DC-LINK

DC-Link capacitors are power electronics capacitors that work in direct current.

These capacitors are suitable as long as it is intended to provide a low impedance path to high frequency switching currents and to provide energy storage. The input stage can be as simple as a rectifier off of an AC line input voltage or a power factor correction (PFC) circuit that generates a constant high voltage current. The DC-Link capacitor acts as the phase output filter in the PFC stage that absorbs the switching currents and whose main objective is to minimize the ripple
current due to the alternating component existing in the direct current.

The output stage should be a switched mode converter or inverter that “cuts off” the excessive frequency current from the DC-Link capacitor. The capacitor also has to be sized to meet DC-Link ripple voltage specifications and energy storage between mains cycles or when input power is lost. Therefore, it should have a low equivalent series resistance (ESR), a minimum series inductance (Ls) and ripple current.

In general, there are three types of capacitors for these applications: aluminum electrolytic, ceramic and DC-Link film.

The selection is not easy and depends largely on the requirements of the project. However, although the electrolytic models are cheaper and more compact than the other models, their durability is much lower and finally translates into a cost similar to other solutions and greater maintenance work, with the film ones offering a better current of ripple and durability, in addition to a greater voltage range of up to several kV.

In this sense, RTR Energía has extensive experience in manufacturing and calculating metallized polypropylene film capacitors, and offers a wide variety of high-quality DC-Link capacitors thanks to the strict manufacturing conditions and the high quality of its materials, which guarantee a low inductance, low internal resistance and high reliability. The coils housed inside an aluminum cylinder are sealed with V0 self-extinguishing polyurethane resin, prepared and certified under the UL94 standard and manufactured by RTR Energía. Therefore, the advantage of using RTR Energía’s film DC-Links over other DC-Link capacitors or over electrolytic capacitors are:

• Longer useful life.
• Great reduction of failures.
• Loss reduction.
• Significant reduction in internal series resistance and inductance.
• More exact tolerances.
• Thanks to its compact design, it is very practical for electrical and mechanical use.