What is a low voltage filter capacitor?

Filter 18.432M

Electrolytic capacitors are used as rectifying and filtering capacitors for inverters/inverters. It is generally believed that the most important parameters of electrolytic capacitors are rated voltage and capacitance. Electrolytic capacitors are usually used as rectifying and filtering capacitors. This idea is based on conventional electronic technology. The effect of the phase rectification circuit. In the three-phase rectifier circuit, there are 6 wave heads in each power cycle. If capacitor filtering is used, only 1/3 of each wave head is the rectifier conduction to the output power supply, and the remaining 2/3 time, The output power can only be supplied by the capacitor. This time is about 1/9 of the power cycle, which is 2.22mS. For inverters with an output power of 30 kW, the filter capacitors are usually two strings of 3300 μF/400 V electrolytic capacitors. The average current of the rectified output under this load condition is approximately 50A. During the period of 2.2mS when the rectifier is not working, the voltage drop of the filter capacitor due to discharge is 33~35V, which is 0.055 of the average output voltage of the 600V rectified output. Considering the equivalent series resistance of the electrolytic capacitor is about 68mΩ, 50A ripple current. The lower ESR voltage drop will reach 3.5V, and the ripple voltage amplitude will exceed 6%, which is about half of that without capacitor filtering, indicating that the rectified output filter capacitor is not actually used for filtering, but for absorption. Ripple current from the rectifier and inverter.