Insulating material and winding for electrical machines

Abstract: In an insulating material used for the winding of electrical machines, a high thermoconductive insulating film 11 is formed around the outer periphery of the wound conductors 10, using a high thermoconductive insulating tape 1 which comprises a mica layer 3, a reinforcement layer 5, and a high thermoconductive filler layer 7. The resin content in each of the mica layer 3 and the high thermoconductive filler layer 7 is the range of 10 to 25 % by weight of the total weight of the material.

Description: Background of the invention The present invention relates to an insulating material and to a winding for electric rotary machines comprising an insulating film composed of such insulating material. Conventionally, insulating films for electrical windings used in electric rotary machines have been formed with an insulating material such as disclosed in JP-A-63-110929 (1988). That is, the insulating material comprising a mica layer, a reinforcement layer, a filler layer including fillers having a high thermal conductivity therein, and resin contained in each layers has been used. The insulating material was wound around the outer periphery of the wound conductors, and the insulating film for windings of electrical machines was formed by curing the resin in the insulating material under a pressurized state. EP 0 266 602 A1 discloses a winding for electric rotary machines which uses an insulating material as set forth in the first part of claim 1. An insulating film for windings of electrical machines formed as described above with the insulating material as described above did not have any problem as long as it was used for electric rotary machines operated at low voltage. However, when it was used for electric rotary machines operated at high voltage such as commercial power generators, high voltage motors, and the like, electrical defects have been readily generated, and its electrical characteristics had a tendency to be deteriorated. In view of the above problems, the inventors of the present invention studied the reasons for the electrical defects. They found that one reason was the following: When forming the insulating film for windings of electrical machines, part of fine bubbles contained in any of the mica layers, filler layers, and the resin was not removed but remained in the insulating material. This was caused by an insufficient flow of impregnated resin in the insulating film during the pressurizing process when forming the insulating film for windings of electrical machines, because the resin content in each of the mica layer and the filler layer was not maintained at an appropriate content. Summary of the invention It is an object of the present invention to provide an insulating material which makes it possible to obtain an insulating film for windings of electrical machines of superior electric characteristics. The invention meets this object by the insulating material set forth in claim 1. The mica layer comprises mica flakes and/or mica particles, the reinforcement layer comprises a reinforcing material, for instance, glass cloth, and the filler layer comprises a filler having a thermal conductivity of at least 5 W/m•K, for instance, alumina. The insulating material is a laminated body of these layers in the order mica layer, reinforcement layer, filler layer, or filler layer, mica layer, reinforcement layer. The insulating material comprises a resin, for instance, epoxy resin. The total content of the resin contained in the insulating material is in the range of 20-50 % by weight of the total weight of the insulating material, and the resin content in each of the mica layer and the filler layer is in the range of 10-25 % by weight of the total weight of the insulating material. A resin content in each of the mica layer and the filler layer of at least 10 % by weight of the total weight of the insulating material is necessary in order to remove the fine bubbles contained in each of the mica layer and the filler layer in the pressurizing process. If the resin content in each of the mica layer and the filler layer exceeds 25 % by weight of the total weight of the insulating material, the operability in winding the insulating material onto the conductor is decreased, and the insulating material is wrinkled. A resin content in each of the mica layer and the filler layer in the range 10-25 % by weight of the total weight of the insulating material is suited to achieve desired electric characteristics, for instance, an alternating insulation breakdown voltage of 26.5-29.0 kV/mm. The insulating material of the present invention is further specified by the fact that the difference between the resin content in the mica layer and that in the filler layer is equal to or less than 10 % by weight. If this difference exceeds 10 % by weight, part of the resin containing the fine bubbles to be removed is transferred from the layer having a large resin content to the layer having a small resin content, and remains therein in the pressurizing process when forming the insulating film for windings of electrical machines. In accordance with the windings for electrical machines relating to the present invention, the insulating film is formed with an insulating material comprising a high dielectric strength layer, a reinforcement layer, and a thermoconductive layer, and the resin content in respective of the high dielectric strength layer and the thermoconductive layer is in the range of 10-25 % by weight, respectively, of total weight of the insulating material. The high dielectric strength layer is a mica layer comprising mica flakes. The reinforcement layer is a layer comprising a reinforcement material, for instance, glass cloth. The thermoconductive layer is a filler layer comprising a filler having a thermal conductivity of at least 5 W/m·K, for instance, alumina. Each of the layers comprises a resin, for instance, epoxy resin. Total resin content is