circuit coil are electromagnetically coupled. When a short-circuit accident occurs in the DC circuit, this current-limiting reactor increases the current in the DC circuit quickly to the vicinity of the predetermined current value at which the contact is opened by the trip device, and when the current value is exceeded, the current increases. Suppress.

Moreover, a transformer, a motor, a generator, etc. have a core (iron core) and a coil. The core is made of a magnetic steel plate, soft ferrite, iron powder, or the like.
When the core is placed in a changing magnetic field, an eddy current is generated in the core so as to prevent the magnetic flux from being changed, which is consumed as heat and becomes a loss (iron loss). In applications such as transformers, motors, and generators, it is desirable to suppress eddy currents in order to prevent heat generation. Therefore, for example, a powder magnetic core obtained by compressing and molding a ferromagnetic powder having an insulating film on the surface is used as a material for the core (see, for example, Non-Patent Document 1). The eddy current between the particles can be suppressed by the insulating coating formed on the surface of the particle.

JP 2006-181686 A

Hiroyuki Mitani, “Expectations for Next-Generation Magnetic Materials“ Magnetic Iron Powder ”, Kobe Steel Technical Report, 2015, Vol. 65, no. 2, pp. 12-15.

In the current-limiting reactor described in Patent Document 1, when a large voltage is suddenly applied and the magnetic field generated by the main coil increases as in the case of a short circuit accident in a DC circuit, an eddy current is generated in the short circuit coil. Due to the magnetic field generated by this eddy current, the current in the main coil (current in the DC circuit) increases rapidly to a predetermined current value, and when the current value is exceeded, the increase in current is suppressed.
However, if a short circuit coil is externally attached to the core of the current limiting reactor, the shape of the current limiting reactor is limited, and the manufacturing cost thereof increases.
Further, unlike cores used in applications such as transformers, motors, and generators, it is desirable that the cores included in the current limiting reactor generate more eddy currents.

  The objective of this invention is providing the manufacturing method of the core for current limiting reactors, the core for current limiting reactors, and the core for current limiting reactors which can produce many eddy currents.

In order to achieve the above object, the core for a current limiting reactor of the present invention is:
A core for a current-limiting reactor formed of a magnetic material,
A plurality of embedded members made of a material having a lower electrical resistivity than the magnetic body, and having a through-hole penetrating from the first main surface to the second main surface facing the first main surface The embedded member is embedded,
It is characterized by that.

Preferably, the core for a current-limiting reactor of the present invention is
The magnetic body is iron-based,
The embedded member is formed of gold, silver, copper, or aluminum;
It is characterized by that.

In addition, the current limiting reactor of the present invention is
The core for the current-limiting reactor described above,
A coil wound around the core for the current-limiting reactor,
With
A magnetic field generated when a current flows through the coil is linked to the first main surface and the second main surface of the embedded member;
It is characterized by that.

Moreover, the manufacturing method of the core for current-limiting reactors of the present invention is as follows:
A second main surface which is an embedded member made of a powder containing magnetic particles made of a material having an electric resistivity lower than that of the magnetic material and which faces the first main surface from the first main surface. A process of putting a plurality of embedding members having through holes penetrating into the mold while embedding them in the powder; and
A step of compressing and molding the powder in which the embedding member is embedded;
It is characterized by providing.

  According to the present invention, many eddy currents can be generated in the core for a current-limiting reactor.

It is a perspective view showing an example of a current limiting reactor concerning an embodiment of the present invention. It is the sectional view on the AA line of the core of FIG. It is a longitudinal cross-sectional view of the core of FIG. It is a figure which shows an example of the eddy current which arises in an embedding member, and the magnetic flux which arises by it. FIG. 4A shows an example of an annular embedding member. FIG. 4B shows an example of a rectangular embedded member. It is a figure which shows an example of the manufacturing method of a core.

