JP2004319669A - Power transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power transformer using a uncut annular core of small leakage flux in which formation of wire winding is easy in a power transformer for large current, the matter of magnetic property deterioration looked at a cut core is not generated, and simplification of wire winding structure is possible. <P>SOLUTION: A power transformer is provided with the uncut annular core, a primary winding wound around the annular core, and a secondary winding constituted in one turn. The secondary winding is provided with conductor penetrating interior of the annular core, and two cylindrical bottomed conductors. The cylindrical bottomed conductors accommodate the annular core so as to be pinched on both sides of the annular core from longitudinal, and are electrically connected with both ends of the conductors penetrating interior of the annular core. On the periphery of the annular core parallel with longitudinal, it is a power transformer insulated electrically mutually. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power transformer used for various inverters, DC-DC converters, switching power supplies, and the like.
[0002]
[Prior art]
The power transformer is composed of an annular core, a primary winding, and a secondary winding. The primary winding and the secondary winding wound around the annular core (uncut annular core) minimize leakage magnetic flux. In order to enhance the coupling, a special study has been made on the winding structure, such as a so-called sandwich structure in which a secondary winding is sandwiched between primary windings as shown in FIG. For example, see Patent Document 1).
The sandwich structure has a complicated winding structure, and can be applied to a power transformer having a small diameter of a conductive wire used for winding, but requires many man-hours for winding. Further, it is difficult to apply the present invention to a power transformer for a large current which requires a large diameter conductor or a large number of conductors to be wound.
Therefore, at present, it is widely practiced to use a cut core obtained by dividing the above-mentioned annular core (uncut annular core) into two or more members, process the conductor in advance into a winding shape, and combine the cut wire with the cut core to form a power transformer. Has been done.
[0003]
By the way, as a typical example of a core applied to a power transformer, a Mn-Zn ferrite core, an amorphous magnetic material manufactured by rapidly solidifying a molten alloy, and a metal magnetic ribbon made of a nanocrystalline magnetic material are wound. There is a core. The nanocrystalline magnetic material is a soft magnetic material having a nanocrystalline structure in which at least 50% or more of the structure has a crystal grain size of 50 μm or less. (For example, see Patent Document 2).
[0004]
Among them, an annular core formed by winding a metal magnetic ribbon such as an amorphous magnetic material is widely used as a core for a power transformer which handles a large current and a large capacity.
Large cores for power transformers that handle large currents and large capacities require large dimensions.However, Mn-Zn ferrite has technical problems, such as restrictions on presses for shaping the core. However, there is a limit to the demand for increasing the size of the annular core. On the other hand, the annular core made of an amorphous magnetic material and a nanocrystalline magnetic material is formed by winding a metal magnetic ribbon, and thus has a high degree of freedom in shape and can easily cope with an increase in the size of the annular core. . Furthermore, amorphous magnetic materials and nanocrystalline magnetic materials have both high saturation magnetic flux density (more than twice as large as Mn-Zn ferrite) and low loss required for miniaturization, and are also suitable for power transformer cores in terms of characteristics. Material.
[0005]
[Patent Document 1]
JP 2001-118733 A [Patent Document 2]
JP-A-1-79342
[Problems to be solved by the invention]
As described above, a metal magnetic ribbon such as an amorphous magnetic material is suitable as a material for a power transformer, but the thickness of the metal magnetic ribbon is several tens of microns. The strength is lower than such a bulk material, and it cannot be cut and processed into the above-mentioned uncut annular core.
[0007]
Therefore, the cut core formed by winding the metal magnetic ribbon is required to be dried and solidified after impregnating the resin with the uncut annular core prepared in advance in order to cut the annular core. Another problem is that the core loss increases due to the residual stress of the resin that has penetrated between the layers during drying. Also, after cutting, it is necessary to polish the cut surface so that the joints of the pair of magnetic cores can be accurately fitted, and eddy current increases due to dielectric breakdown between adjacent ribbons on that surface, resulting in increased core loss. There was a problem of increasing. Furthermore, there is a problem that the copper loss of the winding increases due to the leakage magnetic flux generated from the core joint, and the loss of the power transformer increases.
Furthermore, the use of cut cores causes not only an increase in core loss but also an increase in cost due to an increase in the number of manufacturing steps.
[0008]
According to the present invention, it is easy to form a winding even in a power transformer for a large current, and there is no problem of a decrease in magnetic characteristics seen in a cut core. An object is to provide a power transformer using an uncut annular core.
[0009]
[Means for Solving the Problems]
The present inventors can solve the above-mentioned problem by applying a structure composed of two cylindrical conductors or one cylindrical conductor and one lid-shaped conductor to enclose the entire transformer in the secondary winding. And arrived at the present invention.
