EP3443567A1

EP3443567A1 - Corona shield, electric machine, and method for manufacturing the corona shield

Info

Publication number: EP3443567A1
Application number: EP17720407.0A
Authority: EP
Inventors: Mario Brockschmidt; Christopher ECKERT; Manuel Ettler; Vera Kristin FRANKE; Rene Höhner; Andrey Mashkin; Friedhelm Pohlmann; Guido Schmidt; Ralph Seybold; Christian Staubach
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2016-05-23
Filing date: 2017-04-21
Publication date: 2019-02-20
Also published as: US20200321821A1; WO2017202550A1; EP3249659A1

Abstract

The invention relates to a corona shield for an electric machine, comprising a varnish (4) that contains a first polymer resin, first electrically conductive particles (6) that are dispersed in the first polymer resin, and microcapsules (5) which are dispersed in the first polymer resin and include a second polymer resin in their interior.

Description

description

Corona protection, electrical machine and method for

Making the corona shield

The invention relates to a corona protection and an electrical machine with the corona protection.

An electrical machine, such as a turbogenerator in a power plant for generating electrical energy, is exposed to high mechanical, thermal and electrical stress. In particular, the turbogenerator has a laminated core and a winding of electrical ^conductors . The laminated core has a plurality of grooves in which the conductors are introduced. At the two ends of the

Blechpakets stand out the electrical conductors from the laminated core. The conductors are surrounded by a main insulation, which electrically isolates the conductors against each other, against the laminated core and against the environment.

To avoid partial discharges, a glow protection is arranged on the surface of the main insulation facing away from the conductor. To avoid partial discharges at the interface between the main insulation and the laminated core, the corona shielding between the main insulation and the laminated core has a weakly electrically conductive and grounded external corona protection, which can protrude from the laminated core. To ground the Außenglimmschutz is electrically connected to the laminated core. The external corona shield homogenizes the electrical field emanating from the electrical conductor. As ^¬ with areas with locally excessive electric field strength can be avoided whereby the formation of partial discharges at the surface of the main insulation is suppressed.

Further, the corona shielding has an end corona shielding provided at the axial end of the outer corona shield at the interface between the main insulation and the surroundings. The Endeglimmschutz is weakly electrically conductive and can also have a linear decreasing resistance profile with increasing distance from the Außenglimmschutz. The end glow protection is set up to reduce the electric field formed during operation of the turbogenerator in a direction away from the laminated core.

Damage to the external corona protection, which can occur, for example, when inserting the main insulation and the outer corona protection encased electrical conductor in the groove or when driving Nutseidenfedern between the outer corona and the laminated core, affect the electric field homogenizing effect of Außenglimm- protection and can lead to an increase in the electric field strength and thus to the partial discharges. The partial discharges ^¬ lead to decomposition of the main insulation and the outer corona, and thus shorten the life of the electrical machine. Damage to the end corona shielding can affect the electric field relieving effect of the end corona shielding and thus contribute to the decision ^¬ stehung partial discharges in the area of end corona shielding.

The object of the invention is therefore to provide a corona protection for an electrical machine, with the corona, the life of the electric machine can be extended.

The corona shield according to the invention for an electric Maschi ^¬ ne has a coating comprising a first polymer resin, dispersed in the first polymeric resin first electrically conductive

Particles and in the first polymer resin dispersed microcapsules having in their interior a second polymer resin. In a damage of the invention

Anticorrosive burst on the microcapsules in the damaged area, whereby the second polymer resin located in the microcapsules flows into the damaged area and cures there. This allows the corona shield to repair itself, whereby the corona protection and thus also the electrical see machine have a long life. The first elekt ^¬ driven thereby conductive particles cause an electrical conductivity of the corona shield. In the case that the first electrically conductive particles remain in the damaged area of the corona shield, the electrically conductive particles cause a weak electrical conductivity in the repaired corona protection. It is preferable that the first polymer resin and the second polymer resin are the same. It is preferred that the corona protection is an external corona protection and / or an end corona protection.

