Metalized polypropylene film capacitor electrode loss numerical simulation method
By building a self-healing breakdown experimental platform and building a geometric model, the problems of low physical field calculation accuracy and high computing resource consumption in the electrode loss area of metallized polypropylene film capacitors in the prior art are solved, and high-precision electric field distribution simulation and resource conservation are achieved.
Patent Information
- Application Number
- CN202411717650.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-12-13
- Filing Date
- 2024-11-27
- Publication Date
- 2025-04-01
AI Technical Summary
In the prior art, when calculating the physical field of the electrode loss region of the metallized polypropylene film capacitor, there are problems such as low accuracy and excessive computing resource consumption.
By building a self-healing breakdown experimental platform, a capacitor with a single self-healing breakdown was obtained, and a geometric model was constructed after disassembly, the electrode loss morphology was portrayed, and the electrode electric field distribution cloud map was obtained.
High-precision electric field distribution simulation of the electrode loss area of metallized polypropylene film capacitor is realized, reducing the consumption of computing resources and saving costs.
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Figure CN119740276A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a numerical simulation method for electrode loss of a metallized polypropylene film capacitor, belonging to the technical field of capacitors. Background Art
[0002] Metallized film capacitors based on polypropylene (PP) are widely used in power electronics, new energy vehicles, medical equipment, aerospace, flexible DC transmission and other fields due to their high breakdown strength, low dielectric loss, high DC resistivity and excellent self-healing ability. Under the action of the DC electric field, the self-healing breakdown inside the MPPFC causes permanent loss of the metal electrode, resulting in a decrease in the capacitance and an increase in the dielectric loss of the MPPFC, thereby reducing its electrical performance and operational reliability. At present, the physical field of the electrode loss area is mainly obtained through actual measurement or numerical simulation. Among them, the actual measurement method has the following disadvantages: 1) high cost; 2) only a very limited number of observation points can be observed. The distribution characteristics of the physical field; 3) the physical field distribution test during operation is difficult to achieve; numerical simulation can circumvent the above problems, but due to the thin electrode structure inside the capacitor, there is a huge difference between this size and the overall size. Therefore, it is difficult to directly construct a finite element mesh for the geometric model using the numerical simulation method, so it requires huge computing resources, and sometimes even makes the calculation impossible.
[0003] In view of this, it is necessary to propose the present invention. Summary of the invention
[0004] The invention provides a numerical simulation method for electrode loss of a metallized polypropylene film capacitor, so as to solve the defects of low precision and excessive consumption of computing resources in the existing physical field calculation method of capacitor electrode loss area.
[0005] The technical solution of the present invention is:
[0006] A numerical simulation method for electrode loss of a metallized polypropylene film capacitor, comprising:
[0007] Build a self-healing breakdown test platform for metallized polypropylene film capacitors, and obtain metallized polypropylene film capacitors that have undergone a single self-healing breakdown through a voltage-boosting experiment;
[0008] Disassemble the metallized polypropylene film capacitor that has undergone a single self-healing breakdown and obtain a micrograph of the electrode loss morphology;
[0009] A geometric model of metallized polypropylene film was constructed; based on the electrode loss morphology micrograph, the electrode loss morphology was depicted on the metal electrode of the geometric model.
[0010] Set initial and boundary conditions;
[0011] Set the material property parameters; mesh the geometric model before and after self-healing breakdown;
[0012] Finite element calculation was performed on the geometric model to obtain the electrode electric field distribution cloud map before and after self-healing breakdown.
[0013] Furthermore, according to the electrical signal waveform of the metallized polypropylene film capacitor during a single self-healing breakdown, the sampling current rising curve is fitted to obtain a fitting equation of the sampling current rising curve; the fitting equation is used as a fitting current source on one side of the gold-sprayed end of the metallized polypropylene film.
[0014] Furthermore, the method of obtaining a metallized polypropylene film capacitor that undergoes a single self-healing breakdown through a voltage boosting experiment is specifically as follows: a self-healing breakdown experiment of an MPPFC is performed at room temperature, the experimental sample is voltage-boosted to 2000V at a rate of 25V / s, and an MPPFC sample that only exhibits a single self-healing breakdown phenomenon is selected; or when the experimental sample is voltage-boosted to 2000V at a rate of 25V / s at room temperature, when a single self-healing breakdown phenomenon occurs, a DC power supply is turned off to obtain an MPPFC sample that undergoes a single self-healing breakdown.
