Metallic wire

In a metallic wire for producing transformer windings, first segments (4a, 4b), in which the long axis of the cross section extends in a defined plane, alternate with second segments (4c), in which the long axis of the cross section extends perpendicular thereto.

BACKGROUND OF THE INVENTION

The invention relates to a metallic wire and to a winding for transformers.

In windings for oil-cooled transformers, paper-insulated wires or transposed conductors having a constant thickness/width ratio over their entire length are used. The wires are wound onto a magnetizable metal core.

Such an arrangement of the metal wires does not take into account the different field strengths in the center and at the ends.

As a consequence, the losses in the transformer are increased and the efficiency is reduced.

SUMMARY OF THE INVENTION

An object of the present invention is thus to provide a metal wire for transformer windings that obviates the described drawbacks, or to provide a winding that makes it possible to reduce the stray-field losses in a transformer and to improve the transformer's efficiency.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a winding, e.g., for a transformer, which comprises an iron core 1 and a cylinder 2 , e.g., made of paperboard or insulating board, which is arranged over the iron core. Iron core 1 and cylinder 2 are located in the interior of a wire winding 3 . The wire winding 3 consists of a length of copper profile with a rectangular cross section. According to the teaching of the invention, this copper profile is wound such that in the center area 3 a of winding 3 the long axis of the copper profile extends parallel to the center axis A of the winding. In contrast, in the end areas 3 b of winding 3 , the long axis of the copper profile extends perpendicular to the center axis A of winding 3 . Between the areas 3 a and 3 b , i.e., at 3 c , the copper profile 3 has a nearly square cross section.

By changing the cross section of the copper profile over the course of winding 3 , the stray-field losses can be reduced and the efficiency of a transformer equipped with an inventive winding 3 can be increased.

The copper profile can be a solid flat copper wire. It is also possible, however, to use a profile comprising a plurality of conductor elements arranged one on top of the other, e.g., a so-called transposed conductor, which can be produced by Roebel transposition of flat conductor elements.

An exemplary embodiment of a production process will now be described in greater detail with reference to FIG. 2 .

The upper half of FIG. 2 shows a side elevation of a metallic wire 4 according to the teaching of the invention. This wire comprises a total of five segments 4 a , 4 b , 4 c , 4 d and 4 e.

As shown in the section views, segments 4 a and 4 e have a flat profile with a long axis perpendicular to the horizontal, and segments 4 b and 4 d have a nearly square cross section. The center segment 4 c is rotated by 90 relative to segments 4 a and 4 e.

Such a metallic wire 4 can be produced, for instance, by metallurgical joining techniques, e.g., by welding or soldering the individual segments 4 a to 4 e . The junctions between the segments 4 a to 4 e must be correspondingly adapted to each other, i.e., the cross section of the metal wire 4 must have the same size across the entire length.

Another method for producing the metal wire 4 is to shape the individual segments 4 b , 4 c and 4 d by means of a sizing press or section rolling.

The lower half of FIG. 2 depicts the section rolling machines that are being used.

Section rolling machines 5 and 6 have two roll pairs each, 5 a and 5 b and 6 a and 6 b . The roll pairs 5 a and 5 b as well as 6 a and 6 b can advantageously be driven. They are furthermore adjustable in the direction of the roll nip.

The process sequence is as follows:

Segment 4 e passes freely through the section rolling machines 5 and 6 . When segment 4 d reaches the first section rolling machine 5 , the roll pairs 5 a and 5 b are adjusted such that a nearly square cross section results. Segment 4 d with the square cross section passes freely through the section rolling machine 6 .

Segment 4 e , like segment 4 d , is first shaped into a square cross section. When the shaped segment 4 c reaches the second section rolling machine 6 , the roll pairs 6 a and 6 b are adjusted as shown below and the square profile is shaped into a flat rectangular profile.

Segment 4 b is shaped into a square by the rolling machine 5 and passes freely through rolling machine 6 . Segment 4 a , like segment 4 e , is not being shaped and passes freely through the section rolling machines 5 and 6 in which the roll pairs 5 a and 5 b as well as 6 a and 6 b have been driven apart.

A metallic wire of great length can thus be produced. The wire segments required to produce the windings can then be cut from these wire lengths.