JPH0520883B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a foil-wound transformer equipped with a foil-like winding formed by overlappingly wound a metal sheet and an insulating sheet. This relates to a reinforced foil-wound transformer with reduced load loss.

[Technical background of the invention and its problems]

Foil-wound transformers have the characteristics of being able to achieve smaller size and lighter weight due to their excellent winding space factor, good potential distribution, and easy manufacturing.
It is widely used in low voltage, small capacity transformers such as KV and several hundred KVA.

The configuration of a foil-wound transformer is as shown in Figure 4.
A low-voltage side foil winding 5a and a high-voltage side foil winding 5 are formed by winding a metal sheet 4a and an insulating sheet 4b wider than the metal sheet 4a around an insulating cylinder 3 around the leg portion 1a of the
A clamping plate 9 is arranged at both ends in the winding axial direction of the foil windings 5a and 5b on the low and high voltage sides with insulators 6a and 6b interposed therebetween. The shaped windings 5a, 5b, the insulators 6a, 6b, and the clamping plate 9 are fixed. Note that the broken line in the figure indicates the distribution of the leakage magnetic flux 7.

A foil-wound transformer having such a configuration has the following problems.

(1) Because the foil winding has a wide conductor in the axial direction, eddy currents that tend to cancel out the radial component of the magnetic flux at the axial ends of the winding tend to flow. Therefore, the loss due to eddy current is much higher than that of a general rectangular winding. As a means of reducing this eddy current loss, there is a method of arranging a silicon steel plate with good magnetic permeability, for example, near the end of the foil-wound winding in the winding axis direction to reduce the radial component of the magnetic flux. Since the potential is set to ground potential, it is necessary to provide a certain insulation distance from the high-voltage side foil winding, which limits the ability to reduce the radial component of the magnetic flux.

(2) Foil windings are usually constructed from sheets of aluminum;
As shown in FIG. 4, the winding is supported by placing end pads having the same thickness as the conductor between the insulating sheets 4b at both ends of the foil winding in the winding axial direction. Aluminum sheets have lower strength than the copper wire commonly used for rectangular wires, and the strength of the supporting insulator is also lower than that of supporting methods for rectangular windings, so it is necessary to keep the mechanical force in the axial direction of the windings sufficiently low in the event of a short-circuit accident. There is. However, if the lower ends of the low-voltage side foil winding 4a and the high-voltage side winding 4b in the axial direction of the windings are misaligned due to manufacturing errors, for example, the 3-phase 100MVA
If there is a deviation of 10 mm in a transformer, an external thrust of about 10 tons will be exerted.

[Purpose of the invention]

It is an object of the present invention to provide a foil-wound transformer that solves the above-mentioned problems with foil windings and reduces load loss due to eddy currents and the winding axial component of electromagnetic mechanical force during short circuits. .

[Summary of the invention]

In order to achieve the above object, the present invention provides a foil-wound transformer having low-voltage and high-voltage side foil windings in which a metal sheet and an insulating sheet wider than the metal sheet are overlapped and wound. An end filler with a thickness equivalent to that of the metal sheet is applied between the insulating sheets at the ends of the winding axis of the metal sheet, and silicon steel plates are attached to both ends of the foil winding in the winding axis direction via an insulator. winding,
A C-shaped disk cut at one point on the circumference is arranged, and the distance between the disk and the axial end of the metal sheet of the foil winding is set so that the distance between the disk and the axial end of the metal sheet of the foil winding is smaller than that of the foil winding on the low voltage side. It is characterized by having shorter lines.

[Embodiments of the invention]

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

FIG. 1 shows a longitudinal sectional view of the internal structure of a foil-wound transformer. An insulating tube 3 is placed around the leg portion 1a of the iron core 1.
A metal sheet 4a and an insulating sheet 4b wider than the metal sheet are layered and wound on top of each other, and an end portion having approximately the same thickness as the metal sheet 4a is provided between the insulating sheets at the end of the winding axis of the metal sheet 4a. A low-voltage foil winding 5a provided with padding and a high-voltage foil winding 5b having a similar configuration are arranged outside of the low-voltage foil winding 5a. A disk 8 is attached to both ends of these low-voltage and high-voltage side foil windings 5a and 5b with an insulator 6 interposed therebetween. As shown in Fig. 2, the disc 8 is a C-shaped disc made by winding a silicon steel plate into a ring shape and cutting it at one point on its circumference, and hardened with resin for convenient handling. ing. Generally, the disc 8 is kept at ground potential or a potential close to it, so the minimum distance between the metal sheet 4a of the low-voltage side foil winding 5a and the high-voltage side foil winding 5b and the disc 8 is the minimum distance between each winding. Determined by insulation class.

