JPH1126250A - Transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable heat generate din a core fastener to be efficiently dissipated by a method wherein a structural member of thermal conductivity is thermally connected to the core fastener. SOLUTION: A cooling copper structural member 8 T-shaped in cross section is fixed to the side plate of an iron fastener 6 with bolts. At this point, the cooling structural member 8 is composed of a part parallel with the side plate of the core fastener 6 and another part vertical to the former part. When the core fastener 6 rises in temperature, a strong ascending flow along the vertical plate part and a strong flow along the lower part of the side plate are generated by natural convection. Heat released from the side plate is conducted to the cooling structural member 8, and a strong ascending flow is generated around the cooling structural member 8. SF6 gas or the like of comparatively low temperature is fed from around to efficiently remove heat from the cooling structural member 8. By this setup, the side plate of a core fastener is restrained from rising in temperature so as to enhance a transformer in reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer core, and more particularly to a core clamp suitable for an SF ₆ gas-insulated transformer.

[0002]

2. Description of the Related Art Transformers installed in cities are strongly required to be non-flammable in terms of disaster prevention, and are also required to have large capacity and small size. An iron core, which is a main component of the transformer, is mechanically held by being tightened with an iron core clamp. Part of the magnetic flux leaking from the windings penetrates into the iron core clamp and generates heat due to eddy currents.

[0003] The SF ₆ gas insulated transformer, which is one of the non-combustible transformers, has a low cooling property because the SF ₆ gas, which is a refrigerant, has smaller physical properties related to cooling, such as density, specific heat, and thermal conductivity, than the liquid cooling medium. Low. In particular, most of the core clamps do not face the forced circulation gas flow path and are cooled only by natural convection, so that the temperature rise of the core clamps tends to increase.

[0004] As the capacity of the transformer is increased and as the size of the transformer is reduced, the magnetic flux penetrating into the clamp increases, and the heat generated by eddy current loss increases. Up to now, there has been no sufficient study on cooling of the metal clamps of the gas-insulated transformer.

[0005]

In an iron core clamp which mechanically holds an iron core of a transformer, an eddy current is generated due to a magnetic flux leaking from a winding and generates heat. Most of the generated heat is removed by natural convection of SF ₆ gas.Natural convection has a lower cooling effect than forced convection, etc., and the temperature rise of the core clamp is increased, so that the core and the core clamp are removed. There is a problem that the insulator or gas inserted between them deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to reduce the heat generated in the iron core clamp by the magnetic flux leaking from the winding, which has a lower cooling capacity than the liquid cooling medium. Effective removal with SF ₆ gas keeps the temperature of the iron core clamp low,
An object of the present invention is to provide a highly reliable transformer.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermally fastened, thermally conductive structural member to an iron core clamp for mechanically holding an iron core of a transformer. Is provided so as to be substantially parallel to the vertical direction (the direction of gravity).

[0008] The iron core fastening member is usually composed of a vertical plate member in a parallel direction and a horizontal plate member in a direction perpendicular to the silicon steel plate, which constitute the iron core. However, a temperature difference occurs in the vertical plate member in the height direction. Since relatively strong natural convection occurs, cooling is relatively good. On the other hand, the horizontal plate member hardly causes a temperature difference in the height direction, so that only weak natural convection occurs, and the temperature is higher than that of the horizontal plate member. As in the present invention, when a structural member having thermal conductivity and thermally connected to a high-temperature portion is provided such that the longitudinal direction of the structural member substantially coincides with the vertical direction (the direction of gravity), an iron core fastening member is provided. Is transmitted to the structural member by heat conduction, where a relatively strong natural convection is generated, so that the heat can be efficiently removed and the temperature of the iron core clamp can be kept low.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to FIGS.

FIG. 1 is a sectional perspective view showing a single-phase three-legged iron core according to an embodiment of the present invention, and shows about a half in the longitudinal direction of the iron core. Although not shown in the figure, a winding is wound around the iron core leg 1 formed by stacking silicon steel plates. The iron core leg 1 and the iron core outer leg 2 facing each other across the winding are magnetically coupled by upper and lower yoke 3 respectively. The iron core leg 1 and the iron core outer leg 2 are integrated by binding, and the iron core leg 1, the iron core outer leg 2 and the yoke 3 sandwich the iron core with the insulating plate 5 therebetween and bolt the upper and lower iron core clamps 6 and 7 with bolts ( (Omitted in the figure) to maintain the iron core shape,
It has a standing structure.

The above-mentioned iron core is arranged on an iron core base 4 provided in a tank (not shown). Although not shown, a blower and a cooler are connected to the tank through a cooling pipe. The SF ₆ gas supplied to the tank supplied from the blower cools the windings, the iron core, the tank, etc., and the SF ₆ gas whose temperature has risen flows from the tank to the piping, and is cooled by the cooler, and then cooled to the blower. The cycle of returning is repeated.

In this embodiment, a cooling structural member 8 made of copper and having a T-shaped cross section is fixed to the horizontal plate portion of the upper iron core clamp 6 with a plurality of bolts (not shown). ing.

