Method and apparatus for detecting the electrical strength of polypropylene film

Abstract

The application discloses a kind of method and device for detecting the electrical strength of polypropylene film, belong to electrical strength detection technical field, its device includes test platform, lower foil, mask, test film, upper foil, first reel group, second reel group and third reel group, and the mask is provided with through-hole;Its method includes that upper foil is electrified, makes upper foil embed mask through-hole under the action of electrostatic force, then continues to boost, until test film is broken down, records the voltage and breakdown position when breakdown, after breakdown, the relative position of lower foil, test film, upper foil and mask through-hole is adjusted by first reel group, second reel group and third reel group.The application is realized by first reel group, second reel group and third reel group that lower foil, test film and upper foil are replaced automatically, so as to solve the technical problem that electrode needs to be manually wiped by technical personnel after multiple tests in prior art, effectively reduce the work burden of technical personnel.

Description

Technical Field

[0001] This invention relates to the field of electrical strength testing, and in particular to a method and apparatus for testing the electrical strength of polypropylene film. Background Technology

[0002] The dielectric material of power capacitors is mainly polypropylene film. However, if the polypropylene film experiences a weak point breakdown, it will cause the entire component of the power capacitor to fail. Therefore, in the process of evaluating the electrical strength of polypropylene film, in addition to assessing the average breakdown field strength distribution, it is also necessary to test the minimum breakdown field strength of the polypropylene film.

[0003] Currently, the overall electrical strength assessment of polypropylene films mainly uses the electrode method. Specifically, the film to be tested is sandwiched between upper and lower brass plates, and then a voltage is applied to the upper plate to perform a breakdown test on the film (as per the instruction manual). Figure 1 The system automatically cuts off the power supply and records the voltage at the point of breakdown of the test film. After all test films have been tested, the measured results are filtered, and the average and minimum values ​​of the remaining data are calculated to evaluate the overall electrical strength of the test films.

[0004] Regarding the aforementioned related technologies, the inventors believe the following drawbacks exist: After multiple breakdown discharges, carbon deposits remain on the surface of the brass electrodes. Excessive carbon buildup will affect subsequent breakdown test data, requiring technicians to wipe the brass electrodes. When the number of test films to be tested is large, this increases the workload of technicians during the breakdown test process and reduces the testing efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for testing the electrical strength of polypropylene films, so as to reduce the workload of technicians in the breakdown test process and improve the test efficiency of the breakdown test.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] An apparatus for testing the electrical strength of a polypropylene film includes a test platform. The top of the test platform is provided with a lower electrode foil, a test film, and an upper electrode foil arranged sequentially from bottom to top. The lower electrode foil is grounded, and the upper electrode foil is electrically connected to a power supply and a voltage recorder.

[0008] The test platform is provided with a first roll group on both sides for winding the lower electrode foil, a second roll group on both sides for winding the test film, and a third roll group on both sides for winding the upper electrode foil.

[0009] A mask is provided on the top of the test film, and a through hole is opened through the top of the mask. The bottom of the upper electrode foil abuts against the top of the mask, wherein the upper electrode foil covers the through hole.

[0010] The test platform is equipped with a limiting device for keeping the mask relatively fixed to the test platform, and the mask is detachably connected to the limiting device.

[0011] Preferably, the limiting device includes a first stop block disposed on the top of the test platform for limiting the mask in the horizontal direction, and a second stop block disposed on the top of the test platform for limiting the mask in the vertical direction, wherein the first stop block abuts against the side wall of the mask, and the second stop block abuts against the top of the mask.

[0012] Preferably, the first reel group, the second reel group, and the third reel group have the same winding direction, and the first stop is located on the side of the test platform near the winding shaft of the third reel group.

[0013] Preferably, a camera is provided above the test platform to record the location of the breakdown point of the upper electrode foil.

[0014] Preferably, the test platform is equipped with a lifting pressure shaft for flattening the upper electrode foil.

[0015] Preferably, both the upper electrode foil and the lower electrode foil are aluminum foil.

[0016] Furthermore, the present invention provides a method for detecting the electrical strength of a polypropylene film, comprising the following steps:

[0017] S1. The lower electrode foil and the test film are sequentially wound onto the first roll group and the second roll group. The mask is placed on top of the test film through the limiting device. The upper electrode foil is wound onto the third roll group.

