EP1514338A1

EP1514338A1 - Corona shield

Info

Publication number: EP1514338A1
Application number: EP03759826A
Authority: EP
Inventors: Bernhard Klaussner; Christoph Meyer; Volker Muhrer; Alexander MÄURER; Christian Rüssel; Klaus Schäfer
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2002-06-18
Filing date: 2003-06-05
Publication date: 2005-03-16
Also published as: US20050194551A1; NO20050282L; CN100521450C; WO2003107512A1; CN1663094A; DE10227227A1

Abstract

The invention relates to a corona shield of an electrical machine, which comprises a supporting material and a coating or a fabric or tile that is made of coated strings. Said coating is provided with electrically conductive inorganic material.

Description

description

corona shielding

The invention relates to a glow protection for electrical machines. Such a glow protection usually has a fabric or a fleece.

Such fabrics are known, for example, from the DIN standards EN 16740 and DIN 16741 from 1976 (January). DIN 16740 discloses a textile glass fabric for electronic purposes. DIN 16741 discloses textile glass fabric walls with fixed edges for electronic purposes. The fabrics serve, for example, as carriers for impregnants, electrical properties being achievable by the impregnants. For example, a glow protection can be produced by impregnation.

The smoldering protection can also be produced, for example, by a chemical reduction process, in the US. -PS 3,639,113. The value of the electrical conductivity set by reduction is difficult to reproduce. Furthermore, this reduction process is complicated and expensive.

The object of the present invention is to provide a glow protection for an electrical machine, the electrical properties of which can be set in a reproducible manner and / or which has a longer service life. The glow protection should also be easy and / or inexpensive to manufacture.

The object is achieved in that a glow protection for an electrical machine has a carrier material and a coating thereon.

In a process for producing the smoldering protection, a coating is applied to a carrier layer. In the production of glow protection, for example, a glass fabric that is not electrically conductive is used as the base material. The tissue made of inorganic material is soaked in a solvent. The solvent contains, for example, organometallic and / or inorganic transition metals. After the solvent has evaporated, the soaked glass fabric is calcined at a temperature of approx. 600 ° C. The electrical conductivity can be determined, for example, by means of an animon tin oxide layer on the surface via the thickness and doping.

Because the glow protection has both a carrier material and a coating thereon, that is to say a coating material, the function of the glow protection can be separated. On the one hand, the carrier material in particular also determines the mechanical property of the glow protector, on the other hand, the electrical property of the glow protector is also determined by the coating. The coating has electrically conductive inorganic material. The electrically conductive inorganic material is less sensitive to partial discharges than the prior art due to the lack of an organic component. According to the invention, the smoldering protection can therefore only be constructed from inorganic material.

The carrier material advantageously consists entirely of inorganic material, since damage due to partial discharges can thus be avoided. The coating of the carrier material also consists at least of an inorganic material. The glow protection therefore advantageously consists only of inorganic material. Of course, it can also be advantageous if components of the carrier material have organic chemical compounds such as glue. With an adhesive at the beginning and at the end of a glow protection tape, this can be improved, since the tape for winding on the main Isolation / insulation can be attached both at the beginning and at the end. The carrier material of the smoldering protection is, for example, a fabric and / or a fleece. All electrically insulating inorganic fabric types / tile types that are stable in the temperature range required for the electrical machine can be used as carrier materials. Glass fabrics and fabrics made of aluminum oxide or aluminum oxide containing SiO 2 are preferred. The same materials can also be used for tiles.

The object of the invention is also achieved by a glow protection for an electrical machine, the glow protection being designed as a fleece and / or as a fabric which has fibers and / or threads, the fibers and / or the threads being made of an inorganic material and the fibers and / or the threads are coated with an inorganic material. In a corresponding process, the fibers of the fleece or threads of the fabric are coated accordingly.

The coating of the fibers or threads has, as in the coating of the carrier material, at least in parts electrically conductive inorganic material. In a further embodiment, the coating has only electrically conductive inorganic material.

