Preparation method of xlpe protective layer for reducing surface field intensity of igbt in high altitude area

Abstract

Disclosed are XLPE sheath for reducing the surface field intensity of IGBT in high altitude area and a preparation method thereof. In the method, a predetermined mass of LDPE raw material is weighed; the LDPE raw material and 2wt% of crosslinking agent DCP are added into a bottle, and the granules are placed into a mold padded with polyester film and sent into a flat vulcanizing machine to obtain a sheet-shaped LDPE sample; the sheet-shaped LDPE sample is vulcanized for 10 minutes to complete the crosslinking process; after cooling, the sheet-shaped LDPE sample is placed into a 70 DEG C constant-temperature oven for degassing for 24h to obtain a finished XLPE film; the finished XLPE film is cut and placed into an oven at 120 DEG C to complete softening, and is adhered to the weak insulation position of the IGBT; after cooling, the finished XLPE protective layer is obtained. The thickness of the XLPE film protective layer is quantitatively changed by regulating the mold size, and the coverage area of the XLPE protective layer on the outer surface of the IGBT is flexibly controlled.

Description

Technical Field

[0001] This invention belongs to the field of external insulation protection for power equipment, and in particular, it relates to an XLPE protective layer for reducing the electric field strength along the surface of IGBTs in high-altitude areas and its preparation method. Background Technology

[0002] High-altitude areas are characterized by low air density, low air pressure, low temperature, large diurnal temperature range, low humidity, and frequent thunderstorms. Reduced air density lowers the dielectric strength, making partial discharge more likely and resulting in insufficient insulation distance. Simultaneously, the high humidity at high altitudes can cause a decrease in the corona induction voltage of electrical equipment and wiring.

[0003] With the vigorous development of China's power construction, more and more projects are being built in high-altitude areas. The operation of AC / DC power transmission in high-altitude regions brings new challenges. The insulated gate bipolar transistor (IGBT), a key component of converter valves, inevitably experiences high-stress operating environments at high altitudes. Therefore, research on improving the reliability of its external insulation has attracted significant attention and in-depth study from the electrical industry. Cross-linked polyethylene (XLPE) possesses excellent dielectric properties and temperature stability, as well as strong plasticity, making it an ideal material for manufacturing external insulation protective layers.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes an XLPE protective layer for reducing the surface electric field strength of IGBTs in high-altitude areas and its preparation method. This method can reduce the electrical clearance and creepage distance of IGBTs. The sample preparation method can quantitatively change the thickness of the XLPE film protective layer by adjusting the mold size, and flexibly control the coverage area of ​​the XLPE protective layer on the outer surface of the IGBT. This significantly improves the weak external insulation area of ​​the IGBT and can be widely applied to various types of crimped IGBTs.

[0006] The objective of this invention is achieved through the following technical solution: a method for preparing an XLPE protective layer to reduce the surface electric field strength of IGBTs in high-altitude areas includes:

[0007] Step S1: Weigh a predetermined mass of granular low-density polyethylene (LDPE) raw material according to the density of the insulating granules and the volume of the mold used to prepare the XLPE protective layer;

[0008] Step S2: Add the LDPE raw material and 2% by mass of crosslinking agent dicumyl peroxide (DCP) to the bottle, heat at a constant temperature of 70°C, and shake the glass bottle every first time interval to form granules. Repeat this process multiple times until no particles adhere to the bottle wall.

[0009] Step S3: First open the steam bottom valve of No. 1 flat vulcanizing machine, then open the steam main valve to allow steam to circulate in the No. 1 flat vulcanizing machine for the second time period to drain the condensate in the No. 1 flat vulcanizing machine. Adjust the steam main valve and bottom valve, and preheat the mold at 180°C. The preheating time should not be less than the third time period.

[0010] Step S4: Place the granules into a mold lined with a polyester film, and send them into the No. 1 flat vulcanizing machine for preheating without pressure for the fourth time period. Then, hot press them at a constant temperature and pressure of 120°C and 10 MPa for the fifth time period to obtain sheet-like LDPE samples.

[0011] Step S5: Take out the mold and put it into the No. 2 flat vulcanizing machine. Under constant temperature and pressure of 180℃ and 15Mpa, the flat plate is closed and the sheet LDPE sample is vulcanized in the sixth time period to complete the crosslinking process.

[0012] Step S6: Remove the vulcanized sheet LDPE sample from the mold and place it in the No. 3 flat vulcanizing machine. Set the cooling method to circulating water cooling with a water flow rate of 2m. 3 / h, water temperature is 18℃, cooling time is the seventh time period;

[0013] Step S7: After cooling, place the sheet LDPE sample into a 70℃ constant temperature oven for the eighth degassing time period to obtain the finished XLPE film;

[0014] Step S8: Cut the finished XLPE film, place it in an oven at 120℃ to soften it, and then adhere it to the weak insulation position of the IGBT. After cooling, the finished XLPE protective layer is obtained.