[0015] Furthermore, the metallized polypropylene film capacitors that underwent a single self-healing breakdown were disassembled, and images of the electrodes of each MPPFC sample that underwent a single self-healing breakdown were collected using an optical microscope to obtain a micrograph of the electrode loss morphology.
[0016] Furthermore, the geometric model of the metallized polypropylene film is constructed by: constructing a geometric model of a preset number of metallized polypropylene film layers, performing dimensionality reduction processing on the metal electrodes in the geometric model, setting the surface of the polypropylene film as an electrical shield and setting a part of it as a metal electrode, and setting the remaining part as an edge-retaining air gap.
[0017] Furthermore, the setting of initial conditions and boundary conditions includes: 1) the initial current of the entire geometric model is 0; 2) an electric shield is set on the polypropylene surface to represent an aluminum electrode with a thickness of 20 nanometers and a width of 23 millimeters and a 2 millimeter margin air gap; 3) a fitting current source is applied on one side of the gold-sprayed end, and the other side of the gold-sprayed end is grounded.
[0018] The meshing of the geometric model after self-healing breakdown is performed: the boundary of the electrode loss area is divided by custom meshing, the mesh in the electrode loss area is encrypted, the remaining electrodes and the edge air gap are adaptively meshed using free triangles, and finally the sweep command is used to realize the meshing of the three-dimensional entity.
[0019] The beneficial effects of the present invention are:
[0020] Compared with the existing method of obtaining the physical field between metallized polypropylene films with a two-dimensional axisymmetric structure, the method of the present invention takes into account the complete size structure of the metallized polypropylene film, can obtain the electric field distribution cloud map of the electrode loss area according to the electrode loss morphology micrograph, and has the advantage of higher precision; compared with the existing method of using a full-size model for finite element calculation, the present invention performs dimensionality reduction processing on the metal electrodes in the geometric model, and the method has the advantages of less consumption of computing resources and high computing efficiency; compared with the method of obtaining the physical field distribution by measuring the inside of the capacitor element, the method of the present invention has the advantages of saving costs and being able to obtain the physical field of the entire region. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 It is a flow chart of the present invention;
[0022] Figure 2 It is the self-healing breakdown test circuit diagram;
[0023] Figure 3 It is the structure and geometric model diagram of the metallized film capacitor element; Figure 3 (a) is the metallized film capacitor element structure, Figure 3 (b) is the geometric model;
[0024] Figure 4 This is a single self-healing breakdown voltage and current waveform;
[0025] Figure 5 5(a) is the sampling current rising curve and the schematic diagram of electrode loss; 5(b) is the sampling current rising curve and the schematic diagram of electrode loss;
[0026] Figure 6 is the sampling current fitting curve;
[0027] Figure 7 It is the local meshing and meshing quality cloud map;
[0028] Figure 8 Field intensity, current density and power density distribution diagrams on the electrodes; Figure 8 (a) is the field strength distribution diagram, Figure 8 (b) is the current density distribution diagram, Figure 8 (c) is the power density distribution diagram;
[0029] Fig. 9 This is a micrograph of the morphology near the self-healing point of the metallized polypropylene film; Fig. 9 (a) is the morphology near the self-healing point of the metallized PP film. Fig. 9 (b) is a schematic diagram of self-healing breakdown;
[0030] Fig.10 is the axial distance and tangential distance in the statistical image number;
[0031] Fig.11 is a graph of the relationship between self-healing energy and self-healing voltage;
[0032] Fig.12 is the loss area of polypropylene film and aluminum electrode with different breakdown layers. DETAILED DESCRIPTION
[0033] The invention will be further described below in conjunction with the accompanying drawings and embodiments, but the content of the invention is not limited to the scope of the embodiments.
