1. The structure of electrolytic capacitors is corroded. Etching anode and cathode metal foils are made

 of high-purity, very thin aluminum foil with a thickness of only 0.02-0.1mm. In order to increase the

 disk area and capacitance, the increase in surface area in contact with the electrolyte is achieved by

 etching the metal foil to dissolve the aluminum, forming a high-density mesh structure with billions 

of fine microchannels on the entire surface of the aluminum foil Forming the dielectric with capacitors 

on the anode foil The dielectric is a thin layer of aluminum oxide, AL2O3, That is a chemical growth

 process on the anode foil, which is called "formation" This voltage is 135% -200% of the rated voltage

 of the final capacitor The cathode foil does not need to be transformed, it maintains a high surface

 area and high-density etching mode The insufficient voltage resistance of the oxide film and the flash 

discharge of the electrolyte itself can cause short circuits The winding of the winding capacitor 

component consists of one layer of isolation paper, one layer of anode foil, another layer of isolation

 paper, and cathode foil These isolation papers prevent short circuits from forming between foils, and 

these separators later retain the electrolyte Attach foil to the later connected capacitor terminals 

during the winding of aluminum foil cores or winding process The best method is to use cold welding

 to attach the foil to the tape. Cold welding can reduce short-circuit failure and have better high ripple

 current performance and discharge performance The cut of the inner lead out end face, the foil strip

 riveted to the lead out end, and the cut of the electrode foil section will all have burrs, causing a short

 circuit between the opposing electrodes The expansion of the capacitor heating core and the pressure

 impact when the safety valve is opened cause deformation of the core, resulting in a short circuit

 between the electrodes The sealing capacitor component is sealed in a can In order to release 

hydrogen, the sealing ring is not sealed, it is often pressure sealed by rolling the edge of the can into 

a rubber gasket, a rubber end pin, or rolling into a rubber sheet pressed into stone carbonate If the

 seal is too tight, it will cause an increase in pressure; if it is too loose, the seal will shorten its lifespan

 due to the allowable loss of electrolyte

2. Capacitance Tolerance refers to the maximum and minimum allowable capacitance values, expressed

 as a percentage increase or decrease relative to the rated capacitance, i.e. Δ C/C. The temperature 

characteristics of capacitance are that capacitance changes with temperature The change itself is

 largely dependent on the rated voltage and the size of the capacitor The increase in capacitance from

 25 ℃ to the maximum temperature limit is less than 5% Most capacitors experience a rapid decrease

 in capacitance between -20 ℃ and -40 ℃. For products with a nominal -40 ℃ temperature, the 

capacitance of low-voltage capacitors typically decreases by 20% and high-voltage capacitors by 40% 

at -40 ℃ For capacitors with a rated temperature of -55 ℃, the decrease in capacitance value at -40 ℃

 is generally less than 10%, and the decrease in capacitance value at -55 ℃ is generally less than 20%

 The frequency characteristics of capacitance: The equivalent capacitance value decreases with

 increasing frequency According to the capacitance, the self resonant frequency is generally below 

100kHz The relationship between capacitance and voltage. For example, if we have a 20V 1.2F 

capacitor with a size of 3 × 8.63, and I want to replace it with a 400V capacitor of the same size, what 

is the capacity we choose? 1.2×(400/20)1.5=13000uF ---   0.013F@400V Namely: C1*V1^1.5＝

C2*V2^1.5 .

3. Rated DC voltage is the voltage indicated on the capacitor at rated DC voltage, which is the

 maximum peak voltage including ripple voltage. This voltage may be continuously supplied between

 terminals within the rated temperature range Capacitors with higher rated voltages may replace 

capacitors with lower rated voltages as long as their external dimensions, DF, and ESR ratings are 

compatible The working voltage, abbreviated as WV, should be the nominal safe value, which means

 that in the application circuit, it should not exceed this nominal voltage When electrolytic capacitors 

operate at voltages far below their rated operating voltage, the inability to obtain effective 

depolarization between the electrode and electrolyte can lead to polarization of the electrolytic 

capacitor, reducing ripple current and increasing ESR, resulting in premature aging However, the

 premise of this statement is that it is "far below the rated working voltage". Based on some long-term 

practical experience, it is reasonable to select about 2/3 of the nominal value of the rated working 

voltage as the normal working voltage Rated surge voltage is the maximum DC overvoltage that a 

capacitor can withstand at 25 ℃ for no more than 30 seconds with occasional intervals of no less than 

5 minutes Surge voltage measurement involves applying a rated surge voltage to a capacitor through

 a 1000 Ω± 10% resistor at normal room temperature (if the capacitance is 2500uF or higher, use a

