RU2574070C2 - Insulating materials with formed holes - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: improved electrically insulating tape (16) is offered which comprises the protective layer (20) and the electrically insulating layer (18) joined with the protective layer (20). At least, one of either the electrically insulating layer (18) or the protective layer (20) includes a set of formed apertures (26) to improve penetration of impregnating pitch into the insulating tape (16) during pitch impregnation.

EFFECT: invention provides optimum impregnation of the tape that improves the ability to resist to impact of voltage and premature breakdown and accident.

10 cl, 11 dwg

Description

FIELD OF THE INVENTION

The present invention generally relates to the field of electrical insulation tapes, and more particularly, to electrical insulation materials and methods for improved resin impregnation of electrical insulation materials.

BACKGROUND OF THE INVENTION

High voltage windings are used in various electrodynamic machines, such as motors or generators. For example, high voltage windings, commonly referred to as stator windings, are used in high voltage electric generators. A high voltage winding, such as a stator winding, may be formed of at least one winding bus, which, in turn, includes one or more electrical conductors. Individual electrical conductors are formed from highly conductive material such as copper. Electrical conductors are usually individually insulated and bonded together to form a winding bus. Such a bundle, in turn, is surrounded by insulation and is often referred to as a winding insulator or a case insulator. A case insulator typically includes multiple layers of insulating tape, such as glass-coated mica tape. The housing insulator is coated with an external conductive ground electrode that surrounds the housing insulator. The external conductive ground electrode may be an electrically conductive paint coating or an electrically conductive tape wrapped around a case insulator. The external conductive ground electrode is connected to earth so that the voltage of the outer surface of the high voltage winding has zero potential.

The tape can be applied with half overlap, butt or in any other suitable way. Typically, many layers of mica tape are wound around the coil, with sixteen or more layers typically used for typical high voltage coils. The number of layers can be reduced depending on the power of the generator and the efficiency of the insulator both in terms of its ability to electrical insulation and in relation to its ability to conduct heat. In order to give the tape a higher abrasion resistance and guarantee a denser insulation, an outer tape made of hard fibrous material, such as fiberglass, asbestos, etc., can be wound around the spool.

The insulation tape is usually impregnated with resin to improve its final properties. There are many ways to coat materials with epoxy resins followed by vulcanization of the product. One such method is vacuum pressure impregnation (VPI). This method is used on devices such as stator coils. An insulating tape is applied to the coils, then the coils are placed in a vacuum chamber in which a vacuum is created. After a certain period of time, resin is impregnated to impregnate the coil. In order to force the resin to enter the coils and minimize voids that affect the conductivity, pressure is applied. After this operation is completed, the coils are heated in order to vulcanize the resin. Another variant of this method, global vacuum impregnation under pressure (GVPI), includes a process in which dry insulated coils are wound, and then the entire stator is subjected to vacuum impregnation under pressure instead of individual coils. Due to the relatively high density of existing insulation tapes, there are usually problems with the optimal impregnation of such tapes, such as incomplete impregnation. Incomplete impregnation may result in the coil being unable to withstand the stress and cause premature breakdown and accident.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is explained in the following description with reference to the drawings, which show:

FIG. 1 shows an insulation tape wound around a stator coil in accordance with one aspect of the present invention.

FIG. 2 depicts an insulating tape having a plurality of apertures formed therein in accordance with one aspect of the present invention.

FIG. 3 shows an insulation tape having a plurality of apertures oriented parallel to the longitudinal axis of the insulation tape in accordance with one aspect of the present invention.

FIG. 4 depicts an insulation tape having a plurality of apertures oriented at an angle to the longitudinal axis of the insulation tape in accordance with one aspect of the present invention.

FIG. 5A-5E show exemplary patterns for apertures in insulating tape in accordance with one aspect of the present invention.

FIG. 6 depicts an insulating tape having a plurality of apertures that extend through the insulating layer and into, but not through, the protective layer in accordance with one aspect of the present invention.

FIG. 7 shows an insulating tape having an insulating layer with a plurality of apertures and a protective layer with a plurality of apertures that are offset from the apertures of the insulation layer in accordance with one aspect of the present invention.

FIG. 8 depicts a structurally stable mica sheet (without a protective layer) having a plurality of apertures formed therein, in accordance with one aspect of the present invention.

FIG. 9 depicts a laser source for forming a plurality of apertures in an insulating tape in accordance with one aspect of the present invention.

FIG. 10 depicts a system for forming a plurality of apertures in an insulating tape in accordance with one aspect of the present invention.

