JPS5878406A - Foil wound transformer - Google Patents

Abstract

PURPOSE:To obtain a foil wound transformer which ensures sufficient cooling capability and is resistive to a mechanical force in the radius direction by enhancing closer contact between metal foils and between metal foil and cooling duct. CONSTITUTION:A cooling duct 6 is built within the foil winding where the metal foil 2 and insulating sheet 3 are overlappingly wound. This cooling duct 6 is formed like a hollow having a small gap with a thin plate of elastic material, for example, stainless steel etc. or formed like a cylinder or arc not forming a turn. Since the cooling duct 6 is formed by an elastic material with a high internal pressure, close contact property between metal foils 2 and between metal foil 2 and cooling duct 6 are enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field of the invention The present invention uses a foil-like winding formed by overlapping metal foil and an insulating sheet, and furthermore has a cooling duct built into the winding. Regarding transformers.

(2) Conventional foil-wound transformers have the advantage of a good winding space factor and can be made smaller and lighter. Already several KV, several hundred KVAI! i!
It has been put into practical use in small capacity transformers with relatively low voltage. In recent years, in view of its excellent advantages, research has been carried out to expand its application to higher voltage and larger capacity transformers, such as 275KV and 300M VA class transformers, but the biggest key is how to improve cooling capacity and high insulation capacity. It depends on the ability of the windings to withstand the radial forces of short-circuit accidents. Although such high-voltage, large-capacity transformers have not yet been put into practical use, they are equipped with cooling ducts built into the windings to feed refrigerant with excellent insulation properties to cool the heat generated from winding losses. In other words, a heat pipe type foil-wound transformer is the most promising.

FIG. 1 shows a conceptual diagram of the known heat pipe type foil-wound transformer, FIG. 2 shows the structure of a cooling duct used therein, and FIG. 3 shows a sectional view of the cooling duct.

A low-voltage winding 4 and a high-voltage winding 5 each made of a metal foil 2 and an insulating sheet 3 are wound around a leg part 1 of the iron core, and a hollow cooling duct 6 is built in these windings. cooling duct 6
A refrigerant such as Freon R-113 is sealed in a thin gap in the hollow part, and the pump 7 circulates the refrigerant, absorbing the heat generated in the windings with the latent heat of evaporation of the refrigerant, and converting the vapor into the condenser 8. It is designed to be cooled and condensed through a cooling water pipe 9.

A refrigerant circulation cooling circuit is constructed in which the liquefied refrigerant is stored in a refrigerant tank 10 and further fed into the windings by a pump 7. The refrigerant pipes 11A, 11B are made of metal such as stainless steel, and the refrigerant pipes 11A, 11B are connected to the cooling duct 6 through insulated pipes 12A, 12B. is also connected to ground potential. On the other hand, the cooling duct 6 is electrically connected to the same potential as the adjacent winding because it is incorporated in the winding. Each part of the winding is insulated by an insulating medium such as insulating oil or SFs gas sealed in the tank 13.

In FIG. 1, winding lead wires or bushings drawn out of the tank 13 that are not directly related to the present invention are omitted.

(3) Problems with the conventional technology In the conventional transformer described above, the refrigerant circulation circuit for cooling and the insulating medium of the windings are completely separated. Here, we will call it a separate foil-wound transformer.

This separate foil-wound transformer utilizes the latent heat of vaporization of the refrigerant, so while it can be expected to have excellent cooling properties, it has the following problems.

That is, if a minute gap is created between the metal foils 2 wrapped around the insulating sheet 3 or between the metal foil 2 and the cooling duct 66I, there is a possibility that the heat transfer characteristics thereof will be deteriorated. In particular, when used in high-voltage, large-capacity transformers, insulation sheet 3
In order to prevent the dielectric strength from decreasing due to absorption of other insulators, drying treatment is required after winding assembly, but this drying treatment causes drying of the insulators, and between the metal foils 2 and between the metal foils 2. Gaps are created between the cooling ducts 6, which reduces the cooling effect and may cause overheating of the transformer.