[0034] Example 1: Figure 1-Figure 12 As shown, a numerical simulation method for electrode loss of a metallized polypropylene film capacitor includes:
[0035] Step 1, building a metallized polypropylene film capacitor self-healing breakdown experimental platform, and obtaining a metallized polypropylene film capacitor that has a single self-healing breakdown through a voltage boosting experiment; further, the metallized polypropylene film capacitor that has a single self-healing breakdown through the voltage boosting experiment is specifically: performing an MPPFC self-healing breakdown experiment at room temperature, boosting the experimental sample to 2000V at a rate of 25V / s, and selecting the MPPFC sample that only has a single self-healing breakdown phenomenon, or in the process of boosting the experimental sample to 2000V at a rate of 25V / s at room temperature, when a single self-healing breakdown phenomenon occurs, turning off the DC power supply to obtain the MPPFC sample with a single self-healing breakdown.
[0036] Step 2, dismantling the metallized polypropylene film capacitor that has undergone a single self-healing breakdown to obtain a micrograph of the electrode loss morphology; further, performing a single self-healing breakdown experiment on the metallized polypropylene film capacitor to obtain a metallized polypropylene film capacitor that has undergone a single self-healing breakdown, dismantling the capacitor to obtain the metallized polypropylene film at the self-healing point, and using an optical microscope (OM, model M165C) to collect images of the electrodes of each MPPFC sample that has undergone a single self-healing breakdown;
[0037] Step 3, construct a geometric model of 4-layer metallized polypropylene film, perform dimensionality reduction processing on the metal electrodes in the geometric model, set the surface of the polypropylene film as an electrical shield and set a part of it as a metal electrode, and the remaining part as an edge air gap, and characterize the electrode loss morphology on the metal electrode of the geometric model according to the electrode loss morphology micrograph in step 2.
[0038] Step 4, set initial conditions and boundary conditions; 1) the initial current of the entire geometric model is 0; 2) the electrical shielding is set on the polypropylene surface to represent the aluminum electrode with a thickness of 20 nanometers and a width of 23 mm and a 2 mm margin air gap; 3) a fitting current source ( Figure 6), the other side of the gold-sprayed end is grounded.
[0039] A fitting current source is applied to one side of the gold-spraying end, and the electric field control equations involved include charge conservation (1), Ohm's law (2) and electric field calculation (3).
[0040]
[0041] Specifically, in an embodiment of the present invention, the thickness of each layer of the polypropylene film is set to 5 μm and the width is 25 mm; the metal electrode is subjected to dimensionality reduction processing to simplify it into a two-dimensional surface and an electrical shielding is set to represent a metal electrode with a width of 23 mm and a 2 mm margin air gap, and the surface thickness is set to 20 nm.
[0042] Step 5, set the material property parameters, as shown in Table 1; mesh the geometric model after self-healing breakdown. In order to improve the calculation efficiency, the boundary of the electrode loss area is divided into custom meshes, the mesh is encrypted in the electrode loss area, and the remaining electrodes and the air gap are adaptively meshed using free triangles. Finally, the sweep command is used to realize the meshing of the three-dimensional entity. The local details of the model mesh are divided as follows Figure 7 As shown. In order to ensure the accuracy of the results, the boundary of the electrode loss area is customized for meshing, and the maximum unit size is set to 0.005mm, the minimum unit size is 0.001mm, the maximum unit growth rate is 1.3, and the curvature factor is 0.2. The grid of the electrode loss area is encrypted, and the remaining electrodes and the air gaps are divided by adaptive meshing. Finally, the three-dimensional entity is meshed by the sweep command. The complete mesh of the geometric model contains 5515200 domain units.
[0043] Table 1 MPPFC material parameters
[0044] Material Relative dielectric constant Conductivity / (S / m) Polypropylene film 2.2 <![CDATA[5.5×10 -13 ]]> Gold-sprayed end-zinc 1 <![CDATA[2.94×10 7 ]]> Metal Electrode-Aluminum 1 <![CDATA[3.77×10 7 ]]> Air 1 <![CDATA[1×10 -17 ]]>
[0045] Step 6, perform finite element calculation on the geometric model to obtain the electrode electric field distribution cloud map before and after self-healing breakdown.
[0046] In this embodiment, according to Figure 3 The geometric model shown is Figure 5 The electrode loss morphology micrograph shown depicts the electrode loss morphology. At the same time, in the sampling current rising stage, the material properties are defined by using a piecewise function, so that the electrode loss area increases three times in the process of the sampling current rising from zero value to the peak value.
