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Re: Welders vs. Variac ballasts, was Rotaty popping, (Was Re: comm



In a message dated 4/26/00 5:40:54 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes:

> John,
>  
>  As an addition to an earlier reply of mine, I am a couple of days behind 
> here 
>  - the 5,000 watt variac that I am using as ballast for my 5kva 
transformer, 
> I 
>  believe is saturating.  It is rated for 120 volts, 5,000 watts which 
should 
>  be good for about 40 amps.  My typical primary current is around 30 amps.  
> It 
>  does groan a little however.  I really don't want to cut the core.  An 
>  interesting thing to note is that the best performance from the coil does 
> not 
>  come from a particular tight setting on the ballast variac.  I now have it 
>  set about in the center, and it really does not change the performance if 
I 
>  move it either way up to maybe 25%.

Hi Ed,

Well since you're running the variac near the center of it's range, this
may explain why you may be getting better results than I did.  I had
to run with just a few turns in use on my TC.

>  
>  Again, the reason I went to the variac instead of the welder was to 
prevent 
>  an unwanted 60 HZ resonance that was causing extremely high primary 
voltages 
> 
>  and destroying my caps.  The variac also fixed the problem of the popping 
>  sound in the rotary.  

Why should the variac stop the unwanted resonances?  Was your welder
the infinitely variable type, or the stepped adjustment type.  If you had the
stepped type, then I can understand that you may not have been able to
obtain exactly the right amount of L.  But with the infinitely variable type
you would have ..... unless .... maybe the welder did not have enough of
a range of inductance ??   Maybe you would have needed to use 2
welders in series?   Or maybe the L of the welder did not go low enough?
Many questions.

>  My original configuration with the welder and using 
>  about 1.5 ohms of series resistance also seemed to run better at lower 
> welder 
>  settings, which would be with higher inductance.  I haven't measured the 
>  inductance of the variac, but I would guess from looking at it that it 
would 
> 
>  be considerably less than the welder.

I think that variacs have a surprising amount of inductance, more than
one would think by looking at it.  Another question....  Does the TC still
draw the same total current now compared with the original set up using
the welder... for the same spark lengths?

Cheers,
John Freau
>  
>  Ed Sonderman