In addition, in a foil-wound transformer, vertical dimension differences between the windings are unlikely to occur, and since the windings are foil-shaped, there is almost no horizontal component in the magnetic flux distribution at the top and bottom ends of the windings, so the windings in the event of a short circuit. The mechanical force in the axial direction of the wire is almost non-existent, but the problem is how to withstand the mechanical force in the radial direction of the winding. Particularly, when there are gaps between the metal foils 2 as described above, the rigidity of the winding decreases, and there is a risk that the winding will break due to buckling.

(4) Purpose of the invention The present invention has been made in view of the above points, and its purpose is to:
The object of the present invention is to provide a foil-wound transformer that can secure cooling capacity and withstand radial mechanical force by increasing the adhesion between metal foils and between the metal foils and a cooling duct.

(5) Structure of the Invention In the foil-wound transformer of the present invention, the cooling duct is formed into a hollow shape using a thin elastic body, and the pressure of the refrigerant sealed inside the cooling duct is set higher than the pressure filled with the insulating medium in the tank. It has the following configuration.

(6) Examples of the invention An embodiment of the present invention will be described below with reference to FIG.

A cooling duct 6 is built into the inside of the foil winding, which is formed by overlapping the metal foil 2 and the insulating sheet 3.
is formed into a hollow shape with a thin gap by a thin elastic material such as a stainless steel plate, and is formed into a cylindrical shape or an arc shape that does not form one turn.

The pressure of the refrigerant sealed in the cooling duct 6 after drying the contents of the transformer is the pressure of the insulating medium sealed inside the tank (atmospheric pressure in the case of insulating oil, 1.5 to 1.5 in the case of SF6 gas). 3kg1012).

In this embodiment configured in this way, the cooling duct 6
is an elastic material and its internal pressure is high, so when a gap is created inside the foil winding and the external pressure applied to the cooling duct 6 is reduced, the cooling duct 6 expands due to the pressure of the internal refrigerant and immediately closes the gap. It acts to fill in the .

Note that the thin elastic material forming the cooling duct 6 does not necessarily need to be used over the entire surface, and may be used only on one curved portion so that that portion expands due to internal pressure.

(7) Effects of the Invention In the foil-wound transformer of the present invention as described above, by inflating the cooling duct 6 by the pressure of the refrigerant inside, the insulating sheet and other insulating material dries up during the drying process of the contents of the transformer. between the metal foil 2 or between the metal foil 2 and the cooling duct B
111) is removed, and the adhesion between the metal foils 2 and between the metal foil 2 and the cooling duct 611 is improved. As a result, the heat transfer characteristics between the metal foil 2 and the cooling duct am can be significantly improved, and the required cooling capacity can not only be ensured, but also 1. In addition to increasing the rigidity of the winding itself, the refrigerant in the cooling duct 6 effectively acts as a buffer material, and sufficient strength can be ensured against radial mechanical force in the event of a short circuit.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating the structure of a conventional foil-wound transformer.
Fig. 2 is a perspective view showing the cooling duct structure used in the conventional type, Fig. 3 is a cross-sectional view of the main part of the cooling duct as in Fig. 1, and Fig. 4 is the winding of the foil-wound transformer according to the present invention. lli of the main part
It is a front view. 1... Iron core, 2... Metal foil, 3... Insulating sheet,
4...Low voltage winding, 5...High voltage winding, 6...Cooling duct 7...Pump, 8. ... Condenser, 9... Cooling water pipe, 10... Refrigerant tank, 118, 11B... Refrigerant line pipe, 12A. 12B...Insulated pipe, 13...Tank.

Claims (1)

[Claims] The contents of the transformer are constructed by winding a winding made of overlapping metal foil and insulating sheets around the legs of an iron core, and incorporating a hollow cooling duct within the winding. The contents of this transformer are housed in an insulating medium sealed in a tank, and the cooling duct is configured so that a refrigerant cooled by a cooling unit disposed outside the tank circulates. The foil transformer is characterized in that at least one curved surface of the cooling duct is formed of a thin elastic body, and the pressure of the refrigerant sealed inside the cooling duct is set higher than the pressure sealed of the insulating medium in the tank. Foil-wound transformer.