Author Topic: photoflash capacitor ESR in RLC discharge circuit  (Read 801 times)

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Offline frustratedgrape45Topic starter

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photoflash capacitor ESR in RLC discharge circuit
« on: May 12, 2020, 12:17:29 pm »
hi, my query contains a few diagrams & equations so i typed it out

also, here's the web link as outlined in the second picture: www.glancap.com/web/viewerPDF.asp?Filename=/uploadimg/PF%20Series.pdf
« Last Edit: May 12, 2020, 12:21:12 pm by frustratedgrape45 »
 

Offline gbaddeley

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Re: photoflash capacitor ESR in RLC discharge circuit
« Reply #1 on: May 13, 2020, 02:05:13 pm »
What are querying us about? There could be other parasitics in your schematic that might be considered. It depends on what you are interested in.
Glenn
 

Offline T3sl4co1l

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Re: photoflash capacitor ESR in RLC discharge circuit
« Reply #2 on: May 13, 2020, 03:46:01 pm »
Well, yes, in general ESR won't be the 120Hz value.

I suppose they might be leading you to an answer of iteratively solving for (or approximating) f_test ~= f_underdamped, or perhaps substituting them to get a closed form solution but that may be messy.

Note that a single frequency, steady state measure -- which is how we measure ESR -- isn't the most meaningful for a pulse, as the pulse contains quite a broad range of frequencies.  A more complicated equivalent circuit may be desirable.

In general, the ESL + ESR + C model can be further decomposed into many parallel and series RLC elements, modeling its real impedance more accurately over a wider range of frequencies.  This assumes one has an impedance plot for the component, of course; this is rarely given for electrolytics, unfortunately.

In practice, electrolytics' characteristics vary enough (between individuals, and over temperature and time) that such accuracy really isn't important.  The pulse might deliver 2200A one day and 1900 the next (say if the following day were cooler, or the capacitor were switched out for another).

Tim
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