Re: Diode Strings

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

Original poster: "Richard W." <potluckutk-at-comcast-dot-net> 


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, August 20, 2004 1:02 PM
Subject: Re: Diode Strings


 > Original poster: "Richard W." <potluckutk-at-comcast-dot-net>
 >
 >
 > ----- Original Message -----
 > From: Tesla list <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Friday, August 20, 2004 7:42 AM
 > Subject: RE: Diode Strings
 >
 >
 >  > Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com>
 >
 >  > The reverse voltage seen by any diode (or diode stack) in a bridge
 > rectifier
 >  > is equal to the DC output voltage, ie 1.4 times the RMS AC input
voltage.
 >  > The reason is that when one diode is conducting, the voltage across it
is
 >  > "negligible" therefore the whole DC output voltage must appear across
the
 >  > other diode on that side of the bridge. (If you draw the diagram you
can
 > see
 >  > that the two diodes are in series across the DC bus.)
 >  >
 >  > So if you're making a rectifier to have 40kV DC output, your diodes
must
 > be
 >  > rated at least 40kV PIV each. Preferably 1.5 to 2 times more for
safety.
 >  >
 >  > Steve C.
 >  >
 >  >
 >
 > OK.
 > Then to rectify 15kv or ~22Kv RMS and to have a X2 safely margin I may as
 > well put 50 diodes in each leg since I have them. I'll be ordering more
 > components from the same source and can get more diodes for just a few
 > bucks. Heck, I wouldn't be against 60 diodes per leg if that's something
 > that would help my peace of mind and it would certainly be cheap enough to
 > do IMO.
 >
 > Thanks!!
 >
 > Rick W.
 > Salt Lake City
 >
 >

I'm sitting here looking at this as per the posts and I'm like..."wait a
minute"

When the filter cap charges to 22Kvdc one leg of the bridge is tied to the
negative swinging side of the transformer. So that's 40 - 45Kv on one leg of
the bridge.

Duh!
OK, it takes a little longer for some people. :/

40 diodes is minimum. For a safety margin of 2X then I would need 80 per
leg.
I don't care about the soldering but it gets to the point that one may need
to consider "parts count" to "risk of failure".

Rick W.
Salt Lake City