 2500000/C Ω± 10% resistor, where C is the capacitance unit in uF) Cycle the voltage for 1/2 minute 

on and then 41/2 minutes off. When in the off state, each capacitor discharges through a charging 

resistor or equivalent resistor Repeat the cycle for 120 hours The necessary condition for announcing 

the test is to ensure that DCL, ESR, and DF meet the initial conditions and show no signs of mechanical

 damage or electrolyte leakage No droplets or visible flowing electrolyte residues are allowed 

Transient over voltage: Aluminum electrolytic capacitors can generally withstand very high transient 

overvoltages that limit energy Applications exceeding the rated surge voltage of 50V for capacitors

 will result in high leakage current and a fixed voltage operating mode similar to the reverse 

breakdown of a Zener diode If the electrolyte cannot withstand the voltage pressure, the capacitor

 may be damaged and short circuited. However, even if the electrolyte can withstand the voltage 

pressure, this operating mode cannot be maintained for a long time because the accumulation of 

hydrogen gas and pressure generated by the capacitor will cause damage

Redundant voltage aluminum electrolytic capacitors are charged first, then discharged, and the leads 

are short circuited. After being left for a period of time, there is a phenomenon of voltage rise between

 the two terminals; The voltage caused by this phenomenon is called regenerative voltage When a 

voltage is applied to a medium, it causes the transfer of electrons inside the medium, thereby generating an induced electric field inside the medium, which is opposite in direction to the voltage. This phenomenon is called polarization reaction After applying voltage to cause dielectric polarization, if the two terminals discharge until the voltage between the terminals is zero, and then leave it open for a period of time, a potential electric potential will appear on the two terminals, causing a regenerative voltage The regeneration voltage reaches its peak when the capacitor is left open for 10 to 20 days, and then gradually decreases. The regeneration voltage tends to increase with the size of the component If the two terminals of a capacitor short circuit after generating regenerative voltage, the instantaneous high-voltage discharge may cause fear among the operators on the assembly line, and there is a risk of some low-voltage driving components being broken down. The measures to prevent this situation are to apply a 100ohm~1Kohm resistor for discharge before use, or to cover the product packaging with aluminum foil to cause short-circuit discharge between the two terminals Polarity Reverse Voltage: During circuit design and installation, it is necessary to check the polarity of each capacitor The polarity will be indicated on the capacitor Although capacitors can withstand a reverse voltage of 1.5V continuously, exceeding this value can damage the capacitor due to overheating, excessive pressure, or medium damage This will cause associated open or short circuit faults and rupture of the capacitor pressure release port Charge Discharge aluminum electrolytic capacitors are not designed to charge and discharge frequently and quickly. Frequent and rapid charging and discharging can cause damage to the capacitor due to overheating, excessive pressure, or collapse, followed by open or short circuits For charging discharging applications, capacitors should be designed to not exceed the discharge rate recommended by the manufacturer Voltage Sharing During charging, the voltage of each series capacitor is proportional to the reciprocal of the actual capacitance But when the final voltage is reached, the voltage on each capacitor is proportional to the reciprocal of the leakage current of the capacitor Of course, all leakage currents on the series circuit are the same, and capacitors that tend to have higher leakage currents will receive relatively smaller voltages Because the leakage current increases with the increase of the provided voltage, lower voltage will cause higher leakage impedance, making the voltage tend to be the same Test the series capacitors on the high voltage bus, supply a voltage of 10% more than twice the rated voltage to the capacitors, and display good voltage distribution throughout the entire temperature range. No capacitor voltage has ever exceeded its rated value

The voltage derating is expressed as a percentage, which is the percentage of a given voltage that is less than the rated voltage. For example, a 450V capacitor operating at 400V will experience an 11% voltage derating Aluminum electrolytic capacitors made from aluminum foil with a conversion voltage at least 135% higher than the rated voltage and a rated or higher temperature of 85 ℃ do not require excessive voltage derating, and derating can sustainably increase the working life In applications, it does not require derating when operating at temperatures below 45 ℃ A 10% derating is sufficient above 75 ℃ For higher temperatures and higher ripple currents, a 15% or 20% derating is appropriate Military and space applications use a 50% voltage derating At normal room temperature, photoflash capacitors can be used at full rated voltage because they are designed for this purpose A voltage derating of at least 10% is beneficial for strobe capacitors, as their continuous operation will cause them to heat up

4. Operating Temperature Range refers to the ambient temperature range within which the capacitor is designed to operate continuously To a large extent, the formation voltage determines the high temperature limit value The low temperature limit value is largely determined by the low temperature resistance coefficient of the electrolyte The formation voltage at 105 ℃ level should be higher than 85 ℃ So capacitors with a temperature rating of 105 ℃ have a longer lifespan or higher ability to withstand ripple currents than capacitors with a temperature rating of 85 ℃

