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RE: [TCML] Finalising design for homebuilt transformer.

Hello Finn, Bart

Finn, I spent quiet a lot of time on your webpage before I tackled this
project! You originally inspired me actually - thanks.
Yes you are quiet right, in fact I do mention that in the (rather long)
explanation on the webpage. I was getting 1.9 to 2 volts per turn when the
secondary was in its original position (wrapped around the primary) as it
had a full 8 sq inches of core area. As it will be wound now (with 4 sq
inches of core ) a practical experiment  the other day did indeed give me 1
I initially tried for both coils on the centre leg (secondary wrapped around
the primary as normal) but there was not enough room for anything more than
the original 8K, even going down on wire size would only give me space for
10K. (And that is not allowing for voltage drop of the ballast as mentioned

 A primary with the secondary ABOVe it was not viable either - again no
room. That arrangement would have allowed some shunts to be placed between
the two windings, spanning outwards to the outer legs,

I have now added an illustration (look for Fig 2) on the page now to explain
that. http://homepage.ntlworld.com/follies/tesla/radartransformer.html  (You
may need to refresh the page if it is stored in your PC's cache)

To get the voltage output though that I wanted there was insufficient room
with the old arrangement, hence the imperfect arrangement I have adopted. I
am not after an efficient design (sorry Mr Polar Bear) only a practical one

Interestingly all the transformer formula's give a primary winding of 220
odd turns being needed for an 8 sq inch core, yet as standard I only had 130
bifilar turns on there. Bifilar turns apparently act as one conductor, so
that's not the reason. I do not know the permeability  of the core however.
This transformer was originally built for the UK Admiralty (like the UK's
Royal Navy) and like any government specifications for equipment, it was no
doubt built using good quality stuff, including the core.

******  I am presuming one secondary will need to be would clockwise, while
the other is anti-clock so as to get (for example) 7500 0 7500 ? Is that
correct ? ********

Whether or not I ground the middle connection to the core I don't know. They
will be in oil in a poly box so it will not really be an issue.




-----Original Message-----
From: bartb [mailto:bartb@xxxxxxxxxxxxxxxx] 
Sent: 17 April 2009 04:02
To: Tesla Coil Mailing List
Subject: Re: [TCML] Finalising design for homebuilt transformer.

Hi Phil,

Wow, very nice! I think you've already thought of the misc. points of 
trouble and have combated those issues with what is practical for the 
core your using. Under oil, I think your going to be ok with the design 
and I expect it's going to give you near the results your expecting. 
This must have been a great learning experience for you regarding 
transformer theory. Please let us know how it works out in practice. 
I've kept your transformer build up to date (in my head) so that I know 
where you are with the whole thing as well as the past postings on this 
transformer. This makes a Tesla coil look like a cake walk (literally). 
That's probably because I am so accustomed to TC's and less accustomed 
to high voltage/high current transformers from a build standpoint.

All my best hopes of success,

Phil Tuck wrote:
> Hello.
> I am finalising my design for my homebuilt transformer and after a lot of
> experimenting (volts per turn & current draw with different setups) I have
> decided on this
> http://homepage.ntlworld.com/follies/tesla/radartransformer.html      (It
> starts about half way down the page.)
> Just wondered if anyone can see any points that could be troublesome or
> anything that  I've not considered.
> Regards
> Phil
> www.follytowers.co.uk/tesla

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