Re: Stacking MOTs

To: tesla-at-pupman-dot-com
Subject: Re: Stacking MOTs
From: Jim Lux <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Fri, 25 Sep 1998 17:35:36 -0600
Approved: terryf-at-verinet-dot-com

Tesla List wrote:
> 
> Original Poster: "Payne, Will E" <will.e.payne-at-lmco-dot-com>
> 
> > Heres an idea for those with plenty of MOTs to play around with.
> >
> > Run a MOT into a second stage of two reversed MOTs. You can then tie the
> > second stage MOTs cores to opposite ends of the HV windings and get two
> > 120v sources at HV potential.    You can then run the standard
> > parallel/series trick twice as far.
> >
> > The whole rig will only handle the power of the first MOTs rating, but
> > this one can actually be several in parallel/parallel.  A similar
> > "transformer stacking" trick has been used in particle physics to voltages
> > far beyond the capability of a single xfmr.  Dont forget you may lose 5%
> > to 10% per stage.
> >
> > Will

Actually, almost any transformers can be used for this back to back
isolation transformer scheme. Your basic run of the mill filament
transformer will have an insulation of 1500-2000 Volts, so a pair will
get you high enough to run that second MOT.  THen, you don't have to
feed everything from the first MOT.  Just make sure the VA rating on all
those transformers is enough to handle the power (and, of course, as
Will pointed out, you'll lose 5-10% each time).

You can even get inexpensive "dry transformers" (often surplus) that
have a pair of 240 windings on one side and a pair of 120V windings on
the other. They are used in factories, and the like, to get 120 and 240
from a 480 volt bus, or 120 from a 240 bus.  You connect the windings in
series or parallel to get various voltages. As I recall, 5 kVA runs
about $100-150. (You are buying a bunch of iron, though... it will be
heavy, heavy, heavy).