Insulating varnish composition, insulating varnish cured product, coil, and method for manufacturing coil

Abstract

The insulating varnish composition has: a thermosetting resin (15) including at least one resin among an unsaturated polyester resin, an epoxy resin, and a vinyl ester resin, which contains a high molecular weight body having a weight average molecular weight greater than or equal to 2000; and a liquid bubble forming component having a standard state vapor pressure of a gas greater than or equal to 1 mmHg and less than 80 mmHg.

Description

Technical Field

[0001] This invention relates to an insulating varnish composition, a cured insulating varnish product after curing the insulating varnish composition, a coil having the cured insulating varnish product, and a method for manufacturing the coil. Background Technology

[0002] Traditionally, rotating machines such as electric motors, generators, and compressors have coils formed by winding wires around a stator core. In these coils, to ensure electrical insulation, protect the wires, and secure the wires to the stator core, processes such as wire self-fusion bonding, molding with resin, and insulating varnish treatment are employed. In the insulating varnish treatment, an insulating varnish composition is impregnated into the gaps between the wires in the coil; therefore, insulating varnish compositions containing low-viscosity thermosetting resins are widely used.

[0003] The insulating varnish composition is required to impregnate the gaps between the coil wires. On the other hand, the cured insulating varnish, prepared by heating the insulating varnish composition, must prevent insulation damage caused by partial discharge occurring between the coil wires. Generally, increasing the thickness of the insulating coating layer on the wires and increasing the distance between the wires are effective methods for suppressing partial discharge between the coil wires, but both may lead to a decrease in the output of the rotating machine.

[0004] As a technique to suppress partial discharge between coil wires without reducing the output of the rotating machine, a technique has been developed that reduces the relative permittivity of the cured insulating varnish by forming bubbles in it, thereby increasing the partial discharge inception voltage (PDIV) of the cured insulating varnish. For example, Patent Document 1 discloses a technique for obtaining a bubble-containing cured insulating varnish by adding a microencapsulated foaming agent to a thermosetting resin.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-33433 Summary of the Invention

[0006] The larger the bubbles contained in the cured insulating varnish, the easier it is for partial discharge to occur within the bubbles, and therefore the easier it is for the insulation of the cured insulating varnish to break down. However, Patent Document 1 did not consider the miniaturization of the bubbles, so the effect of suppressing the occurrence of partial discharge within the bubbles may be insufficient.

[0007] The present invention was made in view of the above circumstances, and its object is to obtain an insulating varnish composition capable of suppressing the occurrence of partial discharge of air bubbles in the cured insulating varnish.

[0008] To address the aforementioned issues and achieve the objectives, the insulating varnish composition of the present invention comprises: a thermosetting resin containing at least one of an unsaturated polyester resin, an epoxy resin, and a vinyl ester resin having a weight average molecular weight greater than or equal to 2000; and a liquid bubble-forming component having a vapor pressure in a standard gas state greater than or equal to 5 mmHg and less than 40 mmHg, wherein the thermosetting resin contains a polymerization initiator with a 1-minute half-life temperature less than or equal to 180°C.

[0009] The effects of the invention

[0010] According to the present invention, it has the effect of suppressing the occurrence of partial discharge of air bubbles in the cured insulating varnish. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view of the rotating machine involved in Embodiment 1 cut along its central axis.

[0012] Figure 2 It is a cross-sectional view of the rotating machine according to Embodiment 1 cut in a direction orthogonal to the central axis, and is a partially enlarged cross-sectional view showing the stator.

[0013] Figure 3 This is a partially enlarged cross-sectional view schematically showing the wire and the cured insulating varnish involved in Embodiment 1. Detailed Implementation

[0014] The insulating varnish composition, the cured insulating varnish, the coil, and the method for manufacturing the coil according to the embodiments will now be described in detail based on the accompanying drawings.

[0015] Implementation method 1.

[0016] Figure 1 This is a cross-sectional view of the rotating machine 1 according to Embodiment 1, cut along the central axis C. The rotating machine 1 has a stator 2, a rotor 3, a shaft 4, a frame 5, and two brackets 6. The stator 2 is formed into a cylindrical shape based on the central axis C. Hereinafter, when describing the directions of each structural element of the rotating machine 1, the direction parallel to the central axis C is defined as the axial direction, the direction orthogonal to the central axis C is defined as the radial direction, and the rotation direction centered on the central axis C is defined as the circumferential direction.

[0017] Rotor 3 is disposed inside stator 2. A gap is provided between stator 2 and rotor 3 throughout the entire circumference. Shaft 4 is connected to the center of rotor 3. Shaft 4 is coaxially disposed with respect to the central axis C of stator 2. Rotor 3 can rotate about the central axis C. Frame 5 forms the outer contour of rotating machine 1 and houses stator 2 and rotor 3. Frame 5 is formed as a cylindrical shape with openings at both ends along the axial direction. One bracket 6 is configured to block the opening at one end of frame 5 along the axial direction. Another bracket 6 is configured to block the opening at the other end of frame 5 along the axial direction. One end of shaft 4 protrudes outward from frame 5 through a hole 6a formed in a bracket 6.

