INSULATING SYSTEM MADE OF SOLID INSULATING MATERIAL AND IMPREGNATING RESIN

Abstract

The invention relates generally to the field of insulating electrical conductors against partial discharge in the medium- and high-voltage ranges. In particular, the invention relates to an insulating system for an electric machine, in particular a rotating electric machine such as an electric motor and/or a generator. The invention provides for the first time a substitute for the conventionally used mica as a barrier material in an insulating system, such as the main insulation of rotating electric machines such as motors and/or generators. The substitute is based on a polyether-imide/siloxane copolymer, which can be processed two-dimensionally, for example by surface extrusion. In this way, sheets are produced and, after being processed in sheet form or as a laminate, can be used as planar insulating materials, or cut as strips, in insulating systems.

Claims

1. An insulation system, comprising a solid insulation material in the form of a surface insulation material and a synthetic resin, wherein the surface insulation material is a copolymer of a polyetherimide with a siloxane and the synthetic resin is a thermoset with which the surface insulation material is impregnated and subsequently cured in the form of an encapsulation.

2. The insulation system as claimed in claim 1, wherein the copolymer of polyetherimide and siloxane is a block copolymer.

3. The insulation system as claimed in either of claims 1 and 2, wherein the copolymer has a siloxane content in the range from 0.1% by weight to 90% by weight, based on the total weight of the copolymer.

4. The insulation system as claimed in any of the preceding claims, wherein the copolymer comprises an atomic proportion of silicon atoms in the range from 1% to 25%, based on all atoms in the copolymer.

5. The insulation system as claimed in any of the preceding claims, wherein the copolymer is according to formula (I) ##STR00002## in which R.sup.1-6 are identical or different and are selected from the group of substituted or unsubstituted, saturated, unsaturated or aromatic monocycles having 5 to 30 carbon atoms, substituted or unsubstituted, saturated, unsaturated or aromatic polycycles having 5 to 30 carbon atoms, substituted or unsubstituted, saturated hydrocarbons having 1 to 30 carbon atoms, substituted or unsubstituted, unsaturated hydrocarbons having 2 to 30 carbon atoms; V is a tetravalent linker group selected from the group of substituted or unsubstituted, saturated, unsaturated or aromatic monocycles and polycycles having 5 to 50 carbon atoms, substituted or unsubstituted, saturated hydrocarbons having 1 to 30 carbon atoms, substituted or unsubstituted, unsaturated hydrocarbons having 2 to 30 carbon atoms, and also any combinations of linker groups comprising at least one of the aforementioned groups; g is 1 to 30 and d is 2 to 20.

6. The insulation system as claimed in any of the preceding claims, wherein the surface insulation material includes one or more additives.

7. The insulation system as claimed in any of the preceding claims, wherein the copolymer used is the product available under the trade name Siltem™.

8. The insulation system as claimed in any of the preceding claims, comprising a surface insulation material made from polyetherimide-siloxane copolymer at least in the form of a laminate, a film, in the form of a tape and/or of a tape cut from a laminate.

9. The use of a polyetherimide-siloxane copolymer as surface insulation material and/or as wrapping tape for an insulation system in the medium- and high-voltage range.

10. The use of a polyetherimide-siloxane copolymer as surface insulation material and/or as wrapping tape in electric traction motors.

11. The use of a polyetherimide-siloxane copolymer as surface insulation material and/or as wrapping tape in generators of steam and/or gas turbines.

12. The use of a polyetherimide-siloxane copolymer as surface insulation material and/or as wrapping tape in wind generators.

13. The use of a polyetherimide-siloxane copolymer as surface insulation material and/or as wrapping tape in electric drive motors.

14. The use of a polyetherimide-siloxane copolymer as surface insulation material in the form of a film and/or a laminate as slot lining.

15. The use of a polyetherimide-siloxane copolymer as surface insulation material in the form of a tape as wrapping tape in an electric rotating machine, a motor and/or a generator.

Description

[0037] FIGS. 1 and 2 show the surface of two test specimens comprising insulation systems, in each case illustrating a solid surface insulation material impregnated with a synthetic resin that has been cured after performing impregnation. Both figures show the test specimen after electrical ageing. FIG. 1 illustrates the erosion of the insulation system produced with pure polyetherimide and FIG. 2 illustrates the erosion of the insulation system produced with the polyetherimide-siloxane copolymer of the invention in the form of a solid surface insulation material under the same conditions.

[0038] The defined standard test conditions for electrical ageing according to IEC 60343 are:

[0039] Voltage: 10 kV

[0040] Atmosphere: air 50% RH

[0041] Temperature: Room temperature, approx. 23° C.

[0042] Test duration: 100 hours

[0043] Flow rate: 1000 l*h.sup.−1

[0044] Underneath FIG. 1 there is the key, where it can be seen that in FIG. 1, for the insulation system with pure PEI, under the abovementioned conditions a circle forms around the centrally arranged conductor with an erosion depth, caused by partial discharges, of up to 80 μm, whereas, under the same conditions, the test specimen of FIG. 2, with the insulation system that is produced identically except for the solid insulation material and comprises the copolymer according to the invention as solid insulation material, in the case tested the commercial product Siltem® and/or Ultem® STM 1600 as PEI-siloxane copolymer, also exhibits a circular ageing, but merely with an erosion depth of between −1 μm and −8 μm.

[0045] According to these tests, the present invention delivers a quantum leap in insulation technology, since here for the first time the complex-to-produce and costly mica-containing insulation material can be dispensed with.