5. Ripple current Ripple current is the alternating current flowing into the capacitor The reason why it is called ripple current is because the AC voltage associated with it, which is attached to the DC bias voltage of the capacitor, travels like ripples on water Ripple current causes the capacitor to heat up, and too high a temperature rise will cause the capacitor to exceed its maximum allowable die temperature and quickly damage it. However, operating near the maximum allowable die temperature will greatly shorten the expected lifespan The maximum allowable ripple current depends on how much can be allowed and still meet the load life index of the capacitor The typical load life index for aluminum electrolytic capacitors operating at the maximum allowable die temperature is 1000 to 10000 hours That's six weeks to one year and seven weeks, which is too short for most applications Ripple current specification Ripple current is determined by obtaining the desired temperature rise at the rated temperature The allowable temperature rise for capacitors with a typical rated temperature of 85 ℃ is 10 ℃, and the maximum allowable die temperature is 95 ℃ The allowable temperature rise for capacitors with a rated temperature of 105 ℃ is 5 ℃, and the maximum allowable die temperature is 110 ℃ The rated value of ripple current usually assumes that the capacitor is cooled by convection, and the entire tank is in contact with air. The convection coefficient of 0.006W/℃/in2 is assumed that the temperature rise is from the air to the shell, and the core temperature is assumed to be the same as the shell temperature The power loss is equal to the square of the ripple current multiplied by ESR, (P=I (square) * R). The maximum ESR at 25 ℃ and 120Hz is usually used, but since ESR decreases with increasing temperature, a value lower than the maximum ESR can be used to calculate power loss Here is an example. For a 4700uF, 450V, 3-inch (76mm) diameter, and 55/8-inch (143mm) long can capacitor, its maximum ESR at 25 ℃ and 120Hz is 30m Ω. Assuming you want the ripple current rating of this capacitor The area of the can type - excluding the terminal end - is 60.1in2 (388mm2). The thermal conductivity is (0.006) (60.1)=0.36W/℃ For a temperature rise of 10 ℃, the shell may lose 3.6W So for a maximum ESR of 30m Ω, the allowable ripple current is 11A (3.6=I square x 0.03) A large can capacitor like the one in this example, ignoring the temperature rise from the shell to the core, will seriously exaggerate the capacity of ripple current Ripple current temperature characteristics indicate that the rated ripple current will increase when the operating temperature is below the rated temperature The increase will be displayed in the technical indicators The general increase is determined by the maximum die temperature (Tc), rated temperature (Tr), and ambient temperature (Ta), that is, the ripple temperature increment=[(Tc Ta)/(Tc Tr)] 1/2. A high ripple current will result in a shorter working life than expected, because the longer the capacitance time, the larger the ESR, which will increase the heat generation for the same ripple current This accelerates wear and tear When the operating frequency is not 120Hz, the rated ripple current should be calibrated based on the frequency characteristics of the ripple current The increase will be displayed in the technical indicators The usual increase is determined by the expected ESR with frequency, but as discussed above, ESR is a complex function of temperature, capacitance, rated voltage, and frequency So it is difficult to generate an accurate simulation of its frequency dependent ripple frequency increment table For applications with high ripple current, it is necessary to confirm the ESR at the frequency of interest and calculate the total power loss

The lifespan of electrolytic capacitors is also related to the ratio of the AC current during long-term operation to the rated pulse current (usually measured at an ambient temperature of 85 ℃, but some high-temperature resistant electrolytic capacitors are tested at 125 ℃) Generally speaking, the larger the ratio, the shorter the lifespan of the electrolytic capacitor. When the current flowing through the electrolytic capacitor is 3.8 times the rated current, the capacitor is usually already damaged So, electrolytic capacitors have their own safe working area. For general applications, when the ratio of AC current to rated pulse current is below 3.0 times, the requirements for lifespan have been met In fact, the variation range of d is between 5% and 20%, which causes the ripple current to be about 2-4 times larger than the DC output current of the capacitor The choice of D has a significant impact on capacitors, as a relatively small d value and high peak impulse point circuit can generate a relatively large ripple current value The relationship between ripple current and d can be seen in. According to the relationship between ESR and frequency, transforming d will result in energy consumption of the capacitor, which is proportional to the ripple current, or to the square of the ripple current, or to one of the two values Ripple current is an important parameter for the filtering circuit of stone machines The higher the ripple current Ira, the better His height is related to the working frequency, the higher the frequency, the larger the Irac, and the lower the frequency, the smaller the Irac Traditionally, it is believed that we need to have high ripple currents at low frequencies in order to achieve good high current discharge characteristics, making the low frequencies more robust, full, and elastic, as well as good control and driving characteristics; In fact, high ripple currents at high frequencies have a significant positive impact on the timbre, allowing for better extension and reduced roughness In our existing articles on filter capacitors, most of the recommended capacitors are Japanese made, such as elna, ruby, nichicon, and of course, Japanese chemical products. Since we have been exposed to these capacitors since we entered the market, we tend to assume that they are the best capacitors Of course, friends who play computer games have a broader perspective. They will never easily use these Japanese products, but will try their best to find European and American products Based on my years of practice, among the Japanese products mentioned above, except for a few ENLA varieties and European and American varieties that can be matched, the other varieties are not competitors to European and American products at all Among the filtering capacitors used in gallbladder machines, the Cornell Dubier from the United States performs well. Its diameter is 35mm and its height is twice that of Japanese products. However, the RIFA capacitor with the same withstand voltage has a diameter of 75mm and cannot be installed. The Cornell Dubier capacitor has two thicker terminals fixed by screws, while many Japanese products have four legs that are directly welded. Therefore, it is still difficult to replace them. I had to put in a lot of effort to replace the four filtering capacitors on my gallbladder machine

