JPS58108726A - Transformer - Google Patents

Abstract

PURPOSE:To prevent over heat and to offer a separate-type transformer effectively applied to a large-capacity transformer by a method wherein an increase in current density by winding leakage magnetic flux at both end sections of the metal sheets of foil windings is controlled. CONSTITUTION:A low-voltage winding 4 and a high-voltage winding 5 are composed of foil windings wound by superposing metal sheets 7 and insulating sheets 8. An insulating cylinder 3 and an insulating barrier 6 are provided between the low-voltage winding 4 and an iron core 2, and at the gap between windings 4, 5 respectively. Cooling ducts 9 are positioned in concentric circle shape in the inside of each winding 4, 5 at predetermined intervals. In the low- voltage winding 4 and the high-voltage winding 5 contained the cooling ducts 9 composed in this way, leakage magnetic flux in the windings is absorbed to silicon steel plates 15, 15 forming the cooling ducts 9, and eddy current by leakage magnetic flux crossing the silicon steel plates 15, 15 is hardly occurs at both the end sections of the metal sheets 7 to generate no local over heat.

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to a transformer comprising a foil-wound winding in which a metal sheet and an insulating sheet are overlapped and a cooling duct built into the winding through which a cooling medium is passed. Regarding.

Technical Background of the Invention Foil-wound transformers with foil-wound windings have a good space factor, are small in size,
Due to its ability to reduce weight, it is possible to reduce the
Small capacity transformers with relatively low voltages of the order of kVA have already been put into practical use and are now on the market.

Recently, in view of its excellent advantages, high voltage has been introduced.

Research is underway to expand the application to large-capacity transformers, such as 275kV and 300MVA transformers, but the key lies in how to improve the cooling capacity of the windings and provide high insulation capacity to the windings. . Although such high-voltage, large-capacity transformers have not yet been put into practical use, the cooling method for the windings in foil-wound transformers is to incorporate a cooling duct inside the windings, and to use a coil with excellent insulation properties. A so-called heat/mother-tube type system is being considered, in which a refrigerant is pumped in to directly cool down the heat generated from winding loss.

FIG. 1 shows a transformer of this type. 1 in the diagram
1 is a tank filled with an insulating gas such as insulating oil or SF6 gas as an insulating medium, and an iron core 2 is provided inside this tank 1.

A low voltage winding ftJJ4 is wound on the outside of the main leg 2a of the iron core 2 via an insulating tube 3, and a high voltage winding 5 is wound on the outside of the low voltage winding 4 via an insulating barrier 6. has been done. These low voltage winding 4 and high voltage winding 5 - metal sheet 7 such as aluminum foil and insulating sheet 8 such as resin film
It is composed of foil-wound wires made by overlapping and winding.

Note that the valley windings 4 and 5 are insulated by insulating oil or gas sealed in the tank 1. A cooling duct 9 is built inside the low voltage winding 4 and a cooling duct 9 is built inside the high voltage winding 5. This cooling duct 9 has a cylindrical shape that electrically forms one turn.
It is formed by bending a thin flat duct made of a metal plate, and is wound around the winding 4.5 in a concentric manner. Inside this cooling duct 9, there is a Freon 1
In the process of passing through the cooling duct 9, this refrigerant uses the latent heat of evaporation of the refrigerant to generate heat in the gauze 4 and 5, and causes the winding 4.5 to pass through. Cooling. Then, this refrigerant is cooled and condensed by water cooling in the condenser 10, and the liquefied refrigerant is stored in a refrigerant tank 11 and sent by a pump 12 into a cooling duct 9 provided in the winding 4.5. It will be done. That is, this refrigerant circulation circuit and the insulating medium within the transformer are separated. Also,
The liquid guide pipe 13 that guides the refrigerant is made of metal such as stainless steel, and an insulated flat ingot 14 is used to connect the liquid guide pipe 13 and the cooling duct 9. It is insulated from earth potential parts such as 1. Since the cooling duct 9 is wound within the windings 4 and 5, the potential of the cooling duct 9 is connected to approximately the same potential as the wound portion of the windings 4 and 5.

In addition, in FIG. 1, the lead wires of the windings 4 and 5, the drawer bushing, etc., which are not directly related to the present invention, are omitted.

In a transformer using this cooling method, the circulation circuit through which the refrigerant in the cooling reservoir flows and the insulating medium in the insulation reservoir are separated (separate ≧
Therefore, a transformer equipped with this type of foil-wound winding will be referred to here as a separate foil-wound transformer. This cooling type transformer utilizes the latent heat of vaporization of the refrigerant, so it is expected to have excellent cooling characteristics and is promising for large-capacity transformers.

Problems with the Background Art However, in this transformer, due to the relationship between leakage magnetic flux in the low-voltage and high-voltage windings 4 and 5, the current density at both ends of the windings 4 and 5 in the axial direction (width direction) becomes a dog. Therefore, there is a problem in that heat generation at both ends of the winding becomes locally large.

Therefore, the low voltage and high voltage windings 4, 5 made of foil-wound windings
An analysis of the magnetic flux distribution at is shown in Figure 2. That is, the distribution of the winding leakage magnetic flux in the windings 4 and 5 is such that the leakage magnetic flux passes through the gap between the windings 4 and 5 provided with the insulating barrier 6, and the leakage magnetic flux passes through the gap between the windings 4 and 5, and is distributed to the outside at both ends of the windings 4 and 50. It is something that spreads in both directions. At both ends of the windings 4 and 50, there is almost no spread of leakage magnetic flux (called cressong) in the radial direction of the windings 4 and 50, which occurs in normal windings, and there is no radial component of leakage magnetic flux. There is no linkage with the current flowing through both ends of the metal sheet 70 of the wire 4.5. This is due to the following reason. The metal sheet 7 of the windings 4 and 5 has a large extent in the axial direction (width direction), and a large path is created at both ends of the metal sheet 70 that conducts eddy currents along the axial and circumferential directions, and leakage magnetic flux flows through the metal. When the metal sheet 7 attempts to spread out and invade both ends of the sheet 7 in the radial direction, eddy currents are generated at both ends of the metal sheet 7 . This is because this eddy current generates leakage magnetic flux in the opposite direction, and this leakage magnetic flux eliminates the radial component of the leakage magnetic flux that invades both ends of the metal sheet 70. For this reason, the windings 4 and 5, that is, the foil-wound windings have a feature that the mechanical force in the axial direction is small.

However, on the other hand, eddy currents due to leakage magnetic flux are generated at both ends of the metal sheet 7 in the windings 4 and 5 because the eddy currents are added to the normal current at both ends of the metal sheet 70. IIi', the flow density is greater than in other parts of the metal sheet 7 where only the flow flows. Therefore, there is a problem in that the current density distribution in the axial direction of the metal sheet 7 is biased and uniform at both ends of the sheet. Moreover, metal sheet 6
The current density at both ends of the metal sheet 7 of the windings 4 and 5 increases as the distance from the gap between the windings 4 and 5 increases. That is, the current density at both ends of the metal sheet 70 increases as the distance from the gap between the windings increases. For example, in the low-voltage winding 4, the innermost metal sheet 71 is located at the farthest position from the gap between the windings 4 and 5.
The current density is highest at both ends. In the high-voltage winding 5, the electric voltage V''11 density is highest at both ends of the metal sheet 720 on the outermost circumferential side, which is located farthest from the gap between the windings 4 and 5. 5, the current density distribution from the center of the winding to the end of the metal sheet 72 on the outermost side (indicated by line A), and the current density distribution on the innermost side, which is the position closest to the gap between the windings 4 and 5. The current density distribution (indicated by line B) from the center of the winding to the end of the metal sheet 73 is shown. In the figure, line C is the average density of frost on the metal sheet 7. According to this diagram, in the outermost metal sheet 7, an average current density (indicated by line C) of 7 to 7 is applied to a very limited area at the end, which is a large range of winding heights. 8 times N N flows.

