RE: MOT info

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Carl Litton" <Carl_Litton@xxxxxxxxxx>

Hi Rich,

The advice above your question is quite sound.  Inductive ballast on the
input line is the simplest and easiest way to control current at the
output.  If you have an assortment of transformers lying around as most
of us do, there is more than likely one that will work.

The primary is put in series with the input line and the secondary is
either left open (high inductance) or shorted (low inductance).  There
are many variables and a good LC meter is certainly helpful to measure
the inductance of the primary.  The inductive reactance can then be
calculated and the result in Ohms plugged into Ohm's Law to tell you
what the output current limit will be.  A more detailed explanation
appears on our site:

http://dawntreader.net/hvgroup/ballast.html

MOTs by the way are often a good choice in the 0-30 Amp range.  Based on
our field tests of 25 MOTs, a good rule of thumb is that the open
secondary reactance averages around 12-25 Ohms and the shorted secondary
reactance averages 1-5 Ohms at 60 Hz, giving current control
capabilities down to around 10 Amps in some cases.  Others on this list
may wish to comment or offer differing results but this is our
experience.

Good luck!


Carl Litton, Director
Raleigh-Bartlett Science Club



-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Tuesday, December 28, 2004 12:49 PM
To: tesla@xxxxxxxxxx
Subject: Re: MOT info

Original poster: Rich Simpson <richcreations@xxxxxxxxx>


>I wouldn't worry about the difference cost wise between 30A and 60A
draw.
>Assuming you run it for an hour a day at ~14 kW (plenty enough to
>annoy/scare the neighbors/police/swat team) over a month that's $84 vs.

>$42 for ~7kW. I seriously doubt you'll actually run it that much before

>spark gaps need replaced, ears need a rest, etc. I think it's always
>easier to use inductive ballasting and cheaper. With caps you'd need
lots
>of them in parallel to handle the 30-60A and you'd need lots of uF
(about
>100uF for around 25A limiting off the top of my head). I haven't
actually
>tried this myself, but seems like the caps would heat up like resistive

>ballasting. I personnly would just use the hardware store ballast, (2)
>500' rolls of 10-12 awg for 26A limiting.
I just got my new bigger variac, it is a new dual 120V/22A (motorized)
unit
that I paid dearly for, and I really do not want to burn it out, what
should I do to get the current down to 22A@240v? Again this was for a 6
or
8 mot stack (which is just until I can save up for a pig or more neons
as
all I have is a 6kv/30ma neon (and that is just not enough for my 4 inch

coil ;-)

Thanks Again
-Rich