[0015] In the method for preparing an XLPE protective layer to reduce the surface electric field strength of IGBTs in high-altitude areas, in step S1, the mold has a length of 10cm, a width of 10cm, and a thickness of 0.1cm, and the density of the LDPE used is 0.922 g / cm³. 3 .

[0016] In the method for preparing an XLPE protective layer to reduce the surface field strength of IGBTs in high-altitude areas, the first time period is 5 minutes, the second time period is 6 minutes, the third time period is 20 minutes, the fourth time period is 5 minutes, the fifth time period is 10 minutes, the sixth time period is 10 minutes, the seventh time period is 15 minutes, and the eighth time period is 24 hours.

[0017] In the method for preparing an XLPE protective layer to reduce the surface field strength of IGBTs in high-altitude areas, the weak point in insulation is the connection between the polyimide passivation layer of the IGBT and the ceramic shell.

[0018] In the method for preparing an XLPE protective layer to reduce the surface field strength of IGBTs in high-altitude areas, the characteristic feature is that the weak insulation location is the outer surface of the ceramic shell of the IGBT near the emitter.

[0019] In the method for preparing an XLPE protective layer to reduce the surface electric field of an IGBT in high-altitude areas, the weak point in insulation is the outer surface of the umbrella skirt structure outside the ceramic shell of the IGBT.

[0020] In the method for preparing an XLPE protective layer to reduce the surface field strength of IGBTs in high-altitude areas, the width of the outer surface of the umbrella skirt structure is 3.1 mm and the outer radius is 1.25 mm.

[0021] An XLPE protective layer for reducing the surface electric field strength of IGBTs in high-altitude areas is prepared according to the method described above.

[0022] The XLPE protective layer is shaped to fit the structure at weak points in the IGBT insulation.

[0023] In the XLPE protective layer, the electric field strength of the IGBT with the XLPE protective layer attached is not higher than 3.0462kV / mm.

[0024] Compared with the prior art, the present invention has the following advantages: The present invention quantitatively changes the thickness of the XLPE film protective layer by adjusting the mold size, and flexibly controls the coverage area of ​​the XLPE protective layer on the outer surface of the IGBT, which significantly improves the weak external insulation interface of the IGBT and can be widely used on various types of crimped IGBTs, thus better coping with the harsh working conditions in high-altitude areas. Attached Figure Description

[0025] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0026] In the attached diagram:

[0027] Figure 1 This is a schematic diagram of the XLPE protective layer manufacturing process of the present invention;

[0028] The area within the dashed box illustrates the fabrication process of a single-layer XLPE film, while the remaining portion shows a cross-sectional schematic of a 4500V / 3000A IGBT without the film attached.

[0029] Figure 1 shows the collector of the IGBT, approximately 1 mm thick and 158 mm in diameter; its conductivity is 5.998 × 10⁻⁶. 7 [S / m]; Constant pressure heat capacity is 385 [J / (kg*K)]; Relative permittivity is 1; Density is 8960 [kg / m³] 3 The thermal conductivity is 400 [W / (m*K)].

[0030] Figure 2 shows the copper base of the IGBT, approximately 1.5mm thick and 204mm in diameter; its conductivity is 5.998*10⁻⁶. 7 [S / m]; Constant pressure heat capacity is 385 [J / (kg*K)]; Relative permittivity is 1; Density is 8960 [kg / m³] 3 The thermal conductivity is 400 [W / (m*K)].

[0031] Figure 3 shows the PEEK plastic outer frame of the IGBT, approximately 28.5 mm high and 184 mm in diameter; its conductivity is 2*10⁻⁶. -15 [S / m]; Constant pressure heat capacity is 1700 [J / (kg*K)]; Relative permittivity is 3.5; Density is 1350 [kg / m³] 3 The thermal conductivity is 0.3 [W / (m*K)].

[0032] Figure 4 shows the ceramic skirts of the IGBT, with a height of approximately 26.4 mm, a minimum diameter of approximately 184 mm, a maximum diameter of approximately 195.15 mm, and a total of four skirts. The outer spherical radius of the skirts is 1.15 mm; the conductivity is 5*10⁻⁶. -15 [S / m]; Constant pressure heat capacity is 1250 [J / (kg*K)]; Relative permittivity is 8; Density is 3500 [kg / m³] 3 The thermal conductivity is 1 [W / (m*K)].

