EP0553175B1 - Dry transformer or choke coil and process for making it - Google Patents

Abstract

The invention relates to a dry transformer or a choke coil in which the winding conductors and/or winding layers and/or outer sheathing of at least one winding (2, 13) are insulated. Alternatively, at least one winding and the iron core (1, 11) with the windings (2, 13) can be entirely surrounded by ceramic resin (3). To produce the ceramic resin, a strong alkaline solution with sodium and/or potassium and/or calcium and/or lithium and a powder of silicate and aluminium is prepared. Alternatively, fibre rovings may be soaked in this solution and wound on the winding or the winding or the iron core with windings are put into a mould and this solution poured over it. This is followed by a curing process at a temperature of 70 to 100 °C. Curing may be followed by soaking in a fluid with good dielectric properties.

Description

The invention relates to a dry type transformer or an inductor, to a method for producing the winding of a dry type transformer or an inductor, to a method for producing a dry type transformer or an inductor, and to the use of ceramic material as insulation.

In electrical energy supply, dry-type transformers and dry choke coils are increasingly being used as distribution transformers or choke coils instead of conventional liquid-insulated devices, particularly because of the fire risks posed by liquid-insulated devices and the danger to soil and groundwater from liquids in the event of leaks or transport accidents.

For electrical insulation of the winding wires and layers, for external insulation and to protect the windings of dry-type transformers and dry choke coils against moisture and dirt, plastics are used, such as. B. epoxy, polyester, polyurethane or silicone resins. Cast resin transformers in which one or more windings are completely enclosed with an insulating material have proven to be particularly suitable. These cast resin transformers are therefore completely protected against the effects of moisture and pollution.

However, the plastics used for the electrical insulation of the dry transformers and dry choke coils also have certain disadvantages. In this way, these plastics can burn and develop smoke and toxic combustion gases in the event of a fire, which can endanger people and prevent extinguishing work. The plastics used age due to oxidation and hydrolysis. The chemical decomposition of the plastics is greatly accelerated at relatively high temperatures, which are in the range of the operating temperatures of transformers and choke coils. The mechanical and dielectric properties of the plastics used deteriorate significantly at these temperatures. At even higher temperatures, the plastics are thermally decomposed. Epoxy resins, which are mainly used because of their overall best property profile, are disadvantageously not resistant to UV light. Furthermore, the plastics used are sensitive to leakage currents, so that outdoor installation is only possible with complex protective housings. These protective housings are cost-intensive and disadvantageous due to the increase in weight and size of the transformers or the choke coils.

Problems also arise from possible destruction of the plastic insulation as a result of partial discharge. After hardening, the plastics used show shrinkage, which can lead to cavities and shrinkage stresses and later crack formation, which enables partial discharges.

When plastics are deposited at the end of their useful life, harmful decomposition products can get into the soil and groundwater as a result of the slowly progressing decomposition of the plastics.

In the manufacture of dry transformer coils and choke coils, casting processes and impregnation processes are used, which are often carried out under vacuum to avoid air pockets, or the roving winding process is used, in which glass fiber rovings are impregnated with epoxy resin and applied to the individual winding layers and / or be wound on the spools.

The invention has for its object to provide a dry transformer or a dry inductor, which are provided with an environmentally friendly, aging-resistant insulation and protective material with favorable fire behavior. Furthermore, methods for producing a dry transformer or a dry choke coil and their winding are to be mentioned. In addition, appropriate uses of ceramic material dry transformers and dry inductors should be mentioned.

With regard to the dry-type transformer and the inductor, this object is alternatively achieved by the Characteristics solved in claim 1, according to which the winding conductors and / or winding insulation layers and / or the outer jacket of at least one winding of a dry transformer or a choke coil are insulated with ceramic material.

The object relating to the method for producing a winding of a dry transformer and a choke coil is alternatively achieved by the features characterized in claims 13, 17, 18 and 19.

