JP4620475B2 - power cable - Google Patents

Description

  The present invention relates to an electric wire applied to a high-voltage power cable, various cables for various devices, a power cord, a signal transmission cord, and the like.

  In general, an insulated wire used for, for example, a high-voltage power cable is configured by covering a conductor made of annealed copper wire or the like with a tubular insulator such as polyethylene without a gap.

  By the way, in the cable, it is desirable that the allowable current is as large as possible, but this allowable current is defined by the temperature rise due to the heat generated during energization.

  In addition to the resistance loss that occurs inside the conductor when energized, there is a dielectric loss that occurs particularly in the insulator as a cause of the temperature rise of the cable. This is inevitable as long as a dielectric material such as polyethylene, butyl rubber, paper, or the like is used as a constituent material of the insulator.

  The dielectric loss is proportional to the capacitance and depends on the specific dielectric constant of the substance. Polyethylene, which is a constituent material of the insulator, has a relatively low relative dielectric constant of 2.3 and is widely used as various insulating materials, but still has a relative dielectric constant of air, which is a substance having the smallest dielectric loss. The value is larger than 1.0. That is, an electric wire using an insulator made of polyethylene has a dielectric loss 2.3 times that of a bare electric wire without an insulator.

  In order to bring the dielectric loss of an electric wire covered with an insulator closer to the dielectric loss of a bare electric wire, in the high voltage field, a single conductor has been placed in a metal tube made of a rigid copper tube. In order to increase the withstand voltage, a so-called air cable is known in which sulfur hexafluoride having a relative dielectric constant of 1 is enclosed in the metal tube.

Conventionally, as a high-voltage electric wire for automobiles, a magnetic core is arranged on a shaft core in a tubular insulator, and a conductive wire is spirally wound around the magnetic core to support the conductive wire and a hollow insulator. A configuration in which a gas is interposed between the two is disclosed (for example, Patent Document 1).
Japanese Patent Laid-Open No. 2-215015 (2nd page)

  However, the conventional high voltage cable encapsulating sulfur hexafluoride has a dielectric loss as small as air and can suppress heat generation during energization, but the metal tube encapsulating sulfur hexafluoride is Since it is a rigid body, there is no flexibility and its use is limited.

  In addition, since the conventional cable structure remains linear, there is a problem that even if it is applied to a power cord, for example, there is no coil effect and inductance is not expected, so it is difficult to absorb harmonic components such as noise. is there.

  Note that the technique of the above-mentioned patent publication also has the same drawbacks as the prior art, such that the conducting wire is wound around the magnetic core, the structure becomes complicated, and the flexibility cannot be obtained.

It is an object of the present invention to provide a power cable having a simple structure and having a low dielectric loss, a high allowable current, and excellent flexibility and noise absorption.

The above problem is solved by the following means.

[1] A conductor and a tubular insulator for covering the conductor,
The conductor is locally in contact with the inner peripheral surface of the insulator to form a non-linear shape as a whole, and a space between the conductor and the inner peripheral surface of the insulator except for the local contact portion. Exist,
The insulator is made of polyethylene resin,
The two wire main bodies covering the conductor with the insulator are twisted together in a spiral shape,
A linear ground wire is disposed at a central portion in the radial direction of the two electric wire main bodies,
The power cable according to claim 2, wherein the two electric wire main bodies are arranged on opposite sides of the ground wire.

[2] The power cable according to item 1 above, wherein the conductor is formed in a wave shape.

[3] A tubular second insulator is disposed between each of the two wire main bodies in the circumferential direction, and the two wire main bodies and the two second insulators are collectively connected to the ground. It is twisted in a spiral around the line,
3. The power cable according to claim 1 or 2, wherein the second insulator is formed of the same material and shape as the wire-based insulator and is hollow.

According to the invention of [1], the conductor covered with the insulator is formed in a non-linear shape, and only a part of the conductor is in contact with the inner peripheral surface of the insulator, and the remaining portion and the insulator Since there is a space between the inner peripheral surface of the cable and an air power supply cable with almost no conductor loss, the air is sealed and the relative dielectric constant is close to 1, and the dielectric loss is low. Composed.

  For this reason, there is little generation | occurrence | production of the heat | fever in the conductor at the time of electricity supply, As a result, a temperature rise is suppressed and an allowable electric current can be enlarged.

In particular, as the aerial cable, unlike those encapsulating sulfur hexafluoride in conventional metal tube body, by adopting a polyethylene emissions resins as an insulator, it can have flexibility as a whole the power cable, Applications are expanded.

