A metallized film electrode corrosion observation device and method

Abstract

The present invention discloses a metallized film electrode corrosion observation device and method. The present invention adopts two layers of single-sided metallized film to simulate capacitors, the metallized film sample is placed inside a constant temperature and humidity chamber, the temperature and humidity are controlled by the constant temperature and humidity chamber, a high-frequency voltage source is used to apply voltage to both ends of the metallized film sample, and the voltage amplitude and frequency are measured by an oscilloscope. During the test, an optical microscope is used to observe the diameter of the metallized film electrode corrosion point or the electrode edge degradation distance, and then the electrode corrosion rate under different voltage amplitudes, frequencies and electrode components can be obtained. The test device of the present invention is simple, the measurement method is convenient, the operability is strong, and the observation result is highly accurate.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallized film corrosion measurement, and more specifically, relates to a metallized film electrode corrosion observation device and method. Background Art

[0002] Metallized film capacitors are widely used to suppress electromagnetic interference in lines and are usually connected in parallel in AC lines to ensure stable operation of the lines. In recent years, the application of metallized film capacitors in low-power capacitor power supplies has gradually expanded. At this time, the capacitor is connected in series with the load (such as a smart meter) to limit the current. For the application scenarios of RC step-down power supplies that cross the two lines of the power grid and outdoor meters in industrial applications, metallized film capacitors will encounter high temperature and / or high humidity environments, and the capacitance will gradually decrease. The anatomical analysis of failed capacitors shows that the electrodes with nanometer thickness have oxidized. Taking aluminum electrodes as an example, when the electrodes are oxidized to aluminum oxide with good insulating properties, the effective area of ​​the electrodes decreases and the capacitance decreases. In traditional applications where capacitors are connected across wires, the capacitors are only used as filters, and the actual capacitance may change significantly, but with little or no effect on the load. However, when the capacitor is connected in series with the load, the stability of the capacitor is critical to ensure the stability of the load current.

[0003] Therefore, as the application of metallized film capacitors becomes more and more extensive and the working environment becomes increasingly complex, the degradation problem caused by the corrosion of metallized film capacitor electrodes has become a problem that cannot be ignored. The research on the corrosion of metallized film electrodes can provide theoretical guidance for the evaluation of capacitor working performance, life prediction, reliability analysis and structural optimization design. Summary of the invention

[0004] In view of the defects and improvement needs of the prior art, the present invention provides a metallized film electrode corrosion observation device and method, which can observe the corrosion process of the metallized film electrode.

[0005] To achieve the above-mentioned object, in a first aspect, the present invention provides a metallized film electrode corrosion observation device, comprising: a metallized film sample, a constant temperature and humidity chamber, a voltage regulator and an optical microscope;

[0006] The metallized film sample comprises high and low voltage electrodes and upper and lower metallized films which are partially overlapped, and the upper and lower metallized films have margin areas on opposite sides along the length extension direction, and the high and low voltage electrodes are respectively placed closely on the non-overlapping areas of the upper and lower metallized films;

[0007] The metallized film sample is placed in the constant temperature and humidity chamber, and the high and low voltage electrodes are extended to the outside of the constant temperature and humidity chamber through wires and connected to the voltage regulator;

[0008] The constant temperature and humidity box is placed on the observation platform of the optical microscope to observe the corrosion process of the metallized film sample.

[0009] Furthermore, a transparent object is placed in the overlapping area of ​​the upper and lower metallized films to simulate the interlayer pressure of the metallized films.

[0010] Furthermore, a margin area is provided at one end of the upper and lower metallized films in the overlapping area.

[0011] Furthermore, the high and low voltage electrodes are electrically connected to the upper and lower metallized films through the aluminum foil, and the surfaces of the upper and lower metallized films in contact with the aluminum foil are coated with conductive silver glue.

[0012] Furthermore, the device also includes a high-frequency voltage source for applying an alternating voltage across the metallized film sample.

[0013] Further, the device also includes an oscilloscope, an electronic eyepiece, a display and an isolation transformer;

[0014] Wherein, the oscilloscope is used to measure the voltage amplitude and frequency borne by both ends of the metallized film sample;

[0015] The electronic eyepiece is used to display the image observed by the optical microscope on the display;

[0016] The isolation transformer is used to supply power to the optical microscope, oscilloscope, electronic eyepiece and display.

