What does "rated current" refers to in the capacitor data sheet? Is the current that the capacitor can supply?

I always assumed that it is the current that the capacitor can source. Is that correct? Also why the rated current is always specified at 125°C? How to calculate the rated current at different temperatures?

  • \$\begingroup\$ Link the datasheet \$\endgroup\$ – Funkyguy Jul 23 '14 at 15:05
  • \$\begingroup\$ You can consider the rated ripple current in the datasheet link below:datasheet.octopart.com/… \$\endgroup\$ – Durgaprasad Jul 23 '14 at 15:16

It's usually the ripple current, which is the RMS value of current the capacitor sees.

On a switchmode regulator it should never be higher than half the output current. If there is a parallel ceramic capacitor that can reduce the ripple current in the electrolytic.

The ripple current causes heating in the capacitor (since the capacitor is not perfect), with power loss related to the square of the ripple current. It's reasonable to rate it at a realistic operating temperature and at a realistic frequency. Often (not always) that's at the maximum temperature rating of the capacitor and a plausible SMPS frequency such as 100kHz.

  • \$\begingroup\$ Thanks Spehro. Just a small question. Here you meant to say that the rated ripple current should be more than half of the output current? Correct me if i am wrong.. thanks. \$\endgroup\$ – Durgaprasad Jul 23 '14 at 15:25
  • \$\begingroup\$ It should not exceed half the output current. eetimes.com/document.asp?doc_id=1273335 \$\endgroup\$ – Spehro Pefhany Jul 23 '14 at 15:33
  • \$\begingroup\$ It is very clear to me now. On the same lines could you explain me how we can get this current for different temperatures. \$\endgroup\$ – Durgaprasad Jul 23 '14 at 15:38
  • \$\begingroup\$ @Durgaprasad Check the manuals from the manufacturer and see their recommendations. They may or may not allow higher ripple current at lower temperatures. You should also use the correct max ripple current for the frequency (lower frequencies have a lower maximum ripple current). \$\endgroup\$ – Spehro Pefhany Jul 23 '14 at 17:27

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