in the range of 20-50 % by weight of the total weight of the insulating material, and the resin content of the each layer of the mica layer and the filler layer is in the range of 10-25 % by weight of the total weight of the insulating material. The difference of the resin content in the mica layer from the resin content in the filler layer is equal to or less than 10 % by weight. The insulating film for windings of electrical machines is formed using the insulating material as follows: First, insulated conductors are wound several times for forming a wound conductor. Then, the insulating material is wound around the outer periphery of the wound conductor so that either the mica layer or the filler layer is closest to the wound conductor. Subsequently, a releasing agent is applied onto the outer periphery of the insulating material. A shape forming jig is attached to the winding, and an external force is applied to the surface via the jig. Then, the insulating film is formed by heating at a designated temperature for curing the resin in the insulating material and removing the fine bubbles contained therein. Brief description of the drawings FIG. 1 is a cross sectional view indicating the material structure of the high thermoconductive insulating tape of the embodiment of the present invention; FIG. 2 is a perspective view indicating the structure of the windings for electrical machines of the embodiment of the present invention; FIG. 3 is a perspective view for explaining a manufacturing process of the windings for electrical machines of the embodiment of the present invention; FIG.4 is a cross sectional view of the generator; and FIG.5 is a perspective view showing the stator slots. Detailed explanation of the preferred embodiments of the invention Hereinafter, an embodiment of the present invention is explained referring to drawings. A structure of material for the high thermoconductive insulating tape (high thermoconductive preimpregnated tape) of the embodiment of the present invention is explained hereinafter referring to FIG. 1a. The high thermoconductive insulating tape 1 comprises a laminated body, wherein a mica layer 3 (high dielectric strength layer) comprising a small mica flakes sheet 2, a reinforcement layer 5 comprising glass cloth 4, and a high thermoconductive filler layer (thermoconductive layer) comprising alumina particles 6 are laminated in the order of the above description. The laminated body also may be formed by laminating in the order of the high thermoconductive filler layer 7, the mica layer 3, and the reinforcement layer 5 as shown in Fig.1b. The high thermoconductive insulating tape 1 also contains the resin 8 in each of the mica layer 3, the reinforcement layer 5, and the high thermoconductive filler layer 7, and the total content of the resin 8 is 31.4 % by weight of the total weight of the high thermoconductive insulating tape 1. The resin content in the mica layer 3 is 12.9 % by weight of the total weight of the high thermoconductive insulating tape 1, and the resin content in the high thermoconductive filler layer 7 is 15.0 % by weight of the total weight of the high thermoconductive insulating tape 1. The high thermoconductive insulating tape 1 was prepared as follows: First, a small mica flakes foil 2 (weight; 165 g/m 2 ) manufactured by a paper making machine with small mica flakes dispersed in water, and a glass cloth 4 (weight; 35 g/m 2 ) were prepared. A resin 8 composed by mixing BF 3 monoethylamine 3 parts by weight into novolak type epoxy resin 100 parts by weight was impregnated into the small mica flakes foil 2 and the glass cloth 4, and a small mica flakes sheet (a laminated body of the mica layer 3 and the reinforcement layer 5) was obtained by adhering the small mica flakes foil 2 and the glass cloth 4. The resin 8 composed by mixing BF 3 monoethylamine 3 parts by weight into the novolak type epoxy resin 100 parts by weight, and alumina particles 6 were mixed so that a weight ratio of the alumina particles 6 to the resin 8 became 2:1. After adding methylethylketone of 10 % by weight, the resin was applied onto the side plane of the reinforcement layer 5 of the small mica flakes sheet by a coater so that the applied amount of the resin became 256 g/m 2 . Then, the high thermoconductive insulating sheet was obtained by evaporating and removing the methylethylketone. The high thermoconductive insulating tape 1 was obtained by slitting the high thermoconductive insulating sheet to 30 mm wide by a slitter. A structure of winding for electrical machines in the embodiment of the present invention is explained hereinafter referring to FIG. 2. The winding for electrical machine 9 comprises a wound conductor 10 formed by winding plural insulating conductors 10a, and high thermoconductive insulating film 11 formed at the outer peripheral portion of the wound conductor 10. The windings for electrical machines 9 was prepared as follows: First, a plurality of the insulated conductors 10a are wound several times for forming a wound conductor, as indicated in FIG. 2. Then, the high thermoconductive insulating tape 1 indicated in FIG. 1 was wound around the outer periphery of the wound conductor. At this time, the high thermoconductive insulating tape 1 could be wound irrelevant to either of the mica layer 3, or the high thermoconductive filler layer 7 is closest to the wound conductor 10, but in the present embodiment, the high thermoconductive insulating tape 1 was wound at the outer periphery of the wound conductors 10 so that the mica layer 3 was to be closest to the wound conductor 10. Subsequently, a releasing tape 12 was wound around the outer periphery of the high thermoconductive insulating tape 1. The reason to wind the releasing tape 12 at the outer periphery of the high thermoconductive insulating tape 1 is to prevent a shape forming jig, which would be explained later, from adhering to the high thermoconductive insulating tape 1. Subsequently, a shape forming jig was attached