Three phase rectifiers

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Original poster: "bob golding by way of Terry Fritz <twftesla-at-uswest-dot-net>" <yubba-at-clara-dot-net>

Hi all,
    I have worked out the wiring for my 3 phase rectifier design. I am
going for a design voltage of 12kv at 1 amp. I would like some feedback
on the best way to go about choosing the diodes. I am going for the 12
pulse recifier design shown here (scroll down the page)
http://ham.te.hik.se/homepage/sm5bsz/supply.htm

This should keep the ripple low enough to not need any filter caps. This
will be safer and cheaper. I like safe and cheap in the same sentence.
What voltage should I aim for for the piv on the diodes? peak voltage
will be 16968V. If I go for the old rule for caps of 2.5 peak this works
out at 42420V. I am planning to use IN4007's this works out at 42 diodes
per leg x 12= 504. As they are only 8 pence each this is not a great
expense. Less than £50.00. Is there a problem with long strings of
diodes. If I get them all at the same time there is a good chance they
will be from the same batch. Should I go for 3 amp ones instead? I know
it is a lot of soldering. If it works I can fully exploit my variable
speed async gap.
cheers
bob golding