MOT Madness

• To: tesla-at-pupman-dot-com
• Subject: MOT Madness
• From: "Gregory R. Hunter" <ghunter-at-accucomm-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Fri, 26 May 2000 06:36:46 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Dear List,

I just tried running two unballasted series MOTs at 4800vac with a .096uF
MMC tank cap on my 4" coil, and it was a dismal failure.  It made great
sparks--for about 5 seconds.  Then the spark gap formed a power arc and the
output shrank to nothing.  The 1/4" copper tube primary and 6AWG wire
connections got too hot to touch.  The solder actually melted on my
aligator clip tap.  I think the tank current was a bit out of hand!

I had hoped that a bigger 96nF (instead of 47nF) MMC would give bigger
sparks, but they weren't much longer--maybe up to 40" (about 1 meter) max.
I got a few curved hits to the ceiling, which is about 36" above the
toroid.  Can 4800vac fire a coil?  Sure, but it needs more current limiting
than just the MOT shunts or the spark gap will turn into an arc welder
after a few seconds.

I'm discouraged but not defeated.  I'm going to try this again with a
series inductive ballast--perhaps a MOT with the secondary shorted.  I was
hoping to avoid external ballasting because I'm trying to keep it simple.
However, the tank current is simply too high.

BTW, my earlier MOT estimate of 2400vac-at-385ma is way off.  I got the
voltage right, but the short-circuit current is closer to 750ma.  MOTs
really aren't shunted worth a hoot.

Best Regards,

Greg Hunter
www.angelfire-dot-com/ga3/tesla

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