to the wound conductor 10 as indicated in FIG. 3, and an external force was applied from the surface via the jig. Then, the high thermoconductive insulating film 11 was formed by heating at a designated temperature for curing the resin 8 in the high thermoconductive insulating tape 1 with removing the fine bubbles contained in the high thermoconductive insulating tape 1 with a part of the resin 14 in the high thermoconductive insulating tape 1, and the winding for electrical machines 9 was obtained. The windings 9 for electrical machines of the present embodiment manufactured as above are assembled into core slot of electric rotary machines such as power generators, motors, and the like. Figs. 4 and 5 is a cross sectional view showing a generator, and the winding 9 is inserted into slots 50 of the generator. The generator comprises a stator frame 100 supporting a bearing 20, a stator mounted on the stator frame 100 and a rotor composed of a rotor core 60 and rotatably mounted by the bearing 20 in the stator. The stator has a stator core 30, and the winding 9 inserted into the slots 50 is used as a stator coil 40. As shown in Fig.5, the stator coil 40 is assembled into the slots 50 and fixed by a spring 60 of fibrous glass reinforced plastics between the slots 50 and stator coil 40. A sheet 70 and spring 90 of fibrous glass reinforced plastics are sandwitched between a wedge 80 and the stator to fix the stator winding 40 in the slots 50. Next, results of tests on the alternating break down voltage of the windings for electric machines of the present embodiment and of windings for electric machines of the comparative example are explained based on Table 1. The windings for electric machines of the comparative example used in the tests were manufactured with high thermoconductive insulation formed by high thermoconductive insulating tape, which was prepared by the following process. First, a small mica flakes foil 2(weight; 165 g/m 2 ) manufactured by a paper making machine with small mica flakes dispersed in water, and a glass cloth 4 (weight; 35 g/m 2 ) were prepared. A resin composed by mixing BF 3 monoethylamine 3 parts by weight into novolak type epoxy resin 100 parts by weight was impregnated into the small mica flakes foil 2 and the glass cloth 4, and a small mica flakes sheet (a laminated body of the mica layer 3 and the reinforcement layer 5) was obtained by adhering the small mica flakes foil 2 and the glass cloth 4. The resin composed by mixing BF 3 monoethylamine 3 parts by weight to the novolak type epoxy resin 100 parts by weight, and alumina particles were mixed so that a weight ratio of the alumina particles to the resin became 3.5:1. After adding methylethylketone of 10 % by weight, the resin was applied onto the side plane of the reinforcement layer 5 of the small mica flakes sheet by a coater so that the applied amount of the resin became 230 g/m 2 . Then, the high thermoconductive insulating sheet was obtained by evaporating and removing the methylethylketone. The high thermoconductive insulating tape 1 was obtained by slitting the high thermoconductive insulating sheet to 30 mm wide by a slitter. The total resin content in the high thermoconductive insulating tape of the comparative example manufactured as above was 19. 3 % by weight of the total weight of the high thermoconductive insulating tape. The resin content in the mica layer was 19. 3 % by weight of the total weight of the high thermoconductive insulating tape, and the resin content in the high thermoconductive filler layer was 10. 4 % by weight of the total weight of the high thermoconductive insulating tape. The windings for electrical machines 9 was prepared using the high thermoconductive insulating tape manufactured as above. The method of manufacturing was as same as the present embodiment. Its explanation is omitted. In the test on the alternating break down voltage, an aluminum foil was wound respectively around the outer periphery of the windings for electrical machines of the present embodiment and of the comparative example as an electrode, and the alternating break down voltages were measured by supplying an alternating voltage between the aluminum electrode and the winding conductor of each of windings for electrical machines. The results were as shown in Table 1. Results of measuring insulation break down voltage Embodiment Comparative example Observed values (kV/mm) 26.5 19.0 29.0 17.5 27.5 21.5 Average (kV/mm) 27.7 19.3 As indicated in Table 1, the windings for electric machines of the present embodiment had higher alternating break down voltage than the windings for electric machines of the comparative example. This was, because the high thermoconductive insulating film of the winding for electrical machines was formed using the high thermoconductive insulating tape, wherein the resin content in each of the mica layer and the high thermoconductive filler layer was specified to the range of 10-25 % by weight of the total weight of the material, and because fine bubbles contained in the high thermoconductive insulating tape could be removed sufficiently with a part of the resin in the high thermoconductive tape in the pressurizing process during forming the high thermoconductive insulating film of the windings for electrical machines. Accordingly, because the windings for electrical machines of the present embodiment is provided with a dense high thermoconductive insulating film superior in electrical characteristics, a high reliability can be provided to the electric rotary machines operated with a high voltage. In accordance with the insulating material relating to the present invention, the high thermoconductive insulating film superior in electrical characteristics can be obtained, because the resin content in each of the mica layer and the high thermoconductive filler layer is specified to the range of 10-25 % by weight of the total weight of the material, and fine bubbles contained in the high thermoconductive