[0046] It can be seen that compared to the pure polyetherimide the copolymer brings about an enormous increase, indeed a virtually complete resistance to partial discharge.

[0047] On account of the ascertained partial discharge resistance, the polyetherimide-siloxane copolymer, provided here for the first time as a mica substitute, is suitable as surface insulation material both for wrapping tape insulations and for sheetlike, for example slot lining, insulations, particularly in the use of motors, both for traction and as drive motor, but also for generators such as for example a wind power generator. Its exceptional elongation properties broadens the design scope of—for example—traction motors.

[0048] It is thus an achievable aim to produce both the m-aramid-containing slot linings and also the polyimide-containing insulation tapes with the surface insulation material of the invention made from polyetherimide-siloxane copolymer, without having to make tradeoffs in terms of the power density of the motors or generators. In particular, it is possible in both insulation systems to replace the mica paper and/or mica tape, which each—at least—comprise mica on a carrier, such as for example glass weave, and a tape adhesive for bonding the mica platelets, with the polyetherimide-siloxane copolymer, which inter alia can be processed by surface extrusion.

[0049] A polyetherimide-siloxane film produced for example by surface extrusion insulates for example the coils and/or the wires of the winding of an electric motor. These coils are then inserted into the slots of a laminated core and then impregnated with an impregnation resin, such as for example a polyesterimide and/or a silicone.

[0050] An insulation system according to an embodiment of the present invention for example comprises laminate with one or more films of polyetherimide-siloxane copolymer, also processed for example to give laminates with carriers and/or protective films—bonded for example to m-aramid or polyimide as carrier film.

[0051] The term “film” is understood in the present case to mean a sheetlike layer of a material. The film is a layer and not a layer stack.

[0052] In contrast, a “laminate” is generally a layer stack comprising one or more films. The layers may lie on top of one another in a full-surface manner—that is to say all layers are films—or in a partial-surface manner—that is to say at least one layer has for example a lattice structure and/or randomly distributed fibers and/or grid structure. It may also suffice for laminate formation for a film to be bonded with a weave or a laid scrim, for example a glass fiber laid scrim.

[0053] In the present case, a “laminate” is understood to mean a stack and/or a composite of at least two layers or films, that is to say for example at least one carrier and/or protective film, for example made of m-aramid or polyimide, with at least one film made of the polyetherimide-siloxane copolymer.

[0054] In particular in the case of slot linings, as are found for example in electric motors, wind generators, etc., single films of polyetherimide-siloxane copolymer as surface insulation material may tear, and therefore it is better here to use laminates having relatively tear-resistant films for the use of the polyetherimide-siloxane copolymer as insulation.

[0055] In a further embodiment, the laminates are for example cut into tapes and used in insulation systems.

[0056] In this way, an insulation of a slot for an electric motor may be protected in its entire length also and/or additionally by a surface insulation material made of polyetherimide-siloxane copolymer in a large thickness and/or processed as a laminate, that is to say for example in a composite with for example m-aramid films and/or polyimide films, as slot lining.

[0057] The winding is then inserted into the slots and the whole winding is in turn impregnated with an impregnation resin such as polyesterimide or silicone.

[0058] When producing the surface insulation material as wrapping tape, in particular a tape film is produced for the purpose mentioned here in a thickness in the range from 20 μm to 300 μm, in particular from 25 μm to 200 μm and very preferably in the range from 30 μm to 170 μm. A wrapping tape, for producing the solid portion of a wrapping tape insulation, is then produced from the tape film and is then impregnated with impregnation resin.

[0059] When producing the surface insulation material, for example for slot lining, in particular a film is produced for the purpose mentioned here in a thickness in the range from 12.5 μm to 500 μm, in particular from 25 μm to 450 μm and very preferably in the range from 50 μm to 300 μm. A surface insulation material is then produced from the film, for example by laminating a plurality of films, papers or films of different materials, such as m-aramid films or polyimide films, to produce the solid portion of a slot insulation system, and is then impregnated with impregnation resin.

[0060] Further advantages of the use of a polyetherimide-siloxane copolymer as surface insulation material are for example that [0061] the entire insulation system can be produced much more favorably than with mica-based surface insulation material, [0062] the surface insulation material is thermally resilient from approx. 150° C. to 200° C., [0063] the polyetherimide-siloxane copolymer is also flexible by virtue of its siloxane content, meaning that it can be used as wrapping tape, [0064] electrically, it durably withstands—as tests have shown—the required field strengths, this is because—as has been found in the present case—if in the case of electric field strengths of up to a maximum of 15 kV/mm (!) electrical discharges strike a siloxane or an SiO.sub.2 nanoparticle, a vitrified protective layer forms which significantly increases the lifetime of an electric rotating machine insulated therewith. The vitrified layer thus formed can be readily detected by means of SEM, and in addition elemental analysis by means of EDX is possible in order to detect the silicon in the copolymer, and [0065] it is partial discharge-resistant, as FIG. 2 of the present description shows, which leads to a marked increase in the electrical lifetime.

[0066] As a result of the invention, firstly, a replacement is provided for the conventionally used mica as barrier material in an insulation system such as the main insulation of electric rotating machines such as motors and/or generators. The replacement is based on a polyetherimide-siloxane copolymer which can be processed in sheet form, for example by surface extrusion. Films are produced that are processed in film form or else as laminate, cut as sheetlike insulation materials or as tapes, usable in insulation systems.