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Re: [TCML] First light (maybe second light) on mid-sized coil
Hi Gary,
Thanks for the input. Actually, I didn't necessarily mean to imply that
this was "abnormal" behavior, though, just that 80 nFd is a pretty big
honking capacitor to run on a standard 120 volt feed. I agree that there
is probably core saturation and ferroresonance going as you stated but
it seems to continue somewhat after the SG starts firing, too. Of course,
the BPS rate is NOT going to be very high with 80 nFd either. I'm still
wondering if enough PFC caps in parallel with the input to the PT would
help to reduce the current draw at all or does this approach only
work significantly for NST powered coil? I know most pig coilers
do not bother with PFC caps (myself included) since available current is
not near as limited with a 60 or 100 amp, 240 volt service.
David Rieben
----- Original Message -----
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
Sent: Wednesday, April 16, 2008 6:39 PM
Subject: RE: [TCML] First light (maybe second light) on mid-sized coil
Hi David,
I think there is nothing abnormal with what you described. It's just not a
healthy thing to do. I haven't tried it myself, but if the Variac is
adjusted to just below the point of firing, it means that the transformer is
constantly charging and discharging the cap to just below the firing
voltage, but since the gap never fires, that energy is constantly being
traded between voltage on the cap and current in the transformer secondary,
likely to the point of core saturation and ferroresonance. If the Variac
were just a bit higher, the gap would fire and the capacitor energy from
each charging cycle would have a place to exit rather than causing the high
current and avoid this problem.
Regards, Gary Lau
MA, USA
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of David Rieben
Sent: Wednesday, April 16, 2008 7:50 PM
To: Tesla list
Subject: [TCML] First light (maybe second light) on mid-sized coil
Hi all,
I have figured out that the real current hog culprit in this coil project
is the 80 nFd primary cap. I realized that as I turned the variac
up to only 30 on the dial, the SG is just at the threshold of be-
ginning to fire intermittently. If I turn the variac to this point and
stop just before the SG starts to sputter and leave it powered up
in this position for a couple of minutes, the 22 amp Staco variac
will still manage to get pretty warm and if left long enough, it will
even begin to smoke! I assume this is just the primary capacitor
load on the transformer as the SG is not even firing yet! Am I go-
ing to have to settle for a smaller primary capacitor to stay happily
within the bounds of a 120 volt, 20 amp service or just say the heck
with it and upgrade this baby to 240 volt service? Any suggestions?
David Rieben
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