CN113311265A - Method and system for predicting service life of metallized film capacitor - Google Patents

Method and system for predicting service life of metallized film capacitor Download PDF

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CN113311265A
CN113311265A CN202110573283.9A CN202110573283A CN113311265A CN 113311265 A CN113311265 A CN 113311265A CN 202110573283 A CN202110573283 A CN 202110573283A CN 113311265 A CN113311265 A CN 113311265A
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metallized film
film capacitor
humidity
temperature
capacitance
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CN113311265B (en
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李化
李征
林福昌
王燕
张钦
刘毅
李柳霞
邱天
王雨橙
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Huazhong University of Science and Technology
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Abstract

The invention discloses a method and a system for predicting the service life of a metallized film capacitor, and belongs to the field of capacitor service life prediction. The method comprises the following steps: fitting capacitance change rate k of metallized film capacitor under different temperature and humidity conditionsc(T, RH), calculating the critical time point T of the water in the external atmosphere entering the capacitor0(T, RH); calculating Delta C under different temperature and humidity conditionsr(T，RH)＝kc(T，RH)*t0(T, RH); calculating delta C of metallized film capacitor under extreme temperature and humidity of working environmentrA value; the metallized film capacitor is changed to the capacitance change rate to delta C from the beginning of operationrAs the life of the metallized film capacitor. The invention provides a method for calculating the service life ending criterion of a metallized film capacitor according to the temperature and the humidity of the external environment, and compared with the traditional fixed service life ending criterion, the method provided by the invention considers the metallized film capacitorUnder the capacitance loss condition under different temperature and humidity environment, when the application environment condition is comparatively abominable complicated, the use of condenser can be more reliable stable.

Description

Method and system for predicting service life of metallized film capacitor
Technical Field
The invention belongs to the field of capacitor life prediction, and particularly relates to a method and a system for predicting the life of a metallized film capacitor.
Background
The metallized film capacitor is widely used for suppressing electromagnetic interference in a line, and is generally connected in parallel in an alternating current line to ensure stable operation of the line. In recent years, the use of metallized film capacitors in low power capacitive power supplies has expanded, where the capacitors are connected in series with a load (e.g., a smart meter) to limit the amount of current.
In a humid environment, the capacitance of the metallized film capacitor is gradually reduced, and anatomical analysis on a failed metallized film capacitor shows that electrochemical corrosion occurs on an electrode with the nanometer-scale thickness, and the electrode is converted into an oxide with better insulating property, so that the effective area of the electrode is reduced, and the capacitance is reduced. The capacitance drop further results in a reduction in the current limiting and high frequency emi filtering of the metallized film capacitor. Therefore, the electrochemical aging characteristic model of the metallized film capacitor is established based on capacitance loss, and the method has important significance for improving the operation reliability of the circuit.
The existing capacitance aging model mostly relates to the prediction of the capacitor life, namely the prediction of the working time of the capacitance which is reduced to a certain value. The metallized film capacitor generally adopts an epoxy resin encapsulation structure, and aging research aiming at the metallized film capacitor under the high-temperature and high-humidity conditions shows that the capacitance reduction process is staged, the early-stage reduction is slow, the linear law is formed along with time, and the capacitance begins to be reduced in an accelerated manner after a period of time. The existing capacitor aging model is not related to the electrochemical corrosion process of the capacitor electrode, and for the capacitor aging caused by the electrochemical corrosion of the electrode, the difference between the calculation result and the actual condition sometimes exceeds the acceptable range. Therefore, it is an urgent technical problem to research an effective electrochemical aging characteristic model of a metallized film capacitor for evaluating the performance and the service life of the capacitor.
Disclosure of Invention
The invention provides a method and a system for predicting the service life of a metallized film capacitor, aiming at the defects and improvement requirements of the prior art, and aiming at determining the service life termination criterion of the capacitor and predicting the corresponding service life according to the temperature and humidity environment applied to the metallized film capacitor.
To achieve the above object, according to a first aspect of the present invention, there is provided a metallized film capacitor life prediction method including:
fitting capacitance change rate k of metallized film capacitor under different temperature and humidity conditionsc(T, RH), calculating the critical time point T of the water in the external atmosphere entering the capacitor0(T,RH)；
Calculating Delta C under different temperature and humidity conditionsr(T,RH)＝kc(T,RH)*t0(T,RH)；
Calculating delta C of metallized film capacitor under extreme temperature and humidity of working environmentrA value;
the metallized film capacitor is changed to the capacitance change rate to delta C from the beginning of operationrAs the life of the metallized film capacitor.