Next, the test results of the present embodiment will be described in comparison with the results of a conventional structure (a structure without the cooling structural member 8 in FIG. 1).

The SF ₆ gas pressure is 0.5 MPa, the heat generation density of the upper core clamp 6 is about 400 kW per cubic meter, and the lower core clamp 7 is about 320 kPa.
W. In the conventional structure, the temperature rise (average) from the ambient gas temperature in the horizontal plate portion of the upper core clamp 6 is 4%.
The temperature was 9 ° C., and the temperature rise in the vertical plate portion was 22 ° C.
The temperature rise at the horizontal plate of the lower metal core clamp 7 is 27
℃, the temperature rise in the vertical plate portion was 9 ℃.

In the structure of this embodiment, the temperature rise at the horizontal plate portion of the upper metal core clamp 6 is reduced to 31 ° C., and the temperature rise at the vertical plate portion is reduced to 16 ° C. (average). Since the temperature rise of the lower iron core clamp 7 is relatively small,
In this embodiment, since the conventional structure was used, the temperature rise was almost the same as the conventional structure.

[0016] The mechanism resulting in such a result will be described. With respect to the temperature rise of the upper core clamp, the conventional structure generates a strong upward flow due to natural convection in the vertical plate and can remove heat, so that the temperature rise of the clamp vertical plate is relatively small. The upward flow changes direction at the horizontal plate portion and flows under the horizontal plate at a high flow velocity, but a high-temperature gas region is formed near the horizontal plate. The heat of the horizontal plate cannot be sufficiently transferred to the gas. In addition, natural convection flows also occur in the upper part of the horizontal plate, but the flow velocity is low, and the heat removal effect is small. For this reason, the temperature of the horizontal plate becomes considerably high.

On the other hand, also in this embodiment, a strong upward flow in the vertical plate portion and a strong flow in the lower portion of the horizontal plate are generated similarly. However, the heat of the horizontal plate portion is transmitted to the cooling structural member 8 by heat conduction, and generates a strong upward flow around the cooling structural member. Further, since a relatively low temperature gas is supplied from the surroundings, heat can be efficiently removed from the cooling structural member. The heated gas rises toward the tank ceiling and gives heat to the tank walls. As a result, the temperature rise of the horizontal plate portion of the cooling structural member 8 can be suppressed lower than that of the conventional structure.

Also in the lower metal core fastener, a strong upward flow occurs around the vertical plate portion, and the temperature rise in the vertical plate portion is small. On the other hand, the flow due to natural convection in the horizontal plate is small, but the flow created by the upward flow in the vertical plate flows on the upper surface of the horizontal plate,
In addition, since the gas temperature is relatively low, the temperature rise at the horizontal plate of the lower iron core clamp is only about 55% of the horizontal plate of the upper iron clamp. In the present embodiment, the conventional structure was used because the temperature rise of the lower core fastening metal has no problem with the conventional structure.

According to this embodiment, the heat of the iron core clamp is transmitted to the structural member for cooling which can be efficiently cooled by natural convection through heat conduction, and the heat is radiated, so that the temperature rise of the iron core clamp is reduced. About 60% of that of the first embodiment, and the deterioration of the insulating plate and gas can be prevented.

FIG. 2 shows another embodiment of the present invention.
FIG. 3 is a cross-sectional perspective view showing an upper iron core fastening member and its vicinity. 1 is the same as the embodiment of FIG. 1 except that the cross-sectional shape of the upper iron core clamp 6 is L-shaped. Regarding the temperature distribution of the horizontal plate of the upper core fastening member 6, the temperature on the vertical plate side becomes lower due to heat conduction to the upper core fastening member vertical plate having a relatively low temperature. Therefore, in the embodiment of FIG. 2, the cooling structural member 8 having an L-shaped cross section is arranged so as to be in contact with the high temperature portion of the horizontal plate. As a result, the temperature rise of the upper core clamp was only slightly increased from the temperature rise in the embodiment of FIG. 1, and substantially the same cooling performance was obtained. The cooling structural member 8 in the embodiment of FIG.
The manufacturing cost and weight can be reduced as compared with the embodiment of FIG.

In the embodiment shown in FIGS. 1 and 2, the material of the cooling structural member 8 is copper, but may be soft iron. When the cooling structural member 8 is made of copper, the generated eddy current loss is considerably small because the resistance of copper is small. On the other hand, in the case of soft iron, since the magnetic permeability is high, the leakage magnetic flux easily enters into the soft iron, and the resistivity of the soft iron is about 10 times that of copper, and the occurrence of eddy current loss in the cooling structural member 8 cannot be ignored. The temperature rise of the upper core clamp is about 5 ° C. higher than the temperature rise in the embodiment of FIG. 1. However, when the ambient gas temperature is low, when the heat generated by the core clamp is relatively small, the necessary cooling is required. Performance can be secured.