FIG. 11 depicts another system for forming a plurality of apertures in an insulating tape in accordance with one aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The inventors of the present invention have innovatively developed an insulating tape that substantially improves the penetration of the impregnating resin into the insulating tape during its impregnation with the resin. In one embodiment, the insulating tape includes at least an insulating layer and a plurality of apertures (holes) formed therein by laser drilling and the like. In some embodiments, the largest aperture size is ten microns or less, so that the penetration of the impregnating resin into the tape can be improved without compromising the electrical performance of the insulation tape. Thus, improved insulation tapes not only improve resin impregnation, but are also able to withstand the stresses and forces experienced by the tapes during production and service.

Turning now to the drawings, FIG. 1 shows exemplary operating conditions for the insulation tapes of the present invention. An exemplary coil 10 includes a plurality of turns of conductors 12 that are assembled into a Bakelized coil 14. Housing insulation for the coil 14 is provided by winding one or more layers of electrical insulation tape (insulation tape) 16 around the Bakelized coil 14. The insulation tape 16 typically includes a layer of electrical insulation (insulating layer) 18, combined or bonded to the protective layer or protective sheet 20 using a liquid resinous binder 22.

In one embodiment, the insulating layer 18 includes a plurality of mica flakes that have been molded into a mica plate using conventional papermaking processes known in the art. Mica is known to be a desirable insulator due to the size of mica flakes and plates. The mica can be standard mica (muscovite, phlogopite), biotite mica, or any other suitable mica-like aluminosilicate materials such as kaolinite, halloysite, montmorillonite and chlorite. The size ranges for forming mica can be different, but usually the mica is in the macro range of thickness (for example, 0.01-0.05 mm) with the longest plate sizes up to 10 mm for natural and traditionally processed mica (including all known common mineral forms ) For synthetic micas, the longest size can be in the micron and submicron ranges from 100 nm to 10,000 nm. Mica is not only good at forming paper, but also due to the fact that the plates create highly sinuous paths for the formation of a tree-like conductive trace, it is also an excellent electrical insulating material. Unfortunately, mica is also a very good heat insulator, which is an undesirable side effect.

In another embodiment, insulation tape 16 may further include high thermal conductivity (HTC) materials 24 that can be combined with mica at any suitable mica paper production stage, for example, a dry material stage, a pulp stage, or at the stage of the final product, as described in US patent No. 7846853, which is fully incorporated herein by reference. Mica papers typically have structures that can easily include materials with high thermal conductivity, such as metal oxides, nitrides and carbides, monomeric and polymeric organic compounds, to give composite materials with high dielectric strength. High thermal conductivity materials 24 may be included in place of or in addition to the resin which is applied to the insulation tape 16.

High thermal conductivity materials 24 may include any suitable particles that increase the thermal conductivity of the receiving matrix. Materials with high thermal conductivity may include nano-, meso- and / or micro-sized particles. In one embodiment, materials with high thermal conductivity include nanofillers having a size of from 1 to 1000 nm. The nanofillers may be spherical, may be plates, may be a shape having a large aspect ratio, such as spiral contact springs, rods or nanotubes, and / or may be in assembled forms, such as aggregates, fibrillar dendrites, ropes, bundles, nets and other forms. High thermal conductivity materials 24 may also include coatings, such as diamond-like coatings or other high thermal conductivity materials, such as metal oxides, nitrides, and carbides, which are located on materials with lower thermal conductivity. Further, particles with high thermal conductivity can include inorganic or organic surface functional groups that are reactively grafted to materials with high thermal conductivity, which can form direct or indirect covalent bonds (compounds) with the impregnating resin in order to form a continuous composite material . In one embodiment, materials with high thermal conductivity are connected directly to the impregnating resin via one or more covalent bonds. Specific examples of suitable materials with high thermal conductivity are disclosed in US patent No. 7781063, which is fully incorporated herein by reference.

The impregnating resin used to impregnate the insulation tape 16 may be any suitable resin or epoxy resin, including modified epoxy resins, polyesters, polyurethanes, polyimides, polyamide esters, polyamide esters, bismaleimides, organosilicon materials, polysiloxanes, polybutadiene, cyanoacids etc., as well as homogeneous mixtures of these resins. In addition, the impregnating resin may include additives, such as crosslinkers, accelerators, and other catalysts and substances to improve technological properties. Some resins, such as liquid crystal thermosets (LCT) and 1,2-vinyl polybutadiene combine low molecular weight with good crosslinking properties.

The insulating layer 18 is usually combined with a flexible protective layer 20 (protective layer 20) using a resinous binder 22. The flexible protective layer 20 may include, for example, fiberglass fabric or polyethylene glycol terephthalate reinforcing mat. The resinous binder 22 may be any suitable binder, such as an epoxy material, as is known in the art.