[0017] In a second aspect, the present invention provides a method for observing corrosion of a metallized film electrode implemented based on the metallized film electrode corrosion observation device described in the first aspect, comprising the following steps:

[0018] S1, according to Calculate the capacitance of the metallized film sample, where ε0 is the vacuum dielectric constant, ε r is the relative dielectric constant of the dielectric film, S is the area of ​​the overlapped region of the upper and lower metallized films, and d is the thickness of a single metallized film; the capacitance of the metallized film sample is measured by connecting the high and low voltage electrodes to the LCR digital bridge; if the difference between the measured value and the calculated value of the capacitance of the metallized film sample is within the allowable range, then execute S2, otherwise, re-prepare the metallized film sample;

[0019] S2, placing the metallized film sample in a constant temperature and humidity chamber, turning on the optical microscope, electronic eyepiece, display and oscilloscope, finding the electrode edge area of ​​the metallized film sample under the lens, and adjusting the focus of the optical microscope until the image on the display is clear;

[0020] S3, adjusting the temperature and humidity in the constant temperature and humidity chamber to the temperature setting value and the humidity setting value;

[0021] S4, adjusting the voltage and frequency at both ends of the metallized film sample to the voltage setting value and the frequency setting value;

[0022] S5, turn on the electronic eyepiece video recording function, and after the voltage across the metallized film sample is stable, adjust the focus of the optical microscope again until the image on the display is clear;

[0023] S6, readjust the focus of the optical microscope at intervals of the first preset time, and adjust the power supply voltage at the same time to make the voltage deviation at both ends of the metallized film sample within the deviation range, until the electrode edge degradation distance of the metallized film sample has no obvious change within the second preset time, stop the test, save the video, and obtain a curve of the degradation distance changing with time through the video.

[0024] Furthermore, S4 includes: adjusting the voltage across the metallized film sample to 5% to 10% of the voltage setting value, adjusting the frequency across the metallized film sample to the frequency setting value, and then adjusting the voltage across the metallized film sample to the voltage setting value.

[0025] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0026] (1) The present invention uses two layers of single-sided metallized films to simulate capacitors. The metallized film sample is placed inside a constant temperature and humidity chamber. The temperature and humidity are controlled by the constant temperature and humidity chamber. A high-frequency voltage source is used to apply voltage to both ends of the metallized film sample, and the voltage amplitude and frequency are measured by an oscilloscope. During the test, an optical microscope is used to observe the edge degradation distance of the metallized film electrode, and then the electrode corrosion rate under different voltage amplitudes, frequencies and electrode compositions can be obtained. The test device of the present invention is simple, the measurement method is convenient, the operability is strong, and the observation results are highly accurate.

[0027] (2) The present invention provides a margin area at one end of the overlapping area of ​​the upper and lower metallized films to ensure insulation between the high and low voltage electrodes.

[0028] (3) The high and low voltage electrodes of the present invention are electrically connected to the upper and lower metallized films through the aluminum foil. The surfaces of the upper and lower metallized films in contact with the aluminum foil are coated with conductive silver glue to ensure the stability of the electrical connection between the aluminum foil and the upper and lower metallized films, while preventing electrode loss caused by local discharge on the surface of the metal layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a metallized film electrode corrosion observation device provided in an embodiment of the present invention.

[0030] Figure 2 It is a schematic diagram of a metallized film sample provided in an embodiment of the present invention.

[0031] Figure 3It is a flow chart of a method for observing corrosion of a metallized film electrode provided in an embodiment of the present invention.

[0032] Figure 4 It is a schematic diagram of a curve showing the variation of the edge degradation distance of a metallized film electrode with time provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

[0035] Example 1

[0036] See also Figure 1 The present invention provides a metallized film electrode corrosion observation device, comprising: a metallized film sample, a constant temperature and humidity chamber, a high-frequency voltage source, a voltage regulator, an optical microscope, an oscilloscope, an electronic eyepiece, a display and an isolation transformer.

[0037] Among them, Figure 2 As shown, the metallized film sample includes high and low voltage electrodes and upper and lower metallized films partially overlapped, and the opposite sides of the upper and lower metallized films are provided with margin areas along the length extension direction, and the upper and lower metallized films are also provided with margin areas at one end of the overlapping area to ensure the insulation between the high and low voltage electrodes. The high and low voltage electrodes are respectively placed closely in the non-overlapping areas of the upper and lower metallized films, and the high and low voltage electrodes are electrically connected to the upper and lower metallized films through aluminum foil. The surfaces of the upper and lower metallized films in contact with the aluminum foil are coated with conductive silver glue. After drying, the aluminum foil and the high and low voltage electrodes are placed to ensure the stability of the electrical connection between the aluminum foil and the metallized film, and to prevent the electrode loss caused by local discharge on the surface of the metal layer. A transparent object is placed in the overlapping area of ​​the upper and lower metallized films to simulate the interlayer pressure of the metallized film and reduce the gap distance between the film layers; preferably, the transparent object is organic glass.

