JPH0137815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a three-phase coaxial cable that is easy to manufacture and easy to perform terminal processing.

In recent years, as shown in Figure 1, an excellent cable with low voltage drop has been developed in which the conductors 1, 2, and 3 constituting each phase of a three-phase three-wire system are coaxial with each other, and insulation 4,
A three-phase coaxial cable consisting of 5 and 6 wires has been proposed and put into practical use.

However, this three-phase coaxial cable has disadvantages in that it requires many manufacturing steps and is low in productivity, and that it is difficult to process the terminals.

That is, the manufacturing of this cable consists of a step of twisting the intermediate layer conductor 2 around the outer periphery of the inner layer insulator 4, a step of covering the outer periphery of the intermediate layer conductor 2 with the intermediate layer insulator 5, and then a step of covering the outer periphery of the intermediate layer conductor 2. A large number of manufacturing steps are required, such as the step of twisting the outer layer conductor 3 around the outer periphery of the outer layer conductor 3, and the step of covering the outer periphery of the outer layer conductor 3 with the outer layer insulator 6, and these manufacturing steps are performed sequentially each time. It has to be carried out and the productivity is very poor.

On the other hand, since the wires constituting the intermediate layer conductor 2 and the outer layer conductor 3 are bare conductors, the terminal processing of this cable results in a complicated shape of the interface between the intermediate layer insulator 5 and the outer layer insulator 6. Therefore, insulation treatment such as tape wrapping is difficult and requires a long time.

In view of the above-described problems specific to three-phase coaxial cables, the main object of the present invention is to provide a three-phase coaxial cable of this type that is easy to manufacture and easy to terminate.

That is, in the three-phase coaxial cable of the present invention, the inner layer constituting the first phase of the conductors constituting each phase of the three-phase three-wire system is composed of an insulated conductor in which the conductor is coated with an insulator, and The intermediate layer constituting the third phase is constructed by twisting a plurality of insulated conductors, each of which is a single conductor coated with an insulator, around the outer circumference of the inner layer, and the outer layer constituting the third phase is a single conductor coated with an insulator. The invention is characterized in that a plurality of insulated conductors coated with are twisted together around the outer periphery of the intermediate layer.

An embodiment of the present invention will be explained below with reference to FIG. 2.

It is an inner layer that constitutes the first phase of each phase of the 9 three-phase three-wire system in the figure, and an intermediate layer 12 that constitutes the second phase is provided on its outer periphery, and a third phase is further provided on its outer periphery. A constituting outer layer 15 is provided, and these first to third phases are arranged coaxially with each other. 16 is a sheath provided at the outermost periphery.

The inner layer 9 is an insulated conductor formed by extruding and covering the outer periphery of the conductor 7, such as a single wire or a stranded wire, with an insulator 8.

The intermediate layer 12 has a plurality of insulated conductors formed by extruding and covering the outer periphery of a single conductor 10 such as a single wire or a stranded wire with an insulator 11, which are twisted around the outer periphery of the insulator 8 of the inner layer 9. It was established as follows.

Similarly to the intermediate layer 12, the outer layer 15 also includes an insulator 1 around the outer periphery of a single conductor 13 such as a single wire or a stranded wire.
A plurality of insulated conductors formed by extrusion coating 4 are twisted around the outer periphery of the insulator 11 of the intermediate layer 12.

In the cable of the present invention constructed in this manner, each phase constituting the three-phase three-wire system is arranged coaxially with each other, such as the inner layer, intermediate layer, and outer layer, so that the inductance can be reduced and the voltage This cable maintains the unique advantage of the so-called three-phase coaxial cable, which is that the cable drop can be minimized as much as possible.

In addition, among the conductors that constitute each phase and are arranged coaxially with each other, the intermediate layer and outer layer, which are particularly susceptible to external mechanical, chemical, and thermal influences, are Because each conductor is electrically isolated by a double insulator, it can be put to practical use as a safer cable than the conventional three-phase coaxial cable with bare conductors. It is.

In particular, this type of three-phase coaxial cable is often used under high heat and harsh environments, such as with welding machines, and in this case, the high heat from the welding machine is continuously applied to the cable. When deterioration occurs in the insulation of the intermediate layer and part of the outer layer placed on the outside, electrical insulation from the conductor of a different phase arranged coaxially becomes a problem in the conventional three-phase coaxial cable using bare conductors. However, in the same phase, even if one conductor is corroded, all the remaining conductors that come into contact with it may be corroded one after another.

