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Re: MMC Success!

Hi Daniel,

At 02:36 PM 03/05/2000 -0600, you wrote:
>I finished construction on my new MMC last night with the Pansonic caps
>from Terry. They are so much better than saltwater caps! (What a shocker
>there...) I consistantly got several multi-forked sparks off the toroid no
>less than 24-inches long, showing a nice "banjo effect", which does not
>seem too bad for a 3.5-inch secondary and static spark gap.

Great!  happy to know they are working well for you!
The key is the series resistance.  MMC caps have far lower resistance (and
loss) than saltwater caps.

>
>However, I have a few questions. Using the formulae for MMC caps, I
>calculated that I should need around 33.6 nF (12 kV, 60 ma input). In
>reality, I used one-third that. Any more capacitance, and I could not get
>the coil in tune -- the secondary started to break down severely. The
>working capacitance, 11.2 nF, is around the capacitance that you would
>calculate with traditional capacitor matching methods, not the current MMC
>calculations.

The maximum LTR capacitor size the program gives is with everything
optimized to the limit.  However, I would think that you would be able to
use more than 11.2nF.  Do you have enough turns in the primary to tune
larger values.  It sounds like something is not tuning right.  You may want
to raise the secondary (like a foot) while you tune.  This should prevent
the racing arcs and allow you to safely adjust the tuning.  I would think
you should be able to tune about 20-24nF with a static gap.  You would need
a sync rotary to get the full 33.6nF.  Since the output power is directly
proportional to the primary capacitance, it is well worth your time to try
and get more strings going.  You obviously see how nice it is to be able to
adjust the primary capacitance as MMCs allow!

>
>Should I raise my secondary and try to get the system in tune with the
>higher capacitance, or is that just too much power to put through a
>3.5-inch secondary? I think am already pushing the limit on the sprark
>length -- streamers are going well past where a strike rail on the primary
>ought to be.

Yes, raise the secondary if your getting racing arcs.  The power loss is
very small and racing arcs can do a lot of damage.  You don't say how tall
you coil is but if the arcs are obviously getting too long for the
secondary length, may be time to wind a longer coil.

>
>Either way I am happy, the 3.5-inch coil is working great, and I can use
>the additional capacitance on my 6.5-inch coil that is 75% done. But, it
>would be nice if I could push my small coil a little further.

Raise the secondary and try to tune with more capacitance.  My 9kV/30mA
coil uses 24nF at 12kV firing voltage so there should be plenty of room for
more capacitance on your coil.  Once you have found the best point, you can
carefully lower the secondary in steps to get the best arc output without
racing arcs.

Cheers,

	Terry


>
>Any input is very welcomed,
>
>Daniel Lockhart
>
>