Stator coil and rotating electric machine

Abstract

A thermosetting resin composition (3) according to the present application comprises a thermosetting resin (1), a curing agent that cures the thermosetting resin (1), and an organic insulating-gas-generating agent (2) that generates an insulating gas by pyrolysis. Insulating gas other than oxygen gas is generated by the organic insulating-gas-generating agent (2) at a temperature higher than the curing temperature of the thermosetting resin (1) but 300°C or lower. Long-term suppression of partial discharge in the insulating layer is realized and electric insulation of the iron core and coil conductor is guaranteed.

Description

Thermosetting resin composition, stator coil and rotating electric machine

[0001] The present application relates to a thermosetting resin composition, a stator coil, and a rotating electric machine.

[0002] In order to reduce the size and increase the output of high-voltage rotating electrical machines such as industrial induction motors, water turbine generators, and turbine generators, efforts are being made to increase the voltage and power density of rotating electrical machines. Accordingly, the structure of coils for high-voltage equipment is becoming more compact, and the main insulating layer, which is made up of insulating tape and insulating varnish, is required to have the properties to withstand high voltages for a long period of time.

[0003] A conventional stator coil for a high-voltage rotating electric machine consists of a coil conductor and a main insulating layer made of mica tape, anti-corona tape (anti-corona layer), and insulating varnish. The mica tape and anti-corona tape are wound around the coil conductor in that order, and the stator coil is assembled into the stator core. A thermosetting resin composition is then vacuum-pressurized and impregnated as an insulating varnish, and the varnish is then heated and cured to form the main insulating layer.

[0004] However, if voids such as bubbles or peeling form in the main insulation layer during the manufacturing process, these voids become the starting point for partial discharges because they are exposed to high electric fields due to the increased voltage and power density. Partial discharges generated in these voids cause electrical trees, an electrical breakdown phenomenon, to branch and grow in the main insulation layer between the coil conductors and between the coil conductors and the iron core. Eventually, these trees penetrate the main insulation layer, causing a breakdown.

[0005] Therefore, as a method for suppressing partial discharge in the gap, there has been disclosed a main insulating layer that contains an inorganic insulating gas generating agent and is composed of a mica tape containing a resin composition and an insulating varnish, a stator coil that is composed using the main insulating layer, and a rotating electric machine that is equipped with the stator coil (see, for example, Patent Document 1).

[0006] When a partial discharge occurs in the voids of the insulation system material, the inorganic insulating gas generating agent is decomposed by the partial discharge energy, generating an insulating gas containing carbon dioxide, oxygen, and nitrogen. The insulating gas has the function of capturing negative ions generated by the partial discharge, and carbon dioxide also generates oxygen molecules with higher electron attachment properties through secondary decomposition, which promotes the capture of the negative ions and suppresses partial discharge. Furthermore, the insulating gas generated by the insulating gas generating agent increases the pressure in and around the voids of the main insulation layer, thereby also achieving the effect of improving the partial discharge inception voltage.

[0007] JP 2016-201930 A (paragraph 0031, Figure 3)

[0008] However, in the resin compositions used in the conventional high-voltage equipment described above, oxygen is generated from the inorganic insulating gas generating agent. When partial discharge occurs in the voids, this oxygen is used as a raw material to generate ozone and atomic oxygen, which causes the problem of accelerating oxidative degradation of the insulating layer. In addition, the foaming initiation temperature of inorganic insulating gas generating agents is high, around 300°C to 1000°C, which causes the problem of thermal degradation of the main insulating layer before the foaming initiation temperature is reached.

[0009] The present application discloses a technique for solving the above-mentioned problems, and aims to provide a thermosetting resin composition, a stator coil, and a rotating electric machine that can suppress partial discharge in the main insulating layer over a long period of time and ensure electrical insulation between the iron core and the coil conductor.

[0010] The thermosetting resin composition disclosed in the present application is a thermosetting resin composition containing a thermosetting resin, a curing agent that cures the thermosetting resin, and an organic insulating gas generating agent that generates an insulating gas by thermal decomposition, wherein the organic insulating gas generating agent generates the insulating gas other than oxygen gas at a temperature that is higher than the curing temperature of the thermosetting resin and is equal to or lower than 300°C.

[0011] The stator coil disclosed in the present application is characterized in that the outer layer of the coil conductor is made of a main insulating layer using the above-mentioned thermosetting resin composition.

[0012] A rotating electric machine disclosed in the present application is characterized by including the above-described stator coil.

[0013] According to the present invention, it is possible to suppress partial discharge in the insulating layer over a long period of time and ensure electrical insulation between the iron core and the coil conductor.

[0014] Fig. 1 is a cross-sectional view schematically showing the structure of a main insulating layer using a thermosetting resin composition according to embodiment 1. Fig. 2 is a cross-sectional view schematically showing the structure of a main insulating layer using a thermosetting resin composition according to embodiment 2. Fig. 3 is a cross-sectional view schematically showing the structure of a stator coil including a main insulating layer using a thermosetting resin composition according to embodiment 3. Fig. 4 is a cross-sectional view schematically showing the structure of a rotating electric machine configured with a stator coil including a main insulating layer using a thermosetting resin composition according to embodiment 4.

