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Re: [TCML] mmc cap protection by spark-gaps-any ideas?
Sorry I should have been clearer. I was tired (2am)
I used some "bulk" resistors that were available at the time and they were NOT that cheap. (added expenses gas charge and 14.5% tax.) Yes I did notice a drop in output, maybe 4-6 inches. (maybe it was the resistors? I don't know but according to the formula I must have had very bad or poorly labeled resistors.) I never went back to using them. After I got rid of the resistors I noticed a little increase. ---
I hope that makes a little bit more sense now ?
I agree, Matt it is ideal to have the added safety. Again if I need to make any changes between firings I discharge the capacitors manually.
Again sorry for the confusion.
----- Original Message -----
From: mddeming@xxxxxxx
Date: Tuesday, August 19, 2008 12:42 pm
Subject: Re: [TCML] mmc cap protection by spark-gaps-any ideas?
To: tesla@xxxxxxxxxx
> Oops,
> I dropped a term, Sorry.
> P=E^2/R=12,000x12,000/200,000,000=144/200=720mw/string,
> or 1.44W out of 2.88KW, or 0.05%. Sorry for the carelessness,
> but it
> still makes the claim of waste seem pretty farcical.
>
> Matt D.
>
> -----Original Message-----
> From: mddeming@xxxxxxx
> To: tesla@xxxxxxxxxx
> Sent: Mon, 18 Aug 2008 4:42 pm
> Subject: Re: [TCML] mmc cap protection by spark-gaps-any ideas?
>
>
> 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 m
> ore 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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