[0033] Figure 5 shows the polyimide passivation layer of the IGBT, approximately 1.4 mm thick and 178 mm in diameter; its conductivity is 1*10⁻⁶. -14 [S / m]; Constant pressure heat capacity is 1100 [J / (kg*K)]; Relative permittivity is 3.9; Density is 1300 [kg / m³] 3 The thermal conductivity is 0.15 [W / (m*K)].

[0034] Figure 6 shows the emitter of the IGBT, approximately 1 mm thick and 158 mm in diameter; its conductivity is 5.998 × 10⁻⁶. 7 [S / m]; Constant pressure heat capacity is 385 [J / (kg*K)]; Relative permittivity is 1; Density is 8960 [kg / m³] 3 The thermal conductivity is 400 [W / (m*K)].

[0035] Figure 7 shows the gate of the IGBT, with a radius of approximately 1.47 mm and a diameter of approximately 158 mm; its conductivity is 5.998 × 10⁻⁶. 7 [S / m]; Constant pressure heat capacity is 385 [J / (kg*K)]; Relative permittivity is 1; Density is 8960 [kg / m³] 3 The thermal conductivity is 400 [W / (m*K)].

[0036] The specific structure and dimensions of the weak insulation parts of the IGBT are as follows: a) is the connection between the polyimide passivation layer and the ceramic shell, with a width of approximately 2.3 mm; b) is the outer surface of the ceramic shell near the emitter, with a height of approximately 6 mm; c) is the outer surface of the umbrella skirt structure outside the ceramic shell, with a width of approximately 3.1 mm and an outer radius of 1.25 mm.

[0037] Figure 2 This is a schematic diagram of the external electric field distribution of the IGBT without the XLPE protective layer, as well as a magnified view of a weak part of the insulation.

[0038] Figure 3 This is a schematic diagram of the external electric field distribution of the IGBT after the XLPE protective layer is added according to the present invention, as well as a partial enlarged view of the weak insulation part;

[0039] Figure 4 This is a schematic diagram of the creepage path on the left side of the IGBT. Creepage distance refers to the shortest approximate distance between two conductors along their insulating surfaces. In this model, the creepage distance is represented as the shortest distance along the outer surface of the IGBT connecting the collector and emitter.

[0040] Figure 5 This is a schematic diagram of the tangential electric field components showing the electric field distortion along the creepage path without the XLPE protective layer installed.

[0041] Figure 6 This is a schematic diagram of the tangential electric field components showing the electric field distortion along the creepage path after the XLPE protective layer is installed.

[0042] Figure 7 This is a schematic diagram of a flat vulcanizing machine used in the preparation of the XLPE protective layer.

[0043] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0044] The following will refer to the appendix. Figures 1 to 7 Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0045] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0046] To facilitate understanding of the embodiments of the present invention, the specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings, taking the 4500V / 3000A IGBT (specific model: TG3000SW45ZC-P200) of CRRC Group as an example. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0047] In one embodiment, such as Figures 1 to 6 As shown, a method for preparing an XLPE protective layer to reduce the electric field strength along the surface of an IGBT in high-altitude areas includes:

[0048] Step S1: Calculate and weigh 10.142g of LDPE raw material (granular solid of grade 2220HSC produced by Yangzi Petrochemical-BASF Petrochemical Company) based on the density of insulating granules and the volume of the mold using an electronic balance. Step S2: Add LDPE base material and 2wt% crosslinking agent DCP to a glass bottle, heat at a constant temperature of 70℃, remove and shake the glass bottle every 5 minutes, repeat several times until no particles adhere to the bottle wall. Step S3: First open the steam bottom valve, then open the steam main valve, and let the steam circulate in the flat vulcanizing machine for 6 minutes to drain the condensate in the vulcanizing machine. Adjust the main steam valve and bottom valve, preheat the mold to 180℃ for at least 20 minutes; Step S4: Place the granules into a stainless steel mold lined with polyester film, and preheat it in the No. 1 flat vulcanizing machine for 5 minutes without pressure, then hot-press it for 10 minutes at a constant temperature and pressure of 120℃ and 10MPa to obtain a sheet-like LDPE sample; Step S5: Remove the mold and place it in the No. 2 flat vulcanizing machine, pressurize and close the plate at a constant temperature and pressure of 180℃ and 15MPa, and vulcanize for 10 minutes to complete the crosslinking process; Step S6: Unload the pump station, immediately remove the vulcanized sample from the mold, and place it in the No. 3 flat vulcanizing machine. Set the cooling method to circulating water cooling with a water flow rate of 2m. 3 / h, water temperature is 18℃, cooling time is 15 minutes; Step S7: After cooling, the sample is placed in a 70℃ constant temperature oven for degassing for 24 hours to obtain the finished XLPE film; Step S8: The finished film is cut into appropriate widths, placed in a 120℃ oven to soften, and adhered to the weak insulation locations of the IGBT: (a) the connection between the polyimide passivation layer and the ceramic shell, with a width of about 2.3 mm; (b) the outer surface of the ceramic shell near the emitter, with a height of about 6 mm; (c) the outer surface of the umbrella skirt structure outside the ceramic shell, with a width of about 3.1 mm and an outer radius of 1.25 mm. After cooling, the finished XLPE protective layer is obtained; It is worth noting that without the XLPE protective layer, the maximum electric field strength on the entire IGBT surface is 4.3207 kV / mm; after the XLPE protective layer is added, the maximum electric field strength on the entire IGBT surface is reduced to 3.0462 kV / mm, a reduction of 29.49%. Furthermore, the overall field strength distortion along the creepage path decreases, greatly reducing the probability of surface flashover in the IGBT casing.