In the present invention, whereas the conventional winding axial length (width of the conductor) was the same for all windings, in the low voltage side foil winding 5a, the end of the winding is brought closer to the disk 8. is a feature. Furthermore, the low-voltage and high-voltage side foil windings 5a and 5b, the insulator 6, and the disk 8 are tightened and fixed by the iron core fitting 2.

The action of the foil-wound transformer according to the present invention having the above configuration is as follows.

In other words, the leakage magnetic flux 7 generated in the axial direction of the winding at the metal sheet 4a portion is caused by the disk 8 wound with a silicon steel plate having high magnetic permeability, so that the leakage magnetic flux 7 generated at the end of the metal sheet 4a is curved in the radial direction of the winding at the end of the metal sheet 4a. 8, the winding radial component of the leakage magnetic flux rapidly decreases.

FIG. 3 shows the change tendency of the eddy current loss of the windings with respect to the distance between the end of the metal sheet 4a and the disk 8 of the low-voltage and high-voltage side foil windings 5a and 5b in a 100MVA three-phase two-winding transformer. The vertical axis represents the ratio (%) of eddy current loss to resistance loss of the winding. As is clear from the figure, the eddy current loss decreases exponentially with respect to the distance. Even if only the low-voltage foil winding 5a is moved closer to the disk 8, the eddy current loss in the low-voltage foil winding 5a is reduced, which is effective in reducing the loss of the entire transformer. Furthermore, by increasing the length of the low-voltage side foil winding 5a in the winding axial direction, the thickness of the metal sheet 4a can be made thinner in order to obtain the same cross-sectional area of the metal sheet 4a.
The radial thickness of the low-voltage side foil winding 5a can be reduced accordingly. As a result, the inner diameter of the high-voltage side foil winding 5b can be reduced, and the length and weight of the metal sheet 4a of the high-voltage side foil winding 5b can be reduced accordingly, reducing the loss of the high-voltage side foil winding 5b. Can be reduced.

Regarding electromagnetic mechanical force during short circuit, low pressure during manufacturing,
Even if the positions of the high voltage side foil windings 5a and 5b shift in the winding axial direction, the length of the shift is the same as that of the low voltage side foil winding 5a.
If the width of the metal sheet is smaller than the stretched dimension, the difference in magnetic flux components in the winding radial direction at the upper and lower ends of the high-voltage side foil-like winding 5b is small.
In the same case, the force generated as an external force is smaller than in the case where the positions of the foil winding a and the low voltage side foil winding 5b are shifted from each other. On the other hand, the low voltage side foil winding 5a has a winding end formed by a disk 8.
Since the leakage flux component in the radial direction of the winding is significantly reduced due to the approach, the mechanical force in the axial direction of the winding can also be reduced.

[Effects of the Invention] As described above, according to the present invention, a metal sheet,
In a foil-wound transformer having low-voltage and high-voltage foil windings in which a wide insulating sheet is layered and wound with this metal sheet, the metal A C-shaped circle is formed by wrapping a silicon steel plate through an insulator on both ends of the foil winding in the axial direction of the foil winding, and cutting one point on the circumference, with end padding of the same thickness as the sheet. In addition to arranging the plates, the distance between the disk and the axial end of the metal sheet of the foil winding is made shorter on the low voltage side foil winding than on the high voltage side foil winding, resulting in low loss. This makes it possible to provide a foil-wound transformer with low mechanical force during short circuit.

In addition, in order to reduce the radial component of the magnetic flux, instead of using the disk-shaped silicon steel plates as described above, blocks made by stacking rectangular silicon steel plates are placed at both ends of the winding. A sufficient effect can be obtained even if it is twisted.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a perspective view showing a disk used in the present invention.
The figure is a graph showing the eddy current reduction effect of a disk made of silicon steel plate, and FIG. 4 is a sectional view showing a conventional foil-wound transformer. 1... Iron core, 1a... Leg part, 1b... Yoke part,
2... Iron core tightening fitting, 3... Insulating tube, 4a... Metal sheet, 4b... Insulating sheet, 4c... End tab, 5a... Low voltage side foil winding, 5b... High voltage side foil shaped winding, 6... insulator, 7... leakage magnetic flux, 8...
...Disk, 9...Tightening plate.

Claims (1)

[Claims] 1. In a foil-wound transformer having a low-voltage and high-voltage side foil winding in which a metal sheet and an insulating sheet wider than the metal sheet are overlapped and wound, the ends of the metal sheet of the foil winding in the winding axial direction An end pad with the same thickness as the metal sheet is applied between the insulating sheets, and a silicon steel plate is wound around both ends of the foil winding in the winding axial direction with an insulator interposed therebetween. In addition to arranging the cut C-shaped disks, the distance between the disk and the axial end of the metal sheet of the foil winding is shorter on the low voltage side foil winding than on the high voltage side foil winding. A foil-wound transformer featuring: