Rotating electric machine

Abstract

This rotating electric machine comprises: a coil conductor (7) which is housed in a slot (4) provided in a stator core (2) while leaving the end portions thereof and on the outer periphery of which a main insulating layer (8) is formed; a low-resistance corona shield layer (9) that is formed on an outer peripheral surface of the main insulating layer (8) of the coil conductor (7), makes contact with the stator core (2) inside the slot (4), and is provided extending from the inside to the outside of the slot (4); a non-linear resistance layer (10) provided such that a part thereof is overlapped with the outer end of the low-resistance corona shield layer (9); and a protection layer (11) provided so as to cover the low-resistance corona shield layer (9) outside the slot (4) and the non-linear resistance layer (10). The protection layer (11) contains a non-linear resistance material and a resin.

Description

Technical Field

[0001] This application relates to a rotating electric machine.

Background Art

[0002] Large rotating machines typified by turbine generators are required to have high insulation performance that clears the withstand voltage test imposed before shipment and does not cause insulation abnormalities during decades of operation. Among them, for the stator coil to which a high voltage is applied, the following structure is generally adopted to suppress partial discharge during the withstand voltage test and normal operation and insulation abnormalities caused thereby.

[0003] The stator coil forms a main insulation layer by winding a mica tape having extremely excellent corona discharge resistance characteristics around the coil conductor and further impregnating and curing a thermosetting resin such as an epoxy resin. Further, in the outermost peripheral portion of this main insulation layer, a low-resistance corona shield layer having semiconductive properties is provided in a portion housed inside the slot of the stator core and a part outside the slot. This low-resistance corona shield layer has a function of eliminating the potential difference between the stator core at ground potential and the outermost layer of the stator coil and suppressing discharge inside the slot.

[0004] On the other hand, the portion where the stator coil exits the slot is generally called the coil end. The surface potential of the coil end rises in the longitudinal direction of the coil from the end of the low-resistance corona shield layer at ground potential. For the purpose of relaxing the rising rate, that is, the electric field along the coil surface and suppressing the occurrence of surface discharge, a non-linear resistance layer is provided so as to overlap a part of the end of the low-resistance corona shield layer. The non-linear resistance layer has a characteristic that the resistivity decreases non-linearly as the electric field value applied to the non-linear resistance material increases. The non-linear resistance material used in large rotating machines is generally composed of silicon carbide (SiC) particles mixed in an insulating resin, and is wound around the coil surface in a tape shape in a semi-cured state and thermally cured, or a paint-like material is applied to the coil surface and dried. Either method is used.

[0005] In the withstand voltage test imposed on large, high-voltage rotating machines before product shipment, a test voltage of twice the rated voltage plus 1kV is applied to the stator coil conductors. In this case, the charging current that charges the capacitance of the main insulating layer flows inside the nonlinear resistive layer on the surface of the stator coil end, and Joule heating occurs due to the resistive component of the nonlinear resistive material, resulting in localized heat generation. When the nonlinear resistive material exceeds a predetermined temperature determined by its material properties, it burns out, loses its electric field relaxation function, and surface discharge occurs. Even if burnout does not occur, the resistance increases with rising temperature, so the surface electric field increases, making surface discharge more likely. As a method to reduce heat generation during the withstand voltage test and stabilize the electric field relaxation function, a method of applying multiple nonlinear resistive materials with different resistivity has been published. Furthermore, a protective coating made by dissolving epoxy resin in a solvent and mixing it with a colorant is applied to these low-resistance corona shield layer and nonlinear resistive layer, protecting the coil from dust and allowing for abnormality detection due to discoloration during overheating.

[0006] For example, Patent Document 1 discloses applying a high-resistance paint for electric field relaxation, which has voltage nonlinear resistance characteristics, as a protective layer against surface discharge to the outer periphery of a low-resistance corona shield layer located outside the slot. Patent Document 2 also discloses forming a buffer resistance corona shield layer using a protective paint or the like from the edge of the low-resistance corona shield layer to the high-resistance corona shield layer region. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-193727 (paragraphs 0048-0055, Figure 8) [Patent Document 2] Japanese Patent Publication No. 2003-92849 (paragraphs 0011-0013, Figure 1) [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in the conventional configurations shown in Patent Documents 1 and 2, the protective coating is not applied so as to completely cover the top of the low-resistance corona shield layer and the nonlinear resistance layer, which has the problem that the surface discharge suppression effect may be reduced.

