Pulse power > Capacitor Banks

Failure modes of electrolytics under heavy pulse load

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A colleague is trying to replace film caps with electrolytics in a heavy pulse application (electric fence shock driver).
Does anyone know what failure modes are likely for an electrolytic driven well beyond its ripple current rating? These caps are not pulse rated AFAIK.

Pulsing is 1 to 3 pulses of ~50usec ~50A pk, from 5uF, every few minutes.  I'm concerned the very high discharge current may cause internal damage that is not immediately obvious. 

Your instinct is accurate.  Electrolyte will dry out and ESR rise.  Cap life will be brief with that degree of abuse.

A sort of similar case is the photoflash application.

Are "single use" film cameras still a thing, like for parties and receptions?
They have (or had) very low cost xenon-flashlamp circuits,
that are tested and re-used with new film, battery, etc.
Electrolytic capacitors at 300 V get discharged many dozens of times in 100 amp pulses.

There's no doubt they can work under heavy pulse loads, its just the lifetime that suffers. 
This application requires in excess of 50k pulses.  Supposedly the engineer has tested the circuit for 100k pulses with electrolytics, but I have my doubts about his assessment that it works. I don't think there's been any proper before/after comparison of the capacitor  parameters.

Photoflash capacitors are designed specifically for that use, and generally do have limited life.

Perhaps the 100k life is reasonable for a normal cap.  I reread your initial question - was mistakenly thinking pulses every few seconds, not minutes.  That will keep the average cap temperature low, so limit degradation.


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