Preferably, the fitted metallized film capacitor has a capacitance change rate k under different temperature and humidity conditionsc(T, RH) comprising:
(1) carrying out accelerated aging tests under three different temperature and humidity conditions until the capacitance begins to decrease in an accelerated manner, and stopping the tests, wherein the first temperature and humidity condition is 85 ℃ plus 85% RH, the second temperature and humidity condition is t2 plus 85% RH, the third temperature and humidity condition is 85 ℃ plus RH3, t2 is more than or equal to 35 ℃ and less than 85 ℃, and RH3 is more than or equal to 35% and less than 85%;
(2) measuring the capacitance of the metallized film capacitor under different temperature and humidity conditions relative to the time-varying quantity delta C before the test1(t),ΔC2(t),ΔC3(t)；
(3) Respectively corresponding to the quantity Δ C1(t),ΔC2(t),ΔC3Linear fitting is carried out on the linear section of (t) to obtain the capacitance change rate k under the temperature and humidity conditionc1,kc2,kc3；
(4) Will kc1As a reference value of the Peck accelerated aging model; will kc2Substituting into Peck accelerated aging model to determine activation energy E in the modelak(ii) a Will kc3Substituting into Peck accelerated aging model to determine humidity coefficient n in the modelk(ii) a Further get kc(T,RH)。
Has the advantages that: because the reliability of the metallized film capacitor is high, the capacitance is reduced slowly under the working environment, the invention can accelerate the capacitor failure under the condition of not changing the failure mechanism of the capacitor by carrying out the accelerated aging test under higher temperature and humidity, and can obtain k by only 3 accelerated aging tests through the Peck accelerated aging modelc(T, RH), thereby achieving the effect of shortening the test time and cost.
Preferably, the capacitance is calculated as follows with respect to the amount of change with time before the test:
Figure BDA0003083446880000031
wherein, C0Representing the pre-test capacitance, and C (t) is the capacitance for the test duration t.
Has the advantages that: because the capacitance of the metallized film capacitor before the test is different, the capacitance of the capacitor at the end of the service life is different and can not be directly compared, the invention carries out normalization processing on the capacitance changing along with the time relative to the value before the test, thereby eliminating the influence of the capacitance before the test on the criterion of the end of the service life of the capacitor.
Preferably, the calculating moisture in the external atmospheric environmentCritical time t of intrusion into the interior of the capacitor0(T, RH) comprising:
obtaining the diffusion coefficient D (T, RH) of the encapsulating material of the metallized film capacitor under different temperature and humidity conditions;
calculating a critical time point
Figure BDA0003083446880000032
Wherein h represents the thickness of the potting structure of the metallized film capacitor.
Has the advantages that: because the critical time point of the capacitance accelerated decrease of the metallized film capacitor is related to the diffusion of moisture in the encapsulating material, the calculation of the critical time point under different temperature and humidity conditions is realized by obtaining the diffusion coefficient of the encapsulating material of the metallized film capacitor.
Preferably, the obtaining of the diffusion coefficient D (T, RH) of the potting material of the metallized film capacitor under different temperature and humidity conditions includes:
(1) carrying out accelerated aging tests under five different temperature and humidity conditions, stopping the tests until the mass fluctuation within 100 hours does not exceed 0.02%, wherein the first temperature and humidity condition is 85 ℃ and 85% RH, the second temperature and humidity condition and the third humidity condition are t2+ 85% RH and t3+ 85% RH, and the fourth temperature and humidity condition and the fifth temperature and humidity condition are as follows: 85 ℃ plus RH4, 85 ℃ plus RH5, t2 at a temperature of between 35 ℃ and less, t3 is less than 85 ℃, 35 percent is less than or equal to RH4, and RH5 is less than 85 percent;
(2) measuring the change quantity delta m of the mass of the metallized film capacitor under different temperature and humidity conditions relative to the time before the test1(t),Δm2(t),Δm3(t),Δm4(t),Δm5(t)；
(3) Respectively fitting the values of Δ m nonlinearly according to Fick's second law1(t)，Δm2(t)，Δm3(t)，Δm4(t)，Δm5(t), further determining the diffusion coefficient D1,D2,D3,D4,D5；
(4) Will D1,D2,D3Substituting into Arrhenius model to determine activation energy E in the modelaDD is1,D4,D5Substituting the humidity InversePower model into the model to determine the humidity coefficient n in the modelD(ii) a D (T, RH) is obtained.