[0018] S2. Ground the lower electrode foil and energize the upper electrode foil. When the upper electrode foil is embedded in the mask through hole under the action of electrostatic force, continue to increase the voltage until the test film is broken down.

[0019] S3. Record the voltage at which the test film breaks down using a voltage recorder;

[0020] S4. Record the breakdown location of the test film;

[0021] S5. Drive the first roll group, the second roll group and the third roll group to rewind the lower electrode foil, the test film and the upper electrode foil, so that the breakdown test area of ​​the lower electrode foil and the upper electrode foil in S2 is completely offset from the through hole. Repeat S2-S5 until the test film on the second roll group is tested.

[0022] S6. Replace the test film of the second roll group, remove the mask, reverse the first roll group and the third roll group until the lower electrode foil and the upper electrode foil are reset, replace the mask, so that the through holes of the front and rear masks are completely offset in the direction perpendicular to the winding direction of the upper electrode foil, repeat S2-S6 until all test films are tested.

[0023] S7. Calculate the average and minimum values ​​of the collected data to evaluate the overall electrical strength of the test film.

[0024] 1. After the lower electrode foil, test film, mask, and upper electrode foil are sequentially laid on the top of the test platform from bottom to top, the lower electrode foil is grounded and the upper electrode foil is energized. This allows the upper electrode foil to embed into the through-hole of the mask under the action of electrostatic force, while simultaneously expelling air between the upper electrode foil and the mask, ensuring a tight fit between them. At this point, the portion of the upper electrode foil embedded in the through-hole forms the discharge electrode. After the breakdown test is completed, driving the first, second, and third reel groups to rotate completely separates the areas of the lower electrode foil, test film, and upper electrode foil that have been used from the through-hole of the mask. This avoids the influence of carbon buildup on the electrode surface on the test results and eliminates the need for technicians to manually wipe the discharge electrodes, reducing their workload.

[0025] 2. Since the shape of the discharge electrode formed by the upper electrode foil at the mask through-hole is consistent with the through-hole, the contact area between the discharge electrode and the test film can be adjusted by controlling the shape of the mask through-hole, thereby meeting different testing requirements. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of an electrode-based detection device in the prior art.

[0027] Figure 2 This is a schematic diagram of the detection device in an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the mask structure in an embodiment of the present invention.

[0029] Figure 4 This is a schematic diagram of the structure of the scroll assembly in an embodiment of the present invention.

[0030] Figure 5 This is a top view of the test platform in an embodiment of the present invention.

[0031] Figure 6 This is a schematic diagram of the limiting device in an embodiment of the present invention.

[0032] Figure 7 This is a schematic diagram illustrating the change in the position of the mask through-holes before and after mask replacement in an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached drawings: 1. Test platform; 11. Camera; 12. Lifting pressure shaft; 13. First stop; 14. Second stop; 21. Lower electrode plate; 22. Upper electrode plate; 3. Test film; 4. Mask; 51. Upper electrode foil; 52. Lower electrode foil; 61. Lower electrode winding shaft; 62. Lower electrode unwinding shaft; 71. Sample winding shaft; 72. Sample unwinding shaft; 81. Upper electrode winding shaft; 82. Upper electrode unwinding shaft. Detailed Implementation

[0034] The following is in conjunction with the appendix Figure 2-7 The present invention will be described in further detail below.

[0035] This invention discloses a method and apparatus for detecting the electrical strength of polypropylene film.

[0036] Reference Figure 2 A device for testing the electrical strength of polypropylene film includes a test platform 1. A lower electrode foil 52, a test film 3, a mask 4, and an upper electrode foil 51 are sequentially laid on the top of the test platform 1 from bottom to top. Both the upper electrode foil 51 and the lower electrode foil 52 are aluminum foils, with the lower electrode foil 52 grounded. The upper electrode foil 51 is electrically connected to a power supply and a voltage recorder (not shown in the figure). The mask 4 is relatively fixed to the test platform 1 by a limiting device. In this embodiment, the power supply is equipped with a voltage recorder function, which automatically cuts off power and records the breakdown voltage after the test film 3 is broken down.

[0037] Reference Figure 3 A through hole is provided at the top of the mask 4, and the top opening of the through hole is completely covered by the upper electrode foil 51.