[0009] This invention was made to solve the above-mentioned problems and aims to provide a rotating electric machine with excellent insulation performance in the low-resistance corona shield layer and the nonlinear resistance layer. [Means for solving the problem]

[0010] The rotating electric machine disclosed herein comprises a coil conductor housed in a slot provided in an iron core, with its ends exposed, and having an insulating layer formed on its outer circumference; a corona shield layer formed on the outer surface of the insulating layer of the coil conductor, in contact with the iron core inside the slot, and extending from the inside of the slot to the outside; a nonlinear resistance layer partially overlapping the outer end of the corona shield layer; and a protective layer provided to cover the corona shield layer and the nonlinear resistance layer on the outside of the slot, wherein the protective layer comprises a nonlinear resistance material and a resin , and coloring agents Includes Furthermore, the mixing ratio of the nonlinear resistive material and the resin is in the range of 0.9 to 1.8:1.0. It is characterized by the following: [Effects of the Invention]

[0011] According to this invention, surface discharge propagation can be suppressed, and a rotating electric machine with high insulation reliability can be obtained. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view showing the configuration of a rotating electric machine according to Embodiment 1. [Figure 2] This is a perspective view showing the main components near the stator slot exit of the stator of a rotating electric machine according to Embodiment 1. [Figure 3] This is a cross-sectional view showing the configuration of the coil end main part of a rotating electric machine according to Embodiment 1. [Figure 4]This figure illustrates the mixing ratio of the nonlinear resistive material in the protective layer of a rotating electric machine according to Embodiment 1. [Modes for carrying out the invention]

[0013] The embodiments of the rotating electric machine according to the present application will be described in detail below with reference to the drawings. In the following description of embodiments, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their descriptions will be omitted. However, the present application is not limited by these embodiments.

[0014] Embodiment 1. Figure 1 is a cross-sectional view showing the configuration of a rotating electric machine according to Embodiment 1 of the present application. As shown in Figure 1, the rotating electric machine 100 consists of a stator 1 and a rotor 6. The stator core 2 is provided with slots 4, in which stator coils 3a and 3b are housed. Of the stator coils 3a and 3b, which are partially housed in slots 4, the portion that protrudes outside the slots is called a coil end 5.

[0015] Figure 2 is a schematic perspective view showing the insulating structure near the slot exit of the stator core of a rotating electric machine according to Embodiment 1 of the present invention. As shown in Figure 2, the stator coils 3a and 3b are provided with a main insulating layer 8 formed by winding a mica tape with excellent corona resistance properties around the outer circumference of a coil conductor 7, which is made up of multiple bundled strand conductors, a predetermined number of times, impregnating it with a thermosetting resin such as epoxy resin under pressure in a vacuum, and then performing a heat curing treatment. Furthermore, a low-resistance corona shield layer 9 is provided in the outermost part of the main insulating layer 8, specifically in the portion housed in the slot 4 and in a portion that extends outside the slot 4, in order to eliminate the potential difference between the stator core 2, which is at ground potential, and the outermost part of the stator coils 3a and 3b, and to suppress partial discharge.

[0016] The surface potential of the coil ends 5 where the stator coils 3a and 3b emerge from the slots 4 starts to rise from the end of the low-resistance corona shield layer 9 at ground potential in the longitudinal direction of the coil, and eventually reaches the same potential as the coil conductor 7. Near the end of the low-resistance corona shield layer 9, due to the structure, the creeping electric field along the coil surface becomes high, making it a location prone to partial discharge. For the purpose of relaxing the electric field along the coil surface and suppressing the occurrence of creeping discharge, a non-linear resistance layer 10 is provided to overlap a part of the end of the low-resistance corona shield layer 9.

[0017] The non-linear resistance layer 10 is generally applied with a functional material called a non-linear resistance material, which has the characteristic that the resistivity of the material decreases non-linearly as the applied electric field value increases. For non-linear resistance materials used in large rotating machines such as turbine generators, those in which silicon carbide (SiC) grains with a particle size of about several micrometers to several tens of micrometers are dispersed in an insulating resin are used. As a manufacturing method of the non-linear resistance layer 10, there is a method of winding a mixture of silicon carbide grains and an insulating resin in a semi-cured state in a tape shape around the coil surface and thermally curing it. Also, there is a method of applying a mixture of silicon carbide grains and an insulating resin on the coil surface in a state before curing and drying it to form.

[0018] In the withstand voltage test of a large rotating machine, a test voltage of twice the rated voltage plus 1 kV is applied to the stator coil conductor. The rated voltage of a turbine generator depends on the generator capacity, but is about 15 kV to 30 kV (rms value). That is, the test voltage during the withstand voltage test is 31 kV to 61 kV. If the non-linear resistance layer 10 applied on the coil surface is properly formed and functions normally, the creeping electric field of the coil is relaxed, so creeping discharge does not occur. However, there are the following problems in the withstand voltage test in which a high voltage is applied to the coil conductor 7.

[0019] When a test voltage is applied, the distance of the non-linear resistance layer 10 required for electric field relaxation, that is, the coil surface potential along the non-linear resistance layer 10, increases from the ground potential at the end of the low-resistance corona shield layer 9 to the same potential as the coil conductor 7. In that case, the charging current for charging the capacitance of the main insulation layer 8 formed between the non-linear resistance layer 10 and the coil conductor 7 flows through the inside of the non-linear resistance layer 10, and Joule heat is generated due to the resistance component of the non-linear resistance layer 10. When the non-linear resistance material exceeds a predetermined temperature determined by its material properties, it burns out and loses its electric field relaxation function, resulting in creeping discharge on the coil surface. Even if it does not reach burnout, as the material temperature rises, the non-linear resistance characteristics, that is, the characteristics in which the resistivity decreases as the electric field increases, become smaller, and it substantially becomes a high resistance. Therefore, as a result, the creeping electric field becomes high, and the possibility of reaching creeping discharge on the coil surface increases.