[0015] Embodiment 1. Figure 1 is a cross-sectional schematic diagram showing the structure of a main insulating layer using a thermosetting resin composition according to Embodiment 1 of the present invention. As shown in Figure 1, the main insulating layer 7 of this embodiment 1 is composed of a mica tape 6 and a thermosetting resin composition 3 as an insulating varnish. The thermosetting resin composition 3 contains a thermosetting resin 1 and an organic insulating gas generating agent 2, and the organic insulating gas generating agent 2 is dispersed in the matrix of the thermosetting resin 1. The thermosetting resin composition 3 may be blended as needed as a constituent material of the mica tape 6. The thermosetting resin composition 3 used in the main insulating layer 7 will be described below.

[0016] <Thermosetting Resin> As the thermosetting resin 1, from the viewpoint of improving heat resistance, adhesiveness, electrical insulation, and mechanical strength, epoxy resin, phenol resin, unsaturated polyester resin, imide resin, silicone resin, etc. are preferred, and among these, epoxy resin is more preferred. Examples of epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, biphenol epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, bisphenol F novolac epoxy resins, alicyclic epoxy resins, aliphatic linear epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, hydantoin epoxy resins, isocyanurate epoxy resins, salicylic aldehyde novolac epoxy resins, diglycidyl ethers of bifunctional phenols, halides of bifunctional phenols, hydrogenated products of bifunctional phenols, diglycidyl ethers of bifunctional alcohols, halides of bifunctional alcohols, and hydrogenated products of bifunctional alcohols. These epoxy resins may be used alone or in combination of two or more. On the other hand, from the viewpoint of improving the balance between material cost, viscosity, and heat resistance, it is preferable to use a reaction product of epichlorohydrin and a bisphenol A compound as the thermosetting resin 1 .

[0017] <Curing Agent> A curing agent is added to the thermosetting resin composition 3 to cure the thermosetting resin 1. Any curing agent can be used as long as it chemically reacts with the thermosetting resin 1 to cure it, and the type is not limited. Examples of such curing agents that can be used include amine-based curing agents, acid anhydride-based curing agents, imidazole-based curing agents, polymercaptan-based curing agents, phenol-based curing agents, Lewis acid-based curing agents, and isocyanate-based curing agents. Note that a catalyst that cures the thermosetting resin 1 may be added as an alternative to the curing agent.

[0018] Specific examples of the amine-based curing agent include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, dipropylenediamine, polyetherdiamine, 2,5-dimethylhexamethylenediamine, trimethylhexamethylenediamine, diethylenetriamine, iminobispropylamine, bis(hexamethyl)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, aminoethylethanolamine, tri(methylamino)hexane, dimethylaminopropylamine, diethylamino Examples of suitable organic solvents include propylamine, methyliminobispropylamine, menthenediamine, isophoronediamine, bis(4-amino-3-methyldicyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, N-aminoethylpiperazine, 3,9-bis(3-aminopropyl)2,4,8,10-tetraoxaspiro(5,5)undecane, m-xylenediamine, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, diaminodiethyldiphenylmethane, dicyandiamide, and organic acid dihydrazides.

[0019] Specific examples of acid anhydride curing agents include dodecenyl succinic anhydride, polyadipic anhydride, polyazelaic anhydride, polysebacic anhydride, poly(ethyloctadecanedioic) anhydride, poly(phenylhexadecanedioic) anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylhimic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, methylcyclohexene dicarboxylic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid, ethylene glycol bistrimellitate, glycerol tristrimellitate, HET anhydride, tetrabromophthalic anhydride, Nadic anhydride, methylnadic anhydride, and polyazelaic anhydride. These acid anhydrides may be used alone or in combination of two or more. The amount of acid anhydride is not particularly limited and may be adjusted appropriately depending on the type of acid anhydride used, the type of thermosetting resin 1, and other factors. For example, when a bisphenol-type epoxy resin is used as the thermosetting resin 1, the amount of acid anhydride is preferably 10 to 150 parts by mass, more preferably 30 to 120 parts by mass, and even more preferably 50 to 100 parts by mass, per 100 parts by mass of the bisphenol-type epoxy resin. Such an amount of acid anhydride allows the thermosetting resin composition 3 to be properly cured. When a bisphenol-type epoxy resin and a bisphenol-type curing agent are used, the equivalent ratio of the acid anhydride groups of the acid anhydride to the epoxy groups of the epoxy resin is not particularly limited, but is preferably 0.7 to 1.3, more preferably 0.8 to 1.2, and even more preferably 0.9 to 1.1. If the equivalent ratio is less than 0.7, the workability of forming the main insulating layer 7 tends to decrease. On the other hand, if the equivalent ratio exceeds 1.3, the heat resistance of the main insulating layer 7 tends to decrease.

