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Re: [TCML] BPS Testing

Hi Gary, I agree. That is a whole avenue all by itself. However, I get the "feeling" from the data that the arc is far more consistent than we might ponder. I've noticed in my testing a rhythm of sorts to the breaks. There are times when the gap runs normally and times when it doesn't and there's a rhythm to it (but I need to be able to record much longer periods). here are areas in the data where the darn thing runs exactly as expected. Then, the quick breaks occur, go away for a while, then come back, etc. I think this may have to do with spark loading.
One thing I noticed was that I had only 1 single missed break event out of the entire series early on (so I can pretty much ignore it). That was good to see. My issues are with the breaks that occur immediately after a break. 1ms quickest, 4ms is average when this occurs (equivalent to double the transformer current rating at those points). It may be that we edge into saturation for a period and this is the cause. If it is "ion density" of sorts, I would have expected a more frequent and rather "steady" occurrence, but I'm not seeing that. My gut is telling me either current is periodically climbing or the conduction stopped and re-ignited. But that is just my gut feeling. 

Take care,
Bart

Lau, Gary wrote:

Hi Bart,

As if things weren't complex, chaotic, and muddy enough, one further thing to ponder is whether the gap breakdown voltage does in fact remain consistent from bang to bang.  I have often wondered if in a static gap, if one bang closely follows another, if the likely greater concentration of ions (really not sure of their persistence) or just hot gasses or O3/NOx may affect and lower the subsequent bang's breakdown voltage. It's something that I can do with my scope and fiber optic probe, but just gotta get a round tuit...

Regards, Gary Lau
MA, USA


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of bartb
Sent: Wednesday, March 12, 2008 9:35 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] BPS Testing

Hi Gary,

Lau, Gary wrote:

As I had mentioned, I had measured the NST's short circuit current and found it

to be not far from the faceplate rating of 60mA (I don't recall the exact number).
Low voltage side (primary?) short circuit current???  I don't think that winding
resistance measurements would indicate much.  I have not tried measuring the
open-circuit voltage as I have no reason to suspect that it differs significantly from
the faceplate rating.
Well, then it's certainly a 60mA unit. I like to measure my NST's data 
as much as possible to know what I'm working with, especially for these
type of situations. Winding resistance does tell us impedance
information, although it doesn't change a lot from the face place
equated impedance (but a little). Gerry Reynolds helped iron out the NST
impedance with Javatc allowing users to measure winding resistances
(which almost everyone can easily do) and helps get just a little closer
to reality.

Today I looked at the nearest break to break occurrence with my 15/60
test. The break occurred 1.1ms after the quench of the first break. This
would require a 400mA continuous charge to get back up to the arc
voltage in order to break 1.1ms later. That just seems much to ask from
an NST and I'm not sure ferro resonance will do that (maybe). I know
ferro resonance causes extreme voltages in cables and equipment, but
there is usually a good reason for it (it's just not that easy to find
the reason and that's where it gets difficult). Transformer saturation
is one of those situations that can cause it.

I also looked at the entire 12.7 second measurement data today and
counted number of "soon after" breaks. I don't have the info in front of
me, but it was something like 83 occurrences. If I removed those 83 from
the total 998 breaks during that period, bps equated to 72. There is
something here that's real. It shows that charge time of caps up to the
firing voltage is as it should be, but there are these series of breaks
that occur soon after for some reason (either ferro resonance or
possibly a partial discharge and then re-ignition). It has to be one of
those two reasons.


Looking forward to your 140VAC measurements!


I'm looking forward to it also.

Take care,
Bart


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