Varnish impregnated fixed coil, stator using coil, and rotating electric machine

Abstract

To provide a varnish impregnated fixed coil capable of ensuring both electrical insulation and mechanical vibration resistance even when there are larger temperature changes and mechanical vibrations than before, a stator using the coil, and a rotating electric machine using the coil.SOLUTION: A disclosed varnish impregnated fixed coil is a coil in which the conductor and insulating tape are impregnated and fixed with insulating varnish. The insulating tape is a dry mica tape or a prepreg mica tape made by laminating an insulating base material and mica paper. The cured insulating varnish is a rubber or elastomer.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to the technology of electromechanical devices using coils and cores, and particularly to a varnish-impregnated and fixed coil impregnated and fixed with an electrical insulating varnish, a stator using the coil, and a rotating electrical machine using the coil.

Background Art

[0002] In recent years, from the perspective of global environmental protection, reducing the emissions of greenhouse gases (e.g., carbon dioxide gas) has become an urgent issue, and the application fields of electromechanical devices using coils and cores (e.g., rotating electrical machines and transformers) tend to expand. Along with the expansion of the application fields, the requirements for higher output and smaller size of the electromechanical devices are increasing.

[0003] Taking a rotating electrical machine as an example of an electromechanical device, the power input to the coil is increasing in high power for higher output, and the rotation speed is increasing for smaller size. And in order to cope with the increase in power, an increase in the cross-sectional area of the coil conductor is required, and in order to cope with the smaller size, a reduction in the thickness of the electrical insulation layer is required.

[0004] In addition, since the mechanical vibration of the rotating electrical machine increases due to the increase in the rotation speed, measures against mechanical vibration are also necessary. This is because if cracks occur in the electrical insulation layer or peeling occurs between the electrical insulation layer and the coil conductor due to the mechanical vibration of the rotating electrical machine, partial discharge is likely to occur, leading to electrical insulation breakdown. Furthermore, the increase in power promotes the partial discharge. That is, in order to achieve both higher power and higher rotation speed of the rotating electrical machine, electrical insulation means for ensuring both electrical insulation properties and mechanical vibration resistance in the coil is important.

[0005] Various techniques have been proposed to address such problems. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2019-029475) discloses an electric device coil including a conductor, an insulating tape wound around the conductor, and a curable resin portion impregnated with the conductor wound with the insulating tape. The insulating tape contains silicone composite particles formed from a core of silicone rubber particles and a shell of silicone resin particles, and the surface of the silicone composite particles has a plurality of irregularities. An electric device coil is taught.

[0006] According to Patent Document 1, it is said that silicone composite particles having a plurality of irregularities on the surface can improve the stress resistance of the insulating tape, and can provide an electric device coil in which the crack resistance of the insulating portion composed of the insulating tape and the curable resin portion is improved (the occurrence of cracks is suppressed).

[0007] Also, in an electric device coil, in order to improve the resistance to thermal breakdown and cracking of the insulating material, conventionally, insulating materials added with additives such as high heat-resistant mica, high thermal conductivity crystalline silica, and high toughness core-shell rubber have been proposed. However, when the addition amount increases, there is a problem that the additives tend to aggregate and precipitate in the resin before curing.

[0008] To address this problem, Patent Document 2 (Japanese Patent Application Laid-Open No. 2020-045417) discloses an electric device having an insulating material including a resin, mica, particles, and core-shell rubber particles, wherein the particles are disposed around the mica, and the core-shell rubber particles are disposed around the mica and the particles.

[0009] According to Patent Document 2, it is said that an electric device can be provided that achieves prevention of aggregation and precipitation of additives in the insulating material, improvement of the heat resistance of the insulating material, and prevention of electrical and mechanical breakdown.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

[0011] Currently, various research and developments are being carried out to further expand and advance the scope of application of electromechanical devices (especially rotating electrical machines) using coils and cores. For example, their application as power sources in logistics vehicles, construction machinery, ships, aircraft, etc. is being considered. These vehicles are exposed to harsher environments than before in terms of temperature changes and mechanical vibrations, so it is required that the rotating electrical machine serving as the power source can operate with high reliability even under such harsh environments.