6. Equivalent Series Resistance (ESR) is a single resistance value that represents the Ohmic losses of all capacitors connected in series Used for input filtering capacitors in DC/DC switching power supplies. As the switching converter draws electrical energy to the power supply in pulse form, a large high-frequency current flows through the filtering capacitor. When the equivalent series resistance (ESR) of the electrolytic capacitor is large, significant losses will occur, causing the electrolytic capacitor to heat up Low ESR electrolytic capacitors can significantly reduce the heat generated by ripple (especially high-frequency ripple) current Electrolytic capacitors have a low ESR, which can effectively filter out high-frequency ripples and peak voltages in switch mode power supplies The level of ESR is related to the capacity, voltage, frequency, and temperature of the capacitor, and the lower the ESR requirement, the better When the rated voltage is fixed, the larger the capacity, the lower the ESR When the capacity is fixed, selecting varieties with high rated voltage can reduce ESR ESR is high at low frequencies, low at high frequencies, and high temperatures can also cause ESR to rise The measurement of ESR for aluminum electrolytic capacitors is to test the resistance value in an equivalent series circuit of a measuring bridge circuit at 25 ℃ as the ESR value. The measuring bridge circuit is powered by a 120Hz AC signal voltage of 1Vrms with no harmonic content and no forward bias voltage The temperature characteristics of ESR decrease with increasing temperature The ESR decreases by approximately 35% to 50% from 25 ℃ to the maximum temperature limit But at the minimum temperature limit, the increase in ESR exceeds 10 times For capacitors with a rated temperature of -20 ℃ or -40 ℃, the increase in ESR at -40 ℃ exceeds 100 times

The frequency characteristics of ESR, like DF, vary with frequency Rewrite the formula for DF above, ESR can be simulated using the following formula: ESR=10000 (DFif)/2 л fC+ESRrf is represented by ESR. At low frequencies, ESR steadily decreases with increasing frequency. The volume of the power supply is continuously reduced, and the energy conversion efficiency is continuously improved, resulting in an increase in the operating frequency of the switching power supply (from 20kHz to 500kHz, even exceeding 1MHz). This leads to an increase in high-frequency noise in its output part. In order to effectively filter, capacitors with ultra-low high-frequency impedance or low equivalent series resistance (ESR) must be used D. 3 Loss Factor - Dissipation Factor (DF) Tan&In an equivalent circuit, the ratio of the equivalent series resistance ESR to the capacitance 1/wC is called Tan&, and its measurement conditions are the same as the capacitance Tan&=R (ESR)/(1/wC)=wC R (ESR), where: R (ESR)=ESR (120HZ) w=2 X 3.14 f F=120Hz Tan&increases with increasing measurement frequency and decreases with decreasing measurement temperature The loss factor is the tangent value of the measured loss angle and expressed as a percentage The loss factor is also the ratio of ESR to capacitive reactance, and is therefore related to ESR, expressed by the formula: DF=2 л fC (ESR)/10000 DF is a numerical value expressed as a percentage without units. The unit of the test frequency f is Hz, the unit of the capacitance C is Uf, and the unit of ESR is Ω The DF measurement test was conducted at 25 ℃ using a 120Hz power supply with no harmonic content and a maximum AC signal voltage of 1Vrms without bias voltage The value of DF is related to temperature and frequency The temperature characteristics of DF show that the loss factor decreases with increasing temperature The DF decreases by approximately 50% from 25 ℃ to the maximum temperature limit, but increases by more than 10 times at the minimum temperature limit The DF value of better devices with a rated temperature of -55 ℃ increases by less than 5 times at -40 ℃

