Film capacitor for filtering and smoothing

The filter and smoothing capacitor is used to smooth the output voltage and current of the rectifier. When the voltage is lower than 450V, the aluminum electrolytic capacitor with low unit price is usually used. When the voltage is higher than 500 and lower than 700, the aluminum electrolytic capacitor can be connected in series. However, when a high reliability is required and a voltage higher than 1000 V or higher, a film capacitor is preferably used as the filter capacitor. There is nothing special about a smooth and filtered film capacitor, but the IGBT inverter is operated at a relatively high speed hard switching state due to its IGBT.

If the DC bus has a large parasitic inductance, a high induced potential will appear when the IGBT is turned off, which not only increases the turn-off loss of the IGBT, but also breaks down the IGBT when the induced potential is too high. Moreover, the filter capacitor has a large ESR, and the switching ripple current generated by the IGBT inverter inverter generates heat at the ESR of the filter capacitor to generate heat, shortening the life of the filter capacitor. The use of film capacitors as filter capacitors for inverters will periodically replace aluminum electrolytic capacitors.

The use of a film capacitor as a rectifying filter capacitor for a frequency converter can not only greatly improve the application life of the inverter inverter, but also avoid the cost and cost of replacing the filter capacitor. At the same time, due to the low ESR of the film capacitor, the switching tube in the circuit The voltage stress on the switch is greatly reduced, which is beneficial to the working state and reliability of the switch tube.