[0020] Specific examples of imidazole-based curing agents include imidazole-based compounds such as 2-methylimidazole, 2-undecylimidazole, 1,2-dimethylimidazole, 2-methylimidazole, 2-butadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole. Specific examples of polymercaptan-based curing agents include polysulfide and thioester.

[0021] Furthermore, a curing accelerator may be added in combination with the curing agent to accelerate or control the curing reaction of the thermosetting resin 1. In particular, when an acid anhydride-based curing agent is added, the curing reaction is slower than with other curing agents such as amine-based curing agents, so a curing accelerator is often used. Preferred curing accelerators for acid anhydride-based curing agents include tertiary amines or their salts, quaternary ammonium compounds, imidazoles, and alkali metal alkoxides.

[0022] A reactive diluent may be added to the curing agent. Examples of reactive diluents include styrene monomers, monomers with hydrocarbon functional groups attached to the phenyl groups of styrene monomers, methacrylic monomers, and acrylic monomers. The methacrylic monomers are not particularly limited as long as they do not impair the curing of the epoxy resin, and examples include linear methacrylates, branched methacrylates, and cyclic methacrylates. From the viewpoint of heat resistance, linear methacrylates are preferably used as the methacrylic monomers. Examples of linear methacrylates include lauryl methacrylate, isobornyl methacrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, and cyclohexyl methacrylate. These linear methacrylates may be used alone or in combination of two or more. The acrylic monomers are not particularly limited as long as they do not impair the curing of the epoxy resin, and examples include linear acrylates, branched acrylates, and cyclic acrylates. From the viewpoint of heat resistance, linear acrylates are preferably used as the acrylic monomers. Examples of linear acrylates include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trimethylolpropane triacrylate, lauryl acrylate, isobornyl acrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, and 2-(2,4,6-tribromophenoxy)ethyl acrylate. These linear acrylates may be used alone or in combination of two or more. The amount of reactive diluent added is not particularly limited and may be adjusted as appropriate.

[0023] <Organic insulating gas generating agent> As the organic insulating gas generating agent 2, any organic insulating gas generating agent 2 that decomposes due to a temperature rise caused by discharge energy to generate an insulating gas such as nitrogen gas, carbon dioxide gas, carbon monoxide, or ammonia gas can be used appropriately, and the type is not particularly limited. Examples of the organic insulating gas generating agent 2 having such properties include azo-based blowing agents such as azodicarbonamide (ADCA) and azobisisobutyronitrile, and azo-based blowing agents such as dinitrosopentamethylenetetramine (DPT) and N,N'-dinitroso- Nitroso-based blowing agents such as N,N'-dimethylterephthalamide, hydrazide-based blowing agents such as p-toluenesulfonylhydrazide, p,p'-oxybis(benzenesulfonylhydrazide, OBSH) and benzenesulfonylhydrazide, hydrazodicarbonamide (HDCA), trihydrazinotriazine, and the like can be used. The organic insulating gas generating agents 2 described above can be used alone or as a mixture of two or more types.

[0024] The lower limit of the decomposition temperature of the organic insulating gas generating agent 2 is preferably the curing temperature of the thermosetting resin 1. On the other hand, the upper limit of the decomposition temperature of the organic insulating gas generating agent 2 is preferably 300°C, more preferably 250°C. If the decomposition temperature of the organic insulating gas generating agent 2 is lower than the above-mentioned lower limit, the organic insulating gas generating agent 2 will foam when the thermosetting resin composition 3 is heat-cured, and air bubbles will be mixed into the cured product of the thermosetting resin composition 3. On the other hand, the above-mentioned organic insulating gas generating agent 2 will decompose in a temperature range of 300°C or less, and there is no organic insulating gas generating agent 2 that decomposes above the upper limit of 300°C. Here, the decomposition temperature is expressed as the temperature at which 10 parts by mass is lost per 100 parts by mass at room temperature.

[0025] The lower limit of the content of the organic insulating gas generating agent 2 relative to 100 parts by mass of the thermosetting resin 1 is preferably 0.25 parts by mass, more preferably 1 part by mass. When the content of the organic insulating gas generating agent 2 relative to 100 parts by mass of the thermosetting resin 1 is less than 0.25 parts by mass, the amount of insulating gas generated is small, and partial discharge resistance characteristics cannot be fully exhibited. On the other hand, the upper limit of the content of the organic insulating gas generating agent 2 relative to 100 parts by mass of the thermosetting resin 1 is preferably 50 parts by mass, more preferably 40 parts by mass. When the content of the organic insulating gas generating agent 2 relative to 100 parts by mass of the thermosetting resin 1 exceeds 50 parts by mass, the matrix becomes relatively small, resulting in insufficient strength and fusion properties of the thermosetting resin 1. Furthermore, because the interparticle distance between the organic insulating gas generating agents 2 is small, decomposition of the organic insulating gas generating agent 2 occurs continuously when partial discharge starts, and partial discharge resistance characteristics cannot be fully exhibited.