[0018] The stator 2 has a stator core 7 formed by stacking multiple electromagnetic steel plates and a coil 10 formed by winding wires 11 around the stator core 7. Figure 2 This is a cross-sectional view of the rotating machine 1 according to Embodiment 1, cut in a direction orthogonal to the central axis C, and is a partially enlarged cross-sectional view showing the stator 2. The stator core 7 has a core seat 7a in the shape of a cylinder formed by magnets, and teeth 7b protruding from the inner circumferential surface of the core seat 7a toward the radial direction. Figure 2 In the figure, only one tooth 7b is shown, but in reality, multiple teeth 7b are arranged circumferentially at equal angles. Slots 8 are formed between adjacent teeth 7b.

[0019] An insulator 9 is provided within the slot 8. The insulator 9 is positioned between the stator core 7 and the coil 10 to electrically insulate them. The insulator 9 covers the surface of the core seat 7a opposite to the slot 8 and the surface of the tooth 7b opposite to the slot 8. A coil 10 is formed by winding a wire 11 around the tooth 7b with the insulator 9 in between. A gap G is formed between adjacent wires 11. Furthermore, the stator 2 is not limited to the example shown in the figure; any known stator may be appropriately selected. Additionally, insulating tape or interleaved paper may be provided between adjacent coils 10 in each slot 8.

[0020] Figure 3 This is a partially enlarged cross-sectional view schematically showing the wire 11 and the cured insulating varnish 14 according to Embodiment 1. The wire 11 is an insulated wire with conductive conductor 12 covered by an insulating film 13. The material of the conductor 12 is not particularly limited as long as it is conductive, for example, copper. The material of the insulating film 13 is not particularly limited as long as it is electrically insulating, for example, polyamide-imide. The cured insulating varnish 14 is disposed in the gap G between adjacent wires 11.

[0021] The cured insulating varnish 14 serves the following purposes: it fills the gap G between adjacent wires 11, preventing insulation damage to the wires 11 caused by partial discharge occurring between them; it protects the wires 11; and it secures the wires 11 to the stator core 7. The cured insulating varnish 14 contains a thermosetting resin 15 and air bubbles 16. The cured insulating varnish 14 is produced by heating and curing an insulating varnish composition. The composition of the insulating varnish composition used in the cured insulating varnish 14 will be described in detail below.

[0022] The insulating varnish composition comprises: a thermosetting resin 15, which includes at least one resin selected from unsaturated polyester resin, epoxy resin, and vinyl ester resin containing a high molecular weight body with a weight average molecular weight greater than or equal to 2000; and a bubble-forming component of a liquid, the vapor pressure of which under standard gas conditions is greater than or equal to 1 mmHg and less than 80 mmHg. In this specification, the weight average molecular weight of the thermosetting resin 15 before curing can be determined by existing known methods such as gel permeation chromatography (GPC), and can be obtained from the relative average molecular weight. Furthermore, in this specification, the vapor pressure of the bubble-forming component refers to the equilibrium vapor pressure that can be determined by existing known methods such as the static method, boiling point method, and differential scanning calorimetry (DSC). The standard gas conditions described in this specification are assumed to be conditions where the reference temperature is set to 25°C and the standard pressure is set to 100 kPa (SATP).

[0023] Unsaturated polyester resin, epoxy resin, and vinyl ester resin function to improve the impregnation of the insulating varnish composition into the gap G between the wires 11 before curing, and to improve the heat resistance, electrical insulation, and bonding strength to the stator core 7 of the cured insulating varnish 14 after curing. The thermosetting resin 15, the main agent of the insulating varnish composition, is primarily composed of oligomers, polymers, etc., with a weight average molecular weight greater than or equal to 2000. Therefore, compared to the case of curing from monomers, the thickening effect accompanying the progress of the curing reaction occurs earlier. Thus, the effect of immobilizing the bubbles 16 generated by the vaporization of bubble-forming components within the cured insulating varnish 14 is achieved. When the weight average molecular weight is less than 2000, since the thickening of the thermosetting resin 15 requires time, the number of bubbles 16 in the cured insulating varnish 14 decreases and the diameter of the bubbles 16 increases. From the viewpoint of balancing the impregnation properties of the insulating varnish composition and the refinement of air bubbles 16 in the cured insulating varnish 14, a weight average molecular weight greater than or equal to 5000 and less than 20000 is more preferable. The proportion of high molecular weight components with a weight average molecular weight greater than or equal to 2000 in the thermosetting resin 15 is preferably greater than or equal to 20 parts by weight and less than 90 parts by weight per 100 parts by weight of the thermosetting resin 15. If the proportion of high molecular weight components with a weight average molecular weight greater than or equal to 2000 is within the aforementioned range, both the impregnation properties of the insulating varnish composition and the effect of suppressing partial discharge between wires 11 caused by air bubbles 16 in the cured insulating varnish 14 can be achieved.