insulating tape can be removed sufficiently with a part of the resin in the high thermoconductive tape in the pressurizing process during forming the high thermoconductive insulating film of the windings for electrical machines. In accordance with the resin content specified as above, decrease of workability and causing wrinkles to the insulating material during winding the wound conductors with the insulating material can be prevented. Therefore, generation of voids in the insulating film of the windings for electrical machines, which will cause an electrical defect, can be prevented; and the high thermoconductive insulating film superior in electrical characteristics can be obtained. In accordance with the insulating material relating to the present invention, the high thermoconductive insulating film superior in electrical characteristics can be obtained. Because difference of the resin content in the mica layer from the resin content in the filler layer is specified equal to 10 % by weight or less, a part of the resin including fine bubbles therein, which should be removed outside, can be prevented from entering and remaining into the one layer of smaller resin content from the other layer of larger resin content. In accordance with the windings for electrical machines relating to the present invention, the highly reliable windings for electrical machines having the insulating film superior in electrical characteristics, and the electrical characteristics, which will not be deteriorated even if the windings are used in any electric rotary machines, can be obtained. Because the insulating film is formed using the insulating material, wherein the resin content in each of the mica layer and the high thermoconductive filler layer is specified to the range of 10-25 % by weight of the total weight of the insulating material, fine bubbles contained in the high thermoconductive insulating tape can be removed sufficiently with a part of the resin in the high thermoconductive tape in the pressurizing process during forming the high thermoconductive insulating film of the windings for electrical machines. If the insulating film is formed using the insulating material, wherein the resin content is specified to the range as above, decrease of workability and causing generation of wrinkles to the insulating material during winding the wound conductors with the insulating material can be prevented. Therefore, generation of voids in the insulating film of the windings for electrical machines, which will cause an electrical defect, can be prevented; and the highly reliable windings for electrical machines having the high thermoconductive insulating film superior in electrical characteristics, and the electrical characteristics, which will not be deteriorated even if the windings are used in any electric rotary machines, can be obtained. In accordance with the windings for electrical machines relating to the present invention, its insulating film is formed using the insulating material; wherein, because the difference of the resin content in the mica layer from the resin content in the filler layer is specified equal to 10 % by weight or less, a part of the resin including fine bubbles therein, which should be removed outside, can be prevented from entering and remaining into the one layer of smaller resin content from the other layer of larger resin content; and the highly reliable windings for electrical machines having the high thermoconductive insulating film superior in electrical characteristics, and the electrical characteristics, which will not be deteriorated even if the windings are used in any electric rotary machines, can be obtained.

Claims: An insulating material comprising a mica layer (3), a reinforcement layer (5), and a filler layer (7), characterised in that the resin content in said mica layer (3) and in said filler layer (7) is in the range of 10 to 25 % by weight of the total weight of said insulating material, wherein the resin content in said mica layer (3) differs from that in said filler layer (7) by 10 % by weight or less. The insulating material of claim 1, wherein the resin contents in the mica layer (3) and in the filler layer (7) are substantially equal. The insulating material of claim 1, wherein the total resin content in said insulating material is in the range of 20 to 50 % by weight of the total weight of said insulating material. The insulating material of claim 1, wherein said filler layer (7) comprises a filler material having a thermal conductivity of at least 5 W/m·K. The insulating material of claim 1, wherein said reinforcement layer (5) has two surfaces, said mica layer (3) is formed on one surface of said reinforcement layer (5), and said filler layer (7) is formed on the other surface of said reinforcement layer (5), or on said mica layer (3). A winding for electrical machines comprising an insulating film (11) composed of an insulating material according to any one of claims 1 to S. The winding of claim 6, wherein said high dielectric-strength layer (3) is placed closer to a wound conductor (10) than said thermoconductive layer (7) and said reinforcement layer (5). The winding of claim 6, wherein said thermoconductive layer (7) is placed closer to a wound conductor (10) than said high dielectric-strength layer (3) and said reinforcement layer (5). The winding of claim 6, wherein the resin content in said high dielectric-strength layer (3) and in said thermal conductive layer are such that the alternating insulation breakdown voltage of said insulating film (11) is in the range of 26.5 to 29.0 kV/mm. An electric rotary machine provided with a winding according to any one of claim 6 to claim 9.

Inventors: AMAGI SHIGEO, HONDA TATSUO, MORIKAWA KEIICHI, ONODA MITSURU, TSUNODA TOMOYA, AMAGI, SHIGEO, HONDA, TATSUO, MORIKAWA, KEIICHI, ONODA, MITSURU, TSUNODA, TOMOYA
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1999
Main classification: H02K3
IPC codes: H01B7, H01F5, H01B3, H02K3, H01B17