A preferred solution with regard to the method for producing the winding of a dry-type transformer or a choke coil is that the inner lateral surface of the winding is first produced by fiber rovings with a mixture of a strongly alkaline solution with sodium and / or potassium and / or Calcium and / or lithium ions and a powder of silicate and aluminum are soaked and wound on a mold that the winding conductors are then wound up and further insulation is applied, and that preferably the winding thus prepared is subsequently heated to a temperature of 70 to 100 ° C is heated to harden the ceramic material. The curing can alternatively also be carried out at room temperatures or temperatures higher than 100 ° C.

As an alternative to the winding process, it is also possible to cast at least one winding in the mold with said mixture or, after winding with winding conductors and necessary further insulation, to soak them in a plunge pool and then to carry out the hardening process. It is also possible to impregnate fiber rovings with said mixture and onto it Winding to wrap. In this way, several windings of a transformer can be separated or isolated together. It is also possible to insulate the winding wires and layers with synthetic resin and the outer sheath with ceramic material.

The object is achieved with respect to the method for producing a dry transformer or a dry inductor alternatively by the features characterized in claim 20 or 21, according to which the windings are separated or together or at least one winding together with an iron core in a form with a mixture of a strong alkaline solution with sodium and / or potassium and / or calcium and / or lithium ions and a powder of silicate and aluminum or alternatively the windings are separated or together or the entire active part is soaked in a plunge pool with said mixture. The ceramic material is then hardened at room temperatures or temperatures of 70 to 100 ° C.

Furthermore, the use of ceramic material as an insulating and protective material for the windings or windings and iron core of dry transformers or dry choke coils is proposed according to the invention.

The advantages that can be achieved with the invention are, in particular, that the ceramic material, depending on the composition, has a temperature resistance between 700 ° C. and 1200 ° C. and is not degraded by oxidation and hydrolysis. It is therefore possible to increase the operating temperatures of transformers and choke coils compared to the previous state of the art.

This reduces the weight and dimensions of the dry-type transformer or choke coil, which is of great importance for a large number of applications, particularly in the case of transformers and choke coils for electrically operated vehicles, such as locomotives, on oil drilling platforms and when mounted on masts.

The ceramic material is non-flammable and therefore offers the greatest advantages in all cases in which transformers or choke coils pose fire risks. It is even advantageously possible to continue to operate the transformers and choke coils for a certain time after being involved in a fire due to the very high temperature resistance of the ceramic material, in order to maintain the electrical energy supply in a dangerous situation.

Ceramic material is an environmentally friendly material, from which no hazardous substances are released even after the end of its useful life when it is landfilled.

Ceramic material is resistant to leakage current and UV light so that it can be used outdoors when the devices are installed outdoors, without the need to use expensive protective housings.

Depending on the composition of the ceramic material, the shrinkage during hardening and the thermal expansion can be kept very low, which means that components with high dimensional accuracy can be produced, as well as shrinkage stresses and cavities are avoided, which prevents partial discharges during operation.

The relatively low hardening temperatures and the relatively short hardening times save energy costs during production.

The aforementioned high temperature resistance makes it possible to completely encapsulate the winding and the core, even in the case of transformers or choke coils of higher powers, and to reduce the cooling surface. This optimizes the protection of the winding and core parts against harmful environmental influences - especially moisture. In this regard, the relatively high thermal conductivity that can be achieved, depending on the composition of the ceramic material, is also favorable, because this reduces the build-up of high internal temperatures and temperature differences during operation.

Advantageous developments of the invention are characterized in the dependent claims.