Has the advantages that: according to the invention, accelerated aging tests are carried out at different temperatures and humidities, the diffusion coefficient is obtained according to the quality change of the capacitor under the condition that the diffusion mechanism of moisture in the encapsulating material is not changed, and D (T, RH) can be obtained through 5 accelerated aging tests only through an Arrhenius model and a humidity InversePower model, so that the effects of shortening the test time and reducing the cost are realized.
Preferably, the non-linear fit equation according to Fick's second law is as follows:
Figure BDA0003083446880000041
wherein h represents the thickness of the encapsulating structure of the metallized film capacitor, D represents the diffusion coefficient of the encapsulating material of the metallized film capacitor, and MmA value of Δ m representing a mass fluctuation of the metallized film capacitor of not more than 0.02% in 100 hours.
Has the advantages that: the diffusion coefficient of the moisture in the encapsulating material needs to be obtained through the distribution of the moisture content, and the moisture content in the encapsulating material is more difficult to measure relative to the mass.
To achieve the above object, according to a second aspect of the present invention, there is provided a metallized film capacitor life prediction system comprising:
a processor configured to execute computer-executable instructions;
a memory storing one or more computer-executable instructions that, when executed by the processor, perform the steps of the method for predicting the lifetime of a metallized film capacitor of the first aspect.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
hair brushObviously, by fitting the capacitance change rate of the metallized film capacitor under different temperature and humidity conditions, the critical time point of the moisture in the external atmospheric environment invading the capacitor is calculated, and then the delta C under different temperature and humidity conditions is calculatedr(T, RH), calculating delta C under extreme temperature and humidity of working environment of the metallized film capacitorrValue, the change rate of the capacitance of the metallized film capacitor from the beginning of the operation to Δ CrAs the life of the metallized film capacitor. Compared with the traditional fixed life end criterion, the method provided by the invention considers the capacitance loss condition of the metallized film capacitor under different temperature and humidity environments, and the capacitor can be used more reliably and stably when the application environment conditions are severe and complicated.
Drawings
FIG. 1 is a flow chart of a method for predicting the lifetime of a metallized film capacitor according to the present invention;
fig. 2 is a capacitance variation curve and a weight gain curve provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features mentioned in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
As shown in fig. 1, the present invention provides a method for predicting the lifetime of a metallized film capacitor, comprising:
fitting capacitance change rate k of metallized film capacitor under different temperature and humidity conditionsc(T, RH), calculating the critical time point T of the water in the external atmosphere entering the capacitor0(T,RH)。
Preferably, the fitted metallized film capacitor has a capacitance change rate k under different temperature and humidity conditionsc(T, RH) comprising:
(1) and carrying out accelerated aging tests under three different temperature and humidity conditions until the capacitance starts to decrease in an accelerated manner, and stopping the tests, wherein the first temperature and humidity condition is 85 ℃ plus 85% RH, the second temperature and humidity condition is t2 plus 85% RH, the third temperature and humidity condition is 85 ℃ plus RH3, t2 is more than or equal to 35 ℃ and less than 85 ℃, and RH3 is more than or equal to 35% and less than 85%.
And (3) placing the sample capacitor in a constant temperature and humidity test box, and applying alternating voltage to two ends of the capacitor, wherein the voltage value is at least 1 time of rated voltage. In this example, t2 was 60 ℃ and RH3 was 60%.
(2) Measuring the capacitance of the metallized film capacitor under different temperature and humidity conditions relative to the time-varying quantity delta C before the test1(t),ΔC2(t),ΔC3(t)。
To obtain the Δ c (t) curve, the capacitance needs to be measured at regular intervals. In consideration of the subsequent fitting precision problem, the data points are not too few, and the measurement interval does not exceed 24 hours.
