JP7306789B2 - coil and transformer - Google Patents

Description

The present invention relates to coils and transformers.

2. Description of the Related Art Electric/electronic equipment usually incorporates an inverter and a transformer (also referred to as a transformer) in order to reduce power consumption. Transformers used at high frequencies generally have a coil wound around a core with an electric wire whose conductor radius is smaller than the skin depth determined by the frequency in order to suppress an increase in resistance due to the skin effect.
In order to increase the output of such a transformer, it is necessary to increase the conductor cross-sectional area of the wire wound around the core. In this case, considering the increase in resistance due to the skin effect as described above, it is important to avoid using wires having large-diameter conductors, which increases the number of wires to be wound. Methods for increasing the number of electric wires generally include a method of using a plurality of electric wires to increase the number of parallel wires, and a method of using a litz wire in which a plurality of wires are spirally twisted together.
As a transformer having a coil wound with a litz wire as an electric wire, for example, Patent Document 1 describes a step-up transformer used in a high-frequency heating device. Specifically, this step-up transformer uses, as a secondary winding (high-voltage, low-current side coil), an electric wire in which a litz wire obtained by bundling a plurality of insulated conductors is further coated with an insulator. This step-up transformer has an improved secondary winding as described above. The diameter of the wire is reduced to suppress the influence of the skin effect, and the litz wire is covered with an insulator to ensure insulation performance. It is stated that

JP-A-5-13247

A transformer normally has an input side (primary side) coil and an output side (secondary side) coil, and the voltage and current value of the current applied to each coil are set. In a transformer, one of the primary side coil and the secondary side coil is generally a low-voltage, large-current side coil, and the other is relatively a high-voltage, small-current side coil.
In the present invention, the low-voltage, large-current side coil means a coil through which a relatively low-voltage, large-current value flows among the two coils, and the high-voltage, small-current side coil means a relatively , means a coil through which a current of high voltage and small current value flows.

For low-voltage, high-current coils of high-frequency transformers, conventionally, electric wires having a conductor designed in consideration of the influence of the skin effect and a thin insulating layer covering the outer periphery of the conductor have been used. The reason why the insulating layer is formed as a thin film in this way is that a low-voltage current flows through this wire. In addition, it is necessary to set a high space factor for the purpose of preventing Joule loss due to a large current, and forming the insulating layer as thin as possible has been an effective means for achieving this.

When a high output of 1000 W or more is required for such a high-frequency transformer, the resistance of the low-voltage, high-current side coil becomes large, and accordingly the loss of the transformer becomes large. Therefore, it is necessary to further increase the number of electric wires used for the low-voltage, high-current side coil. As a result, the DC resistance can be made small and the loss can be reduced. However, as the number of wires increases, the AC resistance increases due to the proximity effect acting between the wires. The influence of such a proximity effect cannot be ignored, for example, when the frequency is about 30 kHz or higher. Therefore, in a high-frequency high-output transformer, even if the number of wires is simply increased, there is a limitation in reducing the AC resistance value, and the loss cannot be sufficiently reduced.
In this way, as a wire used for the low-voltage, high-current side coil, in the conventional wire in which the insulating layer is formed thin in consideration of the above-mentioned skin effect and space factor, in order to further reduce the loss of the transformer, There were limitations and improvements were desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a low-resistance coil capable of reducing loss, and a high-frequency high-output transformer including this coil.
In the present invention, the high frequency of the transformer means that the operating frequency is, for example, 30 to 150 kHz, although it is not particularly limited. Further, the high output of the transformer is not particularly limited, but refers to, for example, an output of 1000 W or more, and the upper limit thereof is, for example, 10 kW.

Contrary to conventional electric wires used for low-voltage, high-current coils, the present inventors have attempted to reduce the space factor of conductors within a range that satisfies specific conditions, that is, to specify the distance between adjacent conductors. and the ratio of the distance between the conductor parts to the outer diameter of the conductor part is set to a specific range. It was found that by reducing the resistance in a well-balanced manner, a low resistance that could not be achieved with a conventional low-voltage, high-current side coil could be achieved, and that the loss of the transformer could be effectively reduced. Based on this knowledge, the present inventors have made further studies and completed the present invention.

That is, the object of the present invention has been achieved by the following means.
<1>
A low resistance coil made of an electric wire having a plurality of conductor portions, wherein all of the conductor portions satisfy the following conditions (1) and (2).
Conditions (1) The distance between adjacent conductors should be in the range of 170 to 540 μm.
Condition (2) The distance between the mutually adjacent conductor portions and the outer diameter of each of the mutually adjacent conductor portions satisfy the following formula (A).
Formula (A) Distance between adjacent conductors/outer diameter of conductors = 0.21 to 1.08
<2>
The low resistance coil according to <1>, wherein the conductor portion is a single conductor wire.
<3>
The conductor portion has an insulating film,
The low resistance coil according to <2>, wherein the distance between the conductors adjacent to each other is maintained by the thickness of the insulator filling the space between the conductors.
<4>
The low resistance coil according to <1>, wherein the conductor portion is formed by twisting a plurality of strands.
<5>
The conductor portion has an insulating film,
The low resistance coil according to <4>, wherein the distance between the mutually adjacent conductor portions is maintained by the thickness of the wire insulating layer between the mutually adjacent conductor portions and the thickness of the insulating coating.
<6>
The low resistance coil according to <3> or <5>, wherein the insulating coating has a layer structure of three or more layers.
<7>
A high-frequency high-output transformer comprising a primary side coil and a secondary side coil, wherein the low-voltage high-current side coil of the primary side coil and the secondary side coil is any one of <1> to <6> A high-power transformer for high frequencies, which is the low-resistance coil according to item 1.

In the description of the present invention, “mutually adjacent conductor portions” means a state in which two target conductor portions are arranged side by side with no other conductor portion interposed therebetween. Taking FIG. 21 as an example, among conductors 11a to 11f, conductors 11a and 11b, and conductors 11a and 11f are conductors adjacent to each other. On the other hand, the conducting wire 11a and the conducting wire 11c are arranged side by side with the conducting wire 11b interposed therebetween, so they are not mutually adjacent conductor portions. Also, since the conductors 11a and 11d are arranged with the conductors 11b and 11c interposed therebetween, they are not adjacent conductor portions. Similarly, the conducting wire 11a and the conducting wire 11e are arranged side by side with the conducting wire 11f interposed therebetween, so that they are not adjacent conductor portions.