Fig. 1.1

ein Trockentransformatorteil mit einer mit keramischem Material isolierten Wicklung,

Fig. 1.2

ein Drosselspulenteil mit einer mit keramischem Material isolierten Wicklung,

Fig. 2

ein Trockentransformatorteil mit einer vollständig in keramischem Material eingekapselten Wicklung,

Fig. 3

ein Trockentransformatorteil mit einer vollständig in keramischem Material einkapselten ersten Wicklung und einer gemeinsam mit dem Eisenkern eingekapselten zweiten Wicklung,

Fig. 4

ein Trockentransformatorteil mit zwei vollständig in keramischem Material eingekapselten Wicklungen,

Fig. 5

ein Trockentransformatorteil mit zwei mit dem Eisenkern gemeinsam mit keramischem Material eingekapselten Wicklungen,

Fig. 6

ein Trockentransformatorwicklungsteil Isolation aus keramischem Material,

Fig. 7

ein Trockentransformatorwicklungsteil mit Drahtisolation aus keramischem Material

The invention is explained below with reference to the embodiments shown in the drawing.
Show it:

Fig. 1.1

a dry transformer part with a winding insulated with ceramic material,

Fig. 1.2

a choke coil part with a winding insulated with ceramic material,

Fig. 2

a dry transformer part with a winding completely encapsulated in ceramic material,

Fig. 3

a dry transformer part with a first winding completely encapsulated in ceramic material and a second winding encapsulated together with the iron core,

Fig. 4

a dry transformer part with two windings completely encapsulated in ceramic material,

Fig. 5

a dry transformer part with two windings encapsulated with the iron core together with ceramic material,

Fig. 6

a dry transformer winding part insulation made of ceramic material,

Fig. 7

a dry transformer winding part with wire insulation made of ceramic material

According to a first variant, FIG. 1.1 shows a dry transformer part and in FIG. 1.2 a variant of a choke coil part each with a winding insulated with ceramic material. An iron core 1, a first winding 2 and a second winding 4 can be seen in FIG. 1.1. 1.2 shows an iron core 11 with air gaps 12 and a choke coil winding 13, the so-called air gaps 12 being formed with a non-ferromagnetic material.

The outer lateral surfaces of the first winding 2 and the winding 13 are insulated with ceramic material 3. This outer insulation is preferably produced according to the roving winding process, in the case of glass fiber rovings or rovings of other fiber materials are soaked with the solution described below and contains a powder of silicate and aluminum and are wound onto the spools. This is followed by the curing process described below at room temperature or elevated temperature. It is possible to insulate the outer lateral surface of the second winding 4 with ceramic material in the same way as the outer surface of the winding 2. It is also possible to use ceramic material for the so-called air gaps 12, the material being reinforced by mixing in glass fibers can.

According to a second variant, FIG. 2 shows a dry transformer part with a winding completely encapsulated in ceramic material. An iron core 1, a first winding 2, a second winding 4 and ceramic material 3 can be seen, the ceramic material 3 completely enclosing the first winding 2. For encapsulation, the winding 2 is brought into an appropriately designed shape and cast with the solution described below, containing a powder of silicate and aluminum.

Accordingly, this variant can also be applied to dry choke coils, in which case air gaps in the iron core 11 and only one winding 13 are provided. To avoid cavities, the casting process can be carried out using a vacuum. This is followed by the curing process described in more detail below at room temperature or elevated temperature. It is possible to completely encapsulate the outer surface of the second winding 4 with ceramic material in the same way as the outer surface of the first winding 2. The same method can also be applied to the winding 13 of a choke coil.

For the variant of a dry transformer part shown in FIG. 2 with a winding completely encapsulated in ceramic material, further alternative production methods are specified below.

In the first further production process, the inner lateral surface 5 (FIG. 2) is first produced in accordance with the roving winding process, in which the glass fiber rovings or other fiber rovings are impregnated with the strongly alkaline solution described below and containing a powder of silicate and aluminum and to a suitable shape be wrapped. The winding conductors and necessary further insulations are wound onto the inner surface thus created, the further insulations also being produced using the roving winding method. Either the fiber rovings are soaked with the strongly alkaline solution described below, containing a powder of silicate and aluminum, or alternatively with a liquid plastic material (synthetic resin). After the winding of the winding conductors has been completed, the outer insulation is produced, in the same way as shown above in the description of FIG. 1. This is followed by the hardening process described below. The same method can be applied to the winding 13 of a choke coil.

