JPH05263377A - Litz wire - Google Patents

Abstract

PURPOSE:To prevent AC resistance of a litz wire from increasing by influence of a proximity effect between the middle wire bundle and the peripheral wire bundles. CONSTITUTION:In a litz wire prepared by twisting plural wire bundles respectively composed of plural insulated fine wires, the diameter of each insulated fine conductive wire used for the middle wire bundle existing at the middle part is designed so as to be larger than that of insulated fine wires used for other wire bundles and the outer diameter dimension of the middle wire bundle existing at the middle part in a litz wire having the above-mentioned structure is designed so as to be larger than that of other wire bundles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a litz wire for use as a high-frequency electric wire used as a winding material for transformers and chokes and wiring materials in equipment.

[0002]

2. Description of the Related Art Conventionally, there has been a single wire as a high frequency electric wire used for a winding material of a transformer or a choke, in which a central conductor is a metal such as copper, iron or brass and an outer cover is covered with an insulating film such as formant or enamel. There is also a litz wire formed by twisting a plurality of the above-mentioned insulated single wires having a wire diameter of 0.02 to 0.5 mmφ for the purpose of suppressing an increase in AC resistance due to the skin effect of the wire material at high frequencies, which is also a drawback of the single wires. These single-line litz wires are shown in Figure 4.
The structure is as shown in. 1 is a metal conductor, 2 is an insulating jacket, 3 is an insulating thin wire, 4 is a bundled wire in which a plurality of insulating thin wires are twisted,
5 is an insulating fiber such as Teflon. The single wire in (a) has a diameter of 0.
The material of the insulating jacket 2 is 02 mmφ to 3.2 mmφ, and the material is a single wire made of enamel. The litz wire in (b) has a diameter of 0.02 mmφ
To 0.5mmφ insulating thin wires 3 are twisted together to form a bundled wire 4, and 5 to 7 pieces of this bundled wire are twisted and the exterior is covered with insulating fiber 5 such as Teflon. The total number is several hundreds. ~
Reach thousands.

[0003]

However, when these wire materials are used as a winding material such as a transformer or a choke which operates at a high frequency or a wiring material through which a high frequency current flows, the following problems occur. In the conventional single wire structure (a), when the frequency is increased, the effect of the skin effect of the wire is increased, the AC resistance is increased, and the loss of the transformer and the choke is increased. Similarly, in the litz wire structure of (b), the increase in AC resistance due to the skin effect of the wire is suppressed, but the increase in frequency causes the AC resistance due to the proximity effect between the central bundle and the surrounding bundle. As a result, the loss of transformers and chokes also increased.

[0004]

[Table 1]

[0005]

[Table 2]

[0006]

[Table 3]

Table 1 shows an example of AC resistance of each bundle of litz wires shown in FIG. 4 (b). Table 1 is the absolute value of AC resistance, Table 2 is the relative resistance value of the other bundle wire when the AC resistance at each frequency of the central conductor located at the center is 100, and Table 3 is the AC resistance of 1 KHz of each bundle wire. It is a relative resistance value when set to 100. As shown in the table, there is little variation in the resistance values other than the center bundle wire (center conductor), but the center bundle wire (center conductor) has a shorter wire length than other bundle wires at low frequencies, so the resistance is higher than that of other bundle wires. Is small, and the resistance is higher than other bundles at high frequencies due to the proximity effect from other bundles. The difference in resistance causes the following problems. When a high-frequency current flows through the central bundle of litz wire, it exerts a proximity effect on the surrounding bundles,
It acts to increase the AC resistance of the surrounding bundled wires. Especially when the number of twists is large, it becomes a problem. Fig. 5 shows the AC resistance when the number of twisted litz wires is changed. When the number of twists exceeds 600, the AC resistance suddenly rises at 6 KHz or higher. This is mainly due to the influence of the central bundle line.

Therefore, in order to prevent the variation of the AC resistance between the bundle lines due to the center bundle line and to exert the parallelizing effect by the bundle lines, there is a conventional litz wire having a structure shown in FIG. Here, reference numerals 4 and 5 are the same parts as those of FIG. 4B, and 6 is an insulating core. With the litz wire with the structure shown in Fig. 6, it is possible to prevent an increase in the AC resistance of the central bundle part, but since the insulating core is present, the conductor cross-sectional area in the cross-sectional area of the litz wire is larger than that in Fig. 4 (b). However, there was a problem that the transformer and choke became large. Furthermore, the price of the insulating core is high, the price of the litz wire rises, and the flexibility of the insulating core is poor, making it difficult to form a winding wire. Further, in the conventional litz wire, since the insulating thin wire having the same wire diameter is used up to the center bundle wire, there is a problem that the space factor is poor and the resistance at low frequency is large. There was also the problem of high processing costs.

