Electric transformer for high- and very high-intensity currents, particularly for furnaces and rectifiers

Abstract

 An electric transformer for high- and very high-intensity currents, particularly for furnaces and rectifiers, comprising a tank (2) which contains a magnetic core (3) with the corresponding windings (4,5). The low-voltage feedthroughs for high- and very high-intensity currents protrude hermetically from the tank (2). The particularity of the invention is constituted by the fact that at least the portion of the wall of the tank that is affected by the low-voltage feedthroughs is made of aluminum and/or alloys thereof and forms openings for the hermetic passage of the low-voltage feedthroughs.

Description

[0001] The present invention relates to an electric transformer for high- and very high-intensity currents, particularly for furnaces and rectifiers.

[0002] It is known that the walls of the tanks of electric transformers for high- and very high-intensity currents must be provided with openings for the passage of low-voltage feedthroughs, which are affected by high and very high currents, i.e., above 10,000 amperes.

[0003] Present solutions entail providing a hermetic closure of the tank at the low-voltage feedthroughs by means of a fiber-reinforced plastic body which must have a high mechanical strength in order to withstand the internal pressures produced by the transformer cooling oil.

[0004] These fiber-reinforced plastic closures can be 40-50 mm thick and accordingly are very complicated and expensive to manufacture.

[0005] Additionally, there are also considerable magnetic problems when using electrically insulating material, since the magnetic fluxes that originate from inside the transformer escape through the tank, heating it.

[0006] In order to try to contain these fluxes, which inevitably constitute a loss, special diamagnetic steels are produced, with high production costs, and it is also necessary to reinforce the shielding with bars so as to reduce losses due to heating on the tank.

[0007] In the present situation, therefore, there are , during the operations, considerable losses combined with very high costs for manufacturing the tank with diamagnetic steels and for the corresponding shielding that must be used.

[0008] The aim of the present invention is to eliminate the above drawbacks, by providing an electric transformer for high- and very high-intensity currents, particularly for furnaces and rectifiers, which allows to provide the hermetic closure of the tank of the transformer particularly in the region where the low-voltage feedthroughs pass but without thereby producing a passage of magnetic fluxes which would lead to the above-described drawbacks.

[0009] Within the scope of this aim, a particular object of the present invention is to provide a transformer in which, by virtue of the solutions used, it is possible to provide the tank by using normal steel, without having to resort to shielding provided by means of bars, thus reducing the total weight of the tank and accordingly its cost.

[0010] Another object of the present invention is to provide a transformer tank which, by not being affected by the passage of magnetic fluxes, is not subjected to wear or damage over time.

[0011] Another object of the present invention is to provide an electric transformer for high- and very high-intensity currents with magnetic field containment means which, by virtue of its particular constructive characteristics, is capable of giving the greatest assurances of reliability and safety in use and is furthermore competitive from a purely economical point of view.

[0012] This aim, these objects and others which will become apparent hereinafter are achieved by an electric transformer for high- and very high-intensity currents, particularly for furnaces and rectifiers, according to the invention, which comprises a tank containing a magnetic core with the corresponding windings, low-voltage feedthroughs for high- and very high-intensity currents protruding hermetically from said tank, characterized in that at least the portion of the wall of said tank that is affected by said low-voltage feedthroughs is made of aluminum and/or alloys thereof and forms openings for the hermetic passage of said low-voltage feedthroughs.

[0013] Further characteristics and advantages of the present invention will become apparent from the following detailed description of a preferred but not exclusive embodiment of an electric transformer for high- and very high-intensity currents, particularly for furnaces and rectifiers, illustrated only by way of non-limitative example in the accompanying drawings, wherein:

• Figure 1 is a schematic sectional view of an electric transformer to which an aluminum plate is applied to the wall from which the low-voltage feedthroughs exit;
• Figure 2 is a schematic front view of the aluminum plate;
• Figure 3 is a schematic perspective view of the insulating collar for the passage of the low-voltage feedthroughs;
• Figure 4 is a schematic sectional view of the plate with a low-voltage feedthrough, illustrating two different fixing elements.

[0014] With reference to the above figures, the electric transformer for high- and very high-intensity currents, particularly for furnaces and rectifiers, generally designated by the reference numeral 1, comprises a tank 2 which has a substantially conventional configuration and contains a magnetic core 3 which is itself also of known type and in which high- and low-voltage windings are provided, designated by the reference numerals 4 and 5.

[0015] The relevant characteristic of the invention is constituted by the fact that at least one portion of wall of the tank 2 has an aperture 10 which is closed by a plate 11 made of aluminum or alloys thereof and in practice forms the region of the low-voltage feedthroughs through which high and very high current flows.

[0016] The aluminum plate 11 can affect the entire wall and can have openings 12 provided directly therein, as shown in Figure 2, or it is optionally conceptually possible to provide, at the openings for the passage of the low-voltage feedthroughs, aluminum closure elements to which the low-voltage feedthroughs are connected hermetically and by means of the corresponding electrical insulation.

[0017] The low-voltage feedthroughs, schematically designated by the reference numeral 20, are connected to the plate 11 by interposing a collar 15 which is made of electrically insulating material, such as synthetic rubber or silicone rubber or optionally fiber glass.

[0018] The collar 15, as shown in Figure 3, has a flange-like portion 16 from which a ring 17 protrudes surrounding the region affected by the low-voltage feedthrough 20.

[0019] Holes 18 are provided on the flange-like portion 16 for the insertion of locking screws 30, which can be metallic and therefore provided with bushings 31 which provide insulation with respect to the plate 11 or can optionally be provided by means of electrically insulating screws 32, as shown in Figure 4.

[0020] The flange-like portion 16 further forms a groove 19 in which a gasket engages for providing a seal with respect to the plate 11.

[0021] The adoption of the aluminum plate 11, which affects the entire wall or optionally only the region of the openings, in practice prevents the passage of magnetic fluxes through the tank of the transformer, consequently eliminating the problem of heating the wall of the tank, which can be made of ordinary steel, without having to also apply bars to form shielding.

[0022] The adopted solution, i.e., the use of an aluminum portion at the region where the low-voltage feedthroughs pass, allows to drastically reduce operating losses, to save on labor and materials and to avoid having to provide shielding.

[0023] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

[0024] All the details may also be replaced with other technically equivalent elements.

[0025] In practice, the materials employed, as well as the contingent shapes and dimensions, may be any according to requirements.

Claims

1. Electric transformer for high- and very high-intensity currents, comprising a tank which contains a magnetic core with the corresponding windings, low-voltage feedthroughs for high- and very high-intensity currents protruding hermetically from said tank, characterized in that at least the portion of the wall of said tank that is affected by said low-voltage feedthroughs is made of aluminum and/or alloys thereof and forms openings for the hermetic passage of said low-voltage feedthroughs.

2. Electric transformer according to claim 1, characterized in that said tank has an aperture at which it is possible to apply a plate made of aluminum and alloys thereof which forms said openings.

3. Electric transformer according to claims 1 and 2, characterized in that it comprises an aluminum plate at each opening for the passage of said low-voltage feedthroughs formed on the tank of said transformer.

4. Electric transformer according to one or more of the previous claims, characterized in that said low-voltage feedthroughs are connected to said plate made of aluminum and/or alloys thereof by interposing a collar made of electrically insulating material.

5. Electric transformer according to one or more of the previous claims, characterized in that said collar has a flange for connecting screws for locking the low-voltage feedthrough to said plate while maintaining electrical insulation.

Drawing