From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: RE: need help/capacitors and AC
Date: Thu, 03 May 2007 00:18:03 -0600
Original poster: "Scott Bogard" <teslas-intern@xxxxxxxxxxx>
Matthew,
I have never built an MMC, but I researched them, as I was
going to build one. What is the voltage rating on your caps? 1200
seems like an awful lot of caps for an MMC (to me at least),
especially considering you are using an NST, which probably has
fairly low current (30, 60, or 90, mA). Re-run your calculations,
{V=V1+V2+Vn..., and C=1/((1/C1)+(1/C2)+(1/Cn)...)} and if you get
the same results, consider using different MMC caps (like the 942C
rated at 1500 or 2000 volts). I would say, using the 2kV, you
would need about 20 some, for a small 3 in. coil, and maybe a
little more for a bigger coil, or a higher current supply (not 1200
capacitors). Plus remember, one can generally push the operating
voltage of the caps a little beyond what they are rated (if you
don't mind replacing one once in a while), but be careful, use peak
voltage (15kV/.707) to calculate the necessary voltage rating of the capacitor!
Anyway, to answer your second question, I believe it works like
this, as your frequency increases, your maximum current must go
down (that is how it works with Maxwell caps, or so says the
company that makes them).
Voltage breakdown is irrelevant (not really, but for your purposes it is).
To answer your third question, generally NSTs are 15kV from
terminal to terminal (one is +7.5 kV, the other is -7.5 kV, and
then they switch as the AC cycle progresses). Remember this is RMS
voltage, use peak for calculating you capacitor voltage
(RMS/.707). I hope this helps.
Scott Bogard.
From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: need help/capacitors and AC
Date: Wed, 02 May 2007 18:40:07 -0600
Original poster: "Matthew Boddicker" <shmerpleton_town@xxxxxxxxxxx>
This is Matthew Boddicker
I am currently designing a MMC, but I need the right capacitor for
the job. I am going with cornell-dubilier caps, but my recent
calculations said that I would require around 1200 caps for a MMC.
My question is how does a capacitor react to different frequencies
of current? the cornell-dubilier web page says that the cap can
handle 500Vac at 60Hz. if my circuit for my coil operates on a much
higher frequency will I require a higher ac voltage rating or a lower one?
last question but equally relevant. My NST's output is 15,000
volts, is that the voltage between both output nodes or is 15,000
the voltage between one node and ground?
Thanks,
Matthew Boddicker
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