Round element film and film on-machine winding pressure testing method and application thereof

Abstract

The invention discloses a method for testing the on-machine winding pressure of a circular element film and a film and application of the method, and belongs to the technical field of capacitors. The invention provides a method for testing the on-machine winding pressure of a circular element film and a film, which comprises the following steps of: checking the winding tension of a semi-automatic element winding machine during testing, starting to wind for a small number of circles, stopping, quickly placing a flexible pressure test sensor on a wound film, continuously winding for a plurality of circles, stopping, and finally, continuously winding for a small number of circles. A pressure test sensor reader is connected to read a pressure value, the pressure value and an effective region area in the middle of the sensor are converted to obtain interlayer pressure, and finally the corresponding relation between the actually read pressure value and a calculated value is reversely calculated through a film interlayer pressure calculation formula. Therefore, the correction coefficient K of the pressure intensity between the film layers of different winding mandrels and the actual pressure intensity in the winding process is obtained.

Description

Technical Field

[0001] The invention relates to a circular element film and a testing method for the film's machine winding pressure and application thereof, belonging to the technical field of capacitors. Background Art

[0002] The dry DC support capacitors in flexible DC projects, also known as DC-link capacitors, mainly provide voltage support for IGBTs, filter harmonics, and protect IGBTs. They are widely used in MMC (modular multilevel converter) modules in high-speed rail, subway, and flexible DC transmission projects. As a key component in the MMC module, the safe operation of DC-link capacitors is crucial. DC-link capacitors are dry metallized film capacitors with polypropylene film as the dielectric and zinc-aluminum coatings evaporated on the polypropylene film on the plates. They have self-healing properties, that is, when the film dielectric breaks down, the zinc-aluminum metal coating evaporates rapidly under the action of high current and high heat, thereby isolating the dielectric in the damaged area and allowing the intact dielectrics in other parts to continue to work normally. The self-healing property is the most critical performance of metallized film capacitors.

[0003] The DC-link capacitor used in the flexible DC transmission project has an internal core composed of several round elements, each of which is wound by two layers of metallized film. During the winding process of the round element, there will be pressure between the two layers of film. As the number of winding turns increases, the pressure between the innermost film and the film will increase accordingly. Finally, the pressure of the round element will be reflected in the innermost layer with the largest pressure and the outermost layer with the smallest pressure. In other words, the interlayer pressure between the films of the round element gradually increases from the outside to the inside. Different pressures between layers will directly affect the self-healing characteristics of the metallized film. The self-healing performance test shows that after a certain voltage is applied to the round element, the inner layer of the element has fewer self-healing points, the capacitance loss is small, and the lower self-healing energy will cause the film to self-heal; the outer layer has more self-healing points, the capacitance loss is large, and a higher self-healing energy is required to break down. The different number of self-healing points and self-healing energy of the inner and outer layers are caused by the different pressures between the inner and outer films. The self-healing property of metallized film capacitors is the most important factor affecting their lifespan. Studying the pressure between the films of circular components and controlling the pressure between the films when the components are wound are of great significance to the operating safety and long-term service life of dry DC capacitors.

[0004] At present, the known interlayer pressure test between the membranes of circular components adopts the off-machine test method, which reversely tests the membrane pressure inside the component through piezoelectric conversion. The test steps are as follows:

[0005] 1) First, the pressure sensor 1 is attached to the core shaft of the component 1, and then the component is completely wound without stopping the machine, and the number of winding layers is 500 to 2000;

[0006] 2) Then attach pressure sensor 2 to the core shaft of component 2, the main function of which is to compare the data with that of sensor 1;

[0007] 3) Connect sensors 1 and 2 with two other sensors 3 and 4 to form a bridge type;

[0008] 4) Peel off a certain number of film layers from the component and record the changes in the output value. The number of layers peeled off each time can be from 10 to 100 layers according to the needs;

[0009] 5) Based on the trace change data obtained during each peeling, calculate the curve of pressure change with the number of layers, and calculate the corresponding pressure value based on the strain of the peeled film layer.

