The failure of film capacitors can be the failure of normal use, and the probability of such failure is extremely low, and generally small batch applications may not be considered.

Except for the very low probability of failure in normal use, the most common failures of film capacitors are caused by improper application, such as overvoltage, overcurrent, and overheating.

🪐2. Overvoltage failure

(1). The main reason for the failure of film capacitors due to overvoltage: The probability of failure due to overvoltage increases, and the probability of failure increases by an order of magnitude for every 50K increase in temperature.

(2). Failure due to dielectric breakdown due to overvoltage: the main reason is that the actual rated voltage of the capacitor does not match the nominal voltage of the capacitor. For example, change a capacitor with a rated voltage of 400V to a capacitor with a rated voltage of 630V. Since the test voltage of the film capacitor is generally 1.7 times the rated voltage, and the dielectric strength is higher than the test voltage, it is generally not a problem to use a film capacitor with a rated voltage of 400V as a 630V film capacitor, unless the capacitor’s dielectric strength is tested before application. Electric strength, then divide this value by 2~2.5 to get the rated voltage of the capacitor.

(3) The most common overvoltage failure may be the failure of the film capacitor due to the overvoltage occurring in an abnormal state. The situation may occur when the electronic ballast is working in an abnormal state, the overvoltage generated on the ignition capacitor; the ordinary capacitor as a power supply electromagnetic interference suppression capacitor will cause the capacitor to fail when the power supply voltage has a severe overvoltage or surge voltage.

For the ignition capacitor of the electronic ballast, in the normal working mode, the ignition capacitor only bears the ignition voltage of the lamp within a short period of time when the lamp is ignited. If it is preheating, the peak voltage of the device will not be higher than 630V. However, when the fluorescent tube cannot be ignited and the filament is not broken, the ignition capacitor will resonate with the ballast inductance to generate a high-amplitude resonant voltage, which can easily exceed 1000V. Under the conditions of both high temperature and high frequency, the overvoltage breakdown of thin film electrical appliances can be achieved within a few minutes.

If general-purpose film capacitors are used as capacitors for suppressing electromagnetic interference of power supplies, they cannot pass the instantaneous overvoltage and surge voltage tests in the form of electromagnetic compatibility experiments. Even if the form of electromagnetic compatibility experiment is not carried out, in actual operation, it may fail due to the accidental surge voltage or instantaneous overvoltage in the power grid.

🪐3. Overheating failure when the ambient temperature is too high

From the relationship between the failure rate and the temperature and the relationship between the rated voltage and the temperature, it can be known that an excessively high ambient temperature will lead to an increase in the failure rate of the film capacitor. Because the temperature is too high, the organic dielectric film of the capacitor can be softened or even melted, and the insulation performance will be deteriorated at the same time.

For paper dielectric capacitors, boiling of the immersed capacitor oil or carbonization of the capacitor paper may result in the failure of the paper dielectric capacitor. Even if the temperature does not reach the temperature at which the capacitor oil boils or the capacitor paper is carbonized, an excessively high temperature will increase the capacitor oil Evaporation rate, resulting in a decrease in the capacitance and dielectric strength of the paper dielectric capacitor, leading to failure.

As the temperature increases, the insulation resistance of the medium decreases, which increases the leakage current and increases the probability of capacitor failure.

🪐4. Overheating failure due to overcurrent

Failure due to overcurrent and overheating is a common failure mode for film capacitors. The reason for this failure mode is that due to the limited effective area of the electrode of the film capacitor, the equivalent series resistance of the electrode cannot be ignored. When an excessively high current flows through the capacitor, the excessively high current generates a relatively large loss in the equivalent series resistance of the electrode and causes excessive heating, which in turn causes the film capacitor to enter an overheating failure mode, which causes the film capacitor to fail. The reasons for this phenomenon are:

(1). Most of it is caused by improper selection of capacitors. For example, the “breakthrough” absorption capacitors in switching power supplies or frequency converters choose general-purpose capacitors, and the resonance capacitors of power resonant circuits choose general-purpose capacitors to generate high power. The bypass of the circuit ripple current circuit uses general purpose capacitors, etc.