If glow protection is made up of electrically conductive coated fibers (for the formation of tiles) or threads (for the formation of fabrics), an additional coating of the fabrics or the tiles can advantageously be omitted. An additional one

The possibility of adjusting the electrical conductivity of the glow protection results from a mixture of electrically conductive fibers / threads with electrically non-conductive fibers / threads.

Glow protection is particularly used to protect the insulation of electrical machines such as motors, for example, railway engines, and generators, in particular turbogenerators, for voltages in the kV range, in particular greater than or equal to 3.3 kV. With applied voltages greater than 3.3 kV, precautions are necessary to avoid partial or glow discharges or to control the potential. In the groove area of a laminated core of an electrical machine, internal and external glow protection is mentioned, and in the winding head area, end glow protection or end glow protection.

In the state of the art, as already described, fabric or assembly lines made of glass or polyester are generally used as glow protection, which are impregnated with a filler-containing binder. Paintings containing fillers are sometimes used for single-rod impregnation. Carbon black or graphite are generally used as electrically conductive fillers in the slot area, and electrically semiconducting silicon carbide is used in the winding end area. Due to the necessary organic binding agents, the materials mentioned can only be subjected to limited thermal loads (up to approx. 180 ° C) and are quickly destroyed by partial or glow discharges. In addition, their electrical conductivity is influenced in an unforeseeable way by a VPI impregnation process (VPI stands for Vacuum Pressure Impregnation). By abrasion e.g. of the graphite or leaching, the VPI impregnating agent and the adjacent insulation area can be contaminated by electrically conductive fillers. However, this also adversely changes the electrical conductivity.

The glow protection according to the invention can be implemented, for example, as a fabric or assembly line which is coated with electrically conductive inorganic material or materials. The necessary electrical conductivities for internal and external glow protection (5 * 102 ΩD to 5 * 104 ΩD) and for the end glow protection (5 * 107 ΩD to 109 ΩD) are due to different doping, ie different concentrations rations or also reachable by different layer thicknesses of the electrically conductive layer.

Since thermally stable inorganic materials are preferably used, permanent temperature resistances up to

500C ⁰ realizable. As a result, the electrical machines can be subjected to higher loads with regard to the end glow protection or the external glow protection. The conductivity of the fabric or tile is not influenced by a subsequent VPI soaking process. Contamination of the VPI impregnating agent by electrically conductive components of the glitter protection systems (fillers) is excluded, since the electrically conductive coating adheres firmly to the inorganic carrier material.

In addition to insulation, glow protection is of particular importance in an electrical machine. As already mentioned, this applies in particular to high-voltage machines which have a voltage of approximately 3.3 kV. When developing insulation systems for machines, three parameters are considered in particular:

The thermal stability, the thermal thermal conductivity and the electrical properties.

With regard to the electrical properties, attention must be paid to both the electrical resistance and the distribution of electrical field strengths. Micabased insulation systems are used especially in high-voltage machines.

A maximum field strength of approx. 3.5 kV / mm can be achieved with Mica. The insulation of conductors within electrical machines can be set up in such a way that the conductor is initially surrounded by an insulating layer and then a glow protection layer is added around this insulating layer as an additional layer. The glow protection contributes to an even field distribution on the surface of the conductor at. Furthermore, the glow protection within the electrical machine is adjacent to the stator core in the stator slots. The stator core is, for example, set to zero potential or neutral potential. The electrical glow plug can be designed differently from the end glow plug. Both the insulation and the glow protection of an electrical machine depend on the use of the electrical machine. In particular when operating an electrical machine on converters, which carry out pulse modulation, there are increased demands on the insulation and on the glow protection, which is also referred to in English as "corona shielding".