[0012] The present invention has been made to address the above problems. Therefore, the primary object of the present invention is to provide a varnish-impregnated fixed coil that achieves both ensuring electrical insulation within the coil and ensuring vibration resistance against larger temperature changes and mechanical vibrations than before. Further, the secondary object is to provide a stator and a rotating electrical machine that can operate with high reliability even under environments with larger temperature changes and mechanical vibrations by using the varnish-impregnated fixed coil. [Means for Solving the Problems]

[0013] (I) One aspect of the present invention is a coil in which a segment conductor and an electrical insulation tape are impregnated and fixed with an electrical insulation varnish, wherein the electrical insulation tape is a dry mica tape or a prepreg mica tape in which an insulation base material and mica paper are laminated, and the cured electrical insulation varnish is rubber or an elastomer, and provides a varnish-impregnated fixed coil characterized by the above.

[0014] In the varnish-impregnated and fixed coil (I) according to the present invention, the following improvements and modifications can be freely combined and added. (i) The cured electrical insulating varnish has an elastic modulus at room temperature of 0.1 MPa or more and 100 MPa or less. (ii) The cured electrical insulating varnish has a hardness of 10 or more and 100 or less as measured by a Type E durometer conforming to JIS K 6253-3:2012.

[0015] (II) Another aspect of the present invention is a stator having a varnish-impregnated and fixed coil, wherein the varnish-impregnated and fixed coil is the above-described varnish-impregnated and fixed coil. A stator is provided.

[0016] (III) Still another aspect of the present invention is a rotating electrical machine including a stator having a varnish-impregnated and fixed coil, wherein the varnish-impregnated and fixed coil is the above-described varnish-impregnated and fixed coil. A rotating electrical machine is provided.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a varnish-impregnated and fixed coil that achieves both ensuring electrical insulation and ensuring vibration resistance within the coil even against larger temperature changes and mechanical vibrations than in the past. Further, by using the varnish-impregnated and fixed coil, it is possible to provide a stator and a rotating electrical machine that can operate with high reliability even in an environment with larger temperature changes and mechanical vibrations than in the past. Other problems, configurations, and effects than those described above will be clarified by the description of the embodiments described below.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

[0019] [Basic Idea of the Present Invention] The present invention and the like have studied how to achieve both ensuring electrical insulation and ensuring vibration resistance within a coil against larger temperature changes and mechanical vibrations than in the past. As a result of intensive research, contrary to the conventional technical idea of firmly fixing a stator coil with an electrical insulating varnish of a thermosetting resin, it has been found that by the reverse technical idea of configuring the electrical insulating varnish with an elastic body, it is possible to absorb / relieve the thermal stress caused by large temperature changes and the mechanical stress caused by large mechanical vibrations. The present invention has been completed based on this finding.

[0020] Hereinafter, embodiments according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to the described specific embodiments, and it is possible to appropriately combine with known technologies or improve based on known technologies without departing from the technical idea of the invention. Also, substantially synonymous configurations may be given the same reference numerals, and duplicate explanations may be omitted.

[0021] [Embodiments of the Present Invention] FIG. 1 is a schematic cross-sectional view showing a structural example of a stator according to the present invention. In a rotating electrical machine, a rotor (not shown) is disposed radially inside the stator of FIG. 1. Note that the cross-section means a cross-section orthogonal to the rotation axis direction of the rotating electrical machine (a cross-section whose normal line is parallel to the axial direction). A rotating electrical machine is a general term for an electric motor and a generator.

[0022] As shown in Fig. 1, the stator 10 of the present invention has stator coils wound around a plurality of stator slots 12 formed on the inner peripheral side of the iron core 11, and the stator coils are the varnish-impregnated fixed coils 20 of the present invention. Although not shown, the varnish-impregnated fixed coil 20 is wound so as to straddle between different stator slots 12.