[0024] Unsaturated polyester resin is obtained by mixing a main agent, which is an unsaturated polyester component with an average molecular weight of 2000 or more and has two or more unsaturated bonding sites in the molecule, with a reactive diluent added in any proportion.

[0025] The types of unsaturated polyester components are not particularly limited as long as they can be obtained by polymerizing unsaturated polyacids or their anhydrous forms, polyols, and any saturated polyacids or their anhydrous forms. They can be appropriately selected from known unsaturated polyester components.

[0026] Examples of unsaturated polycarboxylic acids or their anhydrous derivatives include anhydrous maleic acid, maleic acid, fumaric acid, citracic acid, itaconic acid, and methylcyclohexene-1,2-dicarboxylic anhydride. These unsaturated polycarboxylic acids can be used individually or in combination of two or more.

[0027] Examples of polyols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, pentanediol, hexanediol, and bisphenol A. These polyols can be used individually or in combination of two or more.

[0028] Examples of saturated polycarboxylic acids or their anhydrous derivatives include isophthalic acid, phthalic acid, phthalic anhydride, terephthalic acid, succinic acid, adipic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, and bicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride. These saturated polycarboxylic acids can be used individually or in combination of two or more.

[0029] The reactive diluent is formulated to improve the impregnation properties and cross-linking structure of the insulating varnish composition. Therefore, its type is not particularly limited if it has a low viscosity compared to the unsaturated polyester component and has one free radical polymerizable group in its molecule; it can be appropriately selected from known reactive diluents. Examples of reactive diluents include styrene, vinyltoluene, hydroxyethyl methacrylate, and diethylene glycol monovinyl ether. These reactive diluents can be used individually or in combination of two or more. The amount of reactive diluent is not particularly limited, but from the viewpoint of balancing the adhesiveness and low viscosity of the insulating varnish composition, it is preferably in the range of 40 to 250 parts by mass relative to 100 parts by mass of the unsaturated polyester component, and more preferably in the range of 60 to 200 parts by mass. If the reactive diluent exceeds 250 parts by mass, the adhesiveness of the insulating varnish composition may sometimes be significantly reduced. On the other hand, if the reactive diluent is less than 40 parts by weight, the effect of reducing the viscosity of the insulating varnish composition produced by the addition of the reactive diluent may not be fully achieved.

[0030] A polymerization initiator can be added to the unsaturated polyester resin. The type of polymerization initiator is not particularly limited, as long as it is a compound that generates free radicals through heating or the like and promotes cross-linking reactions; it can be appropriately selected from known polymerization initiators. Specifically, an organic peroxide with a half-life temperature of less than or equal to 180°C is preferred as the polymerization initiator. Examples of organic peroxides as described above include methyl ethyl ketone peroxide, benzoyl peroxide, dicumyl peroxide, and t-butyl peroxide. These polymerization initiators can be used individually or in combination of two or more. If an organic peroxide with a half-life temperature higher than 180°C is used, the curing speed of the insulating varnish composition decreases, and the cured insulating varnish 14 containing bubbles 16 is not obtained, or the bubbles 16 may become enlarged. The amount of polymerization initiator is not particularly limited, but it is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, relative to 100 parts by mass of the unsaturated polyester component and the reactive diluent. If the amount of polymerization initiator is less than 0.1 parts by mass, the crosslinking density may decrease, resulting in reduced strength and chemical resistance of the cured insulating varnish 14. On the other hand, if the amount of polymerization initiator is more than 10 parts by mass, the usable time of the thermosetting resin 15 before curing may be significantly shortened.

[0031] Epoxy resin is obtained by mixing epoxy resin as the main agent and a curing agent. The type of epoxy resin is not particularly limited if it contains epoxy resin groups in its molecule; it can be appropriately selected from known epoxy resins. Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol type epoxy resin, phenol-formaldehyde type epoxy resin, cresol-phenol-formaldehyde type epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, and glycidylamine type epoxy resin. These epoxy resins can be used individually or in combination of two or more. Furthermore, to ensure that the weight average molecular weight of the resin components before curing is greater than or equal to 2000, a pre-polymerized epoxy resin can be used.

[0032] The type of curing agent is not particularly limited if it can cure the epoxy resin; it can be appropriately selected from known curing agents. Examples of curing agents include anhydride curing agents and amine curing agents. Examples of anhydride curing agents include bicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylic anhydride, and methylcyclohexene-1,2-dicarboxylic anhydride. Examples of amine curing agents include triethylenetetramine, 4,4'-diaminodiphenylmethane, and methylcyclohexylamine as primary and secondary amines, and N,N-benzyldimethylamine, dimethylaniline, and diazabicycloundecene as tertiary amines. These curing agents can be used individually or in combination of two or more. The amount of anhydride curing agent relative to 100 parts by weight of the epoxy resin compound is preferably 30 to 150 parts by weight, more preferably 50 to 100 parts by weight. Furthermore, the proportions of the first and second-level amine curing agents relative to 100 parts by weight of the epoxy resin compound are preferably 10 to 50 parts by weight, more preferably 20 to 40 parts by weight. Additionally, the proportion of the third-level amine curing agent relative to 100 parts by weight of the epoxy resin compound is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 3 parts by weight. If the proportions of the various curing agents are within the aforementioned ranges, an insulating varnish cured product 14 with high electrical and mechanical properties can be obtained.