In an advantageous embodiment of the glow protection, the coating has an electrically conductive inorganic material. The use of a conductive electrical inorganic material overcomes the disadvantage when using carbon black or graphite that they are influenced by partial discharges. Partial discharges cause ozone. Ozone destroys organic material like that

Resin as a binder of SiC or also the carbon black or the graphite itself. This adversely changes the electrical conductivity of the glow protection. The destruction of organic material increases the partial discharge on the conductors within the electrical machine, so that in turn more ozone is formed, which contributes to an increased extent to the destruction of organic material. This creates a kind of vicious circle, which can lead to great damage to the glow protection. Soot or graphite was previously given in organic resin, with which a glass fabric or a polyester is soaked in the fabric. Silicon carbide can also be introduced into the organic resin to increase the electrical conductivity. The use of organic resin to impregnate glass fabrics or polyester fabrics limits the maximum temperature that can be set in the electrical machine. The ozone generated by partial discharge destroys both the soot and the graphite, which is in the organic Resin is present, so that the conductivity of the glow protection is reduced, as is the organic resin itself, so that it dissolves more and more and the glow protection is destroyed, the glow protection from the glass fabric, the organic resin and the substances contained therein There are substances for adjusting the electrical conductivity.

In an advantageous embodiment, the carrier material, like the coating thereon, consists of inorganic material. As a result, not only can increased temperature resistance be achieved, but also insensitivity to ozone caused by partial discharge.

Glass, aluminum oxide AlO and silicon carbide SiC are to be mentioned as inorganic carrier materials for the coating. A fleece or a fabric can be produced from these materials as a carrier.

The glow protection can be equipped with different electrical properties as external glow protection, AGS for short, or as end glow protection, EGS for short.

The end glow protection preferably has a resistance value of 5 × 10 ⁸ Ωm. The external glow protection typically has a value of around 1000 Ωm. However, these are only guidelines that depend on many factors. Corresponding factors are, for example, the voltage and the length of an end glow protector. The glow protection serves both for external glow protection and in particular for final glow protection to equalize potential on the surface of the main insulation. This means that other resistance values that deviate from the above figures are also possible.

The glow protection continues to ensure a homogenization of the electrical field. The end glow protection is used to send the potential of the stator core package of the electrical see machine. The field strengths occurring in the air on the conductor provided with glow protection no longer lead to arcing in the air.

By using different coatings of a carrier material, the different requirements of an external glow protection with regard to the requirements of a final glow protection can be easily changed since the glow protection now only differs in its coating and the carrier material remains the same.

The glow protection is used in particular in electrical high-voltage machines. In general, high-voltage electrical machines are operated at voltages greater than 3 kV. Due to the high voltages, equipotential bonding on the conductors is necessary using glow protection.

The smoldering protection according to the above-mentioned configurations is produced in a method in such a way that a coating is applied to a carrier material. The coating can be applied in various ways.

The coating can be sprayed onto the carrier layer, for example. Since the inorganic coating, which is at least partially or completely electrically conductive, is sprayed onto the inorganic carrier layer, an inorganic glow protection is produced. For spraying, solvents such as alcohol can be used, which can also be organic. An organic solvent evaporates and ultimately does not form part of the glow protection.

A further possibility of applying the coating to the carrier layer is to evaporate the coating onto the carrier layer so that a layer with inorganic conductive material is formed on the carrier layer. In addition to the coating of the carrier layer, it is also possible to coat individual fibers or individual threads or rovings (threads twisted together). The coating takes place, for example, in such a way that it is evaporated onto the fibers and / or threads. Another possibility of the coating is that the coating is sprayed onto the fibers and / or threads. A third possibility of coating results from the fact that the fibers or the threads are passed through an immersion bath.

A type of immersion bath is also used as a method for coating a carrier material, e.g. a glass fabric, applicable.

In order to produce insulating tapes for glow-protection layers in windings for electrical machines, a fabric-like carrier material is coated with a solution, a sol or a suspension in an electron-conducting manner. This is an alternative to electron-conductive coating by spray, dip or flame coating.