FIG. 3 is a sectional perspective view showing another embodiment of the present invention (only the vicinity of the outer leg of the iron core is shown), and shows the lower iron core tightening fitting and the vicinity thereof. The core outer legs 2 and the yoke 3 are fixed on the iron core base 4 with the insulating plate 5 interposed therebetween and tightened with the lower iron core tightening fitting 7. The mesh cooling structural member 9 is fixed in contact with the horizontal plate of the lower iron core fastening member 7. The other end is not shown in the drawing, but is fixed to the bottom plate of the tank. In the space below the lower iron core,
Due to the presence of the gas flow, the heat transferred by the heat conduction of the mesh cooling structural member is removed by the above-described gas flow. Further, since the mesh structure is quite rough, it does not hinder the flow and does not hinder cooling of the windings and the like. The same cooling effect can be obtained by using a flat plate having a plurality of openings instead of the mesh-shaped cooling structural member.

FIG. 4 is a sectional perspective view showing another embodiment of the present invention. It is the same as the embodiment in FIG. 2 except that a plurality of cooling structural members 9 are arranged in the longitudinal direction. In particular, if the cooling structural member 9 is provided in a portion where a large amount of heat is generated, effective cooling can be performed. In the present embodiment, the cooling structural member 9 is attached to the upper clamp 7,
The same cooling effect can be obtained by using the upper clamp 7 having the same structure as the cooling structural member 9 provided in advance.

FIG. 5 shows another embodiment of the present invention.
It is a sectional perspective view. In the embodiment shown in FIGS. 1 to 4, the cross-sectional shape of the iron core fastener is substantially L-shaped.
Is an example of an iron core clamp having a substantially U-shaped cross section. In this case, the upper core clamp 6 is 2
Although there are two horizontal plates, the cooling structural member 8 is attached to the upper horizontal plate. Although the cooling structural member 8 of this embodiment is the same as that of the embodiment of FIG. 1, the same effect can be obtained by using the cooling structural member 8 of the embodiment of FIGS. Further, in this embodiment, no special cooling structure is provided for the lower iron core fastening member 7, but a mesh cooling structural member 9 similar to the embodiment of FIG. 3 may be used.

Although the present invention has been described by taking a gas-insulated transformer as an example, the present invention is also effective when applied to an oil-filled transformer that generates a lot of heat.

[0026]

As described above, according to the present invention, a core member for mechanically holding a core of a transformer is provided with a thermally connected, thermally conductive structural member. By providing a part of the structural member so as to be substantially parallel to the vertical direction (the direction of gravity), much of the heat generated by the iron core clamp is transmitted to the structural member for cooling by heat conduction. By generating a relatively strong natural convection in the vertically projecting portion, the heat is efficiently removed, and the temperature rise of the iron core clamp can be reduced by about 35% as compared with a case where no cooling structural member is provided. effective.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view showing one embodiment of the present invention.

FIG. 2 is a sectional perspective view showing one embodiment of the present invention.

FIG. 3 is a sectional perspective view showing one embodiment of the present invention.

FIG. 4 is a sectional perspective view showing one embodiment of the present invention.

FIG. 5 is a sectional perspective view showing one embodiment of the present invention.

[Explanation of symbols]

1 ... iron core leg, 2 ... iron core outer leg, 3 ... yoke, 4 ... iron core stand, 5
... Insulating plate, 6 ... Upper core clamp, 7 ... Lower core clamp, 8 ... Cooling structural member, 9 ... Net cooling structural member.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshio Hamadate, Inventor 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Power & Electricity Development Division, Hitachi, Ltd. (72) Inventor Toshimitsu Obata Kokubuncho, Hitachi City, Ibaraki Prefecture 1-1-1, Kokubu Plant, Hitachi, Ltd. (72) Inventor Iwao Umene 1-1-1, Kokubuncho, Hitachi, Ibaraki, Japan

Claims (7)

[Claims] 1. A transformer core comprising an upper core and a lower iron core connected to an iron core leg for winding or a core outer leg for non-rotation by fastening an iron core of a yoke portion with an iron core fastening metal with an insulating plate interposed therebetween. In the transformer arranged in the tank, a structural member made of a material having thermal conductivity is provided by being thermally connected to a portion of the horizontal plate that protrudes in the horizontal direction in the iron core tightening fitting. A transformer. 2. The transformer according to claim 1, wherein said structural member comprises at least a portion parallel to the horizontal plate of said iron core fastening and a portion perpendicular thereto. 3. The transformer according to claim 1, wherein the cross-sectional shape of said structural member is substantially L-shaped or T-shaped. 4. The transformer according to claim 1, wherein said structural member is made of copper, aluminum or iron. 5. The transformer according to claim 1, wherein a plurality of said structural members are arranged in a longitudinal direction of the iron core clamp. 6. The transformer according to claim 1, wherein said structural member is formed of a net-like structure or a flat plate provided with a plurality of openings. 7. A transformer core formed by connecting an upper and lower yoke to an iron core leg for winding or a core outer leg not to be wound by tightening an iron core of a yoke portion with an iron core clamp with an insulating plate interposed therebetween. In the transformer arranged in the tank, in the direction substantially perpendicular from the horizontal plate overhanging in the horizontal direction,
A transformer characterized by using an iron core fastening fitting overhanging a thermally conductive structure.