JPH05291056A - Sheet wound transformer - Google Patents

Abstract

PURPOSE:To enable a sheet wound transformer to be prevented from decreasing in dielectric strength due to gas gap and lessened in thermal resistance and the number of cooling ducts or panels by a method wherein a metal sheet used as conductor is formed of annealed material. CONSTITUTION:A conductor sheet 1 is formed of aluminum sheet of O material (annealed material), and an insulating sheet 2 is formed of two pieces of polyethylene terephthalate film. By this setup, sheet windings can be lessened in gas gap, so that sheet windings which are hardly lessened in dielectric strength due to gas gap defect can be obtained. A sheet winding transformer of this design is enhanced in cooling properties, so that it can be decreased in the number of cooling ducts or panels. Furthermore, if a short gap part is not in an electrical field higher than the minimum value of a Paschen curve, dielectric breakdown hardly occurs, so that the sheet winding transformer can be sharply enhanced in reliability without decreasing the insulating sheet 2 in dielectric strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet winding transformer for electric power having a sheet winding formed by stacking and winding a conductor sheet and an insulating sheet.

[0002]

2. Description of the Related Art A sheet-wound transformer formed by stacking a conductor sheet and an insulating sheet on top of each other is expected to be a transformer for future electric power because it is easy to manufacture a large-capacity transformer and is easy to automate. As a characteristic of the sheet winding, it is necessary to use an insulating sheet without pinholes in order to withstand the voltage between turns with the insulating sheet. An insulating sheet without pinholes is currently difficult to manufacture unless it has a thickness of about 25 μm or more. Therefore, in consideration of the possibility that pinholes exist, two insulating sheets having a thickness of 25 μm or more are stacked and used.

When this sheet winding is wound, the winding is liable to be deformed such as sliding down like a bamboo shoot unless the winding tension is applied. Therefore, appropriate tension is applied to the conductor sheet and the insulation sheet. I am producing. However, due to the tension required for this winding, the conductor sheet is stretched and plastically deformed, and the width of the conductor sheet becomes shorter, and the width of the conductor sheet becomes shorter than the width in the material state when it becomes a winding. However, there was a difficulty in matching the design values with the actual dimensions. Therefore, a hard metal sheet that has been hardened to minimize this plastic deformation is used as the conductor sheet of the winding.

Further, as a feature of the large-capacity sheet winding,
Since the windings are wound closely, the heat generated inside the windings is difficult to escape due to resistance loss, so it is necessary to forcibly cool them. Therefore, it is necessary to put a cooling panel or a cooling duct through which a cooling medium can flow inside the winding.

[0005]

When a hardened, hardened metal sheet is used as a conductor sheet, the following problems occur. In other words, the panel that has the cooling medium existing in the sheet winding installed for cooling the winding inside passes through a spacer between two metal plates to create a passage for the cooling medium. There is. Since the spacer and the two metal plates are fixed by welding, the entire panel is distorted at each part. As a result, the cooling panel and the conductor sheet do not fit well, and after the winding is completed, a gas gap is formed, causing a decrease in dielectric strength, and the gap increases the thermal resistance between the winding and the cooling panel. Therefore, the number of cooling panels has to be increased, and not only the thickness of the transformer must be increased, but also the number of man-hours is increased and the cost is increased. In particular,
As the thickness of the conductor sheet becomes thicker, the mechanical strength in the thickness direction of the conductor sheet becomes larger, and it is easy to form a gas gap, and its influence is remarkable.

Therefore, an object of the present invention is to prevent a decrease in dielectric strength due to the formation of a gas gap in the sheet winding, and to reduce the thermal resistance due to the gas gap to reduce the number of cooling ducts or panels.

[0007]

An annealed material is used for a metal sheet used for a conductor.

[0008]

[Operation] By doing so, since the conductor sheet is very soft, it is tightened by the tension of the sheet applied when the winding is manufactured,
Since it closely adheres to the inner winding part, it is difficult to form a gas gap. Further, the gas gap is reduced, so that the thermal resistance is reduced and cooling can be performed with a small number of ducts or panels.

As a result, since the number of cooling ducts or panels is reduced, the winding is reduced, and the number of man-hours is reduced, so that the manufacturing time can be shortened and the cost can be reduced. Moreover, unless the electric field enters a region with a gap shorter than the minimum value of the Paschen curve and a high electric field does not occur, the dielectric breakdown of the gas gap part does not occur, the dielectric breakdown of the insulator sheet does not decrease, and the reliability of the transformer is greatly increased. it can.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the conductor sheet 1 is an O material (annealed material) aluminum sheet, and the insulator sheet 2 is 25 μm.
Two thick polyethylene terephthalate films are used.

When the conductor sheet 1 is formed as described above, the O material is compared with the case of using the H material of the aluminum sheet that has been hardened by hardening and the case of using the soft O material. In the case of using, the aluminum sheet adheres well to the cooling panel 3, so that the heat transfer characteristic is improved by about 1.4 times that in the case of using the H material. Further, the gas gap does not become a defect, and the insulation breakdown voltage of the insulating sheet 2 can be prevented from lowering. Reference numeral 4 is a spacer that constitutes the cooling panel 3.

The same effect can be obtained by using not only aluminum but also copper sheet for the winding in the conductor sheet 1 of the sheet-wound transformer of the present invention. Further, the effect does not change even if an insulating sheet such as PEN, PEEK or PPS is used as the insulating sheet 1 instead of polyethylene terephthalate.

[0013]

As described above, according to the present invention, it is possible to reduce the gas gap in the sheet winding, and to obtain a sheet winding that does not cause a reduction in the dielectric strength of the winding that causes a defect in the gas gap. be able to. In addition, since the cooling characteristics are improved and the number of cooling ducts or panels can be reduced, the winding can be made smaller, the manufacturing time can be shortened, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view near a cooling panel of a sheet winding using the annealed sheet conductor of the present invention.

[Explanation of symbols]

 1 ... Conductor sheet 2 ... Insulator sheet 3 ... Cooling panel

Claims (1)

[Claims] 1. A sheet wound transformer formed by winding a conductor sheet and an insulating sheet, wherein an annealing material is used for a metal sheet constituting the conductor sheet.