JPS5863109A - Transformer - Google Patents

Abstract

PURPOSE:To provide a transformer with large capacity and dielectric strength, and freed from cavitation and static electricity discharge, by a method wherein both end portions of a cooling duct are put out of both ends of a leaf coil insulating sheet and expanded in the circumferential direction. CONSTITUTION:A cooling duct 7 has expanded tubiform portion 17 at the both ends, so refrigerant carriers gather from all over the liquid path 19 to the cubiform portion 17 of which sectional area is large. The refrigerant carriers, then, flow out to a insulating pipe 12 via a joint 21. Due to this large sectional area of the cubiform portion 17, the flowing speed of the refrigerant carriers around the joint 21 can be lowered, and cavitation and static electricity discharge used to be caused by increment of the refrigerant carriers flowing speed can be prevented, as well as the cooling duct is protected from erosion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a foil-wound wire formed by overlapping and winding a metal sheet and an insulating sheet, and cools the inside of this winding.

Concerning transformers with ducts, transformers with foil-wound windings generally have a good space factor and are small and compact.
Because it is lightweight, it is being considered to be applied not only to low-voltage, small-capacity transformers, but also to high-low-voltage, large-current transformers.
The important issues in this case are improvement of cooling capacity and dielectric strength.

FIG. 1 shows an example of a conventional large capacity transformer. A well-known foil-wound winding duct is provided by overlapping and winding a metal sheet 3 made of an aluminum sheet or the like and an insulating sheet M' made of a resin film or the like around the main leg of the iron core ffQ provided in the tank l. For example, the low voltage winding 5 has 1
A plurality of cooling ducts 7 are built into each of the high voltage windings 6. In the cooling duct 2, there is Freon 113 and Fc.
A circulating cooling circuit is constructed in which a refrigerant such as ys is passed by a pump 8, and the heat generated in each winding 5.6 is sent to the cooling duct 7 by the pump 8 to evaporate the refrigerant. In addition, the 4-liquid %'II made of stainless steel provided on the upper and lower ends of the windings 5 and 6 is connected to the cooling duct 2 through the insulated pipe 12'ae, and is approximately A high-temperature medium such as insulating oil, 8F, or gas is sealed inside the coil, and the windings 5 and 6 are insulated. 2. The low voltage winding 5 is wound around the outer periphery of the main leg of the iron core 1 via an insulating pipe 15, and the high voltage winding 6 is wound around the outer periphery of the low voltage winding 6 via an insulating barrier 16. Also, in Figure 1, 8 shows the @ line lead wires that are directly connected to the present invention, and the tank! Bushings that can be pulled out to the outside are omitted.

Transformers with this cooling method utilize evaporative heat for cooling, so they have excellent cooling characteristics and are suitable for large capacity transformers. However, transformers with conventional structures However, there are still some problems, which are obstacles to its application to large-capacity transformers.

One of the problems is the insulation between the high voltage winding 6 and the metal shield plates 13 provided above and below each winding 5.6. The high-voltage winding 6 shown in Figure 1 has an inner end connected to the neutral point, and the outer end where the metal sheet 3 is wound has a higher potential, and the outermost end is the line terminal, which is generally insulated in stages. It is. In this respect, although the insulation of this transformer is rational in principle, it has the disadvantage that electric field control in the vertical vertical direction shown in FIG. 1 between the high voltage winding 6 and the metal shield plate 13 is not performed. FIG. 2 shows this in an electric field distribution diagram. This figure shows only the upper part of the winding. The equal-level planes indicated by dotted lines at 8 in FIG. 2 extend from the high-voltage winding 6 and wrap around the electrostatic shielding material 14 provided at the end of the line. The shape increases the potential gradient at the edge of the material 14.

Furthermore, the ends of the metal cooling duct 2 built in between the high-voltage windings 6 are thin like the central part of the duct, and moreover, the ends of the duct protrude beyond the metal sheet 3 of the windings 6. However, the width of the insulating sheet 4 is larger than that of the metal sheet 3, and the end of the duct does not protrude outward from the end of the insulating sheet 4. ), the electric field becomes extremely concentrated, resulting in a very low partial discharge inception voltage. Furthermore, the creeping surface of the insulating pipe 12 connected to the cooling duct 2 becomes a weak point. Due to these points, the insulation between the end of the winding and the metal shield plate 13 inevitably becomes weak, so it is necessary to increase the insulation distance or increase the pressure of the 8F6 gas sealed in the tank 1. Measures are being taken to increase insulation strength. For this reason, the outer dimensions of the transformer become larger and the weight increases, and the tank needs to have a high voltage-resistant structure, which has the disadvantage of increasing the transformer cost.