[0038] After the upper electrode foil 51 is energized, it adheres to the mask 4 and is embedded in the through hole under the action of electrostatic force, while the air between the upper electrode foil 51 and the mask 4 is discharged. At this time, the part of the upper electrode foil 51 embedded in the through hole forms a discharge electrode, which discharges and breaks down the test film 3 located at the bottom opening of the through hole.

[0039] Meanwhile, since both the upper foil 51 and the lower foil 52 are made of aluminum foil, the breakdown test electrodes are both aluminum electrodes. On the one hand, since power capacitors are connected to aluminum electrodes in most uses, using aluminum electrodes for breakdown testing allows the test film 3 to simulate the actual operating environment of power capacitors, making the test results closer to reality. On the other hand, compared with brass electrodes, aluminum electrodes can reduce the influence of electrode surface roughness and carbon buildup during the test on the breakdown voltage.

[0040] Reference Figure 4To facilitate the automatic replacement of the upper electrode foil 51, test film 3, and lower electrode foil 52 after the breakdown test, a first roll group for winding the lower electrode foil 52, a second roll group for winding the test film 3, and a third roll group for winding the upper electrode foil 51 are installed on both sides of the test platform 1.

[0041] In this embodiment, the first reel group includes a lower electrode take-up reel 61 and a lower electrode unwind reel 62 respectively installed on both sides of the test platform 1; the second reel group includes a sample take-up reel 71 and a sample unwind reel 72 respectively installed on both sides of the test platform 1; and the third reel group includes an upper electrode take-up reel 81 and an upper electrode unwind reel 82 respectively installed on both sides of the test platform 1. The lower electrode take-up reel 61, the sample take-up reel 71, and the upper electrode take-up reel 81 are all located on the same side of the test platform 1, so that the winding directions of the lower electrode foil 52, the test film 3, and the upper electrode foil 51 are consistent.

[0042] When the first, second, and third reel groups are started, the lower electrode foil 52, the test film 3, and the upper electrode foil 51 can be wound up to a certain length, so that the breakdown areas of the lower electrode foil 52, the test film 3, and the upper electrode foil 51 are completely misaligned with the through-hole opening of the mask 4. This eliminates the need for technicians to wipe the electrodes, reducing their workload and improving the efficiency of breakdown testing.

[0043] Furthermore, since the shape of the discharge electrode formed by the upper electrode foil 51 at the through hole of the mask 4 is consistent with the through hole, the contact area between the discharge electrode and the test film 3 can be adjusted by controlling the shape of the through hole of the mask 4, thereby meeting the testing requirements of different sizes of breakdown areas.

[0044] Furthermore, according to electromagnetic principles, the larger the ratio of the contact area between the upper electrode foil 51 and the mask 4 to the opening area of ​​the via, the smaller the electric field distortion at the edge of the via and the more uniform the electric field. This effectively reduces the interference of the electric field distortion at the electrode edge on the edge data of the test film 3 during breakdown, improving the accuracy of the electrical strength assessment of the test film 3. In addition, because the air between the mask 4 and the upper electrode foil 51 is expelled, the upper electrode foil 51 and the mask 4 are in full contact, reducing the interference of external air on the breakdown test.

[0045] Reference Figure 5 and Figure 6The limiting device includes a first stop 13 and a second stop 14. In this embodiment, there are two first stop 13s, which are vertically fixed to the side of the test platform 1 near the upper electrode winding shaft 81. There are also two second stop 14s, which are vertically fixed to the side of the test platform 1 near the upper electrode unwinding shaft 82. The shape of the second stop 14 is a "7"-shaped structure formed by connecting the ends of the horizontal and vertical parts, so that a gap is left between the bottom of the horizontal part of the second stop 14 and the top of the test platform 1 for the mask 4 to pass through.

[0046] Meanwhile, in this embodiment, the mask 4 is made of PET film, which gives the mask 4 a certain degree of rigidity, making it easier for the first stop 13 and the second stop 14 to limit the mask 4.

