RE: safety gaps at high power

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

Original poster: "R.E.Burnett by way of Terry Fritz <twftesla-at-uswest-dot-net>" <R.E.Burnett-at-newcastle.ac.uk>


Hi John, all.

If a sync gap motor looses torque and falls out of sync,  this can result
in a considerable resonant rise in the charging circuit and excessive tank
voltages.

The worst case is if the electrodes of the rotary happen to line up when
there is no voltage present to fire across the airgap.  The capacitor
voltage is then free to ring up to a very high voltage if a safety gap is
not fitted !

I have observed this in practice.  At last years Teslathon,  my rotary
motor failed during a full power run.  This resulted in three things:

1. Instant barking of the safety gap,
2. A few sporadic long sparks,
3. Frantic arcing along the length of the secondary,

I cut the power very quickly and fortunately nothing was damaged.

FWIW, I have never seen a problem with a safety gap "sticking on" even at
high powers.  I think it might depend on the tank cap and ballast values.

							Cheers,

							-Richie,
On Sat, 6 Jan 2001, Tesla list wrote:

> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net>
> 
> 
> John F. -
> 
> You stated "If the gap slows down and the voltage starts building up
> resonantly". I believe this is a possibility and have mentioned it in the
> past but I have never made the tests to prove it. Have you or any other
> coiler made these tests?
> 
> Variations in the gap operation would account for the various random spark
> lengths issuing from the secondary terminal. This results in a varying
> output load which makes the typical random spark output of little use for
> engineering purposes.
> 
> This is why I am encouraging the use of another type of test and that is
> using the controlled spark test. These are the types of tests that are
> needed to arrive at a resonable "watts per foot of spark" rating to
> correctly compare tesla coils.
> 
> John Couture