Bridge voltage rating: Re: Power supply for Servos - bridge and caps

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "sciciora" <sciciora@A...>
> wrote:
> >
> > A small bit of trivia: in general, the higher the voltage rating
> of a
> > diode, the higher it's voltage drop. So for high current
> > applications, you don't want to get too carried away with voltage
> > rating, because the higher voltage bridge will get hotter than the
> > lower voltage one. I'm no expert, but for me, I think I'd pick

> > 200V one, depending on how well it was going to be heat sunk.
> >
> > Steven Ciciora
>
>
> Interesting.
>
> So, if one transformer is 55volt, 800 VA, AND that can handle 3 of
> these motors, then the max current will be around 10 amps.
>
> Therfore the selection of bridge would only need to be, say, 15

> and as you mentioned, 200volt.
>
> If there is any motor speed problems caused by pulling too much

> the circuit, a second transformer could be added easiy to make the
> power supply 20 amps.
>
> That then makes a 25 amp bridge a nice fit.
>
> Would a 25 amp, 200 volt bridge be a good candidate for a 20 amps,

> volt power supply ?
>
> That then also begs the question of caps.
>
> if the 800 watts discussed is fine, then 800 watts at 78 volts is
> only the 10 amps.
>
> using the 1k uF it would indicate only one 10k uF cap would be

>
> using Mariss's formula, then (80,000 x 10 ) / 78 = 10,258 uF, so a
> 10k uF cap is selected for that.
>
> This would mean a second transformer would need a second cap, kinda
> like adding systems.
>
> It seems that my plasma and Brady's mill will put these to two
> different tests.
>
> I'll post the results and layout and pictures when we get one of
> these running.
>
> Dave