> It's mostly a question of availability of suitable Caps. A
> well suited
> common type is 450V/220uF, you could get by with 6 in
> series, but that
> is cutting it very close, prudence would say use 8 in
> series giving a
> reasonable margin on V and some 27.5uF - that'll do at
> least up to 500mA
> and likely substantially more.
Actually the ESR of the AC source, the load resistance, and
the rectifier type determine the ripple and dynamic
regulation.
In short form:
The higher the transformer ESR (equivalent secondary
resistance), the less important capacitor size is for
anything. This is because the supply starts to act like a
R/C filter with the R distributed throughout the AC system
feeding the rectifier.
There will be a point where going beyond a certain
capacitance does nothing at all. That point is very low with
a high resistance transformer.
As the transformer and power mains get better and better, an
improvement can be had using more and more capacitance.
At 2000V and 500 mA with a transformer ESR of 200 ohms 25uF
is acceptable
At the same voltage and current with a transformer ESR of 20
ohms values up to 250uF would continue to reduce ripple.
73 Tom
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|