(3) Respectively corresponding to the quantity Δ C1(t),ΔC2(t),ΔC3Linear fitting is carried out on the linear section of (t) to obtain the slope under the temperature and humidity condition, namely the capacitance change rate kc1,kc2,kc3。
(4) Will kc1As a reference value of the Peck accelerated aging model; will kc2Substituting into Peck accelerated aging model to determine activation energy E in the modelak(ii) a Will kc3Substituting into Peck accelerated aging model to determine humidity coefficient n in the modelk(ii) a Further get kc(T,RH)。
Figure BDA0003083446880000061
Wherein, TA＝358.15K，RHA＝85％，kBIs the Boltzmann constant, kB＝8.623×10-5eV/K。
Preferably, the capacitance is calculated as follows with respect to the amount of change with time before the test:
Figure BDA0003083446880000062
wherein, C0Representing the pre-test capacitance, and C (t) is the capacitance for the test duration t.
Preferably, the critical time point t of the moisture in the external atmospheric environment intruding into the capacitor is calculated0(T, RH) comprising:
and obtaining the diffusion coefficient D (T, RH) of the encapsulating material of the metallized film capacitor under different temperature and humidity conditions.
The data source can be product data of the encapsulating material and can also be calculated by an accelerated aging test.
Calculating a critical time point
Figure BDA0003083446880000071
Wherein h represents the thickness of the potting structure of the metallized film capacitor.
Preferably, the obtaining of the diffusion coefficient D (T, RH) of the potting material of the metallized film capacitor under different temperature and humidity conditions includes:
(1) carrying out accelerated aging tests under five different temperature and humidity conditions, stopping the tests until the mass fluctuation within 100 hours does not exceed 0.02%, wherein the first temperature and humidity condition is 85 ℃ and 85% RH, the second temperature and humidity condition and the third humidity condition are t2+ 85% RH and t3+ 85% RH, and the fourth temperature and humidity condition and the fifth temperature and humidity condition are as follows: 85 ℃ plus RH4, 85 ℃ plus RH5, t2 at 35 ℃ or less, t3 at 85 ℃ or less, RH4 at 35% or less and RH5 at 85% or less.
In this example, t2 was 60 ℃, t3 was 35 ℃, RH4 was 60%, and RH5 was 35%.
(2) Measuring the change quantity delta m of the mass of the metallized film capacitor under different temperature and humidity conditions relative to the time before the test1(t),Δm2(t),Δm3(t),Δm4(t),Δm5(t)。
Figure BDA0003083446880000072
(3) Respectively fitting the values of Δ m nonlinearly according to Fick's second law1(t)，Δm2(t)，Δm3(t)，Δm4(t)，Δm5(t), further determining the diffusion coefficient D1,D2,D3,D4,D5。
Preferably, the non-linear fit equation according to Fick's second law is as follows:
Figure BDA0003083446880000073
wherein h represents the thickness of the encapsulating structure of the metallized film capacitor, D represents the diffusion coefficient of the encapsulating material of the metallized film capacitor, and MmA value of Δ m representing a mass fluctuation of no more than 0.02% over 100 hours of the metallized film capacitor is used to characterize the saturated weight gain of the metallized film capacitor.
(4) Will D1,D2,D3Substituting into Arrhenius model to determine activation energy E in the modelaDD is1,D4,D5Substituting the humidity InversePower model into the model to determine the humidity coefficient n in the modelD(ii) a D (T, RH) is obtained.
The Arrhenius model is as follows:
Figure BDA0003083446880000081
wherein, TA＝358.15K。
The humidity InversePower model is as follows:
Figure BDA0003083446880000082
wherein RH isA＝85％。
Calculating Delta C under different temperature and humidity conditionsr(T,RH)＝kc(T,RH)*t0(T,RH)。
Calculating the service life and service life end criterion Delta C of the metallized film capacitor under extreme temperature and humidityrThe value:
Figure BDA0003083446880000083
Figure BDA0003083446880000084
wherein, TA＝358.15K，RHA85 percent. In the case of the metallized film capacitor having the potting structure, it takes time for moisture in the external atmospheric environment to intrude into the capacitor, which is expressed as time for saturation of water absorption weight increase of the capacitor, and thus the capacitance drop process caused by electrochemical corrosion of the electrode is roughly divided into 2 stages: (1) the first stage is involved in electrode corrosion, namely the water pre-existing in the capacitor is low in content, the capacitance is slowly reduced, and the capacitance changes linearly along with time; (2) and in the second stage, moisture in the external atmospheric environment invades into the capacitor, so that the moisture participating in electrode corrosion is greatly increased, and the capacitance reduction rate is accelerated. The division point of the two phases is t0As shown in fig. 2, the corresponding capacitance amount changes by Δ CrCapacitance drop exceeding Δ CrThen, the capacitance begins to decrease in an accelerated manner, and the encapsulation structure is saturated with water, the protective effect is reduced, so that Δ CrCan be used as the criterion of the service life ending.