[0023] The stator coil is usually composed of a plurality of segment coils 21 (one electrically insulated coil), and the varnish-impregnated fixed coil 20 of the present invention is one in which at least one segment coil 21 is impregnated and fixed with an electrical insulating varnish. Details of the varnish-impregnated fixed coil 20 will be described later.

[0024] The segment coil 21 will be described. Fig. 2 is a schematic diagram showing an example of the segment coil, and is (A) an overall schematic diagram and (B) an enlarged cross-sectional schematic diagram.

[0025] The long portions extending left and right shown in Fig. 2(A) are the portions inserted into the stator slots 12 of the iron core 11, and each is inserted into a different stator slot 12. One end (here, the left side of the paper) of the segment coil 21 is formed so as to be folded back while being twisted outside the stator slot 12, and the other end side (here, the right side of the paper) is joined to another segment coil 21 while being twisted outside the stator slot 12.

[0026] Also, as shown in Fig. 2(B), the segment coil 21 has the outer periphery of the segment conductor 22 covered with an electrical insulating tape 23. The segment conductor 22 is often composed of a conductor in which a plurality of strands are twisted together, but the present invention is not limited thereto. It is preferable that each of the strands constituting the segment conductor 22 is also electrically insulated. For example, an enameled wire electrically insulated by an enamel coating is used.

[0027] The electrical insulation tape 23 (which may also be abbreviated as the insulation tape) will be described. FIG. 3A is a schematic cross-sectional view of a dry mica tape which is a type of electrical insulation tape, and FIG. 3B is a schematic cross-sectional view of a prepreg mica tape which is another type of electrical insulation tape. The dry mica tape 23a and the prepreg mica tape 23b both have a tape shape and are shaped to be easily wound around the segment conductor 22.

[0028] As shown in FIG. 3A, the dry mica tape 23a has a structure in which an insulating base material 24 and a mica paper 25 are laminated (adhesively fixed) by an adhesive 26. The insulating base material 24 mechanically reinforces the brittle mica paper 25. The insulating base material 24 is selected in consideration of the required heat resistance and electrical insulation properties, and an inorganic base material (for example, glass cloth) or an organic base material (for example, polyethylene terephthalate film, polyimide film, cellulose paper, aramid paper, non-woven fabric) is used.

[0029] Since the mica paper 25 has a high dielectric breakdown voltage and high heat resistance, it is one of the insulating materials that are very useful in rotating electrical machines with high voltage specifications. However, since it is mechanically brittle due to its paper shape, it is preferably used by laminating it with the above-mentioned insulating base material 24. There is no particular limitation on the type of mica paper (the properties of mica), and conventional ones (for example, those using integrated mica, those using flake mica) can be used as appropriate.

[0030] There is no particular limitation on the adhesive 26 as long as the required heat resistance can be ensured, and conventional ones can be used as appropriate. Note that the heat resistance required for the adhesive 26 means the higher of the heat resistance required for the stator and the rotating electrical machine and the heating temperature when impregnating and curing the electrical insulation varnish.

[0031] The prepreg mica tape 23b basically has the same structure as the dry mica tape 23a as shown in FIG. 3B, but is different from the dry mica tape 23a in that the mica paper 25 is impregnated with the electrical insulating varnish 27 and the insulating varnish is in a semi-cured state. The electrical insulating varnish 27 used here is preferably the same as the electrical insulating varnish used in the varnish impregnation fixing coil 20 described above.

[0032] Also, in the prepreg mica tape 23b, the electrical insulating varnish 27 may be used as a substitute for the adhesive 26. In other words, the mica paper 25 may be impregnated with the electrical insulating varnish 27 and laminated with the insulating base material 24, and the insulating varnish may be in a semi-cured state to bond the insulating base material 24 and the mica paper 25. Further, when the insulating base material 24 is made of a porous material (a material having many voids, such as glass cloth, cellulose paper, aramid paper, non-woven fabric, etc.), it is preferable to impregnate the void region of the insulating base material 25 with the electrical insulating varnish 28 and make the insulating varnish in a semi-cured state.

