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RE: Extended Stacking MOTs Not the way to go

Apologies to Reinhard, perhaps my diagrams were not explicit enough.

Your point (1) is well taken.  I did not mean to imply that a 2x insulation
overstress is always safe, I only say that IF IT IS, then this connection
will allow you to stack MORE MOTs with the SAME OVERSTRESS FACTOR.

Your point (2) is where we differ.  You are correct in your accounting of
the voltage rise up the stack.  However each MOT cares only about the
voltage between its primary, core, and secondary.  A MOT may be safely
operated at 1,000,000 volts as long as ALL of its parts are at the same
voltage, including the core.  I have been remiss in my diagram not to have
explicitly shown the core connections.  They could be left to float to
several kV but it would be better perhaps to fix them at a specific voltage.

Please see http://www.altair-dot-org/tesla.htm#motstack again.  I have added a
second diagram showing 4 MOTs stacked with NO overstress of the insulation.
All core connections are explicitly shown, and a total of 8 MOTs are used.
In fact, the secondary connections to the core are maintained.  IF a 2x
overstress is permitted, this could be a 16 MOT stack.  The same principle
may be applied to MOT stacks of any arbitrary number.

Your comment about the power handling problem is correct and the solution is
mentioned in the notes on both diagrams, there was just not enough room in
Win Paintbrush to show the extra MOTs.  Also, Jim Lux suggests using a high
power industrial dry transformer which could be substituted for the first
pair of MOTs.

Feel free to pick on me anytime, it keeps me honest !  Although I am the new
owner of a potential transformer, I certainly admire your MOT efforts and am
keeping a weather eye out for my own supply of MOTs to experiment with.

Will

> Original Poster: RWB355-at-aol-dot-com 
> 
>  Original Poster: "Payne, Will E" <will.e.payne-at-lmco-dot-com> 
>  
>  A pic is worth a Kword, please see
> http://www.altair-dot-org/tesla.htm#motstack
>  If you can safely stack 4 MOTs, this method will make an 8 MOT stack with
>  the same insulation safety factor, but you must use at least 12 MOTs, or
>  more depending if you want full current as well.
>  
> Hi Will,
> 
> I had a look at your website. You say no insulation is stressed more than
> 2
> times the rated voltage. Here are my comments:
> 
> 1.) Depending on the quality of the used MOTs 2x rated could be enough to
> invite problems. As my numerous tests have shown only a few MOTS will
> really
> hold up to a continues beating. My fovorite type being the Gardner
> variety.
> The stay cold after a ten minute run on a Jacobīs Ladder, while other
> types
> have started smoking after a few seconds and tend to die after a few
> minutes.
> An oil emmersion might help, tho.
> 
> 2.) Your theory that the insulation is not stressed to more than 2x Vrated
> is
> simply not true. In your setup it doesnīt make a difference (to the
> insulation
> of the "HV MOTS") if you have the two "isolation transformer MOTS"  (which
> is
> all your 2 primary MOTS connected back to back are) connected or not. Your
> isolation transformer would prevent any high voltage from wandering back
> to
> the mains, however.
> 
> Let me try to explain:
> 
> I will label your MOTS 1-4 from the bottom to the top. Each MOT has an
> output
> voltage of 2kV (example) At the bottom connection we have zero volts. At
> MOT 1
> (HV) we have 2kV. These 2kv enter MOT 2. At the top of MOT 2 we now have
> 4kv.
> This means every turn of MOT 2 has 2kv plus the TPV of MOT 2 (i.e TPV=10)
> if
> you tap winding 100 of MOT 2 you would have 1000 volts (100*10 volts) PLUS
> the
> 2kv you are pumping into the cold (zero) connection. In the example this
> would
> be 2000+1000= 3000 volts. The same continues for MOT 3 and 4. Each time
> the
> "input volatge" gets higher and higher on the "cold" leg. This is exactly
> the
> problem with seriesīing any kind of high voltage transformer.
> 
> Now, If you were to center tap (gnd) your setup at the connection MOT 2
> and 3
> the situation changes. Your theory now holds true because you have just
> divided the voltage the insulation has to hold up to in half. (being 4kv
> on
> either side of the center tap and not 8 kv from core MOT 1 to core MOT 4.
> As
> you are using an isolation xformer you can safely ct this ground and
> ct/ground
> the next identically built setup of four MOTS.
> 
> HOWEVER: !!!
> 
>  Your setup has the disadvantage of needing 6 MOTS for each HV "part
> section".
> Which means you need 12 MOTS for a 16kV setup (using 2kv/xformer). And as
> you
> are limiting the current through one set of MOTS (iso xformer) per 4 HV
> MOT
> setup, you also have to divide the current equally among the connected
> MOTS.
> Example: The two iso xformers each have a VA rating of 1600 VA (biggest I
> could find in germany). You use 4 MOTS in series/parallel. This means
> (1600VA/4) you only get 400VA of power output per MOT transformer on this
> setup.
> This would get you 8kV (or x times the 6er MOT setup voltage) at 200 mA.
> Like
> I said, I have never seen MOTS with more than 1600-1650 VA. As a matter of
> fact you will probably get a lot less than 200 mA output because I didnīt
> consider any losses (magnetic, inductive or saturation losses) This canīt
> be
> the real solution.
> 
> I have found the Gardner variety will hold up day and night if you only
> connect three in series. Firing these dry you wonīt get any arc overs or
> corona, etc (actually you can even string 4 of em in series with no
> problem.
> But I want to stay on the safe side so lets take only 3). Plus as my tests
> have proven they are very desirable because they stay COLD after long runs
> (only the power cord gets warm). If I now add three more in series and
> center
> tap/ground this setup at connection MOT 3/4 I donīt add any further strain
> on
> the insulation (as explained above). I will mount two facing each other
> and
> make three decks of two. This way I can get a small case and have enough
> insulation space in between, to prevent arcing. The whole setup is
> immeresed
> in Diala-X oil as a further saftey measure. My output would be 13.8kV
> (each
> xformer has 2.3 REAL kv, not "rated" volts, like Dave suggested a few
> mails
> ago) and 700mA total output. This is PIG POWER (9.66kVA) !!! To reduce the
> strain on my mains I could wire each set of two (primaries) in series and
> the
> three decks in parallel. I would run them across two phases (400v in
> germany).
> This way I can almost cut my input current in half. The output of the psu
> would drop to 12kv, but so what. The 1800 volts diff can be compensated
> for
> easily in a TC tank circuit.
> 
> sorry for picking on you,
> 
> Coiler greets from germany,
> Reinhard
> 
> 
>