(2). The circuit entering an abnormal working state can also cause the capacitor to overcurrent and overheat. For example, when the excessive harmonic current in the power grid flows into the power factor compensation capacitor, it will compensate the capacitor overcurrent and overheat; the fluorescent lamp cannot start, so that the electronic ballast enters the ballast inductance and the ignition capacitor in series resonance, and the flow rate The normal current is much larger than the resonant current, which causes the capacitor to overcurrent and overheat. In resin-encapsulated capacitors, this failure can be seen to cause the resin-encapsulated capacitor to explode at the terminal.

.In the design, due to insufficient pre-estimation, the current of the capacitor in the actual circuit is higher than the rated current of the capacitor, resulting in overheating failure due to excessive current.

🪐5. Overcurrent failure due to rapid discharge

Although in theory the capacitor can be short-circuited and discharged, in practice, due to the limited current-carrying capacity of the capacitor electrode, it is not allowed to charge or discharge with a very high current value, especially the circuit discharge. The reason is that when a sharply discharged high-amplitude current flows through the entire conductive part of the capacitor, it will cause the weakest part of the conductive capacity to blow like a fuse. The part between the electrode of the capacitor and the terminal is the weakest part of the capacitor’s sharp discharge. Therefore, in this type of failure, the part between the electrode and the terminal is often damaged.

The replacement of the capacitor in the camera flash with a general-purpose electrolytic capacitor will also cause the internal lead to be burned or other types of failure due to the rapid discharge current.

Therefore, in applications requiring rapid discharge of the capacitor, the capacitor should be a “pulse” capacitor dedicated to rapid discharge. Such capacitors allow peak discharge currents of up to 10,000A or even higher.

🪐6. Too high dv/dt overcurrent failure

From the relationship between capacitor voltage and current:

Can get：

The following phenomena may occur:

(1). In the frequency converter, the rate of change of the Vce of the IGBT during the turn-off process can reach a voltage change rate of hundreds of volts or even thousands of volts per microsecond. If the snubber capacitor connected to the collector and emitter of the IGBT has a capacitance of 1μF, the current peak value will reach hundreds or even thousands of amperes [A]. From this result, it can be seen that the snubber capacitor of the IGBT must be able to withstand the very peak current impact.

(2) Such a high rate of voltage change will also occur in the buffer circuit of the switching power supply switch tube. For example, a 1000pF buffer capacitor has a voltage change of 1000V/μs during the switch-off process, and the corresponding peak current flowing through the capacitor is 1A.

(3) The snubber capacitor of the thyristor inverter also has the problem of high peak current impact. If the snubber capacitor is replaced with a general-purpose capacitor, the snubber capacitor will be damaged due to overheating after a short operating time.

🪐7. Failure of improper mechanical stress

Improper mechanical stress is a common phenomenon of capacitor damage. For example, if the length of the pins of the capacitor inserted on the circuit board is too short, the capacitor pins will be improperly stressed due to thermal expansion and contraction. In the long run, the capacitor pins and capacitor ends will break and become invalid. Therefore, the pins of many capacitors are deliberately bent at the roots when they leave the factory to reduce improper application of force.

In terms of the assembly of the capacitor, the stress of the capacitor pin when inserted into the via hole of the circuit board should be as small as possible, and the method of pre-bending the leg to a suitable size can be used.

🪐8. Low-level failure mechanism of high-frequency precision capacitors

Among many organic film capacitors, polystyrene film capacitors have the advantages of low loss, large insulation resistance, good stability, and high dielectric strength. Precision polystyrene capacitors can be used in high-frequency circuits instead of mica capacitors. It should be noted that precision polystyrene capacitors used in high-frequency circuits generally use metal foil plates to improve insulation resistance and reduce losses.

Low-level failure of capacitors is a new problem that has emerged since the 1960s. Low-level failure refers to the failure of capacitors such as open circuit of capacitors or excessive drop in capacity under low voltage working conditions. Since the 1960s, semiconductor devices have been widely used. The voltage of semiconductor circuits is much lower than that of electronic tube circuits. The actual working voltage of capacitors is only a few millivolts in some circuits. If the capacity is live or partly loses the capacity, with a low level impact, the capacity of the capacitor can be restored to normal.