As mentioned above, the insulating tape 16 may be applied half-overlapping, butt-on, or in any other suitable manner around a suitable conductor. Typically, a plurality of layers of insulating tape 16 are wound around a Bakelized coil 14, with sixteen or more layers typically used for typical high voltage coils. The number of layers can be reduced depending on the power of the generator and the efficiency of the insulator both in terms of its ability to electrical insulation and in relation to its ability to conduct heat. After that, the insulating tape 16 is usually impregnated with resin in order to improve many of its overall properties. In one embodiment, the impregnation is performed using a vacuum pressure impregnation process (VPI) or global pressure vacuum impregnation (GVPI).

The insulating tapes of the present invention significantly improve the penetration of the impregnating resin into the tape during its impregnation with resin. In FIG. 2 shows an embodiment of an improved insulation tape, for example, insulation tape 16, in accordance with one aspect of the present invention. The insulation tape 16 includes at least an insulating layer 18 and a plurality of apertures 26 formed therein and located at a certain distance from each other. The apertures can be of any size suitable for a particular application. In one embodiment, the apertures 26 are sized to provide the necessary resistance to electric field voltage. In a particular embodiment, the apertures 26 have a maximum size of ten microns (10 μm) or less. For example, in one embodiment, the apertures 26 have a diameter (D) (as shown in FIG. 2) of ten microns (10 μm) or less, to maintain the structural and electrical integrity of the mica sheet and to provide improved resin impregnation.

In addition to this, it is very important that the depth of the apertures 26 can also be controlled in order to avoid a through piercing of the mica or, conversely, to provide it, if desired. Accordingly, in any of the embodiments described herein, the depth of the apertures can be controlled so that the apertures 26 partially or completely pass only through one of the insulating layer 18 or the protective layer 20 to the desired depth. In further embodiments, apertures 26 can be formed in both the insulating layer 18 and the protective layer 20, but without the apertures 26 having such a depth that they extend completely through the insulating layer 18 and through the protective layer 20. In other embodiments, the apertures 26 pass through both the insulating layer 18 and the protective layer 20. It should be understood, however, that in the last embodiment, the apertures 26 must be small enough in diameter, and in order for such a system to function properly, it must be Call impregnating resin with relatively low viscosity.

In addition, the apertures 26 can be of any suitable shape in order to provide improved penetration of the resin through the insulation tape 16. In one embodiment, the apertures 26 are relatively round in shape, as also shown in FIG. 2. The relatively round shape helps to provide improved permeability of the resin insulating tape 16. In another embodiment, as shown in FIG. 3, apertures 26 are substantially oval or elongated. It should be noted that the size of the apertures 26, as shown in the drawings, need not be scaled, but enlarged for clarity.

Further, the apertures 26 may have any desired orientation with respect to the longitudinal axis 28 of the insulating tape 14. In one embodiment, as shown in FIG. 3, at least a portion of the apertures 26 are oriented parallel to the longitudinal axis 28 of the insulation tape 16. In another embodiment, as shown in FIG. 4, the apertures 26 can be oriented obliquely, for example, at an angle of 45 degrees relative to the longitudinal axis 28 of the insulation tape 14. The apertures 26 can cover any suitable surface area of the insulation tape 14.

Apertures 26 may be provided in the insulating tape 16 with any suitable pattern that will help improve the penetration of the impregnating resin into the insulating tape 16, while maintaining its dielectric strength and structural strength. FIG. 5A-5E illustrate exemplary aperture patterns 26 for insulating tape 16. As shown in FIG. 5A, for example, apertures 26 may be formed in the insulating tape 16 in the form of a diagonal pattern 30 with the largest aperture size 26 oriented parallel to the longitudinal axis 28 of the insulating tape 16. As shown in FIG. 5B, the apertures 26 can be formed in the insulating tape 16 in the form of a diagonal pattern 32 with the largest aperture size 26 oriented at an angle of, for example, 45 ° to the longitudinal axis 28 of the insulating tape 16. As shown in FIG. 5C, apertures 26 may be formed in the insulating tape 16 in the form of a zigzag pattern 34. As shown in FIG. 5D, apertures 26 may include a frame 36 (apertures formed along the edge of the tape 16) such that a tight overlap of the insulation tape 16 will use the frame 36 to provide apertures 26 in each layer of the insulation tape 16 in the wrap. As shown in FIG. 5E, the insulating tape 16 may also include centering 38, which will be more advantageous for half overlap windings. Alternatively, the apertures 26 can be arranged in any other desired order in order to increase the permeability of the insulating tape 16 with an impregnating resin, including, but not limited to, nets and strips. Different types of patterns are not mutually exclusive and can be combined with each other.