DF frequency characteristics The loss factor varies with frequency at high frequencies DF is simulated using the following formula: DF=DFif+2 л fC (ESRrf)/10000 DF is the total loss factor expressed in percentages, DFif is the low-frequency loss factor expressed in percentages, ESRrf is the ESR unit Ω at high frequencies, f is the test frequency unit Hz, and C is the capacitance unit uF at the test frequency DFif is caused by power loss, which is generated by the electric field in the molecular arrangement direction of the aluminum oxide medium ESRrf is caused by resistive losses on thin films, connectors, and electrolyte/isolation pads The resistance value on the electrolyte/isolation pad often plays a dominant role, and its resistance value changes very little with frequency The range of DFif is approximately from 1.5% to 3% The range of ESRrf is from 0.002 to 10 Ω, decreasing with temperature The formula for DF above indicates that DF is a constant at low frequencies, crossing over to a reduced DF and a fixed ESR at crossover frequencies, where the crossover frequency is inversely proportional to the capacitance Therefore, capacitors with high capacitance have lower crossing frequencies As the frequency increases, the capacitance DF of high capacitance decreases more than that of low capacitance Whether the DF value is high or low is related to temperature, capacity, voltage, frequency, etc; When the capacity is the same, the higher the withstand voltage, the lower the DF value The higher the frequency, the higher the DF value, and the higher the temperature, The higher the DF value DF values are generally not labeled on capacitors or in specification descriptions When selecting capacitors for DIY, it is advisable to prioritize those with higher voltage resistance. For example, when the operating voltage is 45V, choosing 50V is not very reasonable Although using 50V is not inappropriate in terms of normal operation under withstand voltage, it lacks some consideration in terms of DF value Using 63V or 71V withstand voltage will have better performance Of course, if it's any higher, it won't be cost-effective Inject electrolyte into Impregnation capacitor components, immerse paper separators, and penetrate into etched pipes The injection method may involve immersion of the device and application of vacuum pressure cycles, with or without heating, or simply absorption in small cell situations Electrolyte is a complex mixture of components represented by different formulas based on voltage and operating temperature range Its basic component is a salt with solubility and conductivity - a dissolved substance - to generate electrical conduction The common solvent is ethylene glycol (EG), Dimethylformamide (DFM) and microgram butyrolactone (GBL). Common dissolved substances are ammonium borate and other ammonium salts EG is typically applied to capacitors with a rated value of -20 ℃ or -40 ℃ DFM and GBL are often used for capacitors with a rated value of -55 ℃ Water plays a significant role in the electrolyte Water increases conductivity and therefore reduces the impedance of capacitance But it lowers the boiling point, which hinders high-temperature performance and reduces storage life A few percentage points of water is necessary because the electrolyte needs to maintain the integrity of the aluminum oxide dielectric When leakage current flows, water is decomposed into hydrogen and oxygen, and oxygen is attached to the anode metal foil to restore the leakage current location by adding more oxygen Hydrogen overflows through the sealing rubber of the capacitor

7. DC Leakage Current (DCL) DC leakage current refers to the direct current value that flows through a capacitor at a given rated voltage The value of leakage current depends on the given voltage, charging cycle, and temperature of the capacitor The dielectric of capacitors has a significant hindering effect on direct current Due to the presence of electrolyte on the aluminum oxide film dielectric, a small current called leakage current is generated during the re formation and repair of the oxide film when voltage is applied. At the beginning of voltage application, the leakage current is relatively large, and over time, it gradually decreases and eventually remains stable Testing temperature and voltage have a significant impact on residual current The leakage current will increase with the increase of temperature and voltage. The DCL method of measurement for leakage current is to provide rated voltage at a temperature of 25 ℃ and connect it in series with a capacitor in the measurement circuit through a 1000 Ω protective resistor After applying voltage for 5 minutes, the leakage current did not exceed the maximum value specified in the specifications Aluminum electrolytic capacitors all have leakage, which is determined by their physical structure The smaller the leakage current, the better The higher the capacitance of a capacitor, the greater the leakage current Lowering the operating voltage can reduce leakage current Choosing varieties with higher voltage resistance can also help reduce leakage current Prioritizing the selection of high pressure resistant varieties under the same conditions is indeed a simple and feasible method; Reduce internal resistance, decrease leakage current, reduce loss angle, and increase lifespan There are many benefits, but the price will be higher The control of leakage current value is the key among the three parameters of capacitors, and the leakage current value is an important indicator for judging the quality of capacitors The main factors affecting the leakage current value of aluminum electrolytic capacitors are: (1) the purity of the raw materials used, including the impurity content of the positive electrode foil, the purity of the negative electrode foil, the purity of deionized water, the impurity content of the electrolytic paper, and other structural materials, sealing materials, etc (2) The composition and viscosity of the working electrolyte P H value, specific resistance (3) The impact of work and storage environment (4) The control of the production environment and manufacturing process of capacitors, especially the aging process and the repair process of the internal oxide film of capacitors Charge electrolytic capacitors of the same capacity according to the rated withstand voltage, let them stand for a period of time, and then check the degree of voltage drop at both ends of the capacitor The less voltage drop, the smaller the leakage current