In the production of insulating tapes for glow protection layers, the electron-conducting coatings are annealed at 350-700 ° C., so that adherent, coherent and electrically conductive coatings are produced on the surface of the fabric. This thermal treatment can take place in different atmospheres, e.g. Air, forming gas, N2, NH3, are carried out. The thermal treatment takes place, for example, in an oven, electrically or fossil-heated, or by infrared radiators and / or other radiation sources, e.g. Laser.

Such a method can be used to produce an electron-conducting coating both on a carrier material and in the case of fibers or threads or rovings. These electron-conducting coatings consist, for example, of metal oxides, primarily indium, tin, arsenic, Antimony oxide, transition metal oxides, and any mixtures of these.

Inorganic salts or complex compounds of metals, primarily indium, tin, arsenic and antimony, preferably acetates, alcoholates, acetylacetonates, oxalates, halides, nitrates, sulfates, are used as the starting compound for the production of the coating of insulating tapes for corona protection layers. Suspensions of the smallest particles of metal oxides, primarily indium, tin, arsenic, antimony oxide, transition metal oxides can also be used for coating.

The resistance of the coating can be set, for example, by the thickness of the coating, but also by the differentiated use of electrically conductive materials in the coating and their concentration. In the case of a dipping process in a solution, a sol or a suspension for producing a coating, the thickness of the coating is a parameter for setting the layer thickness, for example due to the speed at which the object to be coated runs through the dipping bath.

If a coating process is used several times, more than one coating can be formed. In particular when coating fibers, threads but also in the case of a band-shaped carrier material, this can advantageously be used to form an adhesive layer which improves the adhesion between the electrically conductive coating and the carrier layer, or the uncoated thread or the uncoated fiber. Several coatings can also be used in such a way that they create a balance between different coefficients of thermal expansion. In addition to the statements already made, manufacturing processes for a coating are now to be named again:

spray:

A solution, a sol or a suspension are sprayed onto a belt as a carrier material using a spray device. Here, the tape is preferably guided past the spray device. The spray coating can only be carried out on one side or, preferably simultaneously or promptly, from both sides.

Dip coating: In a solution, a sol or a suspension, the glass fabric tape is immersed as a carrier material and pulled out, preferably at a constant speed. This creates an adherent layer of constant thickness. The process is preferably carried out continuously. The glass ribbon is passed through a coating bath which contains the solution, the sol or the suspension. This is preferably done at a constant speed.

Combustion chemical vapor deposition:

A solution, a sol or a suspension is sprayed into a flame. The flame is directed onto the glass fabric tape, which serves as the carrier material. This creates a uniform oxidic coating on the belt. The flame coating can be carried out from only one side or, preferably promptly or simultaneously, from both sides. The flame can be a gas flame or a flame held down by flammable liquids. The flammable liquid can also be the sprayed solution itself. One can also be advantageous

Plasma flame can be used. The glass fabric tape can have room temperature or a temperature increased to 500 ° C.

Sputtering is also a possible coating process.

After a previous coating, thermal post-treatment can also be carried out:

The coating obtained by one of the aforementioned processes is post-treated thermally. Depending on the layer composition and coating technology, temperatures between 350 and 700 ° C are used. The thermal treatment is carried out in an air atmosphere or under a protective gas, or it can also be carried out in a reactive atmosphere, e.g. B. forming gas, NH3 or CH4.

For spray coating as well as for dip coating, thermal post-treatment is generally necessary, while thermal post-treatment does not necessarily have to be carried out after the flame coating.

The thermal aftertreatment takes place in an electrically heated furnace or in a fossil (gas or liquid fuel) heated furnace. According to the invention, infrared emitters and / or other radiation sources can also be used for this. The combination of these heat sources is also possible.

The thermal aftertreatment can be carried out batchwise, but continuous thermal treatment is preferred. Here the carrier material, for example a glass ribbon, is drawn through an oven after the coating has been completed. This furnace can have a locally constant temperature, or can be divided into zones of different temperatures. This allows the continuous strip related thermal treatment in the form of a defined temperature-time profile.

