Wednesday, December 29, 2010

【 Weak current College 】 capacitor main parameters 】

Nominal capacitance is a flag in the capacitance of the capacitor
1. actual capacitance capacitors and nominal capacitance of deviation that error, in the range of allowed deviations stated accuracy.
Precision grade and permissible error corresponding relationships: 00 (01)-± 1%, 0, (02)-± 2%, Ⅰ-± 5%, Ⅱ-± 10%, 20% Ⅲ-±, Ⅳ-(+ 20%-10%), Ⅴ-(+ 50%-20%), Ⅵ-(+ 50%-30%)
General capacitor used Ⅰ, Ⅱ and ⅲ, electrolytic capacitors Ⅳ, Ⅴ, Ⅵ-level select, according to use.
2. rated voltage
At the minimum temperature and the rated ambient temperature under the continuous increase in the maximum DC capacitor voltage RMS, General direct marking on the capacitor shell, if the working voltage exceeding the voltage capacitors, capacitor breakdown, causing permanent damage to be repaired.
3. insulation resistance
DC voltage in the capacitor, and leakage current, the ratio of the two is called the insulation resistance.
When the capacitor less hours, depending on the surface, the capacitor capacity > 0.1uf, mainly depends on the media's performance, insulation resistance as small as possible.
Capacitor time constant: for proper evaluation of bulk capacitance of the insulation and introduces a time constant, he is the capacitance of the insulation resistance and capacity of the product.
4. loss
Capacitor in the electric field, in unit time internal heating consumes energy called the loss. Various types of capacitors provide it in a frequency range of allowed values, capacitance loss mainly by dielectric loss, conductivity losses and capacitor resistance of all metal parts.
In the role of DC electric field, the capacitor's loss to leakage in the form of import loss, usually smaller, in alternating electric field, the capacitance of the loss not only import with leakage, but also to the periodicity of polarization establishment process.
5. frequency characteristics
As the frequency increases, the capacitor capacitance downward.

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