[0010]
That is, the present invention is a power transformer including an uncut annular core, a primary winding wound around the uncut annular core, and a secondary winding composed of one turn, wherein the secondary winding is A conductor penetrating the inside of the uncut annular core, and two bottomed tubular conductors, wherein the tubular conductor houses the uncut annular core so as to sandwich the same from the axial direction, and the inside of the uncut annular core. The power transformers are electrically connected at both ends of a conductor penetrating through them, and are electrically insulated from each other on the outer peripheral surface of the uncut annular core parallel to the axial direction.
[0011]
Still another aspect of the present invention is a power transformer including an uncut annular core, a primary winding wound around the uncut annular core, and a secondary winding composed of one turn. The winding includes a conductor penetrating the inside of the uncut annular core, one bottomed tubular conductor and one lid, and the tubular conductor and the lid conductor sandwich the uncut annular core from the axial direction. The power transformer is housed in such a manner, and is electrically connected at both ends of a conductor penetrating the inside of the uncut annular core, and is otherwise electrically insulated from each other.
[0012]
In the present invention described above, it is preferable that the two tubular conductors, or the one tubular conductor and the one lid conductor, have different diameters and overlap on the outer peripheral surface of the uncut annular core.
Preferably, the uncut annular core is made of either an amorphous magnetic material or a nanocrystalline magnetic material.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of the power transformer of the present invention. As shown in FIG. 1, the power transformer of the present invention includes an uncut annular core 1, a primary winding 2 wound around the uncut annular core 1, a through conductor 3, and tubular conductors 4a and 4b. It consists of a secondary winding.
[0014]
FIG. 2 is a schematic view of the uncut annular core wound with a primary winding used in FIG. FIG. 3 is an exploded view of the secondary winding.
[0015]
In the power transformer according to the present invention, as shown in FIG. 3, the secondary winding penetrates the inner diameter of the uncut annular core and forms one turn of the through conductor 3, and the uncut annular core and 1 shown in FIG. It is composed of two bottomed tubular conductors 4a and 4b to enclose the next winding. The penetrating conductor 3 and the cylindrical conductors 4a and 4b are fixed at both ends of the penetrating conductor using screws or the like, and the two cylindrical conductors are electrically insulated from each other on the outer peripheral side of the annular core to make one turn. Is composed.
[0016]
As described above, in the present invention, since the annular core in which only the primary winding is singly wound is sandwiched from both sides by the cylindrical conductor, a complicated winding as proposed in Patent Document 1 is provided. It is extremely simple compared to the structure. At the same time, in the present invention, the secondary winding formed by the penetrating conductor and the cylindrical conductor almost completely surrounds the primary winding and the uncut annular core, so that the secondary winding is highly effective as a shield body. A low-leakage magnetic flux structure with little leakage of magnetic flux to the outside is made possible.
[0017]
Further, in the present invention, since only the primary winding is formed by winding around the annular core, it is possible to directly wind around the annular core even when a large-diameter conductive wire is used. Therefore, even when a large-diameter conductor such as a power transformer for a large current whose rated current on the secondary winding side is 100 A or more is used, an uncut annular core can be applied. It becomes unnecessary and the number of steps can be reduced.
[0018]
According to the present invention, as described above, a low-leakage magnetic flux structure with little leakage of magnetic flux to the outside of the secondary winding is possible, but also has an advantage that it is hardly affected by external magnetic flux.
For example, as shown in FIG. 4, lead wires 5a and 5b were attached to the cylindrical conductor constituting the secondary winding, and the inductance load shown in FIG. In this case, leakage magnetic flux is generated from the lead lines 5a and 5b. When this leakage magnetic field acts directly on the core, an in-plane eddy current loss occurs in the core. On the other hand, the present invention has a structure in which the core is shielded from the outside by the secondary winding, and the leakage magnetic flux is blocked by a cylindrical conductor or the like constituting the secondary winding so as not to be orthogonal to the outer peripheral surface of the core. Therefore, there is little concern that in-plane eddy current loss occurs in the core, and heat generation can be minimized.
[0019]
In particular, in the two cylindrical conductors constituting the secondary winding, as shown in FIG. 1, the diameters of the two cylindrical conductors are different from each other, and are overlapped on the outer peripheral surface of the uncut annular core parallel to the axial direction. In this case, the effect as a shield body and the effect of blocking leakage magnetic flux generated from the lead wire are further enhanced, which is preferable.
[0020]
As described above, since the transformer of the present invention can have a low leakage magnetic flux structure with a simple structure, it is effective for cost reduction.
[0021]
Further, the power transformer of the present invention has the following advantages.
(1) A thin structure can be easily realized, thereby improving heat dissipation.
(2) The heat of the primary winding and the core can be easily dissipated by inserting a heat dissipation sheet or the like between the primary winding and the cylindrical conductor.
