JPS5885509A - Transformer - Google Patents

Abstract

PURPOSE:To provide a transformer in which increase of current density at ends of windings is restricted and the temperature rise is suppressed without reducing the space factor of foil windings. CONSTITUTION:If load current flows in a low tension winding 4 and a high tension winding 5, eddy current to eliminate the horizontal component of the winding leakage flux scarcely flows at upper and lower ends of a thin metal sheet 7 but it flows in concentration to respective upper and lower ends of a shield plate 11 inside the low tension winding 4 and a shield plate 11 outside the high tension winding 5. Since upper and lower ends of the windings 4, 5, i.e. upper and lower ends of the metal sheet 7 becomes substantially flowing state of normal load current as in the sheet intermediate portion without upper and lower ends, excessive rise of the current density at upper and lower ends of the windings 4, 5 is retarded significantly. In this constitution, ends of the windings 4, 5 are not subjected to the abnormal temperature rise caused by the increase of the current density and the winding leakage flux does not leak out of the shield plate installed outside the high tension winding 5, thereby overheating of a wall of the tank 1 is prevented and the tank shield becomes unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transformer equipped with a low-voltage winding and a high-voltage winding comprising a foil-wound winding in which a metal sheet and an insulating sheet are wound in layers.

TECHNICAL BACKGROUND OF THE INVENTION A transformer equipped with this type of foil-wound winding has a good space factor, so it has the advantage of being compact and lightweight. Already several KV,
Small capacity transformers with relatively low voltages of about several 100 KVA have been put into practical use and are widely available on the market.

Recently, in view of its excellent advantages, research has been conducted to expand its application to higher voltage, larger capacity transformers such as 275KV and 300KVA. How to overcome the problem of excessive temperature rise at the ends of the windings due to eddy currents is the key to putting large capacity foil-wound transformers into practical use.

A conventional foil-wound transformer has the configuration shown in Figure 1. An iron core 2 is provided inside a tank 1 filled with an insulating gas such as insulating oil, SF, or gas as an insulating medium, and a low-voltage winding 4 is connected to the outer circumference of the legs of the iron core 2 via a green part 3. is wound around the outside of this low voltage winding 4? I! A green batho barrier 6 is wound with a high voltage winding 5. Each of these windings 4 and 5 is constituted by a foil-wound wire formed by overlapping and winding a metal sheet 7 made of aluminum or the like and an insulating sheet 8 made of resin film or the like. Clamps 9, 9 for tightening the iron core 2 and each winding 4, 5 are arranged above and on the F side of the upper and lower ends of each winding 4, 5. tank 1
A tank shield 10 is attached to the inside of the wall of the tank 1 to prevent the wall of the tank 1 from overheating due to magnetic flux leakage from the windings 4 and 5.

Problems with the Background Art Conventional transformers use low-voltage and high-voltage windings made of rectangular copper wire, so when a load current flows through the windings, the windings as shown by the broken line in Figure 1 Leakage flux occurs, but in a transformer with low IF and high voltage windings 4.5 made of foil-wound windings, when load current flows through windings 4 and 5, the horizontal component of the leakage flux is canceled. A large loop of eddy current flows through the upper and lower ends of the windings 4 and 5. As a result, the winding leakage magnetic flux of the foil-wound transformer passes vertically inside the windings 4 and 5, and exits from the windings 4 and 5, as shown by the two-dot chain line in Figure 1.
', then turn at almost a right angle. At this time,
Because a large eddy current flows superimposed on the load current at the lower end of each winding 4.5, the current density at the upper and lower ends of the windings 4 and 5 is lower than that of the windings 4 and 5 excluding the upper and lower ends. The current density is extremely high compared to the middle part of the current density. The characteristics of the current density distribution at the ends of the windings 4 and 5 are shown in FIG. According to this diagram, at the end of winding 4, the current density increases from the outer circumference to the inner circumference (line A), and at the end of winding 5, the current density increases from the inner circumference to the outer circumference. It can be seen that there is a tendency to increase (BI3). '1 at the ends of windings 4 and 5 in this way.
1) As a result of the excessive current density, only the 1F end of the winding 4°5 has an abnormally high temperature.

