Method for testing center temperature of a metallized film capacitor

Abstract

This application relates to the field of electronic component testing and provides a method for testing the center temperature of a metallized film capacitor. The method includes: pre-treating the thermocouple wire tip by stripping the thermocouple wire tip to a predetermined length, exposing two alloy wires that are twisted and tightened together; immersing the two tightened alloy wires in molten solder to secure the connection; placing the calibrated thermocouple wire tip into the center diameter hole of the capacitor core at a predetermined depth; sequentially performing hot pressing, gold spraying, welding, assembly, and encapsulation processes on the capacitor core with the thermocouple wire tip placed; connecting the encapsulated capacitor to a fixture connected to a test power supply and placing it in a sealed box; applying a rated load to the capacitor through the test power supply; collecting temperature data at the center of the capacitor within a predetermined time period and plotting a temperature change curve. This method solves the problem of thermocouple wires scratching the metallized film of the core in traditional direct testing methods, significantly improving the pass rate of test samples and the validity of test results.

Description

Technical Field

[0001] This application relates to the field of electronic component testing technology, and in particular to a method for testing the center temperature of a metallized thin-film capacitor. Background Technology

[0002] Metallized film capacitors are capacitors that use plastic film as the dielectric and metallized coating as the electrodes. They have advantages such as small size, large capacitance, low loss, and good self-healing properties. They are widely used in commercial electronics, industrial control, solar power generation, energy storage devices, wind power generation, and new energy electric vehicles and hybrid vehicles. As a key component in power conversion circuits, they are mainly used to filter out ripple current.

[0003] The lifespan of metallized film capacitors is closely related to their operating environment temperature and the core temperature generated by their own heat generation. The higher the core temperature, the faster the capacitor ages and the shorter its lifespan. To ensure the reliability and lifespan of metallized film capacitors in practical applications, power supply manufacturers must conduct individual unit verification and system-wide verification during the capacitor introduction phase. This involves testing the core temperature of the capacitor under extreme ambient temperature and extreme load conditions to determine whether it meets the design life requirements.

[0004] Currently, the industry primarily uses indirect testing methods to measure the temperature of metallized film capacitors. This involves measuring the ambient temperature and surface temperature of the capacitor separately, and then calculating the center temperature based on empirical formulas and temperature rise data. This method has significant drawbacks: firstly, ambient temperature measurement is easily affected by factors such as airflow and equipment heat dissipation, resulting in low accuracy; secondly, the temperature distribution on the capacitor surface is uneven, making it difficult to accurately detect the hottest spots. Furthermore, the correlation between surface temperature and center temperature varies considerably for capacitors of different structures and capacities, leading to large errors in the calculated center temperature and failing to accurately reflect the actual operating temperature of the capacitor. Summary of the Invention

[0005] This application provides a method for testing the center temperature of metallized film capacitors, aiming to solve the problem that the current industry mainly uses indirect testing methods to test the temperature of metallized film capacitors, which cannot truly reflect the actual operating temperature of the capacitor.

[0006] In a first aspect, embodiments of this application provide a method for testing the center temperature of a metallized thin-film capacitor, the method comprising: Pre-treat the thermocouple wire ends by stripping the thermocouple wire ends to a predetermined length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the twisted alloy wires in molten tin to make the two alloy wires firmly connected, and wrapping the alloy wires with high-temperature tape. The pre-treated thermocouple is placed in a constant temperature chamber for temperature calibration; a circular core is wound during capacitor winding, with a pre-drilled shaft diameter hole in the center of the core; the calibrated thermocouple wire ends are placed into the pre-set depth in the shaft diameter hole in the center of the core; the capacitor core with the thermocouple wire ends placed is subjected to hot pressing, gold spraying, welding, assembly and encapsulation processes in sequence, and the thermocouple wire ends are fixed by hot pressing. After the encapsulated capacitor is connected to the fixture for the test power supply, it is placed in a sealed box. The sealed box is then placed in a pre-set temperature drying oven. The rated load is applied to the capacitor through the test power supply. Once the ambient temperature of the capacitor reaches the preset value, the temperature data of the center of the capacitor is collected within a preset time period, and a temperature change curve is plotted based on the collected temperature data.

[0007] In some embodiments, the step of stripping the thermocouple wire end to a predetermined length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the twisted alloy wires in molten solder to secure the connection, and wrapping the alloy wires with high-temperature tape includes: using a wire stripper to strip two millimeters of the thermocouple wire end to expose two complete alloy wires; twisting the two alloy wires together at least three times in the same direction and tightening them; immersing the ends of the tightened alloy wires in molten solder for one to two seconds to fully connect the two alloy wires through solder; and completely covering the alloy wire connection area with high-temperature tape made of high-temperature resistant insulating glass cloth, wrapping only one loop.

[0008] In some embodiments, applying a rated load to the capacitor via a test power supply includes: the test power supply outputting power to the capacitor according to a preset rated operating voltage, rated effective current, and rated ripple frequency; the test power supply acquiring the capacitor's operating voltage and current data in real time, and dynamically adjusting the output parameters based on the acquired operating voltage and current data to ensure that the capacitor always operates under rated load conditions.

[0009] In some embodiments, the step of collecting temperature data at the center of the capacitor within a preset time period after the ambient temperature of the capacitor reaches a preset value, and plotting a temperature change curve based on the collected temperature data, includes: continuously collecting temperature data at the center of the capacitor after the ambient temperature of the capacitor reaches the preset value and remains stable; performing moving average filtering and noise reduction processing on the collected raw temperature data to identify the thermal equilibrium point of the temperature data; calculating the average value of the temperature data after collecting the thermal equilibrium point as the final center temperature value; and plotting a temperature change curve with time as the horizontal axis and temperature as the vertical axis.

[0010] In some embodiments, the step of placing the pre-treated thermocouples into a constant temperature chamber for temperature calibration includes: simultaneously placing multiple pre-treated thermocouples in the same position inside the constant temperature chamber; sequentially setting three different calibration temperature points in the constant temperature chamber; collecting the output data of each thermocouple after maintaining a stable position at each calibration temperature point for a preset time; calculating the error value of each thermocouple at each temperature point; and generating a temperature error compensation curve corresponding to each thermocouple based on the error value of each thermocouple at each temperature point, so as to correct the collected temperature data according to the corresponding temperature error compensation curve during the test.

[0011] In some embodiments, the step of winding a circular core during capacitor winding, with a pre-drilled shaft diameter hole at the center of the core, includes: using a winding machine to wind a circular core according to a preset film thickness and core diameter; detecting the roundness of the core and the inner diameter of the shaft diameter hole in real time during the winding process; and adjusting the tension and rotation speed parameters of the winding machine when the roundness or inner diameter exceeds a preset range, so that the centerness and dimensional accuracy of the shaft diameter hole meet the requirements.

[0012] In some embodiments, inserting the calibrated thermocouple wire tip into the central bore of the core at a predetermined depth includes: using a displacement sensor to detect the insertion depth of the thermocouple wire tip, stopping the insertion when the insertion depth reaches a predetermined range of the total depth of the bore, and using a visual inspection device to confirm that the thermocouple wire tip is located at the central axis position of the bore.

[0013] In some embodiments, the process of hot pressing, gold spraying, welding, assembly, and encapsulation is performed sequentially on the capacitor core with the thermocouple wire head placed therein. The process of fixing the thermocouple wire head by hot pressing includes: hot pressing the capacitor core according to preset hot pressing temperature and pressure parameters; monitoring the temperature and pressure of the hot pressing head in real time during the hot pressing process; ending the hot pressing when the temperature and pressure reach preset values ​​and are maintained for a preset time, so that the thermocouple wire head is tightly bonded to the core without damaging the core film; and then completing the processes of gold spraying, welding, assembly, and encapsulation sequentially.

[0014] In some embodiments, the step of connecting the encapsulated capacitor to the fixture connected to the test power supply and then placing it into a sealed box includes: firmly connecting the two electrodes of the capacitor to the two conductive terminals of the fixture respectively; confirming the continuity between the capacitor and the fixture through a continuity detection device; placing the capacitor and the fixture as a whole into a fixed position inside the sealed box; closing the lid of the sealed box and performing an airtightness test to ensure that the inside of the sealed box is completely isolated from the outside air.

[0015] In some embodiments, placing the sealed box entirely into a preheated drying oven at a preset temperature includes: preheating the drying oven to a preset temperature and maintaining the temperature for a preset stable time, placing the sealed box stably in the center of the drying oven to ensure uniform air temperature around the sealed box, and closing the door of the drying oven.

[0016] This application employs a standardized pretreatment process involving wrapping, tinning, and high-temperature tape wrapping of thermocouple wire ends. This process ensures smooth, burr-free thermocouple wire ends, completely resolving the problem of thermocouple wires scratching the metallized film of the core in traditional direct testing methods. This significantly improves the pass rate of test samples and the validity of test results.

