Re: best capacitors for high ripple and large capacitance

On Apr 10, 9:37 am, Jamie Morken <jmor...@xxxxxxx> wrote:
MooseFET wrote:
On Apr 10, 5:52 am, Jamie Morken <jmor...@xxxxxxx> wrote:
Hi,

What is the best capacitor to use for this?

63V+ rated, 1250uF min capacitance, 15Arms 200kHz ripple rating

A whole bunch of NPO ceramics in parallel is the "best" if you aren't
worried about cost or space.

15A RMS at 200KHz is quite a lot of ripple to put through a single
capacitor.

I've used CDE's 381[huh]R at about 0.5A per every 100uF with some
success. They are worth a look.

[huh] My brain froze there is a character in there

from digikey 381LX I think, wow you really drive those caps hard,

www.cde.com/catalogs/381LR.pdf

381LR221M400A012 ESR=0.271@20KHz 2.03A@20KHz

It is a different part targeted as a "ultra high ripple capacitor"

data*** specs for part#: 381LX332M063H052

3300uF, 63V, 120Hz ripple 2.5Arms, 20kHz ripple 2.9Arms,
both at 105Celcius.

Do you think that cap could be operated with 15Arms ripple
at 200kHz, with ambient temperature below 50Celcius?

No, they will heat themselves up too much. I don't like heat sinks on
capacitors.


I guess it would be better to get two smaller ones so they
have more surface area for cooling, maybe two 1800uF ones:

part#: 381LX182M063H022
1800uF, 63V, 120Hz ripple 1.7Arms, 20kHz ripple 1.96Arms,
both at 105Celcius.

cheers,
Jamie

I was looking at electrolytic's, it would take 3 of these caps to get
15Arms ripple handling:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P749...

that would be 30000uF though! :)

Also that caps 5Arms ripple rating is at 10kHz, would this rating
increase or decrease for 200kHz typically for an electrolytic?

cheers,
Jamie

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