[0047] Proceed as Figure 7 The grid division is shown in the figure; the electrode surface field strength, current density and power density distribution cloud diagrams are obtained in the two states of electrode loss and electrode loss as shown in the figure Figure 8As shown (for the convenience of analysis, the electric field strength in the rising and falling stages of the sampling current is unified to 1.2×10 4 V / m. Similarly, the current density and power density are unified as 1.4×10 4 A / m 2 , 4.5×10 7 W / m 3 The color changes in the figure represent different levels of electric field intensity, current density and power density, from red (high electric field intensity, current density and power density) to blue (low electric field intensity, current density and power density).
[0048] In the time period of 0-12.76μs, according to the test boost speed, for a 1μF capacitor, it can be considered that the capacitor is fully charged instantly. Therefore, when the capacitor does not undergo self-healing breakdown, the capacitor is basically in a fully charged state, the entire metal electrode is in an equipotential state, and the electric field strength, current density and power density on the metallized electrode are zero. From 12.76μs onwards, the sampling current is greater than zero and increases rapidly. From the distribution cloud map of the electric field strength, current density and power density at 15μs, it can be seen that the distribution of the electric field strength, current density and power density begins to change. The red highlighted area in the cloud map corresponds to the enhancement of the local electric field, indicating that the metallized electrode inside the MPPFC is being lost; the highlighted area in the 18μs and 22μs cloud maps further expands, and the electrode damage area further expands; the highlighted area in the 22-200μs cloud map gradually decreases, indicating that the MPPFC is in an insulation recovery state, until the electric field strength, current density and power density on the MPPFC drop to 0 at 200μs. That is, after 200μs, the MPPFC has restored the insulation state, the self-healing point has been isolated, and its current has returned to zero.
[0049] The electric field inside the capacitor is mainly perpendicular to the axial direction. When the electrode is damaged, the electrical gap is prone to charge accumulation. These charges make the electric field at the upper and lower edges of the electrode loss gap increase more than the left and right edges. Therefore, during the self-healing breakdown process, the axial electric field intensity, current density and power density of the metal electrode loss area are higher than the tangential direction. And during the self-healing breakdown of MPPFC, when the Joule heat caused by the current density or power density on the electrode exceeds the energy required for self-healing, some heat may accumulate inside the capacitor, causing the dielectric film to melt, which may cause a short circuit between the electrodes.
[0050] Embodiment 2: In conjunction with the accompanying drawings, the optional specific implementation of the present invention is described as follows:
[0051] In order to better understand the self-healing breakdown characteristics of MPPFC under DC voltage, a self-healing breakdown experiment was conducted at room temperature. To ensure the reliability of the test, MPPFC from the same manufacturer, with the same manufacturing process and test process, was used as a sample to reduce the impact of measurement errors. The MPPFC used is composed of two layers of metallized PP film. The edge distance of the polypropylene film is 2mm, the width is 25mm, and the thickness is 5μm. The metallized electrode is made of aluminum, and the square resistance is less than 5Ω / m 2 The MPPFC capacitance is 1.0μF±5% and the rated voltage is 250V. The experimental sample is boosted to 2000V at a rate of 25V / s. When a single self-healing breakdown occurs during the boosting process, the DC power supply is turned off to obtain an MPPFC sample with a single self-healing breakdown.
[0052] The self-healing breakdown test circuit of MPPFC is as follows Figure 2 As shown in the figure, the DC power supply is a programmable high-power DC power supply (ITECH, IT6000D) with an adjustable voltage range of 0-2250V, and R1 is a current-limiting resistor with a resistance value of 10KΩ, which is used to protect the charging circuit channel; C x is the MPPFC test sample with a capacitance of 1μF; C m The voltage regulator capacitor is 3.3μF; the sampling resistor R2 is 50Ω, which is used to measure the current passing through the MPPFC; an oscilloscope recorder (Zhiyuan Electronics, ZDL6000) is used to record the voltage across the MPPFC and the current flowing through the sampling resistor, with a sampling rate of 100MS / s.
