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Re: rectifier stack experts?



Original poster: "Crow Leader by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla-at-lists.symmetric-dot-net>

The large rectifier stacks that International Rectifer made rated tens to
hundreds of thousands of kV at AMPERES were somehow compensated. They don't
makt that product line anymore and I cannot find data sheets for them.

I've seem many x-ray machine rectifier strings with just diodes. They all
appear to be rated under 500mA. This is not useful to me.

What do people use in large commerial radio transmitters?

KEN

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, October 19, 2002 5:13 PM
Subject: Re: rectifier stack experts?


> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>
>
>
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Saturday, October 19, 2002 11:53 AM
> Subject: Re: rectifier stack experts?
>
>
> > Original poster: "Crow Leader by way of Terry Fritz
<twftesla-at-qwest-dot-net>"
> <tesla-at-lists.symmetric-dot-net>
> >
> > I've noticed mega rectifier assemblies are compensated.
>
> Not really... High quality strings are made from matched (i.e. same mfr
lot,
> low mfr variability, too) sets of rectifiers.  The last few versions of
the
> ARRL handbook have had an explanation of why you don't want RC around each
> diode. (you can also find a similar explanation if you look through the
> archives).
>
> As another poster pointed out, fast but soft reverse recovery time, and
> consistency, are what you need.
>
> This makes sense as
> > switching transients easily diodes, and in a string, when one shorts out
> for
> > good, the stresses just go up on the rest of them. Then eventually they
> all
> > break down and get destroyed. I'm assuming the use of MOVs absorbs any
> > transients that might otherwise permanently destroy a diode.
>
> What transient might that be?? in the forward direction, the MOV won't
> breakdown (because the diode Vf is much, much lower) and in the reverse,
> I'll bet the MOV is slower than the diode avalanche (nanoseconds), and
> besides, the MOV is just a lossy clamp.  Furthermore, if your getting
> transients on every cycle, the MOV will quickly degrade....
>
>  As for how to
> > desing this properly, I have not clue at all. I was using large 1N5600
> (5kV,
> > 2A) diodes before they shorted out.
> >
>
> Rules of thumb:
>
> 1) design for 2xPIV
> 2) design for 3x current
> 3) get all diodes from same mfr lot (not just same date code!).. if you
get
> tape and reel, they're pretty much always going to be same lot
>
>
>
>
>