Method for improving end current-carrying capacity of stator bar structure by designing stator bar structure

Abstract

The invention relates to the technical field of motor structures, in particular to a method for improving the end current-carrying capacity of a stator bar structure by designing the stator bar structure, which comprises the following steps of: processing a low-resistance anti-corona layer on a bar body after the bar body is processed and before a stator core is connected to the bar body; the low-resistance anti-corona layer is tightly attached to and wraps the outer surface of the winding bar body, and the low-resistance anti-corona layer is located between the stator core and the winding bar body; the high-resistance anti-corona unit is processed on the wire rod body, the current transmitted along the axial direction of the wire rod body is guided to the low-resistance anti-corona layer through the high-resistance anti-corona unit, and the current is guided into the stator core through the low-resistance anti-corona layer. According to the technical scheme, the process is simple, anti-corona treatment such as extra paint brushing is not needed, and the method has important significance in improving the production efficiency of the stator bar.

Description

[0001] Technical Domain

[0002] The present invention relates to the field of motor structure technology, and in particular to a method for improving the end current carrying capacity of a stator bar by designing the stator bar structure. Background Art

[0003] With the continuous development of my country's power industry, the market has great demand for large-capacity and high-rated voltage steam turbine generator sets. At present, the rated voltage of the generator sets put into operation in my country is 27kV, and the factory AC withstand voltage test voltage of the stator wire bar is as high as 108kV. At this time, the performance of the stator wire bar anti-corona system is particularly critical. In recent years, steam turbine generator sets with a rated voltage of 30kV and wind turbine generator sets with a rated voltage of 35kV have gradually begun to be developed, and the traditional stator wire bar anti-corona structure may not meet the test requirements.

[0004] At present, the main technical solutions for anti-corona treatment of high-voltage motor stator wire bars are: single-layer anti-corona structure, double-layer anti-corona structure, coated anti-corona structure, etc. These structures have been mature and widely used in high-voltage motor stator wire bars with rated voltage below 27kV. However, for high-voltage motor stator wire bars with higher rated voltages, when the stator wire bars are subjected to factory power frequency AC withstand voltage test and anti-corona test, the field strength on the surface of the stator wire bar end is concentrated and the current density is large, which makes it very easy to cause end corona, flashover and anti-corona layer erosion. The product yield is low, which is not conducive to large-scale production. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and propose a method for improving the current carrying capacity of the end of a stator wire bar by designing a stator wire bar structure. The stator wire bar structure is connected to a double-layer anti-corona layer through a voltage equalizing ring. While improving the uniformity of the electric field distribution at the end of the stator wire bar, the leakage current at the end of the wire bar can be evenly distributed in the double-layer anti-corona layer, thereby improving the current carrying capacity of the anti-corona layer and reducing the risks of end corona, flashover and anti-corona layer ablation.

[0006] The above objectives are achieved through the following technical solutions:

[0007] The method for improving the end current carrying capacity of a stator bar by designing the stator bar structure comprises the following steps:

[0008] S1, preparing processing materials for the wire rod body, stator core, low-resistance anti-corona layer and high-resistance anti-corona unit;

[0009] S2, after the wire rod body is processed and before the stator core is connected to the wire rod body, a low-resistance anti-corona layer is processed on the wire rod body, so that the low-resistance anti-corona layer is tightly wrapped around the outer surface of the wire rod body, and the low-resistance anti-corona layer is between the stator core and the wire rod body;

[0010] S3, a high-resistance anti-corona unit is processed on the wire rod body, and the high-resistance anti-corona unit is used to guide the current transmitted axially along the wire rod body to the low-resistance anti-corona layer, and then introduced into the stator core by the low-resistance anti-corona layer; wherein the high-resistance anti-corona unit is arranged side by side with the low-resistance anti-corona layer along the length direction of the wire rod body, and the inner surface of the head end of the high-resistance anti-corona unit transitionally overlaps the outer surface of the tail end of the low-resistance anti-corona layer.

[0011] Preferably, in step S2, the processed wire rod body includes a copper conductor and a ground insulation layer, and the ground insulation layer is tightly wrapped around the surface of the copper conductor.