In the second further production method, the winding of a dry transformer or a choke coil is immersed in a plunge pool after the winding of the winding conductors and necessary further insulation contains the strongly alkaline solution described below, including the powder made of silicate and aluminum. This creates a coating on all sides that adheres to the outer jacket surfaces in one layer after the winding is pulled out of the plunge pool and also soaks the inner insulation. To reinforce the outer jacket surfaces, fiber mats, fiber fabrics or similar fiber materials can be applied here before the impregnation process. The impregnation process can preferably be carried out under vacuum in order to avoid air pockets. The curing process described below follows the impregnation process.

It is possible to treat the second winding 4 in the same way using the two further methods.

According to a third variant, FIG. 3 shows a dry transformer part with a first winding completely encapsulated in ceramic material and a second winding encapsulated together with the iron core. An iron core 1, a first winding 2, a second winding 4 and ceramic material 3 can be seen, the ceramic material 3 completely enclosing both the winding 2 and the winding 4 together with the iron core 1. In the case of a choke coil, the second winding 4 is omitted and the iron core 1 is designed with so-called air gaps. The encapsulation is carried out as described in FIG. 2, the iron core being brought together with the winding 4 into an appropriately designed shape in order to carry out the casting process, preferably using a vacuum. It is also possible to apply the method to the winding and the core of a choke coil, the material for the so-called air gaps being introduced in the same casting process can be. The second winding 4 can be isolated and encapsulated according to one of the further methods described in FIGS. 1 and 2, the iron core outer surface denoted by numeral 6 in FIG. 3 serving as a form for forming the inner jacket surface 5.

According to a fourth variant, FIG. 4 shows a dry transformer part with windings which together are completely encapsulated in ceramic material. An iron core 1 and two windings 2 and 4 with ceramic material 3 can be seen, the ceramic material 3 completely enclosing both windings. the encapsulation is carried out according to a method described in FIG. 2, the windings 2, 4 either being brought together into a correspondingly shaped form and potted or soaked together in the immersion process or co-processed in the roving winding process - preferably using a vacuum.

According to a fifth variant, FIG. 5 shows a dry transformer part with two windings encapsulated with the iron core together with ceramic material. An iron core 1, windings 2 and 4 and ceramic material 3 can be seen, the ceramic material 3 completely enclosing both the windings 2 and 4 and the iron core. The encapsulation is carried out either by the casting process, in which the iron core is brought into an appropriately designed shape together with all the windings, or by the impregnation process, in which the iron core is immersed in a drinking basin together with all the windings. Both methods are described in Figure 2 and are preferably carried out under vacuum.

FIG. 6 shows a dry transformer winding part or choke coil winding part with layer insulation and encapsulation made of ceramic material. The winding conductors 7, the outer insulation or encapsulation 8 and the inner layer insulation 9 (inner winding insulation layers) can be seen. The inner winding insulation layers 9, like the outer insulation 8, are produced using a method described in FIGS. 1 to 5 with ceramic material.

FIG. 7 shows a dry transformer winding part or choke coil winding part with layer and wire insulation made of ceramic material. The winding conductors 7 and the insulation 10 made of ceramic material can be seen. It is clarified that not only the inner winding layers g according to FIG. 6, but also the insulation from winding conductor to winding conductor can be produced with a ceramic material using a method described in FIGS. 1 to 5.

FIGS. 6 and 7 show winding conductors 7 with a round cross section. Alternatively, winding conductors with a rectangular cross section can be used.

The ceramic material used is an alumino-silicate-based ceramic material with a silicon-aluminum atom ratio, preferably between 2 and 4 (equilibrium ratio 2.07 to 4.14). To produce the ceramic material, a fine powder of aluminum and silicate is placed in a strongly alkaline solution that contains sodium, potassium, calcium or lithium ions or a combination of all these elements. The grain sizes used are preferably between 0.25 µm and 1 µm. The solution is one Liquid with a viscosity between approx. 500 and 300 mPas.

