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Capacitor Calculations
Hi All!
I've amazingly been able to get hold of a 15KVA 22KV Single Wire Earth
Return transformer from the local electricity board.
It was a decommissioned xformer which lived its life on a power pole for
several years. The core is still in good condition, but was "too old" for
power distribution purposes, so when I spotted it in the scrap yard, I
asked and recieved!
Anyway, I'm trying to work out exactly what value caps to use with this
xformer.
With Neon's I use the formula -
1
c = ----------
2*Pi*F*R
Where F = 50Hz (Aussie Freq.)
R = V/I
c is in Farads
Since the power output of the xformer is 15KVA and the voltage is 22KV,
one calculates an approx. current of 0.6A.
When I plug all of this into the formula, it gives me 0.09uF.
Strange thing is that I've seen other coils that use this sort of power
level and transformer, and they use 2 0.5uF caps in series to yeild 0.25uF.
Which ones do I go for, and is there a particular formula I should be
using for these xformers other than the above?
The next question is, how does one calculate what value an inductor RF
choke should be for this? I don't really feel like coupling 80KHz of RF
back into our power grid! :-)
Here's the Tesla coil specs that I'll be driving with this xformer -
Secondary -
12" diam
625 turns of 1mm enamel coated wire spaced at 0.25mm apart
(I know, tat tat, no spacing, but it's an old secondary from way back)
Primary -
5 turns of 3/8" copper pipe in Pancake Archimedes formation,
spaces at 3/8" between windings
ie
__ __ __
---( )---( )---( )--
~~ ~~ ~~
| |
^--------- 3/8"
Spark Gap -
Rotating 12 point gap.
1440RPM (asynchronous) and does splutter occassionally.
Wheel is 10" diam
Not the best designed coil, but should work with 10KW of power, and
should hopefully resonate somewhere between 80-100Khz.
Thanks for your help guys!
Happy Sparking!
Rod
Rodney.Davies-at-anu.edu.au