[0033] Curing accelerators can be added to epoxy resins. Curing accelerators are compounds that accelerate the crosslinking reaction between the epoxy resin compound and the curing agent. The type of curing accelerator is not particularly limited if it is a material commonly used as a curing accelerator for epoxy resins; it can be appropriately selected from known curing accelerators. For example, imidazole curing accelerators and tertiary amine curing accelerators are preferred. These curing accelerators can be used individually or in combination of two or more.

[0034] Vinyl ester resins are obtained by mixing a main agent, primarily composed of a vinyl ester component with an average molecular weight greater than or equal to 2000 and unsaturated binding sites at both ends of the molecule, with a reactive diluent. The type of vinyl ester component is not particularly limited if it is obtained through an additional reaction between any epoxy resin and an unsaturated carboxylic acid; it can be appropriately selected from known vinyl ester resins.

[0035] The structure of an epoxy resin used as a raw material for vinyl ester resin is not particularly limited if it has at least two epoxy resin groups in its molecule. Examples of epoxy resins as described above include those having a structure based on bisphenol A, bisphenol F, cresol phenolic varnish, phenolic varnish, etc., as described in the preceding section on epoxy resins. These epoxy resins can be used individually or in combination of two or more. Furthermore, to ensure that the average molecular weight of the resin components before curing is greater than or equal to 2000, a pre-self-polymerized epoxy resin can be used.

[0036] The structure of an unsaturated carboxylic acid is not particularly limited if it simultaneously possesses one unsaturated binding site and a carboxyl group in its molecule. Examples of unsaturated carboxylic acids as described above include acrylic acid and methacrylic acid. These unsaturated carboxylic acids can be used individually or in combination of two or more. In particular, from the viewpoint that high reactivity can shorten the curing time of the insulating varnish composition based on high cured product properties and heat resistance life, it is preferable to use an unsaturated carboxylic acid obtained by additionally reacting acrylic acid with an epoxy resin compound.

[0037] The reactive diluent can contain the same components as the compounds described in the section on unsaturated polyester resins. Additionally, a polymerization initiator can be added to the vinyl ester resin. The polymerization initiator can contain the same components as the compounds described in the section on unsaturated polyester resins.

[0038] The bubble-forming component is a liquid with a vapor pressure greater than or equal to 1 mmHg and less than 80 mmHg under standard gas conditions. By selecting the liquid described above as the bubble-forming component, it sequentially vaporizes in conjunction with the curing reaction of the thermosetting resin 15, forming independent bubbles in the cured insulating varnish 14. Then, the entire amount of the bubble-forming component vaporizes, preventing liquid residue in the cured insulating varnish 14. If a liquid with a vapor pressure greater than or equal to 80 mmHg is used as the bubble-forming component, the vaporization of the bubble-forming component progresses before the curing of the thermosetting resin 15 begins, thus causing a reduction in the number of bubbles 16 and an increase in the diameter of the bubbles 16 in the cured insulating varnish 14. On the other hand, if a liquid with a vapor pressure less than 1 mmHg is used as the bubble-forming component, the bubble-forming component does not vaporize even near the highest temperature of the curing reaction of the thermosetting resin 15, therefore bubbles 16 cannot be formed in the cured insulating varnish 14. From the viewpoint of thermal stability of the insulating varnish composition and miniaturization of bubbles 16 in the cured insulating varnish 14, the bubble-forming component is more preferably a liquid with a vapor pressure greater than or equal to 5 mmHg and less than 40 mmHg under standard gas conditions.

[0039] The type of bubble-forming component is not particularly limited if it does not hinder the curing reaction of the thermosetting resin 15; it can be appropriately selected from known bubble-forming components. Examples of suitable bubble-forming components include hydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents, and amide solvents. Examples of hydrocarbon solvents include n-heptane, toluene, xylene, and cyclohexane. Examples of ketone solvents include methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, and cyclohexanone. Examples of ester solvents include butyl acetate and ethylene glycol monomethyl ether acetate. Examples of alcohol solvents include propanol, butanol, and diethylene glycol. Examples of amide solvents include N,N-dimethylformamide and N,N-dimethylacetamide. These bubble-forming components can be used individually or in combination of two or more. When two or more bubble-forming components are used in combination, vaporization of the bubble-forming components occurs over a wider temperature range, thus facilitating the formation of bubbles 16.