[0053] The experimental results and analysis are as follows:
[0054] 1. MPPFC self-healing voltage and current signals
[0055] The voltage and current waveform data of MPPFC single self-healing breakdown are obtained by oscilloscope (such as Figure 4 As shown in the figure). In the figure, U0 and U1 are respectively the C x The voltage across the two ends, where U0 is the actual corresponding working voltage, and the difference ΔU between U0 and U1 is the voltage drop of a single self-healing breakdown. The energy consumed in the self-healing process will cause the capacitor C x The voltage on the upper part of the self-healing device changes significantly, and the duration of the self-healing current is generally tens of microseconds to hundreds of microseconds.
[0056] 2. Surface morphology of metallized PP film
[0057] In the simulation analysis, it was found that after the self-healing breakdown of the metallized PP film, the electric field tended to accumulate at the upper / lower edges of the electrode loss area, resulting in higher current density and power density in this area than in other areas. It was then inferred that the axial electrode loss was higher than the tangential loss during a single self-healing breakdown of the MPPFC. Based on this, the MPPFC with a single self-healing breakdown was disassembled, and the surface micromorphology of the self-healing breakdown point of the metallized PP film (including the aluminum electrode layer and the polypropylene film layer) and its adjacent layers were observed and analyzed in detail.
[0058] An optical microscope (OM, model M165C) was used to collect images around the self-healing point of the highly metallized PP film of each MPPFC sample where a single self-healing breakdown occurred. Fig. 9 This is a microscopic image of the surface morphology around the self-healing point of the metallized PP film. Fig. 9 (a) The micrograph numbers and Fig. 9 (b) The position numbers of each layer in the self-healing breakdown diagram correspond to each other. It can be seen from the figure that the main self-healing breakdown hole is located on the fifth and sixth surfaces of the high-voltage electrode metallized PP film, and the area of the self-healing hole is 0.275mm 2 The high-voltage electrode loss area caused by self-healing breakdown is 15.34mm 2 The self-healing breakdown holes are located on the third and fourth surfaces of the ground electrode metallized PP film. The area of the self-healing holes is 0.017 mm 2 The self-healing breakdown caused the ground electrode loss area to be 2.298mm 2 On the seventh and eighth surfaces of the metallized PP film, the ground electrode layer loss area is 6.727 mm 2 And there is no breakdown hole in the low-voltage PP layer. The loss area of the high-voltage electrode in a single self-healing breakdown (15.34mm 2 ) is larger than the ground electrode loss area (9.025mm 2 ).
[0059] The significant difference between the self-healing behavior of MPPFC and single-layer metallized PP film is that the self-healing breakdown phenomenon on the surface of single-layer metallized PP film mainly develops from the breakdown point to the surface; while the self-healing breakdown behavior of MPPFC is not a perfect destruction of the single-layer metallized PP film, the self-healing breakdown develops from the surface to the radial direction, and may even cause penetrating damage to the multi-layer metallized film. Fig. 9 (a) It can be seen that after the capacitor undergoes self-healing breakdown, the damage areas of the aluminum electrode layer and the polypropylene film layer in the single-layer metallized PP film are not symmetrical. This may be because when the metallized PP film is located in the adjacent layer of the self-healing hole, the arc may only slightly corrode the aluminum electrode or the polypropylene surface without causing a complete breakdown.
[0060] During the self-healing process of MPPFC, the aluminum electrode layer evaporates and diffuses outward due to heat. The aluminum vapor is easily ionized to form a plasma discharge arc, and metal electrodes of different polarities will cause large differences in the self-healing area and morphology. By comparing the difference in loss shape between the ground electrode layer on the third surface and the high-voltage electrode layer on the fifth surface, it is found that the high-voltage electrode loss area is relatively regular, while the edge of the ground electrode loss area is relatively irregular.
[0061] It is worth noting that the damage of the metallized PP film along the axial direction is higher than that in the tangential direction, which is consistent with the conclusion found in the simulation that the electric field accumulates at the upper / lower edges of the electrode loss area, which in turn produces higher current density and power density in these areas, resulting in the electrode loss developing along the axial direction. By statistically analyzing the axial and tangential distances of 80 randomly selected electrode loss micrographs, the data show that in the vast majority of electrode loss micrographs, the average axial electrode loss (3.01mm) is higher than the average tangential electrode loss (2.44mm) ( Fig.10 ).
