RE: MOT Mods

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

Original poster: "Loudner, Godfrey by way of Terry Fritz <twftesla-at-uswest-dot-net>" <gloudner-at-SINTE.EDU>

Hi Ted

I took a look at some of my 41 MOTs, and I found the type you want to
modify. After you remove the filament winding, there is a little bit of
space to fill with extra shunting plates. Filling the extra space with
shunting plates will not contribute much to the ability of the MOT to limit
current. Notice the tight combination of core and windings. This means that
the coupling coefficient of a MOT without shunts is close to 1. Adding a
full deck of shunts across the core between the primary and secondary will
reduce the coupling coefficient, but not enough to make the MOT run cool for
an extended period of time. Notice that the core of a NST is long. This
means that the coupling coefficient of a NST without shunts is much less
than 1. After Shunts are added, the coupling coefficient is reduced to a
level where the NST can run cool for an extended period of time. I have
knocked the shunts out of some MOTs, and noticed only a slight increase in
current output. In fact most of the current limiting in a microwave oven is
performed by the capacitor that is connected in series with one of the high
voltage leads. You should continue using a ballast. I am assuming that you
want to use a static spark gap in your tank circuit, and that you are not
using a rectification bridge. Otherwise the capacitors in a bridge will
contribute to current limiting, and playing at a rotary spark gap can play a
significant role in current limiting. Even if you are successful in making a
very current limited MOT, events can happen in a tank circuit that can
overcome your current limiting efforts. Don't waste your time doing such
surgery on your MOTs. My suggestion is to put two MOTs in series for voltage
increase, and then ballast with another MOT. Ballast using a MOT that
GREATLY reduces current output. Call this combination of three MOTs a unit.
Then build more units and gang them together in parallel for increased
current output. Then each unit will run cool, but the ganged units will put
out significant current. I think that MOT powered Tesla coils are
interesting because of the totally wild nature of the discharge---it has a
weird look that I like.

Godfrey Loudner







> -----Original Message-----
> From:	Tesla list [SMTP:tesla-at-pupman-dot-com]
> Sent:	Tuesday, May 08, 2001 7:38 PM
> To:	tesla-at-pupman-dot-com
> Subject:	MOT Mods
> 
> Original poster: "tesla by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <tesla-at-paradise-dot-net.nz>
> 
> Team
> Contemplating adding more MOT shunts using the space released by the
> removed
> Magnetron Heater winding.
> 
> Anybody tried this ?? and found it an effective way of avoiding external
> ballasting
> Best
> Ted L in NZ
> 
>