(3) When a cooling mechanism for cooling the core is provided, a small-sized core can be used. However, since the secondary winding can be used also as a cooling mechanism simply by attaching a cooling pipe such as a water-cooled pipe, a power transformer is used. Can be reduced in size.
[0022]
The effect described above can be obtained even when the secondary winding is constituted by the through conductor 3, one bottomed cylindrical conductor 4 a, and one lid-shaped conductor 7 as shown in an example in FIG. 5. Since the primary winding and the uncut annular core can be almost completely wrapped, the function as a shield body is high, and a low leakage magnetic flux structure with little leakage of magnetic flux to the outside of the secondary winding is obtained, and the secondary winding is drawn out. Since the leakage magnetic flux generated from the wire prevents the outer peripheral surface and the inner peripheral surface of the core from being orthogonal to each other, there is little concern that in-plane eddy current loss occurs in the core due to the leakage magnetic flux, and the same can be achieved. Can be.
[0023]
The power transformer of the present invention is particularly effective when an annular core formed by winding a metal magnetic ribbon of an amorphous magnetic material or a nanocrystalline magnetic material is used.
The above-described metal magnetic ribbon has a smaller electric resistance than Mn-Zn ferrite or the like, and tends to cause an increase in eddy current loss due to leakage magnetic flux. On the other hand, the structure of the power transformer of the present invention is very effective because it has a high shielding property against magnetic flux leakage. In addition, the material has a saturation magnetic flux density as high as twice or more that of Mn-Zn ferrite, and has a small core loss, which can contribute to downsizing of a transformer.
In addition, when an annular core made of a magnetic metal ribbon such as an amorphous alloy ribbon is used as a cut core, a number of problems have occurred as described above. According to the present invention, the present invention can be applied to a power transformer for a large current without impairing the excellent magnetic properties of the metal magnetic ribbon.
[0024]
When the power transformer of the present invention is used in a power supply device, the power supply device can be reduced in size and the leakage magnetic flux can be suppressed. Become. Further, by using the power transformer of the present invention, a low-cost power supply device can be manufactured.
[0025]
【The invention's effect】
As described above, according to the present invention, a small-sized, low-loss, low-leakage magnetic flux structure, and low radiation noise are obtained by using a non-cut annular core capable of maximizing the excellent magnetic properties of a soft magnetic alloy ribbon. A power transformer and the like can be manufactured using the power transformer, which is small, highly efficient, low noise and highly reliable. Further, since a high-performance power transformer can be configured with a relatively simple structure, a practical and low-cost power transformer can be configured with a small number of steps, and the effect is extremely large.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a power transformer showing an example of the present invention.
FIG. 2 is a schematic view of an annular core after winding a primary winding used in a power transformer according to an example of the present invention.
FIG. 3 is an exploded view of a secondary winding used in a power transformer showing an example of the present invention.
FIG. 4 is a schematic diagram of a power transformer in which a lead wire is attached to a power transformer according to an example of the present invention.
FIG. 5 is an exploded view of a secondary winding used in a power transformer showing an example of the present invention.
FIG. 6 is a schematic diagram of an inductance load connected to the power transformer of the present invention.
FIG. 7 is a schematic diagram showing an example of a conventional power transformer.
[Explanation of symbols]
1. 2. Uncut annular core, 2.1 primary winding, Penetrating conductor, 4a, 4b. Cylindrical conductors, 5a, 5b. 5. Leader lines, 6. Load connection terminal, Lid-shaped conductor, 8. Secondary winding

Claims (4)

A power transformer comprising an uncut annular core, a primary winding wound around the uncut annular core, and a secondary winding composed of one turn, wherein the secondary winding is formed of the uncut annular core. A conductor penetrating the inside, and two bottomed tubular conductors, wherein the tubular conductor is housed so as to sandwich the uncut annular core from the axial direction, and a conductor that penetrates the inside of the uncut annular core. A power transformer characterized in that both ends are electrically connected to each other, and are electrically insulated from each other on an outer peripheral surface of an uncut annular core parallel to an axial direction. A power transformer comprising an uncut annular core, a primary winding wound around the uncut annular core, and a secondary winding composed of one turn, wherein the secondary winding is formed of the uncut annular core. A conductor penetrating the inside, one bottomed cylindrical conductor and one lid-shaped conductor are provided, and the cylindrical conductor and the lid-shaped conductor are housed so as to sandwich the uncut annular core from the axial direction, and A power transformer characterized by being electrically connected at both ends of a conductor penetrating the inside of an uncut annular core, and being electrically insulated from each other at other ends. The power transformer according to claim 1, wherein the two tubular conductors, or one tubular conductor and one lid conductor, have different diameters and overlap on an outer peripheral surface of the uncut annular core. . 4. The power transformer according to claim 1, wherein the uncut annular core is made of one of an amorphous magnetic material and a nanocrystalline magnetic material.

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