The main reason for the low-level failure is that the lead wire of the capacitor is in poor contact with the capacitor plate, and the contact resistance increases, resulting in a complete open circuit of the capacitor or a decrease in capacitance.

Precision polystyrene film capacitors generally use aluminum foil as the pole plate, and the copper lead wire and the aluminum foil pole plate are spot welded together. Aluminum foil is easily oxidized in the air; a layer of aluminum oxide semiconductor film is formed on the surface of the electrode plate, and the voltage on the oxide film layer under low-level conditions is not enough to break it down, so the gap capacitance formed between the aluminum foils is equivalent in series The capacity, the gap capacitance is smaller, and the series equivalent capacity is also smaller. Therefore, the low-level capacity depends on the thickness of the aluminum oxide layer on the surface of the electrode plate. The thicker the aluminum oxide layer, the smaller the capacitance of the capacitor under low-level conditions. In addition, when the capacitor is working in an AC circuit, its effective capacitance will decrease due to excessive contact resistance. When the contact resistance is large, the effective capacitance can be reduced to the extent of an open circuit, even if there is no poor conduction gap between the plate and the lead. Layers, will also produce these consequences.

The specific factors that cause the low-level failure of precision polystyrene capacitors are summarized as follows:

(1). The lead surface is oxidized or the dip layer is too thin, so that the welding is not strong.

(2) The lead wire and the aluminum foil are poorly welded, and the aluminum oxide film layer at the spot weld on the surface of the aluminum foil is not eliminated.

(3) The number of solder joints of the single-lead structure is too small, which increases the probability of low-level failure.

(4) Although the contact area of the flattened part at the root of the thick lead is larger, the stress at the solder joint after spot welding is also larger. During the heat treatment or temperature cycle, the contact part may be damaged and the contact condition may be deteriorated.

(5) Moisture enters the capacitor core, oxidizes and corrodes the solder joints, and increases the contact resistance.

The specific factors that cause the low-level failure of mica capacitors are summarized as follows:

(1). There is a thin layer of ground wax film between the silver electrode and the copper foil, and between the copper foil and the lead card. Under low-level conditions, the applied voltage is not enough to break down the insulating film, resulting in gap capacitance , And increase the contact resistance.

(2). The silver electrode and copper foil are corroded by harmful gases, which increase the contact resistance. In a humid sulfur environment, silver and copper are easily vulcanized, which increases the contact resistance between the electrode plate and the lead.

🪐9. Failure mechanism of metallized paper capacitor

The electrode plate of a metalized paper capacitor is a metal film that is vacuum evaporated on the surface of the capacitor paper. Due to the extremely thin thickness of the metalized film, a point parameter deterioration and failure may occur in the metalized film capacitor, and lead breaks and failures may occur.

(1). Deterioration of electrical parameters and failure. “Self-healing” is a unique advantage of metallized capacitors, but the self-healing process is quite complicated. Although self-healing can prevent the capacitor from breaking down due to dielectric short-circuit, the self-healing part will definitely cause metal particle migration and thermal cracking of the dielectric material. The phenomenon. Capacitor paper is composed of fibers, and cellulose is a high molecular weight substance of carbohydrates. At high temperatures, the capacitor cellulose decomposes into free carbon atoms or carbon ions, which increases the surface conductivity of the self-healing part, resulting in a decrease in the resistance of the capacitor, an increase in loss and a decrease in capacitance. In severe cases, the capacitor may become invalid due to the deterioration of the electrical parameters exceeding the allowable range of the technical conditions.

When metallized paper dielectric capacitors work below the rated operating voltage, the self-healing energy is insufficient, and the conductive impurities stored in the capacitor paper form a low-resistance path under the action of the electric field, which can also cause the capacitor’s insulation resistance to decrease and the loss to increase .

Capacitor paper is a porous polar organic dielectric material that easily absorbs moisture. Although the capacitor core has been immersed, if the process is improper or impure, or immersion aging occurs after a long period of work under the action of an electric field, the insulation resistance of the capacitor will be reduced and the loss will therefore increase.

