JPS58182212A - Transformer - Google Patents

Abstract

PURPOSE:To prevent local overheating by a method wherein, with respect to the conductivity of a metal sheet in an inside winding of a foil-wound winding, the conductivity exists on the internal periphery is made greater than that on the external periphery and the conductivity on the external periphery is made greater than that on the internal periphery in the case of the outside winding thereof. CONSTITUTION:Foil-wound low tension and high tension windings 4, 5 prepared by stacking metal sheets 7 on an insulating sheet 8 have preselected breadth and isolated by an insulating cylinder 6. The metal sheet 7 is provided with the predetermined difference in conductivity and, regarding the winding 4, the difference between the internal and external peripheral sides 41, 42 is to at about 1.5X10<-8>OMEGAm, whereas the thickness of the windings is set to the ratio of 1:3. Regarding the winding 5, the same is applied to the difference between the internal and external peripheral sides 51, 52 and the ratio of the thickness of the windings. Cu is used for the windings 41 and 51, whereas Al is used for the windings 42 and 52. According to this construction, the quantity of magnetic flux in the radial direction transversing the end of the metal sheet 7 in the windings 41, 52 is considerably reduced and the current density in the end part is reduced and made uniform in general. For this reason, local overheating of the metal sheet 7 can be prevented, whereas reliability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a transformer equipped with a foil winding formed by overlappingly wound a metal sheet and an insulating sheet.

[Technical background of the invention]

Transformers equipped with foil-wound windings have a good space factor, making them compact and lightweight.
Small capacity transformers with a relatively low voltage of about 0.00 kVA have already been put into practical use and are on the Kanashi market. Recently, in view of the excellent advantages of this type of transformer, research has been conducted to expand its application to higher voltage, larger capacity transformers, such as 275 kV/300 MVA transformers.

The basic configuration of a transformer with foil-wound windings is as shown in FIG. That is, insulating oil or 8F6ff
An iron core 2 is installed inside a tank l filled with an insulating gas such as gas, and a low pressure winding of 1 m, which is an inner winding, is placed on the outside of the leg of this iron core 2 via an insulating cylinder 3! 4 is wrapped,
A high voltage winding 5, which is an outer winding, is wound on the outside of the low voltage winding 4 via an insulating barrier σ. Each of these windings 4.5 is constituted by a foil-wound winding formed by overlapping and winding a metal sheet 2 such as an aluminum sheet and an insulating sheet 8 such as a resin film. Note that 9 in the figure is an electrostatic shield.

[Problems with background technology]

In this foil-wound transformer, due to the relationship of winding leakage flux,
The current density at both ends of the metal sheet 7 in the width direction (both ends of the windings 4 and 5 in the axial direction) in the low-voltage and high-voltage windings 4 and 5 becomes large, resulting in excessive heat generation at both ends of the metal sheet 7. I have one.

That is, at both ends of the metal sheet 7, the windings 4.
An eddy current force is generated by a component of the leakage magnetic flux passing through the gap between the coils 5 and 5 that tends to spread in the radial direction of the winding, and this eddy current generates a magnetic flux that cancels the radial component of the leakage magnetic flux. Therefore, in addition to the normal current, eddy current force I flows through both ends of the metal sheet 10, so the current density becomes higher than in other parts of the metal sheet 7 where only the normal current flows, and the metal sheet 7 as a whole Current density distribution becomes non-uniform.

Since the current density is high at both ends of the metal sheet 7, the current loss is large and the amount of heat generated is significantly increased, resulting in local overheating.

On the other hand, the current at both ends of the metal sheet 7 tends to increase as the metal sheet 1 is located farther away from the gap between the windings 4 and 5.

That is, both ends of the metal sheet 11 located on the innermost side of the low voltage winding 4, which is the farthest position from the gap between the windings 4.5, and the metal sheet 7 located on the outermost side of the high voltage winding @5. The current density is highest at This is because the radial component of the leakage magnetic flux increases as it moves away from the gap between the windings 4.5, and eddy currents flow at the ends of the metal sheet 7 accordingly.

As an example, FIG. 2 shows the outermost metal sheet 71 of the high voltage winding 5, which is the outer winding, and the innermost metal sheet 13, which is the position closest to the gap between the windings 4.5. The current distributions between the center and the ends in the width direction are shown, respectively.

Note that in the figure, the A line shows the current distribution of the outermost metal sheet 11, and the B line shows the current distribution of the innermost metal sheet 7s. FIG. 3 shows the current distribution at the winding end with respect to the radial distance of the winding in the high voltage winding 5, which is the outer winding. According to the diagrams in Figs. 2 and 3, the current is larger on the outer circumferential side than on the inner circumferential side, and the current at the edge of the outermost metal sheet 7 is higher than that of the innermost metal sheet. It can be seen that the current at the end of C) 7s is much larger.

Therefore, when the current density at the end of the metal sheet r on the outer peripheral side is large as described above, the loss becomes large and local overheating occurs.

