A maximum ripple current declared, for example, at 100 kHz and at a temperature of +105 ℃ for an electrolytic capacitor, if estimated at a temperature of +85 °C, how much does it increase? What order of magnitude? Let's say we have 1000 mA at 105 °C and a 25 V / 470 μF electrolytic capacitor, what could it become at 85 °C?
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Approximately 1.7A (1A\$\cdot\sqrt{3}\$), all other things being equal, and assuming a \$\Delta{T}\$ of 5°C due to ripple current for 105°C rated capacitor with a 105°C Ta and \$\Delta{T}\$ of 15°C for the 105°C rated capacitor with an 85°C Ta. Those are just typical values, the manufacturer may be able to advise for a given capacitor model and ratings.
Keep in mind that the life span of an aluminum electrolytic capacitor at the maximum rated temperature and ripple current is usually unacceptable for real applications (like a few thousand hours only), so you typically don't want to be anywhere near those limits under normal operating conditions.
answered Dec 7, 2023 at 13:37