The reason why the current density increases at both ends of the metal sheet 70 located away from the gap between the windings 4 and 5 is because the radial component of the leakage magnetic flux moves away from the gap between the windings 4 and 5. This is because eddy currents are generated in response to the increase in size.

Therefore, as a large current locally flows through both ends of the metal sheet 70 in the winding 4.5, heat generation at both ends of the metal sheet 7 becomes significantly large, resulting in local overheating. Therefore, the above-mentioned problem is a major hindrance in applying a transformer having a foil-wound winding to a large-capacity transformer.

Purpose of the Invention The present invention is based on magnetic flux leakage at both ends of a metal sheet of a foil-wound wire! The object of the present invention is to provide a separate type transformer that prevents overheating by suppressing an increase in JL current density and can be effectively applied to large capacity transformers.

Summary of the Invention The transformer of the present invention has at least the surface portion of the cooling duct built in the foil-wound winding made of a ferromagnetic material, thereby absorbing leakage magnetic flux in the ferromagnetic portion of the cooling duct and forcibly winding it. This is intended to suppress the generation of eddy currents due to leakage magnetic flux at both ends of the metal sheet by oriented in the axial direction of the metal sheet.

Embodiments of the Invention The basic structure of the transformer of the present invention, as shown in FIG. A cooling duct 9 is built into each of these windings 4.5, and these cooling ducts 9
A refrigerant circulation circuit for flowing refrigerant is connected to the refrigerant.

FIG. 4 shows an enlarged view of a winding portion in an embodiment of the transformer of the present invention. As described above, the low-voltage winding 4 and the high-voltage winding 5 are composed of foil-wound windings in which the metal sheet 7 and the insulating sheet 8 are wrapped in layers, and the insulating cylinder 3 is placed between the low-voltage winding 4 and the iron core 2. , winding 9 - An insulating barrier 6 is provided in the gap between the wires 4, 5. The cooling ducts 9 are arranged concentrically within each of the windings 4 and 5 at a predetermined interval. One set of cooling ducts 9 has a cylindrical configuration that does not electrically form one turn, for example, a plurality of arc-shaped ducts that are divided into multiple parts in the circumferential direction and formed by curved thin flat ducts. are combined into a cylindrical shape with an interval of 1~. Alternatively, the set of cooling ducts 9 may be formed by forming entirely thin flat ducts into a cylindrical shape with a gap left. The cooling duct 9 is wound with a metal sheet 7 and an insulating sheet 8 with a winding angle of 4°5, and the metal sheet 7 is guided from the inner circumferential side to the outer circumferential side through the gaps between each duct of the cooling duct 9. ing.

In this embodiment, the cooling duct 9 is formed of a ferromagnetic material, such as a silicon steel plate 15, as a metal plate. That is, two thin steel plates 15.1
5 are assembled vertically. Specifically, each silicon-10 = steel plate 15.15 is attached to one side of the thin flat refrigerant passage 9a in the cooling duct 9 and the rib-shaped refrigerant guide portion 9b that is continuous with the upper and lower ends of the refrigerant passage 9a. These silicon steel sheets 1 are press-formed to form the walls of
5.15, for example, sandwiching the spacer pieces 16 and combining them facing each other,
The periphery of each silicon steel plate 15.15 is sealed by welding to produce a duct. In the figure, 9c is a connection port with the insulating pipe 14. In addition, the thickness of silicon steel plate 75°15 is 1 inch,
The spacing between the silicon steel plates 16 and 16 is 1 stud degree. Although silicon steel sheets generally have high hardness, using non-oriented and relatively low grade silicon steel sheets does not have such high hardness and is easy to process. Using this duct, a plurality of cooling ducts 9 are formed into one cylindrical shape, or a cylindrical cooling duct 9 is formed integrally.