In the description of the present invention, the term “insulating film” means a film that exists on the periphery of each conductor part and individually covers each conductor part, among the insulators that cover the conductor parts. The insulating film will be described with reference to FIGS. 2, 17 and 18 as examples.
In FIG. 2, the insulator 14a is not an insulating film in the present invention because it integrally covers all the conductor portions. In other words, in FIG. 2, each conductor does not have an insulating film individually covering the outer periphery thereof, but has an insulator integrally filling between the conductors or the outer periphery thereof. In FIG. 17, in the electric wire 10C, the insulator 14b exists on the outer periphery of each conductor portion formed by twisting a plurality of strands 13 (consisting of the conductor wire 11 and the strand insulating layer 12), and each conductor portion is individually Since it is covered, it is an insulating film.
In FIG. 18, the insulators 14b to 14d in the electric wire 10D are present on the outer periphery of each conductor formed by twisting a plurality of strands 13, and individually cover each conductor. be.

In the present specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits.

INDUSTRIAL APPLICABILITY The present invention can provide a low-resistance coil and a high-output transformer for high frequencies that has this coil as a low-voltage, high-current side coil and has reduced loss.

FIG. 1 is a schematic cross-sectional view showing an example of an electric wire (one conductor portion is one conductor wire) used in a conventional transformer. FIG. 2 is a schematic cross-sectional view showing an example of a preferable electric wire (one conductor portion is one conductor wire) used in the transformer of the present invention. FIG. 3 is a schematic cross-sectional view showing another example of a preferable electric wire (one conductor portion is one conductor wire) used in the transformer of the present invention. 4 is a schematic cross-sectional view showing a coil produced in Comparative Example 1. FIG. FIG. 5 is a schematic cross-sectional view showing the coil produced in Example 1-1. FIG. 6 is a schematic cross-sectional view showing the coil produced in Example 1-2. FIG. 7 is a graph showing the relationship between the distance between conductor parts/the outer diameter of the conductor part and the resistance value of the coil in a coil using electric wires of the same outer diameter (finished diameter) manufactured using seven conductor wires. Yes (frequency 30 kHz). FIG. 8 is a graph showing the relationship between the distance between conductor parts/the outer diameter of the conductor part and the resistance value of the coil in a coil using electric wires of the same outer diameter (finished diameter) manufactured using seven conductor wires. Yes (frequency 50 kHz). FIG. 9 is a graph showing the relationship between the distance between conductor parts/the outer diameter of the conductor part and the resistance value of the coil in a coil using electric wires of the same outer diameter (finished diameter) manufactured using seven conductor wires. Yes (frequency 150 kHz). FIG. 10 is a schematic cross-sectional view showing an example of an electric wire (one conductor portion is formed by twisting a plurality of strands) used in a conventional transformer. FIG. 11 is a schematic cross-sectional view showing an example of a preferred electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. 12 is a schematic cross-sectional view showing a coil produced in Comparative Example 2. FIG. 13 is a schematic cross-sectional view showing a coil produced in Example 2. FIG. FIG. 14 shows the distance between conductor parts / outer diameter of conductor part in a coil using electric wires with the same outer diameter (finished diameter), which is manufactured using seven litz wires made by twisting seven strands. It is a graph which shows the relationship with the resistance value of a coil (frequency of 30 kHz). FIG. 15 shows the relationship between the distance between conductor parts/the outer diameter of the conductor part in a coil using electric wires with the same outer diameter (finished diameter), which is produced using seven litz wires made by twisting seven strands. It is a graph which shows the relationship with the resistance value of a coil (frequency of 50 kHz). FIG. 16 shows the distance between conductors/outer diameter of the conductor in a coil using electric wires with the same outer diameter (finished diameter), which is manufactured using seven litz wires made by twisting seven strands. It is a graph which shows the relationship with the resistance value of a coil (frequency of 150 kHz). FIG. 17 is a schematic cross-sectional view showing still another example of a preferred electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. FIG. 18 is a schematic cross-sectional view showing still another example of a preferable electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. FIG. 19 is a schematic cross-sectional view showing still another example of a preferable electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. FIG. 20 is a schematic cross-sectional view showing still another example of a preferred electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. FIG. 21 is a schematic cross-sectional view showing still another example of a preferable electric wire (one conductor portion is one conductor wire) used in the transformer of the present invention. FIG. 22 is a schematic cross-sectional view showing still another example of a preferred electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. FIG. 23 is a schematic cross-sectional view showing still another example of a preferable electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. FIG. 24 is a schematic cross-sectional view showing still another example of a preferable electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. FIG. 25 is a schematic cross-sectional view showing still another example of a preferable electric wire (one conductor portion is formed by twisting a plurality of strands) used in the transformer of the present invention. FIG. 26 is a schematic cross-sectional view showing an example of the transformer (split winding transformer) of the present invention. FIG. 27 is a schematic cross-sectional view showing an example of the transformer (sandwich wound transformer) of the present invention. FIG. 28 is a schematic end view of the electric wire for explaining the outer diameter of the conductor portion of the electric wire used in the transformer of the present invention when the conductor portion is formed by twisting strands of wire. FIG. 29 is a schematic end view (partially enlarged view of FIG. 17) of an electric wire for explaining the distance between conductor portions when the conductor portion of the electric wire used in the transformer of the present invention is formed by twisting strands; be.

<<Low resistance coil and high output transformer for high frequency>>
A high-power transformer for high frequencies according to the present invention (hereinafter sometimes simply referred to as a transformer according to the present invention) comprises a primary coil and a secondary coil, wherein one of the primary coil and the secondary coil has a low voltage. The low-resistance coil of the present invention (hereinafter sometimes simply referred to as the coil of the present invention) is provided as the large-current side coil. The electric wire that constitutes the coil of the present invention has a plurality of conductor portions, and all the conductor portions satisfy the following conditions (1) and (2).
Conditions (1) The distance between adjacent conductors should be in the range of 170 to 540 μm.
Condition (2) The distance between the mutually adjacent conductor portions and the outer diameter of each of the mutually adjacent conductor portions satisfy the following formula (A).

Formula (A):
Distance between adjacent conductors (distance between conductors)/Outer diameter of conductors (conductor diameter) = 0.21 to 1.08

By using this wire for the coil of the present invention, the resistance value generated in this coil can be reduced, and the loss of a high-frequency, high-output transformer equipped with the coil of the present invention as a low-voltage, large-current side coil is lower than that of a conventional transformer. can be further reduced. Furthermore, it can also contribute to the reduction in size and weight in recent years.