[0012] Preferably, in step S3, processing the high-resistance anti-corona unit on the wire rod body comprises the following steps:

[0013] S31, firstly process a high-resistance anti-corona layer I on the surface of the wire rod body, and the high-resistance anti-corona layer I is tightly wrapped on the outer surface of the wire rod body as the first flow path of the end leakage current;

[0014] S32, processing an isolation layer on the surface of the high-resistance anti-corona layer I, wherein the isolation layer is closely attached to the outer surface of the high-resistance anti-corona layer I for path isolation;

[0015] S33, processing a high-resistance anti-corona layer II on the surface of the high-resistance anti-corona layer I and the isolation layer, and the high-resistance anti-corona layer II covers and wraps the outside of the high-resistance anti-corona layer I and the isolation layer to serve as a second flow path for the end leakage current.

[0016] Preferably, in step S3, the high-resistance anti-corona layer I and the high-resistance anti-corona layer II are respectively transitionally overlapped with the outer surface of the tail end of the low-resistance anti-corona layer, and the transition overlap width between the high-resistance anti-corona layer I and the low-resistance anti-corona layer is not less than 20 mm, and the transition overlap width between the high-resistance anti-corona layer II and the low-resistance anti-corona layer is not less than 30 mm.

[0017] Preferably, in step S31, the high-resistance anti-corona layer I includes at least two high-resistance anti-corona segments; all the high-resistance anti-corona segments are arranged side by side along the length direction of the wire rod body, and are tightly wrapped around the outer surface of the stator wire rod; adjacent high-resistance anti-corona segments are transitionally overlapped at the head and tail, and a pressure equalizing ring is arranged on the outer side of the transition overlap structure.

[0018] Preferably, in step S31, different high-resistance anti-corona sections are made of fully-cured high-resistance anti-corona tapes with different properties, and starting from one end of the transition overlapping low-resistance anti-corona layer, the initial surface resistivity and nonlinear coefficient of the different high-resistance anti-corona sections increase successively.

[0019] Preferably, in step S31, the voltage equalizing ring is made of a low-resistance anti-corona tape.

[0020] Preferably, in step S31, the axial section of the high-resistance anti-corona section is in a "Z" shape, and the transition overlap width between adjacent high-resistance anti-corona sections is not less than 20 mm.

[0021] Preferably, in step S32, the isolation layer is made of mica tape.

[0022] Preferably, in step S2, the low-resistance anti-corona layer is made of a curable low-resistance anti-corona tape, and a low-resistance anti-corona paint is applied on its surface.

[0023] Beneficial technical effects brought by the present invention:

[0024] 1) The method disclosed in the technical solution for improving the end current carrying capacity of a stator wire bar structure by designing the structure thereof, by providing a low-resistance anti-corona layer and a high-resistance anti-corona unit, the end leakage current of the stator wire bar is guided to the stator core, thereby improving the overall end current carrying capacity of the stator wire bar structure.

[0025] 2) The high-resistance anti-corona unit in this technical solution adopts a double-layer anti-corona layer structure of high-resistance anti-corona layer I and high-resistance anti-corona layer II, which can be applied to two major insulation systems: low-resistance VPI and high-resistance molding. It is formed in one step, with simple process and no need for additional anti-corona treatment such as painting, which is of great significance to improving the production efficiency of stator wire rods.

[0026] 3) In this technical solution, under the premise of setting up a double-layer anti-corona layer structure of high-resistance anti-corona layer I and high-resistance anti-corona layer II, by setting up a voltage equalizing ring, an equipotential zone can be constructed between high-resistance anti-corona layer I and high-resistance anti-corona layer II, which can even out the current density of high-resistance anti-corona layer I and high-resistance anti-corona layer II, improve the current carrying capacity of the entire stator wire rod end, and reduce the risks of end corona, flashover and anti-corona layer ablation. At the same time, the voltage equalizing ring can improve the difference in the length of the anti-corona layer in the inner and outer axial radii of the bend at the end of the stator wire rod to a certain extent, improve the uniformity of the electric field distribution at the end of the stator wire rod, increase the flashover voltage and withstand voltage level of the stator wire rod, and improve the reliability of the stator wire rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is an axial cross-sectional view of a high-voltage motor stator bar anti-corona structure;

[0028] Figure 2 Schematic diagram of the flow direction of the end leakage current in the stator bar.