[0047] When the limiting device is in use, the side wall of the mask 4 near the upper electrode take-up shaft 81 abuts against the first stop 13, and the top of the mask 4 near the upper electrode unwind shaft 82 abuts against the bottom of the horizontal part of the second stop 14. This allows the first stop 13 to limit the horizontal movement of the mask 4, and the second stop 14 to limit the vertical movement of the mask 4. At the same time, since the upper electrode foil 51, the test film 3, and the lower electrode foil 52 all move from the upper electrode unwind shaft 82 side to the upper electrode take-up shaft 81 side, the mask 4 remains pressed against the first stop 13 during the replacement of the test film 3. This prevents the mask 4 from sliding off the second stop 14 side during testing, and also makes it easier to remove the mask 4 from the second stop 14 side after the puncture test is completed.

[0048] In addition, refer to Figure 4 and Figure 5 A lifting pressure shaft 12 is installed on the top of the test platform 1. The lifting pressure shaft 12 can move in the vertical direction. The lifting pressure shaft 12 is existing technology, so the specific structure and lifting principle of the lifting pressure shaft 12 will not be described in detail. When the lifting pressure shaft 12 moves downward and presses down on the upper electrode foil 51, it can keep the upper electrode foil 51 flat during the test.

[0049] In addition, a camera 11 is installed on the top of the test platform 1 to record the puncture location of the test film 3. Specifically, when the test film 3 is punctured, the upper electrode foil 51 and the lower electrode foil 52 are thinner, and the part of the upper electrode foil 51 embedded in the through hole of the mask 4 under the action of electrostatic force is tightly attached to the test film 3. Therefore, holes will appear on the surfaces of the upper electrode foil 51 and the lower electrode foil 52 at the locations corresponding to the puncture location of the test film 3, so that the camera 11 can determine the puncture location of the test film 3 by photographing the location of the hole on the upper electrode foil 51.

[0050] Furthermore, embodiments of the present invention also disclose a method for detecting the electrical strength of a polypropylene film, comprising the following steps:

[0051] S1. The lower electrode foil 52 and the test film 3 are sequentially wound onto the first roll group and the second roll group. The mask 4 is inserted from one side of the second stop 14 and abuts against the side wall of the first stop 13. The upper electrode foil 51 is wound onto the third roll group.

[0052] S2. Drive the lifting and lowering shaft 12 to press down, ground the lower electrode foil 52, and energize the upper electrode foil 51. When the upper electrode foil 51 is embedded in the through hole of the mask 4 under the action of electrostatic force, the pressure is continued to rise until the test film 3 is broken down.

[0053] S3. Power supply recording test: Voltage at which film 3 breaks down;

[0054] S4. The camera captures the location of the breakdown of the test film 3;

[0055] S5. Drive the lifting pressure shaft 12 to rise, and the first roll group, the second roll group and the third roll group rotate to rewind the lower electrode foil 52, the test film 3 and the upper electrode foil 51, so that the breakdown test area of ​​the lower electrode foil 52 and the upper electrode foil 51 in S2 is completely offset from the through hole, and the shortest distance between the hole formed by the upper electrode foil 51 and the lower electrode foil 52 in S2 and the through hole opening of the mask 4 is more than ten times the thickness of the mask 4. Repeat S2-S5 until the test film 3 on the second roll group is tested.

[0056] S6. Replace the test film 3 of the second roll group, take out the mask 4 from the side of the second stop 14, reverse the first roll group and the third roll group until the lower electrode foil 52 and the upper electrode foil 51 are reset, replace the mask 4, so that the through holes of the front and rear masks 4 are completely offset in the direction perpendicular to the winding direction of the upper electrode foil 51, and the shortest distance between the hole formed by the upper electrode foil 51 and the lower electrode foil 52 in S2 and the opening of the through hole of the replaced mask 4 is more than ten times the thickness of the mask 4. Repeat S2-S6 until all test films 3 are tested.

[0057] S7. Calculate the average and minimum values ​​of the collected data to evaluate the overall electrical strength of the test film 3.

[0058] The above method enables the effective utilization of both the lower electrode foil 52 and the upper electrode foil 51, reducing the waste of materials in both the upper electrode foil 51 and the lower electrode foil 52.

[0059] Since the holes formed by the lower electrode foil 52 and the upper electrode foil 51 after the test film 3 is punctured are wound up by the first and third roll groups, the shortest distance between them and the new puncture test area corresponding to the through hole of the mask 4 is ten times the thickness of the mask 4, thus effectively avoiding interference of the puncture holes of the lower electrode foil 52 and the upper electrode foil 51 on the discharge electrode field strength during the puncture test.