Another problem is that the ends of the cooling duct 2 have a small thickness and a small area like the central part of the duct, so insulation at the ends of the duct is poor.

The flux of the refrigerant around the connection port that connects to the pipe 12 increases by several tens of times compared to the flow rate of the refrigerant flowing through the cooling duct 7, causing cavitation around the connection port and increasing the electrostatic capacity of the refrigerant. It has the disadvantage of causing electrical discharge in the refrigerant.

As a result, due to cavitation and electrostatic discharge, the metal plates that form the cooling ducts, which are several millimeters thick, are eroded, causing holes to open over a long period of time, causing accidents where the refrigerant inside the ducts leaks to the outside. .

The present invention has been made in view of the above circumstances, and has a high dielectric strength and does not cause cavitation or electrostatic discharge in the cooling duct in a device that is equipped with a foil-wound wire and has a cooling duct built into the winding. The present invention provides a transformer that is comparable to a large capacity transformer.

That is, in the transformer of the present invention, both ends of the cooling duct are made to protrude from both ends of the insulating sheet of the foil-wound winding, and a tubular part extending in the circumferential direction of the duct is formed by expanding on both of the protruding ends. .

Embodiments of the present invention will be described below with reference to drawings.

3 to 8 show an embodiment of the transformer of the present invention, and the same parts as in FIG. 1 are denoted by the same reference numerals [7].

As shown in FIG. 3, each cooling duct 2 provided inside each of the low-voltage winding 5 and the high-voltage winding 6 has an insulating sheet 4 at both ends in the axial direction connected to each winding 5.6. At both ends of each cooling duct 7, which protrudes outward from both ends of the insulating sheet 4, a tubular part 1 is provided along the circumferential direction of the duct.
7 is the expansion formation. Structure of cooling duct 2 ytW.

Referring to Figure 4, the cooling duct 2 is made of a metal plate made of stainless steel or copper and is formed into a cylindrical shape with a gap 18 along the axial direction. A liquid passage portion 19 is formed at both ends, and a tubular portion l? having a circular cross section in the circumferential direction is formed. is formed as a liquid collecting pipe. FIG. 5 is an enlarged sectional view taken along the 41st DV-V line, and the liquid passage section 19 is constructed by making flat metal walls 20 facing each other with a gap of several millimeters along the axial direction of the duct. The tubular portion 12 is formed by expanding both ends of the metal plate flat wall 20 to have a perfect circle or an ellipse in cross section to have a diameter larger than the width of the liquid passage portion. Note that the tubular portions 17 formed at both ends of the cooling duct 7 have connection ports 2) for connecting with the insulating vibrator 12. Also, the liquid passage portion l? of the cooling duct 7? As shown in FIG. 6 and FIG. 7, a plurality of spacers 22 are arranged in a straight line along the duct axis direction at intervals in the circumferential direction. This spacer 22 is sandwiched between metal plate flat walls 20 forming the liquid passage part 19 of the cooling tact 7, and both ends thereof are located at both ends of the liquid passage part 19. Therefore, the liquid passage portion 19 extends in the axial direction of the duct over the circumferential direction of the duct and is partitioned into a plurality of passages by the spacer 22 .

8. The spacer 22 may be arranged in the liquid dripping portion 19 parallel to the duct axis direction, or may be arranged at an angle.

Furthermore, as shown in FIG. 3, inside the high voltage winding 6, there are a plurality of cooling ducts 21 to 2 as cooling ducts 2. , but these cooling ducts? ,~2. The protruding lengths of both ends of the high voltage winding 6 protruding from the insulating sheet 4 are different from each other. T, that is, the protrusion length of both ends reaching the cooling duct 21 located on the outermost side is the smallest,
The protruding length of both ends of cooling ducts 7 and 8 located in the middle is cooling duct 1. The cooling duct is the second largest and located on the innermost side? , the protrusion length of both ends is the largest. In other words, the protrusion lengths of both ends are set to increase sequentially from the outermost cooling duct 7I to the innermost cooling duct 711711, so that each of the cooling ducts 71 to 2. The positions of the respective tubular portions 17 formed at both ends also differ depending on the protruding lengths of both ends. In addition, each cooling duct)y+~7. The axial length of is set according to the protruding length of both ends protruding from each high voltage winding 6.

Therefore, in the transformer configured in this manner, both ends of the cooling duct 7 protruding from both ends of the insulating sheet 4 in the low voltage winding 5 and the high voltage winding 6 serve to control the electric field in the vertical direction, Excessive electric field concentration around the ends of the windings 5.6 can be alleviated. In particular, each cooling duct 7 provided inside the high-voltage winding 6 is set so that the protruding length of both ends increases sequentially from the outermost cooling duct 21 to the inner cooling duct F7*a7m. This makes it possible to equalize the electric field in the insulating space between the high voltage winding 6 and the metal shield plate 13 as shown in FIG. 8, thereby further preventing excessive electric field concentration.

