Dear coilers,
Thanks for all of your replies! I was afraid that you would say that
the caps wouldn't work. After i posted last night, i made some adjustments
(mostly to my grounding rd and object i was attempting to strike). I was
able to get a nice little corona off a sharp point and 1 1/2 inch sparks.
But that still is much smaller than i would like.
It is really unfortunate that they won't work, because i was able to pick
them all up for free! all together weigh about 26 lbs and fit on a 1.5 x
1.5 piece of plywood.
Yes, like i said, they are ALL in series. they range from .55 uf to .77
uf. I realize that the .55's are taking more voltage then, but almost all
of these are rated at 2100 WVAC, and with 80 in series, certainly the
voltage is dropped sufficiently, correct? I did in fact do the math on how
to set up the bank, using the formula : 1/C(t) = 1/C(1) + 1/C(2) + ...
1/C(80) (parenthesis indicating subscript).
I'm not exactly sure how to "give you output file". I used the calculators
at deepfriedneon. If you would like, i can put my numbers back through,
and give you all the info. Also, what do you mean that this cap value
leads to a resonance problem? Please explain, as i would not like to have
to find another NST.
There is another option for a capacitor. Before building a MOC bank, I
built a plate capacitor. I kind of need something to show tomorrow (I'm
going to the state fair, although thats not the reason i built it) so my
father (I'm 15) thinks it would be an amazing idea to rebuild it, because
it failed when we tried it the first time. Its problem is that it was
filled with mineral oil, but sprung a leak. We decided to test it dry (I
smack myself every time i think of it) and one plate arced on the surface
of the glass to the lead on an another plate. We were able to refill it
with oil, but even so, there must have been a carbon path still
conducting, because the spark gap wasn't firing, and there was a faint
glow in the capacitor (we made the sides out of plexi-glass, so it was
see-through). If we cleaned of the plates, and remade the container so as
to be oil-tight, do you think it would be a viable option?
Again, thank you for taking the time to read this, and please ask if there
is any information i may have forgotten to give you.
One last question: I forget, how do you post picture links in these
mailings? A picture is worth 1000 words, and i have a lot of pictures of
various parts of my tesla.
Thank you!
Sincerely,
Joel Torgeson
________________________________
From: Quarkster <quarkster@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Saturday, August 22, 2009 10:21:45 PM
Subject: Re: [TCML] Tuning, Capacitors, and Spark Gaps
Joel -
Before delving into a detailed troubleshooting process, please provide
some additional information on your coil.
Did you use a Tesla coil design program to determine all the electrical &
mechanical parameters? If so, please post the output file, showing ALL the
parameters for ALL the components. This will allow List members to perform
a quick "design review" and look for any obvious design problems.
You mentioned that your tank capacitor is made from a large number of
microwave oven capacitors. This may be a problem, because they probably
will not be capable of withstanding the peak current seen in a Tesla coil
tank circuit.
Also, you stated that your target tank capacitor value is .0088uF, for a
9kv/30ma NST. This capacitor value yields a resonant condition with this
particular NST, which can cause extremely high voltage conditions that can
instantly destroy either (or both) your NST and your tank capacitor. What
you want for a static-gap system is a "larger than resonant" (LTR)
capacitor value, typically 1.3 - 1.5X the resonant value.
A few additional questions on your capacitor array:
1. Are all 80 of the capacitors connected in a single series string?
2. Are all the capacitors the same capacitance value?
a) If so, please provide the value.
b) If there are various values, please list the values, and how many
capacitors of each value are used.
Unless your capacitors all have a value of 0.7uF, I don't see how you
achieved your .088uF target value.
Regards,
Herr Zapp
----- Original Message ----- From: "Joel Torgeson"
<joeltorgeson@xxxxxxxxx>
To: "Tesla Mailing-list" <tesla@xxxxxxxxxx>
Sent: Saturday, August 22, 2009 3:19 PM
Subject: [TCML] Tuning, Capacitors, and Spark Gaps
Alright,
I've now built my tesla coil, and am very disappointed that it fails
to work. My transformer is a 9,000v 30ma NST. I have tailor-built my
capacitor out of capacitors from microwave ovens. They are internally
resisted, and with 80 of them in series i hit my target capacitance of
.0088 uf. My primary consists of 1/4 inch copper tubing spaced 1/4 inch
between each winding. there are 15 turns of tubing in a flat pancake
configuration. My secondary consists of approximately 760 feet of 24 AWG
magnet wire wrapped around 3.26 inch outside diameter PVC pipe. The
topload is of the tubing and pie-pan variety, using 3 inch aluminum
tubing/ducting. This makes a ~ 15 inch toroid on the top. i am using a 8
ft grounding rod that isn't attached to anything important. There is no
metal inside the secondary, so that isn't a problem. My biggest concern
is the spark gap. It's a static gap, not split up into multiple gaps,
just one big one. it is 5.6mm wide, and has a
hair drier running on cool temp, high velocity blowing on it for
quenching.
There's all the numbers i have, now i need some advice. I have been
trying to tune it in for 2 days, and all i can get is the occasional 3/4
inch spark (usually no more than 1/2 in for rapid sparks). It does light
up a broken fluorescent bulb, and as i said, it makes some small sparks,
but i didn't spend all that time and effort to create something my Van de
Graaff can beat!
So, does anyone see anything obviously wrong? Any suggestions,
comments, tips, or (yes) criticisms would be much appreciated.
Sincerely,
Joel Torgeson
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