Re: Weird safety gap behaviour

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

Original poster: "Ed Phillips" <evp-at-pacbell-dot-net> 

"Hi Ed,

I'm thinking my case may be a different phenomenum.  My capacitance is
26.5
nf and I'm at 2.5* Cres.  The thevenin inductance of the tranny is 663H
and
the thevenin resistance is 15.9Kohms.  The calculated the steady state
voltage on the capacitance is about 14500 Vpeak (assuming 21200 Vpeak
for
the Vs_oc).  The safety gaps are now adjusted to not fire so no
transients
present.

Today, Terry and I measured the PF during this event.  Driving a mostly
pure
capacitive load and before runaway, the PF was 0.17 (small as one would
expect).  After runaway, the PF was 0.97 and the line current droped
slightly.   The power seems to be mostly dissapated in the NST.  The NST
was
buzzing but not too violently.   I did note that the sine wave output
was
relatively clean before the event and became very distorted after
runaway.
The distortion apears to be odd harmonic in nature (symetry seemed to be
preserved).  A scope capture of the event shows a peak to peak growth
until
30KVpeak  is reached.

My current thinking is that what ever the nonlinear effect is,  it is
causing the effective inductance to decrease to cause the resonant
rise.  I
am studying ferroresonance to see what I can learn.

Gerry R."

Gerry:

	Certainly you CAN achieve resonance at high flux density when the
permeability is decreased after going through peak.  In my case it was
at low flux densities that I observed the phenomenon.  What puzzles me
is how your transformer insulation has withstood that high a secondary
voltage!!!!!!!  I assume you haven't run it that way for long......

	I would think the buzzing indicates core saturation, which should be
very evident in the input current waveform, which should show big
spikes.

Ed