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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
>