[0038] The constant temperature and humidity chamber is used to control the ambient temperature and humidity. The metallized film sample is placed in the constant temperature and humidity chamber. The constant temperature and humidity chamber is provided with a wire outlet hole for extending the high and low voltage electrodes to the outside of the constant temperature and humidity chamber through wires and connecting them to the voltage regulator.

[0039] An oscilloscope is used to measure the voltage amplitude and frequency to which the metallized film sample is subjected.

[0040] The high frequency voltage source applies an alternating voltage across the metallized film sample and adjusts the frequency across the metallized film sample.

[0041] The voltage regulator is used to adjust the voltage across the metallized film sample, and the protection resistor is used to limit the loop current.

[0042] Isolation transformers are used to power optical microscopes, oscilloscopes, electronic eyepieces and displays to ensure personal safety and equipment safety.

[0043] The images observed by the optical microscope are displayed on the monitor through the electronic eyepiece, and the videos taken by the electronic eyepiece are stored in storage media such as mobile hard disks. The magnification of the electronic eyepiece is calculated as L = a·b·c / d, where a is the magnification of the objective lens; b is the magnification of the eyepiece adapter; c is the diagonal size of the monitor screen; and d is the target surface size of the camera eyepiece.

[0044] Example 2

[0045] See also Figure 3 The present invention provides a method for observing corrosion of a metallized film electrode, comprising the following steps:

[0046] S1, according to Calculate the capacitance of the metallized film sample, where ε0 is the vacuum dielectric constant, ε r is the relative dielectric constant of the dielectric film, S is the area of ​​the overlapping region of the upper and lower metallized films, and d is the thickness of a single metallized film; the capacitance of the metallized film sample is measured by connecting the high and low voltage electrodes to the LCR digital bridge (the test frequency is 1000 Hz); if the difference between the measured value and the calculated value of the capacitance of the metallized film sample is within the allowable range (for example, not exceeding 20%), then execute S2, otherwise, re-prepare the metallized film sample;

[0047] S2, placing the metallized film sample in a constant temperature and humidity chamber, turning on the optical microscope, electronic eyepiece, display and oscilloscope, finding the electrode edge area of ​​the metallized film sample under the lens, and adjusting the focus of the optical microscope until the image on the display is clear;

[0048] S3, adjusting the temperature and humidity in the constant temperature and humidity chamber to the temperature setting value and the humidity setting value;

[0049] S4, adjusting the voltage and frequency at both ends of the metallized film sample to the voltage setting value and the frequency setting value;

[0050] S5, turn on the electronic eyepiece video recording function, and after the voltage across the metallized film sample is stable, adjust the focus of the optical microscope again until the image on the display is clear;

[0051] S6. Re-adjust the focus of the optical microscope every first preset time (for example, 30 minutes), and adjust the power supply voltage at the same time to make the voltage deviation at both ends of the metallized film sample within the deviation range, until the electrode edge degradation distance of the metallized film sample has no obvious change within the second preset time (for example, 1 hour), stop the test, save the video, and obtain a curve of the degradation distance changing with time through the video. The slope of the curve can characterize the corrosion rate of the metallized film electrode.

[0052] In addition, in addition to observing the electrode edge degradation distance of the metallized film sample, the corrosion rate of the metallized film electrode can also be obtained by observing the changes in the corrosion points. The difference is that in S2, the overlapping area of ​​the upper and lower metallized films is found under the lens. After S5, it also includes: turning off the voltage source 30 minutes after power-on, and looking for observable corrosion points in the overlapping area of ​​the upper and lower metallized films through an optical microscope. In S6, until the corrosion point diameter of the metallized film sample has no obvious change within the second preset time, stop the test, save the video, and obtain the curve of the corrosion point diameter changing with time through the video.

[0053] In this embodiment, the thickness d of a single metallized film is 6.8 μm, and the area S of the overlapping region of the upper and lower metallized films is 1020 mm 2 ,according to The capacitance of the metallized film sample is calculated to be 2.92nF; the capacitance of the metallized film sample is measured to be 2.86nF (test frequency is 1000Hz) by connecting the high and low voltage electrodes to the LCR digital bridge. The difference between the measured value and the calculated value is no more than 20%, and the metallized film sample is valid. Place the metallized film sample in a constant temperature and humidity chamber, turn on the optical microscope, electronic eyepiece, display and oscilloscope, find the electrode edge area of ​​the metallized film sample under the lens, adjust the focus of the optical microscope until the picture on the display is clear, and the magnification of the optical microscope is calculated to be 340 times. The temperature of the constant temperature and humidity chamber is set to 25℃, and the humidity is set to 50%. The voltages at both ends of the metallized film sample are set to 305Vrms and 400Vrms respectively, and the frequency is set to 5kHz. The voltage regulator is controlled to slowly increase the voltage to 30V, and the voltage and frequency at both ends of the metallized film sample are observed through the oscilloscope, and the power supply frequency is adjusted to 5kHz. Control the voltage regulator to continue to slowly increase the voltage to 305Vrms and 400Vrms respectively, turn on the electronic eyepiece recording function, and adjust the focus of the optical microscope again after the voltage at both ends of the metallized film sample is stable until the image on the display is clear. During the test, readjust the focus of the optical microscope approximately every 30 minutes, and adjust the power supply voltage at the same time to ensure that the voltage deviation at both ends of the sample is within the range of ±1%. After 255 minutes of the test, there is no obvious change in the electrode edge degradation distance within 1 hour, so stop the test and measure the degradation distance change curve over time through the video recording, such as Figure 4As described above, for 305 Vrms, the slope of the curve is k1 = 0.68 μm / min, k2 = 0.07 μm / min; for 400 Vrms, the slope of the curve is k1 = 1.18 μm / min, k2 = 0.10 μm / min.