The coating leads to a certain chemical composition of this coating. Inorganic oxide layers are preferred. For example, the layers can consist of doped titanium oxide or tin oxide. Sb ₂ 0 ₅ , Nb ₂ Os, Ta ₂ Os or V2O5 can be used as doping, for example. It is also possible to use undoped layers of Ti0 ₂ or Sn0 ₂ if these are brought into a sufficient electron-conducting state by adding reducing components and / or reducing gas atmospheres during the thermal aftertreatment. Other oxidic coatings, such as Nb ₂ Os, M0O2 or Ta ₂ Os, can also be used; these layers can also be doped. Another preferred possibility is the use of electron-conducting In203 layers, which contain up to 50% by weight. Snθ2, but preferably with 2-5% by weight. Sn0 ₂ can be doped. Examples of further oxide layers according to the invention are CuO, MnO, NiO, CoOx, FeOx and mixtures or compounds of these or of these oxides. In general, transition metal oxide, arsenic, indium, antimony and tin oxide and any mixtures of these or compounds of these oxides can therefore be used.

All solutions which meet the requirements of the coating methods described above can be used as the coating solution. In particular, solutions of inorganic salts or complex compounds of the aforementioned metals should be mentioned. Halides, sulfates, nitrates, acetates, oxalates, acetylacetonates or salts of other organic acids are preferred. Alcoholates of the corresponding metals are also preferred. The solutions can be aqueous solutions, but also alcoholic solutions, which can both contain organic additives. Even the use of organic Solvents are possible. Sols containing the corresponding metal components can also be used. These can be produced, for example, from alcoholates or from halides or acetates or other salts of organic acids using the sol-gel process.

According to the invention, the use of suspension containing the smallest particles in water or organic solvents is also possible. The particle size can be a few n to a few micrometers. The use of particle sizes in the range from 5 nm to 200 nm is preferred. These can be oxidic or hydroxide particles or else particles from chemical compounds which are converted into oxides during thermal treatment. Here, for example, carbonates, acetates or oxalates are mentioned. The suspensions can contain stabilizing or other additives made from organic or inorganic components.

After the thermal treatment has ended, a layer of an organic polymer can be applied. As a protective layer, however, this layer no longer adversely changes the electrical properties of the glow protection.

An exterior glow protection tape is now used as an example

Glass fabric coated with antimony-doped tin dioxide (5 mol%):

The sol for coating is produced from SnCl ₂ * 2H ₂ 0. 50.77 g (0.225 mol) of SnCl ₂ * 2H ₂ 0 (M 225.63) are dissolved in 600 ml of absolute ethanol and then in a flask with reflux condenser and attached drying tube heated under reflux. The solvent is distilled off and the residue, a white powder, is taken up again with 300 ml of absolute ethanol. The resulting solution is stirred for 2 hours at a temperature of 50 ° C. After cooling, 2.57 g (0.011 mol) of SbC13 (M 228.11) are dissolved in a few milliliters of absolute ethanol. Care should be taken to ensure that no permanent precipitation occurs. The glass fabric tape is pulled through the solution, which has aged for several days, at a constant drawing speed of 20 cm / min. The coating is dried at 110 ° C. for 15 minutes and then baked at 500 ° C. for 20 minutes. The result is a transparent, electrically conductive coating that has the following reproducible properties: Layer thickness: 80-100 nm layer resistance: 900 Ω / D - 4.0 KΩ / D

Another example is an external glow protection tape made of glass fabric, coated with tin-doped indium oxide (5 mol%):

The coating solution is prepared from In (N0 ₃ ) 3 * (H2O.5. 45.12 g (0.15 mol) of In (N0 ₃ ) ₃ * (H ₂ 0) 5 (300.83) in 300 ml of absolute ethanol together with Dissolved 30.90 ml (0.30 mol) of acetylacetone (M 100.12)

