Re: rectifier stack experts?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Craig,

On 24 Oct 2002, at 9:51, Tesla list wrote:

> Original poster: "Craig Fuller by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <cbfull-at-hotmail-dot-com>
> 
> 
> 
> 
> >Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
> ><m.j.watts-at-massey.ac.nz>
> >
> >On 22 Oct 2002, at 18:44, Tesla list wrote:
> >
> > > Original poster: "Craig Fuller by way of Terry Fritz
> ><twftesla-at-qwest-dot-net>" <cbfull-at-hotmail-dot-com>
> 
> >What do you mean by "potentially"? Consider one half cycle and
> >replace each conducting diode by a piece of wire in your diagram.
> >What you actually get is two reverse-biased diodes in parallel across
> >the transformer/capacitor which are also essentially in parallel. In
> >a f.w. bridge configuration, Vtransformer and Vcapacitor never appear
> >added in series across anything. Very different from centre-tapped
> >f.w. or voltage-doubling half wave configurations I might add.
> >
> >Regards,
> >Malcolm
> 
> I like your simplification of replacing forward biased diodes with wires.  
> It helps to see what's happening more clearly.  I probably could have found 
> a better word to use than "potentially".  The engineering book I was reading 
> did not go into much detail as to why the bridge must be rated Vpeak * 2.  I 
> assumed it was because the diodes and capacitor tend to act together in a 
> fashion similar to how a cascade multiplier works to increase voltage.  
> Another reason I didn't question it was that I once rectified the output of 
> a 15kV NST with a full bridge rated for 25kV, 1A continuous, which worked 
> fine until I added a capacitor.  After that, it lasted about two minutes.  
> Maybe I will do some more research to see if I can find something that goes 
> into more detail.  Maybe you could too and post your findings.  I think it 
> would help everyone of us tinkerers to know that we are needlessly 
> destroying our diodes when it could be avoided.

Was a load connected to the capacitor? If so, what kind of load? A 
sparking gap perhaps?

Regards,
Malcolm