Rotating electric machine

Abstract

A rotating electrical machine is provided with: a coil conductor (7) housed with an end in a slot (4) provided in a stator core (2), the coil conductor (7) having a main insulating layer (8) formed on the outer periphery thereof; a low-resistance corona shield layer (9) which is formed on the outer peripheral surface of the main insulating layer (8) of the coil conductor (7), is provided so as to be in contact with the stator core (2) inside the slots (4), and extends from the inside to the outside of the slots (4); a non-linear resistive layer (10) provided so as to partially overlap the outer end of the low-resistance corona shield layer (9); and a protective layer (11) provided so as to cover the low-resistance corona shield layer (9) and the non-linear resistance layer (10) on the outer side of the groove (4), the protective layer (11) containing a non-linear resistance material and a resin.

Description

Technical Field

[0001] The present application relates to rotating electrical machines. Background Art

[0002] Large rotating machines such as turbine generators are required to pass the withstand voltage test before shipment and have high insulation performance without insulation abnormalities during decades of operation. In particular, in the stator coils to which high voltage is applied, the following structure is generally adopted to suppress partial discharge during withstand voltage tests and normal operation, and insulation abnormalities caused by this.

[0003] The stator coil is formed by winding a mica tape having excellent corona discharge resistance around the coil conductor, and then impregnating and curing a thermosetting resin such as epoxy resin to form a main insulation layer. In addition, a semi-conductive low-resistance corona shielding layer is provided on the outermost circumference of the main insulation layer, which is accommodated in the slot of the stator core and a part outside the slot. The low-resistance corona shielding layer has the function of eliminating the potential difference between the stator core as the ground potential and the outermost layer of the stator coil, and suppressing discharge inside the slot.

[0004] On the other hand, the portion of the stator coil extending from the slot is generally referred to as the coil end. The surface potential of the coil end rises from the end of the low-resistance corona shield layer, which is the ground potential, toward the long side of the coil. In order to mitigate the rising ratio, that is, the electric field along the coil surface, and suppress the generation of surface discharge, a nonlinear resistance layer is provided in a manner overlapping a portion of the end of the low-resistance corona shield layer. The nonlinear resistance layer has the characteristic that the resistivity decreases nonlinearly as the electric field value applied to the nonlinear resistance material increases. The nonlinear resistance material used in large rotating machines is generally composed of silicon carbide (SiC) particles mixed in an insulating resin, and is either wound around the coil surface in a semi-cured state in a strip shape and thermally cured, or coated on the coil surface with a paint-like material and dried.

[0005] In the withstand voltage test applied to the products of large high-voltage rotating machines before shipment, 1 kV plus twice the rated voltage is applied to the stator coil conductor as the test voltage. At this time, the charging current that charges the electrostatic capacitance of the main insulation layer flows inside the nonlinear resistance layer on the surface of the stator coil end, and Joule heating is generated by the resistance component of the nonlinear resistance material, resulting in local heating. The nonlinear resistance material burns when the temperature exceeds the specified temperature determined by the physical properties of the material, loses the electric field relaxation function, and generates surface discharge. In addition, even if it does not burn, the surface electric field becomes higher due to the high resistance as the temperature rises, resulting in a higher possibility of surface discharge. As a method for reducing the heat generation during the withstand voltage test and stabilizing the electric field relaxation function, a method of applying multiple nonlinear resistance materials with different resistivities is disclosed. In addition, a protective coating in which an epoxy resin dissolved in a solvent and mixed with a colorant is applied to these low-resistance corona shielding layers and nonlinear resistance layers, which becomes a structure that protects the coil from dust while performing abnormal detection of color change associated with overheating.

[0006] For example, Patent Document 1 discloses that a high-resistance coating material for electric field relaxation having a voltage nonlinear resistance characteristic is applied to the periphery of a low-resistance corona shield layer located outside a groove as a protective layer against surface discharge. In addition, Patent Document 2 discloses that a buffer resistance corona shield layer is formed from the end of the low-resistance corona shield layer to the high-resistance corona shield layer region using a protective coating material or the like. Prior art literature Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-193727 (Paragraphs 0048 to 0055, FIG. 8 ) Patent Document 2: Japanese Patent Laid-Open No. 2003-92849 (Paragraphs 0011 to 0013, Figure 1 ) Summary of the invention Technical problem to be solved by the invention

[0008] However, the conventional structures shown in Patent Documents 1 and 2 have a problem in that the protective coating is not applied to completely cover the upper portions of the low-resistance corona shield layer and the nonlinear resistance layer, and the creeping discharge suppression effect may be reduced.

