RE: 1256D Paralleling Choke

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Hello all,

I seem to remember that there was a factory balancing choke for dual 1256D's
to double the current capabilities and keep an equal current through each
variac @ 240V - 280V configuration. Anyone know how that was configured? I
also remember it was expensive. It may still be on their web site.

Jim Mora


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Thursday, June 29, 2006 6:00 PM
To: tesla@xxxxxxxxxx
Subject: Re: 1256D Paralleling Choke

Original poster: BunnyKiller <bunnikillr@xxxxxxx>

hmmm   you are right  ( not a stickler for details)  but here it
goes...  my system uses 2 @ 7.5 A variac cores stripped of the original
wire...
core size is 4" od with a 1.5" id and 4" tall  wound with # 8 THHN
solid copper 10 turns each side

but in my setup I am paralelling 2 variacs per leg of the 240VAC    (
4 variacs stacked 2 per leg therefore 2 chokes)

for a total of 280VAC at 56 or so amps    ( I have pushed it to 60
amps for several minutes with minimal warming)

in the "laser mode setup" it has run for 45 minutes pulling near 60A
at full voltage output ( usually blow the fuse on the variac after 45
minutes or things get rather toasty)   and BTW  NEVER replace a fuse
with a 3/8 bolt    it leads to a blown fuse and the other variac
taking the full 60A load along with toasted brushes....

voltage differences between variacs run approimately 2%    (about 3-4
volts tween legs)

hope this cleared things up...

Scot D





Tesla list wrote:

>Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>
>
>Hi Scot,
>
>One of the websites I originally read about this subject was yours. You
>don't give much information on the core size though.
>
>Thanks,
>Cameron
>
> > Original poster: BunnyKiller <bunnikillr@xxxxxxx>
> >
> > Hey Cameron...
> >
> > Back again     had to update my website...
> >
> > see this page for wiring and info
> >
> >
> > http://members.cox.net/bunnikillr/parallel.html
> >
> >
> > Scot D
> >
> >
> >
> > Tesla list wrote:
> >
> > >Original poster: "Cameron B. Prince" <cplists@xxxxxxxxxx>
> > >
> > >Hey guys,
> > >
> > >I've got 2 1256's I've mechanically ganged together. I now need to
build
> > a
> > >paralleling choke for them. I've read some posts and websites on how
this
> > is
> > >done, but they talk about using an old variac as the core. I have a
> > ferrite
> > >torroid that measures 2.25 inches O.D. 1.50 inches I.D. and is .75
inches
> > >wide. I believe the core is physically large enough to get 16 turns of
> > 8AWG
> > >around it, but I'm concerned if the core is magnetically large enough
or
> > >not. Any thoughts about this would be appreciated. I do have two of
these
> > >cores, so I could stack them and wind through both at once if need be.
> > >
> > >Thanks,
> > >Cameron
> > >
> > >
> >
>