<Electric wire>
The electric wire used for the coil of the present invention will be described, but the coil of the present invention is not limited to this.
As long as the electric wire used for the coil of the present invention has a plurality of conductor portions and an insulator covering the outer periphery of the conductor portions, other configurations are not particularly limited.
In the electric wire used for the coil of the present invention, in the electric wire B obtained by twisting the electric wires A, the electric wire A may be referred to as a "single electric wire". A and B are descriptive symbols and do not indicate specific wires.

Specific examples of the conductor portion include (i) a wire core (conductor itself), (ii) a wire core (litz wire) from which the outermost wire insulation layer is removed ("a wire made by twisting a plurality of wires ”), and the like.
The term "strand" means a wire having a wire insulation layer around the conductor, or a wire having a wire insulation layer around the conductor and an insulation coating around the wire insulation layer. A "litz wire" means a wire formed by twisting a plurality of strands.

In (i), the diameter of the conductor is the outer diameter of the conductor. Further, the distance between conductor portions is the shortest distance between conductor wires in conductor portions adjacent to each other.
If the cross section perpendicular to the axis of the conductor wire is not a perfect circle, the diameter of the conductor portion is the diameter of a perfect circle having the same area as the cross section.
The distance between the conductors of the condition (2) is the distance between the multiple conductors 11 in the process of extruding the insulator 14a in the configuration as shown in FIGS. ). In contrast, when the distance between conductors is maintained by an insulating film, it can be controlled by the thickness of the insulating film. That is, it is preferable that the distance between the conductors is maintained by the insulating film between the conductor portions, since the manufacturing efficiency can be further improved.

In (ii), the conductor portion means a plurality of strands arranged in the outermost row in the radial direction in a cross section perpendicular to the axis of the litz wire (in FIG. 28, strands other than the strands arranged in the center A portion defined by an imaginary circumscribing circle (circle indicated by a dashed line in FIG. 28) that circumscribes each of the six wires 13). In other words, it refers to a portion defined by a virtual circumscribed circle that circumscribes each portion of the wire arranged in the outermost row with respect to the radial direction of the litz wire, excluding the wire insulating layer existing radially outside. .

In (ii), the outer diameter of the conductor portion is the diameter C (conductor portion diameter C) of the virtual circumscribed circle that defines the conductor portion in a cross section perpendicular to the axis of the litz wire (see FIG. 28). The distance between conductor portions is the shortest distance D between a conductor wire forming one conductor portion and a conductor wire forming the other conductor portion in mutually adjacent conductor portions (see FIG. 29). Here, the above-mentioned strands arranged in the outermost row with respect to the radial direction of the litz wire are the strands located in the outermost row among the strands arranged adjacent to each other in the radial direction of the litz wire. say the line
The conductor portion diameter C can be adjusted by the outer diameter of the conductor wire, the thickness of the wire insulating layer, and the like, and can be measured or calculated by a standard method. If the virtual circumscribed circle in the cross section is not a perfect circle, the diameter of the conductor portion is the diameter of a perfect circle having the same area as the virtual circumscribed circle.
Regarding the distance between the conductors of the condition (2), in the case of the configuration as shown in FIG. to control. In contrast, in the configuration shown in FIG. 18, the distance between conductors can be controlled by the layer thickness of the strand insulating layer and the thickness of the insulating coating. That is, since the manufacturing efficiency can be further improved, it is preferable that the distance between the conductors is maintained by the wire insulating layer and the insulating coating between the conductor portions.

The outer diameter (finished diameter, eg, see F in FIGS. 17 to 25) of the electric wire used in the present invention is not particularly limited as long as the conductor portion satisfies the above conditions (1) and (2). The cross-sectional shape of the electric wire used in the present invention is not particularly limited, and the outer circumference and circumscribed circumference of the electric wire may be circular or rectangular (rectangular shape), but circular (round wire) is preferable.

In the present invention, the insulating coating forming the electric wire may be a single layer or multiple layers of two or more layers. In the present invention, the number of layers is determined by cross-sectional observation of the layers, regardless of the types and contents of the resins and additives forming the layers. Specifically, when observing the cross section of a certain layer at a magnification of 200 times, if no tree-ring boundaries can be identified, the total number of layers is set to 1, and if tree-ring boundaries can be identified, the number of layers in a layer is is (number of boundaries + 1).

Preferred forms of the electric wire used in the coil of the present invention are described below.
First, an electric wire in which one conductor portion is one conducting wire will be described by taking the electric wires in FIGS. 2, 3, 20 and 21 as examples.

In FIG. 2, the electric wire 100B is formed by twisting a plurality of conducting wires 11 (having a circular cross section) at intervals. In the electric wire 100B, one conducting wire 11 is a conductor portion and has seven conductor portions. The electric wire 100B has an insulator 14a that covers between the conductor portions and the outer periphery thereof. In the electric wire 100B, the conductor portion diameter C is the diameter of the conductor wire 11 . Further, the distance D between the conductor portions is the shortest distance between the conductor portions adjacent to each other. F indicates the outer diameter (finished diameter) of the electric wire 100B.

The electric wire 100C shown in FIG. 3 has the same configuration as the electric wire 100B shown in FIG. 2 except that the conductor 11 has a different diameter.

The electric wire 100H shown in FIG. 20 is the electric wire 100B shown in FIG. , and has the same configuration as the electric wire 100B shown in FIG.

The electric wire 100I shown in FIG. 21 has the same configuration as the electric wire 100B shown in FIG. 2, except that the conductor 11 at the center of the electric wire 100B shown in FIG.

In the present invention, the electric wire having one conductor portion is not limited to the electric wire shown in the drawings. For example, the number of conductors can be changed as appropriate. The number of conducting wires is the same as the number of strands forming a litz wire, which will be described later.

An electric wire in which the conductor portion is a litz wire from which the outermost wire insulating layer is removed will be described with reference to the insulated wires shown in FIGS. 11, 17 to 19 and 21 to 26 as examples.

The electric wire 10B shown in FIG. 11 is obtained by twisting single electric wires 100E and covering the stranded wire with an insulator 14a. This electric wire 100E has a conductor portion formed by twisting strands 13 composed of conductors 11 and strand insulating layers 12 (see FIG. 28 and the above (ii)). This conductor portion is covered with an insulator 14b (insulating film).

An electric wire 10C shown in FIG. 17 has the same configuration as the electric wire 10B shown in FIG. 11 except that the single electric wire 100E is not covered with the insulator 14a.

