Aug 28, 2026Reliability Engineering
How Ripple Current and ESR Affect Capacitor Reliability
Understand how ripple current, ESR and internal heating interact to influence capacitor temperature and endurance.
Ripple current flowing through an aluminum electrolytic capacitor produces internal heat. The amount of heating depends strongly on equivalent series resistance, or ESR, at the relevant frequency.
If ripple current exceeds the capacitor's rating, or if airflow and ambient temperature are worse than expected, the core temperature can rise and accelerate electrolyte degradation. This may reduce endurance even when rated voltage and capacitance appear correct.
A sound selection compares ripple-current rating, ESR or impedance, frequency, ambient temperature, cooling conditions, case size and endurance. Designers should also account for harmonics and verify that the specified conditions match the actual application.