JPS60261118A - Foil-wound transformer - Google Patents

Abstract

PURPOSE:To reduce electromagnetic mechanical force on a short circuit by changing length in the axial direction of windings at every winding, arranging C- shaped disks, which are formed by winding silica steel plates and cutting one positions on the circumferences of the silica steel plates, at both end sections of each winding through insulators and clamping the disks to a core. CONSTITUTION:A metallic sheet 4a and an insulating sheet 4b are superposed and wound on an insulating cylinder in the periphery of a leg section 1a for a core 1 while a foil-shaped low-tension winding 5a, to which end-section paddings in approximately the same thickness as the metallic sheet 4a are executed, and the same foil-shaped high-tension winding 5b on the outside of the winding 5a are arranged at the end sections of the metallic sheet 4a. Disks 8 are fitted at both end sections of these foil-shaped windings 5a, 5b through insulators 6. The disk 8 is formed in a C-shaped disk, which is shaped by winding a silica steel plate to a ring shape and cutting one position on a circumference thereof, and fixed by a resin. The end sections of a winding for a low-tension winding 5a are brought near to the disks 8 in the low-tension winding 5a. The foil-shaped windings 5a, 5b, the insulators 6 and the disks 8 are clamped and fastened by a core clamping fitting 2.

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 be made smaller and lighter due to their excellent winding space factor, good potential distribution, and easy manufacturing. It is widely used in low voltage, small capacity transformers.

The structure of the foil-wound transformer is as shown in Fig. 4.
Foil windings 5a and 5b formed by winding a metal sheet 4a and an insulating sheet 4b around an insulating cylinder 3, and a tightening plate 9 attached to both ends of the foil winding in the axial direction via an insulator 6. The foil winding 4 insulator 6 and the clamping plate 9 are fixed by the iron core clamping metal 2. 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) Since 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 wire winding. As a means to reduce this eddy current loss, a silicon steel plate with good magnetic permeability, for example, is placed near the axial end of the winding to reduce the radial component of the magnetic flux, but the potential of this silicon steel plate is set to the ground potential. Therefore, it is necessary to maintain a certain insulation distance from the high-voltage winding, and there is a limit to reducing the radial component of the magnetic flux.

(2) Foil windings are usually made of sorted aluminum, and the windings are supported by placing conductors at both axial ends of the windings with end pads of the same thickness, as shown in Figure 4. It is done. Aluminum sheets have lower strength than the copper wire commonly used for rectangular wire windings, and the strength of the supporting insulators is also lower than that of supporting methods for rectangular wire windings, so the axial mechanical force in the event of a short circuit accident can be kept sufficiently low. There is a need. However, due to manufacturing errors, if the lower ends of the low-voltage winding and the high-voltage winding are misaligned in the axial direction, for example, in a three-phase 100 MV A transformer, if there is a misalignment of 1 Q mm, an external damage of about 10 tons will occur. Thrust works.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned problems with foil-wound wires, reduce load loss due to eddy currents and reduce the axial component of electromagnetic mechanical force during short circuits, and provide a foil-wound transformer. shall be.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention provides a foil-wound transformer having a foil winding in which a metal sheet and an insulating sheet are wound in an overlapping manner. The ends are padded with a thickness equivalent to that of the metal sheet, and a C-shaped disk cut at one point on the circumference is placed on both ends of which a silicon steel plate is wound through an insulator. In addition, the twist between the disk and the axial end of the metal sheet of the winding is varied depending on the insulation class of the winding.

[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. Around the leg portion 1a of the iron core 1, a metal sheet 4a and an insulating layer 4b are layered and wound around an insulating tube 3, and at the end of the metal sheet 4a there is a metal sheet 4a having a thickness almost the same as that of the metal sheet 4a. A foil-like low-voltage winding 5a having end tabs is arranged, and a foil-like high-voltage winding 5b having a similar configuration is arranged outside of the foil-like low-voltage winding 5a. A disk 8 is attached to both ends of these 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 hardening it with resin for convenient handling. It is being Since the disk 8 is generally kept at or near the ground potential, the minimum distance between the metal sheet 4a of the windings 5a and 5b and the disk 8 is determined by the insulation class of each winding.

