Re: MOT Power Supply Questions

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

Original poster: "Christoph Bohr by way of Terry Fritz <teslalist-at-qwest-dot-net>" <cb-at-luebke-lands.de>

Hi!

 > 1.  I am going to use 4 identical MOTs wired in series.  Does anyone have
 > the proper hook-up diagrams for doing this "the best way."  I assume we
want
 > to wire the middle two MOTs referenced at ground and then have only one
 > transformer at either side floating at 2400VAC.  Also, I seen some
diagrams
 > where it appears they use two MOTs (opposed) to provide isolation for the
 > 120VAC input.  Any reason why they are doing this?  It doesn't appear to
be
 > implementing any type of ballasting.
 >
 > 2.  Regarding current ballasting, what is the current trend.  Do we remove
 > all shunts from the MOT or can the MOT with the shunts still installed
give
 > us the current we need. (oil submersed)  Also, anyone have luck in running
 > these things to the max (under oil) without any ballasting at all???  I
 > think someone before stated that these things will self-limit the current
at
 > a point where operation (without total destruction) is possible.


I did this some weeks ago and felt that things ran quite better than
expected.
There are several Ideas of hooking the xformers up and I decided to use the
folling one:
The two centre MOT's are connected with the cores, the HI end of the center
MOT's is connected to the cores of the outer MOT's. Against suggestions from
several coilers I did not disconnect the HV-winding of the outer MOT's from
the cores. The whole setup is submergerd under oil and I didn't experience
any problems jet.

I left the shunts in the MOT's, but for no real reason, but it doesn't seem
to be too limiting to the output current. I used this supply with primary
ballasting ( one MOT with shorted secondary ), secondary ballasting ( the
MO-caps ) and without any current limiting. The primary ballast turned out
to be very unefficient, low output voltage and the ballast got really hot.
Secondary ballasting with the caps worked fine though I mistrust if these
caps will stand the stress so I always try to stand clear ;-).
Last weekend I ran the supply without any external ballast for the first
time on am 240V / 40A service I installed for this purpose. The supply went
hot for the first time, but within reasonable limits ant the output was
astonishing an a jacobs-ladder an on my 4" coil...no pics jet....

 >
 > 3.  These MOTs will be submersed in mineral oil.  What type of enclosures
 > (readily available) have you guys had luck with?  Anything off the shelf
 > that works extremely well???

I used a Plasic-container but I wound not do this again.... These things are
cool anuless you try to lift them. The container will bend and any kind aof
seal will break. I solved this by putting a smaller box inside a bigger one.
Now Handling is easy and even if something goes wrong the oil won't spill
all around.
Next time I would rather use am betal box an use the container as center
ground....just like a very small pig.

 >
 > I'm hoping to get at least 5-6kW from this thing.  (Fingers crossed!)
 >
 >

I think you can change from hoping to expecting ;-)
These things are realy the way to go if you canÄt get hold of a PDT.
so good luck an happy coiling!


Christoph