The temperature characteristics of DCL increase with temperature. The DCL method of measurement for leakage current is to provide rated voltage at a temperature of 25 ℃ and connect it in series with a capacitor in the measurement circuit through a 1000 Ω protective resistor After applying voltage for 5 minutes, the leakage current did not exceed the maximum value specified in the specifications Charge electrolytic capacitors of the same capacity according to the rated withstand voltage, let them stand for a period of time, and then check the degree of voltage drop at both ends of the capacitor The less voltage drop, the smaller the leakage current The voltage characteristics of DCL: The value of leakage current decreases rapidly as the supplied voltage decreases

External pressure has no correlation with the capacitance of solid electrolyte Aluminum electrolytic capacitors can operate at 80000 feet (20320 meters) and a low pressure of 3 kPa The maximum air pressure depends on the size and type of capacitor Exceeding the maximum value will damage the capacitor by crushing the casing, opening the pressure release port, or creating a short circuit circuit

Inductance is an equivalent series inductance that is relatively independent of temperature and frequency The typical range for SMT is from 2 to 8nH, for radial lead types it is from 10 to 30nH, for screw terminal types it is from 20 nH to 50nH, and for axial lead types it is as high as 200nH These low values are obtained through the inherent low inductance of the table area and dielectric contact geometry Capacitive components have a typical inductance of less than 2nH The simple calculation formula for CDE inductance is: (diameter/2)+5<inductance (nH)<diameter -8

10. Insulation and Grounding: The aluminum shell of a non solid electrolyte aluminum electrolytic capacitor is connected to the negative electrode through contact with the electrolyte The insulation resistance generated ranges from a few ohms to several thousand ohms For capacitors with axial terminals and flat component packaging shells connected to the negative terminal If the device in contact with the casing has a certain level instead of a negative terminal, use a capacitor with an insulating sleeve Plastic insulation (UL224VW-1) can withstand 3000Vdc or 2500Vac, 60Hz for 1 minute, with voltage applied between the casing and a 1/4 inch wide metal film surrounding the insulation sleeve Install satisfactory nylon nuts and spacer holes on the capacitor After applying 100V between the film and the capacitor casing for 2 minutes, the insulation resistance shall not be less than 100M Ω

At rated temperature, the difference in leakage current between two capacitors connected in series can be estimated to be 0.0015CVr in uA, C in uF for rated capacitance, and Vb in Vdc for voltage across the two capacitors Using this estimated value, use the following formula to select the balanced resistance value for each capacitor R=(2Var Vb)/(0.0015CVr) R makes the unit of balanced resistance M Ω, Vr is the maximum voltage you want to apply to each capacitor, and Vb is the maximum bus voltage across two capacitors For three or more capacitors connected in series, the following formula can be used, where n is the number of capacitors connected in series: When two capacitors are connected in series, balancing resistors are rarely used for voltage distribution Before using balanced resistors for voltage discharge, it should be considered that not using balanced resistors usually increases the reliability of the system because not using balanced resistors can lower the temperature around the capacitor. Removing components with lower reliability than capacitors means protection As an alternative, use a batch of capacitors from the same production to ensure the same leakage current or use a higher rated voltage to allow for uneven voltage distribution among capacitors from different manufacturers Ensure that the capacitors connected in series have the same thermal environment

Storing aluminum electrolytic capacitors with a lifespan of 5 to 10 years or more in Self Life may increase DC leakage current Before use, check if DCL meets the requirements of the application Re limit the conditions for high DCL individuals by applying a 1000 Ω resistor and a rated voltage for 30 minutes Storage life is a measure of how a capacitor maintains long-term storage, especially at high temperatures To test the storage life, place the capacitor in a furnace and set the storage life test temperature to -0+3 ℃ as the storage life test cycle Complete the experiment to stabilize the capacitor at 25 ℃ for 24 hours or longer Provide rated voltage for 30 minutes and confirm the limit value after testing If there are no other indicators, the electrical capacity, DCL, and ESR will meet the initial requirements (1) Store indoors at a temperature of 5-30 ℃ and humidity below 75%. (2) Do not store in environments or under equivalent conditions that are prohibited during assembly and use