At room temperature or by heating the solution provided with the powder of aluminum and silicate to temperatures of preferably 70 to 100 ° C, an exothermic reaction is triggered, accompanied by polycondensation of the ceramic molecules. This is based on the merger of ALO₄ and SiO₄ tetrahedra, whereby the metallic ions of the solution are included in the structure as a charge balance. The combination of the molecules creates a 3-dimensional structure, which remains completely disordered, so that the resulting material is amorphous.

The heating up period is essentially determined by the dimension of the component, the material being able to cure in principle at different temperature gradients. The curing time for 0.1 mm thick films at 70 ° C is approx. 30 min, for 1 cm thick blocks at the same temperature approx. 3 hours. Hardening is also possible at room temperature, but the time required for this is on the order of days, again depending on the geometry.

The reaction produces water as a condensation product, which is removed from the material by heating for several hours at temperatures above 50 ° C. This drying is an important time factor, as it is much slower than hardening, especially for large components. The heating speed also plays an important role here, since if the heating is too fast, cracks may occur in the material. The resulting ceramic material has ceramic properties regarding high temperature strength, chemical stability, hardness, fracture toughness and electrical properties. The material properties - in particular the mechanical strength - can also be influenced by reinforcing the ceramic material with various fiber materials or fillers. In particular, glass fibers and / or mineral fillers can be used.

Ceramic material can be completely sealed with a ceramic-like glaze on its surface or with a thin coating of another water-impermeable material. Liquids with favorable dielectric properties such as. B. a silicone-containing emulsion, for impregnating the ceramic material and thus to increase the dielectric strength of the material, and a silicone-containing lacquer for the outer coating of the material.

Claims (35)