[0029] In the figure:

[0030] 1. Stator core; 2. Low-resistance anti-corona layer; 3. Isolation layer; 4. High-resistance anti-corona layer II; 5. High-resistance anti-corona section; 6. Grading ring; 7. Copper conductor; 8. Ground insulation layer. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0032] Therefore, the following detailed description of the invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the invention. Based on the embodiments of the invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the invention.

[0033] Example 1

[0034] This embodiment discloses a method for improving the current carrying capacity of the stator bar end by designing the stator bar structure. As a preferred embodiment of the present invention, according to Figure 1 The stator bar structure shown includes the following steps:

[0035] S1, preparing processing materials for the wire rod body, the stator core 1, the low-resistance anti-corona layer 2 and the high-resistance anti-corona unit;

[0036] S2, after the wire rod body is processed and before the stator core 1 is connected to the wire rod body, a low-resistance anti-corona layer 2 is processed on the wire rod body, so that the low-resistance anti-corona layer 2 is tightly wrapped around the outer surface of the wire rod body, and the low-resistance anti-corona layer 2 is between the stator core 1 and the wire rod body;

[0037] S3, processing a high-resistance anti-corona unit on the wire rod body, using the high-resistance anti-corona unit to guide the current transmitted axially along the wire rod body to the low-resistance anti-corona layer 2, and then leading the current into the stator core 1 through the low-resistance anti-corona layer 2; wherein the high-resistance anti-corona unit is arranged side by side with the low-resistance anti-corona layer 2 along the length direction of the wire rod body, and the inner surface of the head end of the high-resistance anti-corona unit transitionally overlaps the outer surface of the tail end of the low-resistance anti-corona layer 2.

[0038] Based on the structural design and processing of the above-mentioned stator wire bar structure, the principle of improving its end current carrying capacity is: after the current is introduced through the wire bar body, under the action of high voltage, the current will be transmitted along the axial and radial directions of the wire bar body. Radial transmission is when the stator wire bar is subjected to high voltage, the current flows directly to the stator core 1 through the wire bar body. Axial transmission is the end leakage current. In the present technical scheme, a high-resistance anti-corona unit is provided so that the end leakage current flows to the high-resistance anti-corona unit, and then flows to the stator core 1 through the low-resistance anti-corona layer 2. In this process, due to the low resistivity of the low-resistance anti-corona layer 2 and the high-resistance anti-corona unit, the end leakage current is mainly concentrated in the internal transmission of the two. In summary, the present technical scheme achieves an improvement in the end current carrying capacity of the stator wire bar structure.

[0039] Example 2

[0040] This embodiment discloses a method for improving the current carrying capacity of the end of a stator bar by designing its structure, as a preferred embodiment of the present invention, that is, based on Example 1, in step S2, the processed bar body includes a copper conductor 7 and a ground insulation layer 8, and the ground insulation layer 8 is tightly wrapped around the surface of the copper conductor 7. The ground insulation layer 8 is a basic insulation layer, which can be made of materials such as mica tape or epoxy resin.

[0041] Generally, after the current is introduced through the wire rod body, under the action of high voltage, the current will be transmitted along the axial and radial directions of the copper conductor 7. The radial transmission is when the stator wire rod is subjected to high voltage, the current inside the copper conductor 7 passes through the ground insulation layer 8 to the stator core 1. Figure 2 As shown, axial transmission (end leakage current, the arrow in the figure is the flow direction of the end leakage current) is that the current in the copper conductor 7 flows along the surface of the ground insulation layer 8 to the high-resistance anti-corona unit, and then flows to the stator core 1 through the low-resistance anti-corona layer 2.