Stir 1.69 g (0.0075 mol) SnCl ₂ D 2H ₂ 0 (M 225.63) directly into the solution. The glass fabric tape is pulled through the resulting and aged solution at a constant drawing speed of 30 cm / min. The coating is dried for 15 min at 110 ° C and then baked at 550 ° C for 30 min. A transparent, electrically conductive coating is produced which has the following reproducible properties: Layer thickness: 90-110 nm layer resistance: 3 KΩ / D - 8 KΩ / D

Another example is the following process for producing an external glow protection tape from glass fabric, coated with fluorine-doped tin dioxide (5 mol%): The sol for coating is made from SnCl ₂ * 2H0. 60.92 g (0.27 mol) of SnCl ₂ * 2H ₂ 0 (M 225.63) are dissolved in 600 ml of absolute ethanol and then heated under reflux in a flask with reflux condenser and attached drying tube. The solvent is distilled off and the residue, a white powder, is taken up again with 300 ml of absolute ethanol. The resulting solution is stirred for 2 hours at a temperature of 50 ° C. After cooling, 0.34 ml (0.0043 mol) of CF ₃ COOH (M 114.03) is slowly added dropwise with stirring. Care should be taken to ensure that no permanent precipitation occurs. The glass fabric tape is pulled through a solution aged for several days at a constant pulling speed of 10 cm / min. The coating is dried at 110 ° C. for 15 minutes and then baked at 500 ° C. for 30 minutes. The result is a transparent, electrically conductive coating that has the following reproducible properties:

Layer thickness: 100-110 nm

Sheet resistance: 30 KΩ / D - 60 KΩ / D

Exemplary embodiments of the invention are explained in more detail with reference to the drawings. Show it:

1 shows the insulation of a conductor with the associated stator plate,

2 shows a carrier layer with a coating

3 shows the exit of a conductor from a stator laminated core,

5 shows the dependence of the conductivity on the concentration of electrically conductive substances,

FIG β two examples of a fabric and 7 shows a structure for carrying out the method for coating.

1 shows a section of a stator core 1 of an electrical machine. An electrical machine essentially consists of a stator, which is constructed from the so-called core sheet stack 2, in which 9 insulated windings / copper conductors 3 are inserted in preformed stator slots, and the rotor, which rotates in the stator. The Städner laminated core 2 is composed of a certain number of individual laminations stacked on top of one another, the upright laminations 1, into which upright grooves 9 are stamped. The stator winding is inserted into these stator slots 9 and, depending on the requirement, is provided with a specific insulation system. A typical insulation system for high-voltage machines has a main insulation in the following also called conductor insulation 7, around which mica tapes 4, 5 are wound. Preferably for high-voltage machines> 3.3 kV, for converter-fed rail and high-voltage machines and for thermally highly utilized machines such as rail motors, the surface of the stator insulation in the groove area is provided with an electrically highly conductive external glow protection (AGS) 5 to protect the insulation from damage caused by excessive partial discharges to protect. The external glow protection 5 extends beyond the stator core 2, so that no discharges can occur even at short distances against pressure plates and pressure fingers of the stator core 2. Using an impregnation process (VPI process), the windings are impregnated with an impregnation resin, which is then cured. This means that the external glow protection tape 5 used must be compatible with this complex process. The tape must not contain any components that interfere with the impregnation process or release it into the soaking bath. In addition, it must be incorporated homogeneously in the molding material formed after curing, so that partial discharges are avoided. According to the current state of the art, soot or graphite-containing fabric tapes or lacquers are used to produce the external corona protection layer 5. In the VPI all-soak process, woven or non-woven tapes based on glass or polyester are used, which are provided with an organic binder with a filler that is conductive according to the requirements (carbon black, graphite). In the case of winding elements which are produced by the single-rod impregnation process or the RR process, corresponding exterior glow protection layers 5 are applied on a lacquer basis in the painting process.