[0026] The lower limit of the average diameter of the organic insulating gas generating agent 2 is preferably 1 μm, more preferably 5 μm. On the other hand, the upper limit of the average diameter of the organic insulating gas generating agent 2 is preferably 50 μm, more preferably 40 μm. If the average diameter of the organic insulating gas generating agent 2 is less than 1 μm, the probability of contact between the electrical tree and the organic insulating gas generating agent 2 decreases, and the partial discharge suppression effect cannot be fully exhibited. Conversely, if the average diameter of the organic insulating gas generating agent 2 exceeds 50 μm, the diameter of bubbles formed by decomposition of the organic insulating gas generating agent 2 becomes large, and the partial discharge resistance characteristics deteriorate. Here, the average particle diameter is represented by the median diameter D50 of the volume particle size distribution in the dispersion liquid.

[0027] Furthermore, according to the first embodiment of the present invention, the thermal decomposition residue of the organic insulating gas generating agent 3 has low reactivity with water, and thermal deterioration of the main insulating layer due to heat generated by the chemical reaction can be suppressed.

[0028] A foaming aid may be blended into the thermosetting resin composition 3 together with the organic insulating gas generating agent 2. The foaming aid is not particularly limited as long as it accelerates the thermal decomposition of the organic insulating gas generating agent 2, and examples thereof include urea compounds.

[0029] The lower limit of the amount of foaming aid to be blended relative to 100 parts by mass of the organic insulating gas generating agent 2 is preferably 5 parts by mass, more preferably 50 parts by mass. On the other hand, the upper limit of the amount of foaming aid to be blended is preferably 200 parts by mass, more preferably 150 parts by mass. If the amount of foaming aid to be blended is less than 5 parts by mass, the effect of decomposing the chemical foaming agent may be insufficient. Conversely, if the amount of foaming aid to be blended exceeds 200 parts by mass, there is a risk that the organic insulating gas generating agent 2 may unintentionally decompose during heat curing of the thermosetting resin composition 3, during storage of the cured product, etc.

[0030] In addition to the above-described components, additives may be blended as necessary into the constituent materials of the thermosetting resin composition 3 according to this embodiment, to the extent that the effects of the present application are not impaired. Examples of other additives that may be blended into the materials of the thermosetting resin composition 3 include reactive diluents, viscosity modifiers such as toluene and xylene, curing accelerators, anti-sagging agents, anti-settling agents, anti-foaming agents, leveling agents, slip agents, dispersants, and substrate wetting agents.

[0031] As described above, in the first embodiment of the present application, the thermosetting resin composition 3 contains the thermosetting resin 1 and the organic insulating gas generating agent 2. When the thermosetting resin composition 3 containing the organic insulating gas generating agent 2 is used for the main insulating layer 7, insulating gases that do not contain oxygen gas, such as nitrogen and carbon dioxide, are generated by thermal decomposition, and the internal pressure in the voids and their vicinity is increased, thereby suppressing the occurrence of partial discharge. Furthermore, compared to when the thermosetting resin composition 3 containing an inorganic insulating gas generating agent is used for the main insulating layer 7, the partial discharge inception voltage of the main insulating layer 7 is improved, and the discharge suppression effect can be fully exerted even when the temperature rise due to discharge energy is small. This makes it possible to suppress partial discharges that occur inside the bubbles during operation of the rotating electric machine, thereby extending the life of the main insulating layer.

[0032] As described above, the thermosetting resin composition 3 according to the first embodiment is a thermosetting resin composition 3 comprising a thermosetting resin 1, a curing agent for curing the thermosetting resin 1, and an organic insulating gas generating agent 2 that generates an insulating gas by thermal decomposition. The organic insulating gas generating agent 2 generates an insulating gas other than oxygen gas at a temperature higher than the curing temperature of the thermosetting resin 1 but not higher than 300°C. Since the insulating gas does not contain oxygen, oxidation degradation of the main insulating layer due to ozone and atomic oxygen can be suppressed. Furthermore, since the insulating gas is generated at a low temperature range higher than the curing temperature but not higher than 300°C, the time of exposure to partial discharge energy can be shortened and thermal degradation of the main insulating layer can be suppressed. Furthermore, by generating insulating gases such as nitrogen and carbon dioxide that do not contain oxygen gas by thermal decomposition and increasing the internal pressure in and around the voids, the occurrence of partial discharge can be suppressed. Furthermore, compared to when the thermosetting resin composition 3 containing an inorganic insulating gas generating agent is used for the main insulating layer 7, the partial discharge inception voltage of the main insulating layer 7 is improved, and the discharge suppression effect can be fully exerted even when the temperature rise due to the discharge energy is small.

[0033] Second Embodiment In a second embodiment, a case where a thermosetting resin composition further containing an inorganic nanofiller is used will be described.