As a countermeasure against this phenomenon, the thickness of the metal sheet 7, which is a conductor in the windings 4 and 5, may be increased to reduce the current density at the ends of the windings to a level where the temperature rise does not become a problem. However, in order to wind the winding so that the winding thickness is uniform in the winding height direction (winding axial direction), approximately 90 mm of the total winding height, which is not affected by eddy currents except at the ends of the winding, is required. It is also necessary to uniformly increase the thickness of the metal sheet 7 in the middle portion of the winding, which occupies more than one inch. As a result, the DQ of the metal sheet 7 as a whole increases, and the greatest feature of the foil mahjong winding, which is a good space factor, is lost. Further, since the thickness of the metal sheet 7 is uniform, there is a problem in that it is difficult to implement a cooling structure that allows cooling of the ends of the winding to be much better than that of the middle part of the winding.

OBJECTS OF THE INVENTION The present invention provides four transformers that suppress increases in current density at the ends of the windings and prevent temperature rises without reducing the space factor of the foil-wound windings.

SUMMARY OF THE INVENTION The transformer of the present invention includes an electrically connected wire around one or both of the inner circumference of a low voltage winding (inner winding) made of foil-wound windings and the outer circumference of a high voltage winding (outer winding). By providing a conductive cylindrical shield plate that does not form a turn, eddy currents are hardly generated at the ends of the windings and are generated concentratedly at the ends of the shield plate. This suppresses the increase in current density at 5-.

Embodiment of the Invention Figures 3 to 5 show an embodiment of the transformer of the invention. The transformer of this embodiment has an iron core 2 provided inside a tank 1 filled with an insulating medium, similar to the previously mentioned known example.
A 1 m4 low-voltage winding consisting of a foil-wound winding made by overlapping a metal sheet 7 and an insulating sheet 8 and a high-voltage winding 5 are wound concentrically on the inside and outside, and clamps 9, 9 are provided. .

In the transformer according to the embodiment, a shield plate 11 is provided concentrically around the inner circumference of the low voltage winding 4 which is the inner winding in the tank 1, that is, between the low voltage winding 4 and the legs of the iron core 2.
A shield plate 11 is provided concentrically around the outer periphery of the high voltage winding 5 which is the outer winding, that is, between the high voltage winding 5 and the peripheral wall of the tank 1. The shield plates 11 and 11 provided on the inside of the low-voltage winding 4 and the outside of the high-voltage winding 5 are made of conductive metal and are made of a sufficiently thick plate with a gap having a predetermined diameter. It has a substantially cylindrical shape that is curved into a substantially cylindrical shape except for 12, and as shown in FIG. 4, at least one gap 12 is always formed along the axial direction so that one electrical turn is not formed. ing. It is the shield plate 11 that forms the gap f12 on the shield plate 1.
This is because when the entire structure forms one turn, a closed electric path is formed and current flows in the circumferential direction. The shield plate 1 provided around the inner side of the low-voltage winding 4 is fitted onto the outer periphery of the insulating cylinder 3. Furthermore, an insulator/griyer 13 is provided between the shield plate 11 and the low voltage winding 4. A shield plate 1 provided around the outside of the high-voltage winding 5 is fitted onto the high-voltage winding 5 via an insulator 14. For this reason, the insulating cylinder 3, the shield plate 11,
Insulating barrier 13, low voltage winding 4, insulating barrier 6, high voltage winding 5, insulating barrier 14, and shield plate 11 are provided concentrically in this order. Furthermore, magnetic shields 15 and 15 formed by laminating silicon steel plates, for example, are provided on the side faces facing the winding ends of the windings 4 and 5, respectively. It is a provision.

