Selecting and Applying DC Link Bus Capacitors for Inverter Applications

DC Link Bus Capacitors for Inverter Applications

Aluminum electrolytic and DC film capacitors are widely used in all types of inverter power systems, from variable-speed drives to welders, UPS systems, and inverters for renewable energy.

This paper discusses the considerations involved in selecting the right type of bus capacitors for such power systems, mainly in terms of ripple current handling and low-impedance energy storage that maintains low ripple voltage. Examples of how to use Cornell Dubilier’s web-based impedance modeling and lifetime modeling applets, whose calculation inputs include not only ambient temperature and airflow velocities but also separate mains and switching frequency components, are covered. The information provided will help engineers to select DC link capacitors that maximize efficiency and end-product reliability.