[0040] Starting from the point where the vaporization of the bubble-forming component and the curing of the thermosetting resin 15 occur simultaneously, it is preferable that the standard boiling point of the bubble-forming component is similar to the 1-minute half-life temperature of the polymerization initiator added to the thermosetting resin 15. The amount of the bubble-forming component added is preferably 10 to 50 parts by mass relative to the total mass of the thermosetting resin component and the reactive diluent of 100 parts by mass, more preferably 20 to 40 parts by mass. When the amount of the bubble-forming component is less than 10 parts by mass, the amount of vaporization is insufficient, and a sufficient number of bubbles 16 cannot be formed in the cured insulating varnish 14. On the other hand, when the amount of the bubble-forming component is more than 50 parts by mass, the strength and toughness of the cured insulating varnish 14 tend to decrease.

[0041] In the insulating varnish composition, known additives such as flame retardants, flame retardant auxiliaries, reinforcing agents, antioxidants, light stabilizers, anti-static agents, bubble nucleating agents, defoamers, surfactants, glass fibers, ceramic fibers, carbon fibers, stabilizers, and colorants can be formulated in proportions without impairing the effects of the present invention. The addition of these additives can improve the heat resistance, mechanical strength, and other properties of the insulating varnish composition. The aforementioned additives can be used individually or in combination of two or more.

[0042] Next, refer to Figure 2 and Figure 3 The manufacturing method of the coil 10 according to this embodiment will be described. The manufacturing method of the coil 10 may include a mixing process, a preheating process, an air cooling process, an impregnation process, a de-drip process, and a curing and drying process. In addition, these processes are just examples and do not limit the manufacturing method of the coil 10.

[0043] The mixing process involves mixing a thermosetting resin 15 comprising at least one of an unsaturated polyester resin, an epoxy resin, and a vinyl ester resin containing a high molecular weight fraction greater than or equal to 2000, a bubble-forming component having a vapor pressure of greater than or equal to 1 mmHg and less than 80 mmHg under standard gas conditions, and various additives. The mixing method is not particularly limited; any known mixing method may be appropriately selected. For example, the thermosetting resin 15, the bubble-forming component, and the various additives may be uniformly mixed using a mixer or similar machinery. Through this mixing process, an insulating varnish composition is obtained.

[0044] The preheating process involves heating the sample at a specified temperature. Figure 2 The process shown is to heat the coil 10 before impregnation. The air cooling process is to cool the coil 10, which has been heated in the preheating process, to a specified temperature in order to suppress the temperature rise of the insulating varnish composition in the impregnation process.

[0045] The impregnation process is the process of impregnating the coil 10, which has been cooled by the air-cooling process, with an insulating varnish composition. The impregnation method for the insulating varnish composition is not particularly limited, and any known method may be appropriately selected. Examples of impregnation methods for the insulating varnish composition include, for instance, the impregnation method (dipping method) in which the coil 10 is immersed in an impregnation tank containing the insulating varnish composition, and the dripping impregnation method (drip method) in which the insulating varnish composition is dripped onto the coil 10. When using the dripping impregnation method, the coil 10 can be preheated before the impregnation process begins. Furthermore, both the impregnation method and the dripping impregnation method allow the impregnation of the insulating varnish composition onto the coil 10 to be performed in multiple stages.

[0046] The drip removal process is a process that removes unwanted insulating varnish composition that has been attached to the sides of the coil 10 by the impregnation process.

[0047] The curing and drying process involves heating the insulating varnish composition impregnated with the coil 10 to cure it. Heating the insulating varnish composition cures the thermosetting resin 15, and the bubble-forming components vaporize to form a mixture containing… Figure 3The insulating varnish cured product 14, with fine air bubbles 16, is shown. The cured insulating varnish 14 is fixed to the coil 10 and fills the gap G between adjacent wires 11. Thus, a coil 10 with electrical insulation is obtained. The curing method of the insulating varnish composition is not particularly limited, and any known method can be appropriately selected. For example, a closed curing oven, a tunnel oven capable of continuous curing, or an electrically heated device can be used to heat and cure the insulating varnish composition. The heating temperature of the insulating varnish composition is not particularly limited, generally 80°C to 200°C, preferably 130°C to 180°C. If the heating temperature of the insulating varnish composition is less than 80°C, the curing of the insulating varnish composition may become insufficient. Furthermore, if the heating temperature of the insulating varnish composition is higher than 200°C, the possibility of deterioration and decomposition of the resin components that electrically insulate the coil 10, such as the insulating varnish, phase paper, and insulator 9, increases.

[0048] The curing speed of the insulating varnish composition and the amount of the insulating varnish composition adhering to the coil 10 vary depending on the composition of the insulating varnish composition. Therefore, the heating time of the insulating varnish composition can be appropriately set according to its composition, requiring a heating time for complete curing of the insulating varnish composition. Generally, this is 5 minutes to 6 hours, preferably 20 minutes to 4 hours, and more preferably 30 minutes to 2 hours. By using the curing conditions described above, a coil 10 with sufficient electrical insulation can be obtained. In particular, by impregnating the coil 10 with the insulating varnish composition and heating it at 130°C to 180°C for 5 minutes to 2 hours to cure it, the gaps G between the wires 11 of the coil 10 can be filled by the cured insulating varnish 14 containing microbubbles 16. This can suppress the occurrence of partial discharge between adjacent wires 11, improve the heat resistance of the coil 10, and enhance the reinforcing properties of the coil 10.

