[Prev][Next][Index][Thread]

# Re: MMC Cost VS One Cap

```
Hi Bill,
if you do consider the mmc option if you join the uk bulk buy you
can get 47nF 1500V 4500V/us caps for 45c each.

Regards
Nick Field
> Hi Bill,
>
> I haven't said anything about this so far because it is complex...
>
> At 10:44 AM 02/10/2000 -0500, you wrote:
> >
> >Greets All,
> >
> >1) Is \$180 to much to pay for a 0.01uf high voltage
> >tesla cap, brand new -- 15KVAC rms?
> >FYI it is from plastic capacitor coporation.
>
> "I" would not pay that. A handful of poly caps could do the same thing in
> most cases.  There are three things you have to know:
>
> 1. The peak voltage needed.
>
> 2. The RMS current level the cap will have to handle
>
> 3. The cost of various options.
>
> The first question is easy.  A 15kV RMS transformer puts out 15000 x
> SQRT(2) = 21200 volts peak.  If you can get 1600 volt DC rated poly caps
> you could use 13 per string to get that (I use 10 with no problem).
>
> The current is a bit tricky but even the commercial cap will fry if it is
> run with too much RMS current going through it.  Be sure to tell the
> manufacturer the frequency of your coil and the RMS current the cap will
> need to handle.  RMS current is a big deal for caps but we always worry
> about voltage (easy) and forget the current will kill them just as fast.
> Current used to be really hard to determine but the following link will
> help you out there:
>
> http://www.peakpeak-dot-com/~terryf/tesla/misc/MMCPower4.html
>
> You could probably get away with four strings fine.  So you could have 13
> caps per string in four strings.  Some math will tell you that is 32.5nF
> per cap to get 10nF.  You need 52 of them.
>
> Whipping open your DigiKey catalog for 33nF 1600 volt poly caps gets you
> \$21 per ten.  So you need \$110 worth of them.
>
> However, it gets even more fun.  If Terry hadn't run out of the 56nF caps
> for \$1.40 each, you could probably get by with two strings of 11 caps.  22
> caps at \$1.40 gives \$30.80 for your cap!  That is 1/6th the cost of the
> commercial cap(plus \$10 for other bits and pieces).  It might blow up (it
> will probably do fine)??  but at that cost, who cares...
>
> MMCs can be made right on the edge of destruction for very little money or
> they can be made bullet proof (fail safe in fact) for real money.  I doubt
> any commercial cap could be made cheaper than an equivalent MMC.
>
> But the choice is yours and the commercial cap is quick and easy where an
> MMC takes time to figure out...
>
> Cheers,
>
> Terry
>
> >
> >2) Is the above mentioned cap powerful enough to handle
> >a 15KV 60ma NST or maybe later on a 120ma NST?
> >
> >3) Home much does it cost to build a MMC 0.01uf with
> >the above ratings?
> >
> >I like the sounds of the self discharging MMC.
> >
> >3) Can a single cap have a bleeder resistor?
> >if yes then what would be the ratings of that resistor be?
> >
> >Many Thanks,
> >Bill Parn
> >
>
>

```