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Re: [TCML] Tesla Coil Problem: Capacitors?



Scott -

Are you sure that you are not confusing "series" and "parallel" connections?

You describe your MMC tank capacitor as using .047 @1600 caps, wired "two strings of 12 in parallel" for a value of .0078uF.

If you actually have them wired this way, your MMC value is .282uF, not .0078uF. Twelve .047uF caps connected in parallel yields a value of .564uF. Connecting two twelve-capacitor "strings" together in series will yield .282uF, much larger than what you need for resonance.

Verify how your MMC is actually constructed. Two series-connected strings of 12 capacitors each in parallel, or two paralleled strings of 12 capacitors each in series?

Regards,
Scott Hanson
----- Original Message ----- From: "Scott" <doxiescott@xxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, February 16, 2008 2:55 AM
Subject: [TCML] Tesla Coil Problem: Capacitors?


Hey there Telsa List!
I have been working on my first coil for about 4 months now and I'm almost
sure it's one issue away from sparks....
My problem is a little tricky, so I'm gonna be as detailed as possible here
(sorry for the massive post).

First off:
The coil is built around a 10kv 30ma neon sign transformer with stupid evil
GFP: Here's the description from the maker:
http://www.jcmimports-prostore.net/servlet/Detail?no=2

The spark gap is made of 8 copper electrodes, about 1-2mm spacing between
each

Primary and seconardy/topload all match and are correct size according to
the calculators from deepfiredneon:
http://deepfriedneon.com/tesla_frame0.html

The secondary and strike rail are "grounded" to a large steel spike hammered
2 to 3 feet into wet Earth.  The grounding tab on the sign transformer is
not connected to anything.

When everything is wired according up in a complete circuit and power is
added, nothing happens.  If the primary connection point is changed,
nothing.  It the spark gap size is increased or decreased, nothing.  What
gets interesting is when the circuit is slightly broken at some point (an
ark is drawn between any 2 components) it either fights to keep current
running through the cap-primary loop, or if that is impossible, it just
completes the circuit through the spark gap, ignoring the primary loop. It
won't do both actions at once (fire the spark gap while the circuit is
completed). I know the primary coil/gap is working because whenever the two
are connected (with some kind of arc in the loop) a florescent light will
light up when over the primary.

I'm almost certain the caps are to blame for two reasons: they are not
breaking down the spark gap when put in the right place in series, and when
they are removed from the circuit completely, it acts the same way.  I am
using these caps: http://www.vishay.com/docs/28124/mmkp383.pdf
(0.047uF at 1600volts, wired as 2 series strings of 12 in parallel (24 caps
total, overall rating of 0.0078 uF and 19200 volts).  Each cap was tested,
and it holds its charge under low voltage, and discharges with a spark. No
bleed resistors...yet.  The cap bank produces a different ark than the NST
when arced to the primary coil (a high pitched crackling instead of a low
hum), but this tone can only be heard at that connection.

Alright, thanks for reading so far. So what do you guys think is going on? How can I test my caps to be sure they work alright? Do you see an obvious problem with another component? I will check back frequently, so feel free
to send in ideas or questions.

Thanks a lot guys, now let's get this working!
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