[0062] 3. MPPFC self-healing voltage and self-healing energy
[0063] Calculate the energy W released by MPPFC self-healing SH When , since the capacitance loss of MPPFC before and after a single self-healing breakdown is small, the capacitance loss of a single self-healing breakdown can be ignored, so W SH The expression is:
[0064]
[0065] In the formula, U0 is the voltage at the start of self-healing; U1 is the voltage at the end of self-healing. In addition, the energy released by the self-healing of a single-layer metallized PP film W SH It can be expressed as:
[0066]
[0067] In the formula, C s is the capacitance of metallized PP film; U BD is the self-healing voltage; R is the square resistance of the aluminum electrode; a(p) is the functional relationship between the self-healing energy and the interlayer pressure; a1 and a2 are the power coefficients of the self-healing voltage and the square resistance of the aluminum electrode, respectively. For the aluminum electrode with R < 10Ω / sq, a1 = 4.7, a2 = 1.8. Given that the constants of the single-layer metallized PP film are only related to the physical properties of the film itself, the self-healing energy W SH Can be simplified to:
[0068]
[0069] Where k is the inherent constant of MPPFC, which is determined by its own physical properties; α is the correlation coefficient between self-healing energy and self-healing voltage. Fig.11The correlation between the self-healing energy and the self-healing voltage is approximately fitted using the formula, and the correlation coefficient α is obtained as 2.10-2.54.
[0070] For the MPPFC (square resistance <5Ω / m 2 ), when the external applied voltage is lower than 500V, no self-healing behavior occurs; when the external applied voltage is higher than 500V, the self-healing voltage of MPPFC is in the range of 500V to 1375V, and its self-healing energy is between 10mJ and 350mJ, and its self-healing energy increases with the increase of self-healing voltage.
[0071] 4. Number of self-healing breakdown layers and loss area of MPPFC
[0072] When self-healing breakdown occurs in MPPFC, the energy released by the breakdown of the first dielectric layer easily induces the breakdown of the adjacent metallized PP film, resulting in multiple self-healing holes on the polypropylene film instead of just one. Fig.12 As shown in the figure, the maximum number of PP film layers that can be penetrated by a single self-healing breakdown can reach 4 layers, and the damage range of the aluminum electrode can reach 5 layers. Every time a layer of PP film is penetrated, a self-healing hole will be left on the PP film. While leaving a self-healing hole, the aluminum electrode evaporated on the surface of the PP film will also be evaporated, and the adjacent layers of PP film and aluminum electrode will be affected at the same time. Therefore, the generation of self-healing holes is not limited to the metallized PP film layer where the electrical weak point is located.
[0073] In addition, the loss area of the polypropylene film and the aluminum electrode does not necessarily increase with the increase of the number of breakdown layers. For example, in MPPFC samples s3 and s4, the number of breakdown layers of the polypropylene film is 3 and the number of damaged layers of the aluminum electrode is 4, but the loss area of the polypropylene film and the aluminum electrode is lower than that of the MPPFC sample s2, which has 2 breakdown layers of the polypropylene film and 3 damaged layers of the aluminum electrode. Fig.12 It can be seen that when the MPPFC undergoes self-healing breakdown behavior, the loss area of the aluminum electrode is significantly higher than the loss area of the polypropylene film.
[0074] By applying the above technical solution, it can be seen that the present invention uses finite element simulation software to simulate the local electric field of the MPPFC self-healing point, and then builds a test platform to test and verify the simulation results. The simulation results show a good agreement with the test results. Based on the above results, the following conclusions are drawn:
[0075] First, after the self-healing breakdown of the metallized polypropylene film capacitor occurs, the electric field strength tends to be concentrated at the upper / lower edges of the electrode loss area, resulting in a significant increase in the current density and power density at the upper / lower edges of the electrode loss area. Through a single self-healing breakdown experiment, it was found that the axial damage degree of the metallized polypropylene film was significantly higher than that of the tangential damage, indicating that the electrode loss after self-healing breakdown mainly extends along the axial direction.