The electric wire 10D shown in FIG. 18 has the same configuration as the electric wire 10C shown in FIG. 17, except that the electric wire 10D shown in FIG. The single electric wire 100F is the same as the single electric wire 100E in FIG. 17 except that the insulator 14b is covered with the insulator 14c, and the insulator 14c is covered with the insulator 14d. is the configuration.

The electric wire 10E shown in FIG. 19 has the same configuration as the electric wire 10C shown in FIG. 17 except that the single electric wire 100G is used instead of the single electric wire 100E. The single electric wire 100G has the same configuration as the single electric wire 100E except that the litz wire 16b has more strands than the litz wire 16a of the single electric wire 100E.

The electric wire 10F shown in FIG. 22 has the same configuration as the electric wire 10C shown in FIG. 17, except that the electric wire 10C shown in FIG. 17 does not have the central single electric wire 100E.

The electric wire 10G shown in FIG. 23 has the same configuration as the electric wire 10C shown in FIG. 17 except that the insulated wire 17 is used instead of the single electric wire 100E in the center of the electric wire 10C shown in FIG. . The insulated wire 17 only needs to have bendability for winding, and a specific example thereof is a wire obtained by twisting a plurality of nylon wires.

The electric wire 10H shown in FIG. 24 has the same configuration as the electric wire 10C shown in FIG. 17 except that the electric wire 10C shown in FIG. be.

The electric wire 10I shown in FIG. 25 has the same configuration as the electric wire 10C shown in FIG. 17 except that the single electric wire 100J is used instead of the single electric wire 100E in the electric wire 10C shown in FIG. The litz wire 16c of the single electric wire 100J is obtained by passing the litz wire 16a of the single electric wire 100E through a circular die and compressing it into a circular shape so as to eliminate the space between the wires. The electric wire 10I can have the same finished diameter as the electric wire 10C by using a conductor wire having an outer diameter larger than that of the electric wire 10C. Therefore, the electric wire 10I has a conductor cross-sectional area larger than that of the electric wire 10C, thereby reducing the direct current resistance, while the distance between the conductors is further increased, so that the proximity effect is further reduced, and the alternating current resistance can be further reduced.

In the present invention, the electric wire in which the conductor portion is a litz wire from which the outermost wire insulating layer is removed is not limited to the electric wire shown in the drawings. For example, the number of unit wires can be changed as appropriate.

In the electric wire used in the present invention, all conductor portions satisfy the above conditions (1) and (2), thereby suppressing an increase in the finished diameter of the electric wire, reducing the proximity effect, and increasing the resistance value of the coil. can be reduced. Although the reason for this is not clear, it is considered as follows.
Since the distance between the conductors is large (condition (1)), the AC resistance caused by the proximity effect is reduced. By thickening the insulation coating of the wire core, the distance between the conductor portions can be increased. However, increasing the thickness of the insulation film on the wire core increases the finished diameter of the wire. Therefore, in the electric wire used in the present invention, the diameter of the conductor portion is reduced. If the diameter of the conductor is made smaller, it becomes less susceptible to the magnetic field, but the DC resistance value increases. In the electric wire used in the present invention, the diameter of the conductor portion satisfies a specific relationship with the distance between the conductor portions even though the diameter of the conductor portion is reduced (condition (2)). As a result, it is considered that the electric wire used in the present invention can suppress an increase in the DC resistance value, further reduce the AC resistance value, lower the resistance value of the coil, and reduce the loss of the transformer.
In addition, since the raw material cost of resin, which is an insulating film, is generally lower than that of copper, which is a conductor, the electric wire used in the present invention can reduce costs compared to conventional designs that improve the space factor.

- Core -
The wire core used in the present invention is not particularly limited in other configurations as long as the conductor portion of the electric wire used in the present invention satisfies the above conditions (1) and (2). As for the form of the wire core, the form in which the wire core is composed of the conductor itself (forms shown in FIGS. 2, 3, and 21) and the form in which the wire core is composed of a litz wire (a wire made by twisting a plurality of strands). forms (forms of FIGS. 11, 17, 18, 19, 20, 22, 23, 24, and 25).

(conductor)
As the conducting wire that constitutes the wire core, a wire that has conventionally been used in windings for coils or the like can be used. Preferably, a copper wire made of low-oxygen copper or bare copper having an oxygen content of 30 ppm or less (more preferably 20 ppm or less) is used.
The cross-sectional shape of the conducting wire may be circular or rectangular (rectangular), but circular is preferable.
The outer diameter φ (wire diameter) of the conducting wire is not particularly limited as long as it satisfies the above conditions (1) and (2).

(Insulator)
When the wire core is a litz wire, each wire constituting the litz wire has an insulating layer (wire insulating layer) formed around the conductor wire. This insulator preferably has a wire insulating layer (also referred to as an enamel layer) containing preferably a thermosetting resin as a resin component.

As the thermosetting resin for forming the wire insulating layer, any thermosetting resin commonly used in electric wires can be used without particular limitation. Examples thereof include polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polyesterimide (PEsI), polyurethane (PU), polyester (PEst), polybenzimidazole, melamine resin, epoxy resin, and the like. Among them, polyamideimide, polyimide, polyetherimide, polyesterimide, polyurethane or polyester is preferable. One or two or more thermosetting resins may be contained.

This wire insulation layer may contain various additives commonly used in electric wires. In this case, the content of the additive is not particularly limited, but is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, with respect to 100 parts by mass of the resin component.

The thickness of the wire insulating layer is not particularly limited, but is preferably 8 to 18 μm, for example, from the viewpoint of ensuring insulation between wires and increasing the lamination factor of the conductor wires.

A strand insulating layer can be formed by a normal method. For example, it is preferable to apply a varnish made of a resin component such as a thermosetting resin to the outer periphery of the conductive wire and bake the varnish. This varnish contains a resin component, a solvent, and, if necessary, a curing agent for the resin component or various additives. The solvent is preferably an organic solvent, and a solvent that can dissolve or disperse the resin component is appropriately selected.
A usual method can be selected as the varnish coating method, and examples thereof include a method using a varnish coating die having an opening having a shape similar or substantially similar to the cross-sectional shape of the conductor. Baking of the varnish is usually carried out in a baking furnace. The conditions at this time cannot be determined unambiguously according to the type of resin component or solvent, but for example, conditions include a furnace temperature of 400 to 650° C. and a passage time of 10 to 90 seconds.

As the wire used in the present invention, for example, a wire composed of a conductor wire 11 and a wire insulating layer 12 shown in FIG. 11 is preferable.