Further, both ends of the cooling duct 7 protruding from the winding 5.6 are connected to a tubular portion 1 having a diameter larger than the width dimension of the liquid passage portion 19.
Since the cooling duct 7 is expanded and formed, the cooling duct 7 is smaller than the conventional one.
It is possible to alleviate the electric field concentration at the end of the electrode, and it is possible to significantly improve the partial discharge inception voltage and breakdown voltage. As a result, the insulation distance between the winding end and the metal shield plate 13 can be reduced.

Furthermore, the gas pressure of the 8F6 gas, which is an insulating medium, sealed in the tank 1 can be lowered, and the entire transformer can be made smaller and lighter, thereby reducing costs.

Furthermore, since the tubular portions 12 having a large cross-sectional area along the circumferential direction are expanded and formed at both ends of the cooling duct 2, the refrigerant flowing from the entire circumference of the liquid path portion 19 of the cooling duct 7 has a large cross-sectional area. It collects in the tubular part J7 at the upper end of the duct, and flows out into the insulating pipe 12 through the connection ports 2. In this way, the tubular part 1
Since the cross-sectional area of 1 is large, the flow velocity of the refrigerant around the connection port 21 can be kept low compared to the conventional method (2). Therefore, cavitation and static electricity that occur due to an increase in the flow velocity of the refrigerant can be suppressed. It is possible to prevent the occurrence of electrical discharge and to prevent erosion of the cooling duct.

Further, in this embodiment, since the spacer 22 is provided inside the cooling duct 7, the refrigerant flowing inside the cooling duct 2 is guided by the spacer 22, and the tubular part 17 at the lower end of the duct 1 is guided by the spacer 22. Since it is evenly distributed over the entire circumferential direction of the liquid path J9 and flows well in the liquid path 19,
The cooling effect of the refrigerant on the windings 5.6 can be improved.

In addition, the low voltage winding 5 and the high voltage winding 6 are applied to the iron core 2 with strong tension.
Alternatively, when winding the insulation barrier 12, the cooling duct 7 provided within the winding 5.6 is closed because the spacer 22 acts as a reinforcing aggregate and stops receiving the tension of the winding 5.6. It is possible to prevent the liquid path section 19 of No. 7 from being crushed by tension.

Note that a spacer provided inside the cooling duct is not necessarily required.

As explained above, the transformer of the present invention improves the insulation properties of the foil-wound winding, making it compact and lightweight, and reducing costs. The reliability can be improved by preventing the occurrence of discharge, and it can be effectively used in large equipment transformers.

[Brief Description of the Drawings] Figure 1 is a sectional view showing a conventional transformer, Figure 2 is an explanatory diagram showing the electric field distribution at the winding end of the conventional transformer, and Figure 3 is a diagram showing the transformer of the present invention. FIG. 4 is a perspective view showing a cooling duct in the transformer of the present invention, FIG. 5 is a sectional view taken along line v-v in FIG. 4, and FIG. FIG. 7 is a cross-sectional view taken along the line Vl--Vl, FIG. 7 is a cross-sectional view taken along the line ■-■ in FIG. 4, and FIG. 8 is an explanatory diagram showing the electric field distribution at the winding end in the transformer of the present invention. l...tank, 2...iron core, 3...metal sheet,
4... Insulating sheet, 5... Low voltage winding, 6... High voltage winding, 7... Cooling duct, II... Liquid guide #←, 12
... Insulating pipe, 12 ... Tubular part, 19 ... Liquid path part, 22 ... Spacer. Applicant's agent Patent attorney Takehiko Suzue 2 Illustrations of 3 spears and 5 illustrations of spears

Claims (2)

[Claims] (1) A device comprising a foil-wound winding formed by overlapping and winding a metal sheet and an insulating sheet, and a cylindrical cooling duct for flowing a refrigerant for cooling the winding inside the winding, in which the cooling Both ends in the axial direction of the duct are made to protrude outward from both ends of the insulating sheet of the foil-wound winding, and these ends are expanded to form a tubular shape along the circumferential direction of the duct. A transformer formed by forming a part. (2) The protruding length of both ends of the foil-wound winding of the plurality of cooling ducts provided inside the foil-wound winding is determined from the outermost cooling duct to the innermost cooling duct. 2. The transformer according to claim 1, wherein the transformer is set to gradually increase in size as the cooling duct increases.