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 transverse cross section of a ferrite core 211 forming an inner layer of a leg part 26 of an iron core 2 around which a primary winding 3 and a secondary winding 4 are wound is smaller than a transverse cross section of a ferrite core 21 forming an outer layer and a middle layer of the leg part 26. A transverse cross section of a ferrite core 212 forming a middle layer and an inner layer of a yoke part 27 of the iron core 2 around which the primary winding 3 and the secondary winding 4 are not wound is smaller than a transverse cross section of the ferrite core 21 forming an outer layer of the yoke part 27. The ferrite cores 21, 211, and 212 forming the outer layer, the middle layer, and the inner layer of the iron core 2 are arranged such that magnetic resistance of the outer layer, the middle layer, and the inner layer may be equivalent to one another.SELECTED DRAWING: Figure 3

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 having an outer layer consisting of a plurality of ferrite cores, a middle layer consisting of a plurality of ferrite cores arranged on the inner side of the outer layer, and an inner layer consisting of a plurality of ferrite cores arranged on the inner side of the middle layer, wherein the cross-section of the ferrite core constituting the inner layer of the leg portion of the iron core around which the winding is wound is smaller than the cross-section of the ferrite core constituting the outer layer and the middle layer of the leg portion, the cross-section of the ferrite core constituting the middle layer and the inner layer of the yoke portion of the iron core around which the winding is not wound is smaller than the cross-section of the ferrite core constituting the outer layer of the yoke portion, and the ferrite cores of the outer layer, middle layer and inner layer are arranged so that the magnetic resistance of the outer layer, middle layer and inner layer are equivalent.

[0007] In one embodiment of the present invention, in the core structure, the cross-section of the ferrite core forming the inner layer of the leg portion is 1 / 2 the cross-section of the ferrite core forming the outer layer and middle layer of the leg portion, the cross-section of the ferrite core forming the middle layer and inner layer of the yoke portion is 1 / 2 the cross-section of the ferrite core forming the outer layer of the yoke portion, and the ferrite core of the outer layer of the yoke portion is positioned such that the cross-section of the outer layer is smaller than the cross-sections of the middle layer and inner layer of the yoke portion.

[0008] One aspect of the present invention is an iron core structure having an outer layer consisting of a plurality of ferrite cores, a middle layer consisting of a plurality of ferrite cores arranged on the inner side of the outer layer, and an inner layer consisting of a plurality of ferrite cores arranged on the inner side of the middle layer, wherein the cross-section of the ferrite core constituting the inner layer of the leg portion of the iron core around which the winding is wound is smaller than the cross-section of the ferrite core constituting the outer layer and the middle layer of the leg portion, the cross-section of the ferrite core constituting the middle layer of the yoke portion of the iron core around which the winding is not wound is smaller than the cross-section of the ferrite core constituting the outer layer and the inner layer of the yoke portion, and the ferrite cores of the outer layer, middle layer and inner layer are arranged so that the magnetic resistance of the outer layer, middle layer and inner layer are equivalent.

[0009] In one embodiment of the present invention, in the core structure, the cross-section of the ferrite core forming the inner layer of the leg portion is 1 / 3 of the cross-section of the ferrite core forming the outer layer and the middle layer of the leg portion, and the cross-section of the ferrite core forming the middle layer of the yoke portion is 1 / 3 of the cross-section of the ferrite core forming the outer layer and the inner layer of the yoke portion.

[0010] One aspect of the present invention is a transformer having the above-described core structure. Effect of the Invention

[0011] 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]

[0012] [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. [Diagram 3] FIG. 4 is a cross-sectional view of a core structure in a transformer according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of a core structure in a transformer according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] [Embodiment 1] The core structure of the first embodiment shown in FIG. 1 is applied to, for example, a core-type transformer 1.

[0015] 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.

[0016] As shown in the figure, the iron core 2 is formed in a hollow prismatic shape by laminating rectangular or long plate-shaped ferrite cores 21 to 25 arranged in a frame shape in one direction.

[0017] The leg portions 26 of the core 2 around which the primary winding 3 and secondary winding 4 are wound, and the yoke portion 27 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.

[0018] Corner portion 28 of core 2, which is the joint between leg portion 26 and yoke 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.

[0019] In the case of the three-layer core 2 illustrated in Fig. 1, the corner 28 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 arranged in the outer layer OUT (Fig. 2) of this corner 28. 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 arranged 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 arranged in the inner layer IN (same figure) located on the inner circumferential side of the middle layer CEN.

