Temperature Estimation of Aluminum Electrolytic Capacitor under Actual Circuit Operation

To increase the power density and lifetime of power converters, the loss evaluation of passive components is crucial. The lifetime and reliability of electrolytic capacitors are strongly influenced by temperature. To calculate power loss and temperature rise, an accurate loss calculation method is proposed herein. First, a novel measuring method of the equivalent series resistance (ESR) of a capacitor by utilizing a B-H analyzer is introduced. The measured results show that the ESR of the electrolytic capacitor has strong dependency on the temperature, current frequency, etc. By considering the characteristics of the ESR and the thermal resistances in several portions of the capacitor, the power loss of the electrolytic capacitor in a practical operating condition, for instance in a non-sinusoidal current waveform and high temperature, is calculated. The experimental results agree with the calculated ones.