[0042] Example 3

[0043] This embodiment discloses a method for improving the current carrying capacity of the end of a stator bar by designing the structure of the stator bar. As a preferred embodiment of the present invention, based on Embodiment 1 or 2, in step S3, processing a high-resistance anti-corona unit on the bar body includes the following steps:

[0044] S31, firstly process a high-resistance anti-corona layer I on the surface of the wire rod body, and the high-resistance anti-corona layer I is tightly wrapped on the outer surface of the wire rod body as the first flow path of the end leakage current;

[0045] S32, processing an isolation layer 3 on the surface of the high-resistance anti-corona layer I, wherein the isolation layer 3 is closely attached to the outer surface of the high-resistance anti-corona layer I for path isolation;

[0046] S33, processing a high-resistance anti-corona layer II 4 on the surface of the high-resistance anti-corona layer I and the isolation layer 3, the high-resistance anti-corona layer II 4 covers and wraps the outside of the high-resistance anti-corona layer I and the isolation layer 3, and serves as a second flow path for the end leakage current.

[0047] In the present technical solution, in order to reduce the leakage current density of the high-resistance anti-corona unit, a high-resistance anti-corona layer I and a high-resistance anti-corona layer II4 are set, and an isolation layer 3 is set between the high-resistance anti-corona layer I and the high-resistance anti-corona layer II4, so that the end leakage current can flow through two paths of the high-resistance anti-corona layer I and the high-resistance anti-corona layer II4.

[0048] In addition, this technical solution adopts a double-layer anti-corona layer structure of high-resistance anti-corona layer I and high-resistance anti-corona layer II 44, which can be applied to two major insulation systems: low-glue VPI and high-glue molding. It is formed in one time and the process is simple. There is no need for additional anti-corona treatment such as painting, which is of great significance to improving the production efficiency of stator wire rods.

[0049] Example 4

[0050] This embodiment discloses a method for improving the current carrying capacity of the end of a stator bar by designing its structure, as a preferred embodiment of the present invention, that is, based on Example 3, in step S3, the high-resistance anti-corona layer I and the high-resistance anti-corona layer II4 are respectively transitionally overlapped with the outer surface of the tail end of the low-resistance anti-corona layer 2, and the transition overlap width between the high-resistance anti-corona layer I and the low-resistance anti-corona layer 2 is not less than 20 mm, and the transition overlap width between the high-resistance anti-corona layer II4 and the low-resistance anti-corona layer 2 is not less than 30 mm. In this way, the connectivity between the low-resistance anti-corona layer 2 and the high-resistance anti-corona layer I, the low-resistance anti-corona layer 2 and the high-resistance anti-corona layer II4, and the low-resistance anti-corona layer 2 and the high-resistance anti-corona unit as a whole is ensured.

[0051] Example 5

[0052] This embodiment discloses a method for improving the current carrying capacity of the end of a stator wire rod by designing its structure, as a preferred embodiment of the present invention, that is, based on Example 3 or 4, considering that due to the difference in material properties and the influence of electric field strength, a simple double-layer high-resistance anti-corona layer structure cannot achieve uniform distribution of leakage current in two paths, and the current carrying capacity prompt effect is limited. Based on this, in step S31, the high-resistance anti-corona layer I includes at least two high-resistance anti-corona segments 5; all high-resistance anti-corona segments 5 are arranged side by side along the length direction of the wire rod body, and are tightly wrapped around the outer surface of the stator wire rod; adjacent high-resistance anti-corona segments 5 are transitionally overlapped at the head and tail, and an equalizing ring 6 is arranged on the outside of the transition overlap structure.

[0053] That is, this technical solution sets different numbers of equalizing rings 6 at the isolation layer 3 to connect the high-resistance anti-corona layer I and the high-resistance anti-corona layer II 4 to form a conductive channel. Its function is to construct an equipotential zone between the high-resistance anti-corona layer I and the high-resistance anti-corona layer II 4, so that the leakage current density tends to be uniform, and further improve the current carrying capacity of the entire stator bar end. In summary, this technical solution has the characteristics of facilitating the adjustment of field strength distribution and ensuring the anti-corona effect, specifically:

[0054] Different high-resistance anti-corona sections 5 can be made of fully cured high-resistance anti-corona tapes with different properties, so that starting from one end of the transitional overlap low-resistance anti-corona layer 2, the initial surface resistivity and nonlinear coefficient of different high-resistance anti-corona sections 5 increase in sequence. Figure 1 As shown, three high-resistance anti-corona sections 5 are provided, starting from one end of the transitional overlap low-resistance anti-corona layer 2, which are high-resistance anti-corona section I, high-resistance anti-corona section II and high-resistance anti-corona section III, respectively, and are made of three types of fully cured high-resistance anti-corona tapes. The high-resistance anti-corona tape is a semiconductor material with nonlinear characteristics, and its surface resistivity can be calculated according to the following formula:

[0055] ρ E =ρ0×e-βE ;

[0056] Where ρ0 is the initial surface resistivity; β is the nonlinear coefficient; E is the electric field strength during the test; ρ E is the surface resistivity when the electric field strength is E.

[0057] Therefore, when selecting the fully solidified high-resistance anti-corona tape for high-resistance anti-corona segment I, high-resistance anti-corona segment II and high-resistance anti-corona segment III, the initial surface resistivity of high-resistance anti-corona segment I is ρ 01 , the nonlinear coefficient is β1; let the initial surface resistivity of the high-resistance anti-corona section II be ρ 02 , the nonlinear coefficient is β2; let the initial surface resistivity of high-resistance anti-corona section III be ρ 03 , the nonlinear coefficient is β3, then:

[0058]

[0059] In this way, the field strength at the end can be reduced as much as possible to ensure the anti-corona effect.

[0060] Example 6

[0061] This embodiment discloses a method for improving the current carrying capacity of the end of a stator wire rod by designing its structure, as a preferred implementation scheme of the present invention, that is, based on Example 5, in its step S31, the voltage equalizing ring 6 is made of a low-resistance anti-corona tape. Specifically, it is made by wrapping the low-resistance anti-corona tape in a ring shape, and its function is to construct an equipotential zone between the high-resistance anti-corona layer I and the high-resistance anti-corona layer II4. The voltage equalizing ring 6 can even out the current density of the high-resistance anti-corona layer I and the high-resistance anti-corona layer II4, and improve the current carrying capacity of the entire stator wire rod end. At the same time, the voltage equalizing ring 6 can improve the difference in the axial length of the anti-corona layer of the inner and outer radii at the bend of the stator wire rod end to a certain extent, and improve the uniformity of the electric field distribution at the stator wire rod end.

[0062] Example 7

[0063] This embodiment discloses a method for improving the current carrying capacity of the end of a stator bar by designing its structure, as a preferred embodiment of the present invention, that is, based on Embodiment 5 or 6, in step S31, the axial section of the high-resistance anti-corona section 5 is in a "Z" shape, which is convenient for transitional overlap between adjacent high-resistance anti-corona sections 5, and between the high-resistance anti-corona layer I and the low-resistance anti-corona layer 2. At the same time, the high-resistance anti-corona section 5 of the structure has a stepped structure, which is convenient for the layout of the isolation layer 3 and the equalizing ring 6.

[0064] Furthermore, the transition overlap width between adjacent high-resistance anti-corona sections 5 is not less than 20 mm to ensure connectivity. Furthermore, the width (axial dimension) of the equalizing ring 6 is consistent with the transition overlap width between adjacent high-resistance anti-corona sections 5 to prevent local thickening.

[0065] Furthermore, the isolation layer 3 is made of mica tape, specifically, half-wrapped mica tape. According to the wire rod forming process, mica tape with less glue, medium glue, or more glue can be flexibly selected, or other similar insulating materials can be selected.

Claims

1. A method for improving the current carrying capacity of a stator bar end by designing the stator bar structure, characterized in that: The following steps are involved: S1, preparing processing materials for the wire rod body, the stator core (1), the low-resistance anti-corona layer (2) and the high-resistance anti-corona unit; S2, after the wire rod body is processed and before the stator core (1) is connected to the wire rod body, a low-resistance anti-corona layer (2) is processed on the wire rod body, so that the low-resistance anti-corona layer (2) is tightly fitted and wrapped around the outer surface of the wire rod body, and the low-resistance anti-corona layer (2) is located between the stator core (1) and the wire rod body; S3, processing a high-resistance anti-corona unit on the wire rod body, using the high-resistance anti-corona unit to guide the current transmitted along the axial direction of the wire rod body to the low-resistance anti-corona layer (2), and then guiding the current from the low-resistance anti-corona layer (2) into the stator core (1); wherein the high-resistance anti-corona unit is arranged side by side with the low-resistance anti-corona layer (2) along the length direction of the wire rod body, and the inner surface of the head end of the high-resistance anti-corona unit transitionally overlaps the outer surface of the tail end of the low-resistance anti-corona layer (2).