[0020] In particular, the ferrite cores 21 to 25 are arranged and laminated so that the magnetic resistances of the inner layer IN, middle layer CEN, and 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 the figure are expressed by the following formulas (1) to (3) (where μ is the magnetic permeability of the iron core 2, l IN : Length of the magnetic path in the inner layer IN, l CEN : Length of the magnetic path of the middle layer CEN, lOUT : length of the magnetic path of the outer layer OUT, S: cross-sectional area of ​​the magnetic path, μ 0 : Vacuum permeability, 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 same applies to the following embodiments 2 and 3.)

[0021]

number

[0022]

number

[0023]

number

[0024] The relationship between the normal magnetoresistance Rm_OUT, the magnetoresistance Rm_CEN, and the magnetoresistance Rm_IN is given by the following equation (4).

[0025]

number

[0026] 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).

[0027] [Number]

[0028] As described above, the ferrite cores 21-25 having different cross-sectional dimensions are arranged and laminated such that the gap length 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 larger on the inside, and the magnetic resistance on the outside and inside becomes uniform, so that concentration of magnetic flux at the corners 28 of the iron core 2 (joints between the leg portions 26 and the yoke portions 27) is alleviated.

[0029] 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.

[0030] [Embodiment 2] 3, the cross section of the ferrite core 211 forming the inner layer of the leg portion 26 is set smaller than the cross section of the ferrite core 21 forming the outer and middle layers of the leg portion 26. The cross section of the ferrite core 212 forming the middle and inner layers of the yoke portion 27 is also set smaller than the cross section of the ferrite core 21 forming the outer layer of the yoke portion 27. The ferrite cores 21, 211, 212 are arranged so that the magnetic resistances of the outer, middle, and inner layers of the iron core 2 are equivalent, thereby mitigating magnetic flux concentration on the inner periphery side of the corner portion 28 of the iron core 2 and iron loss.

[0031] The cross sections of the illustrated ferrite cores 211, 212 are set to be half the cross section of the ferrite core 21. Furthermore, the ferrite cores 21 in the outer layer of the yoke portion 27 are arranged so that the cross sections of the outer layer are smaller than the cross sections of the middle and inner layers of the yoke portion 27. Specifically, the number of ferrite cores 21 arranged in the outer layer of the yoke portion 27 is reduced to "2", one less than the number "3" of ferrite cores 21 arranged in the outer layer of the yoke portion 27 in the first embodiment.

[0032] 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 iron core 2 due to the ferrite cores 21, 211, 212 and their connection portions (gaps) are expressed by the following equations (6) to (8).

[0033]

number

[0034]

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[0035]

number

[0036] Since the magnetic resistance of the connection portion is dominant, the relationship between the magnetic resistance Rm_OUT, the magnetic resistance Rm_CEN, and the magnetic resistance Rm_IN is expressed by the following formula (9).

[0037]

number

[0038] As described above, by arranging the ferrite cores 21, 211, 212 in the iron core 2 so that the number of connection parts of the ferrite cores 21, 211, 212 are the same, the magnetic resistance of the inner layer, middle layer and outer layer of the iron core 2 becomes uniform and concentration of magnetic flux density is mitigated.

[0039] In the core 2 of the first embodiment, a magnetic circuit of the core 2 is adjusted so that a plurality of ferrite cores of different sizes are combined to make the magnetic flux density uniform, but the core 2 of the second embodiment can reduce the number of different sizes of the ferrite cores in addition to the effect of the first embodiment. Since the magnetic flux density is low at the corners 28 of the core 2, by arranging the ferrite cores so that the cross section of the outer layer of the yoke portion 27 is smaller than the cross sections of the middle and inner layers of the yoke portion 27 as in the second embodiment, the number of ferrite cores can be further reduced compared to the first embodiment.

[0040] [Embodiment 3] In the iron core 2 of the embodiment 3 shown in Fig. 4, the cross section of the ferrite core 213 forming the inner layer of the leg portion 26 is set smaller than the cross section of the ferrite core 21 forming the outer and middle layers of the leg portion 26. The cross section of the ferrite core 214 in the middle layer of the yoke portion 27 is also set smaller than the cross sections of the ferrite core 21 in the outer and inner layers of the yoke portion 27. The cross sections of the ferrite cores 213 and 214 shown in the figure are set to 1 / 3 of the cross section of the ferrite core 21. The ferrite cores 21, 213 and 214 are arranged so that the magnetic resistances of the outer, middle and inner layers of the iron core 2 are equivalent, thereby mitigating magnetic flux concentration on the inner periphery side of the corner portion 28 of the iron core 2 and iron loss.

