Re: rectifier stack experts?

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

Original poster: "D.C. Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>


Fuji diodes have replaced the older IR units.  Also Quality Semi-Micro which
used to be Varo in Garland, TX, makes a good line of HV diodes and x-ray
diodes.

Dr. Resonance




----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, October 19, 2002 3:51 PM
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>
>
> 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
> >
> >
> >
> >
> >
>
>
>