[Purpose of the invention]

The present invention provides a transformer that reduces current concentration at the ends of metal sheets in foil-wound windings, thereby suppressing local overheating.

[Summary of the invention]

The transformer of the present invention is equipped with inner and outer windings made of foil-wound wires, and the inner circumferential side of the inner winding located nine positions away from the gap between both windings, and the outer circumference of the outer winding. By making the conductivity of each side section larger than the other sections, the leakage flux is directed toward the winding axis in the section away from the winding gap, thereby reducing current concentration at the edges of the metal sheet, especially away from the winding gap. This suppresses the concentration of current at the edge of the metal sheet located at a certain position.

[Embodiments of the invention]

An embodiment of the transformer of the present invention will be described with reference to FIG.

An insulating tube 3 is fitted into an iron core 2 provided inside a tank 1 filled with an insulating medium, and a low voltage winding 4, which is an inner winding, is wound around this insulating tube 3. A high-voltage winding 5, which is an outer winding, is wound on the outside with an insulating layer 6 interposed therebetween. These low-voltage and high-voltage windings 4 and 5 are constituted by foil-wound windings formed by overlapping and winding a metal sheet 1 and an insulating sheet 8. Note that the widths of both windings 4.5 are constant throughout. In addition, the low voltage winding 4 changes the electrical conductivity of the metal sheet 1 at the inner circumferential side 4, which is a position away from the gap between the windings 4 and 5, to the outer circumference, which is a position close to the gap of winding #4.5. The conductivity is set to be higher than the conductivity of the metal sheet 7 on the side portion 43. This inner peripheral side portion 41 and outer peripheral side portion 4. The difference in conductivity between the metal sheets 1 is approximately 1.5×10 −80 m.

The ratio of the lengths of the inner circumferential side portion 41 and the outer circumferential side portion 4 in the radial direction is approximately 1=3. The high-voltage winding 5 is connected to a metal sheet 1 located on the outer circumferential side 5, which is located at the 9th position from the gap between the windings 4 and 5.
The conductivity of the metal sheet 1 is set to be larger than the conductivity of the metal sheet 1 at the inner circumferential side 51, which is a position close to the gap between the windings 4.5. The difference in electrical conductivity between the metal sheets 7 on the outer peripheral side 5m and the inner peripheral side 55 is about 1.5 x 10-80 m, and the length ratio in the radial direction is 1:3. Therefore, the metal sheet 7 wound around the inner peripheral side 4N of the low voltage winding 4 and the outer peripheral side 53 of the high voltage winding Is5 is made of, for example, copper (7
Conductivity at 5°C 2. l X 1゜0-8Ω・I!
l), the outer peripheral side 41 of the low voltage winding 4 and the inner peripheral side 5 of the high voltage winding 5! The metal sheet 7 wound around the metal sheet 7 is made of K, for example, aluminum (electrical conductivity at 75 DEG C.: 3.7 x 10-' Ω·m) in order to reduce the electrical conductivity.

Therefore, when a current is passed through each metal sheet 7 in the low voltage winding 4 and high voltage winding 5 configured in this way,
The leakage magnetic flux from the winding 4.5 passes through the gap between the windings 4.5 and tends to spread from the outer circumferential side 43 to the inner circumferential side 41 to the ends of the windings 4 and 5 and to the end 51. Here, when the radial component of the leakage magnetic flux enters the metal sheet, an eddy current is generated, but the metal sheet 7 at the inner peripheral side 41 of the low voltage winding 4I4 and the outer peripheral side 5 of the high voltage winding 5 has a high electrical conductivity. Eddy currents due to the radial component of leakage magnetic flux tend to flow in the rounded shape. Therefore, the magnetic flux generated by the eddy current in the opposite direction to the winding leakage flux increases, and this large magnetic flux directs the radial component of the winding leakage flux in the winding axial direction, so that the inside of the low-voltage winding 4 The amount of leakage magnetic flux in the radial direction passing through the circumferential side 4 and the outer circumferential side 531 of the high voltage winding 5 is reduced. Therefore, the inner peripheral side 41 of the low voltage winding 4 and the high voltage winding 5
The amount of the radial component of the leakage magnetic flux across the edge of the metal sheet 7 at the outer peripheral side 5s of is significantly reduced, the current density at the edge of the metal sheet 1 is reduced, and the current in the central part of the metal sheet 7 is reduced. If the current density is about the same as the density, the current density distribution of the entire metal sheet 7 will be approximately equal. Furthermore, since the current density is reduced at the ends of the metal sheet 1, heat generation due to current loss is also reduced, and local overheating is eliminated. In this way, it is possible to suppress an increase in the current density at the ends of the metal sheet 1 at the inner circumferential side 41 of the low voltage winding 4 and the outer circumferential side 5 of the high voltage winding 5, thereby preventing local overheating.

Note that the current density at the end of the metal sheet 7 at the outer peripheral side 4 of the low voltage winding 4 and the inner peripheral side 5 of the high voltage winding @5 hardly increases as in the conventional case.