The metallized film capacitor is changed to the capacitance change rate to delta C from the beginning of operationrAs the life of the metallized film capacitor.
Examples
The rated capacitance of the metallized film capacitor is 470nF, the total number of the metallized film capacitors is 15, the set temperature of the constant temperature and humidity box is 85 ℃, and the relative humidity is set to be 85%. Electrically connecting the metallized film capacitor in the constant temperature and humidity box with the lead wire, leading the lead wire out from the outlet, and measuring the initial capacitance C of the metallized film capacitor by using an LCR digital bridge0(test frequency 1000Hz), initial mass m was measured using a balance0. And after the quality measurement is finished, closing an alternating current voltage source switch, adjusting an output voltage value, applying alternating current voltage to two ends of the metallized film capacitor by using an alternating current voltage source, wherein the alternating current voltage has an effective value of 305V, and monitoring the voltage at two ends of the capacitor in real time by a voltmeter.In the test process, every time T is 24h, the output voltage value of the alternating current voltage source is adjusted to zero, the alternating current voltage source switch is turned off, the capacitance C (T) and the mass m (T) of the metallized film capacitor are measured, and the capacitance variation is calculated
Figure BDA0003083446880000091
And amount of mass change
Figure BDA0003083446880000092
Test duration ttest600 h. According to the test time ttestThe change in capacitance Δ c (t) and the change in mass Δ m (t) over 600h are analyzed, from which k is calculated by fittingcAnd diffusion coefficient D, temperature 85 deg.C, relative humidity 85%,
kc(85℃,85％RH)＝－4.16×10-4/h
D(85℃,85％RH)＝9.54×10-3mm2/h
t0(85℃,85％RH)＝205h，ΔCr(85℃,85％RH)＝－8.55％。
setting the temperature of the constant temperature and humidity box to be 60 ℃, setting the relative humidity to be 85 percent, setting the rest of the test and the steps to be the same, and calculating to obtain
kc(60℃,85％RH)＝－3.39×10-4/h
D(60℃,85％RH)＝2.67×10-2mm2/h,t0(60℃,85％RH)＝59h
ΔCr(60℃,85％RH)＝－2.00％。
Setting the temperature of the constant temperature and humidity box to be 85 ℃ and the relative humidity to be 60 percent, setting the rest of the test and the steps to be the same, and calculating to obtain
kc(85℃,60％RH)＝－1.14×10-4/h
D(85℃,60％RH)＝6.45×10-3mm2/h
t0(85℃,60％RH)＝321h
ΔCr(85℃,60％RH)＝－3.67％。
The set temperature of the constant temperature and humidity box is 35 ℃, the relative humidity is set to be 85 percent, only the mass of the capacitor is measured, the other test settings and steps are the same, and the calculation is carried out to obtain
D(35℃,85％RH)＝8.84×10-2mm2/h
t0(35℃,60％RH)＝28h。
Setting the temperature of the constant temperature and humidity chamber to 85 ℃ and the relative humidity to 35%, measuring the mass of the capacitor only, and calculating the mass values of the capacitor by using the same test settings and steps
D(85℃,35％RH)＝3.52×10-3mm2/h
t0(85℃,35％RH)＝557h。
Calculating model parameters E according to the test resultsak＝0.49eV，nk＝3.23；EaD＝0.42eV，nD1.12. The life and end-of-life criterion expression of the capacitor is as follows:
Figure BDA0003083446880000101
Figure BDA0003083446880000102
wherein, TA＝358.15K，RHA＝85％。
The invention also provides a life prediction system for the metallized film capacitor, which comprises:
a processor configured to execute computer-executable instructions;
and a memory storing one or more computer-executable instructions that, when executed by the processor, perform the steps of the method for predicting the life of a metallized film capacitor described above.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. A method for predicting a lifetime of a metallized film capacitor, comprising:
fitting capacitance change rate k of metallized film capacitor under different temperature and humidity conditionsc(T, RH), calculating the critical time point T of the water in the external atmosphere entering the capacitor0(T，RH)；
Calculating Delta C under different temperature and humidity conditionsr(T，RH)＝kc(T，RH)*t0(T，RH)；
Calculating delta C of metallized film capacitor under extreme temperature and humidity of working environmentrA value;
the metallized film capacitor is changed to the capacitance change rate to delta C from the beginning of operationrAs the life of the metallized film capacitor.