  Hereinafter, the manufacturing method of the core for current limiting reactors, the current limiting reactor, and the core for current limiting reactors which concerns on embodiment of this invention is demonstrated in detail, referring drawings. In all the drawings for explaining the embodiments, common constituent elements are denoted by the same reference numerals, and repeated explanation is omitted.

FIG. 1 shows an example of the structure of a current-limiting reactor 1 according to the first embodiment of the present invention. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a longitudinal sectional view of the core of FIG. 2 and 3 show an example of the internal structure of the core.
The current limiting reactor 1 has a core 10 and a coil 20.
The coil 20 is wound around the core 10. One end and the other end of the coil 20 are connected to the terminal T1 and the terminal T2, respectively. The coil 20 is inserted into the DC circuit, and a current i flows from the terminal T1 to the terminal T2, for example.

The core 10 is made of a magnetic material. The core 10 includes a yoke Y1, a yoke Y2, a leg part P1, and a leg part P2. The yoke Y1 and the yoke Y2 face each other. The leg P1 connects the left end of the yoke Y1 and the left end of the yoke Y2. The leg P2 connects the right end of the yoke Y1 and the right end of the yoke Y2.
The coil 20 is wound around a part thereof, for example, the leg P1.

As shown in FIGS. 2 and 3, the core 10 has a large number of small embedded members 30 embedded therein.
As shown in FIG. 4, the embedding member 30 is, for example, an annular or rectangular member. The embedding member 30 has a first main surface 31 and a second main surface 32 facing it, and has a predetermined thickness. The embedded member 30 has a through hole 33 that penetrates from the first main surface 31 to the second main surface 32. The embedding member 30 is made of a material having a low electrical resistivity such as gold, silver, copper, or aluminum. The embedded member 30 may be a ring made of a metal wire such as gold, silver, copper, or aluminum.

The embedded member 30 functions as a short circuit coil. As shown in FIGS. 1 and 3, when a current i flows through the coil 20, a magnetic flux Φm is generated inside the core 10. As shown in FIG. 4, the magnetic field Φm is linked to the first main surface 31 and the second main surface 32 of each embedded member 30. At this time, it is desirable that the magnetic field Φm interlinks with the first main surface 31 and / or the second main surface 32 of the embedded member 30 at an angle as close to perpendicular as possible.
When the current i of the coil 20 changes (that is, the magnetic flux Φm changes), the eddy current ie flows through the embedded member 30. Since the electric resistance of the embedded member 30 is smaller than that of the magnetic body forming the core 10, a large eddy current ie flows. The eddy current ie generates a magnetic flux Φe in a direction that suppresses the change of the magnetic flux Φm. For this reason, compared with the case where there is no embedding member 30, magnetic flux (PHI) m becomes difficult to saturate.

The position where the embedded member 30 is embedded and the density thereof are adjusted according to the degree of suppression of the magnetic flux Φm in the core 10. For example, as shown in FIG. 3, the embedded member 30 may be embedded in the yoke Y1, the yoke Y2, and the leg part P2 other than the leg part P1 around which the coil 20 is wound. Further, the embedding member 30 may be embedded only in the leg part P2 facing the leg part P1. The embedded member 30 may be embedded in all of the yoke Y1, the yoke Y2, the leg part P1, and the leg part P2.
Further, the degree of freedom of the shape of the core 10 can be increased by making the outer shape of the embedded member 30 relatively small.

The core 10 is manufactured by embedding a large number of embedding members 11 in a powder containing magnetic particles such as iron powder, and compressing and molding the embedding member 11.
The magnetic powder used in the manufacture of the core 10 may be one in which an insulating coating is formed on the surface of the particles, but is preferably one in which no insulating coating is formed on the surface of the particles. In the core 10 manufactured using particles having no insulating coating formed on the surface, eddy currents are also generated between the particles.