[0034] 2 is a cross-sectional schematic diagram showing the structure of a main insulating layer using a thermosetting resin composition according to embodiment 2 of the present invention. As shown in FIG. 2, the main insulating layer 7 of embodiment 2 is composed of a mica tape 6 and a thermosetting resin composition 30 as an insulating varnish. The thermosetting resin composition 30 is the same as the thermosetting resin composition 3 of embodiment 1, but further contains inorganic nanofiller 8 dispersed in the matrix of the thermosetting resin 1.

[0035] <Inorganic nano-filler> The inorganic nano-filler 8 is difficult to scrape off even when a partial discharge occurs in the main insulating layer 7, and therefore serves as a physical barrier to the electrical tree propagating in the main insulating layer 7, causing the electrical tree to branch in a dendritic form. Therefore, it is possible to slow down the propagation speed of the electrical tree and increase the probability of contact with the organic insulating gas generating agent 2, thereby improving the partial discharge resistance characteristics.

[0036] Metal oxides such as titanium oxide, silica, aluminum oxide, zirconium oxide, aluminum hydroxide, magnesium hydroxide, potassium titanate, magnesium oxide, and calcium oxide are preferred as the inorganic nanofiller 8, and titanium oxide, silica, and magnesium hydroxide are particularly preferred. These inorganic nanofillers 8 may be used alone or in combination of two or more.

[0037] The shape of the inorganic nanofiller 8 is not particularly limited, and is preferably granular, spherical, or scale-like. Among these, a spherical shape is more preferable from the viewpoint of dielectric breakdown resistance and strength. Here, a spherical shape means a sphere in which the ratio of the minimum diameter to the maximum diameter in a cross section passing through the center of gravity is 90% or more.

[0038] The lower limit of the average particle diameter of the inorganic nanofiller 8 is preferably 0.5 nm, more preferably 1 nm. The upper limit of the average particle diameter of the inorganic nanofiller 8 is preferably 1 μm, more preferably 0.5 μm. When the average particle diameter of the inorganic nanofiller 8 is less than 0.5 nm, the particle diameter is smaller than the electrical tree diameter, so it does not function as a physical barrier and the effect of inhibiting electrical tree propagation cannot be fully exhibited. On the other hand, when the average particle diameter of the inorganic nanofiller 8 exceeds 1 μm, the probability of contact with the electrical tree is low, and the effect of inhibiting tree propagation cannot be fully exhibited. Here, the average particle diameter is represented by the median diameter D50 of the volume particle size distribution in the dispersion.

[0039] The lower limit of the content of the inorganic nanofiller 8 is preferably 1 vol%, more preferably 3 vol%. The upper limit of the content of the inorganic nanofiller 8 is preferably 20 vol%, more preferably 10 vol%. Here, the volume content of the inorganic nanofiller 8 is a percentage obtained by dividing the volume of the inorganic nanofiller 8 by the volume of the thermosetting resin composition 3. If the content of the inorganic nanofiller 8 is less than 1 vol%, the probability of contact with the electrical tree is low, and the effect of suppressing the progression of the electrical tree cannot be fully exerted. On the other hand, if the content of the inorganic filler 8 exceeds 20 vol%, the viscosity of the thermosetting resin composition 3 increases, which tends to reduce the workability when forming the main insulating layer 7.

[0040] Furthermore, the inorganic nanofiller 8 described above may be surface-modified with a coupling agent or coated with a surface treatment agent for the purpose of improving adhesion to the thermosetting resin 1 or improving dispersibility in the thermosetting resin 1. Examples of such coupling agents include silane coupling agents such as γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-glycidyloxypropyltrimethoxysilane, titanate-based coupling agents, and aluminum-based coupling agents. Examples of surface treatment agents include aluminum laurate, aluminum stearate, alumina iron stearate, silica, zirconia, and silicone. These coupling agents or surface treatment agents may be used alone or in combination.

[0041] The other configurations of the thermosetting resin composition 30 according to the second embodiment are the same as those of the thermosetting resin composition 3 according to the first embodiment, and the corresponding parts are given the same reference numerals and the description thereof will be omitted.

[0042] As described above, in the second embodiment of the present invention, the thermosetting resin composition 30 contains the thermosetting resin 1, the organic insulating gas generating agent 2, and the inorganic nanofiller 8. By using the thermosetting resin composition 30 containing the organic insulating gas generating agent 2 for the main insulating layer 7, the partial discharge inception voltage of the main insulating layer is improved compared to when a thermosetting resin composition containing an inorganic insulating gas generating agent is used for the main insulating layer. Furthermore, by including the inorganic nanofiller in the thermosetting resin composition 3, the inorganic nanofiller acts as a physical barrier to electrical trees, causing the electrical trees to branch in a dendritic manner. This slows the propagation rate of the electrical trees and increases the probability of contact with the organic insulating gas generating agent, thereby improving partial discharge resistance. This suppresses partial discharges that occur inside the bubbles during operation of the rotating electric machine, thereby extending the life of the main insulating layer 7.

