Core structure and transformer

Abstract

To alleviate magnetic flux concentration and iron loss on an inner circumferential side of a bonding part between a wire-wound part and a non-wire-wound part of an iron core made up of ferrite cores.SOLUTION: A transformer 1 comprises: a hollow columnar-shaped iron core 2 made up of ferrite cores 21 to 25; and a primary winding 3 and a secondary winding 4 wound around the iron core 2. A corner 28 of the iron core 2, which is a bonding part between a wire-wound part 26 and a non-wire-wound part 27, is formed by disposing and stacking, in one direction, the plurality of ferrite cores 21 to 25 with different transverse cross sections. The transverse cross sections gradually become smaller from an outer circumferential side toward an inner circumferential side of the iron core 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an iron core for a high-frequency, large-capacity transformer, and in particular to the structure of an iron core made of a ferrite core. [Background technology]

[0002] The core of a large-capacity transformer generally has a structure in which plate-shaped magnetic bodies made of, for example, ferrite cores are arranged in a frame shape and laminated in one direction (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Publication No. 58-12915 [Patent Document 2] Japanese Patent Application Publication No. 5-326289 Summary of the Invention [Problem to be solved by the invention]

[0004] In an iron core made of laminated ferrite cores, magnetic resistance caused by the gaps between adjacent ferrite cores causes magnetic flux to concentrate on the inner side of the iron core, especially at the joints between the winding and non-winding parts of the iron core, and iron loss also concentrates on this inner side.

[0005] In view of the above circumstances, an object of the present invention is to reduce magnetic flux concentration and core loss on the inner periphery of a joint between a winding portion and a non-winding portion of an iron core made of a ferrite core. [Means for solving the problem]

[0006] Therefore, one aspect of the present invention is an iron core structure, in which a ferrite core having a different cross section is disposed at a joint between a winding portion and a non-winding portion of the iron core made of a ferrite core.

[0007] In one aspect of the present invention, in the core structure, the cross section becomes smaller from the outer periphery side to the inner periphery side of the core.

[0008] One aspect of the present invention is a transformer having the above-described core structure. Effect of the Invention

[0009] According to the present invention as described above, it is possible to reduce magnetic flux concentration and core loss on the inner periphery side of the joint between the winding portion and the non-winding portion of the iron core made of a ferrite core. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a core structure in a transformer according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram of the magnetic resistance of a magnetic circuit simulating the outer, middle and inner layers of a transformer core. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] The core structure of the first embodiment shown in FIG. 1 is applied to, for example, a core-type transformer 1.

[0013] The transformer 1 includes an iron core 2 formed of ferrite cores 21 to 25, and a primary winding 3 and a secondary winding 4 wound around this iron core 2.

[0014] As shown in the figure, the iron core 2 is formed in the shape of a hollow prism by laminating rectangular or long plate-shaped ferrite cores 21 to 25 arranged in a frame shape in one direction.

[0015] The winding section 26, which corresponds to the leg section of the core 2 around which the primary winding 3 and secondary winding 4 are wound, and the non-winding section 27, which corresponds to the yoke section of the core 2 around which the primary winding 3 and secondary winding 4 are not wound, are formed by arranging ferrite cores 21 of the same size and stacking them in one direction. Adjacent ferrite cores 21 are bonded by a bonding method well known in the field of core manufacturing.

[0016] Corner portion 28 of core 2, which is the joint between winding portion 26 and non-winding portion 27, is formed by arranging and stacking in one direction a plurality of ferrite cores 21-25 with different cross sections perpendicular to the axial direction of core 2. The cross sections become smaller from the outer periphery to the inner periphery of core 2. Adjacent ferrite cores 21-25 are also bonded by the well-known bonding method.

[0017] In the case of the three-layer core 2 illustrated in Fig. 1, the joint 29 has a substantially square cross section. A ferrite core 21 having a rectangular cross section of normal dimensions and a ferrite core 22 having a rectangular cross section that is approximately 2 / 3 of the normal dimensions are disposed in the outer layer OUT (Fig. 2) of this joint 29. Furthermore, ferrite cores 23 and 24 having a cross section that is approximately 1 / 3 or approximately 1 / 3 to 4 / 5 of the ferrite core 21 are disposed in the middle layer CEN (same figure) located on the inner circumferential side of the outer layer OUT. Then, ferrite cores 24 and 25 having a cross section that is approximately 1 / 3 or approximately 1 / 10 of the ferrite core 21 are disposed in the inner layer IN (same figure) located on the inner circumferential side of the middle layer CEN.