In order to solve the above-mentioned problems, the present invention uses an insulating thin wire having a thicker wire diameter instead of the same wire diameter as the central wire bundle and surrounding wire bundles. ， The outer diameter of the central bundle located at the center is made thicker than the outer diameters of other bundles, and the central bundle at high frequency causes an inadvertent increase of AC resistance due to the proximity effect to the surrounding bundles. The purpose is to provide a litz wire that suppresses the loss and reduces the loss in the transformer and choke windings while not sacrificing the price and flexibility of the litz wire.

[0010]

According to the present invention, the central bundled wire of the litz wire may be replaced by a thin insulated wire having a large diameter instead of the conventional insulated thin wire having the same diameter. The outer diameter is thicker than the outer diameters of other bundles.

[0011]

According to the present invention, by increasing the diameter of the central bundle wire, the influence of the proximity effect is reduced and the AC resistance at high frequencies is reduced as compared with the conventional Litz wire having the same wire diameter and the same number of wires (same cross-sectional area). In addition, since the space factor can be improved and the AC resistance at low frequencies can be reduced, the loss in the transformer and choke windings can be reduced, the winding temperature rise can be prevented, and the transformer and choke can be made smaller. Further, in the above configuration, even if the outer diameter of the central bundle line is made larger than the outer diameters of the other bundle lines, the same effect can be obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a first embodiment of the present invention. Here, reference numerals 1 to 5 are the same parts as in FIG. 4, and reference numeral 7 is a central bundled wire having a diameter larger than that of the insulating thin wire used in the surrounding bundled wires. FIG. 2 shows the AC resistance of the litz wire of the present invention. In the figure, the AC resistance is shown when the center bundle is a 0.7 mmφ single wire and a 1.2 mmφ single wire.
If the central bundle is thickened, the AC resistance will rapidly increase from a low frequency due to the proximity effect and the skin effect. Therefore, compared with the conventional litz wire, the litz wire of the present invention makes it difficult for a high-frequency current to flow from a low frequency to the central bundle wire (here, a single wire), and therefore the surrounding bundle wire due to the proximity effect due to the current flowing through the central bundle wire. It is possible to suppress the increase of the AC resistance of. Therefore, as shown in the figure, the high frequency resistance of the litz wire of the present invention is about 5% at 50 KHz, and the AC resistance is lower than the conventional one. Further, at low frequencies, the litz wire of the present invention has a higher space factor as compared with the conventional litz wire, so that the resistance is about 9% smaller. Note that the description has been given with the case where the central bundle line is a single wire, but the same effect can be obtained even when the central bundle line has a wire diameter different from that of the surrounding bundle wire.

FIG. 3 shows another embodiment of the present invention. Here, reference numerals 1 to 6 are the same parts as those in FIG. 4, and reference numeral 8 is a center bundle line in which the outer diameter dimension of the center bundle line is thicker than other bundle lines. Similar effects can be obtained in the present invention. In addition, although the explanation was given using the litz wire having the parent bundle line, the center child bundle line and the central grandchild bundle line are the same as those of the present invention even in the litz wire having the child bundle line and the grandchild bundle line. This has the same effect.

[0014]

Since the present invention has the above-described structure, the AC resistance is reduced by using the litz wire of the present invention as a wiring material of a high frequency power source (converter, inverter, etc.) and a winding material of a transformer or a choke. The advantage is that the loss can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a litz wire according to a first embodiment of the present invention and a view for explaining its configuration.

FIG. 2 is a comparison diagram of AC resistance with respect to frequencies of the present invention and a conventional litz wire.

FIG. 3 is a sectional view of a litz wire according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional wire rod, (a) is a single wire, and (b) is a litz wire.

FIG. 5 is a comparison diagram of AC resistances with respect to frequencies of each bundle of the litz wire of the present invention and the conventional litz wire.

FIG. 6 is a sectional view of a conventional litz wire.

[Explanation of symbols]

1 Metal conductor 2 Insulation skin 3 Insulation thin wires 4 Multiple insulation thin wires 5 Insulating fibers such as Teflon 7 Central bundle wire 8 whose diameter is larger than that of other bundles A center bundle with a larger conductor outer diameter than other bundles

Claims (2)

[Claims] 1. A conductor diameter of an insulating thin wire used for the other central bundle in a litz wire formed by twisting a plurality of bundles made of a plurality of insulating thin wires, the conductor diameter of the insulating thin wire being used for the central bundle located at the center. Litz wire characterized by being thicker than 2. The litz wire according to claim 1, wherein the outer diameter of the central bundled wire located at the center is larger than the outer diameters of the other bundled wires.