[0017] By directly measuring the center temperature by embedding a thermocouple into the central bore of the capacitor core, the inherent error caused by estimating the center temperature from the surface temperature in indirect testing methods is completely avoided, and the test results can truly reflect the actual operating temperature of the capacitor.

[0018] By placing the capacitor in a sealed enclosure and then into a forced-air drying oven, the sealed enclosure completely isolates the capacitor from the airflow of the drying oven, keeping it in a static, constant-temperature environment. This eliminates the influence of forced-airflow on the capacitor's temperature, ensuring the accuracy and reproducibility of the test data. A complete testing process is provided, from thermocouple calibration, core preparation, and thermocouple fixing to data acquisition and curve plotting. The operation is highly standardized and repeatable. By plotting temperature change curves, the trend of the capacitor's center temperature can be visually observed, facilitating rapid assessment of the capacitor's thermal performance and lifespan.

[0019] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic flowchart illustrating the steps of a method for testing the center temperature of a metallized thin-film capacitor according to an embodiment of this application; Figure 2 This is a schematic block diagram of a metallized thin-film capacitor center temperature testing system provided in one embodiment of this application; Figure 3 This is a schematic block diagram of a metallized thin-film capacitor center temperature testing device provided in one embodiment of this application; Figure 4 This is a schematic block diagram of the structure of a computer device provided in an embodiment of this application.

[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0025] It should be understood that, in order to clearly describe the technical solutions of the embodiments of the present invention, the terms "first" and "second" are used in the embodiments of the present invention to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.

[0026] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0028] Metallized film capacitors are capacitors that use plastic film as the dielectric and metallized coating as the electrodes. They have advantages such as small size, large capacitance, low loss, and good self-healing properties. They are widely used in commercial electronics, industrial control, solar power generation, energy storage devices, wind power generation, and new energy electric vehicles and hybrid vehicles. As a key component in power conversion circuits, they are mainly used to filter out ripple current.

[0029] The lifespan of metallized film capacitors is closely related to their operating environment temperature and the core temperature generated by their own heat generation. The higher the core temperature, the faster the capacitor ages and the shorter its lifespan. To ensure the reliability and lifespan of metallized film capacitors in practical applications, power supply manufacturers must conduct individual unit verification and system-wide verification during the capacitor introduction phase. This involves testing the core temperature of the capacitor under extreme ambient temperature and extreme load conditions to determine whether it meets the design life requirements.

[0030] Currently, the industry mainly uses two methods to test the temperature of metallized film capacitors. The first method is the indirect testing method, which involves measuring the ambient temperature and surface temperature of the capacitor separately, and then calculating the center temperature of the capacitor based on empirical formulas and temperature rise data. This method has obvious drawbacks: on the one hand, the detection of ambient temperature is easily affected by factors such as airflow and equipment heat dissipation in the test environment, resulting in low detection accuracy; on the other hand, the temperature distribution on the capacitor surface is uneven, and it is usually impossible to accurately detect the hottest spot on the surface. Furthermore, the correlation between surface temperature and center temperature varies greatly for capacitors of different structures and capacities, leading to a large error in the calculated center temperature, which cannot truly reflect the actual operating temperature of the capacitor.

[0031] The second method is the direct testing method, which involves inserting the thermocouple directly into the center of the capacitor for temperature measurement. While this method can directly measure the center temperature, it still has several problems in practical applications: First, the thermocouple wire ends are usually used directly without special pretreatment. The exposed metal wire ends are sharp and burr-like, which can easily scratch the metallized film of the core during insertion and subsequent processing, leading to short circuits, leakage, and other faults in the capacitor, damaging the test sample and affecting the validity of the test results. Second, during testing, the capacitor is usually placed directly in a forced-air drying oven. The motor inside the oven drives the air circulation, which continuously removes heat from the capacitor surface, causing the capacitor's temperature to be lower than its actual operating temperature in a static, windless environment. This results in a lower-than-expected center temperature reading and a significant device error.

[0032] In the existing technology, some solutions only make partial improvements to one of the above problems. For example, they only wrap the thermocouple with simple insulation or only optimize the temperature control accuracy of the drying oven. However, none of them can solve the two core problems of thermocouple scratching film and wind interference with temperature testing at the same time. They cannot fundamentally improve the accuracy and reliability of the center temperature test of metallized film capacitors.

[0033] To solve the above problem, please refer to Figure 1 This application provides a method for testing the center temperature of a metallized thin-film capacitor, applicable to applications such as... Figure 2 The system shown is for testing the center temperature of a metallized film capacitor. Figure 2 As shown, the provided metallized film capacitor center temperature testing system includes a film capacitor 1, a thermocouple 2, a forced-air drying oven 3, a test power supply 4, a temperature measuring instrument 5, a fixture 6, and a sealed box 7.

[0034] The provided method for testing the center temperature of a metallized film capacitor includes steps S101 to S103. Details are as follows: Step S101. Pre-treat the thermocouple wire ends by stripping the thermocouple wire ends to a predetermined length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the two twisted alloy wires in molten tin to make the two alloy wires firmly connected, and wrapping the alloy wires with high-temperature tape.

[0035] Specifically, this step eliminates sharp burrs and exposed metal edges on the thermocouple wire ends through standardized processing, fundamentally solving the problem of short circuits and leakage in capacitors caused by thermocouples scratching the metallized film of the core in traditional testing.

[0036] Prepare the following: wire strippers with an accuracy of 0.1mm, a constant temperature solder pot with a temperature control accuracy of ±5℃, anti-static tweezers, stainless steel scissors, lint-free cloth, K-type thermocouple wire (0.3mm-3.2mm in diameter), lead-free solder wire (Sn99.3Cu0.7), high-temperature resistant insulating glass cloth tape (10mm wide, 0.13mm thick) with a temperature resistance of ≥200℃, and anhydrous ethanol.

[0037] For example, the operation process corresponding to this step may include: (1) Cleaning the wire ends: Wipe the insulation sheath of the thermocouple wire ends for 5cm length with a lint-free cloth soaked in anhydrous ethanol to remove surface oil and dust.

[0038] (2) Precise stripping: Use wire strippers to precisely strip 2mm of the insulation outer sheath at the end of the thermocouple wire, exposing only the two parallel alloy wires inside. Do not scratch or cut the alloy wires. After stripping, use tweezers to gently align the two alloy wires.

[0039] (3) Alloy wire winding: Use tweezers to tightly wind the two alloy wires clockwise at least 3 times, with uniform winding spacing. After winding, cut off the excess alloy wire ends, leaving only a 1mm long connector, and ensure that the connector is free of forks and burrs.

[0040] (4) Soldering reinforcement: Preheat the constant temperature solder furnace to 240°C. After the molten solder is completely melted and there is no oxide layer on the surface, vertically immerse the end of the wound alloy wire into the molten solder for 1 mm to 1.5 mm for 1 to 2 seconds, so that the solder completely wets and wraps the connection part of the alloy wire, forming a smooth spherical solder joint with a diameter of about 1.5 mm. After taking it out, let it cool naturally to room temperature.

[0041] (5) Insulation wrapping: Cut a piece of high-temperature tape about 5mm long and wrap it tightly around the connection part of the alloy wire to ensure that the tape completely covers the solder joint and all exposed alloy wires. When wrapping, align the two ends of the tape, and ensure that there are no wrinkles, no bubbles, and no overlaps to avoid the wire ends being too thick and affecting the subsequent insertion of the core shaft diameter hole.

[0042] After pretreatment, observe the thermocouple wire ends with a magnifying glass to confirm that the solder joints are smooth, without burrs or incomplete soldering, and that the high-temperature tape is completely wrapped without any exposed metal. Gently pull the thermocouple wires by hand to confirm that the alloy wire connection is firm and not loose.

[0043] Step S102. Place the pretreated thermocouple in a constant temperature chamber for temperature calibration; when winding the capacitor, roll a circular core and leave a shaft diameter hole in the center of the core; place the calibrated thermocouple wire end into the shaft diameter hole in the center of the core at a preset depth; perform hot pressing, gold spraying, welding, assembly and packaging processes on the capacitor core with the thermocouple wire end placed in it in sequence, and fix the thermocouple wire end by hot pressing.

[0044] Specifically, this step achieves accurate calibration of the thermocouple and precise and reliable fixation inside the capacitor core, ensuring the accuracy of the test position and the consistency of the test results.

[0045] For example, thermocouple temperature calibration may include: (1) Preparation of calibration equipment: Prepare a standard constant temperature chamber with an accuracy class of 0.01, a standard platinum resistance thermometer with an accuracy of ±0.05℃, and a data acquisition device.