In the present invention, whereas conventionally all the windings had the same length (length in the axial direction and width of the conductor), the low voltage winding 5a is characterized in that the end of the winding is brought closer to the disk 8. Further, the foil windings 5a and 5b, the insulator 6, and the disc 8 are tightened and fixed by the iron core clamp 2. It is.

That is, the leakage magnetic flux 7 generated in the axial direction at the metal sheet 4a portion is transferred to the disk 8 wound with a silicon steel plate having high magnetic permeability, and the magnetic flux 7 that bends in the radial direction at the end of the metal sheet 4a remains small. , the radial component of leakage magnetic flux decreases rapidly.

FIG. 3 shows the tendency of change in eddy current loss of the windings with respect to the distance between the metal ends 4a of the foil windings 5a and 5b and the disk 8 in a VC100MVA three-phase two-winding transformer. The vertical axis represents the ratio (%) of eddy current loss to resistance loss in 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 winding 5a is moved closer to the disk 8Vc, the eddy current loss on the low-voltage winding side is reduced, which is effective in reducing the loss of the entire transformer. Also, if the axial length of the low voltage winding 5a is increased, the same metal '/-)4
In order to obtain the cross-sectional area of a, the thickness of the metal sheet 4a can be reduced, and the radial thickness of the low-voltage winding 5a can be reduced accordingly.

As a result, the inner diameter of the high-voltage winding 5b can be reduced, so the length and weight of the metal sheath 4a of the high-voltage winding 5b can be reduced accordingly, and the loss of the high-voltage winding 5b can be reduced.

Regarding the electromagnetic mechanical force at the time of short circuit, the windings 5a and 5 at the time of manufacture
Even if the axial position of b is shifted, if the length of the shift is smaller than the length of the stretched low-voltage winding, the difference in radial magnetic flux components at the upper and lower ends of the high-voltage winding 5b is small, and the metal sheet The force generated as an external force is smaller than when the widths of the high-voltage winding 1w5a and the low-voltage winding 5b are the same but their positions are shifted from each other. On the other hand, in the case of the low-voltage winding, since the end of the winding approaches the disk 8, the leakage magnetic flux component in the radial direction is significantly reduced, so that the mechanical force in the axial direction can also be reduced.

〔Effect of the invention〕

As described above, according to the present invention, the axial length of the winding wire is changed for each winding wire, and a silicon steel plate is wound around both ends of each winding wire with an insulator interposed therebetween. By arranging a C-shaped disk cut at one place and fixing it with a core clamp, it is possible to provide a foil-wound transformer with low loss and low mechanical force during short circuit.

In addition, in order to reduce the radial component of the magnetic flux, instead of using silicon steel plates with a disk configuration as described above, blocks made by stacking rectangular silicon steel plates are placed at both ends of the winding. You can also obtain sufficient effects.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a perspective view showing a disk used in the present invention, and Fig. 3 is a graph showing the eddy current reduction effect of a disk made of silicon steel plate. , Fig. 4 is a cross-sectional view showing a conventional foil-wound transformer.
4a...Metal sheet 4b...Insulating sheet) 4C...End tab 5a...
・Low voltage winding 5b...High voltage winding 6...Insulator 7・
...Leakage magnetic flux 8...Disk 9...Tightening plate agent Patent attorney Noriyuki Chika Figure 1 Figure 3

Claims (2)

[Claims] (1) Wrap a metal sheet and an insulating sheet over each other. In a foil-wound transformer having a foil winding, the axial end of the metal sheet of the foil winding is provided with an end pad having the same thickness as the metal sheet, and an insulator is placed between the ends of the end pad. A C-shaped disc is wound around a silicon steel plate and cut at one point on the circumference, and the insulation between the disc and the axial end of the metal sheet of the winding is removed. A foil-wound transformer characterized by changing according to class. (2) The foil-wound transformer according to claim 1, wherein the insulating sheet and the end padding at the end of the foil winding are extended in the axial direction to form an insulator.