However, glow protection tapes 4, 5 or lacquers with carbon black or graphite as conductive filler known from the prior art have serious disadvantages. Due to the organic binders and carrier materials required for processing and the desired properties, the materials have only a limited thermal resistance up to a maximum of 180 ° C. In addition, the materials when

Partial discharges quickly destroyed and therefore ineffective. In addition, the electrical conductivity of commercially available external glow protection tapes changes during the impregnation process. There is also the risk that soot or graphite particles are carried away unintentionally by the impregnation resin and thereby impair the quality of the impregnation.

The invention makes it possible to produce external glow protection tapes 5, as well as corresponding end glow protection tapes 4 as shown in FIG. 1, in reproducible quality

To make available. The insulation must therefore be reliably protected against partial discharges and the impregnation process and the quality of the rest of the insulation must not be impaired. In addition, the glow protection 4.5 according to the invention has a significantly higher thermal resistance compared to the previously known glow protection tapes or in comparison with lacquers. The illustration according to FIG. 1 consequently shows schematically the place of use of a glow protection according to the invention. A stator core 2 is shown, which is composed of stator core 1. Copper conductors 3 are located within stator slots 9. The copper conductors 3 have conductor insulation 7. The conductor insulation 7 is advantageously made stronger inside the stator core 2 than outside the stator core 2 where the copper conductors 3 form a winding end, which is not shown in FIG. 1, however. There is a glow protection 4.5 on the conductor insulation 7. The glow protection for the area of the copper conductor 3, which is located within the stator core 2, is referred to as external glow protection 5 - AGS. The glow protection on the conductor insulation 7, which is located outside the stator core 2, is referred to as end glow protection 4 - EGS. Both the external glow protection 5 and the end glow protection 4 serve for electrical potential control. The glow protection 4, 5 is made at least from a carrier layer and a layer thereon, which can be designated as a coating layer. Consequently, it is also possible to carry out a smoldering protection which has more than one carrier material and / or more than one coating, but is not shown in the figure.

The illustration according to FIG. 2 shows a glow protection 14 which has a carrier material 10 and a coating 12. Depending on the purpose of the glow protection, i.e. as external glow protection or as end glow protection is both that

Backing material 10 but in particular also the coating 12 can be implemented differently, for example with regard to the thickness. The carrier material 10 consists, for example, of glass fibers. A fabric can be produced from this glass fiber. This results, for example, in canvas formation with Velcro or weft threads. Depending on the type of fabric selected, the stability or flexibility can be set differently. In principle, it is advantageous to be able to make the tissue as thin as possible. The fabric structure is also of particular importance because it can be used to influence the field smoothing. The coating 12 has electrically conductive inorganic substances. These are, for example, metals with different oxidation levels. Since the external glow protection generally has a higher electrical conductivity compared to the end glow protection, a higher concentration of metals allows different levels of oxidation within the glow protection to change the end glow protection to the external glow protection.

The illustration according to FIG. 3 shows in detail the transition of the copper conductor 3 from the stator core 1 into the air 16. The copper conductor 3 has both conductive insulation 7 and an external glow protection 5 and an end glow protection 4. The two glow protectors meet at connection 6. The step connection between the external glow protection 5 and the end glow protection 4 results from the fact that the glow protection is advantageously wound as a tape overlapping the conductor insulation of the copper conductor, so that the glow protection is located on the conductor insulation 7 in two layers, for example. Of course, other winding options are also possible, which lead to a single-layer or multi-layer winding by a tape.

The illustration in FIG. 4 shows the conductivity 18 on the Y axis and the concentration of electrically conductive materials on the X axis 20. For example, carbon or silicon carbide can be used as the electrically conductive material. Curve 22 shows a steep increase 24 within a small concentration change band 26. This shows the problem of adjusting the concentration of conductive materials according to the prior art by impregnating a carrier material. By draining or

Evaporation can easily result in a shift in concentration, leading to a large change in conductivity leads. Another problem in the present case is that damage to the glow protection caused by ozone generated during partial discharge can lead to a major change in the conductivity. Through the use of inorganic material both for the carrier material and for the coating and the retrieval of electrical conductivity by means of electrically conductive material within the coating, the above problem is solved in the present invention.