Capacitance out-of-tolerance failure is a failure form of metallized paper capacitors. Metallized paper capacitors may fail due to excessive increase in capacitance when stored under high temperature conditions, and may fail due to excessive decrease in capacitance when operating under high temperature conditions. Semi-hermetic metallized paper dielectric capacitors will inevitably absorb moisture when stored at high temperatures. Water is a strong polar substance, and its dielectric constant is close to 20 times the dielectric constant of an impregnated capacitor. Therefore, a small amount of moisture invades the capacitor core, which will also cause a significant increase in capacitance. The electric capacity will decrease after baking and dehumidification. If the capacitor works in a high-temperature environment, the combined action of moisture and electric field will cause electrolytic corrosion of the metal film electrode, reducing the effective area of the electrode plate and increasing the resistance of the electrode plate, resulting in a substantial decrease in capacitance. If corrosion occurs at the contact part of the lead wire and the metal film layer, the contact resistance will increase and the effective capacitance of the capacitor will be further reduced. The capacitance of individual capacitors can be reduced to close to an open circuit.

(2) The lead breaks and fails. When metallized paper capacitors work in a high-humidity environment, the root of the positive terminal lead of the capacitor will be severely corroded. This electrolytic corrosion leads to a decrease in the mechanical strength of the lead, and in severe cases, the lead may break and fail.

The post Film capacitors failure analysis and countermeasures？ appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

💡The main factors that affect the capacitor failure rate during application are operating temperature and operating voltage. The relationship between the failure rate of different media and the operating voltage is shown in Figure 2.22~Figure 2.26. They are paper capacitors, polyethylene capacitors, polyester capacitors, The relationship curve of the failure rate of polypropylene capacitors and polyphenylene sulfide capacitors with operating temperature and operating voltage.

💡The ordinate in the figure shows the failure rate per billion hours, and the abscissa is the operating temperature. The five curves/slashes in the figure are the relationship between the capacitor failure rate and the operating temperature at 1.5 times the rated voltage, and 1.25 times the rated voltage. The relationship between the failure rate of the capacitor and the operating temperature, the relationship between the failure rate of the capacitor and the operating temperature at 0.75 times the rated voltage, and the relationship between the failure rate of the capacitor and the operating temperature at 0.5 times the rated voltage.

⭕️First, the failure rate increases with the increase of operating temperature. The failure rates of Evox-Rifa’s paper capacitors, polyester capacitors, polyester capacitors, and polyphenylene sulfide capacitors under rated voltage working conditions increase with temperature. 1.5 100, 1000, 15000, 3000 when it rises to 105℃.

⭕️The increase of the operating voltage at the same operating temperature will also lead to the increase of the failure rate. At room temperature (30°C), when the working voltage is 0.5VR, 0.75VR, 1VR, 1.25VR, 1.5VR, the corresponding failure rates per billion hours are 0.08, 0.6, 3, 8, 30 for paper capacitors, respectively. Ethyl capacitors 0.25, 2.5, 12, 40, 130, polyester capacitors 0.4, 4, 20, 80, 220, polypropylene capacitors 0.1, 1, 6, 20, 60, polyphenylene sulfide capacitors 0.05, 1, 7, 30, 100. Therefore, in normal applications, the overvoltage use of capacitors should be avoided as much as possible.

🎈It can be seen from Figures 2.22~2.26 that the paper dielectric capacitor has the lowest failure rate among the above five dielectrics, which is one-tenth of that of polypropylene dielectric capacitors and one of the highest among polyphenylene sulfide capacitors, polyethylene capacitors, and polyester capacitors.

The post The relationship between capacitor failure rate and application conditions? appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

✨“Self-healing”: The vacuum deposition metal attachment directly attached to the plastic film is only 20-50mm. If there are weaknesses, defects or the dielectric strength of the insulator in the mixture in the insulator is exceeded, the insulator will be broken down. The arc-shaped discharge of energy in the fading channel can evaporate all the thin metal outer layers passing nearby. The rapid extension of the plasma in the fading channel cools it in tens of milliseconds, and the discharge ends. In this way, the insulating area allows the previously imperfect area of the capacitor to regain the full performance of the capacitor.