[0033] The electrical insulating varnish 27 used in the present invention has fluidity in the state before curing and becomes rubber or elastomer in the cured state. Specifically, the electrical insulating varnish 27 preferably has a viscosity of 20 Pa·s or less at room temperature (for example, 20°C) in the state before curing, and an elastic modulus of 0.1 MPa or more and 100 MPa or less at room temperature (for example, 20°C) in the cured state. Also, the hardness (hardness measured by type E durometer in accordance with JIS K 6253-3:2012) in the cured state is preferably 10 or more and 100 or less.

[0034] By using the electrical insulating varnish 27 having the above properties (here, viscosity, elastic modulus, hardness), impregnability, defoaming property, adhesion property, and vibration absorption property can be ensured.

[0035] Note that chemical reactions (crosslinking reactions) that form a three-dimensional crosslinked structure in elastomers such as rubber and elastomers are roughly classified into condensation reactions and addition reactions. Crosslinking by a condensation reaction is liable to cause volume shrinkage due to the departure of molecules, and has a weakness that bubbles may be generated / remain due to the departed molecules. Volume shrinkage and generation / remainder of bubbles in the electrical insulation layer are feared to lead to arc discharge. On the other hand, crosslinking by an addition reaction has fewer of those weaknesses.

[0036] Therefore, it is preferable to use a rubber or an elastomer that crosslinks by an addition reaction for the electrical insulating varnish 27 used in the present invention. For example, SYLGARD TM 184 silicone elastomer, DOWSIL TM SH 850 LTV, DOWSIL TM SE 1816 CV, DOWSIL TM SE 1817 CV M, etc. can be preferably used. The heat treatment conditions for heat-curing the electrical insulating varnish 27 may be appropriately adjusted according to the characteristics of the rubber or elastomer used. For example, in the case of DOWSIL TM SE 1817 CV M, heat treatment holding at 100 °C for 1 hour can be preferably used.

[0037] FIG. 4 is an example of an enlarged cross-sectional schematic view of the slot region of the stator. FIG. 4 shows an example in which two segment coils 21 are wound around one stator slot 12.

[0038] In FIG. 4, a slot liner 13 is disposed between the side walls of the stator slot 12 (the circumferential walls of the iron core 11, the left and right walls in the figure) and the segment coil 21, and the slot inner insulating material 14 is disposed so as to sandwich each segment coil 21 in the radial direction of the iron core 11 (at the upper and lower positions in the figure). Further, a wedge 15 is disposed at the opening of the stator slot 12 on the inner peripheral side of the iron core 11 (the upper position in the figure).

[0039] The slot liner 13 is arranged with the intention of more surely providing electrical insulation (ground insulation) between the segment coil 21 and the iron core 11. Further, it also has the effect of preventing damage to the electrical insulating tape 23 when the segment coil 21 is inserted into the stator slot 12. As the slot liner 13, for example, a polyethylene terephthalate film, a polyimide film, cellulose paper, aramid paper, non-woven fabric, etc. can be suitably used.

[0040] The in-slot insulating material 14 is arranged with the intention of more surely providing electrical insulation (ground insulation) between the segment coil 21 and the iron core 11 and electrical insulation (phase insulation) between the segment coils 21. Further, it also has the effect of more surely fixing the segment coil 21. As the in-slot insulating material 14, for example, glass fiber reinforced resin (GFRP) etc. can be suitably used.

[0041] The wedge 15 is arranged with the intention of more surely fixing the segment coil 21 and the in-slot insulating material 14. As the wedge 15, for example, glass fiber reinforced resin (GFRP) etc. can be suitably used.

[0042] Note that the present invention is not limited to the configurations (structures and presence / absence) of these slot liner 13, in-slot insulating material 14, and wedge 15. In other words, in the present invention, part or all of the slot liner 13, in-slot insulating material 14, and wedge 15 may not be arranged.

