JPH09115740A - Iron core clamp for transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the stray loss of the iron core of a transformer caused by eddy currents generated on the clamp of the core by constituting the clamp of a high-strength insulating material. SOLUTION: The main structure of an iron core clamp which has been made of steel is made of such a high-strength insulating material 1 as a thick FRP, etc. In addition, insulating magnetic bodies 2, such as ferrite bodies, etc., are buried in the material 1 so that the bodies 1 can absorb magnetic fluxes. Even when the magnetic bodies 2 are concentrated to the part of the material 1 which comes into contact with the top part of windings, the bodies 2 exert sufficiently high effects. In addition, the clamp is made to have a periodical structure in the length direction. A plurality of kinds of longer molds is prepared and the material 1 manufactured by using the molds is cut into an arbitrary length. Therefore, the eddy currents which have been generated on the iron core clamp by leakage magnetic fluxes from the gap between the windings of a power transformer can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a power transformer, and more particularly to a structure in which an iron core fastener is attached to an iron core and the iron core fastener is made of an insulating material.

[0002]

2. Description of the Related Art In recent years, there has been a demand for a review of the entire power transmission system in response to the needs for increasing the capacity of the power transmission system. In particular, with respect to the power demand in large cities, which is increasing year by year, substations are being installed in various places inside the big cities, and the system is being changed to a method of distributing the demand. In this way, when a new substation is installed inside a large city, from the viewpoint of land use efficiency, it is not possible to provide a vast site like a substation that has been conventionally installed in mountainous areas, and buildings, parks, etc. It is required to be installed in a narrow space underground. Therefore, urban substations, for which demand will increase rapidly in the future, are underground substations, and the following requirements are imposed on the equipment.

The first point is miniaturization. Underground substations should be sized so that they fit into a section of an already overcrowded city and that the installation procedure is taken into consideration. The second point is incombustibility. The possibility of transformer fire due to insulation breakdown is a more serious problem in densely populated areas than in the past.

However, these two requirements are conflicting with the transformer design. First of all, the miniaturization of the device necessarily brings the structures close together. As a result, the winding and the conductive magnetic material structure such as the iron core clamps that have been installed apart from each other come closer to each other, and the eddy current is easily generated in the structure due to the magnetic flux leaking from the winding gap. . This increases heat generation. Further, due to the demand for non-combustion, it is required to switch from the conventional insulation / cooling using oil to insulation / cooling using non-combustible gas. However, if a non-combustible gas is used, the cooling capacity will decrease due to the difference in heat capacity. Thus, these two requirements simultaneously bring about the problems of increased heat generation and reduced cooling capacity. Gas insulated transformers for underground substations are required to have new means to solve such problems.

Even conventional oil-based transformers have UHV
Since such an ultra-high capacity transformer has a large eddy current to be driven, new means for solving such a problem is required as in the case of the gas insulated transformer for the underground substation.

Most of the power transformers are of the inner iron type having an iron core inside the winding, and adopt a concentric arrangement in which the primary winding and the secondary winding are concentrically arranged in one iron core. Since a potential difference corresponding to a boost is generated between the primary winding and the secondary winding, a winding gap is provided for insulation. The magnetic flux leaking from the winding gap causes an eddy current in the iron core fastener and the tank.

Conventionally, as a means for reducing the eddy current generated in the iron core fastening member by the magnetic flux leaking from the winding gap, as disclosed in Japanese Patent Laid-Open No. 122204/1987, a copper plate or the like is inserted in the portion where the magnetic flux enters. The low resistance material shield was attached, and an eddy current was generated on the shield to create a demagnetizing field, and magnetic flux was prevented from entering the high resistance member made of iron to reduce heat generation by the eddy current. Although such a means is effective in locally suppressing the eddy current at the part where the magnetic flux directly penetrates, some loss occurs on the shield, and the magnetic field bent by the demagnetizing field eventually results in the tank. As a result, the stray loss due to the new eddy currents is attracted to the etc., so that there is little effect in reducing the stray loss as a whole.

As a second means, Japanese Patent Laid-Open No. 63-276208
As described in the publication, a silicon steel plate was attached to the surface of the iron core fastener to induce as much magnetic flux as possible in the iron core. However, in this method, the magnetic flux that has passed through the silicon steel plate also penetrates into the iron core fastener, so that an eddy current is also generated on the surface of the iron core fastener. Therefore, it was still ineffective in reducing stray loss.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to gas insulation and
It is an object to suppress stray loss due to eddy currents on iron core fastenings, which is a problem in cooling transformers and UHV ultra large capacity transformers.

[0010]

The above-mentioned problems can be solved by the following means.

The iron core fasteners that were conventionally made of steel are
The main structure is made using a high strength insulating material such as RP. Furthermore, an insulating magnetic material such as ferrite is embedded so that the magnetic flux can be absorbed. As described above, the iron core fastener is formed of the composite material in which the high-strength insulating material and the insulating magnetic material are combined.

The operation of the present invention will be described with reference to FIGS.

FIG. 2 is a perspective view of a typical conventional power transformer. As shown in FIG. 2, the iron core fasteners are attached to the upper and lower portions of the winding so as to sandwich the iron core. The main role of the iron core fastener is to crimp and fix the iron core drawn up by laminated steel plates. FIG. 3 is a sectional view of a conventional typical power transformer. A part of the magnetic flux leaked from the winding gap between the low-voltage winding and the high-voltage winding is sucked into the iron core fastening member, which is a magnetic body, enters the iron core, penetrates the iron core leg, and returns to the winding gap again. In this way, the iron core fastening member not only serves as a structural material for crimping and fixing the iron core, but also serves as a magnetic flux guide that attracts the leakage magnetic flux and passes it to the iron core. The reason why it is necessary to suck the leakage magnetic flux and pass it to the iron core is that the power transformer is usually housed in an oil cooling tank made of iron as shown in FIG. If the leakage magnetic flux is not attracted to the iron core side as much as possible, the eddy current generated on the tank increases.