✨Since the loss of any form of pressure in the respective insulating layer and a good homogeneity improve the self-healing ability, a capacitor with a good surface layer has better self-healing performance than a capacitor with a damaged surface layer.

🌟Metal-coated capacitors have many advantages, and these advantages are particularly obvious in the large rated capacity.

✨Because of the metal-coated design, it can also be applied to some more complex capacitor designs. For example, it is used to handle multiple internal series couplings of high DC voltages and high AC loads.

✨In capacitors that require high current pulses and high di/dt, the combined application of metal foil, metal film and metal-free film can be used to make the capacitor carry extremely high current and self-healing.

The post What are the advantages of metal film capacitors？ appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

⭐️The dielectric coefficient of capacitor paper is about 2.2. Because it is made of plant cellulose, it is porous, and generally contains 20% to 35% (volume) of air and 5% to 7% (weight) of moisture. Therefore, when manufacturing capacitors, drying and immersion must be carried out to remove moisture. Dipping is usually filled with liquid (capacitor oil) or solid (paraffin) with high dielectric coefficient and dielectric strength to improve dielectric coefficient and dielectric strength.

✨Advantages of paper dielectric capacitors:

The capacitance and working voltage range is very wide, the process is simple, the cost is low, and it is easy to metalize. The current paper medium is usually combined with an organic medium to take full advantage of the good metallization performance of the paper medium to make a capacitor with excellent performance such as a double-metallized capacitor.

⚡️The disadvantages of paper dielectric capacitors are:

The purity of the capacitor oil or paraffin determines the insulation resistance of the paper dielectric capacitor. Once the capacitor oil is acidified or other factors that cause the insulation resistance to decrease, the insulation resistance and dielectric strength of the paper dielectric capacitor will be destroyed.

Since the capacitor paper is a porous plant fiber, even if it is impregnated with capacitor oil or paraffin, the non-porous metalized electrode may cause some weaknesses of the capacitor, although the self-healing performance of the metalized electrode can eliminate the weakness of the metalized capacitor when a local breakdown occurs. However, the insulation resistance of metallized paper dielectric capacitors is generally lower than that of organic film metallization.

⭐️In spite of this, paper dielectric capacitors are still used in a large number of applications. The main reason is that paper dielectric is most suitable for metallized electrodes. In other words, various dielectric film metallized electrodes, and paper dielectric metallized electrodes have the best quality. Moreover, the paper media film does not become soft at high temperatures is another advantage of paper media.✨

The post Characteristics of paper dielectric film capacitors appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

❓What is the relationship between dissipation factor and frequency?

✨If the inductive reactance Ls is not considered, for ƒ <ƒt (where ƒt is the resonant frequency), the equivalent circuit of the capacitor shows that the disipation factor tanδ is the loss factor tanδp of the parallel resistance part, the disipation factor tanδs of the equivalent series resistance part, and the insulation The disipation factor tanδd of the dielectric part is formed. In this way, the overall disipation factor of the film capacitor is

Tanδ = tanδp + tanδs + tanδd

Among them,

And tanδd is the characteristic of the medium itself.

✨Because the diffipation factor of the parallel resistance part is relatively small, it is negligible in the entire frequency range, because due to the existence of insulation resistance (parallel resistance Rp), even at very low frequencies (ƒ<<1kHz), tanδp, In fact, it has no obvious effect on the entire dissipation factor. Therefore, the dissipation factor Tanδ at low frequencies is only determined by the insulation component tanδd. For small-capacity polypropylene film capacitors, before the frequency rises to several MHz, the dissipation factor is almost independent of frequency, about 0.0001.

✨However, as the frequency increases (ƒ>1kHz), the equivalent series resistance (ESR) part of the dissipation factor Tanδs (proportional to the capacitance) increases rapidly, until it becomes the decisive component of the dissipation factor curve, Figure 1.15 is 1nF And the dissipation factor of the polypropylene film capacitor of 100nF, the relationship between the dissipation factor of the equivalent series resistance and the frequency can clearly see this conclusion. The equivalent series resistance part is the sum of the connection resistance (terminal), wire resistance, metal layer and electrode foil resistance.