[0049] From the viewpoint of suppressing the occurrence of partial discharge in the cured insulating varnish 14, it is preferable that all the bubbles 16 contained in the cured insulating varnish 14 are independent bubbles. Furthermore, the size of the bubbles 16 is preferably such that the largest bubble diameter is less than or equal to 10 μm, and more preferably less than or equal to 5 μm. If the largest bubble diameter of the bubbles 16 is within the aforementioned range, the electrical properties, particularly the effect of suppressing the occurrence of partial discharge in the bubbles 16, are improved. The minimum diameter of the bubbles 16 is not particularly limited, but is preferably greater than or equal to 0.1 μm. The size of the bubbles 16 can be determined by observing the cross-section of the cured insulating varnish 14 using a scanning electron microscope (SEM). Specifically, the cured insulating varnish 14 is cut, and its cross-section is magnified by SEM, for example, to 15,000x. The diameter of each of the arbitrarily selected bubbles 16 is measured, and the arithmetic mean of the measured bubble diameters is calculated to determine the size of the bubbles 16, i.e., the average diameter of the bubbles 16. Besides being circular, the cross-sectional shape of bubble 16 can also be elliptical or rectangular. In the case of a circular bubble 16, the diameter of the circle is set as the bubble diameter. In the case of an elliptical bubble 16, the major axis of the ellipse is set as the diameter. In the case of a rectangular bubble 16, the length of the line connecting the diagonals of the rectangle is set as the bubble diameter.

[0050] Next, the effects of the insulating varnish composition, the cured insulating varnish 14, and the coil 10 involved in this embodiment will be explained.

[0051] Generally speaking, in Figure 3 If a strong electric field is applied between adjacent wires 11 by energizing the coil 10, partial discharge may occur due to electron avalanche in the air. In this embodiment, the insulating varnish composition, which is an element of the insulating varnish cured product 14, includes: a thermosetting resin 15 containing at least one resin among unsaturated polyester resin, epoxy resin, and vinyl ester resin containing a high molecular weight body with a weight average molecular weight greater than or equal to 2000; and a liquid bubble-forming component whose vapor pressure under standard gas conditions is greater than or equal to 1 mmHg and less than 80 mmHg. As a result, a large number of fine bubbles 16 are formed in the insulating varnish cured product 14. Therefore, the relative permittivity of the insulating varnish cured product 14 can be reduced, thereby increasing the partial discharge initiation voltage of the insulating varnish cured product 14 and suppressing the occurrence of partial discharge between adjacent wires 11. In addition, the bubbles 16 contained in the insulating varnish cured product 14 can be miniaturized, thus suppressing the occurrence of partial discharge of the bubbles 16 in the insulating varnish cured product 14.

[0052] In this embodiment, the bubble-forming component is liquid, thus improving the impregnation properties of the insulating varnish composition onto the coil 10.

[0053] In this embodiment, the thermosetting resin 15 contains a polymerization initiator with a 1-minute half-life temperature of less than or equal to 180°C, thereby enabling the production of an insulating varnish cured product 14 containing bubbles 16 at a temperature of less than or equal to 200°C, which is suitable for the curing conditions of the insulating varnish composition.

[0054] In this embodiment, the bubble-forming component is a liquid containing at least one of hydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents, phenol solvents, and amide solvents, thereby facilitating the formation of bubbles 16 during the curing of the insulating varnish composition and enabling the miniaturization of bubbles 16.

[0055] In this embodiment, the average diameter of the bubbles 16 contained in the cured insulating varnish 14 is in the range of 0.1 μm to 10 μm, thereby achieving both the effect of suppressing the occurrence of partial discharge in the bubbles 16 and the effect of reducing the relative permittivity of the cured insulating varnish 14. Therefore, it is also possible to cope with the increase in the current flowing through the coil 10 that accompanies the increase in the output of the coil 10.

[0056] Furthermore, in this embodiment, the insulating varnish composition of the present invention is used for the insulation of the coil 10 of the rotating machine 1, but the insulating varnish composition of the present invention can also be used for the insulation of the coils of various rotating machines such as generators, transformers, and compressors.

[0057] Next, the effects of the present invention will be further explained through examples and comparative examples.

[0058] Table 1

[0059]

[0060] (Material composition)

[0061] The insulating varnish compositions described in Examples 1-8 and Comparative Examples 1-5 were prepared according to the proportions shown in Table 1. Furthermore, the details of each material shown in Table 1 are described below.