13. Bus Structure When capacitors are connected in parallel, these characteristics should be used in mind to design the connection bus The minimum series inductance requires a thin busbar or strip structure For example, use one part of the circuit board to connect the positive terminals of all capacitors, and use another part to connect the negative terminals of all capacitors The line impedance for each capacitor will be equal to ensure the same current diversion Although for low-frequency ripple, the distribution of ripple current between capacitors is proportional to the value of capacitance, the distribution of high-frequency ripple current is proportional to the value of ESR and line impedance

14. Vibration: Aluminum electrolytic capacitors can generally withstand a vibration force of 10g Limit values will be provided in the technical specifications Adjust the process to make the vibration force smaller than the value required by a single type of technical indicator To test the vibration impedance, the capacitor is fixed on the vibration platform to withstand a simple harmonic motion, with a maximum peak to peak amplitude of 0.06 inches and a maximum acceleration of 10g or 15g depending on the given value Linearly change the vibration frequency between 10 and 55 Hz Pass through the entire frequency range within 1 minute Unless otherwise specified, vibrate the capacitor in a direction parallel to its axis for 1.5 hours, then place the capacitor so that its direction of motion is perpendicular to the axis, and continue vibrating for another 1.5 hours During the final 1.5 hours of testing, connect the capacitor to the rectifier bridge and observe a 3-minute cycle In the following experiment, when shaken by hand, there will be no significant looseness of the capacitive element inside the container Of course, during the 3-minute observation period, there were no signs of intermittent connections or short circuits in the capacitors

15. Self resonant frequency refers to the frequency at which the capacitive impedance (1/2 л fC) equals the inductive impedance (2 л fL) Because at this frequency, the phase difference between capacitive impedance and inductive impedance is 180 degrees. Subtracting the two reactances, the remaining impedance is purely resistive and equal to ESR Devices above the self resonant frequency are inductive The self resonant frequency of aluminum electrolytic capacitors typically occurs below 100kHz The self resonant frequency is equal to 1/[2 л (LC) ^ 1/2]. Based on a 120Hz capacitor, the self resonant frequency is higher than the expected frequency because the capacitance decreases with increasing frequency, and increasing temperature prevents the decrease in capacitance, so it decreases with increasing temperature

16. When the pressure relief vent is used in aluminum electrolytic capacitors with non solid electrolyte, the gas pressure generally increases Most of this gas is hydrogen, which can be sealed through a capacitor to avoid excessive pressure However, excessive pressure in the event of overvoltage, reverse voltage, AC voltage, or capacitor damage can cause capacitor explosion In order to avoid explosion, aluminum electrolytic capacitors are often equipped with pressure relief port structures These safety release ports are designed to release gas pressure After the capacitor cracks, its lifespan is limited because it loses the electrolyte, causing it to dry out Be careful not to affect the operation of the release port, such as some installation methods such as clamping, gluing, or sealing components For large capacitors protected by thermoplastic can seals, do not install them under the safety port, as the can seal may flow and block the safety port when the capacitor overheats In rare cases, capacitors are installed separately. For capacitors, in most cases, multiple parallel capacitors play a complete role, and the pressure relief device may not function in a timely manner This will avoid causing extreme overload or sparking the gas inside the capacitor due to damage When testing the pressure release port, use a protective cover to protect personnel from potential damage caused by high-energy capacitors, and ensure the use of a sturdy protective cover An example of a suitable protective cover for testing is a 1/4 inch thick steel plate or 1/2 inch thick polycarbonate wrapped around it, with one side open to change the direction of the explosion instead of surrounding it Use one of the following three methods to test the pressure release capability of a capacitor by supplying voltage or current A. According to the rated capacitance, the capacitor can withstand AC current as follows: rated capacitance test current Uf A rms, 60Hz up to 3000 1 to 100 3000 to 20000 85 to 150 higher than 20000 100 to 175 B. For rated voltage of 150Vdc or higher, a series connected 5 Ω± 10% current limiting resistor is used to supply power from 110 to 125Vac, 60Hz C. It is a capacitor that can withstand a DC voltage of opposite polarity, allowing it to flow a current ranging from 1 to 10A Excessive internal pressure will be released without causing severe damage to capacitor components or seals, or igniting surrounding materials To prove that there was no ignition, two layers of cheese cloth were loosely wrapped around the outer shell, and the fabric was not ignited during testing Short circuit or open circuit is not a test fault