[0046] (2) Setting up the calibration environment: Place all the pre-processed thermocouples and standard platinum resistance thermometers into the same calibration platform inside the standard constant temperature chamber, ensuring that the measuring ends of all thermocouples and the measuring ends of the standard platinum resistance thermometers are on the same horizontal plane and that there is no obstruction between them.

[0047] (3) Multi-temperature point calibration: Set the constant temperature chamber to three calibration temperature points of 25℃, 85℃ and 125℃ in sequence; at each temperature point, after the temperature of the constant temperature chamber is kept stable for 30 minutes, collect the output data of all thermocouples and standard platinum resistance thermometers at the same time. Collect 10 sets of data at each temperature point, with a 1-minute interval between each set of data.

[0048] (4) Error calculation and compensation: Calculate the average measurement value of each thermocouple at each temperature point, compare it with the measurement value of the standard platinum resistance thermometer, and obtain the error value of each thermocouple at each temperature point; use the least squares method to linearly fit the error value, generate the temperature error compensation curve corresponding to each thermocouple, and import the compensation curve into the control system of the temperature measuring instrument 5 for real-time correction of subsequent test data.

[0049] For example, the fabrication of the circular capacitor core and the pre-drilling of the shaft diameter hole may include: (1) Winding machine parameter settings: Start the fully automatic capacitor winding machine and input the core diameter, film width, number of metallized film layers, initial winding tension of 0.2N, and winding speed of 3000 rpm in the control system.

[0050] (2) Real-time monitoring of the winding process: The laser displacement sensor built into the winding machine detects the outer roundness of the core and the inner diameter of the central shaft hole in real time at a frequency of 50Hz; when the core roundness error is detected to be greater than 0.2mm or the inner diameter error of the shaft hole is greater than 0.1mm, the control system automatically adjusts the winding tension (adjustment step 0.1N) and the spindle speed (adjustment step 1 rpm) until the dimensions meet the requirements.

[0051] (3) Winding completed: When the number of winding turns reaches the preset value, the winding machine automatically cuts the metallized film, fixes the end of the core with tape, and takes out the rolled round core.

[0052] For example, thermocouple mounting and securing may include: (1) Precise insertion and positioning: Fix the calibrated thermocouple 2 on an electric displacement stage with a positioning accuracy of 0.01mm, fix the capacitor core on a special fixture, and align the core's central shaft diameter hole with the thermocouple wire head coaxially; start the electric displacement stage to slowly insert the thermocouple wire head into the core's central shaft diameter hole, and the displacement sensor detects the insertion depth in real time; when the insertion depth reaches 45%-55% of the total depth of the shaft diameter hole, the electric displacement stage automatically stops moving; start the industrial camera located above the shaft diameter hole to take an image of the inside of the shaft diameter hole, and use an image recognition algorithm to confirm that the thermocouple wire head is located on the central axis of the shaft diameter hole. If there is any offset, fine-tune the X and Y axis positions of the electric displacement stage to correct it.

[0053] (2) Hot pressing fixation: Place the core with the thermocouple installed into the special mold of the hot press, ensuring that the core is placed flat and the thermocouple wire is led out from the reserved groove of the mold; set the hot pressing parameters as hot pressing temperature 100℃, hot pressing pressure 6MPa, and hot pressing time 240 seconds; start the hot press, and monitor the temperature and pressure of the hot press head in real time during the hot pressing process. When the temperature and pressure reach the preset value, start timing; after the timing ends, the hot press automatically lifts the hot press head, takes out the core, and gently pulls the thermocouple wire to confirm that the thermocouple wire end is tightly connected to the core without loosening.

[0054] (3) Subsequent capacitor processing: In accordance with the standard metallized film capacitor production process, the hot-pressed core is sequentially subjected to end face gold spraying, electrode lead welding, plastic shell assembly and epoxy resin potting process. During potting, epoxy resin is prevented from entering the shaft diameter hole and affecting thermocouple measurement.

[0055] Step S103. After connecting the encapsulated capacitor to the fixture connected to the test power supply, place it in a sealed box; place the entire sealed box in a pre-set temperature drying oven; apply the rated load to the capacitor through the test power supply; after the ambient temperature of the capacitor reaches the preset value, collect the temperature data of the center of the capacitor within a preset time period, and plot the temperature change curve based on the collected temperature data.

[0056] Specifically, this step isolates the airflow of the drying oven from the airflow through a sealed box, creating a static constant temperature testing environment for the capacitor, enabling accurate measurement and intuitive presentation of the capacitor's center temperature.

[0057] For example, the test system connection may include: (1) Connecting the capacitor to the fixture: Place the prepared thin film capacitor 1 with built-in thermocouple on the test fixture 6, and connect the two electrodes of the capacitor to the positive and negative elastic conductive terminals of the fixture respectively; start the continuity detection device to detect the continuity resistance between the capacitor and the fixture. The continuity resistance should be less than 10mΩ. If the continuity is poor, re-polish the electrode surface or replace the fixture terminals.

[0058] (2) Temperature measurement system connection: Connect the other end of thermocouple 2 to the corresponding input terminal of high-precision thermometer 5, and confirm that the thermometer 5 has imported the temperature error compensation curve of the thermocouple and that the connection is firm and not loose.

[0059] (3) Power system connection: Connect the power input line of the test fixture 6 to the output terminal of the programmable test power supply 4, strictly distinguishing between positive and negative terminals to avoid damaging the power supply by reversing the connection.

[0060] For example, sealing and testing environment settings may include: (1) Sealed box assembly: Place the connected capacitor and clamp into the insulating fixed bracket inside the sealed box 7, arrange the thermocouple wire and power line, lead the line out from the aviation sealing plug on the side of the sealed box, and tighten the locking nut of the aviation plug; close the box cover, and evenly tighten the 8 sealing bolts around the box cover to ensure that the sealing strip between the box cover and the box body is completely in place.

[0061] (2) Air tightness test: Start the air tightness tester and introduce dry compressed air at a pressure of 0.05MPa into the box through the air inlet of the sealed box. Hold the pressure for 5 minutes. If the pressure drop is less than 0.001MPa, the air tightness of the sealed box is qualified.

[0062] (3) Preheating of the drying oven: Start the drying oven 3, set the preset test environment temperature, turn on the blower function to circulate the air inside the oven, and after the temperature of the drying oven reaches the preset value, continue to keep the temperature stable for at least 30 minutes to ensure that the temperature of each point inside the drying oven is uniform.

[0063] (4) Placement of the sealed box: Open the door of the blower drying oven and place the sealed box 7 stably on the center shelf inside the drying oven, so that the distance between the sealed box and the inner wall of the drying oven is greater than 10cm, ensuring that the air circulation around the sealed box is uniform, and close the door of the drying oven.

[0064] For example, load application and data acquisition and analysis may include: (1) Applying rated load: Start the programmable test power supply 4, and preset the rated working voltage, rated effective current and rated ripple frequency parameters of the capacitor in the control system; the test power supply outputs power to the capacitor in a soft start mode, and the built-in voltage sensor and current sensor collect the working voltage and working current data of the capacitor in real time at a sampling frequency of 100Hz; the control system dynamically adjusts the power supply output parameters through the PID algorithm so that the capacitor always works in the rated load state, monitors the working status of the capacitor in real time, and immediately cuts off the power supply output and issues an alarm signal if overvoltage, overcurrent or overheating occurs.

[0065] (2) Temperature data acquisition: When the thermometer 5 detects that the ambient temperature inside the sealed box 7 has reached the preset value and remains stable, the data acquisition program is started to continuously acquire the temperature data of the center of the capacitor within 6 hours at a sampling frequency of 1Hz; during the data acquisition process, the temperature change curve is displayed in real time, and the maximum, minimum and real-time values ​​of the temperature are recorded.

[0066] (3) Data processing and result output: After the data acquisition is completed, the system automatically performs a moving average filter with a window size of 5 on the original temperature data to remove random noise and interference signals; by calculating the standard deviation of the temperature data within 10 consecutive minutes, when the standard deviation is less than 1℃, the capacitor is determined to have reached thermal equilibrium, and this moment is recorded as the thermal equilibrium point; the temperature data for 1 consecutive hour after the thermal equilibrium point is collected, and its arithmetic mean is calculated as the final center temperature value of the capacitor; a continuous curve of temperature changing with time is plotted with time as the horizontal axis and temperature as the vertical axis, and the thermal equilibrium point and the final center temperature value are marked on the curve to generate a test report.

[0067] In some embodiments, the step of stripping the thermocouple wire end to a predetermined length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the twisted alloy wires in molten solder to secure the connection, and wrapping the alloy wires with high-temperature tape includes: using a wire stripper to strip two millimeters of the thermocouple wire end to expose two complete alloy wires; twisting the two alloy wires together at least three times in the same direction and tightening them; immersing the ends of the tightened alloy wires in molten solder for one to two seconds to fully connect the two alloy wires through solder; and completely covering the alloy wire connection area with high-temperature tape made of high-temperature resistant insulating glass cloth, wrapping only one loop.