Therefore, in the transformer configured in this way, when a load current is passed through the low voltage winding 4 and the high voltage winding 5, each winding 4
, 5, almost no eddy current flows in the upper and lower ends of the thin metal sheet 7 for canceling the horizontal component of the winding leakage flux, and the shield plate 11 provided inside the low voltage winding 3 and the high voltage Eddy electricity flows in a concentrated manner at the upper and lower ends of the shield plate 11 provided on the outside of the winding wire 4. For this reason, the upper F end of each winding 4, 5, that is, the metal sheet 7 is in a closed state, so the winding 4
, 5, the extreme increase in current density at the upper and lower ends is significantly alleviated.

The characteristics of the current density distribution at the ends of windings a4 and a5 in this case are shown in FIG. In this diagram, the incoming wire shows the current density at the 4th end of the winding, and the A wire shows the current density at the 5th end of the winding. According to this diagram, it can be seen that the current density is significantly lower than the current density at the end of the winding in the conventional transformer shown in FIG. Therefore, the temperature at the 4.5-degree end of the winding does not rise significantly due to an increase in current density. A shield plate 1 provided on the outside of the high voltage winding 5
Since the winding leakage magnetic flux does not leak outside the tank 1, overheating of the wall of the tank 1 due to the leakage magnetic flux can be prevented, so the tank shield 10 conventionally attached to the wall of the tank 1 becomes unnecessary. In addition, since the winding leakage magnetic flux does not leak inside the shield plate 11 provided inside the low-voltage iron core 4,
Overheating of the iron core 2 and its surrounding metal structure due to winding leakage flux can be prevented. Furthermore, the magnetic shield 15.15 attached to the clamps 9, 9 prevents the winding leakage magnetic flux from winding 4,
This has the effect of further strengthening the straightness within the coils 5 and reducing the slight eddy current remaining at the upper and lower ends of the windings 4 and 5. And since the metal sheet 7 in each winding 4, 5 does not need to increase its overall thickness to avoid temperature rises due to eddy currents,
A decrease in the space factor of the winding 4.5 can be prevented.

The potential of the shield plate 11.11 can be set to the same potential as the metal sheet 7 of the adjacent winding 9-4.5, or to the ground potential, but the shield plate provided outside the high-voltage winding 5 When plate 1 is at ground potential, the third
As shown in FIG. 4, the shield plate 11 and the tank 1
The insulation distance d2 between the peripheral wall portion and the interphase distance d3 between the outer shield plates 11 of each phase in the case of three phases can be shortened to the structurally necessary minimum size. The insulation distance d1 between the high-voltage winding 5 of the present invention shown in FIGS. The insulation distance d4 between the high voltage winding 5 and the tank shield 10 can be shortened. That is, in the transformer of the present invention, since the shield plate 11 is arranged concentrically with the high-voltage winding 5, an insulating barrier 13 having a so-called multi-barrier insulation structure in which both are partitioned into a narrow gap by an insulating cylinder is provided. This is because it is possible to significantly shorten the insulation distance d1.

10- The effect of the invention is that by providing conductive shield plates on both sides, it is possible to prevent an increase in current density at the end of the winding and to prevent a rise in temperature, without impairing the space factor of the winding.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal side view showing the schematic configuration of a conventional transformer, Fig. 2 is a diagram showing the current density distribution at the end of the winding in the conventional transformer, and Fig. 3 is a diagram showing the current density distribution of the winding end of the conventional transformer. FIG. 4 is a plan view of the same, and FIG. 5 is a diagram showing the current density distribution at the end of the winding in the transformer of the embodiment. 1...tank, 2...iron core, 3...insulation tube, 4...
...Low voltage winding, 5...High voltage winding, 6...Insulation barrier, 7...Metal sheet, 8...Insulation sheet, 9...
Clamp, 11... Shield plate, 13.14... Insulating barrier, 15... Magnetic shield. 11- Fig. 1, Fig. 2

Claims (1)

[Claims] A low-voltage winding consisting of a foil-wound winding made of overlapping metal sheets and insulating sheets is wound around an iron core provided inside the tank, and a high-voltage winding consisting of the foil-wound winding is placed outside of this low-voltage winding. In one or both of the inner periphery of the low voltage winding and the outer periphery of the high voltage winding,
A transformer characterized by being provided with a cylindrical conductive shield plate that does not form one electrical turn.