17. Installation position: In low-temperature environments, aluminum electrolytic capacitors have a relatively long lifespan; So, place the aluminum electrolytic capacitor on the coldest part of the printed board Ensure that aluminum electrolytic capacitors are kept away from hot components such as power resistors, power transistors or diodes, and transformers Separate the components thoroughly to allow for the circulation of cold air This is particularly important when the provided ripple current or charging/discharging load is high Please follow the following instructions during installation: a. In order to perform point testing on capacitors and measure electrical performance, please do not use capacitors that have been installed in the machine and passed through electricity, except for removing the capacitors; b. When a capacitor generates regenerative voltage, it needs to be discharged through a resistor of about 1KOHM; c. Long term guaranteed capacitors need to be pressurized with a resistance of about 1Kohm; d. After confirming the specifications (electrostatic capacity, rated voltage, etc.) and polarity, proceed with installation; e. Do not let the capacitor fall to the ground, and do not use the fallen capacitor again; f. Do not install deformed capacitors; g. The distance between the positive and negative electrodes of the capacitor must match the distance between the holes on the circuit board; h. The mechanical arm of the automatic insertion machine should not have excessive force; ② When welding, please confirm the following: a. Be careful not to attach solder outside the terminals; b. The welding conditions (temperature, time, frequency) must be executed according to the specified time; c. Do not immerse the capacitor itself in soldering solution; d. When welding, do not let other products fall and touch the capacitor; ③ The processing after welding should not generate the following mechanical stresses: a. The capacitor tilts; b. The capacitor touches other circuit boards; c. Make other objects touch the capacitor; ④ Do not clean capacitors with cleaning agents. However, if cleaning is necessary, capacitors must be cleaned within the range specified in the product specification manual For capacitors that must be cleaned, the following must be determined during cleaning: a. Cleaning agent pollution management (conductivity, pH value, specific gravity, moisture, etc.) b. After cleaning, it cannot be stored in a cleaning solution environment or a closed container. Printed circuit boards and capacitors should be dried with hot air (below the highest operating temperature) to prevent residual cleaning solution components. ⑥ Do not use halogen containing fixatives or resin coating agents. ⑦ When using fixatives and coating agents, please confirm the following: a) There should be no welding residue or dirt left between the circuit board and the capacitor; b) Before the adsorption of fixatives and coating agents, try to minimize the residue of cleaning ingredients and dry the printing holes to prevent blockage;

About Us

Guangdong Fulong Electronic Technology Co., Ltd. is a private high-tech enterprise specializing in the research and development, manufacturing, and sales of aluminum electrolytic capacitors, certified by IATF16949，ISO9001, ISO14001, and ISO45001. The company has a building area of 17000 square meters and more than 50 automated production lines; The total investment is 50 million yuan (RMB), with more than 100 employees, including more than 20 engineering and technical, quality management, and production management personnel. The annual production of capacitors (4 * 5.4~16 * 21.5) is about 400 million pieces; Our products are mainly sold to domestic and international markets, and we strive to promote our company's products globally.

Jiangxi Fulong Electronic Technology Co., Ltd. is a wholly-owned subsidiary of Guangdong Fulong Electronic Technology Co., Ltd. established in Hukou County, Jiangxi Province with a total investment of 500 million yuan. It has 50 fully automated production lines and an annual output of approximately 1.2 billion capacitors (4 * 5.4~16 * 21.5).

Fulong Group has an international professional core technology research and development team for aluminum electrolytic capacitors and a global sales network. Rich experience in the design, research and development, and production management of aluminum electrolytic capacitors. The R&D team follows the technical design theory of aluminum electrolytic capacitors, complies with international and domestic legal and regulatory requirements (RoHs), and adheres to the highest international quality standards

Fulong Group has high-quality and stable raw material supply partners, and key raw materials (such as aluminum foil, electrolytic paper, etc.) are selected from well-known Japanese and Korean companies (KJCC KDKNKK, etc.), ensuring reliable and stable advantages in product quality, environmental protection, safety, and energy conservation.

Fulong Group has a group of highly qualified professional technicians and management personnel who can produce various series of sheet aluminum electrolysis products according to customer requirements. The products include high-frequency low impedance, low leakage, wide temperature, extremely low impedance, non-polar, ultra long life, medium high voltage long life, high reliability and other new types of special requirements for surface mount products; At the same time, the company's products can withstand a soldering temperature of 260 ℃, meeting the lead-free reflow soldering technology required for SMT in the whole machine factory. All technical indicators of the products have reached or exceeded the international level of similar products.

While strengthening management and expanding operational scale, Fulong Group is also committed to improving its competitiveness and customer satisfaction, continuously and steadily increasing customer and social trust, continuously meeting market demand, further optimizing environmental management and expanding social contributions, and developing together with the electronics industry.

Guangdong Follon Electronic Technology Co., Ltd.

Jiangxi Follon Electronic Technology Co., Ltd.

Address: Building 3, South District, Haishan Science and Technology Park, Hukou County, Jiujiang City, Jiangxi Province

www.follon.com

Professional manufacturer of high-quality surface mount electrolytic capacitors