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Old 10-06-2011, 06:22 AM   #5121 (permalink)
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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...

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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