[0010] This approach has the following problems:

[0011] A. This method tests the interlayer pressure of the film in the reverse direction after winding is completed. It cannot reflect the actual pressure during the winding process in real time, and it is also impossible to control the actual pressure by adjusting the parameters of the equipment;

[0012] B. It is difficult to implement, because the pressure change caused by the peeling of the film layers of the element is at a trace level, which is very difficult to operate, and the accuracy of the measuring instrument must be high enough;

[0013] C. There are difficulties and deviations in manual operation. When peeling the thin film layer from the component manually, different people use different strengths and operating techniques, which will directly affect the result value. Summary of the invention

[0014] In order to solve at least one of the above problems, the present invention proposes a method for testing the pressure of circular element film and film in machine winding. During the test, a semi-automatic element winding machine is used. The winding tension of the winding machine is first verified, and then the winding is stopped after a small number of turns. The flexible pressure test sensor is quickly placed on the wound film, and then the film is wound for several turns and stopped. The pressure value is connected to the pressure test sensor reader to read the pressure value. The pressure value is converted with the effective area in the middle of the sensor to obtain the interlayer pressure. Finally, the corresponding relationship between the actual read pressure value and the calculated value is reversely calculated through the film interlayer pressure calculation formula. Thus, the correction coefficient K between the interlayer pressure of different winding mandrel films and the actual pressure during the winding process is obtained.

[0015] The first object of the present invention is to provide a method for testing the pressure of a circular element film and a film on a machine, the testing method comprising:

[0016] Step S1: Select a flexible pressure sensor with a measuring range of more than 50 kg, and place a cushion block in the middle of the effective area of ​​the sensor;

[0017] Step S2: Select a metallized winding film with a thickness of 4 μm to 10 μm, put the winding film 1 and the film 2 on the material shaft of the winder, set the tension of the winder, and first wind about 20 to 30 turns to obtain the diameter Dn of the nth round element;

[0018] Step S3: the winding machine stops, and the flexible pressure sensor is quickly placed on the middle plane of the component. After the sensor is placed, the winding machine continues to be wound down. When the winding machine is wound for more than 200 turns, the machine is stopped, and the sensor reader is quickly connected to the sensor to read the pressure value on the sensor at this time.

[0019] Step S4: Repeat the operations of steps S1 to S3 on the same winding machine mandrel to verify the pressure values ​​under different numbers of turns, and convert the obtained pressure values ​​into pressure intensity;

[0020] Step S5: Using the known parameters measured, The pressure between the membrane layers is calculated by the formula and compared with the measured pressure to determine the difference coefficient K between the calculated pressure and the measured pressure under the same winding mandrel; where P n-N ——Pressure between the nth film layers inside the circular element, MPa; T d ——winding tension, N; r 0 ——radius of the mandrel, mm; d——thickness of the metallized film, mm; b——width of the metallized film, mm; D=d 0 +4Nd——component outer diameter, mm; D n =d 0 +4nd——The diameter of the nth circle of the circular element, mm, where d 0 is the core rod diameter, mm.

[0021] Step S6: Replace the winding machine mandrel, repeat the operations of the above steps S1 to S5, and finally obtain the measured value and calculated value correction coefficient K of the pressure between the film layers under different mandrels.

[0022] In one implementation, the thickness of the pad placed in the middle of the sensor effective area in step S1 is 1 mm to 4 mm.

[0023] In one embodiment, the specific steps of step S2 are to select a metallized winding film with a thickness of 4 μm to 10 μm, put the winding film 1 and the film 2 on the winding machine material shaft, put the ends of the two films on the winding machine core shaft, and set the tension T of the winding machine. d , set the value between 300CN and 1000CN, first wind 20 to 30 turns, and get the diameter Dn of the nth turn of the circular element.

