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Re: Transformer build up

Tesla List wrote:
> 
> Original Poster: RWB355-at-aol-dot-com
> 
> SNIP
> 
>  I've built a similar contraption using 4 of the 4500V 450mA illumination
> transformers with the 600V tertiary winding (avail from H&R and also the
> cascade, limiting the output to 8 kVA per side.
> SNIP
>  That system works great as sort of a "mondo" NST (18 kV+ at 450 mA makes
> 
> SNIP
> 
> Hi Jim, ALL
> 
>  I suppose you mean 18kv and 225mAīs not 450 mA?! You are running your
second
> (2 x) HV xformer from the first and as they are the same and the first
limits
> the total current to 450mA you would only have 225mA at 9kv (x 2 for 18kV)

Yes, that is correct.

> 
> I saw your website (downloaded it). The problem is your special
transformers.
> I canīt get them here.

I would think that something similar may be available. Check out mercury
vapor lighting ballasts for big lamps.


 Thatīs why I posted my email. I want to know if I can
> do what I planned or not with my MOT setup. Up to now I havenīt gotten a
real
> answer to my question. My problem is that MOTS (Gardner 2.3kv-at-700mA) are
> almost impossible to find. I have three and would need another three (for
13.8
> kV). These are the only units (out of ten different manufacturers all
> 2.3kV-at-700mA) that will survive on a Jaccobīs Ladder for a decient amount of
> time. If they donīt survive this thrashing I wouldnīt ever dream of using
them
> in TC service.

I have heard that submerging a MOT in oil greatly improves the life.

> 
> I am thinking of winding my own. Iīll go nuts counting all those turns
but it
> seems to be the only possibility if I canīt find a decient 10-15kV-at-400mA
power
> source. I ran up my telephone bill and I donīt think I left out a source for
> HV xformers. Nothing (here in germany) !!

Because you aren't trying to make a physically small transformer,
winding could be quite easy. Wind your secondary on a bobbin, separate
from the core. Get one of those little counters that counts revolutions
(like a bicycle odometer) and use it to count turns on a motorized
winder. Also, don't forget that you don't need ultimate precision in
terms of number of turns. If you are off by 5 or 10%, it won't make that
much difference, will it?  You might be able to do it by length or
weight without even counting turns.

Your trick will be finding a suitable source for core material. Ideally,
you want a stack of silicon-steel laminations. (High resistance, thin
sheets for minimal eddy current loss)  This you might find scrap from a
larger transformer that is dead.

Transformer manufacturing isn't all that much a black art, unless you
are trying to make them commercially, where you have to eke out every
bit of value (Simply because there are no magic tricks, everyone knows
the physics, so it comes down to optimizing your manufacturing technique
to reduce costs).
>