JPH05135626A - High voltage withstanding wire - Google Patents

Abstract

PURPOSE:To provide a high voltage withstanding wire capable of increasing withstand voltage compared with an outer diameter of a wire while being light in weight and inexpensive. CONSTITUTION:A high voltage withstanding wire is composed of a core wire 1, a mesh wire 7 encircling this wire core 1 and an inclined insulator interposed between the core wire 1 and a mesh wire 7, whose dielectric constant is gradually increased from the mesh wire 7 to the core wire 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure resistant wire capable of transmitting a higher voltage without increasing the outer diameter or the like.

[0002]

2. Description of the Related Art Conventionally, electric power and signals are transmitted using insulated wires, wires for general wiring such as cables, and cables for control and light equipment (hereinafter, simply referred to as wires). Especially when a high voltage power supply such as an X-ray device is required, a coaxial high voltage electric wire is usually used.

The structure of this conventional high-voltage electric wire will be described below with reference to the sectional shape shown in FIG. In FIG. 3, a core wire 101 having a substantially circular cross section at the center of the high-voltage electric wire.
Is surrounded by an insulator 105 having a uniform dielectric constant, the outside thereof is concentrically surrounded by a mesh wire 107, and the outside thereof is covered by a protective coating 109 made of an insulator.

A material having a high withstand voltage such as polyethylene is used for the insulator 105 to increase the withstand voltage between the core wire and the mesh wire. Further, the radius R ₁ of the outer circumference of the core wire is close to 1 / e (about 1 / 2.7) of the radius R ₂ of the inner side of the wire in order to maximize the withstand voltage with respect to the outer diameter of the wire. Is set to. That is, the ratio of the diameters is such that when the core wire is thin, the electric field on the surface of the core wire becomes strong, and discharge tends to occur outward from here, and when the core wire is thick, the insulation distance between the core wire and Since it becomes shorter and the withstand voltage decreases, it is required as an optimum value that can maximize the withstand voltage.

[0005]

DISCLOSURE OF THE INVENTION As described above,
With conventional electric wires, the withstand voltage is determined by the outer diameter and the material of the insulator, and in order to increase the withstand voltage, the outer diameter is increased.
Further, since the core wire is relatively thicker than the outer diameter, the weight of the electric wire itself is heavy and expensive. Further, for that reason, there are problems to be solved such as deterioration of flexibility.

The present invention has been made in view of the above problems, and makes it possible to increase the withstand voltage as compared with the outer diameter of the electric wire, that is, by making the outer diameter of the core wire small, the electric wire can be made flexible. Moreover, it is intended to be lightweight and inexpensive.

[0007]

SUMMARY OF THE INVENTION The present invention is provided between an inner conductor, an outer conductor surrounding the inner conductor, the inner conductor and the outer conductor, and having a dielectric constant of the outer conductor. The gist of the present invention is to have an insulator formed so as to be sequentially higher from the body toward the inner conductor.

[0008]

In the withstand voltage wire of the present invention, an insulator is formed between the inner conductor and the outer conductor so that the dielectric constant is gradually increased from the outer conductor to the inner conductor. , The electric field intensity peak on the inner conductor surface is relaxed.

[0009]

Embodiments will be described below with reference to the drawings. FIG. 1 shows a cross section of a pressure resistant electric wire according to an embodiment of the present invention.

A core wire 1 as an inner conductor having a substantially circular cross section at the center of a pressure resistant wire is composed of a single wire or a stranded wire of copper, aluminum or an alloy thereof, and the periphery thereof is closer to the core wire 1 and is dielectric. It is surrounded, that is, surrounded by a graded insulator 3 that uses a so-called functionally graded material, which has a higher rate.

The functionally graded material used in the graded insulator 3 is a combination of materials having different functions, which are integrated by continuously or stepwise changing the composition ratio of the materials. In terms of internal characteristics, styrene-butadiene rubber with a high dielectric constant (relative dielectric constant 3.0-7.0)
Alternatively, a mixture of nylon (5.0 to 14.0) with a high mixing ratio and polyethylene with a low dielectric constant on the outside (2.2 to 14.0)
The mixing ratio of the inclined insulator 3 changes gradually from the inside to the outside so that the mixing ratio of 2.4) and the like increases, and in this embodiment, the dielectric constant changes in proportion to approximately 1 / r. It is done like this. Further, this inclined insulator 3 portion is mainly formed by a thermal spraying method. That is, a plurality of raw material powders are sequentially laminated while changing the mixing ratio thereof appropriately by using a plasma jet in a decompression chamber where the atmosphere is controlled. Therefore, the composition ratio of the graded insulator 3 changes continuously.