[0068] This embodiment further defines the thermocouple wire pretreatment step described in step S101 by preparing wire strippers with an accuracy of 0.1mm, a constant temperature soldering furnace with a temperature control accuracy of ±5℃, anti-static tweezers, stainless steel scissors, lint-free cloth, K-type thermocouple wire (0.3mm-3.2mm in diameter), lead-free solder wire (Sn99.3Cu0.7), high-temperature insulating glass cloth (temperature resistance ≥200℃, width 10mm, thickness 0.13mm), and anhydrous ethanol.

[0069] For example, the process corresponding to this embodiment may include: (1) Use a wire stripper to strip two millimeters of the thermocouple wire end to expose two complete alloy wires. Ensure that there is no residue of the insulation sheath and that the alloy wires are free from scratches and breaks. After stripping, gently align the two alloy wires with tweezers.

[0070] (2) Wrap the two alloy wires together at least three times in a clockwise direction and tighten them. The wrapping spacing should be uniform. After wrapping, use stainless steel scissors to cut off the excess alloy wire ends, leaving only a 1mm long connector. Ensure that the connector is free of forks and burrs.

[0071] (3) Preheat the constant temperature tin furnace to 240°C. After the tin liquid is completely melted and there is no oxide layer on the surface, vertically immerse the end of the tightened alloy wire into the molten tin liquid for one to two seconds, so that the two alloy wires are completely connected by solder to form a smooth spherical solder joint with a diameter of about 1.5 mm. After taking it out, let it cool naturally to room temperature.

[0072] (4) Cut a piece of high-temperature resistant insulating glass cloth about 5mm long, completely cover the alloy wire connection part and wrap it only once. When wrapping, align the two ends of the tape, without wrinkles, bubbles or overlap, to avoid the wire ends being too thick and affecting the subsequent insertion of the core shaft diameter hole.

[0073] After pretreatment, observe the thermocouple wire ends with a 10x magnifying glass to confirm that the solder joints are smooth and free of burrs, incomplete soldering, and false soldering, and that the high-temperature tape is completely wrapped with no exposed metal; gently pull the thermocouple wires by hand to confirm that the alloy wire connection is firm and not loose.

[0074] In some embodiments, applying a rated load to the capacitor via a test power supply includes: the test power supply outputting power to the capacitor according to a preset rated operating voltage, rated effective current, and rated ripple frequency; the test power supply acquiring the capacitor's operating voltage and current data in real time, and dynamically adjusting the output parameters based on the acquired operating voltage and current data to ensure that the capacitor always operates under rated load conditions.

[0075] This embodiment further defines the step of applying a rated load to the capacitor through a test power supply as described in step S103. A programmable AC test power supply 4 is prepared, with an output voltage range of 0V-1000V, an output current range of 0A-100A, and an output frequency range of 50Hz-100kHz. It has a built-in high-precision voltage sensor and current sensor, and a sampling frequency of not less than 100Hz.

[0076] For example, the process corresponding to this embodiment may include: (1) In the control system of the test power supply 4, preset the rated operating voltage, rated effective current and rated ripple frequency parameters of the capacitor under test.

[0077] (2) Test power supply 4 outputs power to the capacitor in soft start mode. The soft start time is set to 10 seconds to avoid damage to the capacitor by inrush current.

[0078] (3) Test power supply 4 collects the working voltage and working current data of the capacitor in real time, with a sampling frequency of 100Hz.

[0079] (4) The control system of the test power supply 4 compares the collected working voltage and working current data with the preset rated parameters, calculates the deviation value, and dynamically adjusts the output voltage and output current parameters through the PID control algorithm so that the capacitor always works under rated load.

[0080] (5) Test power supply 4 monitors the working status of the capacitor in real time. When abnormal conditions such as overvoltage, overcurrent, overtemperature or short circuit occur, the power supply output is immediately cut off and an audible and visual alarm signal is issued.

[0081] In some embodiments, the step of collecting temperature data at the center of the capacitor within a preset time period after the ambient temperature of the capacitor reaches a preset value, and plotting a temperature change curve based on the collected temperature data, includes: continuously collecting temperature data at the center of the capacitor after the ambient temperature of the capacitor reaches the preset value and remains stable; performing moving average filtering and noise reduction processing on the collected raw temperature data to identify the thermal equilibrium point of the temperature data; calculating the average value of the temperature data after collecting the thermal equilibrium point as the final center temperature value; and plotting a temperature change curve with time as the horizontal axis and temperature as the vertical axis.

[0082] This embodiment further defines the step of collecting temperature data and plotting temperature change curves described in step S103 by preparing a high-precision thermometer 5 with a temperature measurement range of -200℃ to 200℃, a temperature measurement accuracy of ±0.1℃, a sampling frequency of not less than 1Hz, and built-in data processing and curve plotting functions.

[0083] For example, the process corresponding to this embodiment may include: (1) When the thermometer 5 detects that the ambient temperature inside the sealed box 7 has reached the preset value and remains stable, the data acquisition program is started.

[0084] (2) Continuously collect temperature data at the center of the capacitor at a sampling frequency of 1 Hz for a continuous collection time of 6 hours.

[0085] (3) Perform a moving average filter with a window size of 5 on the collected raw temperature data to remove random noise and interference signals, and obtain a smooth temperature data sequence.

[0086] (4) By calculating the standard deviation of temperature data over 10 consecutive minutes, when the standard deviation is less than 1℃, the capacitor is determined to have reached thermal equilibrium, and this moment is recorded as the thermal equilibrium point.

[0087] (5) Collect temperature data for one hour after the thermal equilibrium point and calculate the arithmetic mean as the final capacitor center temperature value.

[0088] (6) Plot a continuous temperature change curve with time as the horizontal axis and temperature as the vertical axis. Mark the thermal equilibrium point and the final center temperature value on the curve, and generate and save the test report.

[0089] In some embodiments, the step of placing the pre-treated thermocouples into a constant temperature chamber for temperature calibration includes: simultaneously placing multiple pre-treated thermocouples in the same position inside the constant temperature chamber; sequentially setting three different calibration temperature points in the constant temperature chamber; collecting the output data of each thermocouple after maintaining a stable position at each calibration temperature point for a preset time; calculating the error value of each thermocouple at each temperature point; and generating a temperature error compensation curve corresponding to each thermocouple based on the error value of each thermocouple at each temperature point, so as to correct the collected temperature data according to the corresponding temperature error compensation curve during the test.

[0090] This embodiment further defines the step S102, which involves placing the pre-treated thermocouple into a constant temperature chamber for temperature calibration, by preparing a standard constant temperature chamber with an accuracy class of 0.01, a standard platinum resistance thermometer with an accuracy of ±0.05℃, and a data acquisition device.

[0091] For example, the process corresponding to this embodiment may include: (1) Place the pre-treated thermocouples into the same calibration platform inside the constant temperature chamber at the same time, ensuring that the measuring ends of all thermocouples are on the same horizontal plane as the measuring ends of the standard platinum resistance thermometer, and that there is no obstruction between them.

[0092] (2) Set three different calibration temperature points in the constant temperature chamber in sequence: 25℃ (room temperature), 85℃ (common working temperature of capacitors) and 125℃ (limit working temperature of capacitors).

[0093] (3) At each calibration temperature point, after the temperature of the constant temperature chamber has been stable for 30 minutes, the output data of each thermocouple and the standard platinum resistance thermometer are collected simultaneously. Ten sets of data are collected continuously at each temperature point, with a 1-minute interval between each set of data.

[0094] (4) Calculate the average measurement value of each thermocouple at each temperature point, compare it with the measurement value of the standard platinum resistance thermometer, and obtain the error value of each thermocouple at each temperature point.

[0095] (5) The least squares method is used to linearly fit the error values ​​of each thermocouple at three temperature points to generate the temperature error compensation curve corresponding to each thermocouple.

[0096] (6) Import the temperature error compensation curve corresponding to each thermocouple into the control system of the temperature measuring instrument 5, and correct the collected temperature data in real time according to the corresponding temperature error compensation curve during subsequent testing.

[0097] In some embodiments, the step of winding a circular core during capacitor winding, with a pre-drilled shaft diameter hole at the center of the core, includes: using a winding machine to wind a circular core according to a preset film thickness and core diameter; detecting the roundness of the core and the inner diameter of the shaft diameter hole in real time during the winding process; and automatically adjusting the tension and speed parameters of the winding machine when the roundness or inner diameter exceeds a preset range, so that the centerness and dimensional accuracy of the shaft diameter hole meet the requirements.