[0043] (Method for manufacturing a stator) The method for manufacturing a stator according to the present invention is different from the prior art in that the aforementioned electrical insulating varnish 27 (an insulating varnish that becomes rubber or elastomer in a cured state) is used as the electrical insulating varnish for impregnating and fixing the stator coil. Other parts may be the same as the prior art.

[0044] There are roughly three methods for manufacturing the stator (a method of impregnating and fixing the stator coil). Hereinafter, the case where the segment conductor 22 constituting the segment coil 21 is composed of a twist of a plurality of strands will be described as an example.

[0045] (1) One-piece injection method (full impregnation method) This method is suitable when the stator 10 is relatively small (not so huge).

[0046] First, a segment conductor preparation step S1 of preparing a segment conductor 22 in which insulated strands are twisted and bundled is performed. Next, a segment coil forming step S2a of winding a dry mica tape 23a around the outer periphery of the segment conductor 22 and processing it into a coil shape to form a segment coil 21 is performed.

[0047] Next, a stator winding forming step S3a of inserting the segment coil 21 into the stator slot 12 of the iron core 11 to form a stator winding is performed. In the stator winding forming step S3a, if necessary, a slot liner 13, an in-slot insulating material 14, and a wedge 15 are incorporated.

[0048] Next, the entire stator winding (the one in which the segment coil 21 is incorporated into the iron core 11) is immersed in an electrical insulating varnish in a pre-cured state (flowing state), and an electrical insulating varnish impregnation step S4a of impregnating the insulating varnish into the void region of the stator winding (particularly, the void region in the stator slot 12, including the void regions of the insulating base material 24 and mica paper 25) is performed. The electrical insulating varnish used at this time is the electrical insulating varnish 27 which is a feature of the present invention. There is no particular limitation on the impregnation method of the electrical insulating varnish 27, and a conventional method (for example, vacuum pressure injection) can be appropriately used.

[0049] Next, an electrical insulating varnish curing step S5a of performing heat treatment on the stator winding impregnated with the electrical insulating varnish 27 to cure the insulating varnish is performed. The segment coil 21 fixed by varnish impregnation through the electrical insulating varnish curing step S5a becomes a kind of varnish impregnation fixed coil 20 according to the present invention.

[0050] Next, a segment coil joining step S6 of electrically joining the segment coils 21 of the stator winding is performed. Thereby, the stator 10 according to the present invention is completed. Note that the segment coil joining step S6 may be performed before the electrical insulation varnish impregnation step S4a.

[0051] (2) Single injection method This method is suitable for the stator 10 of a huge rotating electrical machine such as a high-voltage and large-output generator used in a power plant. When the stator 10 is relatively large (so-called huge), the method of immersing and impregnating the entire stator winding in an electrical insulation varnish as in the above-described integral injection method has a large cost disadvantage. Therefore, impregnation fixing of the electrical insulation varnish is performed on each segment coil, and the obtained varnish-impregnated and fixed coil is incorporated into the stator slots 12 of the iron core 11 to manufacture the stator 10.

[0052] First, in the same manner as described above, a segment conductor preparation step S1 and a segment coil formation step S2a are performed.

[0053] Next, the segment coil 21 is immersed in an electrical insulation varnish in a state before curing (flowing state), and an electrical insulation varnish impregnation step S3b of impregnating the insulation varnish into the void region of the segment coil 21 (particularly including the void region between the segment conductor 22 and the electrical insulation tape 23, and the void regions of the insulation base material 24 and mica paper 25) is performed.

[0054] Next, a heat treatment is performed on the segment coil 21 impregnated with the electrical insulation varnish 27 to cure the insulation varnish, and an electrical insulation varnish curing step S5b is performed. The segment coil 21 fixed by varnish impregnation through the electrical insulation varnish curing step S5b becomes a kind of varnish-impregnated and fixed coil 20 according to the present invention.

[0055] Next, a stator winding forming step S3b is performed in which the varnish-impregnated and fixed coil 20 is inserted into the stator slot 12 of the iron core 11 to form a stator winding. In the stator winding forming step S3b, the slot liner 13, the in-slot insulating material 14, and the wedge 15 are incorporated as necessary.

