JPS5889811A - Foil-wound transformer - Google Patents

Abstract

PURPOSE:To cool at a roughly constant refrigerating temperature over the entire windings while maintaining electrical insulation good under high tension by a method wherein a liquid refrigerant is caused to flow downward from the upper part of a high-tension side refrigerant duct and then to flow vaporizing upward from the lower part of a low-tension side refrigerant duct. CONSTITUTION:Liquid refrigerant is let out a pump 7 to be supercooled and goes into the upper part of a refrigerant duct 6' located in the outmost side of a high-tension coil 5. The liquid refrigerant then goes into the lower parts of refrigerant ducts 6. The refrigerant procedes in the refrigerant ducts 6, vaporizing, and combines in a manifold 15 to be led into a condenser 16. The vaporized part of the refrigerant condenses in the condenser 16 and is supercooled under the condensed liquid surface 17. The degree of supercooling is so set that the refrigerant does not vaporize in the refrigerant ducts 6' wherein it flows downward and that it immediately starts vaporizing upon entering the refrigerant ducts 6 wherein it flows upward.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a foil-wound transformer in which a cooling duct is built into a coil formed by overlappingly wound a foil-like conductor and an insulating sheet.

Conventional technology and its problems Foil-wound transformers have the advantage of being smaller and lighter than transformers using linear conductors because the area factor of the wrapped conductor is good. In order to apply it to high-voltage, large-capacity transformers, it is necessary to improve the cooling ability of the coil and provide the coil with high insulation ability. It is designed to directly cool the heat generated from the conductor.

As shown in Fig. 1, this type of conventional foil-wound transformer consists of a coil body formed by overlapping and winding a foil conductor 2 and an insulating sheet 3 on the outside of an iron core l, and this coil body is a low-voltage coil. 4 and a high-voltage coil 5, each of which has a built-in annular cooling duct 6. There is a narrow gap inside this cooling duct.
4 is filled, and the Joule heat generated within the foil-wound winding is taken away by the pump 7. The refrigerant 14, which has risen once by absorbing heat, is cooled by cooling water 9 in an external cooler 8, and is sent into the duct again. The liquid collection pipe 10 is made of metal such as stainless steel, and an insulated pipe 11 is used to connect it to the cooling duct, so the liquid collection pipe 10 is connected to the tank 12.
The ground potential is taken as follows.

On the other hand, the cooling duct and the coil are at almost the same potential because the cooling duct is wrapped inside the coil, and the insulation between them and the outside is represented by the insulating 8F gas 13 sealed in the tank. Ru.

In FIG. 1, the lead wires of the windings that are not directly connected to the present invention and the pushing wires that lead them out of the tank are omitted.

The foil-wound transformer described above is called a separate foil-wound transformer because the circulation circuit through which the refrigerant for cooling flows and the insulator 13 for insulation are completely separated. It has the advantages of being significantly smaller and lighter, and has high insulation reliability.

However, the nine conventional separate foil-wound transformers shown in FIGS. 1 and 2 have the following problems.

In other words, in conventional transformers, the flow direction of the refrigerant in the cooling duct was constant (from bottom to top) as shown in Figure 3, so as the temperature increases along the flow direction of the refrigerant, The temperature of the coil also increases accordingly. This creates a large temperature gradient within the coil in its axial direction, with the temperature being highest near the outlet of the cooling duct.

In order to generate this axial temperature gradient within the coil, the maximum temperature of the coil must be kept below a certain value due to the heat resistance of the material used, and the number of cooling ducts F must be controlled during manufacturing. This was a very big drawback considering that it had to be minimized as much as possible.

In order to avoid a rise in the temperature of the refrigerant along the flow direction within the cooling duct, it is conceivable to flow the refrigerant while evaporating it within the cooling duct. However, in high-voltage transformers that require high electrical insulation, the inside of the insulated pipe (11) connecting the cooling duct (6) to the liquid collecting pipe section, which has an earth potential, must be completely filled with liquid. Otherwise, high electrical insulation could not be maintained.

Purpose of the Invention The present invention has been made in consideration of the circumstances described above, and is a method of evaporating the refrigerant in the cooling duct while maintaining electrical insulation against high voltage, so as to prevent a temperature gradient from occurring within the coil. The purpose is to provide a foil-wound transformer.

Summary of the invention: A liquid phase refrigerant flows from the top to the bottom of the cooling duct on the high voltage side, and the refrigerant flowing out from the cooling duct flows from the bottom to the top of the low voltage side cooling duct while being evaporated. This aims to achieve the above objectives.

Effects of the Invention According to the present invention, it is possible to realize a foil-wound transformer that maintains electrical insulation against high voltages and can cool the entire winding to approximately a constant temperature from corrosion.

Examples of the invention Examples of the present invention will be described below with reference to FIG.

In FIG. 4, elements that are the same as those of the prior art are designated by the same numbers as in FIGS. 1 to 3, and their explanations will be omitted.

The supercooled liquid phase refrigerant discharged from the pump (7) is sent to the outermost cooling duct on the high pressure coil (5) side.
e), from which the liquid phase refrigerant then flows into the lower part of the other cooling duct (6). Cooling duct (6
), the refrigerant flows while evaporating, and the refrigerant flows through the manhold ttS.
and is led to the condenser αe. The refrigerant vapor condenses in the condenser αe and is further subcooled below the condensed liquid level.

The product of supercooling of the refrigerant does not evaporate in the cooling talitic crystal where the refrigerant flows downward, but it flows into the cooling duct (6) where the refrigerant flows upward and starts evaporating immediately. be done.

Next, the effects of the present invention will be explained. First, the high voltage coil (
5) Since the part with the highest voltage is filled with liquid phase refrigerant, high electrical insulation is maintained against high voltage. Cooling duct (6) where refrigerant evaporates inside
) The temperature of the refrigerant in the cooling duct is constant, so there is no temperature gradient between the top and bottom of the cooling duct.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the schematic configuration of a conventional foil-wound transformer.
Fig. 2 is a partially enlarged view of Fig. 1, Fig. 3 is a diagram showing the flow direction of the refrigerant in the cooling duct constituting the foil-wound transformer of Fig. 1, and Fig. 4 is the foil-wound transformer according to the present invention. It is a figure showing one example of the composition of a container. 4...Low voltage coil 5...High voltage coil agent
Patent Attorney Noriyuki Chika (and 1 other person) Figure 1 (1) /4 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a foil-wound transformer, a foil conductor and an insulating sheet are layered and wound around the outside of a vertical core, and a cooling duct is built in between the windings, through which refrigerant flows. A foil-wound transformer characterized in that the refrigerant flows from the upper part of the cooling duct toward the lower part, and the refrigerant flowing out from the cooling duct flows from the lower part to the upper part of the cooling duct on the low voltage side while being evaporated.