Modeling and improving heat dissipation from large aluminum electrolytic capacitors

Thermal models for large can aluminum electrolytic capacitors have existed for a number of years for screw terminal products. These models have various shortcomings in their ability to handle the effects of package size, roll diameter and the mechanical details of assembly. An improved model was introduced recently which more accurately accounts for these internal parameters. This paper extends the use of that model to improved constructions which allow much more ripple current with no more internal heating than standard capacitors. An approximate empirical relationship has been developed to estimate conduction of heat from the roll to the terminals. In addition, the external environment of the capacitor has been considered since dissipation of heat necessarily involves transfer of the energy away from the capacitor. Studies have been conducted on the effect of air flow on the package-to-ambient thermal resistance. The use of external heat sinking is shown to be effective, especially when air flow is available and the heat sinks are integrated with the capacitor package to minimize the thermal resistances in the heat flow path. In these cases, the external thermal resistances can be reduced by more than 50%.