5 shows two fabrics 40, 41. The fabric 40 is a plain weave. The fabric 41 is a body bond. Both types of fabric are to be understood as an example both for a fabric which serves as a carrier material for a coating and as an example for a fabric whose threads are coated.

The illustration according to FIG. 7 shows an example of a coated thread or a coated fiber, which has a glass fiber 51 inside, which represents the thread core or the fiber core and is surrounded on the outside by a coating 50.

The illustration according to FIG. 8 shows a dip coating with subsequent calcination (heat treatment). A fabric-like carrier material (77) is coated with a solution, a sol or a suspension in an immersion bath 72. The direction of movement 74 of the carrier material is indicated by an arrow. The immersion bath contains various inorganic materials dissolved in alcohol which lie on the carrier material 77 in the immersion bath. Inorganic materials can be selected that show electron-conducting properties directly or after thermal aftertreatment. Depending on the coating process, the solvent in the present case becomes alcohol, for example, by elevated temperature - which results in evaporation 75 - in one Intermediate treatment device 73 and / or removed by dripping 76. During a subsequent thermal aftertreatment in a heating section 71, calcination is carried out at temperatures between 350 ° C. and 700 ° C., so that a firmly adhering, coherent and electrically conductive coating is formed on the surface of the fabric. The layer thicknesses of the electron-conducting layer are a few nm to a few micrometers, preferably 50 nm to 500 nm. A glow protection tape 70 can be removed from a coating device 78 as described above.

All electrically insulating inorganic fabric types that are stable in the specified temperature range can be used as carrier materials. Glass fabrics and fabrics made of aluminum oxide or aluminum oxide containing SiO 2 are preferred.

Claims

claims

1. Glow protection for an electrical machine, so that the glow protection has a carrier material and at least one coating on it.

2. glow protection according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the carrier material and the coating consist of inorganic material.

3. smolder protection according to claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t that the carrier material is a fleece and / or a fabric.

4. Glow protection according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the carrier material consists of glass.

5. glow protection according to one of claims 1 to 3, d a d u r c h g e k e n n z e i c h n e t that the carrier material consists of silicon carbide SiC.

6. glow protection according to one of claims 1 to 3, d a d u r c h g e k e n n z e i c h n e t that the carrier material consists of aluminum oxide AlO.

7. Glow protection for an electrical machine, wherein the glow protection is designed as a fleece and / or as a fabric which has fibers and / or threads, characterized in that the fibers and / or the threads consist of an inorganic material and the fibers and / or the threads are coated with an inorganic material.

8. Glow protection according to claim 7, so that the fibers and / or threads have a fiber core or a thread core, which consists of glass or silicon carbide or aluminum oxide.

9. Glow protection according to one of the aforementioned, that is, that the coating consists of at least one electrically conductive inorganic material.

10. smolder protection according to claim 9, d a d u r c h g e k e n n z e i c h n e t that the electrically conductive inorganic material of the coating is antimony tin oxide.

11. Use of the glow protection according to one of the preceding claims as external glow protection.

12. Use of the smoldering protection according to one of claims 1 to 11 as final smoldering protection.

13. Use of the glow protection according to one of the preceding claims in an electrical high-voltage machine.

14. A method for producing a smoldering protection according to claim 1, in which a coating is applied to a carrier material.

15. A method for producing fibers or threads or rovings for producing a glow protection according to one of claims 7 to 10, characterized in that a coating is applied to a fiber or a thread or a roving.

16. A method for producing a smoldering protection according to claim 14, that the coating is carried out by a spray coating or a dip coating or a flame coating.

17. A method for producing fibers or threads or rovings for producing a smoldering protection according to claim 15, d a d u r c h g e k e n n e e c h n e t that the coating is carried out by a spray coating or a dip coating or a flame coating.

18. Electrical machine, so that it has a glow protection according to one of claims 1 to 10.