[0020] FIG. 3 is a cross-sectional view showing the configuration of a main part of a coil end of a rotating electric machine according to Embodiment 1 of the present application. As shown in FIG. 3, in the coil end 5 of the rotating electric machine 100, a protective layer 11 is provided so as to cover the upper portions of the low-resistance corona shield layer 9 and the non-linear resistance layer 10. The protective layer 11 is formed by dissolving a resin such as epoxy in a solvent and applying a protective paint in which a coloring agent and a non-linear resistance material are dispersed. As the non-linear resistance material, silicon carbide grains having a particle size of about several micrometers to several tens of micrometers are used.

[0021] Regarding the mixing ratio of the non-linear resistance material with the insulating resin, it is preferable to disperse the silicon carbide grains in the insulating resin at a ratio of 0.9 to 1.8:1.0 with respect to the ratio of the silicon carbide grains to the epoxy resin. FIG. 4 is a diagram for explaining the mixing ratio of the non-linear resistance material of the protective layer in the rotating electric machine according to Embodiment 1 of the present application.

[0022] When the mixing ratio of the nonlinear resistive materials falls below 0.9:1.0, the discharge power exceeds 0.05W (threshold A), as shown in Figure 4, and discharge occurs. In addition, since the paint forming the protective layer 11 contains a colorant, the colorant changes color when overheated, making it possible to detect abnormalities. However, when the mixing ratio of the nonlinear resistive materials exceeds 1.8:1.0, it becomes difficult to distinguish the color change when overheated.

[0023] This configuration covers the coil with a protective coating that contains nonlinear resistance, low resistance The corona shield layer 9 and the nonlinear resistance layer 10 are heated by Joule heating. high Even if resistance is introduced, the protective layer 11, which is mixed with a nonlinear resistive material, has an electric field mitigation effect, thereby reducing the creepage electric field and suppressing the progression of creepage discharge between coils. Furthermore, it protects the coils from dust and moisture during the manufacturing of the rotating electric machine 100 and suppresses discharge that occurs between coils. In addition, the coloring agent changes color when overheating occurs, enabling abnormality detection.

[0024] In this embodiment 1, silicon carbide was used as the nonlinear resistive material, but it is not limited to this. For example, similar effects can be obtained by using alumina (Al2O3) or zinc oxide (ZnO).

[0025] As described above, the rotating electric machine 100 according to this embodiment 1 comprises a coil conductor 7 housed in a slot 4 provided in the stator core 2, with its ends remaining, and having a main insulating layer 8 formed on its outer circumference; a low-resistance corona shield layer 9 formed on the outer surface of the main insulating layer 8 of the coil conductor 7, in contact with the stator core 2 inside the slot 4, and extending from the inside to the outside of the slot 4; a nonlinear resistance layer 10 partially overlapping the outer end of the low-resistance corona shield layer 9; and a protective layer 11 provided to cover the low-resistance corona shield layer 9 and the nonlinear resistance layer 10 on the outside of the slot 4. The protective layer 11 includes a nonlinear resistance material and a resin. low resistance The corona shield layer and nonlinear resistance layer are heated by Joule heating. highEven if resistance is introduced, the protective layer containing nonlinear resistive material has an electric field relaxation effect, which reduces the creepage electric field and suppresses the discharge power between coils while suppressing the progression of creepage discharge between coils.

[0026] While this application describes various exemplary embodiments, the various features, aspects, and functions described in the embodiments are not limited to the application of any particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated in this specification are conceivable within the scope of the art disclosed herein. For example, these include modifying, adding, or omitting at least one component, or even extracting at least one component and combining it with other components. [Explanation of Symbols]

[0027] 1 Stator, 2 Stator core, 3a, 3b Stator coils, 4 Slots, 5 Coil ends, 6 Rotor, 7 Coil conductors, 8 Main insulation layer, 9 Low-resistance corona shield layer, 10 Nonlinear resistance layer, 11 Protective layer, 100 Rotating electric machine.

Claims

[Claim 1] A coil conductor is housed in a slot provided in an iron core, leaving its ends exposed, and has an insulating layer formed on its outer circumference. A corona shield layer is formed on the outer surface of the insulating layer of the coil conductor, is in contact with the iron core inside the slot, and extends from the inside of the slot to the outside, A nonlinear resistive layer is provided, partially overlapping the outer edge of the corona shield layer, A protective layer is provided so as to cover the corona shield layer and the nonlinear resistance layer on the outer side of the slot, Equipped with, The rotating electric machine is characterized in that the protective layer comprises a nonlinear resistive material, a resin, and a colorant, and the mixing ratio of the nonlinear resistive material and the resin is in the range of 0.9 to 1.8:1.0.

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