[0009] The present application is made to solve the above-mentioned problems, and its object is to provide a rotating electric machine having excellent insulation performance of a low-resistance corona shield layer and a nonlinear resistance layer. Technical means for solving technical problems

[0010] The rotating electric machine disclosed in the present application is characterized in that it includes: a coil conductor, which is accommodated in a slot provided in an iron core with an end portion left and an insulating layer formed on the outer periphery; a corona shielding layer, which is formed on the outer peripheral surface of the insulating layer of the coil conductor and is provided to contact the iron core inside the slot and extend from the inside of the slot to the outside; a nonlinear resistance layer, which is provided so that a portion of the nonlinear resistance layer overlaps with the outer end of the corona shielding layer; and a protective layer, which is provided in a manner covering the corona shielding layer on the outer side of the slot and the nonlinear resistance layer, and the protective layer contains a nonlinear resistance material and a resin. Effects of the Invention

[0011] According to the present application, the progress of creeping discharge can be suppressed, and a rotating electric machine with high insulation reliability can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view showing the structure of the rotating electrical machine according to the first embodiment. Figure 2 It is a perspective view showing the main part structure near the stator slot outlet of the stator of the rotating electric machine according to the first embodiment. Figure 3 It is a cross-sectional view showing the structure of a main part of a coil end portion of the rotating electrical machine according to the first embodiment. Figure 4 This is a diagram for explaining the mixing ratio of the nonlinear resistance material of the protective layer in the rotating electric machine according to the first embodiment. DETAILED DESCRIPTION

[0013] Hereinafter, an embodiment of the rotary electric machine involved in the present application will be described in detail based on the drawings. In the following description of the embodiment, the same reference numerals are given to the same or corresponding parts in the drawings, and the description thereof is omitted. In addition, the present application is not limited to the embodiment.

[0014] Implementation method 1. Figure 1 1 is a cross-sectional view showing the structure of the rotating electrical machine according to the first embodiment of the present application. Figure 1 As shown, the rotating electric machine 100 is composed of a stator 1 and a rotor 6. The stator core 2 is provided with slots 4 to accommodate stator coils 3a and 3b. The portions of the stator coils 3a and 3b partially accommodated in the slots 4 and exposed outside the slots are called coil ends 5.

[0015] Figure 2 1 is a perspective view schematically showing an insulation structure near a slot outlet of a stator core of a rotating electrical machine according to Embodiment 1 of the present application. Figure 2As shown, the stator coils 3a and 3b are provided with a main insulating layer 8 on the outer periphery of a coil conductor 7 in which a plurality of wire conductors are bundled. The main insulating layer 8 is formed by winding a mica tape having excellent corona resistance for a predetermined number of times, pressurizing and impregnating a thermosetting resin such as epoxy resin in a vacuum, and performing a heat curing treatment. In addition, a low-resistance corona shielding layer 9 is provided on the outermost periphery of the main insulating layer 8, the portion accommodated in the slot 4, and the portion exposed outside the slot 4, in order to eliminate the ground potential, that is, the potential difference between the stator core 2 and the outermost periphery of the stator coils 3a and 3b, and suppress partial discharge.

[0016] The surface potential of the coil end 5 of the stator coil 3a, 3b coming out of the slot 4 starts to rise from the end of the low-resistance corona shield layer 9, which is at the ground potential, toward the long side of the coil, and soon becomes the same potential as the coil conductor 7. The vicinity of the end of the low-resistance corona shield layer 9 is a location where the surface electric field along the coil surface becomes high and partial discharge is easily generated. In order to mitigate the electric field along the coil surface and suppress the generation of surface discharge, the nonlinear resistance layer 10 is provided in a manner overlapping a portion of the end of the low-resistance corona shield layer 9.

[0017] The nonlinear resistor layer 10 generally adopts a functional material called a nonlinear resistor material, which has the characteristic that the resistivity of the material decreases nonlinearly as the applied electric field value increases. For nonlinear resistor materials used in large rotating machines such as turbine generators, a material in which silicon carbide (SiC) particles with a particle size of several microns to tens of microns are dispersed in an insulating resin is used. As a method for making the nonlinear resistor layer 10, there is a method in which a mixture of silicon carbide particles and insulating resin is made into a strip-shaped material in a semi-cured state and is wound on the surface of a coil and thermally cured. In addition, there is a method in which the mixture of silicon carbide particles and insulating resin is applied to the surface of a coil in a state before curing and dried.

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

[0019] When the test voltage is applied, the distance of the nonlinear resistance layer 10 required for electric field relaxation, that is, the distance required for the coil surface potential along the nonlinear resistance layer 10 to rise from the ground potential at the end of the low-resistance corona shield layer 9 to the same potential as the coil conductor 7, becomes very long. In this case, the charging current for charging the electrostatic capacitance of the main insulating layer 8 formed between the nonlinear resistance layer 10 and the coil conductor 7 flows inside the nonlinear resistance layer 10, and Joule heating is generated by the resistance component of the nonlinear resistance layer 10. When the nonlinear resistance material exceeds the specified temperature determined by the physical properties of the material, it burns, loses the electric field relaxation function, and generates surface discharge on the coil surface. In addition, even if it does not burn, as the material temperature rises, the nonlinear resistance characteristic, that is, the characteristic that the resistivity decreases according to the increase of the electric field, becomes smaller, and the resistance is actually high. Therefore, as a result, the surface electric field becomes higher, and the possibility of achieving surface discharge on the coil surface becomes higher.

