JPS5914845B2 - Method for forming wire insulation coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a so-called strand insulation coating, in which an oxide film is formed on the surface of strands constituting a power cable conductor.

(2) As power transmission capacity increases in recent years, power cable conductors have become larger in size.

As a result, the effects of skin effect and proximity effect cannot be ignored during power cable operation, and to solve this problem, it is necessary to form a wire insulation coating on the wires that make up the power cable conductor.
is being carried out. The present invention provides a method for efficiently forming the wire insulation coating.

Various methods have been used to date to form an insulating coating on a strand, particularly by heating.5 A method for forming an insulating coating on a strand is to heat the strand with a burner in an oxidizing atmosphere. The current state of affairs is the extent to which the method is being implemented.

However, when heating with a burner, it is difficult to uniformly heat the entire circumferential surface of the wire, and as a result, the wire insulation coating does not have a uniform thickness, and the inside of the wire is also heated. However, there were drawbacks such as it took a relatively long time to cool the system and a large-scale cooling device was required. The present invention has been made to overcome the above-mentioned drawbacks.

That is, the method uses a normal induction heating method as a heating device, uniformly heats only the surface of the wire to form a uniform oxide film on the surface of the wire, and rapidly cools the wire. The method of the present invention will be explained with reference to the drawings.
A single copper wire 1 fed out from the feeding mechanism is heated by induction in a container 3 containing an oxidizing atmosphere 2 (for example, oxygen gas, ozone, carbon dioxide gas, a mixed solution of sodium chlorite and caustic soda). 5 along the central axis of the coil 4 (made of copper, for example), and during this time the surface of the copper strand 1 is oxidized by the heating of the induction heating coil 4.

In this case, if the oxidizing atmosphere is carbon dioxide gas, the container 3 is of a closed type and the atmosphere constantly contains carbon dioxide gas at a constant concentration.

In this case, since the induction heating coil 4 is placed inside the closed container 3, the thermal efficiency is particularly good, and an effect that cannot be obtained with other heat sources (for example, a normal heating method that heats the container from the outside) is achieved. Furthermore, if the oxidizing atmosphere is a liquid (a mixed solution of sodium chlorite and caustic soda), it goes without saying that the container 3 does not have to be of a closed type.

In the above case, the wire speed is 1m/s for the copper wire with a thickness of 2m1.
When the copper wire is induction heated in carbon dioxide gas at 3 oz, a 1 μm cupric oxide (CuO) film is formed on the surface of the copper wire.

(Copperous oxide is not preferred due to its chemical and mechanical stability and electrical resistance.) After the above steps are completed, the copper wire undergoes a simple cooling step or is directly wound onto a bobbin. If the surface of the coil (e.g. made of copper) used for induction heating is coated with a tube of non-magnetic material (e.g. tetrafluoroethylene resin, silicone rubber), the surface of the coil will remain oxidized even in an oxidizing atmosphere. Since di-copper (CuO) is not formed, the coil does not increase electrical resistance and generate heat, and induction heating is performed efficiently. In the examples of the present invention, a wire insulation coating was formed on a single copper wire, but it is not limited to single wire copper wires, and by lowering the frequency of induction heating (for example, 1K1Iz), multiple copper wires can be coated. Of course, it is also possible to use stranded wire conductors twisted together.

As described above, according to the present invention, only the surface of the wire is uniformly heated by induction heating in an oxidizing atmosphere, so the wire insulation coating is uniformly formed, and the wire is rapidly heated. Since the wire is cooled to 100%, a simple cooling device or no cooling device is required, and the wire insulation coating can be efficiently formed.Also, an oxidizing atmosphere is formed in the closed container, and the induction heating coil is heated in this atmosphere. If used, it can be used particularly efficiently as a heat source.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram when implementing the method of the present invention, in which:
1 is a wire, 2 is an oxidizing atmosphere, 3 is a container, and 4 is an induction heating coil.

Claims (1)

[Scope of Claims] 1. A wire is advanced approximately along the central axis of an induction heating coil placed in an oxidizing atmosphere, and an oxide film is formed on the surface of the wire by heating with the induction heating coil. A method for forming an insulating film on a wire, characterized by: 2. The method for forming an insulating film on wires according to claim 1, characterized in that an oxidizing atmosphere is formed in a closed container.