  Also, there is an advantage that the structure is simpler than that using a magnetic core or the like.

In addition, since the two wire main bodies are twisted in a spiral shape, the inductance is increased by the coil effect, and harmonic components such as noise can be reduced.

In addition, since the straight ground wire is arranged at the center portion in the radial direction of the two wire main bodies, an appropriate grounding function is exhibited and the ground wire is tightened to the plurality of wire main bodies. It is firmly held and can resist external force in the pulling direction, so that construction and the like are facilitated.

According to the invention of [ 2 ], a space can be easily present between the conductor and the insulator by simply forming the conductor in a wave shape.

According to the invention of the preceding item [3], the second insulator is formed of the same material and in the same shape as the insulator, and is hollow, so that the second insulator is contained as a conductor as necessary and used as a main body of the electric wire. It is also possible to configure. In addition to providing the grounding function effectively by providing the grounding wire at the center of the two wire main bodies and the two second insulators, the grounding wire is tightened and pulled by the wire main body. It is stably held without being influenced by the external force of stress.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 are an external perspective view and a cross-sectional view showing a power cable to which an electric wire according to an embodiment of the present invention is applied, respectively.

  The power cable includes a plurality of (for example, two) wire main bodies 1, 1, a plurality of (for example, two) insulators 2, 2, and a single ground wire 3.

  As shown in FIG. 3, each electric wire main body 1 includes a conductor 11 and a tubular insulator 12 that covers the conductor 11. As shown in FIG. 2, the two wire main bodies 1, 1 are arranged on opposite sides of the ground wire 3.

  The conductor 11 is a single wire having a diameter of about 1.0 mm, and is made of, for example, a JIS C3102 soft conductor. Of course, the conducting wire 11 may be a stranded wire.

  The insulator 12 is made of, for example, polyethylene resin, and is formed into a tube shape having a thickness of 1.40 mm and an outer diameter of 6.50 mm, and covers the conductor 11.

  As shown in FIG. 3, the conductor 11 is formed in a non-linear shape, for example, a wave shape, which comes into local contact with the inner peripheral surface of the insulator 12, except for the local contact portion 11 a. A space P exists between the inner peripheral surface of the insulator 12. Of course, the non-linear shape of the conductor 11 is not limited to a wave shape.

  The insulator 2 is made of the same material as the insulator 12 and is formed in the same shape. Here, the insulator 2 remains hollow, but may be configured as a main body of an electric wire with a conductor as necessary. Is possible. That is, by placing the conductor 11 in one insulator 2, a three-core cable is formed by the wire main bodies 1, 1, and by inserting the conductor 11 in both insulators 2, 2, The cable is configured. Of course, the number of cores can be increased or decreased as appropriate. As shown in FIG. 2, the insulator 2 is disposed between the two wire main bodies 1 and 1 in the circumferential direction.

  The ground wire 3 is formed in a straight line, and is disposed in a central portion surrounded by the two electric wire main bodies 1, 1 and the two insulators 2, 2.

  The ground wire 3 is composed of a conductor 31 made up of seven single wires and having an outer diameter of 2.4 mm stranded wire, and an insulator 32 covering the outside of the conductor 31.

  One single wire in the conductor 31 is made of, for example, a JIS C3102 soft conductor of 0.8 mm. The conductor 31 is not limited to a stranded wire, but may be a single wire.

  The insulator 32 is made of, for example, polyethylene resin, is formed into a tube shape having a thickness of 0.30 mm and an outer diameter of 3.00 mm, and covers the conductor 31.

  The two electric wire main bodies 1 and 1 and the two insulators 2 and 2 are twisted together spirally around the ground wire 3.

  In this case, the twisting pitch is, for example, 160 to 170 mm, and the outer diameter is 15.70 mm.

  In the electric wire thus configured, the insulator 12 is made of polyethylene, has a relative dielectric constant of 2.3, and does not reach the relative dielectric constant of 1.0.

  However, the conductor 11 covered with the insulator 12 is formed in a wave shape, and only a part 11a thereof is in contact with the inner peripheral surface of the insulator 12, and the remaining portion and the inner peripheral surface of the insulator 12 are contacted. Since there is a space P between them, the air-filled state is obtained in almost all parts, the relative permittivity is close to 1, and the air cable is configured with little dielectric loss.

  For this reason, generation | occurrence | production of the heat | fever in the conductor 11 at the time of electricity supply is suppressed, As a result, a temperature rise is suppressed and an allowable electric current can be enlarged. As a result, the conductor 11 having a relatively small diameter can be used for a large current.