☀️The relationship between the dissipation factor and frequency of various film dielectric capacitors is shown in Figure 1.26.

✨Among them, due to the insulating properties of polyester film capacitors, a considerable dielectric dissipation tanδd of the insulating component is caused. Especially in the case of low frequency, polyester film capacitors are significantly higher than the total dissipation factor of polypropylene film capacitors and polyethylene film capacitors.

☀️The above is the relationship between the dissipation factor and frequency of the film capacitor. In the next article, we will explain the relationship between the dissipation factor and temperature, humidity and voltage.

The post What is the dissipation factor of film capacitors and frequency? appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

When the current flowing through the film capacitor reaches the rated current allowed, the limitation of the heat dissipation capacity and the conductivity of the electrode, the current flowing will not be allowed to continue to increase.

🌞Is the derating of the applicable AC voltage of the film capacitor with frequency proportional to the product of the voltage amplitude and the frequency?

Since the current of the capacitor is proportional to the product of the capacitance of the capacitor and the rate of voltage rise, the rate of voltage rise is proportional to the product of the voltage amplitude and frequency. Therefore, when neglecting the influence of the dielectric loss of the capacitor, the current of the capacitor will be proportional to the product of the voltage amplitude and the frequency. However, for film capacitors, as the frequency increases, the dielectric loss cannot be ignored. Therefore, the derating of the applicable AC voltage of the film capacitor with frequency is not proportional to the product of the voltage amplitude and the frequency.

🌞The following figure shows the relationship between the AC voltage and frequency that can be applied to the film capacitor at different frequencies.👇

No alt text provided for this image
As can be seen from the figure, in the characteristic curve with a capacitance of 220nF, the allowable effective value voltage at a frequency of 10KHz is about 190Vrms, and the allowable effective value voltage at a frequency of 100KHz is 130Vrms. The product of the effective value of the voltage and the frequency of the two is greater than the former.

✊In your circuit board, have you also encountered AC voltage and frequency problems? If so, looking forward to discussing more details with you!!

Email: coco@xuanxcapacitors.com

Ph/(whatsapp): +86-18825879082

Skype: Coco.PSH

The post The relationship between the applicable AC voltage and frequency of Film capacitor？ appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

 The film is processed to allow metal atoms to attach to the film. The metal is evaporated under vacuum (1200 ° C for aluminum) to the surface of the treated film (the film is cooled to -25 ° C to -35 ° C) to form a metal layer. If the dielectric is short-circuited, the metal plating will volatilize and short-circuit. The local isolation, this phenomenon is called the self-healing effect, the self-healing effect of the metallized film is the main factor to improve the voltage gradient; for the dry technology, in the pulse application, the voltage gradient can reach 500V/μm or more, in the DC In the filtering application, the voltage gradient can reach 200V/μm. Since the capacitor is designed according to the CEI1071 standard, the capacitor can withstand several times the surge voltage of twice the rated voltage without significant life shortening. Therefore, the user only needs to consider the nominal voltage required in the application.

Electrolytic Capacitor principle

Uses the dielectric properties of alumina. Aluminum has a dielectric constant between 8 and 8.5 and an operating voltage gradient of 700 V/μm. Therefore, for 900V (DC), an alumina thickness of 1.2 um is required. However, this thickness is not possible because, in order to have a good energy density, the surface of the aluminum foil must have grooves. Obviously, there is a ratio between the foil groove and the thickness. The thickness of the aluminum reduces the capacitance factor of the aluminum foil groove. For example, the capacitance coefficient of 500V is half of that of the low voltage capacitor.