[0024] In one embodiment, the mandrel of the winding machine in steps S1 to S6 needs to select a suitable mandrel diameter of the winding machine, because the size of the pressure sensor and the diameter of the mandrel of the winding machine are matched. The pressure sensor is flat and the mandrel is round, so there will be problems in matching the two. It is necessary to determine whether the bending of the pressure-sensitive area affects the measurement results. In order to reduce the influence of this factor, the size of the sensor should be as small as possible and the diameter of the mandrel should be as large as possible.

[0025] In one embodiment, the effective area of ​​the pressure sensor in step S3 has a protective frame. This frame has a great influence on the force applied to the sensor, but the pressure sensor is to be inserted as a whole between the membrane layers of the component, and a way needs to be found to allow the effective area of ​​the sensor to be subjected to force. There are two ways to do this: one is to re-customize the lead wires and remove the protective frame; the other is to add a gasket to ensure that the effective area of ​​the sensor is subjected to force under a controlled state. The modified sensor needs to be recalibrated.

[0026] In one embodiment, after the winding is completed in step S3, the pressure test data should be read quickly. Due to inertia, the winding tension will slowly decrease and the component winding diameter will also slowly increase, so the test should be performed as quickly as possible to reduce the deviation of the measurement results.

[0027] A second object of the present invention is to provide a method for improving the operating safety and service life of a dry DC capacitor.

[0028] In one embodiment, the method is to adjust the pressure between the corresponding element film layers by adjusting the relevant parameters of the winding through the above-mentioned circular element film and film in-machine winding pressure testing method; by adjusting the interlayer pressure of the film, the self-healing energy of the element is improved and the service life of the product is extended.

[0029] The third object of the present invention is to provide a dry DC capacitor, wherein the above-mentioned method for testing the circular element film and the film on-machine winding pressure is adopted in the test verification process of the dry DC capacitor.

[0030] The fourth object of the present invention is to provide a production method of a dry DC capacitor, which includes winding, heat treatment, gold spraying, welding, voltage resistance test, and life test; wherein the life test adopts the above-mentioned round element film and the film in-machine winding pressure test method.

[0031] The beneficial effects of the present invention are:

[0032] 1) The method for testing the pressure of circular element membrane and membrane in machine winding provided by the present invention is to place a flexible pressure test sensor on the wound film, and then connect a pressure test sensor reader to read the pressure value. The pressure value is converted with the effective area in the middle of the sensor to obtain the interlayer pressure, which can reflect the actual pressure in the winding process in real time.

[0033] 2) The present invention adjusts the pressure between the corresponding element membrane layers by adjusting the relevant parameters of the winding; by adjusting the interlayer pressure of the membrane, the self-healing energy of the element is improved and the service life of the product is extended.

[0034] 3) The testing method of the present invention can be applied to the test and verification process of dry-type DC capacitors to determine the most reasonable inter-film pressure, thereby achieving the purpose of prolonging the service life of dry-type DC capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 It is a test schematic diagram of a round element film and a test method of the film on-machine winding pressure of the present invention;

[0037] In the figure, 1 is a flexible pressure sensor, 2 is a wound circular element, 3 is a sensor reader, 4 is a winding machine core shaft, 5 is an effective area, 6 is a winding film 1, and 7 is a winding film 2. DETAILED DESCRIPTION

[0038] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0039] Embodiment 1:

[0040] This embodiment provides a method for testing the pressure of a circular element film and a film on a machine winding. Figure 1 , the method comprising:

[0041] 1) Select a flexible pressure sensor with the maximum pressure test range, the maximum test value is 50kg;

[0042] 2) Select a metalized winding film with a thickness of 4 μm, put the winding film 1 and film 2 on the winding machine material shaft, put the ends of the 2 films on the winding machine core shaft, and set the tension T of the winding machine. d , set the value between 1000CN, first wind 25 turns, and get the diameter D of the 25th turn round element 25 ;

[0043] 3) Stop the winding machine and quickly place the flexible pressure sensor on the middle plane of the component. The effective area of ​​the sensor needs to be placed with a pad in advance. The pad should not be too thick or too thin. It should be thicker than the thickness of the sensor frame. If it is too thick, it will increase the local pressure of the film, and the obtained pressure between the film layers will deviate from the real data.

