Scott Townley wrote:
(snip)
> This amp runs on 13.8VDC and about 70-80A.
(snip)
> As it happens I have a 10VAC, 100A transformer (actually it's
> dual-secondary, and each secondary is marked 10V/100A) and a 1F (or
> 1,000,000uF) capacitor that the audio nuts use in their cars. So I'm
> thinking I can build it myself...capacitor input filter would be 14.1VDC
> max which is fine for the amp.
> One question is: what to use for rectifiers?
(snip)
Have you considered connecting the two 10 volt secondaries in series
and using a pair of diodes to rectify the output, returning on the
center tap? This cuts the diode heat and drop in half, but heats the
windings a bit more. A 300CNQ040 dual diode rated at 300 amps average
out and 45 PIV runs about USD35 from Digikey. The heat sink surface
is the positive output.
> Any suggestions before I press on? Is 10VAC just too close to the fuzzy
> edge for a 13.8V amplifier? 1F should be enough filter capacitance, is
> there some reason those audio stiffening caps aren't suited for filter
> service? (They don't quote any peak or surge current ratings)
I would be more worried about the RMS ripple current rating, since
that is what is going to boil the cap over. A capacitor bank really
rated for something like 100 amps of ripple current rating is going to
be spendy. Ripple current handling ability will cost you roughly USD1
per ampere.
For instance, a Panasonic ECO-S1CP683EA, 68,000 uF, 16 volt has a
ripple current rating of 9.05 A and costs USD6.73 (from Digikey) if
you but 10 of them. 10 would add up to .68F with a ripple current
rating of 90.5A if you can keep their ambient below 85C.
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