TexasRF@aol.com wrote:
> Steve is right on the money here.
Steve's had one too many crispy fried transformers :-) I've also been
burned (both metaphorically and literally) by attractive looking big
transformers which turn out to have been designed for use with choke
input. Hook them onto a capacitor input PSU, and you get much less power
than you were expecting, lousy regulation, and the smell of burning
insulation.
> Many capacitor filters will cause peak
> currents about 5 times average but the current only flows 1/5 of the
> cycle. Since heating is related to current squared, the total heating in
> this case would approximate 5 times 5 or 25 times dived by 5 for a total
> of 5 times as much heat compared to a resistive load.
You can sometimes take liberties if you keep the average current down
(low rf clipping), overs short, and the tx/rx ratio low.
>
> The high peak current also causes 5 times the voltage drop at the peak
> of the cycle. Since we are trying to charge the filter to the peak
> voltage this means the voltage sag is also five times more than with a
> resistive load. More copper is needed to compensate.
And the problems compound if you want to run from a generator set - most
are rated for resistive or motor loads, hit them with peak current
demands from a capacitor input PSU, and the voltage dies.
Steve
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