In addition, silicon steel sheets are generally used for iron cores and have high magnetic permeability, and even those with non-directionality have 1.
It has a magnetic permeability of over 2000 in the 5 Tesla region.

Therefore, in the low-voltage winding 4 and the high-voltage winding 5 that incorporate the cooling duct 9 configured in this way, the leakage magnetic flux within the windings is caused by the silicon steel plate 15, 15 forming the cooling duct 9.
The leakage magnetic flux is forcibly directed in the axial direction of the cooling duct 9 (in the axial direction of the windings 4 and 5) at the silicon steel plate 15 and 15, and reaches both axial ends of the cooling duct 9. be guided. In other words, the silicon steel plate 15°15 has a much higher magnetic permeability than the 1.0 magnetic permeability of the metal sheet and insulating sheet of the winding, so it is easier for magnetic flux to pass through it.
When the leakage magnetic flux tries to spread in the radial direction at both ends of the windings 4 and 50, the silicon steel plates 15 and 15 of the cooling duct 9 built in the middle of the windings 4 and 5 absorb the magnetic flux heading in the radial direction. This is forcibly guided in the axial direction and discharged from the end of the cooling duct 9 to the outside of the winding 4.5. For this reason, the amount of leakage magnetic flux (radial component) that crosses both ends of the metal sheet 7 of the windings 4 and 5 is significantly reduced, and eddy currents due to the leakage magnetic flux that cross the metal sheet 7 are generated at both ends of the metal sheet 7. Occurrence almost disappears. In other words, the spread 9 of leakage magnetic flux in the radial direction at both ends of the winding 4° 5 can be prevented by the silicon steel plate 15 of the cooling duct 9 without generating eddy currents at both ends of the metal sheet 7. Can be done. Therefore, almost no vortex current flows at both ends of the metal sheet 70, and the state is similar to that in which only a normal current flows, and the density of the stain flow is significantly reduced. The difference in current density between the current density and other parts of the metal sheet 7 can be significantly reduced, and non-uniformity of current density distribution in the axial direction of the metal sheet 7 can be significantly reduced. Furthermore, the increase in current density at both ends of the metal sheet 7 at positions successively away from the gap between the windings 4 and 50 in each winding 4.5 can be significantly alleviated. This is due to the following Shioyama. That is, the cooling duct 9 has high and low voltage windings 4 and 5.
Since they are arranged at a predetermined interval inside the cooling duct 9, the radial component of the leakage magnetic flux generated by the winding conductor in the portion closer to the winding gap than the cooling duct 9 cannot penetrate the cooling duct 913-, and is transferred from the cooling duct 9 to the winding conductor. This will not affect the winding conductor at a portion away from the winding spacing, and the radial component will be the same on both the inside and outside of the winding.

In this way, a vortex t is formed at both ends of the metal sheet 7 of the windings 4 and 5.
If R, does not occur, there will be no temperature rise at both ends of the metal sheet 70, and localized overheating can be prevented.

FIG. 5 shows the current density distribution (indicated by line A') of the metal sheet 72 located on the outermost side of the high voltage winding 5 in this embodiment, and the current density distribution (indicated by line A') of the metal sheet 73 located on the innermost side of the high voltage winding 5.
FIG. In addition, the cooling duct 9
is manufactured by combining two silicon steel plates with a magnetic permeability μ2000 and a buoyancy 1+a+ with an interval of 1 strip. According to this, the maximum current density at the end of the metal sheet (72+7a) is 1/1 from V2 compared to the conventional case shown in FIG.
It can be seen that the number has been reduced to 3.

FIG. 6 shows another embodiment of the cooling duct 9. In FIG.