(litz wire)
A litz wire is a stranded wire formed by twisting a plurality of strands, as described above.
As described above, the strands forming the litz wire are composed of the conductor wire and the strand insulation layer.

The number of strands forming the litz wire is not particularly limited as long as it is 2 or more, but considering the alignment of the strands, it is preferable to have 7 or more, with 6 strands arranged around one strand. Considering practical workability, the number is preferably 100 or less. Considering especially alignment, the number is more preferably 7 to 37.
The arrangement of the strands, the twisting direction, the twisting pitch, etc. when twisting the strands can be appropriately set according to the application.

－ Insulating film －
As described above, the “insulating film” means a film that exists on the periphery of the conductor part and individually covers each conductor part among the insulators that cover the conductor parts. As the insulating film, a layer (thermoplastic resin layer) containing a thermoplastic resin, which will be described later, as a resin component is preferable. The thickness of the thermoplastic resin layer is not particularly limited as long as the above condition (2) is satisfied. This insulating coating is preferably a layer (extrusion coating layer) formed by extrusion molding (extrusion coating).

The insulating coating can have a laminated structure of two or more layers as described above, preferably three or more layers, and more preferably a laminated structure of three to five layers. With a laminated structure of three or more layers, it is possible to secure a sufficient creepage distance for the electric wire, so that in the coil of the present invention, it is possible to omit the insulating tape that is normally used to ensure insulation. This is also effective in reducing the size of the transformer.
When the insulating coating has a laminated structure, the thickness of each layer is not particularly limited as long as the total thickness of each layer satisfies the aforementioned radius difference and outer diameter ratio. For example, when having an inner layer, an intermediate layer and an outer layer, the thickness of each layer may be the same or different. It is preferable that the thickness of each layer is uniform because the manufacturing conditions can be adjusted.

The electric wire 100F shown in FIG. 18 is mentioned as an electric wire having an insulating film of laminated structure. 100F shown in FIG. 18 has an insulating film of a three-layer laminated structure consisting of insulators 14b to 14d. All of the insulators 14b to 14d are set to have the same thickness. In the present invention, there is no particular limitation on the relationship between the thicknesses of the constituent layers in the insulating coating of the laminated structure.

The insulating coating preferably contains a thermoplastic resin as a resin component. The thermoplastic resin is not particularly limited as long as it is a thermoplastic resin commonly used for electric wires or windings. For example, polyamide (nylon), polyacetal (POM), polycarbonate (PC), polyphenylene ether (PPE, including modified polyphenylene ether), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), ultra In addition to general-purpose engineering plastics such as high molecular weight polyethylene, polysulfone (PSF), polyethersulfone (PES), polyphenylene sulfide (PPS), polyarylate (PAR), polyetherketone (PEK), polyaryletherketone (PAEK), Tetrafluoroethylene/ethylene copolymer (ETFE), polyether ether ketone (including PEEK and modified PEEK), polyether ketone ketone (PEKK), tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (PFA), polytetra Super engineering plastics such as fluoroethylene (PTFE), thermoplastic polyimide resin (TPI), thermoplastic polyamide-imide (TPAI), liquid crystal polyester, polymer alloys based on polyethylene terephthalate or polyethylene naphthalate, ABS/polycarbonate, Polymer alloys containing the above engineering plastics such as nylon 6,6, aromatic polyamide resins, polyphenylene ether/nylon 6,6, polyphenylene ether/polystyrene, and polybutylene terephthalate/polycarbonate can be mentioned. One or two or more thermoplastic resins may be contained.

When the insulating coating has a laminated structure, the maximum content of the resin component in each layer may be the same or different.

The insulating coating may contain various additives commonly used in electric wires. In this case, the content of the additive is not particularly limited, but is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, with respect to 100 parts by mass of the resin component.

When the wire core is a litz wire, the insulation coating can be formed by extrusion molding a resin composition on the outer periphery of the litz wire. The resin composition contains the resin component described above and, if necessary, various additives. The extrusion method cannot be uniquely determined according to the type of the resin component, but for example, using an extrusion die having an opening that is similar or substantially similar to the cross-sectional shape of the litz wire, the resin component is extruded at a temperature above the melting temperature. A method of extruding at temperature is mentioned.
The insulation film is not limited to extrusion molding, and can be formed in the same manner as the enamel layer using a varnish containing the above-mentioned thermoplastic resin, solvent, etc., and various additives if necessary.
In the present invention, as described above, the thickness of the insulation coating is increased contrary to that of the conventional electric wire. Therefore, from the viewpoint of productivity, it is preferable to form the insulation coating by extrusion molding.

(Litz wire structure)
A litz wire that is preferable as the configuration of the wire core of the electric wire of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
In each figure, the contour shape of the electric wire is illustrated as ring-shaped, but in the electric wire used in the present invention, the shape of the outer contour line is not limited to ring-shaped and can be determined as appropriate. For example, the contour shape of the electric wire includes an elliptical shape, a flat knurled shape (a gear shape or a wavy shape), etc., in addition to the circular shape.

An example of a preferred litz wire for use in the present invention is a litz wire 16a shown in FIG.
The litz wire 16a is formed by twisting seven strands 13 (constituted of the conducting wire 11 and the strand insulating layer 12). The litz wire 16 a is formed by twisting seven strands 13 in a pattern in which six strands 13 are arranged around one strand 13 . The six strands 13 are all arranged in the outermost row in the radial direction and are strands that determine the conductor portion. Each strand 13 has a conductor 11 and a strand insulation layer 12 disposed on the outer peripheral surface of the conductor 11 .

Another preferred example of the litz wire used in the present invention is the litz wire 16b shown in FIG.
A litz wire 16b shown in FIG. 19 is the same as the litz wire 16a except that 19 wires 13 are twisted together. The litz wire 16b has a structure in which a total of 12 wires 13 are arranged and twisted so as to form a hexagon in the cross section shown in FIG. 19 outside the litz wire 16a.

Another preferred example of the litz wire used in the present invention is the litz wire 16c shown in FIG. The litz wire 16c is obtained by twisting seven strands 13 in the same manner as the litz wire 16a, passing the strands through a circular die, and compressing them into a circle so that the spaces between the strands are eliminated.

In the present invention, as the structure of the litz wire used in the present invention, a structure obtained by appropriately combining the respective structures of the litz wires 16a to 16c can be used.