Next, the periphery of this inclined insulator 3 is covered with an insulator 5 having a uniform dielectric constant. In this insulator 5,
A material having a high withstand voltage such as polyethylene is used to increase the withstand voltage between the core wire 1 and a mesh wire 7 described later.

The outer side is surrounded by a mesh wire 7 as an outer conductor, which is formed by knitting a number of concentric copper wires in a knitted shape, and the outer side is further covered with polyvinyl chloride (PVC), chloroprene rubber (CR), etc. It is covered with a protective coating 9 made of an insulating material. Next, the operation of this embodiment will be described with reference to FIG.

First, the electric field strength E in a general insulator
When the electric field strength E at a point at a distance r from the central axis set in this insulator is E = q / 2πεr (1) when the permittivity of the insulator at that point is ε ₀ ) Is represented by. Here, q is an electric charge charged per unit length of the electric wire (in FIG. 1, + q is charged on the surface of the core wire 1 and −q is charged on the inner surface of the mesh wire 7).

Therefore, in the case of the conventional wire shown in FIG. 3 which is covered only by the insulator 105 having a uniform dielectric constant, the electric field strength E is as shown by the one-dot chain line in FIG. 2 because the dielectric constant ε ₀ is constant. Is inversely proportional to the distance r. Therefore, the electric field strength E has a peak P on the surface of the core wire 101.

On the other hand, in the case of the withstand voltage wire of this embodiment, the electric field strength E has a shape such that the peak P generated in the conventional wire is removed as shown by the solid line in FIG. That is,
Since the electric field strength E ₀ is constant in the region where the radial distance r is r ₂ to r ₃ , the electric field strength E is inversely proportional to the radial distance r as in the conventional electric wire. Further, the radial distance r is r ₁ to r ₂
In the region of, since the dielectric constant ε ₀ is inversely proportional to the radial distance r, the electric field intensity E becomes constant and no peak occurs.

As described above, according to this embodiment, the core wire 1
The peak of the electric field strength E on the surface is relaxed, and the maximum electric field strength can be suppressed low. For this reason, insulation damage due to discharge is less likely to occur, and the withstand voltage of the wire can be increased. Further, at this time (state in which the electric charge q is charged)
The voltage V between the core wire 1 and the mesh wire 7 is

[0018]

[Equation 1] It is also calculated by the formula (2) of the above, but this is also the area of the part surrounded by the r-axis and the solid line (the one-dot chain line in the case of the conventional example) in the figure. Shown for).
As can be seen from FIG. 2, in this embodiment, the maximum electric field strength is suppressed to a low level, that is, the withstand voltage of the wire is increased, although the area is larger and a higher voltage is applied than in the conventional example.

As described above, when the size of the outer diameter is fixed, the withstand voltage of the electric wire can be further increased, and at the same time, the outer diameter of the core wire can be reduced. It can be lightweight and inexpensive.

The present invention does not particularly limit the materials constituting the graded insulator 3, the mixing ratio, and the manufacturing method.
Further, it may be integrated with the insulator 5 surrounding the inclined insulator 3 (in this case, two kinds of materials having greatly different dielectric constants are required). Further, in the inclined insulator 3 portion, unlike the present embodiment, even if the dielectric constant is not continuously changed, a thin film, a sheet, or a tape made of an insulating material having a different dielectric constant is closer to the core wire 1 in the dielectric constant. In order to obtain a high dielectric constant, the core wire 1 may be sequentially wound and covered to form a multilayer structure in which the dielectric constant is changed stepwise.

[0021]

As described above, according to the pressure resistant wire of the present invention, the withstand voltage can be made higher than the outer diameter of the wire and the outer diameter of the core wire is small. This has the effect of making the electric wire flexible and lightweight.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a pressure resistant wire according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the action of the pressure-resistant wire shown in FIG.

FIG. 3 is a cross-sectional view showing a configuration of a conventional electric wire.

[Explanation of symbols]

 1 core wire 3 inclined insulator 5 insulator 7 mesh wire 9 protective coating

Claims (1)

[Claims] 1. An inner conductor, an outer conductor surrounding the inner conductor, and a dielectric constant provided between the inner conductor and the outer conductor, the permittivity being directed from the outer conductor to the inner conductor. A pressure-resistant wire, comprising: an insulator formed so as to be sequentially higher.