Seek capacitance knowledge, capacitance and capacitor knowledge points

1. Capacitors:

1. Function: Capacitor is an important component commonly used in electrical equipment, which can be used to accommodate electric charge.

3. Charging and discharging: making the capacitor live is called charging; Causing the charged capacitor to lose its charge is called discharge.

4. The amount of electricity carried by the capacitor: the absolute value of the amount of electricity carried on one plate of the capacitor.

5. Breakdown voltage and rated voltage: If the voltage applied to the two poles of the capacitor exceeds a certain limit, the dielectric will be broken down and damage the capacitor, and this limit voltage is called breakdown voltage; The voltage that a capacitor can withstand for a long time is called the rated voltage, which is lower than the breakdown voltage.

2. Capacitance: 1. Unit: In the International System of Units, the unit of capacitance is the method (f).

2. Commonly used units are: micromethod (F) and skin method (PF).

3. Their conversion relationship is 1f=106UF=1012pf.

4. Physical significance: It represents the physical quantity of the capacitor to accommodate the electric charge.

5. The determining factor of the capacitance of the parallel plate capacitor: the capacitance of the parallel plate capacitor is proportional to the dielectric constant, proportional to the opposite area s, and inversely proportional to the distance d between the plates.

One minute to take you to understand the difference between electrolytic capacitors and supercapacitors.

The general formula for capacitance: c=q u. For a capacitor, if the potential difference between the two stages is 1 volt when there is a charge of 1 bank, the capacitance of this capacitor is 1 method, that is: c=q u.

The special formula for parallel plate capacitors: the electric field strength between the plates e=u d.

Capacitor capacitance deterministic disassembly c= s 4 kd.

But the size of the capacitance is not determined by q (charged) or u (voltage), i.e.: c = s 4 kd. where is a constant, s is the area facing the capacitive plate, d is the distance of the capacitor plate, and k is the electrostatic force constant.

For common parallel plate capacitors, the capacitance is c= s d( is the dielectric constant of the middle beam between the plates, s is the area of the plates, d is the distance between the plates).

In the International System of Units, the unit of capacitance is farad, referred to as method, and the symbol is f, because the unit of farad is too large, so the commonly used capacitance units are millimethod (mf), micromethod (f), nanomethod (nf) and picomethod (pf), etc., and the conversion relationship is:

1 farad (f) = 10 3 millifartha (mf) = 10 6 microfarf (f) = 10 9 nanofarth (nf) = 10 12 picofara (pf) = 10 15ff.

The relationship between capacitance and battery capacity: 1 volt-ampere-hour = 1 watt-hour = 3600 joules, w =.

1) According to c = q u, the amount of charge of a plate q = 120 * 3 * 10-12) = * 10-10c (2) according to u = ed, e = u d = 120 (4 * 10-3) = 3 * 10 * 90 = * 10-17c (3) For electron pairs, from b to a, according to the kinetic energy theorem: wf electric = ek2-0, according to the functional relationship wf electric = -δep and δ ep = epa-0 = epa = ae, ek2 = * 10-17j is obtained according to the above three male brothers.

1. Test the quality of the capacitance, if there is a capacitance meter, you can use the meter to measure the capacity of the capacitor. If there is no capacitance meter, use a multimeter (preferably pointer), hit the multimeter to x100 gear, and judge the leakage and capacity of the capacitor according to the degree of deflection of the pointer. If the hermaphroditic capacitance is being measured, the pointer should go back to infinity.

If the electrolytic capacitor is electrolytic, there will be a certain leakage current, and the pointer cannot completely return to infinity, which is normal.

2. The number above the capacitor represents the capacity and withstand voltage. For example, 680 is 68pf.

3. If you can't see the logo, you can make an approximate estimate based on the opening and volume. Some can be used in decoupling circuits.

4. In general, in the filter circuit, you can see the electrolytic capacitors with large capacities such as 100uf and 1000uf. The size of the filter capacitor is selected according to the load current and ripple requirements. Multiple capacitors in parallel are better filtered than one capacitor with a large capacitance.

According to my experience, if the load current is 1A, the capacitance of the filter capacitor is 1000UF.

Hope mine is helpful to you.

Replacing the capacitance of 200V220 F with the series or parallel method can be done in the following ways:

1. If there are capacitors of 200V or 250V and above, they can be used in parallel: two at 100 F or five at 47 F, ten at 22 F; The withstand voltage of the capacitor in parallel can be different, but it cannot be lower than the original 200V; The capacities can be different, and the addition is close to or greater than 220 F.

2. There is no 200V withstand voltage capacitor, multiple capacitors can be connected in series: 100V470 F two or 63V680 F three, each capacitor in series is required to be completely equal in value, and each capacitor also needs to be connected in parallel with a 100K 1W resistor.

3. Hybrid method, capacitors are connected in parallel and then connected in series, the method is more complex and difficult to master.

Due to the relatively high working voltage, the capacitor must be insulated to prevent short circuit between capacitors and short circuit between capacitor groups and other components or lines.

To put it simply, the capacity of a shunt capacitor is the sum of the capacitance of each capacitor, and all capacitors are subjected to the same voltage (the original voltage); The total capacitance of the series capacitors is equal to the capacity of the capacitor with the smallest capacitance, and the voltage borne by each capacitor is inversely proportional to its capacity (if n capacitors of the same capacity are connected in series, the voltage borne by each capacitor is also exactly equal, which is 1 n of the total voltage), and the sum of the voltages received by all capacitors is equal to the total voltage.

You can use two that add up to 220uf and are similar.

It's better to go and buy one so troublesomely.