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Old 10-06-2011, 06:22 AM   #5121 (permalink)
isaac_alaska
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thanks paul! i learn just a little bit more every day

back to the capacitor topic, i was thinking about it again, and the rms current rating on the capacitor is just the ripple current. and i haven't actually tested this on something this big yet, but it seems that the capacitor just kind of has to fill in the corners of the pulse, to make it a nice square pulse, and the batteries are still doing most of the actual current. i'm not sure how it relates in terms of percentages, but i would bet that the ripple current on the capacitor is probably less than 20% or so of motor current. just how i'm picturing it in my head...

*EDIT*
to put this capacitor in perspective, we can compare it with the existing capacitor bank in the cougar 1k. 22 electrolytics in parallel:
2.84 amps ripple current each
149 mOhm ESR each
in parallel with ten poly caps,
7.5 mOhm ESR each=.75 mOhm total
this gives
62.48 amps ripple for the whole stack
~.74 mOhm total ESR

compare this with the ring cap:
500 amps ripple
.125 mOhm ESR

new capacitor should be more than up to the job


Last edited by isaac_alaska; 10-06-2011 at 06:44 AM..
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