  The powder material used for manufacturing the core 10 is preferably an iron-based magnetic material. For example, pure iron, iron-silicon alloy, iron-nitrogen alloy, iron-nickel alloy, iron-carbon alloy, iron-boron alloy, iron-cobalt alloy, iron-phosphorus alloy, iron-nickel -The core 10 can be manufactured using powders, such as a cobalt type alloy and an iron-aluminum-silicon type alloy (Sendust alloy), an iron amorphous type material, and a fine crystal material.

FIG. 5 shows an example of a method for manufacturing the core 10.
When manufacturing the core 10, first, a powder containing magnetic particles is put into a mold while a plurality of embedded members 30 are embedded therein (S1). Here, as for the particle | grains contained in powder, what the insulating film is not formed in the surface is desirable. Next, the powder in which the embedding member 30 is embedded is compressed with a press machine and molded (S2).
After the core 10 is compressed and molded, the embedded member 30 is deformed. As long as it is closed, there is no problem.
Further, in order to prevent the embedded member 30 from being deformed during compression / molding, the yoke Y1, the yoke Y2, the leg part P1, and the leg part P2 are separately manufactured by compression / molding as square pillars, and thereafter four pieces are formed. It is good also as joining a prism to a rectangle. In this case, a force is applied to the first main surface 31 and the second main surface 32 of the embedding member 30 perpendicularly by applying a force along the longitudinal direction of the prism during compression and molding. Deformation of the insert member 30 can be prevented.

  In addition, although the example of the rectangular core 10 was shown in embodiment mentioned above, it is not restricted to this, The core 10 may be other shapes, such as a rod shape and a cyclic | annular form. In the above-described embodiment, the example of the annular or rectangular embedded member 30 is shown. However, the present invention is not limited to this, and the embedded member 30 may have other shapes as long as it has an eddy current. .

According to the present invention, a large number of short-circuit coils (embedded members) are arranged in the core for the current-limiting reactor, so that many eddy currents are generated. Furthermore, an eddy current is also generated between particles in a core manufactured using particles having no insulating coating formed on the surface. Therefore, the current-limiting reactor core according to the present invention has a coil current (DC circuit current) when a large voltage is suddenly applied as in the case of a DC circuit short-circuit accident without externally attaching a short-circuit coil. Can be rapidly increased to near a predetermined current value, and when the current value is exceeded, an increase in current can be suppressed.
Moreover, since many short-circuit coils are arrange | positioned in parallel, the frequency characteristic of the core for current limiting reactors improves.

  Although the embodiments of the present invention have been described above, various modifications and combinations necessary for design or manufacturing convenience and other factors are described in the claimed invention and the embodiments of the invention. It is included in the scope of the invention corresponding to the specific example.

DESCRIPTION OF SYMBOLS 1 ... Current-limiting reactor, 10 ... Core, 20 ... Coil, 30 ... Embedded member, 31 ... 1st main surface of an embedded member, 32 ... 2nd main surface of an embedded member, 33 ... Embedded member Through hole

Claims (4)

A core for a current-limiting reactor formed of a magnetic material,
A plurality of embedded members made of a material having a lower electrical resistivity than the magnetic body, and having a through-hole penetrating from the first main surface to the second main surface facing the first main surface The embedded member is embedded,
Core for current-limiting reactor, characterized by that. The magnetic body is iron-based,
The embedded member is formed of gold, silver, copper, or aluminum;
The core for a current-limiting reactor according to claim 1. The core for a current-limiting reactor according to claim 1 or 2,
A coil wound around the core for the current-limiting reactor,
With
A magnetic field generated when a current flows through the coil is linked to the first main surface and the second main surface of the embedded member;
A current-limiting reactor characterized by that. A second main surface which is an embedded member made of a powder containing magnetic particles made of a material having an electric resistivity lower than that of the magnetic material and which faces the first main surface from the first main surface. A process of putting a plurality of embedding members having through holes penetrating into the mold while embedding them in the powder; and
A step of compressing and molding the powder in which the embedding member is embedded;
A method for manufacturing a core for a current-limiting reactor, comprising:

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