[0043] As described above, the thermosetting resin composition 30 according to the second embodiment further contains the inorganic nanofiller 8 made of a metal oxide, so that the electrical tree can be branched into a dendritic shape, the propagation speed of the electrical tree can be slowed, and the probability of contact with the organic insulating gas generating agent can be improved, thereby improving the partial discharge resistance characteristics.

[0044] Third Embodiment In a third embodiment, a case will be described in which a stator coil is formed using a main insulating layer using the thermosetting resin composition according to the first and second embodiments of the present application.

[0045] Fig. 3 shows a schematic cross-sectional view of a stator coil 23 according to embodiment 3. As shown in Fig. 3, the stator coil 23 of embodiment 3 is composed of a coil conductor 9 formed by bundling strand conductors, a main insulating layer 7 formed by winding mica tape 6 around the outer layer of the coil conductor 9, and a corona prevention layer 11 formed by winding corona prevention tape around the outer layer of the main insulating layer 7. The thermosetting resin composition 3 of embodiment 1 or the thermosetting resin composition 30 of embodiment 2 is used for the main insulating layer 7. The thermosetting resin composition 3 and the thermosetting resin composition 30 contain an organic insulating gas generating agent 2.

[0046] Next, a description will be given of a manufacturing method of the stator coil 23 according to the present embodiment 3. The manufacturing method of the stator coil 23 uses the coil fixing member 10 and applies a pressure impregnation process and a heat curing process to the core slots 17 using a thermosetting resin composition 3 as an insulating varnish, and includes a shear dispersion process, a mixing process, and a coating process.

[0047] The shear dispersion process is a process in which the organic insulating gas generating agent 2 is added to the thermosetting resin 1 and sheared to disperse the agent in the thermosetting resin 1. The organic insulating gas generating agent 2 typically aggregates as secondary or tertiary particles before being added to the thermosetting resin 1. Therefore, the shear dispersion process is required to crush the secondary or tertiary particles of the organic insulating gas generating agent 2 and disperse them in the thermosetting resin 1. The aggregation and dispersion states of the organic insulating gas generating agent 2 can be adjusted by appropriately setting the shear dispersion conditions. In the shear dispersion process, the thermosetting resin 1 and the organic insulating gas generating agent 2 are mixed by shear force. The device used in the shear dispersion process is not particularly limited as long as it is a mixing device that can apply shear force to the organic insulating gas generating agent 2, and may be appropriately selected from known devices. An example of a device used in the shear dispersion process is a wet high-pressure shear dispersion device.

[0048] The mixing step is a step of adding a curing agent to the thermosetting resin 1 in which the organic insulating gas generating agent 2 has been dispersed, and mixing them. The curing agent is dispersed in the thermosetting resin 1 by the mixing step. The method of mixing the curing agent with the thermosetting resin 1 is not particularly limited, and may be appropriately selected from known methods. For example, after adding the curing agent to the thermosetting resin 1, the curing agent and the thermosetting resin 1 may be mixed using a machine such as a mixer. A thermosetting resin composition 3 is obtained by the above shear dispersion step and mixing step.

[0049] The coating process is a process of coating the stator coil 23 with the thermosetting resin composition 3. The method for coating the thermosetting resin composition 3 is not particularly limited and may be appropriately selected from known methods. Examples of methods for coating the thermosetting resin composition 3 include immersing the stator coil 23 in a container containing the thermosetting resin composition 3. Examples of impregnation methods include vacuum impregnation, vacuum pressure impregnation, and atmospheric pressure impregnation. The conditions for the impregnation process are not particularly limited and may be appropriately set depending on the types of thermosetting resin composition 3, the enameled wire constituting the coil conductor 9, and the like. Another method for coating the thermosetting resin composition 3 is to drop the thermosetting resin composition 3 onto the stator coil 23. After the coating process, the thermosetting resin composition 3 is heated and cured to obtain the stator coil 23 having the main insulating layer 7. The thickness of the main insulating layer 7 is not particularly limited and may be appropriately set depending on the size of the stator coil 23 to be manufactured.

[0050] As described above, in the second embodiment of the present invention, the stator coil 23 is provided with the thermosetting resin composition 3 containing the organic insulating gas generating agent 2 and the main insulating layer 7 using the thermosetting resin composition 30, which has the effect of improving the partial discharge inception voltage, suppressing partial discharge, and ensuring electrical insulation between the iron core and the coil conductor. In addition, it is possible to provide a stator coil that has excellent electrical insulation and reliability even after many years of use.

[0051] As described above, according to the stator coil 23 of the third embodiment, the outer layer of the coil conductor is made of the main insulating layer 7 using the thermosetting resin composition 3, 30 of the first or second embodiment, which has the effect of improving the partial discharge inception voltage, suppressing partial discharge, and ensuring electrical insulation between the iron core and the coil conductor. It is therefore possible to provide a stator coil that has excellent electrical insulation and reliability even after many years have passed.