[0044] 4) After placing the sensor, continue to wind it down, wind it to 200 turns, stop the machine, quickly connect the sensor reader to the sensor, and read the pressure value on the sensor at this time;

[0045] 5) Repeat the above operation on the same winding machine mandrel to verify the pressure values ​​under different numbers of turns; the obtained pressure values ​​are converted into pressure;

[0046] 6) Using the known parameters measured, adopt The pressure between the membrane layers is calculated by the formula and compared with the measured pressure to determine the difference coefficient K between the calculated pressure and the measured pressure under the same winding mandrel; where P n-N ——Pressure between the nth film layers inside the circular element, MPa; T d ——winding tension, N; r 0 ——radius of the mandrel, mm; d——thickness of the metallized film, mm; b——width of the metallized film, mm; D=d 0 +4Nd——component outer diameter, mm; D n =d 0 +4nd——The diameter of the nth circle of the circular element, mm, where d 0 is the core rod diameter, mm;

[0047] 7) Replace the winding machine mandrel, repeat the above operation, and finally obtain the measured value and calculated value correction coefficient K of the pressure between the film layers under different mandrels;

[0048] Embodiment 2:

[0049] This embodiment provides a method for testing the pressure of a circular element film and a film on a machine winding. Figure 1 , the method comprising:

[0050] 1) Select a flexible pressure sensor with the maximum pressure test range, the highest test value is 55kg;

[0051] 2) Select a metalized winding film with a thickness of 8 μm, put the winding film 1 and film 2 on the winding machine material shaft, put the ends of the 2 films on the winding machine core shaft, and set the tension T of the winding machine. d , set the value between 300CN, first wind 30 turns, and get the diameter D of the 30th turn round element 30 ;

[0052] 3) Stop the winding machine and quickly place the flexible pressure sensor on the middle plane of the component. The effective area of ​​the sensor needs to be placed with a pad in advance. The pad should not be too thick or too thin. It should be thicker than the thickness of the sensor frame. If it is too thick, it will increase the local pressure of the film, and the obtained pressure between the film layers will deviate from the real data.

[0053] 4) After placing the sensor, continue to wind it down, wind it to 200 turns, stop the machine, quickly connect the sensor reader to the sensor, and read the pressure value on the sensor at this time;

[0054] 5) Repeat the above operation on the same winding machine mandrel to verify the pressure values ​​under different numbers of turns; the obtained pressure values ​​are converted into pressure;

[0055] 6) Using the known parameters measured, adopt The pressure between the membrane layers is calculated by the formula and compared with the measured pressure to determine the difference coefficient K between the calculated pressure and the measured pressure under the same winding mandrel; where P n-N ——Pressure between the nth film layers inside the circular element, MPa; T d ——winding tension, N; r 0 ——radius of the mandrel, mm; d——thickness of the metallized film, mm; b——width of the metallized film, mm; D=d 0 +4Nd——component outer diameter, mm; D n =d 0 +4nd——The diameter of the nth circle of the circular element, mm, where d 0 is the core rod diameter, mm;

[0056] 7) Replace the winding machine mandrel, repeat the above operation, and finally obtain the measured value and calculated value correction coefficient K of the pressure between the film layers under different mandrels;

[0057] Embodiment three:

[0058] This embodiment provides a method for testing the pressure of a circular element film and a film on a machine winding. Figure 1 , the method comprising:

[0059] 1) Select a flexible pressure sensor with the maximum pressure test range, and the maximum test value is 60kg;

[0060] 2) Select a metalized winding film with a thickness of 10 μm, put the winding film 1 and film 2 on the winding machine material shaft, put the ends of the 2 films on the winding machine core shaft, and set the tension T of the winding machine. d , set the value between 500CN, first wind 20 turns, and get the diameter D of the 20th turn round element 20 ;

[0061] 3) Stop the winding machine and quickly place the flexible pressure sensor on the middle plane of the component. The effective area of ​​the sensor needs to be placed with a pad in advance. The pad should not be too thick or too thin. It should be thicker than the thickness of the sensor frame. If it is too thick, it will increase the local pressure of the film, and the obtained pressure between the film layers will deviate from the real data.