[0076] Second, during the microsecond self-healing breakdown process, the loss area shapes of the aluminum electrode layer and the polypropylene film layer are asymmetric, and the main breakdown is more likely to occur in the metallized polypropylene film layer where the high-voltage electrode is located.
[0077] Third, the self-healing energy increases exponentially with the increase of the self-healing voltage, and the correlation coefficient α of the self-healing voltage ranges from 2.10 to 2.54. In addition, the damage to the metallized polypropylene film by a single self-healing breakdown can reach up to 5 layers, indicating that the generation of self-healing holes is not limited to the metallized polypropylene film layer where the electrical weak point is located.
[0078] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.
Claims
1. A numerical simulation method for electrode loss of metallized polypropylene film capacitor, characterized in that: include: Build a self-healing breakdown test platform for metallized polypropylene film capacitors, and obtain metallized polypropylene film capacitors that have undergone a single self-healing breakdown through a voltage-boosting experiment; Disassemble the metallized polypropylene film capacitor that has undergone a single self-healing breakdown and obtain a micrograph of the electrode loss morphology; Construct a geometric model of metallized polypropylene film; depict the electrode loss morphology on the metal electrode of the geometric model based on the electrode loss morphology micrograph; Set initial and boundary conditions; Set the material property parameters; mesh the geometric model before and after self-healing breakdown; Finite element calculation was performed on the geometric model to obtain the electrode electric field distribution cloud map before and after self-healing breakdown.
2. The method for numerical simulation of electrode loss of metallized polypropylene film capacitor according to claim 1, characterized in that: According to the electrical signal waveform of the metallized polypropylene film capacitor during a single self-healing breakdown, the sampling current rising curve is fitted to obtain the fitting equation of the sampling current rising curve; the fitting equation is used as the fitting current source on one side of the gold-sprayed end of the metallized polypropylene film.
3. The method for numerical simulation of electrode loss of metallized polypropylene film capacitor according to claim 1, characterized in that: The method of obtaining a metallized polypropylene film capacitor that has a single self-healing breakdown through a voltage boosting experiment specifically comprises: performing a self-healing breakdown experiment of MPPFC at room temperature, boosting the voltage of the experimental sample to 2000V at a rate of 25V / s, and selecting the MPPFC sample that only has a single self-healing breakdown phenomenon; or, when the single self-healing breakdown phenomenon occurs during the process of boosting the voltage of the experimental sample to 2000V at a rate of 25V / s at room temperature, turning off the DC power supply to obtain the MPPFC sample that has a single self-healing breakdown phenomenon.
4. The method for numerical simulation of electrode loss of metallized polypropylene film capacitor according to claim 1, characterized in that: The metallized polypropylene film capacitors that underwent a single self-healing breakdown were disassembled, and the electrodes of each MPPFC sample that underwent a single self-healing breakdown were imaged using an optical microscope to obtain a micrograph of the electrode loss morphology.
5. The method for numerical simulation of electrode loss of metallized polypropylene film capacitor according to claim 1, characterized in that: The method of constructing a geometric model of a metallized polypropylene film specifically comprises: constructing a geometric model of a metallized polypropylene film with a preset number of layers, performing dimensionality reduction processing on metal electrodes in the geometric model, setting the surface of the polypropylene film as an electrical shield and setting a part of it as a metal electrode, and setting the remaining part as an edge-retaining air gap.
6. The method for numerical simulation of electrode loss of metallized polypropylene film capacitor according to claim 1, characterized in that: The setting of initial conditions and boundary conditions includes: 1) the initial current of the entire geometric model is 0; 2) an electric shield is set on the polypropylene surface to represent an aluminum electrode with a thickness of 20 nanometers and a width of 23 millimeters and a 2 millimeter margin air gap; 3) a fitting current source is applied on one side of the gold-sprayed end, and the other side of the gold-sprayed end is grounded.
7. The method for numerical simulation of electrode loss of metallized polypropylene film capacitor according to claim 1, characterized in that: The meshing of the geometric model after self-healing breakdown is performed: the boundary of the electrode loss area is divided by custom meshing, the mesh in the electrode loss area is encrypted, the remaining electrodes and the edge air gap are adaptively meshed using free triangles, and finally the sweep command is used to realize the meshing of the three-dimensional entity.