Main parameters of Capacitor

The main parameters of the capacitor are nominal capacity and allowable deviation, rated operating voltage, insulation resistance, temperature coefficient, capacitor loss and frequency characteristics.

1. Nominal capacity and allowable deviation of capacitor The capacitance of the mark on the capacitor is called nominal capacity. There is a certain deviation between the actual capacity of the capacitor and the nominal capacity, and the permissible maximum deviation range of the capacitor's nominal capacity and the actual capacity is called the permissible deviation of the capacitor. The error of capacitor's nominal capacity and actual capacity reflects the precision of capacitor.General capacitors commonly used Ⅰ, Ⅱ, Ⅲ grade, electrolytic capacitors with Ⅳ, Ⅴ, Ⅵ grade.

2. Rated operating voltage of capacitor Rated operating voltage refers to the capacitor in the specified temperature range, can be continuously reliable work of the highest point pressure, sometimes divided into rated DC operating voltage and rated AC operating voltage. The rated operating voltage is related to the dielectric and ambient temperature of the capacitor. The maximum operating voltage that the capacitor can withstand varies with the ambient temperature. When the capacitor is selected, a capacitor with a rated operating voltage greater than the actual working voltage shall be selected according to the working voltage, to ensure that the capacitor is not penetrated. The commonly used fixed capacitor working voltage has 6.3V, 10V, 16V, 25V, 50V, 63V, 100V, 400V, 500V, 630V, 1000V, 2500V.The pressure value is generally directly nominal on the capacitor, but some electrolytic capacitor pressure using the color standard method, the position near the root of the positive lead.

3. Temperature coefficient of the capacitor The change of temperature will cause a small change in capacitor capacity, which is usually expressed by the temperature coefficient. The temperature coefficient refers to the relative variation of the capacitor capacity at a certain temperature range of 1 ℃ per change in temperature.

4. Leakage Current OF capacitor Capacitor media is not absolutely insulated, there will always be some leakage, resulting in leakage current. Generally, the leakage current of electrolytic capacitors is relatively large, and the leakage current of other capacitors is very small. When the leakage current is large, the capacitor will be hot, when the heat is serious, the capacitor will be damaged by overheating.

5. Insulation resistance of capacitor The value of the insulation resistance of the capacitor is equal to the ratio of the voltage at both ends of the capacitor to the leakage current through the capacitor. The insulation resistance of the capacitor is related to the dielectric material and area of the capacitor, the material and the length of the lead, the manufacturing process, the temperature and the humidity. For capacitors of the same medium, the larger the capacitance, the smaller the insulation resistance.

Capacitor insulation resistance of the size and change will affect the performance of electronic equipment, for the general electronic equipment, the greater the choice of insulation resistance, the better.

6. Frequency characteristics of capacitors Frequency characteristic refers to the performance of a capacitor to a variety of frequencies (that is, the characteristics of electric capacitance and other electrical parameters changing as the frequency of the circuit works). Capacitors of different dielectric materials, their maximum operating frequency is also different, for example, large capacity capacitors (such as electrolytic capacitors) can only work in the Low-frequency circuit, and high-frequency circuit can only use a small high-frequency ceramic capacitor or mica capacitor.

7. Dielectric Loss of capacitor The energy consumed by the capacitor in the electric field is usually expressed by the ratio of the loss power to the capacitor, i.e. the tangent of the loss angle. The greater the loss angle, the greater the loss of the capacitor, the larger the loss of the capacitor is not suitable for the high-frequency operation.