[0062] 4) After placing the sensor, continue to wind it down, wind it to 200 turns, stop the machine, quickly connect the sensor reader to the sensor, and read the pressure value on the sensor at this time;

[0063] 5) Repeat the above operation on the same winding machine mandrel to verify the pressure values ​​under different numbers of turns; the obtained pressure values ​​are converted into pressure;

[0064] 6) Using the known parameters measured, adopt The pressure between the membrane layers is calculated by the formula and compared with the measured pressure to determine the difference coefficient K between the calculated pressure and the measured pressure under the same winding mandrel; where P n-N ——Pressure between the nth film layers inside the circular element, MPa; T d ——winding tension, N; r 0 ——radius of the mandrel, mm; d——thickness of the metallized film, mm; b——width of the metallized film, mm; D=d 0 +4Nd——component outer diameter, mm; D n =d 0 +4nd——The diameter of the nth circle of the circular element, mm, where d 0 is the core rod diameter, mm;

[0065] 7) Replace the winding machine mandrel, repeat the above operation, and finally obtain the measured value and calculated value correction coefficient K of the pressure between the film layers under different mandrels;

[0066] Embodiment 4:

[0067] The present embodiment provides a method for improving the operating safety and service life of a dry-type DC capacitor. The method specifically adjusts the relevant parameters of the winding and the pressure between the corresponding element film layers by adopting a circular element film and a film in-machine winding pressure test method of Example 1, thereby adjusting the interlayer pressure of the film to improve the element self-healing energy and extend the service life of the dry-type DC capacitor.

[0068] Embodiment five:

[0069] This embodiment provides a method for producing a dry DC capacitor, the method comprising:

[0070] 1) Winding: Wind the core together to ensure uniform and stable tension to prevent the film from shifting or loosening.

[0071] 2) Heat treatment: Sterilization and impurity removal are carried out through heat treatment process. This step has a direct impact on the quality of capacitors, and appropriate temperature needs to be controlled to maintain product quality.

[0072] 3) Gold spraying: A metal layer is sprayed on both ends of the core inside the capacitor. Usually, a low-melting-point gold spraying material is used. After drying, filtering and other process treatments, this is related to the capacitor's ability to withstand wear.

[0073] 4) Welding: Weld the capacitor metallized film, core and other components together. Arc spraying and flame spraying are two process technologies. The latter can effectively improve the anti-surge capability of the power capacitor itself and reduce the contact loss of the capacitor.

[0074] 5) Withstand voltage test: A semi-inspection is carried out before the capacitor is completed to assess the manufacturing level of the capacitor and the insulation performance of the metallized film.

[0075] 6) Life test: Perform regular life simulation tests on capacitors to detect product quality under high temperature and high pressure; adjust the dry DC capacitors according to the test method of a round element film and a film on-machine winding pressure in the above-mentioned embodiment 1.