<Electric wire used for high-voltage, low-current side coil>
The electric wire used for the high-voltage, small-current side coil in the transformer of the present invention is not particularly limited, and a normal electric wire used for the high-voltage, small-current side coil of the transformer can be used. As such an electric wire, for example, there is a litz wire used for a secondary winding, which is described in Patent Document 1. Moreover, the electric wire used for the above-mentioned invention can also be used.

<Coil>
The coil of the present invention is obtained by winding the electric wire used in the present invention on the outer peripheral surface of the core of the bobbin. Therefore, the coil of the present invention is the same as the conventional coil except that the electric wire used in the present invention is used as described above.

The coil of the present invention will be described with reference to FIGS. 5, 6 and 13 as examples.

The coil 4B shown in FIG. 5 is obtained by winding (10 turns) the electric wire 100B used in the present invention around the outer peripheral surface of the core 6 of the bobbin 5 (the inner peripheral surface of the slot 7 formed in the bobbin 5).

A coil 4C shown in FIG. 6 is obtained by winding (10 turns) the electric wire 100C used in the present invention around the outer peripheral surface of the core 6 of the bobbin 5. As shown in FIG.

A coil 4E shown in FIG. 13 is obtained by winding (20 turns) the electric wire 10B used in the present invention around the outer peripheral surface of the core 6 of the bobbin 5. As shown in FIG.

The high-voltage, low-current side coil of the transformer of the present invention is obtained by winding the above-described known electric wire or the electric wire used in the present invention on an outer peripheral surface different from the outer peripheral surface of the core around which the electric wire used in the present invention is wound. (See FIG. 26). The high-voltage, low-current side coil of the transformer of the present invention is obtained by winding the above-described known electric wire or the electric wire used in the present invention around the outer peripheral surface of the electric wire used in the present invention wound around the core. (See FIG. 27).

In the present invention, the material (iron core, magnetic core, air core, etc.) and size of the core around which each electric wire is wound are appropriately selected according to the application. Also, the method of winding the electric wire, the number of turns (two or more turns), the pitch, etc., are appropriately selected according to the application.

<Transformer of the Present Invention>
The transformer of the present invention is the same as the conventional transformer except that the above-described coil of the present invention is used as the low-voltage, high-current side coil.
A transformer is a device for converting the voltage level of AC power using electromagnetic induction. A transformer generally has two coils, an input side coil (primary side coil) and an output side coil (secondary side coil). In a transformer, an alternating current is passed through a primary coil to generate an alternating magnetic field, which is received by a magnetically coupled secondary coil to generate and output current again. At this time, the ratio of the voltages generated in the primary coil and the secondary coil is the same as the ratio of the number of turns of the wire in each coil. is determined.
A transformer in which the voltage of the primary coil is set relatively higher than that of the secondary coil is called a step-down transformer. In this step-down transformer, a high-voltage, small-current current flows through the primary coil (high-voltage, small-current side coil), and a low-voltage, large-current current flows through the secondary-side coil (low-voltage, large-current side coil). On the other hand, a transformer in which the voltage of the primary coil is set relatively lower than that of the secondary coil is called a step-up transformer. In this step-up transformer, a low-voltage, large-current current flows through the primary side coil (low-voltage, large-current side coil), and a high-voltage, small-current current flows through the secondary side coil (high-voltage, small-current side coil).

The transformer of the present invention, whether it is a step-down transformer or a step-up transformer, uses a coil wound with the wire used in the present invention as a low-voltage, large-current side coil.
The transformer of the present invention is not particularly limited in its structure, size, etc., as long as it has a coil wound with the above electric wire used in the present invention as a low-voltage, high-current side coil. For example, since the voltage and current value of the current are relatively determined for the primary side coil and the secondary side coil, the present invention can be applied to the high voltage small current side coil in addition to the low voltage large current side coil. A coil obtained by winding the above electric wire to be used can also be used.

In the transformer of the present invention, the current flowing through each coil is appropriately determined according to the application and characteristics, as described above. Although it is not particularly limited, for example, the current flowing through the low-voltage high-current side coil preferably has a voltage of 100 V or more and less than 500 V and a current value of 1 A or more and 30 A or less. , the current flowing through the high-voltage, low-current side coil preferably has a voltage of 500 V or more and 4000 V or less and a current value of 0.3 A or more and less than 1 A.

In the transformer of the present invention, the core and bobbin can be appropriately selected from shapes, sizes and materials used in ordinary transformers.

The transformer of the present invention may have the above configuration, and examples thereof include the transformer shown in FIG. 26 or FIG.

A transformer 1A shown in FIG. 26 has a low-voltage, large-current side coil 4B shown in FIG. The secondary coils 2 are arranged in a row in the axial direction with their axes aligned with each other. The low-voltage, large-current side coil 4B has an electric wire 100B wound around the outer peripheral surface of the core 6B of the bobbin 5B. wire is wound.

A transformer 1B shown in FIG. 27 has a low-voltage, large-current side coil 4B shown in FIG. The secondary coil 2 is wound around the same core via a three-layer insulating tape. A wire 100B is wound around the outer peripheral surface of the core 6 of the bobbin 5 in the low-voltage, high-current side coil 4B. The high-voltage, small-current side coil 2 has a wire composed of a conductor 11A and an insulating layer 12B wound around the outer circumference of a three-layer insulating tape wound around the outer circumference of the low-voltage, large-current side coil 4B.

Since the transformer of the present invention has a coil wound with wires satisfying the above conditions (1) and (2) in all conductor portions as a low-voltage, high-current side coil, it is a high-output transformer for high frequencies. Also, as described above, the loss can be effectively suppressed.

<Application>
INDUSTRIAL APPLICABILITY The transformer of the present invention is suitably used in applications requiring high output for high frequencies and applications in which a large amount of current flows. For example, it is more preferably used as an alternating current (AC) / direct current (DC) converter, which transforms and rectifies an alternating current commercial power supply and converts it into a direct current with a voltage suitable for electrical and electronic equipment, specifically a microwave oven. It is suitably used as each transformer for generating a high voltage to be supplied to the magnetron in the power supply board for the.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these.