[0062] (Unsaturated polyester resin)

[0063] Unsaturated polyester resin A: An unsaturated polyester resin prepared by condensing and polymerizing 30 parts by weight of maleic acid, 20 parts by weight of isophthalic acid, and 50 parts by weight of propylene glycol using a known method, to achieve a polymer average molecular weight of approximately 5000.

[0064] Unsaturated polyester resin B: An unsaturated polyester resin prepared by condensing and polymerizing 30 parts by weight of maleic acid, 20 parts by weight of isophthalic acid, and 50 parts by weight of propylene glycol using a known method, to achieve a polymer average molecular weight of approximately 8000.

[0065] Unsaturated polyester resin C: An unsaturated polyester resin prepared by condensing and polymerizing 30 parts by weight of maleic acid, 20 parts by weight of isophthalic acid, and 50 parts by weight of propylene glycol using a known method, to achieve a polymer average molecular weight of approximately 2000.

[0066] Unsaturated polyester resin D: An unsaturated polyester resin prepared by condensing and polymerizing 30 parts by weight of maleic acid, 20 parts by weight of isophthalic acid, and 50 parts by weight of propylene glycol using a known method, so that the average molecular weight of the polymer is about 1000.

[0067] Reactive diluent: styrene

[0068] Polymerization initiator: Benzoyl peroxide

[0069] (Epoxy resin)

[0070] Epoxy resin compound: A linear epoxy resin prepared by alternating copolymerization of bisphenol A diglycidyl ether (manufactured by Mitsubishi Chemical Corporation: jER828) and bisphenol A using a known method, with a polymerization average molecular weight of approximately 5000.

[0071] Curing agent: Bicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride

[0072] Curing accelerator: 2-ethyl-4-methylimidazolium

[0073] (Vinyl ester resin)

[0074] Vinyl ester composition: A bisphenol A type vinyl ester resin is prepared by alternating copolymerization of bisphenol A diglycidyl ether (manufactured by Mitsubishi Chemical Corporation: jER828) and bisphenol A using a known method, followed by end-cap modification with methacrylic acid, to achieve a polymer average molecular weight of approximately 5000.

[0075] Reactive diluent: styrene

[0076] Polymerization initiator: Benzoyl peroxide

[0077] (Bubble-forming components)

[0078] Use directly without refining the following commercially available products.

[0079] 2-Propanol: Vapor pressure under standard conditions: 40 mmHg; Alcohols: Methyl isobutyl ketone: Vapor pressure under standard conditions: 15 mmHg; Ketones: Xylene: Vapor pressure under standard conditions: 10 mmHg; Hydrocarbons

[0080] Cyclohexanone: Vapor pressure under standard conditions is 4 mmHg; ketones.

[0081] Tetrahydrofuran: Vapor pressure under standard conditions is 175 mmHg; ether.

[0082] Ethyl acetate: vapor pressure under standard conditions is 92 mmHg; ester.

[0083] 2-Aminoethanol: Vapor pressure under standard conditions is 0.4 mmHg; alcohol.

[0084] Ethylene glycol: vapor pressure under standard conditions is 0.01 mmHg; alcohol.

[0085] (Example 1)

[0086] 100 parts by weight of unsaturated polyester resin A, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of 2-propanol were uniformly mixed to obtain the insulating varnish composition involved in Example 1.

[0087] (Example 2)

[0088] 100 parts by weight of unsaturated polyester resin A, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of methyl isobutyl ketone were uniformly mixed to obtain the insulating varnish composition involved in Example 2.

[0089] (Example 3)

[0090] 100 parts by weight of unsaturated polyester resin A, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of xylene were uniformly mixed to obtain the insulating varnish composition involved in Example 3.

[0091] (Example 4)

[0092] 100 parts by weight of unsaturated polyester resin A, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of cyclohexanone were uniformly mixed to obtain the insulating varnish composition involved in Example 4.

[0093] (Example 5)

[0094] 100 parts by weight of unsaturated polyester resin B, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of xylene were uniformly mixed to obtain the insulating varnish composition involved in Example 5.

[0095] (Example 6)

[0096] 100 parts by weight of unsaturated polyester resin C1, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of xylene were uniformly mixed to obtain the insulating varnish composition involved in Example 6.

[0097] (Example 7)

[0098] 100 parts by weight of epoxy resin compound, 80 parts by weight of curing agent, 2 parts by weight of curing accelerator and 50 parts by weight of xylene were uniformly mixed to obtain the insulating varnish composition involved in Example 7.

[0099] (Example 8)

[0100] 100 parts by weight of vinyl ester, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of xylene were uniformly mixed to obtain the insulating varnish composition of Example 8.

[0101] (Comparative Example 1)

[0102] 100 parts by weight of unsaturated polyester resin A, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of tetrahydrofuran were uniformly mixed to obtain the insulating varnish composition involved in Comparative Example 1.

[0103] (Comparative Example 2)

[0104] 100 parts by weight of unsaturated polyester resin A, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of ethyl acetate were uniformly mixed to obtain the insulating varnish composition involved in Comparative Example 2.