Therefore, the current density of the low pressure winding @4 is the inner circumferential side 41 and the outer circumferential side 4! ) is averaged over the entire area, and it is extremely high! The current density of I5 is also averaged over the entire inner peripheral side part 5 and outer peripheral side part 53, and the current loss of both windings @4.5 is also averaged, so that local overheating can be prevented.

Figure 5 shows the relationship between the loss at the end of the low-voltage winding 4 and the distance in the radial direction of the winding. D#i! 1 and 2 respectively show losses when the conductivity of the metal sheet 7 of the inner peripheral side portion 41 is increased. In addition, winding 4
The electrical conductivity σ of the outer circumferential side is σ. The conductivity σ of the inner peripheral side portion 41 was 1.5σ. shall be. According to this diagram, it can be seen that the loss in the inner circumferential side 41 of the winding 14 is significantly reduced as the conductivity of the inner circumferential side 41 is increased. FIG. 7 shows another embodiment. In this embodiment, the high voltage winding ill is arranged in a plurality of winding parts 5m+5b+5er in the radial direction.
5d, and set the width (height) of these winding parts 51 to 5d so that the width of the winding part located on the outer peripheral side is smaller than the width of the winding part located on the inner peripheral side, and Each winding part 51~
The conductivity of the metal sheet 7 of 5d is set so that the conductivity of the winding portion located on the outer circumferential side is greater than the conductivity of the winding portion located on the inner circumferential side.

According to this configuration, the conductivity of each of the winding parts 51 to 5d in the high voltage winding 5 increases as the winding parts are located closer to the outer periphery of the winding, so that the radial component of the leakage magnetic flux is The windings are oriented in the winding axis direction every ~5d. In this case, the degree to which the leakage magnetic flux is directed in the winding axial direction in the winding portions 51 to 5d gradually increases. Therefore, the current density at the end of each winding portion 51 to 5d of the high voltage winding 5 is reduced, and local overheating can be prevented. Further, in the high voltage winding 1115, the outermost metal sheet 7 is connected to the line end, so the potential becomes higher toward the outer peripheral side of the winding 5. However, each winding portion 5a to 5d
By making the width smaller as it is located closer to the outer periphery,
The ends of the winding portions 5a to 5d can be successively separated from the core yoke (not shown) toward the outer circumference of the winding 5. That is, the ends of the windings 5 can be separated from the core yoke depending on the position where the potential is high. This improves the electric field distribution in the high voltage winding 5 and allows the distance between the winding and the core yoke to be reduced.

〔Effect of the invention〕

The transformer of the present invention is characterized in that the conductivity of the metal sheet on the inner circumference side of the inner winding made of foil winding is increased by the conductivity of the metal sheet on the outer circumference side, and the conductivity of the metal sheet on the outer circumference side of the outer winding is increased. By making the electrical conductivity of the metal sheet thicker than the electrical conductivity of the metal sheet on the inner circumferential side, the edges of the metal sheet on the inner circumference side of the inner winding and the outer circumference of the outer winding are located away from the gap between both windings. This can reduce the current density of the metal sheet and prevent local overheating at the edge of the metal sheet.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing the inner and outer windings of a conventional transformer, Fig. 2 is a diagram showing a current distribution from the center to the end of the winding in the conventional winding, and Fig. 3 FIG. 4 is a diagram showing the current distribution at each end of the conventional outer winding in the radial direction; FIG. 4 is a schematic diagram showing an embodiment of the inner and outer windings in the transformer of the present invention; Fig. 5 is a diagram showing the current distribution at each end located in the radial direction of the inner winding of the present invention, Fig. 6 is an explanatory diagram showing the distribution of leakage magnetic flux in the winding of the present invention, and Fig. 7 is a diagram showing the distribution of leakage magnetic flux in the winding of the present invention. FIG. 6 is a schematic diagram showing another embodiment of the inner and outer windings of the inventive transformer; 1t...tank□, 2...iron core, 4...low voltage winding,
41... Inner circumferential side part, 41... Outer circumferential side part, 5... High voltage winding, 51... Inner circumferential side part, 5 Mushroom... Outer circumferential side part, 5
a to 5d... Winding part, 1... Metal sheet, 8...
Insulating sheet. Applicant's representative Patent attorney Suzue Takemon - Issho Shigeki (
-S C4 S$J Cloud Ministry Nib Gufeng ni Set ￥ (-Qiao! IO Figure 5 17 Figure

Claims (1)

[Claims] It has an inner winding wound around an iron core and an outer winding wound outside the inner winding, and these windings are composed of foil-wound windings made by overlapping metal sheets and insulating sheets. In the transformer, the conductivity of the metal sheet on the inner circumference side of the inner winding is made greater than the electric conductivity of the metal sheet on the outer circumference side of the outer winding, and the conductivity of the metal sheet on the outer circumference side of the outer winding is set to A transformer characterized by having a conductivity greater than that of the metal sheet on the side.