  In particular, as an aerial cable, the insulator 12 is made of a synthetic resin such as polyethylene, unlike a conventional metal tube in which sulfur hexafluoride is sealed, so that the cable should be flexible. Can be used for a wide range of applications

  In addition, there is an advantage that the structure can be made simpler than that in which a conducting wire is wound around a magnetic core.

  Such a power cable can be applied to, for example, a power cord of an audio device using the two electric wire main bodies 1 and 1. In that case, since the two wire main bodies 1 and 1 are twisted together with the two insulators 2 and 2 in a spiral manner around the ground wire 3, the coil effect increases the inductance, noise and the like. As a result, an improvement in frequency characteristics of the acoustic device can be expected.

  The power cable having the above configuration can be used with only two wire main bodies 1 and 1, but is located at the center between the two wire main bodies 1 and 1 and the two insulators 2 and 2. In addition to the grounding function being effectively exhibited, the grounding wire is fastened to the wire main bodies 1 and 1 and is stably held without being influenced by the external force in the pulling direction.

  By the way, although the three of the two electric wire main bodies 1, 1, 2 insulators 2, 2 and the ground wire 3 were used as they were as the electric wires, as shown in FIG. The insulators 2 and 2 and the ground wire 3 may be covered with the sheath 5 via the shield body 4.

  The shield body 4 has an outer diameter of, for example, 16.51 mm, a thickness of 24 mm, and is formed by assembling seven 0.14 mm single wires and twisting them into a cylindrical shape with a pitch of 20 mm.

  The sheath 5 is made of PVC, for example, and is formed in a cylindrical shape with a thickness of 1.00 mm and an outer diameter of 18.50 mm. The finished outer diameter including the shield body 4 and the sheath 5 is, for example, 18 .5 ± 0.50 mm.

  In this case, the sheath 5 and the shield body 4 increase the strength and exert an effect of blocking an external magnetic field.

FIG. 5 shows a reference embodiment of the present invention.

In this reference form, the conductor 11 is not formed into a wave shape to form an air cable, but as shown in FIG. 5, a plurality of wire main bodies 10 and 10 having straight ordinary conductors 111 are used, The ground wire 3 is provided at the center, and the wire main bodies 10 and 10 are spirally twisted around the ground wire 3.

  In the electric wire having the above configuration, the electric wire main bodies 10 and 10 are spirally twisted together by the ground wire 3 in the same manner as in the above embodiment, so that the coil effect is exhibited and the inductance increases as the frequency increases. Can contribute to the reduction of harmonic components such as noise.

  Further, in this case as well, since the ground wire 3 is tightened by the twisted electric wires 10 and 10, a stable state that is hardly affected by the external force in the pulling direction is maintained.

Of course, even in this reference embodiment, as shown in FIG. 6, the wire main bodies 10, 10, the insulators 2, 2 and the ground wire 3 are covered with a sheath 5 through a shield body 4. May be.

It is an external appearance perspective view which shows the power cable with which the electric wire concerning embodiment of this invention was applied. It is a cross-sectional view which similarly shows a power cable. It is a longitudinal section showing one electric wire subject in a power cable similarly. It is a transverse cross section showing a power cable provided with a sheath. It is a cross-sectional view which shows the power cable with which the electric wire concerning the reference form of this invention was applied. In a reference form, it is a transverse cross section showing a power cable provided with a sheath.

1 (10) ··· Wire main body 12 ······· Insulator 3 ······· Ground wire 11 (111) ··· Conductor 11a ···・ ・ ・ ・ ・ Local contact site P ・ ・ ・ ・ ・ Air

Claims (3)

A conductor and a tubular insulator for covering the conductor;
The conductor is locally in contact with the inner peripheral surface of the insulator to form a non-linear shape as a whole, and a space is formed between the conductor and the inner peripheral surface of the insulator except for the local contact portion. Ri Oh in the presence of a,
The insulator is made of polyethylene resin,
The two wire main bodies covering the conductor with the insulator are twisted together in a spiral;
A linear ground wire is arranged at a central portion in the radial direction of the two electric wire main bodies,
The power cable according to claim 2, wherein the two electric wire main bodies are arranged on opposite sides of the ground wire . The power cable according to claim 1, wherein the conductor is formed in a wave shape. A tubular second insulator is disposed between each of the two wire main bodies in the circumferential direction, and the two wire main bodies and the two second insulators are collectively centered on the ground wire. Are twisted together in a spiral,
3. The power cable according to claim 1, wherein the second insulator is formed of the same material and in the same shape as the wire-based insulator and is hollow.

Images