[0018] In particular, the ferrite cores 21 to 25 are arranged and laminated so that the magnetic resistances of the inner layer IN, the middle layer CEN, and the outer layer OUT of the iron core 2 are approximately uniform. That is, the magnetic resistance Rm_IN of the inner layer IN, the magnetic resistance Rm_CEN of the middle layer CEN, and the magnetic resistance Rm_OUT of the outer layer OUT of the three-layer iron core 2 illustrated in FIG. 2 are expressed by the following formulas (1) to (3) (where μ is the magnetic permeability of the iron core 2, l is the magnetic resistance of the inner layer IN, the middle layer CEN, and the outer layer OUT, respectively). IN : Length of the magnetic path in the inner layer IN, l CEN : Length of the magnetic path of the middle layer CEN, l OUT : length of the magnetic path of the outer layer OUT, S: cross-sectional area of ​​the magnetic path, μ0: magnetic permeability of vacuum, l gap: The length of the gap between adjacent ferrite cores 21 to 25 in the inner layer IN, the middle layer CEN, and the outer layer OUT, S gap : the cross-sectional area of ​​the gap).

[0019]

number

[0020]

number

[0021]

number

[0022] Ordinary magnetic resistances Rm_OUT, Rm_CEN, and Rm_IN are expressed by the following equation (4).

[0023]

number

[0024] The magnetic resistances Rm_OUT, Rm_CEN, and Rm_IN are adjusted to be approximately equal by adjusting the length and number of the gaps, since the magnetic resistance of the gaps between the adjacent ferrite cores 21 to 25 is larger than the magnetic resistance of the ferrite cores 21 to 25. In particular, since the magnetic reluctance rate μ(φ) is a function of the magnetic flux φ, the length and number of the gaps are adjusted by a numerical analysis method such as the finite element method so that the magnetic resistances Rm_OUT, Rm_CEN, and Rm_IN are equal as shown in the following formula (5).

[0025]

number

[0026] As described above, the ferrite cores 21-25 having different cross-sectional dimensions are arranged and laminated such that, for example, the length of the gap between adjacent ferrite cores 21-25 becomes smaller from the outer periphery to the inner periphery of the iron core 2. As a result, the number of gaps between the ferrite cores 21-25 is smaller on the outside of the iron core 2 and is greater on the inside, and the magnetic resistance on the outside and inside is uniform, so that concentration of magnetic flux at corners 28 of the iron core 2 (joints between the winding winding portion 26 and the non-winding winding portion 27) is alleviated.

[0027] Although there are technical limitations to enlarging the ferrite cores 21 to 25 of the iron core 2, this can be achieved by arranging and laminating ferrite cores of available sizes. In particular, by equalizing the magnetic resistance by adjusting the number of gaps, it is possible to prevent magnetic flux from concentrating on the inner periphery of the iron core 2, and thus prevent iron loss from concentrating on the inside where it is difficult to cool.

[0028] Although the core structure of the above embodiment is applied to a core-type transformer, it is clear that the same effect as in the above embodiment can be obtained even if the core structure of the present invention is applied to a shell-type transformer. Also, although the core 2 is a three-layer core, it is clear that the same effect as in the above embodiment can be obtained even if the core structure of the present invention is applied to a four-layer or more core. [Explanation of symbols]

[0029] 1. Transformer 2... iron core, 21 to 25... ferrite core, 26... winding portion, 27... non-winding portion, 28... corner portion 3…Primary winding 4…Secondary winding

Claims

1. The joint between the winding portion and the non-winding portion of the iron core is made of multiple ferrite cores, An iron core structure, characterized in that the length of the gap of the ferrite core becomes smaller from the outer layer to the inner layer of the joint.

2. A transformer having the core structure according to claim 1.

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