It is further provided that when the insulating tape 16 includes an insulating layer 18 and a protective layer 20, the apertures 26 described herein can be included in one or both of the insulating layer 18 and the protective layer 20. In one embodiment of the aperture 26 are formed exclusively in the insulating layer 18, as shown, for example, in FIG. 2, and not in the protective layer 20. In another embodiment, the apertures 26 are formed exclusively in the protective layer 20, but not in the insulating layer 18.

In yet another embodiment, the apertures 26 are formed in the insulating layer 18 and in the protective layer 20. When the apertures 26 are formed in both the insulating layer 18 and the protective layer 20, the apertures 26a in the insulating layer 18 and the apertures 26b in the protective layer 20 relative to each other in any suitable configuration. In one embodiment, as shown in FIG. 6, apertures 26a in the insulating layer 18 and apertures 26b in the protective layer 20 are substantially aligned with each other in a vertical plane. In a further embodiment, as shown in FIG. 7, apertures 26a in the insulating layer 18 and apertures 26b in the protective layer 20 may be substantially non-aligned with each other in a vertical plane.

It should be understood that the present invention is not limited to insulating tapes having an insulating layer and a protective substrate material. In some aspects of the present invention, as shown in FIG. 8, the insulating layer 16 may be provided as a standalone, single layer, structurally stable sheet 40 without a protective layer 20. The structurally stable sheet 40 may have a plurality of apertures 26 formed therein, as in any embodiment described above. The sheet 40 may be formed from mica or any other suitable insulating material, and may or may not include materials with high thermal conductivity, as described herein. Optionally, after the apertures 26 are formed in the sheet 40, the sheet 40 can be combined with the protective backing material (with or without apertures), as described herein, for example, with the protective layer 20, and glued to it with a liquid resinous binder substance.

In accordance with another aspect of the present invention, there is provided a method for producing an insulating material in any embodiment described herein. The insulation material may include insulation tape 16 or structurally stable mica sheet 40, as described above. The method includes forming a plurality of apertures 26 in the insulating material. In one embodiment, the apertures 26 have a predetermined diameter and depth. The formation of apertures can be performed using any suitable method known in the art, for example using mechanical rollers with spikes or using laser drilling. In one embodiment, the formation of apertures is performed using laser drilling. Laser drilling removes material from the insulating material, creating apertures 26. The wavelength and intensity of the laser radiation can be chosen so as to interact with the insulating material in a controlled manner, which will be clear to specialists in this field of technology.

In accordance with another aspect of the present invention, laser drilling can selectively remove components (e.g., the first component) from the insulating material, e.g., from the insulation tape 16 or structurally stable sheet 40, leaving other components (e.g., the second component) substantially intact. It is understood that the laser wavelength will have a significant effect, since the reflectivity of one component, for example a material with high thermal conductivity, such as boron nitride, can be very different from the reflectivity of the second component, such as mica. Therefore, the power required for the evaporation / removal of the material can be very different, for example, for materials with high thermal conductivity and mica. The methods described herein optionally include selectively removing components, such as mica or materials with high thermal conductivity, from a substrate, for example, from insulating tape 16 or from structurally stable sheet 40, leaving another component, such as materials with high specific thermal conductivity thermal conductivity or mica, essentially intact.

Laser drilling can be performed, for example, by hammer drilling or by cutting circular grooves. In hammer drilling, the beam focuses on a substrate, for example, on an insulating tape 16, into a spot equal to the diameter of the aperture to be formed. When cutting circular grooves, the laser can move relative to the substrate in order to form apertures with the desired diameter and depth. Suitable laser drilling equipment is available from a variety of sources, including, but not limited to, U.S. Laser Corp., Wyckoff, NJ.

In one embodiment, as shown in FIG. 9, a beam 42 from a laser source 44 is directed onto an insulating material (eg, an insulating tape 16) and a plurality of apertures 26 are formed in the insulating tape 16, while the insulating tape 16 is held in a stationary position. In another embodiment, as shown in FIG. 10, the insulating material moves along the conveyor to provide a continuous source of insulating material, and apertures 26 are formed in the insulating material as the insulating material passes the laser source 44. For example, in one embodiment, a roll 46 of insulating material, such as an insulating tape 16 is provided as a feed source for the strip of insulating tape 16. One or more rollers 48 can be provided to guide the insulating tape 16 from the roll 46 to the laser source 44. In another embodiment (not shown), the insulating layer 18 and the protective layer 20 are separately supplied from separate rolls and can be connected together before or after contact of any layer with the laser beam 42 of the laser source 44. In any of the options described herein the implementation of the depth of the apertures can be controlled so that the apertures are partially or completely formed individually either in the insulating layer 18, or in the protective layer 20, or in both layers. The depth of the apertures can also be controlled in such a way as to avoid a through piercing of mica, or, conversely, to guarantee a through piercing. When the insulating material is transported past the laser source 44, it is generally understood that more powerful laser sources are likely to have a repetition rate of not more than 1 kHz, which is likely to limit the maximum possible speed of transportation of the insulating material.