[0041] 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 iron core 2 due to the ferrite cores 21, 213, 214 and their connection portions (gaps) are expressed by the following equations (10) to (12).

[0042]

number

[0043]

number

[0044]

number

[0045] In this embodiment, as in the second embodiment, the magnetic resistance of the connection portion is dominant, so that the relationship between the magnetic resistance Rm_OUT, the magnetic resistance Rm_CEN, and the magnetic resistance Rm_IN is expressed by the above formula (9).

[0046] As described above, by arranging the ferrite cores 21, 213, 214 in the iron core 2 so that the number of connection parts of the ferrite cores 21, 213, 214 are the same, the magnetic resistance of the inner layer, middle layer, and outer layer of the iron core 2 becomes uniform, and the concentration of magnetic flux density is alleviated as in embodiment 2. Then, as in embodiment 2, in addition to the effect of embodiment 1, the variety of dimensions of the ferrite cores can be reduced.

[0047] Although the core structures of the above embodiments 1 to 3 are applied to core-type transformers, it is clear that the same effects as those of the above embodiments 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 effects as those of the above embodiments can be obtained even if the core structure of the present invention is applied to a four-layer or more core. [Explanation of symbols]

[0048] 1...Transformer 2...Iron core, 21-25, 211-214...Ferrite core, 26...Leg portion, 27...Yoke portion, 28...Corner portion 3…Primary winding 4…Secondary winding

Claims

1. an outer layer made of a plurality of ferrite cores; an intermediate layer made of a plurality of ferrite cores arranged on the inner peripheral side of the outer layer; an inner layer made of a plurality of ferrite cores arranged on the inner periphery side of the intermediate layer; having a cross section of a ferrite core constituting the inner layer of a leg portion of the iron core around which the winding is wound is smaller than cross sections of ferrite cores constituting the outer layer and the middle layer of the leg portion, a cross section of a ferrite core constituting the middle layer and the inner layer of a yoke portion of the iron core on which the winding is not wound is smaller than a cross section of a ferrite core constituting the outer layer of the yoke portion, The ferrite cores of the outer layer, the intermediate layer and the inner layer are arranged so that the magnetic resistances of the outer layer, the intermediate layer and the inner layer are equal to each other. An iron core structure characterized by:

2. a cross section of the ferrite core constituting the inner layer of the leg portion is half a cross section of the ferrite core constituting the outer layer and the middle layer of the leg portion, a cross section of the ferrite core constituting the middle layer and the inner layer of the yoke portion is half a cross section of the ferrite core constituting the outer layer of the yoke portion, The ferrite core of the outer layer of the yoke portion is arranged so that the cross section of the outer layer is smaller than the cross sections of the middle layer and the inner layer of the yoke portion. The core structure according to claim 1 .

3. an outer layer made of a plurality of ferrite cores; an intermediate layer made of a plurality of ferrite cores arranged on the inner peripheral side of the outer layer; an inner layer made of a plurality of ferrite cores arranged on the inner periphery side of the intermediate layer; having a cross section of a ferrite core constituting the inner layer of a leg portion of the iron core around which the winding is wound is smaller than cross sections of ferrite cores constituting the outer layer and the middle layer of the leg portion, a cross section of a ferrite core constituting the middle layer of a yoke portion of the iron core on which the winding is not wound is smaller than cross sections of ferrite cores constituting the outer layer and the inner layer of the yoke portion, The ferrite cores of the outer layer, the intermediate layer and the inner layer are arranged so that the magnetic resistances of the outer layer, the intermediate layer and the inner layer are equal to each other. An iron core structure characterized by:

4. a cross section of the ferrite core constituting the inner layer of the leg portion is ⅓ of a cross section of the ferrite core constituting the outer layer and the middle layer of the leg portion, The cross section of the ferrite core constituting the middle layer of the yoke portion is 1 / 3 of the cross section of the ferrite core constituting the outer layer and the inner layer of the yoke portion. The iron core structure according to claim 3 .

5. A transformer having the core structure according to any one of claims 1 to 4.

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