2. The method of claim 1, wherein the fitted metallized film capacitor has a rate of change of capacitance k at different temperature and humidity conditionsc(T, RH) comprising:
(1) carrying out accelerated aging tests under three different temperature and humidity conditions until the capacitance begins to decrease in an accelerated manner, and stopping the tests, wherein the first temperature and humidity condition is 85 ℃ plus 85% RH, the second temperature and humidity condition is t2 plus 85% RH, the third temperature and humidity condition is 85 ℃ plus RH3, t2 is more than or equal to 35 ℃ and less than 85 ℃, and RH3 is more than or equal to 35% and less than 85%;
(2) measuring the capacitance of the metallized film capacitor under different temperature and humidity conditions relative to the time-varying quantity delta C before the test1(t)，ΔC2(t)，ΔC3(t)；
(3) Respectively corresponding to the quantity Δ C1(t)，ΔC2(t)，ΔC3Linear fitting is carried out on the linear section of (t) to obtain the capacitance change rate k under the temperature and humidity conditionc1，kc2，kc3；
(4) Will kc1As a reference value of the Peck accelerated aging model; will kc2Substituting into Peck accelerated aging model to determine activation energy E in the modelak(ii) a Will kc3Substituting the result into a Peck accelerated aging model,determining the humidity coefficient n in the modelk(ii) a Further get kc(T，RH)。
3. The method of claim 2, wherein the capacitance is calculated as follows with respect to the amount of time change before the test:
Figure FDA0003083446870000011
wherein, C0Representing the pre-test capacitance, and C (t) is the capacitance for the test duration t.
4. Method according to any one of claims 1 to 3, characterized in that the critical point in time t at which the moisture in the external atmospheric environment penetrates into the interior of the capacitor is calculated0(T, RH) comprising:
obtaining the diffusion coefficient D (T, RH) of the encapsulating material of the metallized film capacitor under different temperature and humidity conditions;
calculating a critical time point
Figure FDA0003083446870000021
Wherein h represents the thickness of the potting structure of the metallized film capacitor.
5. The method of claim 4, wherein obtaining the diffusion coefficient D (T, RH) of the potting material of the metallized film capacitor under different temperature and humidity conditions comprises:
(1) carrying out accelerated aging tests under five different temperature and humidity conditions, stopping the tests until the mass fluctuation within 100 hours does not exceed 0.02%, wherein the first temperature and humidity condition is 85 ℃ and 85% RH, the second temperature and humidity condition and the third humidity condition are t2+ 85% RH and t3+ 85% RH, and the fourth temperature and humidity condition and the fifth temperature and humidity condition are as follows: 85 ℃ plus RH4 and 85 ℃ plus RH5, wherein t2 is more than or equal to 35 ℃ and less than 85 ℃, t3 is more than or equal to 35 ℃ and less than 85 ℃, RH4 is more than or equal to 35% and less than 85%, and RH5 is more than or equal to 35% and less than 85%;
(2) measuring different temperatures and humiditiesChange of mass of the metallized film capacitor with time before the test Δ m under the condition1(t)，Δm2(t)，Δm3(t)，Δm4(t)，Δm5(t)；
(3) Respectively fitting the values of Δ m nonlinearly according to Fick's second law1(t)，Δm2(t)，Δm3(t)，Δm4(t)，Δm5(t), further determining the diffusion coefficient D1，D2，D3，D4，D5；
(4) Will D1，D2，D3Substituting into Arrhenius model to determine activation energy E in the modelaDD is1，D4，D5Substituting the humidity InversePower model into the model to determine the humidity coefficient n in the modelD(ii) a D (T, RH) is obtained.
6. A method according to claim 5, wherein the non-linear fit according to Fick's second law is as follows:
Figure FDA0003083446870000022
wherein h represents the thickness of the encapsulating structure of the metallized film capacitor, D represents the diffusion coefficient of the encapsulating material of the metallized film capacitor, and MmA value of Δ m representing a mass fluctuation of the metallized film capacitor of not more than 0.02% in 100 hours.
7. A system for predicting the life of a metallized film capacitor, comprising:
a processor configured to execute computer-executable instructions;
a memory storing one or more computer-executable instructions that, when executed by the processor, perform the steps of the method of predicting metallized film capacitor life of any one of claims 1 to 6.
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