It is preferred that the lacquer comprises second electrically conductive particles which are arranged in the interior of the microcapsules. As a result, when the corona protection is damaged, the second electrically conductive particles also flow into the damaged area. It is thereby achieved that the damaged area after the curing of the second polymer resin is electrically conductive, so that an electric field emanating from an electrical conductor of the electric machine is also homogenized in the region of the damaged area and around this area. Characterized ^¬ field strength peaks are advantageously suppressed, whereby partial discharges can be avoided in the operation of the electrical machine. It is preferred that the mass fraction of the microcapsules loading subjected to the paint and the mass fraction of the second particles is chosen to be high on the lacquer, that the second particles überperkolierend vorlie ^¬ gene in the ausgehär ^¬ depressed area This means, that the second particles form a continuous network in the off ^¬ cured area, the edge points of the cured portion interconnecting where ^¬ a whole is electrically conductive by the damaged area after curing the second polymer resin. It is preferred that the first electrically conductive particles and / or the second electrically conductive particles of graphite, carbon black and / or inorganic particles with an electrically leit ^¬ coating capable of having. It is preferable that the sum of the proportions by weight of the microcapsules and the first electroconductive particles is 6 to 90% with respect to the varnish ΠΠ 5 ". The addition of the microcapsules increases the viscosity of the varnish, but low viscosity is advantageous in processing of the paint. In the specified range of values for the weight fraction of the coating has rokapseln a sufficient low viscosity for processing o ^¬ processing as well as a sufficiently high weight fraction of the Mik ^¬ order to achieve a good healing of the damaged area. the weight ratio of the microcapsules to the first electrically conductive particles is preferably from 1 to 10, in particular from 1 to 2.

It is preferable that the polymer resin is a copolymer. In this case, it is preferred that the copolymer is a polymer based on polyacrylate, in particular acrylate and / or acrylonitrile, and / or polystyrene. Further, it is preferable that a part of the microcapsules have only one of the monomers of the copolymer and another part of the microcapsules merely another one of the monomers of the copolymer. Since ^¬ come through the two monomers advantageously only in contact when burst the microcapsules in the damage, whereby the curing can take place only after damage. The microcapsules preferably have in their interior electrically non-conductive inorganic nanoparticles, in particular, the nanoparticles Ti0 ₂ , Si0 ₂ , Al ₂ O ₃ and / or MgO. In the event that after the hardening of the damaged area nevertheless partial discharges occur in and / or in the vicinity of the damaged area, the area cured with the nanoparticles has a higher resistance to the partial discharges and thus a longer service life than it would be the case without the nanoparticles. The microcapsules preferably have in their interior a solvent, in particular ethanol, n-propanol, isopropanol, ethyl acetate and / or an alkane, in particular n-pentane, n-hexane and / or n-heptane. As a result, the viscosity of the reduced in the microcapsule liquid, ie, the polymer resin with the solvent, whereby the liquid after the bursting of the microcapsules can be finely distributed in the damaged area and can also penetrate into very small cracks. This allows almost complete repair of the damaged area. In addition, by evaporation of the solvent, the curing of the polymer resin can take place. It is preferable that the wall material of the microcapsules

Wax, polyurea-formaldehyde and / or polyurethane on ^¬ points. The microcapsules preferably have a middle one

Diameter from 10 ym to 1500 ym. It is preferred that the microcapsules have a wall thickness of

50 nm to 500 nm. Due to this wall thickness, the Mik ^¬ rokapseln have sufficient strength so that they do not burst when ^¬ nor paint processing of the resist, but at the same time, the wall thickness is such that they burst in damage to the corona shield.

The corona protection preferably has a porous band which is impregnated by the lacquer. Due to the band, the corona protection has an increased mechanical strength. Preferably, the impregnated tape of the paint has a sufficient porosity to be processed in a VPI (vacuum pressure impregnation) method, ie, the porosity is sufficiently high, so that impregnated by the paint tape of a resin, in particular an epoxy resin , can be soaked. Preferably, the tape is partially porous according to the performed VPI method, so that the capillary action of the tape allows the polymer resin located in the microcapsules to spread particularly well in the damage to the microcapsules in the tape. The partial porosity can be achieved, for example, by means of hollow fibers in the band. Due to the partial porosity, the corona protection can heal particularly well and without the formation of trapped air, which promotes the formation of partial discharges. It is preferred that the band is a fabric and / or a nonwoven fabric, in particular the nonwoven fabric and / or the fabric comprises polyethylene terephthalate (PET), polyester, glass, polyimide, polyaramide, polyamide, polypropylene and / or PTFE.

The electric machine according to the invention comprises a step elekt ^¬ conductor, a main insulation, which surrounds the electrical conductor and the corona shield that is applied to the outer side of the main insulation. The corona shield should be an external corona shield and / or an end corona shield.

