Transient thermal modeling of aluminum electrolytic capacitors under varying mounting boundary conditions

The lifetime of aluminum electrolytic capacitors is mainly determined by their operating temperature. To simulate this temperature a finite element model of a radial type capacitor, which is mounting boundary condition (MBC) independent, is developed. Thermal parameters of the anisotropic winding are calculated by means of a lumped thermal network of the capacitor under natural convection. Finally different mounting boundary conditions are experimentally analysed and compared to simulation results where an accuracy of 10% could be achieved. Besides it is shown that this specific type of capacitor directly dissipates heat over its can to the printed circuit board. The usage of potting compound reduces the total thermal resistance of the capacitor by over 20%. Both effects are correctly predicted by the thermal model.