Re: Battle of the Capacitors

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Sundog,

Thanks a bunch for this very interesting test you did!!!!  This is one of
those posts that will serve to answer that "how good are MMCs question" for
years to come!

Cheers,

	Terry


At 01:39 PM 12/26/2000 -0500, you wrote:
>
> Hi all,
>
> Did an impromptu test over the holidays.  I have my polepig up and running
>on 120v (the 240v drop is coming along slowly), running ~2.5kva.  I'm using
>a 240bps sync gap, and an 8" coil.  Comparison was by the gap sound and
>streamer quality (length, power, etc)
>
> On the testbed was a 35kv30nf Maxwell, a 16.7kv35nf MMC (panasonic caps),
>and a 30kv34nf cap (3 10kv .1uf caps in series).  The gap was left at the
>same position for each cap, as the capacitancies were pretty much the same.
>Yep, I know I'm seriously overvolting the MMC with a 14.4kv polepig, but
>what the hey, it's all in fun!
>
> The MMC gave a nice rich sound.  There was no heating of the cap bank, and
>performance was good.
> The 3 10kv caps gave the gap a bit sharper sound, and also did not heat.
>The streamers were maybe 1-2" longer (measured byfrequency of hits to a
>grounded target just inside of strike range).
> The Maxwell gave the gap a very sharp, harsh sound.  Again, no heating of
>the cap. The streamers grew ~1" longer with the Maxwell.
>
>  The MMC is the biggest of the caps as far as actual bulk goes, followed by
>the 3 10kv jobbers, then the maxwell (roughly the size of a brick).
>
>  So there isn't much difference between the performance of the caps.
>Cost-wise, I spent $1.40 on each Panasonic cap(7 strings of 11), and about
>$10 to mount them. Right around $120 for a 16kv35nf cap.  I spent $40 each
>on the 10kv .1uf caps.  Flattened 1/4" tubing for interconnections, so I'm
>figuring ~$125 for a 30kv34nf cap.  The 35kv30nf maxwell was about $130 when
>all was said and done.  Pricewise, they are about the same (a new maxwell
>will almost certainly cost more).
>  Repair wise...I have 4 of the 10kv caps.  That means I have 1 spare.  If
>the Maxwell blows..well..I'll probably cry a bit and start hunting for
>another.  The MMC...I have some spare panasonics hangin' out on my workbench
>for the "oopsies" when (and if!) they occur.
>
>
> My conclusion now that i've run the caps at low power level,
>   The MMC is probably the cheapest for most people, as I lucked up on the
>other caps.
>   The professional-cap MMC (big caps in series/parallel) will probably
>handle current better.
>   The professional single cap holds the size advantage, but you're stuck
>with the values you get.  And you can always use more capacitance ;)
>
>    So unless you luck up on a pro cap(s), go MMC!  The actual performance
>difference is nothing to write home about, and you end up with a cap that's
>easily stackable to whatever voltage/capacitance you need.  And once the
>240v drop is in, we'll see how MMC's run at the multi KVA levels. (like
>5-15+kva!)  I've got a polepig and a 60A breaker, and I'm not afraid to
>chunk 'er wide open!  =^))
>															Shad
>