The inventive method for manufacturing the Glimmschut ^¬ zes comprises the steps of: - applying a lacquer, comprising a first polymer resin, in the first polymer resin dispersed first electrically conductive particles and in the first poly ^¬ merharz dispersed microcapsules containing a second in its interior Polymer resin, on an electrical conductor enclosing the main insulation; - curing of the polymer resin. The paint can either be applied directly to the main insulation and cured or the paint can first be applied to the tape and cured on the tape and then the tape can be applied with the cured paint on the main insulation. It is preferred that the lacquer comprises a solvent, in particular ethanol, n-propanol, isopropanol, ethyl acetate and / or an alkane, in particular n-pentane, n-hexane and / or n-heptane, outside and inside the microcapsules, and the polymer resin is cured by evaporation of the outside of the microcapsules located solvent.

In the following the invention will be explained in more detail with reference to the accompanying schematic drawings. Show it:

Figure 1 before a corona protection according to the invention

damage,

Figure 2 shows the corona protection after damage and Figures 3 and 4 the process of annealing the ^{Beschädi ¬} tion.

As can be seen from FIGS. 1 to 4, a glow contactor 1, for example external corona shielding and / or end corona protection, has a lacquer 4 for an electrical machine. The varnish 4 comprises a first polymer resin, first electrically conductive particles 6 dispersed in the first polymer resin, and microcapsules 5 dispersed in the first polymer resin. The microcapsules 5 have in their interior a second polymer resin. It is conceivable that the lacquer comprises an inorganic and electrically non-conductive filler, for example in the form of nanoparticles, wherein the filler is dispersed in the first polymer resin and / or second polymer resin. By the filler, the strength of the corona 1 against partial discharges can be increased.

The microcapsules 5 can be prepared, for example, in a dropping process or by emulsion polymerization. The wall material of the microcapsules 5 may comprise wax, polyurea-formaldehyde and / or polyurethane. The microcapsules 5 may have an average diameter of 10 ym to 1500 ym. The microcapsules 5 may have a wall thickness of 50 nm to 3500 nm.

The coating 4 may be second electrically conductive particles aufwei ^¬ sen, which are arranged in the interior of the microcapsules. 5 It is also conceivable that the second electrically conductive particles are the same in chemical composition as the first electrically conductive particles 6, but a smaller one average diameter than the first electrically conductive particles 6 have. Thus, the second electrically conductive particles can be more easily accommodated in the microcapsules 5. For example, the first electrical have driven conductive particles and / or the second electrically conductive particles of graphite, carbon black and / or inorganic Par ^¬ Tikel with an electrically conductive coating. It is conceivable that the electrical conductivity of the second particles is higher than the electrical conductivity of the first particles. It can thereby be achieved that the electrical conductivity of the cured damaged areas is the same as before the damage despite a lower particle concentration.

The sum of the weight fractions of the microcapsules 5 and the ers ^¬ th semiconductive particles 6 based on the coating 4 is, for example from 10% to 50%. The weight ratio of the microcapsules 5 to the first electrically conductive particles is, for example, from 1 to 10, in particular from 1 to 2.

For example, the first polymer resin and / or the second polymer resin are a copolymer. The copolymer may be, for example, a polymer based on polyacrylate, in particular acrylic acid ester and / or acrylonitrile, and / or polystyrene. It is conceivable that a part of the microcapsules 5 has only one of the monomers of the copolymer and another part of the microcapsules 5 only another one of the monomers of the copolymer. It is thereby achieved that 5 the two monomers come into contact only at a bursting of the micro ^¬ caps and allowed to cure said second polymeric resin.

In another example, the second polymer resin may include a monomer that is disposed only in a part of the microcapsules 5. In another part of the microcapsules 5, a polymerization initiator may be arranged. The polymerization initiator may be dissolved in a solvent. It is thereby achieved that only when the microcapsules 5 burst does the polymerization initiator and the monomer come into contact and thus the second polymer resin cures. The coating 4 may be a reactive diluent such as 3-ethyl-oxetane-3-methanol or cycloaliphatic epoxides, exhibit ^¬. The reactive diluent may be mixed with the first polymer resin and / or with the second polymer resin.

The microcapsules 5 may additionally have electrically non-conductive inorganic nanoparticles in their interior. For example, the nanoparticles Ti0 ₂ , Si0 ₂ , I ₂ O ₃ and / or MgO have or consist of the aforementioned substances. In addition, the microcapsules may have 5 a solvent in their interior, in particular ethanol, n-propaganda nol, isopropanol, ethyl acetate and / or an alkane, insbeson ^¬ particular n-pentane, n-hexane and / or n-heptane. It is conceivable that the corona protection 1 has a porous, electrically non-conductive band, which is impregnated by the coating 4 ^¬ . The tape may have a fabric and / or a nonwoven on ^¬ . The fabric and / or the nonwoven fabric may comprise hollow fibers. The nonwoven fabric and / or the fabric may comprise polyethylene terephthalate (PET), polyester, glass, polyimide, polyaramide, polyamide, polypropylene and / or PTFE.

