What Is a Filter Capacitor?

Filter capacitor is an energy storage device, which is often installed at both ends of the rectifier circuit to reduce the AC ripple ripple coefficient to improve the efficient and smooth DC output.

The calculation formula is: X (c) = 1 / W _c = 1 / (2f _c );

In theory, the higher the frequency, the smaller the capacitive reactance, the easier it is to pass high-frequency signals. In fact, due to many problems such as process, its parasitic inductance must be considered. Often parasitic inductance exceeds its own capacitive reactance and will appear inductive. ^[1]

Implementation standards:

Self-healing low-voltage ASMJ filter capacitor: IEC 60831-1 (GB / T 12747);

Self-healing high-voltage ASMJ filter capacitor: IEC 60871-1: 2005 (GB / T 11024-2010);

Rated voltage: 220v ~ 12kv;

Rated frequency: 50hz;

Rated capacity: 30 ~ 200kvar;

Capacitance deviation: -5% ~ + 10%;

Dielectric loss angle tangent (tg): 0.0003;

Maximum allowable overvoltage: 1.1un;

Maximum allowable overcurrent: 1.3 in;

Ambient air temperature: -40 ~ + 45 ;

Altitude: 1000m;

Environmental conditions: no harmful gases and vapors, no conductivity and explosive dust. ^[1]

The role of electrolytic capacitors ^[1] is to filter out the low-frequency signals in the current, but even the low-frequency signals are divided into several orders of magnitude. Therefore, in order to be suitable for use at different frequencies, electrolytic capacitors are also divided into high-frequency capacitors and low-frequency capacitors (here the high-frequency is relatively speaking).

Low-frequency filter capacitors are mainly used for electric filtering or filtering after transformer rectification, and their working frequency is 50Hz consistent with the mains; while high-frequency filter capacitors are mainly used for filtering after switching power supply rectification, and their operating frequency is several thousand Hz to tens of thousands. Hz. When we use low-frequency filter capacitors for high-frequency circuits, the low-frequency filter capacitors have high internal resistance and high equivalent inductance during high-frequency charge and discharge due to their poor high-frequency characteristics. Therefore, in use, a large amount of heat is generated due to the frequent polarization of the electrolyte. The higher temperature will vaporize the electrolyte inside the capacitor and increase the pressure inside the capacitor, eventually leading to bulging and bursting of the capacitor ^[1] .