<Example 1>
- Example 1-1 -
In this example, a coil 4B shown in FIG. 5 was produced using the electric wire 100B shown in FIG. 2 and evaluated.
First, the electric wire 100B shown in FIG. 2, which is used for the low-voltage high-current side coil 4B, was produced.
Seven conductive wires 11 (copper wires with a circular cross section) having an outer diameter of 0.85 mm were twisted together in the following manner.
With one conducting wire 11 as the center, the other six conducting wires 11 were arranged around the centered conducting wire 11 at every 60° and twisted together while maintaining the distance between the conductors at 186 μm. (Twist pitch 77.7 mm).
Subsequently, a polyethylene terephthalate (PET) resin was extruded so that the outer diameter (finished diameter) of the resulting electric wire was 3.108 mm, thereby producing an electric wire 100B having the conducting wire 11 and the insulator 14a.
The produced electric wire 100B had a conductor portion (conductor 11) diameter of 0.85 mm and an outer diameter (finished diameter) of the electric wire 10B of 3.108 mm. In this electric wire 100B, the distance between the conductor portions 11 adjacent to each other is 186 μm, and the distance between the conductor portions/the diameter of the conductor portion=0.219.
As shown in FIG. 5, the electric wire 100B is wound on the outer peripheral surface of the core 6 by two rows of 5 turns (parallel number: 2) for a total of 10 turns (number of turns) to form a low-voltage high-current side coil. 4B was produced.
The core 6 and the bobbin 5 used had a diameter of 30.2 mm on the outer peripheral surface (inner peripheral surface of the slot 7) around which the electric wire 100B was wound, and a width of the slot (axial length) of 18 mm (Fig. 5 (schematic cross-sectional view). ) do not exactly match the above dimensions given in Example 1-1).

- Example 1-2 -
In this example, the electric wire 100C shown in FIG. 3 was used to fabricate a coil 4C shown in FIG. 6 and evaluated.
An electric wire 100C shown in FIG. 3 was produced in the same manner as in Example 1-1, except that seven conductor wires 11 with an outer diameter of 0.5 mm were used and the distance between the conductors was set to 536 μm.
The produced electric wire 100C had a conductor portion (conductor 11) diameter of 0.5 mm and an outer diameter (finished diameter) of 3.108 mm. In this electric wire 100C, the distance between the conductor portions 11 adjacent to each other is 536 μm, and the distance between the conductor portions/the diameter of the conductor portion=1.072.
A coil 4C shown in FIG. 6 was produced in the same manner as in Example 1-1, except that this electric wire 100C was used.

- Example 1-A -
In this example, the following coils were produced and evaluated.
In the same manner as in Example 1-1, an electric wire having a distance between conductors/diameter of conductor portion=0.727 was produced. A coil was produced using this electric wire in the same manner as in Example 1-1.

<Comparative Example 1>
In this example, a coil 4A shown in FIG. 4 was produced using the electric wire 100A shown in FIG. 1 and evaluated.
A wire 13 having a wire insulating layer 12 (enamel layer) with a thickness of 18 μm by applying polyamide-imide resin varnish to the surface of a conducting wire 11 (copper wire with a circular cross section) with an outer diameter of 1.0 mm and baking it. was made. The electric wire 100A shown in FIG. 1 was produced by bundling and twisting seven of these strands (twisting pitch: 25.9 mm).
The produced electric wire 100A had a conductor portion (leading wire 11) diameter of 1.0 mm, and an outer diameter (finished diameter) of the electric wire 100A of 3.108 mm. In this electric wire 100A, the distance between the conductor portions 11 adjacent to each other is 36 μm (the thickness of the enamel layer×2), and the distance between the conductor portions/the diameter of the conductor portion=0.036.
A coil 4A shown in FIG. 4 was produced in the same manner as in Example 1-1 except that this electric wire 100A was used.

<Resistance measurement>
Using the coils produced in Examples 1-1, 1-2, 1-A and Comparative Example 1-1, the resistance value generated in the coil by changing the frequency was measured with a precision LCR meter (trade name: E4980A, KEY SIGHT It was measured using TECHNOLOGIES (former Agilent).
Specifically, in the range of about 40 mm from both ends of each low-voltage, high-current side coil, the conductor wire exposed by peeling off the insulator was covered with solder. The soldered portion was sandwiched between measurement jigs of a precision LCR meter and pressed down to sufficiently reduce the contact resistance, and the resistance value was measured. The obtained resistance value was divided by the coil length excluding the soldered portion to calculate the resistance value per meter (Ω/m).

7 to 9 show the relationship between the resistance value at frequencies of 30 Hz, 50 Hz and 150 Hz and the distance between the conductor portions/the diameter of the conductor portion for the coil using the electric wire made using seven conductor wires.
Table 1 shows the resistance values of the coils of Examples 1-1, 1-2, 1-A and Comparative Example 1-1 at each frequency.

<Notes to the table>
D/C: distance between conductors/diameter of conductor

7 to 9 and Table 1 reveal the following.
At high frequencies above 30 kHz, the proximity effect becomes non-negligible. However, when all the conductors of the electric wire used for the low-voltage, high-current side coil satisfy the above conditions (1) and (2), the balance between the DC resistance and the AC resistance is improved, and compared to the conventional coil (Comparative Example 1), It can be seen that a coil with a smaller resistance value can be realized by increasing the resistance value (Embodiment 1-1). Also, from FIG. 7, it can be seen that the resistance value of the coil is the smallest when D/C=0.219 (Example 1-1).
The higher the frequency, the greater the proximity effect and the greater the resistance value of the coil. However, compared with the coil of Comparative Example 1, it can be seen that the low-voltage, high-current side coil of the example is excellent in the effect of reducing the resistance value (Examples 1-1 and 1-A at a frequency of 50 kHz; Examples 1-1, 1-A and 1-2). Also, from FIG. 8, it can be seen that the resistance value of the coil is the lowest when D/C=0.727 (Example 1-A) at a frequency of 50 kHz. From FIG. 9, it can be seen that the resistance value of the coil is the lowest when D/C=1.072 (Example 1-2) at a frequency of 150 kHz.
A step-up transformer used in an inverter type microwave oven generally has an operating frequency of 30 to 150 kHz. Therefore, when the step-up transformer having the low-voltage, high-current side coil of Example 1 is used in an inverter-type microwave oven, the resistance of the low-voltage, high-current side coil can be effectively reduced, and the loss of the step-up transformer can be reduced.