The laser source 44 may be a fiber optic laser source or any other suitable laser source known in the art. In operation, the laser source 44 directs the beam onto the insulation tape 16 in order to form a plurality of apertures 26 in the insulation tape 16. It will be understood that one skilled in the art will understand that the speed of movement of the insulation material, as well as the wavelength, pulse duration and the pulse frequency of the laser source can be changed as necessary in order to form holes 26 in the insulating material having the desired size, including, but not limited to, the desired shape, height, width inu and / or depth. To obtain apertures 26 having a circular shape, a movable mirror 50 may be provided in order to direct the laser beam 42 from the laser source 44 onto the insulating material, for example onto the insulation tape 16, and to form a circular shape as the insulation tape 16 is transported past the laser source 44, as shown in FIG. eleven.

In addition to the above considerations, one skilled in the art will appreciate that the amount of diffraction, the choice of a particular laser source, and the selected wavelength of the laser source 44 will affect the number and size of apertures 26. Further, the number and dimensions of apertures 26 may depend on the shape the beam of the laser source 44 and any structures that help create the desired beam shape.

The laser source 44 and these structures can be adapted to provide circular, ellipsoidal, and cylindrical intensity profiles using various structures known in the art. For example, the "natural" beam profile of excimer lasers, as a rule, has a cylindrical rather than a Gaussian profile. In one embodiment, the laser beam 42 undergoes spatial filtering and then focuses on the insulating material in order to make a single spot or aperture. The minimum spot size is approximately equal to the laser wavelength, but this minimum worsens the more, the more the spot moves away from the Gaussian profile. In another embodiment, the localization of a single spot can be controlled by moving insulating material, such as insulating tape 16, or by moving the laser beam 42 through swinging mirrors that scan along and across the insulating material. In another embodiment, the laser beam 42 is guided through a cylindrical lens in order to form a line that can then be directed toward the insulating material. In yet another embodiment, the laser beam 42 passes through a mask in which there are many holes. This passage generates many rays that can be focused by the lens, providing many holes on the insulating material, for example on the insulating tape 16.

In accordance with another aspect of the present invention, there is a method for using any embodiment of an insulation tape 16 described herein having a plurality of apertures 26 formed therein. The method includes winding the insulation tape 16 around an electrical conductor and impregnating the insulation tape 16 with an impregnating resin. A plurality of apertures 26 in the insulation tape 16 provides improved resin penetration while maintaining the structural stability and dielectric strength of the insulation tape 16.

While various embodiments of the present invention have been shown and described herein, it is obvious that such embodiments are given by way of example only. Numerous variations, changes, and substitutions can be made without departing from the invention described herein. Accordingly, it is intended that the present invention be limited only by the spirit and scope of the appended claims.

Claims (10)

1. An electrically insulating material comprising an electrically insulating layer including a plurality of apertures formed therein, in which the apertures have a maximum size of ten microns or less, and in which the electrically insulating layer includes mica. 2. The insulating material according to claim 1, wherein the insulating material is in the form of a structurally stable mica sheet. 3. The insulating material according to claim 1, wherein the plurality of apertures has a depth such that it only partially passes through the insulating layer. 4. The electrically insulating material according to claim 1, wherein the electrically insulating layer further comprises a plurality of fillers with high thermal conductivity (NTS). 5. The electrical insulating material according to claim 1, wherein said electrical insulating material comprises an electrical insulating tape. 6. A method of manufacturing an electrically insulating material, including:
- forming a plurality of apertures in the electrically insulating material, wherein said electrically insulating material contains a first component and a second component, said formation comprising selectively removing the first component from the electrically insulating material, while leaving the second component substantially intact, and the electrically insulating material contains an insulating layer containing mica. 7. The method of claim 6, wherein the apertures have a maximum size of ten microns or less. 8. The method of claim 6, wherein the electrical insulating material includes an electrical insulating tape including an insulating layer connected to the protective layer, and in which apertures are formed in each of the insulating layer and the protective layer. 9. The method according to p. 6, in which the formation of apertures is carried out by laser drilling. 10. The method of claim 6, wherein the second component comprises a material with high thermal conductivity.

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