[0060] Similarly, refer to Figure 7Since the holes formed by the lower electrode foil 52 and the upper electrode foil 51 after the test film 3 is broken down, after the mask 4 is replaced, the shortest distance d between the holes and the new breakdown test area corresponding to the through holes of the replaced mask 4 is ten times the thickness of the mask 4, which further avoids the interference of the breakdown holes of the lower electrode foil 52 and the upper electrode foil 51 on the discharge electrode field strength during the breakdown test.

[0061] The above are all preferred embodiments of the present invention. These embodiments are merely explanations of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An apparatus for testing the electrical strength of a polypropylene film, comprising a test platform (1), wherein a lower electrode foil (52), a test film (3), and an upper electrode foil (51) are sequentially laid on the top of the test platform (1) from bottom to top, the lower electrode foil (52) being grounded, and the upper electrode foil (51) being electrically connected to a power supply and a voltage recorder, characterized in that: The test platform (1) is provided with a first roll group on both sides for winding the lower electrode foil (52), a second roll group on both sides for winding the test film (3), and a third roll group on both sides for winding the upper electrode foil (51). The test film (3) is provided with a mask (4) on top, and a through hole is provided on the top of the mask (4). The bottom of the upper electrode foil (51) abuts against the top of the mask (4), wherein the upper electrode foil (51) covers the through hole. The test platform (1) is provided with a limiting device for keeping the mask (4) relatively fixed to the test platform (1), and the mask (4) is detachably connected to the limiting device.

2. The apparatus for detecting the electrical strength of polypropylene film according to claim 1, characterized in that: The limiting device includes a first stop (13) disposed on the top of the test platform (1) for limiting the mask (4) in the horizontal direction, and a second stop (14) disposed on the top of the test platform (1) for limiting the mask (4) in the vertical direction, wherein the first stop (13) abuts against the side wall of the mask (4), and the second stop (14) abuts against the top of the mask (4).

3. The apparatus for detecting the electrical strength of polypropylene film according to claim 2, characterized in that: The first reel group, the second reel group, and the third reel group have the same winding direction, and the first stop (13) is located on the side of the test platform (1) near the winding shaft of the third reel group.

4. The apparatus for detecting the electrical strength of polypropylene film according to claim 1, characterized in that: A camera (11) is installed above the test platform (1) to record the location of the breakdown point of the upper electrode foil (51).

5. The apparatus for detecting the electrical strength of polypropylene film according to claim 1, characterized in that: The test platform (1) is equipped with a lifting pressure shaft (12) for flattening the upper electrode foil (51).

6. The apparatus for detecting the electrical strength of polypropylene film according to claim 1, characterized in that: Both the upper electrode foil (51) and the lower electrode foil (52) are aluminum foils.

7. A method for detecting the electrical strength of a polypropylene film, used with the apparatus for detecting the electrical strength of a polypropylene film according to any one of claims 1-6, characterized in that... Includes the following steps: S1. The lower electrode foil (52) and the test film (3) are sequentially wound up to the first roll group and the second roll group. The mask (4) is placed on top of the test film (3) through the limiting device. The upper electrode foil (51) is wound up to the third roll group. S2. Ground the lower electrode foil (52) and energize the upper electrode foil (51). When the upper electrode foil (51) is embedded in the through hole of the mask (4) under the action of electrostatic force, continue to increase the voltage until the test film (3) is broken down. S3. Record the voltage at which the test film (3) breaks down using a voltage recorder; S4. Record the breakdown location of the test film (3); S5. Drive the first roll group, the second roll group and the third roll group to wind up the lower electrode foil (52), the test film (3) and the upper electrode foil (51) so that the breakdown test area of ​​the lower electrode foil (52) and the upper electrode foil (51) in S2 is completely offset from the through hole. Repeat S2-S5 until the test film (3) on the second roll group is tested. S6. Replace the test film (3) of the second roll group, take out the mask (4), reverse the first roll group and the third roll group until the lower electrode foil (52) and the upper electrode foil (51) are reset, replace the mask (4) so ​​that the through holes of the front and rear masks (4) are completely offset in the direction perpendicular to the winding direction of the upper electrode foil (51), repeat S2-S6 until all test films (3) are tested; S7. Calculate the average and minimum values ​​of the collected data and evaluate the overall electrical strength of the test film (3).

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