[0076] 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, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the pressure of a circular element film and a film on a machine, characterized in that: The test method includes: Step S1: Select a flexible pressure sensor with a measuring range of more than 50 kg, and place a cushion block in the middle of the effective area of ​​the sensor; Step S2: Select a metallized winding film with a thickness of 4 μm to 10 μm, put the winding film 1 and the film 2 on the material shaft of the winder, set the tension of the winder, and first wind about 20 to 30 turns to obtain the diameter Dn of the nth round element; Step S3: the winding machine stops, and the flexible pressure sensor is quickly placed on the middle plane of the component. After the sensor is placed, the winding machine continues to be wound down. When the winding machine is wound for more than 200 turns, the machine is stopped, and the sensor reader is quickly connected to the sensor to read the pressure value on the sensor at this time. Step S4: Repeat the operations of steps S1 to S3 on the same winding machine mandrel to verify the pressure values ​​under different numbers of turns, and convert the obtained pressure values ​​into pressure intensity; Step S5: Using the known parameters measured, The pressure between the membrane layers is calculated by the formula and compared with the measured pressure to determine the difference coefficient K between the calculated pressure and the measured pressure under the same winding mandrel; where P n-N ——Pressure between the nth film layers inside the circular element, MPa; T d ——winding tension, N; r0——radius of the mandrel, mm; d——thickness of the metallized film, mm; b——width of the metallized film, mm; D=d0+4Nd——outer diameter of the component, mm; D n =d0+4nd——the diameter of the nth circle of the circular element, mm, where d0 is the core rod diameter, mm; Step S6: Replace the winding machine mandrel, repeat the operations of the above steps S1 to S5, and finally obtain the measured value and calculated value correction coefficient K of the pressure between the film layers under different mandrels.

2. The method for testing the pressure of the circular element film and the film on the machine winding according to claim 1, characterized in that: The thickness of the pad placed in the middle of the sensor effective area in step S1 is 1 mm to 4 mm.

3. The method for testing the circular element film and the film on-machine winding pressure according to claim 1, characterized in that: The specific steps of step S2 are to select a metallized winding film with a thickness of 4 μm to 10 μm, put the winding film 1 and the film 2 on the winding machine material shaft, put the ends of the two films on the winding machine core shaft, and set the tension T of the winding machine. d , set the value between 300CN and 1000CN, first wind 20 to 30 turns, and get the diameter Dn of the nth turn of the circular element.

4. The method for testing the circular element film and the film on-machine winding pressure according to claim 1, characterized in that: The core shaft of the winding machine in the steps S1 to S6 needs to select a suitable core shaft diameter of the winding machine. Due to the matching problem between the size of the pressure sensor and the diameter of the core shaft of the winding machine, the pressure sensor is planar and the core shaft is round, and there will be problems in matching the two. It is necessary to determine whether the bending of the pressure-sensitive area has an impact on the measurement results. In order to reduce the impact of this factor, the size of the sensor should be as small as possible and the core shaft diameter should be as large as possible.

5. The method for testing the circular element film and the film on-machine winding pressure according to claim 1, characterized in that: The effective area of ​​the pressure sensor in step S3 has a protective frame, which has a great influence on the force on the sensor. However, the pressure sensor is to be inserted as a whole between the membrane layers of the component, and a way is needed to make the effective area of ​​the sensor bear force. There are two ways to do this: one is to re-customize the lead wires and remove the protective frame; the other is to add gaskets to ensure that the effective area of ​​the sensor is subjected to force under a controlled state. The modified sensor needs to be recalibrated.

6. The method for testing the circular element film and the film on-machine winding pressure according to claim 1, characterized in that: After the winding is completed in step S3, the pressure test data should be read quickly. Due to inertia, the winding tension will slowly decrease and the component winding diameter will also slowly increase, so the test should be performed as quickly as possible to reduce the deviation of the measurement results.

7. A method for improving the operating safety and service life of a dry DC capacitor, characterized in that: The method is a method for testing the circular element film and the film on-machine winding pressure according to any one of claims 1-6.

8. The method according to claim 7, characterized in that: The method specifically adjusts the pressure between the corresponding element membrane layers by adjusting the relevant parameters of the winding, thereby improving the element self-healing energy and extending the service life of the dry DC capacitor by adjusting the interlayer pressure of the membrane.

9. A dry DC capacitor, characterized in that: The production process of the dry DC capacitor adopts a method for testing the circular element film and the film winding pressure in a machine as described in any one of claims 1 to 6.

10. A method for producing a dry DC capacitor, characterized in that: The method includes winding, heat treatment, gold spraying, welding, pressure resistance test, and life test; wherein the life test adopts a method for testing the circular element film and the film in-machine winding pressure as described in any one of claims 1 to 6.

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