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Re: Capacitor Help
Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
At 12:54 PM 12/12/2005, you wrote:
Original poster: "C. Sibley" <a37chevy@xxxxxxxxx>
I'd go with a Maxwell pulse capacitor. The can be had
on e-bay for around $100 and are well worth the $$$.
The have very high peak current and very low
inductance. If this is your first coil (and not your
last) you will have room to grow as you build more
powerful coils...
Search e-bay for "Pulse Capacitor" and look for the
big square white block type capacitor.
Curt.
there's a remarkable variety of Maxwell caps out there, some not
suitable for tesla coil use (RF current rating is too
low). Furthermore, if you're buying off Ebay, you might not have any
information on the previous history of the cap (for instance, is it
at the end of its rated life?).
That said, there are some really good caps out there.
For a first coil, though, you have two fairly bulletproof ways to go:
1) beer bottles in a bucket of salt water. heavy, cheap, works fairly well
2) MMC, using the CORRECT kind of polypropylene capacitors. You
don't want polyester, nor polyethylene nor any other
poly-something. You also want the correct construction type that
handles higher RMS current. The "right" capacitors should set you
back about $2-$3 each, brand new, for 0.15 uF 2kV units (or values in
that range). For your run of the mill NST coil, you need to string
enough in series for the 21kV peak voltage (but be aware that they
are tough enough that you can probably run at more than rated
voltage). In any case, 10 of these $3 caps in series is $30. You
might actually want more, just to reduce the capacitance to stay away
from resonance with the NST.
(Example cap CornellDubilier 942C20P15K 0.15 uF, 2kV.... check the
archives, or someone will no doubt pipe up with the latest scoop)