In addition, the electrolyte conductivity of the low-voltage electrolytic capacitor is 150 Ωcm, the electrolyte conductivity of the high-voltage electrolytic capacitor (500 V) is 5 kΩcm, and its RMS current is limited to about 20 mA/μF. For the above reasons, the typical nominal voltage of a typical electrolytic capacitor is 500V, so in the case of requiring a higher voltage, the user must use a plurality of capacitors in series. At the same time, because the insulation resistance of each capacitor is different, the user must connect a resistor to each capacitor to balance the voltage. In addition, if a reverse voltage exceeding 1.5 times the voltage is applied to the capacitor, it will cause a chemical reaction inside the capacitor. If the voltage continues for a long enough time, the capacitor will explode, or with the internal pressure of the capacitor. The release of electrolyte will flow out. To avoid this danger, the user must connect a diode in parallel with each capacitor.

The post The electrolytic capacitor and film capacitor principle appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

A film capacitor is a capacitor in which metal foil is used as an electrode, and plastic films such as polyethylene, polypropylene, polystyrene or polycarbonate are overlapped from both ends and then wound into a cylindrical structure. According to the type of plastic film, they are called polyethylene capacitors (also known as Mylar capacitors), polypropylene capacitors (also known as PP capacitors), polystyrene capacitors (also known as PS capacitors) and polycarbonate capacitors.

二, the working principle of the film capacitor

The working principle of the film capacitor is the same as that of the general capacitor. It stores the electric charge on the electrode and stores the electric energy. Usually, it is used together with the inductor to form the LC oscillating circuit. The working principle of the capacitor is that the electric charge will move under the electric field, when the conductor Having a medium between them hinders the movement of charge and causes the charge to accumulate on the conductor, resulting in the accumulation of charge.

三, the use of film capacitors

The function of the film capacitor is the same as that of all capacitors, which acts to accommodate the charge.

However, compared with other general capacitors, film capacitors are excellent in performance because of their excellent characteristics. Its main characteristics are as follows: no polarity, high insulation resistance, excellent frequency characteristics (wide frequency response), and low dielectric loss.

A capacitor of the type of a metallized film, which has a so-called self-recovery effect (Self Healing AcTIon), that is, an electrode metal around the short-circuited portion is caused by a small portion of the electrode due to a weak electrical boundary. The electrostatic energy or short-circuit current carried by the capacitor at that time will cause a larger area of melting and evaporation to restore the insulation, so that the capacitor restores the function of the capacitor again. In other words, it can heal itself instantly.

Film capacitors are commonly used for high frequency filtering, high frequency bypass, first or second order filtering circuits. Widely used in electronics, home appliances, telecommunications, electric power, electrified railways, hybrid vehicles, wind power, solar power and many other industries.

The post The use and working principle of film capacitor appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

Domestic capacitor companies should be more forward-looking

At present, global capacitor production capacity is mainly concentrated in Japan, Taiwan and China. Compared with the former two, domestic capacitor production capacity is large, but most of them are low-end products. Therefore, Pan Da-nan, secretary general of the China Electronic Component Industry Association Capacitor Branch, pointed out: “Domestic capacitor companies should adapt to market changes, pay close attention to forward-looking industries, and continuously introduce products that meet the requirements of different complete machines to become bigger and stronger. Current capacitor manufacturers should Focus on the development of solar photovoltaic, wind power, tidal power, energy-saving lamps, electric vehicles, hybrid vehicles, automotive electronics, subways, high-speed rail, DC power transmission, triple play, HDTV, set-top boxes, mobile TV and other industries.”

The advantages of aluminum electrolytic capacitors are still huge

Capacitors account for about 40% of the total electronic components, while aluminum electrolytic capacitors account for 34% of the total capacitor production. Aluminum electrolytic capacitors, which have a wide range of voltage and capacitance, large power storage and low price, account for 44% of consumer electronics applications, mainly used in household appliances such as computers, color TVs, air conditioners, cameras, and CNC lathes.

With the continuous advancement of aluminum electrolytic capacitor technology and the continuous product structure, in recent years it has been widely used in automotive electronics, new energy, aerospace military and other fields, mainly used in the manufacture of energy-saving lamps, inverters, inverters, uninterruptible power supplies, etc. This will increase the market share of aluminum electrolytic capacitors in the entire capacitor market. High frequency, low impedance, long life, wide temperature, ultra small size, etc. will be the development direction of aluminum electrolytic capacitors.

