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Re: [TCML] The Dreadful Task of Ballasting (longish)



Hi Phil,

I'm with Jay, the cores you have are amazing! Regarding the 60V when the sec is shorted. I would not have expected your transformer to have this much leakage. This must be due to the hv coils placement on the core since you don't have shunts installed nor an air gap. You may have stumbled upon an interesting approach to self limiting. I wonder if a ballast is necessary?

BTW, nice ballast!

Take care,
Bart

Phil Tuck wrote:
Bert, Scott, Harvey, Bart  et al
The situation has taken a slight turn for the better now. I am basically
waiting on the company who sold me my DVM to get back about a replacement,
so in the meantime I wound a permanent ballast
http://homepage.ntlworld.com/follies/tesla/inductor.jpg  by the 'suck it and
see ' method. Eventually after gradually chopping bits off the winding I got
to my desired 16 amps (this gives the secondary a reasonable current). Out
of curiosity more than anything I tried it on the coil and the safety gap
firing is significantly reduced. There are a few too many safety gap firings
to be happy with, but it is on the way to success. I am now wondering that
maybe my previous temporary ballast's, that also gave 16amp, were in fact
saturating. Could this have been the culprit ?
The small MOT got hot pretty quickly and the welder is only a cheap 150 amp
which also has a rather inadequate core that got hot. Whereas the ballast I
wound only gets slightly warm to touch after 5 mins on a Jacobs ladder.
With the new ballast I am still getting around 60 volts across the tranny
when the secondary is short circuit, so the tranny is still partially
behaving like an NST

As my caps are woefully STR anyway I'm ordering some more CD 942's to take
me up to 75nF (currently I have 42nF). This increase, though still STR, will
definitely move the resonance point and is something that the coil needs
anyway. If I still get safety firings with the new cap size I know then that
my stubbiness to stick with my heavy duty single static gap is the problem
and I can then complete my RSG (I milled the motor's rotor  months ago).
When I get a DVM I will use Bart's spreadsheet and post the actual results.

Regards

Phil
www.follytowers.co.uk/tesla

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