[0098] This embodiment further defines the step S102, which involves winding a circular core during capacitor winding and reserving a shaft diameter hole in the center of the core. By preparing a fully automatic capacitor winding machine with a built-in laser displacement sensor and a detection accuracy of ±0.01mm, the roundness of the core and the inner diameter of the shaft diameter hole can be detected in real time.

[0099] For example, the process corresponding to this embodiment may include: (1) Input the preset core diameter, film width, number of metallized film layers, initial winding tension of 5N and winding speed of 100 rpm into the control system of the winding machine.

[0100] (2) Start the winding machine and wind the round core according to the preset parameters.

[0101] (3) During the winding process, the laser displacement sensor built into the winding machine detects the roundness of the core and the inner diameter of the shaft diameter hole in real time at a frequency of 50Hz.

[0102] (4) When the core roundness error is detected to be greater than 0.2 mm or the inner diameter error of the shaft diameter hole is greater than 0.1 mm, the control system automatically adjusts the tension and speed parameters of the winding machine. The tension adjustment step is 0.1 N and the speed adjustment step is 1 rpm, so that the centerness and dimensional accuracy of the shaft diameter hole meet the requirements.

[0103] (5) When the number of winding layers reaches the preset value, the winding machine automatically cuts the metallized film and automatically wraps 5 to 10 layers of light film around the outside, and then automatically heats the outside with a soldering iron.

[0104] In some embodiments, inserting the calibrated thermocouple wire tip into the central bore of the core at a predetermined depth includes: using a displacement sensor to detect the insertion depth of the thermocouple wire tip, stopping the insertion when the insertion depth reaches a predetermined range of the total depth of the bore, and using a visual inspection device to confirm that the thermocouple wire tip is located at the central axis position of the bore.

[0105] This embodiment further defines the step S102, which involves placing the calibrated thermocouple wire end into the core's central shaft diameter hole at a preset depth, by preparing an electric displacement stage (positioning accuracy ±0.01mm), an industrial camera (resolution ≥1.3 million pixels), an image processing system, and a dedicated core fixing fixture.

[0106] For example, the process corresponding to this embodiment may include: (1) Fix the calibrated thermocouple 2 on the electric displacement stage, fix the capacitor core on the special fixture, and align the core center diameter hole with the thermocouple wire end coaxially.

[0107] (2) Start the electric displacement stage to slowly insert the thermocouple wire head into the central shaft diameter hole of the core. The displacement sensor detects the insertion depth of the thermocouple wire head in real time.

[0108] (3) When the insertion depth reaches 45%-55% of the total depth of the shaft diameter hole, the electric displacement table will automatically stop insertion.

[0109] (4) Start the industrial camera located above the shaft diameter hole, take an image of the inside of the shaft diameter hole, and transmit the image to the image processing system.

[0110] (5) The image processing system detects the position of the thermocouple wire head through the image recognition algorithm and confirms that the thermocouple wire head is located at the central axis position of the shaft diameter hole; if the thermocouple wire head is detected to be deviating from the central axis, the control system automatically fine-tunes the X and Y axis positions of the electric displacement stage to adjust the thermocouple wire head to the central axis position.

[0111] In some embodiments, the process of hot pressing, gold spraying, welding, assembly, and encapsulation is performed sequentially on the capacitor core with the thermocouple wire head placed therein. The process of fixing the thermocouple wire head by hot pressing includes: hot pressing the capacitor core according to preset hot pressing temperature and pressure parameters; monitoring the temperature and pressure of the hot pressing head in real time during the hot pressing process; ending the hot pressing when the temperature and pressure reach preset values ​​and are maintained for a preset time, so that the thermocouple wire head is tightly bonded to the core without damaging the core film; and then completing the processes of gold spraying, welding, assembly, and encapsulation sequentially.

[0112] This embodiment describes the hot pressing, gold spraying, welding, assembly, and encapsulation processes for the capacitor core with the thermocouple wire ends placed in step S102. The hot pressing step for fixing the thermocouple wire ends is further defined by preparing a flat plate hot press (temperature control accuracy ±2℃, pressure control accuracy ±0.05MPa), a gold spraying machine, an ultrasonic welding machine, and a potting machine.

[0113] For example, the process corresponding to this embodiment may include: (1) Place the core with the thermocouple installed into the special mold of the hot press, ensuring that the core is placed flat and the thermocouple wire is led out from the reserved slot of the mold to avoid breaking the thermocouple wire during hot pressing.

[0114] (2) Set the preset hot pressing temperature to 100℃, hot pressing pressure to 6MPa and hot pressing time to 240 seconds in the control system of the hot press.

[0115] (3) Start the hot press. During the hot pressing process, monitor the temperature of the hot press head and the pressure applied to the core in real time. When the temperature and pressure reach the preset value and are maintained for the preset time, the hot pressing is ended.

[0116] (4) After hot pressing is completed, the hot press automatically lifts the hot pressing head, takes out the core, and gently pulls the thermocouple wire to confirm that the thermocouple wire head is tightly connected to the core and does not damage the core film.

[0117] (5) In accordance with the standard metallized film capacitor production process, the hot-pressed core is sequentially subjected to end face gold spraying, electrode lead welding, plastic shell assembly and epoxy resin potting process; during potting, attention should be paid to controlling the amount and flow rate of epoxy resin to avoid epoxy resin entering the shaft diameter hole and affecting thermocouple measurement.

[0118] In some embodiments, the step of connecting the encapsulated capacitor to the fixture connected to the test power supply and then placing it into a sealed box includes: firmly connecting the two electrodes of the capacitor to the two conductive terminals of the fixture respectively; confirming the continuity between the capacitor and the fixture through a continuity detection device; placing the capacitor and the fixture as a whole into a fixed position inside the sealed box; closing the lid of the sealed box and performing an airtightness test to ensure that the inside of the sealed box is completely isolated from the outside air.

[0119] This embodiment further defines the step S103, which involves connecting the encapsulated capacitor to the fixture connected to the test power supply and then placing it into the sealed box. This is achieved by preparing the test fixture 6, the continuity tester, the airtightness tester, and the stainless steel sealed box 7 (equipped with an aviation sealing plug and an air inlet).

[0120] For example, the process corresponding to this embodiment may include: (1) Securely connect the two electrodes of the capacitor to the two conductive terminals of the clamp 6 to ensure good contact.

[0121] (2) Start the continuity detection device to detect the continuity resistance between the capacitor and the clamp 6. The continuity resistance should be less than 10mΩ. If the continuity is poor, re-polish the surface of the capacitor electrode or replace the conductive terminal of the clamp until the continuity is normal.

[0122] (3) Place the capacitor and clamp 6 as a whole into the insulating fixed bracket inside the sealed box 7, arrange the thermocouple wires and power lines, lead the lines out from the aviation sealing plug on the side of the sealed box 7, tighten the locking nut of the aviation plug, and ensure good sealing.

[0123] (4) Close the lid of the sealed box 7 and tighten the 8 sealing bolts around the lid evenly to ensure that the silicone rubber sealing strip between the lid and the box body is fully attached.

[0124] (5) Start the air tightness tester and introduce dry compressed air at a pressure of 0.05MPa into the box through the air inlet of the sealed box 7 and maintain the pressure for 5 minutes; if the pressure drop is less than 0.001MPa, the air tightness of the sealed box 7 is qualified, ensuring that the inside of the sealed box 7 is completely isolated from the outside air.

[0125] In some embodiments, placing the sealed box entirely into a preheated drying oven at a preset temperature includes: preheating the drying oven to a preset temperature and maintaining the temperature for a preset stable time, placing the sealed box stably in the center of the drying oven to ensure uniform air temperature around the sealed box, and closing the door of the drying oven.

[0126] This embodiment further defines the step of placing the sealed box into a pre-set temperature drying oven as described in step S103. The drying oven 3 is prepared with a temperature control accuracy of ±1℃ and a temperature uniformity of ±2℃, and is equipped with multiple shelves inside.

[0127] For example, the process corresponding to this embodiment may include: (1) Start the blower drying oven 3, set the preset test environment temperature, and turn on the blower function to circulate the air inside the drying oven.

[0128] (2) Preheat the drying oven 3 to the preset temperature and keep the temperature stable for at least 30 minutes to ensure that the temperature of each point inside the drying oven is uniform.

[0129] (3) Open the door of the forced-air drying oven 3 and place the sealed box 7 stably on the central shelf inside the forced-air drying oven 3, so that the distance between the sealed box 7 and the inner wall of the drying oven is greater than 10cm, and ensure that the air temperature around the sealed box 7 is uniform.

[0130] (4) Close the door of the drying oven 3 and wait for 10 minutes. After confirming that the temperature inside the sealed box 7 has reached the preset value and remains stable through the ambient temperature sensor inside the sealed box 7, start applying load to the capacitor for testing.