In contrast, in the three-phase coaxial cable of the present invention, even if some of the insulators in the intermediate and outer layers deteriorate, most of the remaining insulated conductors, which are individually isolated by the insulators, are in good condition. This prevents deterioration of electrical insulation between adjacent different phases in a coaxial arrangement, and even if the insulation of one insulated conductor deteriorates and is corroded by an external corrosive environment within the same phase, the electrical insulation will not deteriorate. It is possible to reliably prevent migration corrosion to most of the conductors, and it is possible to continue using the insulated conductors even if a defect occurs in some of the insulated conductors. The same thing can be said in the case of partial damage to the outer part due to severe use.

Further, according to the three-phase coaxial cable of the present invention, flexibility, which is required as a cable's original function, is also sufficiently improved.

That is, in the case of a conventional three-phase coaxial cable, the insulators between adjacent conductors constituting each phase of a three-phase three-wire system are provided coaxially and annularly with each other, similar to the coaxial arrangement of the conductors. By enclosing these insulators in an annular shape, the rigidity is increased, and as a result, it is not possible to bring out the necessary and sufficient performance for the flexibility of the cable.

In contrast, in the present invention, insulators are individually applied to each of the conductors constituting each phase of a three-phase three-wire system, and also to each of the plurality of conductors in the same phase in the intermediate layer and outer layer where the diameter becomes large. Because of this, the insulators are coaxially arranged for each phase conductor, which provides the necessary and sufficient flexibility as a small bending stiffness for each insulated conductor, and the cable This makes handling even easier.

Furthermore, according to the three-phase coaxial cable of the present invention,
Conventional methods of using bare conductors include forming an intermediate layer by twisting multiple insulated conductors around the outer periphery of the innermost inner layer, and forming an outer layer by twisting multiple insulated conductors around the outer periphery of the intermediate layer. It can be manufactured in a manufacturing process that is approximately half that of a three-phase coaxial cable with bulk insulation between layers, and the multiple insulated conductors that make up the intermediate and outer layers can be manufactured in large quantities in advance. In order to be able to use the general-purpose wires, the production of the multiple insulated conductors for the intermediate layer and the outer layer is stopped, and the stocked general-purpose insulated conductors are sequentially supplied as needed to the inner layer. The intermediate layer and the outer layer around the outer layer can be constructed, and by twisting together multiple highly flexible general-purpose insulated conductors in the intermediate layer and outer layer, which have a larger diameter, the twisting work becomes extremely easy. This method solves all the difficulties in conventional manufacturing of this type of three-phase coaxial cable and greatly improves productivity.

Furthermore, in terminal processing, each phase is constructed with adjacent insulators, and multiple insulated conductors are individually insulated within the same layer, so multiple insulated conductors are connected one by one for each phase. Due to the sufficient flexibility of the insulated conductor, it can be easily brought together and terminated, and the insulation at the terminal portion can also be easily performed.

Furthermore, in the case of this coaxial cable, since the impedance is lower as the outer conductor approaches, it is easy to create a well-balanced low impedance structure by reducing the core cross-sectional area as the outer conductor approaches. By doing so, it is possible to bring out the economic effects of resource conservation.

As explained above, according to the three-phase coaxial cable of the present invention, the difficulty in manufacturing and the difficulty in terminal processing, which are one of the obstacles to generalization in this type of cable, can be solved all at once, and the three-phase coaxial cable The low impedance effect of the axial structure is superior to other low impedance cables with a non-coaxial structure. It has sufficiently improved the flexibility required as a function of the insulator, which tends to deteriorate, and is safe by guaranteeing low impedance characteristics as a three-phase coaxial type even if a part of the insulator deteriorates. The present invention has greatly contributed to the further utilization of this type of three-phase coaxial cable, and its industrial value is immense.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram showing an example of the structure of a conventional three-phase coaxial cable, and FIG. 2 is a cross-sectional explanatory diagram showing an embodiment of the three-phase coaxial cable of the present invention. 1, 2, 3, 7, 10, 13: conductor, 4, 5,
6, 8, 11, 14, 16: insulator, 9: inner layer,
12: middle layer, 15: outer layer.

Claims (1)

[Claims] 1. In a coaxial cable in which conductors constituting each phase of a three-phase three-wire system are arranged coaxially with each other, the inner layer constituting the first phase is composed of an insulated conductor in which the conductor is coated with an insulator. , the intermediate layer constituting the second phase is constructed by twisting a plurality of insulated conductors, each of which is a single conductor coated with an insulator, around the outer periphery of the inner layer, and the outer layer constituting the third phase is composed of a single conductor coated with an insulator. A three-phase coaxial cable characterized in that it is constructed by twisting a plurality of insulated conductors, each of which is a conductor coated with an insulator, around the outer periphery of the intermediate layer.