[0056] Next, a segment coil joining step S6 is performed in which the segment coils 21 of the stator winding are electrically joined to each other. Thus, the stator 10 according to the present invention is completed.

[0057] (3) Prepreg method Similar to the single injection method, this method is also a suitable method for the stator 10 of a huge rotating electrical machine such as a high-voltage and large-output generator used in a power plant. This method differs from the single injection method in that a prepreg mica tape 23b is used as the electrical insulation tape 23 of the segment coil 21 and the electrical insulation varnish impregnation step S3b is not essential.

[0058] First, similar to the above, a segment conductor preparation step S1 is performed. Next, a segment coil forming step S2b is performed in which the prepreg mica tape 23b is wound around the outer periphery of the segment conductor 22 and processed into a coil shape to form the segment coil 21.

[0059] Next, an electrical insulation varnish curing step S5c is performed in which the segment coil 21 using the prepreg mica tape 24b is heat-treated to cure the insulating varnish. The segment coil 21 impregnated and fixed with varnish through the electrical insulation varnish curing step S5c becomes a kind of the varnish-impregnated and fixed coil 20 according to the present invention.

[0060] Thereafter, similar to the single injection method, a stator winding forming step S3b and a segment coil joining step S6 are performed. Thus, the stator 10 according to the present invention is completed.

[0061] The above-described embodiments have been described to assist in the understanding of the present invention, and the present invention is not limited to the specific configurations described. For example, it is possible to replace a part of the configuration of the embodiment with a configuration within the common general knowledge of those skilled in the art, and it is also possible to add a configuration within the common general knowledge of those skilled in the art to the configuration of the embodiment. That is, with respect to a part of the configuration of the embodiment in this specification, it is possible to delete, replace with other configurations, or add other configurations without departing from the technical idea of the invention.

Description of Reference Numerals

[0062] 10... Stator, 11... Core, 12... Stator Slot, 13... Slot Liner, 14... Insulating Material in Slot, 15... Wedge, 20... Varnish-Impregnated Fixed Coil, 21... Segment Coil, 22... Segment Conductor, 23... Electrical Insulating Tape, 23a... Dry Mica Tape, 23b... Prepreg Mica Tape, 24... Insulating Base Material, 25... Mica Paper, 26... Adhesive, 27... Electrical Insulating Varnish.

Claims

1. A coil in which a segment conductor and an electrical insulating tape are impregnated and fixed with an electrical insulating varnish, wherein the electrical insulating tape is a dry mica tape or a prepreg mica tape obtained by laminating an insulating base material and mica paper, and the cured electrical insulating varnish is a rubber or an elastomer, characterized in that it is a varnish-impregnated and fixed coil.

2. In the varnish-impregnated and fixed coil according to Claim 1, the cured electrical insulating varnish is characterized in that its elastic modulus at room temperature is 0.1 MPa or more and 100 MPa or less, which is a varnish-impregnated and fixed coil.

3. In the varnish-impregnated and fixed coil according to Claim 1, the cured electrical insulating varnish is characterized in that its hardness measured by a Type E durometer conforming to JIS K 6253-3:2012 is 10 or more and 100 or less, which is a varnish-impregnated and fixed coil.

4. In the varnish-impregnated and fixed coil according to Claim 2, the cured electrical insulating varnish is characterized in that its hardness measured by a Type E durometer conforming to JIS K 6253-3:2012 is 10 or more and 100 or less, which is a varnish-impregnated and fixed coil.

5. A stator having a varnish-impregnated and fixed coil, wherein the varnish-impregnated and fixed coil is the varnish-impregnated and fixed coil according to any one of Claims 1 to 4, which is a stator.

6. A rotating electric machine including a stator having a varnish-impregnated and fixed coil, wherein the varnish-impregnated and fixed coil is the varnish-impregnated and fixed coil according to any one of Claims 1 to 4, which is a rotating electric machine.

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