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Re: safety gaps at high power



Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 1/14/01 1:14:34 PM Pacific Standard Time, tesla-at-pupman-dot-com 
writes:

<<  "Edward Wingate by way of Terry Fritz <twftesla-at-uswest-dot-net>" 
<ewing7-at-rochester.rr-dot-com>
  >>

<< My magnifier uses a 14400 volt pole transformer ballasted with an arc
welder alone and will exhibit the same tendency to power arc the
transformer safety gap when I slow rotary gap to approximately 7000 RPM
or less from the normal 7500 to 8000 RPM operating range when the
voltage input to the system is at the maximum 235 volts. >>

Ed,
My classic Tesla system basically has the same power supply
that you have (14400 volt, 10 kVA pig ballasted with an arc welder
only) but my rotory RPMs are much lower. My twin rotory discs
each have (6) 3/8" dia brass rotory electrodes and the the motor 
turns at a max of 3450 RPMs and I usually run around 3000 RPM.
So, I guess I would definitely have that problem since yours starts 
to exhibit this property at < 7000 RPMs. I never thought about a 
lower motor speed causing this. I also use a 12 kV rated utility
line lightning arrestor in parallel with the pig's output to the Tesla
primary circuit and this really helps to clip the overvoltage spikes
generated by the tank circuit. I think a slightly higher voltage rat-
ed arrestor would work a little better though, as it starts clipping 
before I reach the full input voltage with my variac. I haven't installed
a safety gap across the terminals of my capacitor. It is rated at
84 KVDC and the max. clearance between the opposite terminals
is about 2". I don't think it could exceed an 84 kV potential with
only this much clearance without the terminals flashing over to ea.
other, so I think the installation of a safety gap across the cap. ter-
minals would be moot with my setup.

David Rieben