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Electrolytic capacitors with ~50ns pulse of ~30% over rated voltage
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Psi:
Does anyone know how electrolytic capacitors behave with a very short pulse of overvoltage.
(I'm thinking ~50ns duration ~30% overvoltage)

I'm sure it's not 'good' for them, but is this something that definitely leads to premature failure or something that is very frowned upon but probably not going to do much etc..

I noticed this on a prototype circuit and have already addressed it with higher voltage caps but it got me wondering.
PartialDischarge:
Badly. It depends on how often that pulse takes place, but that will prematurely kill the cap. You are entering into partial discharges area, high frequency currents that affect the isolation. If that kind of pulse takes place often I'd say at least a 100% excess rated voltage needs to be used
Kleinstein:
It takes a lot of current to charge the cap from 100% to 130% within 50 ns.  Chances are the ESR / ESL would prevent this from really reaching the capacitor part. If seen on the scope, the question is if this is real, of more like the lead inductance.
Psi:
interesting.

Thanks.
timenutgoblin:

--- Quote from: Psi on September 29, 2021, 08:33:06 am ---Does anyone know how electrolytic capacitors behave with a very short pulse of overvoltage.
(I'm thinking ~50ns duration ~30% overvoltage)

I'm sure it's not 'good' for them, but is this something that definitely leads to premature failure or something that is very frowned upon but probably not going to do much etc..

I noticed this on a prototype circuit and have already addressed it with higher voltage caps but it got me wondering.

--- End quote ---

I realize that your question has already been answered...


I don't have any experience with this type of testing nor am I confident of my calculations.

One thing that you didn't specify is whether the capacitor is precharged at 100% of it's rated voltage before before pulsing with +30% overvoltage or whether you're pulsing the capacitor with 130% of it's rated voltage from a discharged state.

If I = C dV / dt then dt = 25ns since the pulse is symmetrical (25ns charge followed by 25ns discharge) and dV depends on the initial charge state of the capacitor.

If E = ½CV² and you further-energize the capacitor for 50ns then the dissipated power (power is Joules per second) then that is a lot of power.

I suppose the capacitor's ESR would be vaporized doing this (P = I²R). Also, I think the ESR would limit the effects.

Are you planning to test the capacitor in a blast chamber? You will likely end up with one very angry capacitor!  :rant:
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