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Electrolytic capacitors with ~50ns pulse of ~30% over rated voltage
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Kleinstein:
A diode would not help, as the voltage never does negative.
What would help, could be a 2nd parallel capacitor, even if smaller (like 100 nF).

With only 1 µF a the rise from, 14 V to 22 V are still 8 µC and for a pulse lenght of 50 ns this would be 160 A on average ! The the ESL must be small, more like only a few nH and this could still explain the observed spike. This must be a hell lot of a machine to cause such spikes.
Psi:

--- Quote from: Kleinstein on October 02, 2021, 03:26:12 pm ---This must be a hell lot of a machine to cause such spikes.

--- End quote ---

yeah, it's 100-200A DC winch controller.

(I did find the max voltage spike was less than stated above when probed with the scope ground spring right on the cap as closes as physically possible. But the issue has been solved by using 50V ceramic caps)
T3sl4co1l:
What value?

Again, inductance is significant, so it might not appear at the capacitor at all (say, if you could sneak an ideal diff probe down into the capacitor's rollup), or at worst, across just the ESR.

And since your duty cycle is low, it's not going to overheat or whatever.

Tim
PartialDischarge:

--- Quote from: Psi on October 03, 2021, 02:50:54 am ---
--- Quote from: Kleinstein on October 02, 2021, 03:26:12 pm ---This must be a hell lot of a machine to cause such spikes.

--- End quote ---

yeah, it's 100-200A DC winch controller.

(I did find the max voltage spike was less than stated above when probed with the scope ground spring right on the cap as closes as physically possible. But the issue has been solved by using 50V ceramic caps)

--- End quote ---

That means most of the measured spike is the result of magnetic flux from nearby switching currents. Anyway depending on what this capacitor is doing I'd even use a PP cap or ceramic with 100V
Psi:
The cap where i saw the original pulse was 1000uF 25V.

I'm now using around 120uF of 50V ceramic caps.

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