Re: Diode Strings

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

Original poster: "robert heidlebaugh" <rheidlebaugh-at-desertgate-dot-com> 

Richard:  Your caution is well founded. Keep in mind 15 Kv eff= 22 Kv peek
so a string of 30 is only 8 Kv higher than applied, but a bridge has 2
strings in the circuit at any given time so your design sounds well planed.
       Robert    H
-- 


 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > Date: Wed, 18 Aug 2004 07:34:01 -0600
 > To: tesla-at-pupman-dot-com
 > Subject: Diode Strings
 > Resent-From: tesla-at-pupman-dot-com
 > Resent-Date: Wed, 18 Aug 2004 07:36:51 -0600
 >
 > Original poster: "Richard W." <potluckutk-at-comcast-dot-net>
 >
 >
 > Hi all,
 >
 > I have 200 1000V 6A diodes (6A10). Recovery time is ~2.5uS
 >
 > 
<http://pdf.searchdatasheets-dot-com/pdf/266/266448.pdf>http://pdf.searchdatasheet
 > s-dot-com/pdf/266/266448.pdf
 >
 >
 > I hope to use 30 in each leg of a bridge to rectify 14.4Kv from a pig.
 >
 > 6A10s are general purpose diodes so I doubt they're manufactured with
 > comparatively tight tolerances. Seaching the mailing list I've read
 > something that the first diode to turn off can take the full applied
 > voltage and could cause failure if the diodes used aren't at least close to
 > being matched.  This seems plausible if the diode turned off at the peak of
 > the AC voltage swing but that doesn't seem likely. If the diodes begin to
 > turn off relatively close to zero crossing then I don't see that it would
 > matter so much. Say I have 30 1000PIV diodes in a string with 15Kv applied.
 > Close to zero crossing the the collective voltage drops shouldn't even be
 > close to individual diode PIV. I know there are many that have had success
 > using 1N4007s but I'm just curious and maybe a bit cautious.
 >
 > So, am I missing something or is my logic in error?
 > I've also read about pros and cons using voltage balancing resistors so
 > that's on my mind too.
 > And how does recovery time figure into a diode string operating at 60Hz or
 > is 60Hz too slow to even worry about?
 >
 > I prefer to ask first than use the "powerup/duck" method.
 >
 >
 > Thanks!
 >
 > Rick W.
 > Salt Lake City
 >
 >