Since the conventional iron core fastener is made of steel, an eddy current is generated on the surface when the eddy current is attracted. This eddy current was the main cause of transformer stray loss along with the eddy current flowing in the tank.

In the present invention, as shown in FIG.
The main structure is made using a high strength insulating material such as P. Furthermore, an insulating magnetic material such as ferrite is embedded so that the magnetic flux can be absorbed. As described above, the iron core fastener is formed of the composite material in which the high-strength insulating material and the insulating magnetic material are combined. As a result, an eddy current does not flow, and as shown in FIG. 5, it is possible to provide an iron core fastener that also acts as a magnetic flux guide that attracts leakage magnetic flux and passes it to the iron core.

[0016]

The first embodiment of the present invention is the system of FIG. 1 used in describing the means of the present invention. FIG. 6 shows an example in which the present embodiment is applied to a three-phase five-leg transformer for electric power.

The second embodiment of the present invention is a gas cooling / insulation transformer shown in FIG. Gas cooling / insulation transformers are often installed in the basement of buildings, etc., and therefore are required to be compact. Due to the miniaturization, the winding and the iron core fastening member come close to each other, and an eddy current is easily generated by the magnetic flux leaking from the winding gap. Further, when a non-combustible gas is used, the cooling capacity is lowered due to the difference in heat capacity, so the eddy current heat generation of the internal structure is more serious. Gas insulated transformers for underground substations are required to have new means to solve such problems.

It is considered that the insulating magnetic material used in the present invention exerts a sufficient effect only by concentrating the insulating magnetic material in the portion that contacts the upper portion of the winding. FIG. 8 shows an embodiment in which the insulating magnetic material is arranged only on the upper part of the winding. By doing so, the cost can be reduced when an expensive material such as ferrite is used as the insulating magnetic body.

Ferrite is the first candidate for the insulating magnetic material, but since the present invention is used in the commercial frequency band,
It is not necessary to use high quality ferrite as used for electromagnetic wave shielding. Inexpensive ferrite is sufficient because it needs to have sufficient magnetic permeability for the dynamic magnetic field in the commercial frequency band.

A main structure made of a high-strength insulating material such as FRP requires a mold at the time of manufacture. In the case of a power transformer that is not a mass-produced product, there is a problem that it is difficult to reduce the cost because the cost of making the mold is large. This point is solved by the following method.

In the power transformer, since the transformer capacity and the transformer value differ depending on the power system, the size of the transformer varies. But it is the winding radius that depends directly on them,
The iron core fasteners only change in length. Therefore, the iron core fastener of the present invention has a periodic structure in the length method as shown in FIG. As for the mold, several kinds of long ones are made, and the high-strength insulating material produced using this is cut into an arbitrary length and used. By doing so, the cost of producing the mold can be suppressed.

[0022]

EFFECTS OF THE INVENTION By using the iron core fastener according to the present invention, it is possible to suppress the eddy current on the iron core fastener generated by the leakage flux from the winding gap in the power transformer, so that the heat generation of the equipment can be suppressed. Reduce losses. In particular, by reducing heat generation in a gas cooling / insulation transformer for an underground substation, for which demand will rapidly increase in the future, it is possible to reduce the load of the cooling system, which has been difficult in the past.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a conventional iron core fastener of a transformer.

FIG. 3 is a cross-sectional view showing the flow of magnetic flux in the vicinity of a conventional iron core fastener of a transformer.

FIG. 4 is a perspective view showing a conventional iron core fastening member and a tank of a transformer.

FIG. 5 is a sectional view showing the flow of magnetic flux in the vicinity of the iron core fastener of the present invention of the transformer.

FIG. 6 is a perspective view showing an iron core fastener of the present invention for a transformer.

FIG. 7 is a perspective view showing an iron core fastener of the present invention for a transformer.

FIG. 8 is a perspective view showing an iron core fastener of the present invention for a transformer.

[Explanation of symbols]

 1 ... High-strength insulating material, 2 ... Insulating magnetic material.

Claims (9)

[Claims] 1. A low voltage winding and a high voltage winding, which are electrically independent of each other,
A transformer iron core fastener, comprising: an iron core and a fastener for restraining the iron core, wherein the fastener for restraining the iron core is made of an insulating material. 2. The transformer core fastener according to claim 1, wherein an insulating magnetic material is added. 3. The transformer core fastener according to claim 1, wherein FRP is used as an insulating material to constitute the transformer iron core fastener. 4. The transformer core fastener according to claim 2, wherein ferrite is used as the insulating magnetic body. 5. A transformer using the iron core fastener according to claim 1. 6. The iron core fastener according to claim 1, wherein an insulating magnetic material is concentratedly arranged in a portion located near the winding. 7. A transformer using the iron core fastener according to claim 6. 8. The transformer core fastener according to claim 1, claim 2, claim 3 or claim 4, which has a periodic structure in the longitudinal direction. 9. The method for manufacturing a transformer iron core fastener according to claim 8, wherein the iron core fastener manufactured by using one mold is cut into an appropriate length, and the iron core fastener according to each specification is provided.