[0105] (Comparative Example 3)

[0106] 100 parts by weight of unsaturated polyester resin A, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of 2-aminoethanol were uniformly mixed to obtain the insulating varnish composition involved in Comparative Example 3.

[0107] (Comparative Example 4)

[0108] 100 parts by weight of unsaturated polyester resin A, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of ethylene glycol were uniformly mixed to obtain the insulating varnish composition involved in Comparative Example 4.

[0109] (Comparative Example 5)

[0110] 100 parts by weight of unsaturated polyester resin D, 80 parts by weight of reactive diluent, 2 parts by weight of polymerization initiator and 50 parts by weight of xylene were uniformly mixed to obtain the insulating varnish composition involved in Comparative Example 5.

[0111] (Experimental Methods)

[0112] Regarding the cured insulating varnishes obtained by curing the insulating varnish compositions involved in Examples 1-8 and Comparative Examples 1-5, the presence or absence of microbubbles in the cured insulating varnishes and the relative permittivity of the cured insulating varnishes were evaluated. The insulating varnish compositions involved in all examples and comparative examples were injected into a mold frame and cured by heat curing in a drying oven to obtain cured insulating varnishes with dimensions of 20 mm (length) × 20 mm (width) × 1 mm (thickness). In all examples and comparative examples, the heat curing conditions were set to 180°C for 30 minutes.

[0113] [Presence or absence of microbubbles in the cured insulating varnish]

[0114] The presence or absence of microbubbles in the cured insulating varnish was evaluated by observing the cross-section of the cured insulating varnish using SEM. Specifically, 10 bubbles were randomly selected, and the diameter of each bubble was measured. A bubble diameter whose arithmetic mean was less than or equal to 10 μm was evaluated as good, and a bubble diameter greater than 10 μm was evaluated as bad.

[0115] [Relative permittivity]

[0116] The relative permittivity of the cured insulating varnish is calculated by sandwiching the cured varnish between two flat electrodes and measuring the capacitance. A relative permittivity less than or equal to 3.0 obtained at 25°C and 1kHz is rated as good, while a relative permittivity greater than 3.0 is rated as bad.

[0117] As clearly shown in Table 1, Examples 1-8, in which the thermosetting resin contains a weight-average molecular weight greater than or equal to 2000 and the vapor pressure of the gas containing the bubble-forming component under standard conditions is in the range of 4 mmHg to 40 mmHg, show a "good" evaluation in terms of the presence or absence of microbubbles and the relative permittivity in the cured insulating varnish. On the other hand, Comparative Examples 1-4 have bubble-forming component gases whose vapor pressure under standard conditions is outside the range of 1 mmHg to 80 mmHg, therefore microbubbles cannot be formed in the cured insulating varnish, and the effect of sufficiently reducing the relative permittivity of the cured insulating varnish cannot be obtained. Furthermore, in Comparative Example 5, the thermosetting resin contains a weight-average molecular weight of 1000, thus confirming an increase in the bubble diameter in the cured insulating varnish.

[0118] The structure shown in the above embodiments is an example and can be combined with other known technologies. Without departing from the main idea, parts of the structure can be omitted or modified.

[0119] Explanation of the label

[0120] 1 Rotating machine, 2 Stator, 3 Rotor, 4 Shaft, 5 Frame, 6 Bracket, 6a Hole, 7 Stator core, 7a Core seat, 7b Tooth, 8 Slot, 9 Insulator, 10 Coil, 11 Wire, 12 Conductor, 13 Insulating film, 14 Cured insulating varnish, 15 Thermosetting resin, 16 Bubble, C Central shaft, G Gap.

Claims

1. An insulating varnish composition, characterized in that, have: A thermosetting resin comprising at least one resin selected from unsaturated polyester resin, epoxy resin, and vinyl ester resin containing a high molecular weight component with a weight average molecular weight greater than or equal to 2000; and The components that form bubbles in a liquid have a vapor pressure under standard conditions greater than or equal to 5 mmHg and less than 40 mmHg. The standard state of the gas is defined by setting the reference temperature to 25°C and the standard pressure to 100 kPa. The thermosetting resin contains a polymerization initiator with a half-life temperature of less than or equal to 180°C within 1 minute. The bubble-forming component is a liquid containing at least one of the following: ketone solvents, ester solvents, alcohol solvents, phenol solvents, and amide solvents.

2. A cured insulating varnish, which is a cured insulating varnish formed by curing the insulating varnish composition described in claim 1, characterized in that, The average diameter of the air bubbles contained in the cured insulating varnish is in the range of 0.1 μm to 10 μm.

3. A coil, characterized in that, have: The wire wound around the stator core; and The cured insulating varnish as described in claim 2 fills the gap between adjacent wires.

4. A method for manufacturing a coil, which is the method for manufacturing a coil as described in claim 3, characterized in that, Include: The impregnation process involves impregnating the coil with the insulating varnish composition as described in claim 1; and The heat curing process involves heating the insulating varnish composition impregnated in the coil to cure it.

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