[0054] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A metallized film electrode corrosion observation device, characterized in that: include: Metallized film samples, constant temperature and humidity chamber, voltage regulator and optical microscope; The metallized film sample comprises high and low voltage electrodes and upper and lower metallized films which are partially overlapped, and the upper and lower metallized films have margin areas on opposite sides along the length extension direction, and the high and low voltage electrodes are respectively placed closely on the non-overlapping areas of the upper and lower metallized films; The metallized film sample is placed in the constant temperature and humidity chamber, and the high and low voltage electrodes are extended to the outside of the constant temperature and humidity chamber through wires and connected to the voltage regulator; The constant temperature and humidity chamber is placed on the observation platform of the optical microscope to observe the corrosion process of the metallized film sample; A transparent object is placed in the overlapping area of ​​the upper and lower metallized films to simulate the interlayer pressure of the metallized films; and a margin area is provided at one end of the overlapping area of ​​the upper and lower metallized films.

2. The metallized film electrode corrosion observation device according to claim 1, characterized in that: The high and low voltage electrodes are electrically connected with the upper and lower metallized films through the aluminum foil, and the surfaces of the upper and lower metallized films in contact with the aluminum foil are coated with conductive silver glue.

3. The metallized film electrode corrosion observation device according to claim 1, characterized in that: The device also includes a high frequency voltage source for applying an alternating voltage across the metallized film sample.

4. The metallized film electrode corrosion observation device according to claim 1, characterized in that: The device also includes an oscilloscope, an electronic eyepiece, a display and an isolation transformer; Wherein, the oscilloscope is used to measure the voltage amplitude and frequency borne by both ends of the metallized film sample; The electronic eyepiece is used to display the image observed by the optical microscope on the display; The isolation transformer is used to supply power to the optical microscope, oscilloscope, electronic eyepiece and display.

5. A method for observing corrosion of a metallized film electrode implemented based on the metallized film electrode corrosion observation device according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, according to Calculate the capacitance of the metallized film sample, where ε0 is the vacuum dielectric constant, ε r is the relative dielectric constant of the dielectric film, S is the area of ​​the overlapped region of the upper and lower metallized films, and d is the thickness of a single metallized film; the capacitance of the metallized film sample is measured by connecting the high and low voltage electrodes to the LCR digital bridge; if the difference between the measured value and the calculated value of the capacitance of the metallized film sample is within the allowable range, then execute S2, otherwise, re-prepare the metallized film sample; S2, placing the metallized film sample in a constant temperature and humidity chamber, turning on the optical microscope, electronic eyepiece, display and oscilloscope, finding the electrode edge area of ​​the metallized film sample under the lens, and adjusting the focus of the optical microscope until the image on the display is clear; S3, adjusting the temperature and humidity in the constant temperature and humidity chamber to the temperature setting value and the humidity setting value; S4, adjusting the voltage and frequency at both ends of the metallized film sample to the voltage setting value and the frequency setting value; S5, turn on the electronic eyepiece video recording function, and after the voltage across the metallized film sample is stable, adjust the focus of the optical microscope again until the image on the display is clear; S6, readjust the focus of the optical microscope at intervals of the first preset time, and adjust the power supply voltage at the same time to make the voltage deviation at both ends of the metallized film sample within the deviation range, until the electrode edge degradation distance of the metallized film sample has no obvious change within the second preset time, stop the test, save the video, and obtain a curve of the degradation distance changing with time through the video.

6. The method for observing corrosion of a metallized film electrode according to claim 5, characterized in that: The S4 includes: adjusting the voltage across the metallized film sample to 5% to 10% of the voltage setting value, adjusting the frequency across the metallized film sample to the frequency setting value, and then adjusting the voltage across the metallized film sample to the voltage setting value.

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