[0131] like Figure 2 As shown, the metallized film capacitor center temperature testing system provided in this embodiment is used to implement the metallized film capacitor center temperature testing method described in any of the above embodiments. Figure 2 As shown, the system includes a thin-film capacitor 1, a thermocouple 2, a forced-air drying oven 3, a test power supply 4, a temperature measuring instrument 5, a fixture 6, and a sealed box 7. The specific structure, technical parameters, and functions of each component are as follows: Film capacitor 1 serves as the test sample, used to measure its center temperature under rated load and preset ambient temperature. Film capacitor 1 is a metallized film capacitor with a built-in thermocouple; its core is circular with a pre-drilled shaft diameter hole in the center. The measuring end of thermocouple 2 is fixed at a preset depth within the shaft diameter hole and tightly bonded to the core via a hot-pressing process. The capacitor is manufactured through a series of processes including gold spraying, welding, assembly, and epoxy resin potting. It is suitable for various metallized film capacitors with rated voltages of 100V-3000V and rated capacitances of 1nF-2000μF. During potting, epoxy resin must not enter the shaft diameter hole and must not affect the measurement accuracy of thermocouple 2.

[0132] Thermocouple 2 directly measures the center temperature inside the thin-film capacitor 1 and converts the temperature signal into an electrical signal, which is then transmitted to the temperature measuring instrument 5. Thermocouple 2 is a type K nickel-chromium / nickel-silicon thermocouple with a wire diameter of 0.3mm-3.2mm, a temperature range of -200℃ to 1300℃, and a long-term operating temperature not exceeding 1200℃. Its measuring end undergoes pre-treatment, as described in the above embodiment. The measuring end of thermocouple 2 is inserted into the central bore of the thin-film capacitor 1 to a depth of 45%-55% of the total depth of the bore, and is located at the central axis of the bore. The other end is connected to the input terminal of the temperature measuring instrument 5 via a high-temperature resistant wire.

[0133] The forced-air drying oven 3 provides a stable ambient temperature for testing, simulating the actual operating temperature of the film capacitor 1. The temperature control range of the forced-air drying oven 3 is room temperature to 200℃, with a temperature control accuracy of ±1℃ and a temperature uniformity of ±2℃. It is equipped with multi-layer stainless steel shelves, and the blower motor has a power of ≥100W, enabling forced air circulation within the oven. The oven body is made of stainless steel with a smooth, easy-to-clean inner wall. The door is equipped with a double-layered tempered glass observation window for easy observation of the internal conditions. The control system allows for preset temperature, heating rate, and holding time.

[0134] Test power supply 4 is used to apply rated load to film capacitor 1, simulating its operating state in an actual circuit. Test power supply 4 is a programmable AC test power supply with an output voltage range of 0V-1000V, an output current range of 0A-100A, and an output frequency range of 50Hz-100kHz. It has built-in high-precision voltage and current sensors with a sampling frequency of no less than 100Hz and features overvoltage, overcurrent, overtemperature, and short-circuit protection functions. Test power supply 4 can preset rated operating voltage, rated RMS current, and rated ripple frequency parameters; it can acquire the capacitor's operating voltage and current data in real time and dynamically adjust the output parameters through a PID control algorithm to ensure the capacitor always operates under rated load conditions.

[0135] The thermometer 5 receives the electrical signals transmitted by thermocouple 2, converts them into temperature data for display, storage, and processing, and plots temperature change curves. The thermometer 5 has a temperature measurement range of -200℃ to 200℃, a measurement accuracy of ±0.1℃, and a sampling frequency of no less than 1Hz. It supports simultaneous multi-channel measurement and can connect multiple thermocouples 2 simultaneously. It has a built-in data processing unit and a graphics display unit. The thermometer 5 can import the temperature error compensation curves of thermocouple 2 to correct the collected temperature data in real time. It can perform moving average filtering and noise reduction on the raw temperature data, automatically identify the thermal equilibrium point, and calculate the final center temperature value. It supports plotting temperature change curves with time as the x-axis and temperature as the y-axis and generates test reports.

[0136] The clamp 6 is used to fix the film capacitor 1 and realize the electrical connection between the film capacitor 1 and the test power supply 4. It is made of insulating, high-temperature resistant material and equipped with two flexible conductive terminals, which respectively contact the two electrodes of the film capacitor 1; the conductive terminals are gold-plated, and the contact resistance is less than 10mΩ; the bottom of the clamp has a fixing hole for fixing to a bracket inside the sealed box 7. An integrated continuity detection circuit can detect whether the connection between the film capacitor 1 and the clamp 6 is good, ensuring reliable electrical connection.

[0137] The sealed chamber 7 houses the film capacitor 1 and the clamp 6, completely isolating it from the airflow inside the forced-air drying oven 3, keeping the film capacitor 1 in a static, constant-temperature environment and eliminating the influence of forced-airflow on temperature testing. The sealed chamber 7 is made of stainless steel and has a sealed cubic structure; the lid and body are sealed with silicone rubber sealing strips, and eight sealing bolts are evenly distributed around the perimeter; an aviation-grade sealing plug is provided on the side for leading out thermocouple wires and power cords; an air inlet is provided for airtightness testing. The sealed chamber 7 exhibits excellent airtightness, maintaining pressure at 0.05 MPa for 5 minutes with a pressure drop of less than 0.001 MPa; it can withstand temperatures not lower than 150℃ and can be used long-term at the operating temperature of the forced-air drying oven 3.

[0138] A thin-film capacitor 1 is fixed to a clamp 6, with its two electrodes electrically connected to the two conductive terminals of the clamp 6. The measuring end of a thermocouple 2 is built into the center of the core of the thin-film capacitor 1, and its other end is connected to the input terminal of a thermometer 5 via a wire. The clamp 6 is connected to the output terminal of a test power supply 4 via a power cord, which provides power to the thin-film capacitor 1. The thin-film capacitor 1 and the clamp 6 are placed together on a fixed bracket inside a sealed enclosure 7, with the thermocouple wires and power cords leading out from an aviation-grade sealed plug on the side of the sealed enclosure 7. The sealed enclosure 7 is placed on a central shelf inside a forced-air drying oven 3, which provides a stable constant temperature environment for the sealed enclosure 7.

[0139] The test system is set up according to the above connection relationship. Check that all component connections are secure and electrical connections are normal. Start the forced-air drying oven 3, preheat to the preset test temperature and maintain stability for at least 30 minutes. Place the sealed box 7 smoothly into the center of the forced-air drying oven 3 and close the oven door. Start the test power supply 4 to apply the rated load to the film capacitor 1, causing the capacitor to start working and generate heat. Start the thermometer 5 to monitor the ambient temperature inside the sealed box 7 and the center temperature of the film capacitor 1 in real time. Once the ambient temperature inside the sealed box 7 reaches the preset value and remains stable, the thermometer 5 begins to continuously collect the temperature data of the center of the film capacitor 1. After data collection, the thermometer 5 automatically processes the temperature data, calculates the final center temperature value, plots the temperature change curve, and generates a test report. After the test, turn off the test power supply 4, the thermometer 5, and the forced-air drying oven 3 in sequence. After the equipment cools down, remove the sealed box 7 and the film capacitor 1.

[0140] Please see Figure 3 As shown, Figure 3This is a schematic diagram of the structure of the metallized film capacitor center temperature testing device 200 provided in this application embodiment. The metallized film capacitor center temperature testing device 200 is used to perform the steps of the metallized film capacitor center temperature testing method shown in the above embodiments. The metallized film capacitor center temperature testing device 200 can be a single server or a server cluster, or it can be a terminal, such as a handheld terminal, a laptop computer, a wearable device, or a robot.

[0141] like Figure 3 As shown, the metallized film capacitor center temperature testing device 200 includes: The wire end processing unit 201 is used to pre-process the thermocouple wire ends by stripping the thermocouple wire ends to a preset length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the two twisted alloy wires in molten tin to make the two alloy wires firmly connected, and wrapping the alloy wires with high-temperature tape. The hot-pressing fixing unit 202 is used to place the pre-treated thermocouple into a constant temperature chamber for temperature calibration; to wind a circular core during capacitor winding, with a pre-drilled shaft diameter hole in the center of the core; to place the calibrated thermocouple wire end into the pre-set depth in the shaft diameter hole in the center of the core; and to perform hot-pressing, gold spraying, welding, assembly, and encapsulation processes on the capacitor core with the thermocouple wire end placed therein, thereby fixing the thermocouple wire end by hot pressing. The curve plotting unit 203 is used to connect the packaged capacitor to the fixture connected to the test power supply and place it into a sealed box; place the entire sealed box into a pre-set temperature drying oven; apply the rated load to the capacitor through the test power supply; and after the ambient temperature of the capacitor reaches the preset value, collect the temperature data of the center of the capacitor within a preset time period and plot the temperature change curve based on the collected temperature data.

