(16-08-2011, 11:31 AM)Yorkie Wrote: Effective Series Resistance (ESR):
This only applies to electrolytic capacitors.
I'd agree with your post - except this bit!
ESR exists and is very much alive in non-electrolytic capacitors, too. Luckily, it's usually low enough to not have to worry. But occasionally, it's sufficiently non-zero to be of concern.
I've worried about the ESR of ceramic capacitors, when used across power lines, as bypass components. Similarly with polyester types in the same situation.
The ESR of metallised polyester types can provide a guide to whether they are over-stressed in terms of ripple current. Too much current can overheat and vapourise the metallising, usually in the vicinity of the end metallising for terminal connection. In a stacked foil construction, this can progressively isolate layers, thus the capacitor loses value but maintains the same dissipation factor till near the end. In a wound film capacitor, the capacitance stays nearly constand till near the end, but ESR progressively rises as the connection between metallising and termination becomes more and more tenuous.