<Example 2>
- Example 2-1 -
In this example, a coil 4E shown in FIG. 13 was produced using the electric wire 10B shown in FIG. 11 and evaluated.
A wire 13 having a wire insulating layer 12 (enamel layer) with a thickness of 8 μm by applying polyamide-imide resin varnish to the surface of a conducting wire 11 (copper wire with a circular cross section) with an outer diameter of 0.15 mm and baking it. was made. Seven of these strands were bundled and twisted at a twist pitch of 12.45 mm to obtain a litz wire 16a. A PET resin was extruded from the litz wire 16a so as to have an outer diameter of 0.972 mm to produce an electric wire 100E.
Subsequently, seven electric wires 100E are twisted together at a twist pitch of 72.9 mm, and then PET resin is extruded so that the outer diameter (finished diameter) is 2.916 mm to obtain the electric wire 10B shown in FIG. rice field.
The produced electric wire 10B has a conductor portion diameter of 482 mm {conductor 11 diameter 0.15 mm x 3 wires) + (strand wire insulating layer 120.008 mm x 4 layers) = 0.482 mm}. In this electric wire 10B, the distance between adjacent conductor portions is 490 μm, and the distance between conductors/conductor portion diameter=1.017.
A low-voltage, high-current side coil 4E shown in FIG. 13 was fabricated in the same manner as in Example 1-1, except that the electric wire 10B was used and the total number of turns was 20.

- Example 2-A -
In this example, the following coils were produced and evaluated.
In the same manner as in Example 2-1, an electric wire having a distance between conductors/diameter of conductor portion=0.224 was produced. A coil was produced using this electric wire in the same manner as in Example 2-1.

- Example 2-B -
In this example, the following coils were produced and evaluated.
In the same manner as in Example 2-1, an electric wire having a distance between conductors/diameter of conductor portion=0.519 was produced. A coil was produced using this electric wire in the same manner as in Example 2-1.

<Comparative Example 2>
In this example, a coil 4D shown in FIG. 12 was produced using the electric wire 10A shown in FIG. 10 and evaluated.
A wire 13 having a wire insulating layer 12 (enamel layer) with a thickness of 9 μm by applying polyamide-imide resin varnish to the surface of a conducting wire 11 (copper wire with a circular cross section) with an outer diameter of 0.3 mm and baking it. was made. Seven of these wires were bundled and twisted at a twist pitch of 23.85 mm to obtain a litz wire 16a. An electric wire 100D was obtained by covering and fixing the litz wire 16a with an insulating tape having a thickness of 9 μm.
Subsequently, seven electric wires 100D were twisted together at a twist pitch of 72.9 mm to fabricate the electric wire 10A shown in FIG.
The prepared electric wire 10A has a conductor portion diameter of 0.936 mm {conductor diameter 0.3 mm × 3 pieces) + (wire insulating layer 0.009 mm × 4 layers) = 0.936 mm}, the outer diameter of the electric wire 10A ( Finished diameter) was 2.916 mm. In this electric wire 10A, the distance between adjacent conductors is 36 μm, and the distance between conductors/conductor diameter=0.038.
A low-voltage, high-current side coil 4D shown in FIG. 12 was fabricated in the same manner as in Example 1-1, except that the electric wire 10A was used.

<Resistance measurement>
Using the coils produced in Example 2 and Comparative Example 2, the resistance generated in the coils was measured by changing the frequency in the same manner as in Example 1.

The relationship between the resistance value at frequencies of 30 Hz, 50 Hz and 150 Hz and the distance between the conductors/diameter of the conductor is measured for a coil using an electric wire made by using seven litz wires made by twisting seven strands. This is shown in FIGS. 14-16.
Table 2 shows the resistance values of the coils of Example 2 and Comparative Example 2 at each frequency.

Since the coil of Example 2 uses more wires (the number of turns) than the coil of Example 1, the proximity effect between wires is strengthened and a large AC resistance is generated. However, as shown in FIGS. 14 to 16 and Table 2, the low-voltage, high-current side coil wound with the electric wire specified in the present invention is similar to Example 1, and Example 2-A has a frequency of 30 kHz or more. At high frequencies, an increase in resistance can be suppressed. In addition, in Examples 2-A and 2-B at a frequency of 50 kHz and Examples 2-1, 2-A and 2-B at a frequency of 150 kHz, the higher the frequency, the smaller the resistance ratio to the coil of Comparative Example 2. , excellent resistance reduction effect. Therefore, it can be seen that when the step-up transformer having the low-voltage, high-current side coil of Example 2 is used in an inverter-type microwave oven, the resistance of the low-voltage, high-current side coil can be effectively reduced, and the loss of the step-up transformer can be reduced.

From Examples 1 and 2, it can be seen that the coil using the electric wire specified in the present invention exhibits a small resistance when used in a transformer as a low-voltage, high-current side coil, and can effectively reduce the loss of the transformer.

1A, 1B Transformer 2 Primary side coil (low voltage large current side coil)
3 Secondary side coil (High voltage, small current side coil)
4A to 4D Coil 5, 5A, 5B Bobbin 6, 6A, 6B Core 7 Slot 11A, 11, 11a to 11f Wire core (conductor)

12 wire insulation layer (enamel layer)
12B Insulating layer 13 Wires 14a to 14d Insulator 15 Insulating tape 16a to 14c Wire core (litz wire)
17 Insulated wire 18B Three-layer insulating tape 10A to 10I Wire 100A to 100H Wire C Conductor diameter D Distance between conductors F Outer diameter (finished diameter)
G Diameter of insulated wire 17

Claims (7)

A low resistance coil made of an electric wire having a plurality of conductor portions, wherein all of the conductor portions satisfy the following conditions (1) and (2).
Conditions (1) The distance between adjacent conductors should be in the range of 170 to 540 μm.
Condition (2) The distance between the mutually adjacent conductor portions and the outer diameter of each of the mutually adjacent conductor portions satisfy the following formula (A).
Formula (A) Distance between adjacent conductors/outer diameter of conductors = 0.21 to 0.727 2. The low resistance coil according to claim 1, wherein said conductor portion is a single wire. The conductor portion has an insulating film,
3. A low resistance coil according to claim 2, wherein the distance between said adjacent conductor portions is maintained by the thickness of an insulator filling said conductor portions.
However, the insulating film is a film that exists on the outer periphery of each of the plurality of conductors in the insulator and individually covers each of the conductors. 2. The low resistance coil according to claim 1, wherein said conductor portion is formed by twisting a plurality of strands. The conductor portion has an insulating film,
5. The low resistance coil according to claim 4, wherein the distance between said mutually adjacent conductor portions is maintained by the thickness of said wire insulating layer between said mutually adjacent conductor portions and the thickness of said insulating coating. 6. The low resistance coil according to claim 3, wherein said insulating coating has a layer structure of three or more layers. A high-frequency high-output transformer comprising a primary side coil and a secondary side coil, wherein the low-voltage high-current side coil of the primary side coil and the secondary side coil is any one of claims 1 to 6. A high-power transformer for high frequencies, which is the low-resistance coil according to .

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