In the traditional inverter and converter, the bus capacitors are electrolytic capacitors, but in the new ones, the film capacitors are chosen, what are the advantages of film capacitors compared with electrolytic capacitors?

At present, more and more centralized and string inverters are choosing film capacitors for the following reasons:

(1) Film capacitors can achieve higher voltage withstand than electrolytic capacitors. The rated voltage of aluminum electrolytic capacitors is lower, up to 450 V. To obtain higher voltage withstand level, they usually need to be used in series, and the problem of voltage equalization must be considered in the process of series connection. In contrast, film capacitors can reach up to 20KV, so there is no need to consider series connection in medium and high voltage inverter applications, and of course, there is no need to consider the connection problems such as voltage equalization and the corresponding cost and manpower.

(2) Film capacitors have higher temperature resistance than electrolytic capacitors.

(3) The life time of film capacitor is longer than electrolytic capacitor. Generally, the life span of electrolytic capacitor is 2,000H, but the life span of CRE film capacitor is 100,000H.

(4) ESR is much smaller. The ESR of film capacitor is usually very low, generally below 1mΩ, and the parasitic inductance is also very low, only a few tens of nH, which is unparalleled by aluminum electrolytic capacitors. The extremely low ESR reduces the voltage stress on the switching tube, which is beneficial to the reliability and stability of the switching tube.

(5) Stronger ripple current resistance.The ripple current resistance of metalized film capacitors can be ten to several dozen times of the rated ripple current of aluminum electrolytic capacitors of the same capacity. In order to achieve higher current resistance, aluminum electrolytic capacitors usually use larger capacity to meet the requirements, while larger capacity is an unnecessary waste of cost and installation space.