Figures 1 to 4 show how the corona protection according to the invention in the electrical machine heals itself. The electric machine has an electrical conductor, a main ^¬ insulation, which surrounds the electrical conductor, and the

Corona 1 on. The corona shield 1 has a radial outer side 2 and a radial inner side 3. The corona shield 1 is introduced listed on the radial outer side of the main insulation, so that the radial inner side 3 abuts the radial Au ^¬ ßenseite the main insulation. The radial outer side 2 of the corona shield 1 is in contact with a laminated core of the electrical machine and can be damaged by this touch contact, by external influence and / or by partial discharges, whereby, as shown in Figure 2, a damaged area 7 is formed. As a result of the damage, the microcapsules 5 burst and the second polymer resin located in their interior flows into the damaged area 7, as illustrated by the arrows 8 in FIG. After hardening of the second poly merharzes the damaged area 7 is filled and cured so as Darge ^¬ represents in Figure 4 by the reference numeral 9 is.

Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims

claims

1. Corona protection for an electric machine, with a

Lacquer (4), the first polymer resin, in the first polymer resin dispersed first electrically conductive particles

(6) and microcapsules (5) dispersed in the first polymer resin,

which have in their interior a second polymer resin, wherein the lacquer (4) second electrically conductive particles which are arranged in the interior of the microcapsules (5).

2. corona protection according to claim 1,

wherein the first electrically conductive particles (6) and / or the second electrically conductive particles comprise graphite and / or carbon black.

3. corona protection according to claim 1 or 2,

wherein the sum of the weight fractions of the microcapsules (5) and the first electrically conductive particles (6) relative to the lacquer (4) θΠ 5 "is 6 to 90%.

4. corona protection according to one of claims 1 to 3,

wherein the weight ratio of the microcapsules (5) to the first electroconductive particles is from 1 to 10, especially from 1 to 2.

5. corona protection according to one of claims 1 to 4,

wherein the first polymer resin and / or second polymer resin is a copolymer, wherein the copolymer is in particular a polymer based on polyacrylate, in particular acrylate and / or acrylonitrile, and / or polystyrene,

in particular, the first polymer resin and the second polymer resin are the same.

6. corona protection according to claim 5,

wherein a part of the microcapsules (5) has only one other of the monomers of the copolymer, only one of the monomers of the copolymer and another part of the Mikrokap ^¬ clauses (5).

7. corona protection according to one of claims 1 to 6,

wherein the microcapsules comprise electrically non-conductive inorganic nanoparticle in its interior, insbeson ^¬ particular have the nanoparticles Ti0 _2, Si0 _2, Al ₂ O ₃ and / or MgO.

8. corona protection according to one of claims 1 to 7,

wherein the microcapsules (5) have a solvent in their interior, in particular ethanol, n-propanol, isopro panol, ethyl acetate and / or an alkane, in particular n-pentane, n-hexane and / or n-heptane.

9. corona protection according to one of claims 1 to 8,

wherein the wall material of the microcapsules comprises wax, polyurea-formaldehyde and / or polyurethane.

10. corona protection according to one of claims 1 to 9,

wherein the microcapsules (5) have an average diameter of 10 to 1500 ym ym have, wherein the microcapsules (5) in particular ^¬ sondere have a wall thickness of 50 nm to 3500 nm.

11. Corona protection according to one of claims 1 to 10,

wherein the corona shield (1) has a porous, electrically non-conductive band which is impregnated by the lacquer (4),

in particular the web and / or the fabric comprises polyethylene terephthalate, polyester, glass, polyimide,

Polyaramid, polyamide, polypropylene and / or PTFE on.

12. Electrical machine comprising an electrical conductor, a main insulation, which encloses the electrical conductor, and a corona shield (1) according to one of claims 1 to 11, which is applied to the outside of the main insulation.

13. A method for producing a corona protection (1) according to one of claims 1 to 11,

with the steps:

- applying a lacquer (4) which comprises a first polymer resin, dispersed in the first polymeric resin first electrically conductive particles (6) and dis ^¬ pergierte in the first polymer resin microcapsules (5) having a second polymer resin in its interior to a an electrical conductor enclosing main insulation;

- curing the first polymer resin.

14. The method according to claim 13,

wherein the paint (4) has a solvent outside and within ^¬ half of the microcapsules (5) and the polymer resin is cured by evaporation of the outside of the microcapsules (5) located solvent.