The cooling duct 9 in this embodiment consists of 14- two metal plates 1 made of non-magnetic material such as stainless steel plates;
7.17 are combined with the spacer pieces 16 in between, and the peripheral edges of the metal plates 17.17 are sealed by welding to form a duct, and the surfaces of each metal plate 17.17 are coated with ferromagnetic iron powder. A ferromagnetic material such as
A ferromagnetic layer 18 is formed as a surface layer of a metal plate 17.17. 2. By incorporating this cooling duct 9 into each of the windings 4 and 5, the same effects as in the embodiment described above can be obtained.

In this embodiment, the entire cooling duct 9 is heated.

Compared to the case where the cooling duct 9 is made of a magnetic metal plate, the thickness of the cooling duct 9 as a whole becomes larger in order to obtain the same effect using a material with the same magnetic permeability, but the original function of the cooling duct 9 is In order to send the refrigerant without leaking it to the outside, the cooling duct 9 is manufactured using a metal plate 17.17 that has the optimum properties of being easy to process, such as a stainless steel plate, and then the metal plate 17. There is an advantage that the ferromagnetic layer 18 can be formed on the surface of the magnetic layer 17.

Therefore, the metal plate forming the wall of the cooling duct 9 has
It is required to have relatively low electrical conductivity so that excessive eddy currents do not flow, and sufficient rigidity to withstand radial mechanical force. Therefore, in the present invention, when the entire cooling duct 9 is formed of a ferromagnetic metal plate as in the former embodiment, and when the cooling duct 9 is formed entirely of a ferromagnetic metal plate as in the latter embodiment, a ferromagnetic metal plate is formed on the surface of the non-magnetic metal plate as in the latter embodiment. In either case where the body is provided, a metal plate having the above-mentioned properties is used. Furthermore, the cooling duct of the present invention is not limited to the case in which the entire metal plate is made of ferromagnetic material (the former embodiment), but may be any other as long as at least the surface portion of the metal plate is made of ferromagnetic material. It is assumed that the region formed of the ferromagnetic material in the metal plate covers the entire surface. As ferromagnetic metal plates, there are electric and magnetic iron plates such as silicon steel strips and magnetic steel strips, and the ferromagnetic layer formed on the surface of the metal plate is made of amorphous magnetic thin film in addition to iron powder. It can be formed by wrapping it around.

Effects of the Invention The transformer of the present invention has ferromagnetism in the metal plate of the cooling duct built into the foil-wound winding, thereby suppressing the generation of eddy currents at both ends of the metal sheet of the winding, thereby reducing the current flow. The density can be reduced to prevent overheating or eddy current losses at both ends of the metal sheet. Therefore, it is possible to take advantage of the feature of foil-wound windings, which is that the axial mechanical force is small, and solve the eddy current problem, which is the biggest problem with foil-wound windings, making it effective for large-capacity transformers. Applicable to

[Brief explanation of the drawing]

Fig. 1 is a longitudinal side view showing the basic configuration of a foil-wound transformer of the separator type, Fig. 2 is an explanatory diagram showing the leakage flux distribution in a conventional foil-wound winding, and Fig. 3 is a conventional foil-wound transformer. A line diagram showing the current density distribution in the metal sheet of the winding, FIG. 4 is a sectional view showing an embodiment of the foil-wound winding portion of the transformer of the present invention, and FIG. 5 is the foil-wound winding in the same embodiment. A diagram showing the current density distribution of the wire metal sheet, and FIG. 6 is a sectional view showing another embodiment of the cooling duct. 17- 1...tank, 2...iron core, 4...low voltage winding, 5
... High voltage winding, 7... Metal sheet, 8... Insulating sheet, 9... Cooling duct, 15... Laminated steel plate, 1
7... Non-magnetic metal plate, 18... Ferromagnetic layer. Applicant's agent Patent attorney Takehiko Suzue 1Q- Figure 3 Figure 4

Claims (1)

[Claims] A device comprising a foil-wound winding formed by overlapping a metal sheet and an insulating sheet, and a cooling duct made of a metal plate built into the winding, wherein at least a surface portion of the metal plate forming the cooling duct is ferromagnetic. Transformer 0 characterized by being formed of a body