[0020] Figure 3 1 is a cross-sectional view showing the structure of the main part of the coil end of the rotating electric machine involved in the first embodiment of the present application. Figure 3 As shown, a protective layer 11 is provided on the coil end 5 of the rotating electric machine 100 so as to cover the upper part of the low resistance corona shield layer 9 and the nonlinear resistor layer 10. The protective layer 11 is formed by dissolving a resin such as epoxy resin in a solvent and applying a protective coating in which a colorant and a nonlinear resistor material are dispersed. The nonlinear resistor material uses silicon carbide particles with a particle size of several micrometers to tens of micrometers.

[0021] Regarding the mixing ratio of the nonlinear resistor material and the insulating resin, it is preferred that the ratio of silicon carbide particles to epoxy resin be 0.9 to 1.8:1.0, so that the silicon carbide particles are dispersed in the insulating resin. Figure 4 This is a diagram for explaining the mixing ratio of the nonlinear resistance material of the protective layer in the rotating electric machine according to the first embodiment of the present application.

[0022] When the mixing ratio of the nonlinear resistor material is lower than the ratio of 0.9:1.0, such as Figure 4 As shown, the discharge power is 0.05W (threshold A) or more, and discharge occurs. In addition, since a colorant is mixed in the coating material forming the protective layer 11, the colorant changes color when overheated, and abnormality detection can also be performed. However, if the mixing ratio of the nonlinear resistance material exceeds the ratio of 1.8:1.0, the color change during overheating is difficult to distinguish.

[0023] According to this structure, since the coil is covered with a protective coating mixed with a nonlinear resistor, even if the resistance layer corona shield layer 9 and the nonlinear resistor layer 10 are reduced in resistance due to Joule heating, the protective layer 11 mixed with the nonlinear resistor material has an electric field relaxation effect, thereby having the effect of reducing the surface electric field and suppressing the development of surface discharge between the coils. In addition, it has the effect of protecting the coil from dust and moisture when manufacturing the rotating electric machine 100, and suppressing the discharge generated between the coils. In addition, since the colorant changes color when overheated, abnormality detection can also be performed.

[0024] In the first embodiment, silicon carbide is used as the nonlinear resistor material, but the nonlinear resistor material is not limited to this. For example, aluminum oxide (Al 2 O 3 ) or zinc oxide (ZnO) can also achieve the same effect.

[0025] As described above, according to the rotating electric machine 100 involved in the present first embodiment, the coil conductor 7 is accommodated in the slot 4 provided in the stator core 2 with the end portion left, and the main insulating layer 8 is formed on the outer periphery; the low-resistance corona shield layer 9 is formed on the outer peripheral surface of the main insulating layer 8 of the coil conductor 7, and is provided to contact with the stator core 2 inside the slot 4 and extend from the inside of the slot 4 to the outside; the nonlinear resistance layer 10 is provided so as to partially overlap with the outer end of the low-resistance corona shield layer 9; and the protective layer 11 is provided so as to cover the low-resistance corona shield layer 9 and the nonlinear resistance layer 10 on the outer side of the slot 4, and the protective layer 11 contains a nonlinear resistance material and a resin. Therefore, even if the resistance layer corona shield layer and the nonlinear resistance layer are reduced in resistance due to Joule heating, the protective layer containing the nonlinear resistance material has an electric field relaxation effect, thereby reducing the surface electric field, suppressing the development of surface discharge between the coils, and suppressing the discharge power between the coils.

[0026] Although various exemplary embodiments are described in this application, the various features, methods and functions described in the embodiments are not limited to the application of specific embodiments, but can be applied to the embodiments alone or in various combinations. Therefore, it can be considered that countless variations that are not illustrated are also included in the technical scope disclosed in the specification of this application. For example, it is set to include the case where at least one structural element is deformed, added or omitted, and the case where at least one structural element is extracted and combined with other structural elements. Description of symbols

[0027] 1 stator, 2 stator core, 3a, 3b stator coil, 4 slot, 5 coil end, 6 rotor, 7 coil conductor, 8 main insulation layer, 9 low resistance corona shielding layer, 10 nonlinear resistance layer, 11 protective layer, 100 rotating motor.

Claims

1. A rotating electrical machine, characterized in that: include: a coil conductor which is received in a slot provided in the core with its end portion left, and has an insulating layer formed on the outer periphery; a corona shielding layer formed on an outer peripheral surface of an insulating layer of the coil conductor, arranged to contact the core inside the slot and extending from the inside of the slot to the outside; a nonlinear resistance layer, the nonlinear resistance layer being arranged to partially overlap with an outer end of the corona shielding layer; as well as a protective layer provided so as to cover the corona shielding layer on the outer side of the groove and the nonlinear resistor layer, The protection layer includes a non-linear resistance material and a resin.

2. The rotating electrical machine according to claim 1, characterized in that The protective layer contains a colorant.

3. The rotating electrical machine according to claim 2, characterized in that The mixing ratio of the nonlinear resistance material and the resin in the protective layer is in the range of 0.9 to 1.8:1.0.

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