RE: Diode Strings

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

Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com> 

 >Yes, the PIV is 40 KV.  But it will be distributed across
 >two legs of a bridge

I have seen quite a few people mention this now so I couldn't let it pass.
it's wrong!

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.