[0052] Fourth Embodiment In a fourth embodiment, a case will be described in which a rotating electric machine is configured using the stator coil according to the third embodiment of the present invention.

[0053] Fig. 4 is a schematic cross-sectional view of a rotating electric machine 20 according to embodiment 4. As shown in Fig. 4, the rotating electric machine 20 according to embodiment 4 includes, within a frame 21, a gas cooler 22, a stator coil 23 which is an armature, and a rotor 27 which is a field magnet.

[0054] A refrigerant for cooling heat generated by power generation circulates within the frame 21, and the circulating refrigerant is cooled by a gas cooler 22. The stator coil 23 has a cylindrical stator core 24 and a stator winding 25. The stator core 24 is fixed within the frame 21, and the stator winding 25 is fixed to the inner periphery of the stator core 24. Both ends of the stator winding 25 in the axial direction of the stator core 24 protrude from the stator core 24 to form coil ends 26. A main lead is connected to one of the coil ends 26, and the electric power generated by the rotating electric machine 20 is extracted to the outside of the frame 21.

[0055] The rotor 27 has a rotating shaft 28, a rotor core 29, a first retaining ring 30, and a second retaining ring 31. The rotating shaft 28 protrudes axially outward from both axial ends of the rotor core 29, and the rotating shaft 28 and the rotor core 29 are arranged coaxially with the stator core 24. As the rotor 27 rotates, a magnetic field generated from the rotor core 29 crosses the stator winding 25, generating an electromotive force in the stator winding 25 and generating a current. The first retaining ring 30 and the second retaining ring 31 are attached to both axial ends of the rotor core 29 and fix the field winding wound around the rotor core 29.

[0056] As described above, in the fourth embodiment of the present application, the rotating electric machine 20 is configured with a stator coil including the thermosetting resin composition 3 containing the organic insulating gas generating agent 2 and the main insulating layer 7 using the thermosetting resin composition 30. This has the effect of improving the partial discharge inception voltage, suppressing partial discharge, and ensuring electrical insulation between the iron core and the coil conductor. It is therefore possible to provide a rotating electric machine that has excellent electrical insulation properties and reliability even after many years of use.

[0057] As described above, the rotating electric machine 20 according to the fourth embodiment includes the stator coil 23 according to the third embodiment, which has the effect of improving the partial discharge inception voltage, suppressing partial discharge, and ensuring electrical insulation between the iron core and the coil conductor. As a result, it is possible to provide a rotating electric machine that has excellent electrical insulation and reliability even after many years of use.

[0058] In the fourth embodiment of the present application, the thermosetting resin composition 3 of the present disclosure is used for the main insulating layer 7 of the stator coil 23 of the rotating electric machine 20. However, the thermosetting resin composition of the present disclosure may also be used for the insulating layer of the stator coil of a rotating machine other than a rotating electric machine, such as an electric motor, a generator, a compressor, or a servo motor.

[0059] The present application will be described in detail below based on examples, but the present application should not be construed as being limited by the descriptions in these examples.

[0060] Example 1 100 parts by mass of an epoxy resin (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation) was mixed with 5 parts by mass of an organic insulating gas generating agent (ADCA, manufactured by Sankyo Kasei Co., Ltd.) having a decomposition temperature of 160°C while applying shear force. A curing agent (acid anhydride curing agent, manufactured by Showa Denko Materials Co., Ltd.) was added and mixed. The mixture was then heated and dried at 150°C to produce a cured sheet.

[0061] Example 2 100 parts by mass of an epoxy resin (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation) was mixed with 5 parts by mass of an organic insulating gas generating agent (ADCA, manufactured by Sankyo Kasei Co., Ltd.) having a decomposition temperature of 300°C while applying shear force. A curing agent (acid anhydride curing agent, manufactured by Showa Denko Materials Co., Ltd.) was added and mixed. The mixture was then heated and dried at 150°C to produce a cured sheet.

[0062] Comparative Example 1 100 parts by mass of an epoxy resin (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation) was mixed with 5 parts by mass of an organic insulating gas generating agent (ADCA, manufactured by Sankyo Kasei Co., Ltd.) having a decomposition temperature of 140°C while applying shear force. A curing agent (acid anhydride curing agent, manufactured by Showa Denko Materials Co., Ltd.) was added and mixed. The mixture was then heated and dried at 150°C to produce a cured sheet.

[0063] Comparative Example 2 100 parts by mass of epoxy resin (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation) was mixed with 5 parts by mass of an inorganic insulating gas generating agent (calcium carbonate, manufactured by Nitto Funka Kogyo Co., Ltd.) having a decomposition temperature of 600°C as an organic insulating gas generating agent while applying shear force. A curing agent (acid anhydride curing agent, manufactured by Showa Denko Materials Co., Ltd.) was added and mixed. The mixture was then heated and dried at 150°C to produce a cured sheet.

