RE: Three phase rectifiers

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

Original poster: "Basura, Brian by way of Terry Fritz <twftesla-at-uswest-dot-net>" <brian.basura-at-unistudios-dot-com>

Bob/Mike,

I used a four strings of twenty 5408's for a HV bridge. They ran great up
to 70% setting on my Variac then blew. This appears to be caused by my over
zealous attempts to lower the limiting resistor value. The next iteration
(hopefully in the Spring) will use 30 or 40 5408's per string and I'll
start with a much higher resistance working down in controlled steps.

The following URL details my DC adventure to date:
http://fp2.hughes-dot-net/brianb/dc.htm

Regards,
Brian B. 

 -----Original Message-----
From: 	Tesla list [mailto:tesla-at-pupman-dot-com] 
Sent:	Wednesday, January 24, 2001 10:45 AM
To:	tesla-at-pupman-dot-com
Subject:	Re: Three phase rectifiers

Original poster: "Mike Harrison by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <mike-at-whitewing.co.uk>

On Wed, 24 Jan 2001 07:50:09 -0700, you wrote:

>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.

I would be inclined to use 1N5408's - 1KV at 3 amps, only 5p each at
100x from Rapid Elec. and rated at 3 amps - gives you a better 'smoke
margin'