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>

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>
> 
> Jim,
> 
> I am not trying to be confrontational, but I don't think your statement is 
> correct.  Maybe you can clarify what you mean, in case I misunderstood you.
> 
> The way I see it, if you draw out a full bridge, each diode in the bridge 
> being rated accordingly for 1 volt (with a small margin for error, so say 
> 1.1 volts) and create a scenario where the cap is fully charged to 1 volt, 
> and the AC signal is at a peak value (which is also +1 and -1, or vise 
> versa) each diode potentially sees +2 or -2 volts as a maximum, and 
> breakdown will occur.

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


  The only place where you are protected by 2 diodes in 
> series, is across the capacitor terminals, which also appears at the + and - 
> terminals of the bridge.  This is not where the problem occurs.  The problem 
> occurs between a polarized terminal and a non-polarized terminal of the 
> bridge.  Am I making any sense, or do I have this all wrong?
> 
> Craig
> 
> 
> 
> 
> 
> >Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
> ><jimlux-at-earthlink-dot-net>
> >
> >Think of it when the output of the transformer is opposite in polarity from
> >that on the capacitor.. 2*Vpeak..
> >
> >Bear in mind, though, that if you are using a bridge rectifier, you have
> >two diodes in series, so each diode really only needs to be rated for Vpeak
> >(plus margin!).
> 
> 
> 
>