The Main Parameters Of The Capacitor

(1) The nominal capacitance is the capacitance marked on the capacitor. But the capacitor actual capacitance is the same as The nominal capacitance is biased, and the accuracy level corresponds to the allowable error. Generally, capacitors commonly use I., II., III. grades, and electrolytic capacitors use IV., V., VI. to indicate capacity accuracy, and are selected according to their use. The capacitance of an electrolytic capacitor depends on the impedance exhibited when operating at AC voltage, and changes with operating frequency, temperature, voltage, and measurement method. The unit of capacitance is F (method).

Since a capacitor is a "container" for storing charge, there is a problem of "capacity". In order to measure the capacitor's ability to store charge, the physical quantity of capacitance is determined. The capacitor must be under the influence of an applied voltage to store charge. Different capacitors may also store different amounts of charge under voltage. Internationally, it is uniformly stipulated that when a capacitor is added with a DC voltage of 1 volt, the amount of charge it can store is the capacitance of the capacitor (that is, the amount of electricity per unit voltage), which is represented by the letter C. The basic unit of capacitance is farad (F). Under the action of 1 volt DC voltage, if the charge stored by the capacitor is 1 coulomb, the capacitance is set to 1 fara, and the farad is denoted by the symbol F, 1F = 1Q/V. In practical applications, the capacitance of capacitors is often much smaller than 1 farad, commonly used smaller units, such as millifarad (mF), microfarad (μF), nanofarad (nF), picofard (pF), etc., their relationship is: 1 microfarad is equal to one millionth farad; 1 picofarad is equal to one millionth of a microfarad, i.e.:
1 farad (F) = 1000 millifarads (mF); 1 millifarad (mF) = 1000 microfarad (μF); 1 microfarad (μF) = 1000 nanofarads (nF); 1 nanofard (nF) = 1000 picofarads (pF); That is: 1F=1000000μF; 1μF=1000000pF.

(2) The rated voltage is the highest DC voltage that can be continuously applied to the capacitor at the lowest ambient temperature and rated ambient temperature. If the operating voltage exceeds the withstand voltage of the capacitor, the capacitor will be broken down, causing damage. In practice, as the temperature increases, the withstand voltage value will become lower.

(3) Insulation resistance. DC voltage is applied to the capacitor to produce leakage current, and the ratio of the two is called insulation resistance. When the capacitance is small, its value mainly depends on the surface state of the capacitor; When the capacity is greater than 0.1 μF, its value depends mainly on the medium. In general, the greater the insulation resistance, the better.

(4) Loss. Under the action of the electric field, the energy consumed by the capacitor due to heat generation per unit time is called loss. The loss is related to the frequency range, dielectric, conductance, resistance of the metal part of the capacitor, etc.

(5) Frequency characteristics. As the frequency rises, the capacitance of general capacitors decreases. When the capacitor operates below the resonant frequency, it behaves capacitively; When its resonant frequency is exceeded, it behaves as inductive, and it is not a capacitor but an inductor. Therefore, it is important to avoid capacitors operating above the resonant frequency.