[0142] In some embodiments, the step of stripping the thermocouple wire end to a predetermined length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the twisted alloy wires in molten solder to secure the connection, and wrapping the alloy wires with high-temperature tape includes: using a wire stripper to strip two millimeters of the thermocouple wire end to expose two complete alloy wires; twisting the two alloy wires together at least three times in the same direction and tightening them; immersing the ends of the tightened alloy wires in molten solder for one to two seconds to fully connect the two alloy wires through solder; and completely covering the alloy wire connection area with high-temperature tape made of high-temperature resistant insulating glass cloth, wrapping only one loop.

[0143] In some embodiments, applying a rated load to the capacitor via a test power supply includes: the test power supply outputting power to the capacitor according to a preset rated operating voltage, rated effective current, and rated ripple frequency; the test power supply acquiring the capacitor's operating voltage and current data in real time, and dynamically adjusting the output parameters based on the acquired operating voltage and current data to ensure that the capacitor always operates under rated load conditions.

[0144] In some embodiments, the step of collecting temperature data at the center of the capacitor within a preset time period after the ambient temperature of the capacitor reaches a preset value, and plotting a temperature change curve based on the collected temperature data, includes: continuously collecting temperature data at the center of the capacitor after the ambient temperature of the capacitor reaches the preset value and remains stable; performing moving average filtering and noise reduction processing on the collected raw temperature data to identify the thermal equilibrium point of the temperature data; calculating the average value of the temperature data after collecting the thermal equilibrium point as the final center temperature value; and plotting a temperature change curve with time as the horizontal axis and temperature as the vertical axis.

[0145] In some embodiments, the step of placing the pre-treated thermocouples into a constant temperature chamber for temperature calibration includes: simultaneously placing multiple pre-treated thermocouples in the same position inside the constant temperature chamber; sequentially setting three different calibration temperature points in the constant temperature chamber; collecting the output data of each thermocouple after maintaining a stable position at each calibration temperature point for a preset time; calculating the error value of each thermocouple at each temperature point; and generating a temperature error compensation curve corresponding to each thermocouple based on the error value of each thermocouple at each temperature point, so as to correct the collected temperature data according to the corresponding temperature error compensation curve during the test.

[0146] In some embodiments, the step of winding a circular core during capacitor winding, with a pre-drilled shaft diameter hole at the center of the core, includes: using a winding machine to wind a circular core according to a preset film thickness and core diameter; detecting the roundness of the core and the inner diameter of the shaft diameter hole in real time during the winding process; and automatically adjusting the tension and speed parameters of the winding machine when the roundness or inner diameter exceeds a preset range, so that the centerness and dimensional accuracy of the shaft diameter hole meet the requirements.

[0147] In some embodiments, inserting the calibrated thermocouple wire tip into the central bore of the core at a predetermined depth includes: using a displacement sensor to detect the insertion depth of the thermocouple wire tip, stopping the insertion when the insertion depth reaches a predetermined range of the total depth of the bore, and using a visual inspection device to confirm that the thermocouple wire tip is located at the central axis position of the bore.

[0148] In some embodiments, the process of hot pressing, gold spraying, welding, assembly, and encapsulation is performed sequentially on the capacitor core with the thermocouple wire head placed therein. The process of fixing the thermocouple wire head by hot pressing includes: hot pressing the capacitor core according to preset hot pressing temperature and pressure parameters; monitoring the temperature and pressure of the hot pressing head in real time during the hot pressing process; ending the hot pressing when the temperature and pressure reach preset values ​​and are maintained for a preset time, so that the thermocouple wire head is tightly bonded to the core without damaging the core film; and then completing the processes of gold spraying, welding, assembly, and encapsulation sequentially.

[0149] In some embodiments, the step of connecting the encapsulated capacitor to the fixture connected to the test power supply and then placing it into a sealed box includes: firmly connecting the two electrodes of the capacitor to the two conductive terminals of the fixture respectively; confirming the continuity between the capacitor and the fixture through a continuity detection device; placing the capacitor and the fixture as a whole into a fixed position inside the sealed box; closing the lid of the sealed box and performing an airtightness test to ensure that the inside of the sealed box is completely isolated from the outside air.

[0150] In some embodiments, placing the sealed box entirely into a preheated drying oven at a preset temperature includes: preheating the drying oven to a preset temperature and maintaining the temperature for a preset stable time, placing the sealed box stably in the center of the drying oven to ensure uniform air temperature around the sealed box, and closing the door of the drying oven.

[0151] It should be noted that those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the metallized film capacitor center temperature testing device and its modules described above can be referred to the corresponding content in the various embodiments of the metallized film capacitor center temperature testing method, and will not be repeated here.

[0152] The aforementioned method for testing the center temperature of metallized film capacitors can be implemented as a computer program, which can be used in various applications such as... Figure 3 It runs on the device shown.

[0153] Please see Figure 4 , Figure 4 This is a schematic block diagram of the structure of a computer device provided in an embodiment of this application. The computer device includes a processor, a memory, and a network interface connected via a device bus, wherein the memory may include a storage medium and internal memory.

[0154] The storage medium can store operating devices and computer programs. The computer program includes program instructions that, when executed, cause the processor to perform any method for testing the center temperature of a metallized film capacitor.

[0155] The processor provides computing and control capabilities, supporting the operation of the entire computer device.

[0156] The internal memory provides an environment for the execution of computer programs in non-volatile storage media. When executed by a processor, the computer program can enable the processor to perform any method for testing the center temperature of a metallized film capacitor.

[0157] This network interface is used for network communication, such as sending assigned tasks. Those skilled in the art will understand that... Figure 4 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the terminal to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0158] It should be understood that the processor can be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among these, a general-purpose processor can be a microprocessor or any conventional processor.

[0159] In one embodiment, the processor is configured to run a computer program stored in memory to perform the following steps: Pre-treat the thermocouple wire ends by stripping the thermocouple wire ends to a predetermined length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the twisted alloy wires in molten tin to make the two alloy wires firmly connected, and wrapping the alloy wires with high-temperature tape. The pre-treated thermocouple is placed in a constant temperature chamber for temperature calibration; a circular core is wound during capacitor winding, with a pre-drilled shaft diameter hole in the center of the core; the calibrated thermocouple wire ends are placed into the pre-set depth in the shaft diameter hole in the center of the core; the capacitor core with the thermocouple wire ends placed is subjected to hot pressing, gold spraying, welding, assembly and encapsulation processes in sequence, and the thermocouple wire ends are fixed by hot pressing. After the encapsulated capacitor is connected to the fixture for the test power supply, it is placed in a sealed box. The sealed box is then placed in a pre-set temperature drying oven. The rated load is applied to the capacitor through the test power supply. Once the ambient temperature of the capacitor reaches the preset value, the temperature data of the center of the capacitor is collected within a preset time period, and a temperature change curve is plotted based on the collected temperature data.

[0160] In some embodiments, the step of stripping the thermocouple wire end to a predetermined length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the twisted alloy wires in molten solder to secure the connection, and wrapping the alloy wires with high-temperature tape includes: using a wire stripper to strip two millimeters of the thermocouple wire end to expose two complete alloy wires; twisting the two alloy wires together at least three times in the same direction and tightening them; immersing the ends of the tightened alloy wires in molten solder for one to two seconds to fully connect the two alloy wires through solder; and completely covering the alloy wire connection area with high-temperature tape made of high-temperature resistant insulating glass cloth, wrapping only one loop.

[0161] In some embodiments, applying a rated load to the capacitor via a test power supply includes: the test power supply outputting power to the capacitor according to a preset rated operating voltage, rated effective current, and rated ripple frequency; the test power supply acquiring the capacitor's operating voltage and current data in real time, and dynamically adjusting the output parameters based on the acquired operating voltage and current data to ensure that the capacitor always operates under rated load conditions.

[0162] In some embodiments, the step of collecting temperature data at the center of the capacitor within a preset time period after the ambient temperature of the capacitor reaches a preset value, and plotting a temperature change curve based on the collected temperature data, includes: continuously collecting temperature data at the center of the capacitor after the ambient temperature of the capacitor reaches the preset value and remains stable; performing moving average filtering and noise reduction processing on the collected raw temperature data to identify the thermal equilibrium point of the temperature data; calculating the average value of the temperature data after collecting the thermal equilibrium point as the final center temperature value; and plotting a temperature change curve with time as the horizontal axis and temperature as the vertical axis.

[0163] In some embodiments, the step of placing the pre-treated thermocouples into a constant temperature chamber for temperature calibration includes: simultaneously placing multiple pre-treated thermocouples in the same position inside the constant temperature chamber; sequentially setting three different calibration temperature points in the constant temperature chamber; collecting the output data of each thermocouple after maintaining a stable position at each calibration temperature point for a preset time; calculating the error value of each thermocouple at each temperature point; and generating a temperature error compensation curve corresponding to each thermocouple based on the error value of each thermocouple at each temperature point, so as to correct the collected temperature data according to the corresponding temperature error compensation curve during the test.