[0064] The ingredients used in the thermosetting resin compositions of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.

[0065]

[0066] A long-term voltage application test (Vt test) was conducted on the thermosetting resin compositions of Examples 1 and 2 and Comparative Examples 1 and 2 to evaluate their voltage resistance characteristics. An earth electrode of an evaluation device was installed on one side of the thermosetting resin composition, and a rod electrode was fixed to one side of the thermosetting resin composition with insulating resin. A voltage of 12.0 kV was applied to the rod electrode, and the insulation life until breakdown was measured. Then, using this procedure, a voltage application test was conducted on the thermosetting resin compositions of Examples 1 and 2 and Comparative Examples 1 and 2, and the insulation life until breakdown was measured.

[0067] The insulation life of the thermosetting resin compositions of Examples 1 and 2 and Comparative Examples 1 and 2 is shown in Table 2.

[0068]

[0069] As shown by the insulation life in Table 2, the thermosetting resin compositions of Examples 1 and 2 have an improved insulation life until dielectric breakdown occurs, compared to the thermosetting resin compositions of Comparative Examples 1 and 2. When the content of the organic insulating gas generating agent relative to 100 parts by mass of the thermosetting resin composition is less than 0.25 parts by mass or exceeds 50 parts by mass, the withstand voltage characteristics are reduced and the insulation life is shorter than that of Example 1.

[0070] Example 1 and Comparative Example 1 are compared. In the thermosetting resin composition of Example 1, ADCA, which has a melting point of 160°C, is filled in an epoxy resin at 5% by mass as an organic insulating gas generating agent. On the other hand, in Comparative Example 1, ADCA, which has a melting point of 140°C, is filled in an epoxy resin at 5% by mass as an organic insulating gas generating agent. As shown by the insulation life in Table 2, in Example 1, the organic insulating gas generating agent dispersed in the epoxy resin decomposes due to a local temperature increase caused by partial discharge, improving the partial discharge inception voltage and suppressing partial discharge, thereby extending the insulation life. However, in Comparative Example 1, the decomposition temperature of the organic insulating gas generating agent is lower than the curing temperature of the thermosetting resin, and the organic insulating gas generating agent decomposes and forms bubbles during the heat curing process, making partial discharge more likely to occur and shortening the insulation life.

[0071] Example 1 and Comparative Example 2 are compared. In the thermosetting resin composition of Example 1, ADCA, which has a melting point of 210°C, is filled in an epoxy resin at 5% by mass as an organic insulating gas generating agent. On the other hand, in Comparative Example 2, calcium carbonate, which has a melting point of 600°C, is filled in an epoxy resin at 5% by mass as an inorganic insulating gas generating agent. As shown by the insulation life in Table 2, in Example 1, the organic insulating gas generating agent dispersed in the epoxy resin decomposes due to a local temperature rise caused by partial discharge, improving the partial discharge inception voltage and suppressing partial discharge, thereby extending the insulation life. However, in Comparative Example 2, the decomposition temperature of the organic insulating gas generating agent is high and the time of exposure to the temperature rise caused by discharge energy is long, resulting in a shortened insulation life.

[0072] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0073] 1 Thermosetting resin, 2 Organic insulating gas generating agent, 3 Thermosetting resin composition, 23 Stator coil, 20 Rotating electric machine.

Claims

1. A stator coil using a thermosetting resin composition containing a thermosetting resin, a curing agent for curing the thermosetting resin, and an organic insulating gas generating agent for generating an insulating gas by thermal decomposition, the thermosetting resin composition contains the organic insulating gas generating agent that generates the insulating gas other than oxygen gas at a temperature higher than a curing temperature of the thermosetting resin and not higher than 300° C., A stator coil, wherein an outer layer of a coil conductor is constituted by a main insulating layer using the above-mentioned thermosetting resin composition.

2. 2. The stator coil according to claim 1, wherein the organic insulating gas generating agent is at least one of azodicarbonamide, dinitrosopentamethylenetetramine, and oxybisbenzenesulfonylhydrazide.

3. 2. The stator coil according to claim 1, wherein the organic insulating gas generating agent has an average particle size of 1 μm or more and 50 μm or less.

4. 2. The stator coil according to claim 1, wherein the insulating gas generated from the organic insulating gas generating agent is at least one of nitrogen gas, carbon dioxide gas, carbon monoxide gas, and ammonia gas.

5. 2. The stator coil according to claim 1, wherein the content of the organic insulating gas generating agent is 0.25 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the thermosetting resin.

6. 2. The stator coil according to claim 1, further comprising an inorganic nano-filler made of a metal oxide.

7. The stator coil according to claim 6, wherein the inorganic nanofiller has an average particle size of 0.5 nm or more and 1 μm or less.

8. The stator coil according to claim 6 , wherein a surface of the inorganic nano-filler is modified with a coupling agent or coated with a surface treatment agent.

9. A rotating electric motor comprising a stator coil described in any one of claims 1 to 8.