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Re: MOTs...exploring the low end of TC voltage

Hi Mike,

> Original Poster: "Mike Nolley" <mnolley-at-mail.slc.edu> 
> 
> > No, No, please! keep it on the list, we cannot have enough info
> > on low-cost transformer solutions.
> >
> > What I wonder is: Why would the outher transformers tend to saturate
> > more than the 2 inner transformers.
> >
> > I basically think we have an insulation problem, or perhaps just an
> > insulation challenge.
> 
>     Actually, the saturation problem is real, according to a post
> I read earlier--since 2000 volts is being fed into the bottom of
> the second stage secondary, the coil is actually seeing 2X voltage.
>  The core will tend to saturate very easily because even though the
> voltage differential between turns is the same as a first stage Mot,
> (i.e. the gradations between 2kv and 4kv are the same as those
> between 0 and 2kv), the level of power being handled is higher. 

Is the voltage across the winding the same though?  Is the current 
through the winding the same as the first stage transformer?

> The MOT secondary is having to deal with its own output, and that
> of the one previous to it.  I must admit I don't know the physics of
> it, but the fact of saturation is borne out by my tests on
> multi-stage MOT arrays.  In simple 1-1 arrays, the second stage
> would get warm, and the third stage, if there was one, would fail
> within 1-2 minutes.  So it is not simply a matter of core-coil
> breakdown.  With the solution I have now, the second 2 Mot stage is
> ice cold, and it is the first stage which gets warm.  I have chosen
> the highest current Mots for the first stage for this very
> purpose--and the second stages, since they tend to be handling
> much less current, I am less picky about. 

Interesting results. If the secondary windings are connected in 
series then the currents through them must be identical and if the 
windings have the same number of turns and the cores are identical 
then identical Ampere-turns must be applied and those windings at 
least must be generating the same flux density in each core. What 
appears to be getting hottest - the secondary winding/s, primary or 
core?

Regards,
Malcolm