Hi Connor,
Congratulations on not zapping yourself, YET.
With resistors running about 1-2 cents each in bulk, I can't see that
it is a major expense for added safety.
Many older coilers (30-yr experience+) believe they got to be that way
by using both a J-stick AND discharge resistors.
Using 20 10-meg resistors would "waste" three MILLIWATTS per string.
I find it hard to believe that you could really notice a loss of 0.006
watts out of 2880 watts total.
That's about 0.0002%! Seems like a very small price to pay for the
added safety.
Matt D.
-----Original Message-----
From: CONOR WHYTE <cjwhyte@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sun, 17 Aug 2008 11:37 pm
Subject: Re: [TCML] mmc cap protection by spark-gaps-any ideas?
I don't use resistors on my MMC. I find these waste energy and cut
down on my
spark length. I use CDE 942C series 1.6Kvdc 680nF capacitors, I use
20 per
string 34nF @ 32Kvdc x2 . I run 12Kvac @ 240mA. I have been running my
MMC now
for 2 years and have had 0 problems.
Quite often many people are scared about residual charge in the cap
bank this is
why people add the resistors. It bleeds charge away after the unit is
turned
off. You can do this with a discharge wand MUCH cheaper.
Like I said I have never used them. It is a waste of energy.
If you feel like you want to protect your cap bank, I'd might make an
extra gap
that one could adjust.
maybe say to be safe a 3.5cm gap 35Kv. I would also make sure the MMC
total DC
rating is around 3x that of the input voltage. 12Kvac -- 32-36Kvdc.
Another
factor I would also check is the tolerance rating of the capacitors
most are
5%... which is ok... CDEs on the other hand are 10% and can handle
much more
voltage spikes.
----- Original Message -----
From: vatercox@xxxxxxx
Date: Monday, August 18, 2008 10:47 am
Subject: [TCML] mmc cap protection by spark-gaps-any ideas?
To: tesla@xxxxxxxxxx
Dear List
I have 30 x 47nF polypropylene metal foil caps, each rated at 2
kVDC
which I intend to wire as three strings of 10 capacitors for
approximately 14nF at 20kV DC. While normally each capacitor in
an MMC
would be protected by a 10- or more megohm high voltage resistor
these
have proved difficult to obtain (due to lack of demand?). In liu
of
this would it be possible to protect each cap with a miniature
spark-gap -perhaps a pair of closely-positioned stiff wires
connected
to the capacitor leads notwithstanding the fact that 2 kV is
usually
regarded as a bit on the low side for satisfactory spark-gap operation
Jolyon Francis Vater-Cox
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