1. Dry-type transformer or reactance coil having an iron core, at least one winding having winding conductors, an outer circumferential surface and an insulation, characterised in that a ceramic material based on aluminium silicate is provided as insulation.
2. Dry-type transformer or reactance coil according to Claim 1, the outer circumferential surface of at least one winding (2, 13) being insulated with the ceramic material (3).
3. Dry-type transformer or reactance coil according to Claim 2, at least one winding (2, 13) being completely enclosed by the ceramic material (3).
4. Dry-type transformer or reactance coil according to Claim 3, both the iron core (1, 11) and at least one winding (2, 13) being completely enclosed by the ceramic material (3).
5. Dry-type transformer or reactance coil according to Claim 1, the winding conductors (7) of at least one winding being insulated with the ceramic material (10).
6. Dry-type transformer or reactance coil according to Claim 1, the inner winding-insulation layers (9) and the outer insulation (8) comprising of at least one winding of the ceramic material.
7. Dry-type transformer or reactance coil according to one of Claims 1 to 6, the ceramic material having the grouping-together of AlO₄ and SiO₄ tetrahedrons.
8. Dry-type transformer or reactance coil according to one of Claims 1 to 7, the surfaces of the ceramic material being at least partially sealed with a ceramic-like glazing, as is customary in ceramics.
9. Dry-type transformer or reactance coil according to one of Claims 1 to 7, the surface of the ceramic material being at least partially sealed with a water-impermeable material.
10. Dry-type transformer or reactance coil according to Claim 9, characterised by the use of a silicone-containing lacquer for the outer coating of the ceramic material.
11. Dry-type transformer or reactance coil according to Claim 9, characterised by the use of a silicone-containing emulsion for impregnating the ceramic material.
12. Dry-type transformer or reactance coil according to one of Claims 1 to 7, the ceramic material used being entirely or partially impregnated with a liquid having favourable dielectric properties, such as epoxy resin or silicone resin.
13. Process for the production of a winding of a dry-type transformer or of a reactance coil, characterised in that, first of all, the inner circumferential surface (5) of the winding is produced by fibre rovings being impregnated with a strongly alkaline solution with sodium and/or potassium and/or calcium and/or lithium ions as well as a powder of silicate and aluminium and wound onto a form, in that subsequently the winding conductors are wound on and further insulations are applied.
14. Process according to Claim 13, the further insulations being likewise produced by using fibre rovings.
15. Process according to Claim 14, the fibre rovings being likewise impregnated with a strongly alkaline solution with sodium and/or potassium and/or calcium and/or lithium ions as well as a powder of silicate and aluminium.
16. Process according to Claim 14, the fibre rovings being additionally impregnated with a liquid synthetic resin such as epoxy resin or silicone resin.
17. Process for the production of a winding of a dry-type transformer or of a reactance coil, characterised in that, after winding with winding conductors and necessary further insulation, the winding are [sic] impregnated in a dip tank with a strongly alkaline solution with sodium and/or potassium and/or calcium and/or lithium ions as well as a powder of silicate and aluminium.
18. Process for the production of a winding of a dry-type transformer or of a reactance coil, characterised in that fibre rovings are impregnated with a strongly alkaline solution with sodium and/or potassium and/or calcium and/or lithium ions as well as a powder of silicate and aluminium and are wound onto the winding (2, 3).
19. Process for the production of at least one winding of a dry-type transformer or of a reactance coil, characterised in that at least one winding, situated in a mould, are [sic] cast with a strongly alkaline solution with sodium and/or potassium and/or calcium and/or lithium ions as well as a powder of silicate and aluminium.
20. Process for the production of a dry-type transformer or of a reactance coil, characterised in that at least one winding (2, 13), situated together with an iron core (1, 11) in a mould, is cast with a strongly alkaline solution with sodium and/or potassium and/or calcium and/or lithium ions as well as a powder of silicate and aluminium.
21. Process for the production of a dry-type transformer or of a reactance coil, characterised in that at least one winding (2, 13) is impregnated together with an iron core (1) in a dip tank with a strongly alkaline solution with sodium and/or potassium and/or calcium and/or lithium ions as well as a powder of silicate and aluminium.
22. Process according to at least one of Claims 13 to 21, the silicate/aluminium atomic ratio being between 2 and 4.
23. Process according to one of Claims 13 to 21, characterised in that the particle size of the powder is 0.25µm to 1µm.
24. Process according to at least one of Claims 13 to 23, the windings or the windings with iron core or the transformer being successively heated to a temperature of 70 to 100°C.
25. Process according to at least one of Claims 13 to 24, characterised by the application of a vacuum in the case of winding, pouring or impregnating.
26. Process according to at least one of Claims 13 to 25, the solution being additionally provided with fibres, preferably glass fibres.
27. Process according to at least one of Claims 13 to 26, the solution being additionally provided with fillers, preferably mineral fillers.
28. Process according to at least one of Claims 13 to 27, the water produced during the curing reaction being driven out by heating over hours to temperatures above 50°C.
29. Process according to at least one of Claims 13 to 28, the ceramic material being impregnated after curing by dipping at least one winding into a dip tank with a liquid having favourable dielectric properties.
30. Process according to at least one of Claims 13 to 29, the ceramic material being impregnated after curing by dipping at least one winding together with the iron core into a dip tank with a liquid having favourable dielectric properties.
31. Process according to at least one of Claims 29 and 30, the impregnating agent or the components to be impregnated being heated to temperatures above 30°C.
32. Process according to at least one of Claims 29 and 30, the impregnating agent and the components to be impregnated being heated to temperatures above 30°C.
33. Process according to at least one of Claims 29 to 32, a vacuum being applied during the impregnating operation.
34. Use of ceramic material based on Al-Si as insulating and/or protecting material for the windings of dry-type transformers and reactance coils.
35. Use of ceramic material based on Al-Si as insulating and/or protecting material for the windings and the iron core of dry-type transformers and reactance coils.

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