[0049] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for preparing an XLPE protective layer to reduce the surface electric field strength of IGBTs in high-altitude areas, characterized in that, It includes the following steps: Step S1: Weigh the predetermined mass of LDPE raw material according to the density of the insulating granules and the volume of the mold used to prepare the XLPE protective layer; Step S2: Add the LDPE raw material and 2wt% crosslinking agent DCP to the bottle, heat at a constant temperature of 70°C, and shake the glass bottle every first time interval to form granules. Repeat this process multiple times until no particles adhere to the bottle wall. Step S3: First open the steam bottom valve of No. 1 flat vulcanizing machine, then open the steam main valve to allow steam to circulate in the No. 1 flat vulcanizing machine for the second time period to drain the condensate in the No. 1 flat vulcanizing machine. Adjust the steam main valve and bottom valve, and preheat the mold at 180°C. The preheating time should not be less than the third time period. Step S4: Place the granules into a mold lined with a polyester film, send it into a flat vulcanizing machine for preheating without pressure for the fourth time period, and hot press it at a constant temperature and pressure of 120℃ and 10MPa for the fifth time period to obtain a sheet-like LDPE sample. Step S5: Take out the mold and put it into the No. 2 flat vulcanizing machine. Under constant temperature and pressure of 180℃ and 15Mpa, the flat plate is closed and the sheet LDPE sample is vulcanized in the sixth time period to complete the crosslinking process. Step S6: Remove the vulcanized sheet LDPE sample from the mold and place it in the No. 3 flat vulcanizing machine. Set the cooling method to circulating water cooling with a water flow rate of 2m. 3 / h, water temperature is 18℃, cooling time is the seventh time period; Step S7: After cooling, place the sheet LDPE sample into a 70℃ constant temperature oven for the eighth degassing time period to obtain the finished XLPE film; Step S8: Cut the finished XLPE film, place it in an oven at 120℃ to soften it, and then adhere it to the weak insulation position of the IGBT. After cooling, the finished XLPE protective layer is obtained. In step S8, the weak insulation locations are the connection between the polyimide passivation layer of the IGBT and the ceramic shell, the outer surface of the ceramic shell of the IGBT near the emitter, or the outer surface of the umbrella skirt structure outside the ceramic shell of the IGBT.

2. The method for preparing an XLPE protective layer to reduce the surface electric field strength of IGBTs in high-altitude areas according to claim 1, characterized in that, In step S1, the mold has a length of 10cm, a width of 10cm, a thickness of 0.1cm, and the density of the LDPE used is 0.922g / cm3.

3. The method for preparing an XLPE protective layer to reduce the surface electric field strength of IGBTs in high-altitude areas according to claim 1, characterized in that, The first time period is 5 minutes, the second time period is 6 minutes, the third time period is 20 minutes, the fourth time period is 5 minutes, the fifth time period is 10 minutes, the sixth time period is 10 minutes, the seventh time period is 15 minutes, and the eighth time period is 24 hours.

4. The method for preparing an XLPE protective layer to reduce the surface electric field strength of IGBTs in high-altitude areas according to claim 1, characterized in that, The width of the outer surface of the umbrella skirt structure is 3.1 mm, and the outer radius is 1.25 mm.

5. An IGBT with an XLPE protective layer that reduces the surface electric field strength of the IGBT in high-altitude areas, characterized in that, The XLPE protective layer is prepared according to any one of claims 1-4 using a method for preparing an XLPE protective layer to reduce the surface field strength of IGBTs in high-altitude areas.

6. The IGBT according to claim 5, characterized in that, The shape of the XLPE protective layer is adapted to the structure at weak points in the IGBT insulation.

7. The IGBT according to claim 5, characterized in that, The electric field strength of the IGBT with the XLPE protective layer attached is not higher than 3.0462 kV / mm.

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