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Re: new power transformer (variac as ballast)



to: John

A complete slot with 0.120 of Nomex or other suitable insulation is epoxied
in the gap works fine.  The 0.120 spacing prevents saturation as you
suspected.  Also run a suitable 0.5 to 0.8 Ohm (5 kw) resistance in series
with this type inductor for best performance.

DR.RESONANCE-at-next-wave-dot-net


----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: new power transformer (variac as ballast)
> Date: Tuesday, September 01, 1998 5:29 PM
> 
> Original Poster: FutureT-at-aol-dot-com 
> 
> In a message dated 98-08-31 20:46:57 EDT, you write:
> 
> << Ed,
>   
> > > Did you have to cut a slot in the core to prevent saturation?  I've
always
> > > heard this was necessary.  Does the TC draw basically the same amount

> > > of current with the variac as with the welder?
>   
> > > John Freau
>    >>
>  
> > John,
>  
> > I haven't cut a slot in it - I didn't want to ruin it for possible
future
> use.
> > Maybe I should as I think it does saturate sometimes.  I am guessing by
the
> > occasional bumps and humming that it does.  If it is rated at 40 amps,
then
> it
> > should not saturate with less than that through it, correct?  Of course
I am
> > running all the current through only about one half of it.  I am
running 35
> to
> > 40 amps through the pole transformer primary - about the same as with
the
> > welder.  Only now my safety gap across the caps does not fire. 
Possibly I
> > eliminated a 60 hz resonance problem by replacing the welder.
>  
> > Ed Sonderman
>   >>
> 
> Ed,
> 
> I think the key is that you're using half the variac, so the volts per
turn is
> kept reasonably low.  In a test I did, I drew only (less than) 3 amps
through
> a 20A variac, but it saturated, but I was using only about 10 turns or so
of
> the variac, so maybe the volts per turn went too high.  But then another 
> possibility is that the current peaks were a lot higher than 20 amps.  
> In any case, the
> system drew twice the total power with the variac ballast than when 
> using the original straight cored ballast, to obtain the same spark
length.
> I don't blame you for not wanting to ruin that variac by cutting it.
> 
> Thanks,
> John Freau
>