Film capacitors follow the trend

Compared with aluminum electrolytic capacitors, film capacitors have the advantages of good reliability, stable performance, and large capacity, and are more suitable for the harsh outdoor environment. Especially in the field of new energy vehicles, wind power, solar power, high-speed rail and light rail trains and high-voltage inverters, film capacitors have become the first choice due to their advantages in life, temperature and voltage.

It is understood that international wind power giant Vestas and other manufacturers have begun to use film capacitors, and Toyota New Energy Vehicle Prius II replaced aluminum electrolytic capacitors with film capacitors. In China, aluminum electrolytic capacitor giant Jianghai also invested 200 million yuan to build 10 high-voltage film capacitor production lines, forming an annual output of 1 million high-voltage large-capacity film capacitors, which is also preparing for future film capacitors for new energy vehicles.

As the world’s top five film capacitor manufacturers, Farah Electronics also expands the frequency conversion appliance and new energy market. The company’s AC film capacitors can be applied to many fields of new energy: hybrid vehicles, wind power, solar energy, etc. However, the shortcomings of large and high-priced film capacitors also have a great impact on market share. In order to meet the needs of new industries, high frequency, large capacity, high current, low impedance, high voltage, high dv / dt characteristics will be the development direction of film capacitors.

Film capacitor PK aluminum electrolytic capacitor, who will hold the ear in the future?

At present, the market capacity of aluminum electrolytic capacitors in the new energy market is still larger than that of film capacitors, but with excellent performance, the permeability of film capacitors is also constantly increasing. In the future, is the film capacitor who replaces the aluminum electrolytic capacitor, or does it distinguish the market according to the high pressure range? At the upcoming 78th China Electronics Show, sponsored by China Electronic Equipment Corporation and China Electronic Component Industry Association, China Electronics Business Magazine and China Electronic Component Industry Association Capacitor Branch hosted the “Capacitor Application and Selection Seminar” The application prospects and market development of these two capacitors in the green emerging industry will be discussed, and the selection and application design reference for engineers and procurement personnel will be provided to enhance the design and procurement capabilities of local engineers and procurement personnel in China.

The post A new opportunity for film capacitors to replace aluminum electrolytic capacitors appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.

CBB capacitors, polypropylene capacitors. With excellent high-frequency insulation performance, capacitance and loss are independent of frequency in a large frequency range, with small changes in temperature, and dielectric strength increases with increasing temperature, which is difficult for other dielectric materials. High temperature resistance, small absorption coefficient.

CL capacitors, polyester capacitors, also known as polyester film capacitors. The capacity can be from 100pF to several hundred uF; the working voltage is from tens of volts to tens of thousands of volts. High insulation resistance and good heat resistance. With self-healing and non-inductive properties. The disadvantages are large losses and poor stability of electrical parameters.

Difference between CBB capacitor and CL capacitor

♦   Loss: The CBB capacitor and the CL capacitor do not differ greatly in their appearance, but they differ greatly in their electrical properties. The loss of polyester capacitors is relatively large, typically around 50×10-4 at 1 kHz, which is comparable to paper-based capacitors. The loss (1 kHz) of the polypropylene capacitor is about 10×10-4, which is actually less than 5×10-4, which is about one tenth of that of the polyester capacitor.

♦   Insulation: CBB capacitors and CL capacitors have particularly good insulation properties and are superior to other capacitors. For example, a CBB22 type 100nF capacitor can have an insulation resistance of more than 50,000 megaohms.

♦   Temperature coefficient: The temperature coefficient of the CBB capacitor and the CL capacitor is generally about 300PPM/°C, but the CL type is a positive temperature coefficient and the CBB type is a negative temperature coefficient. It was previously described that the capacity of a CBB capacitor is reduced by about 1-2% when the temperature rises by 40°C. Therefore, neither capacitor can be made into a precision capacitor with an accuracy of ±5% (J).

The post The difference between CBB capacitor and CL capacitor appeared first on DongGuan Xuansn Electronic Tech Co.,LTD.