2. The method for improving the end current carrying capacity of a stator bar by designing its structure as claimed in claim 1, characterized in that: In the step S2, the processed wire rod body comprises a copper conductor (7) and a ground insulation layer (8), and the ground insulation layer (8) is tightly wrapped around the surface of the copper conductor (7).

3. The method for improving the end current carrying capacity of a stator bar by designing its structure as claimed in claim 1, characterized in that: In step S3, processing the high-resistance anti-corona unit on the wire rod body comprises the following steps: S31, firstly process a high-resistance anti-corona layer I on the surface of the wire rod body, and the high-resistance anti-corona layer I is tightly wrapped on the outer surface of the wire rod body as the first flow path of the end leakage current; S32, processing an isolation layer (3) on the surface of the high-resistance anti-corona layer I, wherein the isolation layer (3) is closely attached to the outer surface of the high-resistance anti-corona layer I for path isolation; S33, processing a high-resistance anti-corona layer II (4) on the surface of the high-resistance anti-corona layer I and the isolation layer (3), wherein the high-resistance anti-corona layer II (4) covers and wraps the outside of the high-resistance anti-corona layer I and the isolation layer (3) to serve as a second flow path for the end leakage current.

4. The method for improving the end current carrying capacity of a stator bar by designing its structure as claimed in claim 3, characterized in that: In the step S3, the high-resistance anti-corona layer I and the high-resistance anti-corona layer II (4) are respectively transitionally overlapped with the outer surface of the tail end of the low-resistance anti-corona layer (2), and the transitional overlap width between the high-resistance anti-corona layer I and the low-resistance anti-corona layer (2) is not less than 20 mm, and the transitional overlap width between the high-resistance anti-corona layer II (4) and the low-resistance anti-corona layer (2) is not less than 30 mm.

5. The method for improving the end current carrying capacity of a stator bar by designing its structure as claimed in claim 3, characterized in that: In the step S31, the high-resistance anti-corona layer I comprises at least two high-resistance anti-corona segments (5); all the high-resistance anti-corona segments (5) are arranged side by side along the length direction of the wire rod body, and are respectively tightly fitted and wrapped around the outer surface of the stator wire rod; adjacent high-resistance anti-corona segments (5) are transitionally overlapped at the head and tail, and a pressure equalizing ring (6) is arranged on the outer side of the transition overlap structure.

6. The method for improving the end current carrying capacity of a stator bar by designing its structure as claimed in claim 5, characterized in that: In the step S31, the different high-resistance anti-corona sections (5) are made of fully cured high-resistance anti-corona tapes with different properties, and starting from one end of the transition overlapping low-resistance anti-corona layer (2), the initial surface resistivity and nonlinear coefficient of the different high-resistance anti-corona sections (5) increase successively.

7. The method for improving the end current carrying capacity of a stator bar by designing its structure as claimed in claim 5, characterized in that: In the step S31, the voltage equalizing ring (6) is made of a low-resistance anti-corona tape.

8. The method for improving the end current carrying capacity of a stator bar by designing its structure as claimed in claim 5, characterized in that: In the step S31, the axial section of the high-resistance anti-corona section (5) is in a "Z" shape, and the transition overlap width between adjacent high-resistance anti-corona sections (5) is not less than 20 mm.

9. The method for improving the current carrying capacity of the stator bar end by designing the stator bar structure as claimed in claim 3, characterized in that: In the step S32, the isolation layer (3) is made of mica tape.

10. The method for improving the end current carrying capacity of a stator bar by designing its structure as claimed in claim 1, characterized in that: In the step S2, the low-resistance anti-corona layer (2) is made of a curable low-resistance anti-corona tape, and its surface is coated with a low-resistance anti-corona paint.

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