[0164] In some embodiments, the step of winding a circular core during capacitor winding, with a pre-drilled shaft diameter hole at the center of the core, includes: using a winding machine to wind a circular core according to a preset film thickness and core diameter; detecting the roundness of the core and the inner diameter of the shaft diameter hole in real time during the winding process; and automatically adjusting the tension and speed parameters of the winding machine when the roundness or inner diameter exceeds a preset range, so that the centerness and dimensional accuracy of the shaft diameter hole meet the requirements.

[0165] In some embodiments, inserting the calibrated thermocouple wire tip into the central bore of the core at a predetermined depth includes: using a displacement sensor to detect the insertion depth of the thermocouple wire tip, stopping the insertion when the insertion depth reaches a predetermined range of the total depth of the bore, and using a visual inspection device to confirm that the thermocouple wire tip is located at the central axis position of the bore.

[0166] In some embodiments, the process of hot pressing, gold spraying, welding, assembly, and encapsulation is performed sequentially on the capacitor core with the thermocouple wire head placed therein. The process of fixing the thermocouple wire head by hot pressing includes: hot pressing the capacitor core according to preset hot pressing temperature and pressure parameters; monitoring the temperature and pressure of the hot pressing head in real time during the hot pressing process; ending the hot pressing when the temperature and pressure reach preset values ​​and are maintained for a preset time, so that the thermocouple wire head is tightly bonded to the core without damaging the core film; and then completing the processes of gold spraying, welding, assembly, and encapsulation sequentially.

[0167] In some embodiments, the step of connecting the encapsulated capacitor to the fixture connected to the test power supply and then placing it into a sealed box includes: firmly connecting the two electrodes of the capacitor to the two conductive terminals of the fixture respectively; confirming the continuity between the capacitor and the fixture through a continuity detection device; placing the capacitor and the fixture as a whole into a fixed position inside the sealed box; closing the lid of the sealed box and performing an airtightness test to ensure that the inside of the sealed box is completely isolated from the outside air.

[0168] In some embodiments, placing the sealed box entirely into a preheated drying oven at a preset temperature includes: preheating the drying oven to a preset temperature and maintaining the temperature for a preset stable time, placing the sealed box stably in the center of the drying oven to ensure uniform air temperature around the sealed box, and closing the door of the drying oven.

[0169] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the steps of the metallized thin-film capacitor center temperature testing method provided in any embodiment of this application.

[0170] The computer-readable storage medium may be an internal storage unit of the computer device described in the foregoing embodiments, such as the hard disk or memory of the computer device. The computer-readable storage medium may also be an external storage device of the computer device, such as a plug-in hard disk, SmartMedia Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the computer device.

[0171] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for testing the center temperature of a metallized thin-film capacitor, characterized in that, include: Pre-treat the thermocouple wire ends by stripping the thermocouple wire ends to a predetermined length to expose two alloy wires, twisting the two alloy wires together tightly, immersing the twisted alloy wires in molten tin to make the two alloy wires firmly connected, and wrapping the alloy wires with high-temperature tape. The pre-treated thermocouple is placed in a constant temperature chamber for temperature calibration; a circular core is wound during capacitor winding, with a pre-drilled shaft diameter hole in the center of the core; the calibrated thermocouple wire ends are placed into the pre-set depth in the shaft diameter hole in the center of the core; the capacitor core with the thermocouple wire ends placed is subjected to hot pressing, gold spraying, welding, assembly and encapsulation processes in sequence, and the thermocouple wire ends are fixed by hot pressing. After the encapsulated capacitor is connected to the clamp connected to the test power supply, it is placed in a sealed box; then the entire sealed box is placed in a forced-air drying oven at a preset temperature. The rated load is applied to the capacitor by the test power supply; after the ambient temperature of the capacitor reaches the preset value, the temperature data of the center of the capacitor within a preset time period is collected, and the temperature change curve is plotted based on the collected temperature data.

2. The method according to claim 1, characterized in that, The process involves stripping the thermocouple wires to a predetermined length, exposing two alloy wires, twisting the two alloy wires together tightly, immersing the twisted alloy wires in molten solder to secure the connection, and then wrapping the alloy wires with high-temperature adhesive tape. The procedure includes: Use a wire stripper to strip two millimeters of the thermocouple wire end, exposing two complete alloy wires. Wrap the two alloy wires together at least three times in the same direction and tighten them. Immerse the tightened end of the alloy wire into molten solder for one to two seconds to fully connect the two alloy wires through solder. High-temperature adhesive tape made of high-temperature resistant insulating glass cloth is used to completely cover the alloy wire connection area and only wraps it once.

3. The method according to claim 1, characterized in that, The process of applying a rated load to the capacitor via a test power supply includes: The test power supply outputs power to the capacitor according to the preset rated operating voltage, rated effective current and rated ripple frequency; The test power supply collects the capacitor's operating voltage and current data in real time, and dynamically adjusts the output parameters based on the collected operating voltage and current data to ensure that the capacitor always operates under rated load conditions.

4. The method according to claim 3, characterized in that, Once the ambient temperature of the capacitor reaches a preset value, temperature data is collected from the center of the capacitor within a preset time period, and a temperature change curve is plotted based on the collected temperature data, including: Once the ambient temperature of the capacitor reaches the preset value and remains stable, the temperature data at the center of the capacitor is continuously collected. The collected raw temperature data is then processed by moving average filtering to remove noise and identify the thermal equilibrium point of the temperature data. After collecting temperature data at the thermal equilibrium point, the average value is calculated as the final center temperature value, and a temperature change curve is plotted with time as the horizontal axis and temperature as the vertical axis.

5. The method according to claim 1, characterized in that, The step of placing the pretreated thermocouple in a constant temperature chamber for temperature calibration includes: Multiple pre-treated thermocouples are placed in the same position inside the constant temperature chamber. The constant temperature chamber is set with three different calibration temperature points in sequence. After the temperature is stabilized at each calibration temperature point for a preset time, the output data of each thermocouple is collected, and the error value of each thermocouple at each temperature point is calculated. Based on the error value of each thermocouple at each temperature point, a temperature error compensation curve is generated for each thermocouple, so that the collected temperature data can be corrected according to the corresponding temperature error compensation curve during the test.

6. The method according to claim 1, characterized in that, The method of winding a circular core during capacitor winding, with a pre-drilled axial diameter hole in the center of the core, includes: A winding machine is used to wind a circular core according to the preset film thickness and core diameter. During the winding process, the roundness of the core and the inner diameter of the shaft diameter hole are detected in real time. When the roundness or inner diameter exceeds the preset range, the tension and speed parameters of the winding machine are adjusted so that the centerness and dimensional accuracy of the shaft diameter hole meet the requirements.

7. The method according to claim 1, characterized in that, The step of inserting the calibrated thermocouple wire end into the core's central shaft diameter hole at a predetermined depth includes: A displacement sensor is used to detect the insertion depth of the thermocouple wire tip. Insertion is stopped when the insertion depth reaches the preset range of the total depth of the shaft diameter hole, and a visual inspection device is used to confirm that the thermocouple wire tip is located at the center axis position of the shaft diameter hole.

8. The method according to claim 1, characterized in that, The process of hot pressing, gold spraying, welding, assembly, and encapsulation of the capacitor core with the thermocouple wire ends in place, and fixing the thermocouple wire ends by hot pressing, includes: The capacitor core is hot-pressed according to the preset hot-pressing temperature and pressure parameters. The temperature and pressure of the hot-pressing head are monitored in real time during the hot-pressing process. The hot-pressing ends when the temperature and pressure reach the preset value and are maintained for the preset time, so that the thermocouple wire ends are tightly connected to the core without damaging the core film. Then, the processes of gold spraying, welding, assembly and packaging are completed in sequence.

9. The method according to claim 1, characterized in that, The step of connecting the encapsulated capacitor to the clamp connected to the test power supply and placing it in a sealed box includes: Securely connect the two electrodes of the capacitor to the two conductive terminals of the clamp, confirm the continuity between the capacitor and the clamp using a continuity testing device, place the capacitor and clamp together in a fixed position inside the sealed box, close the lid of the sealed box and perform an airtightness test to ensure that the inside of the sealed box is completely isolated from the outside air.

10. The method according to claim 9, characterized in that, The step of placing the entire sealed box into a pre-set temperature forced-air drying oven includes: Preheat the drying oven to the preset temperature and maintain the temperature for the preset duration. Place the sealed box stably in the center of the drying oven to ensure that the air temperature around the sealed box is uniform. Then close the door of the drying oven.

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