[Prev][Next][Index][Thread]

Peak cap voltage, was 12kV, 30ma TC specs, 42" spark


From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent: 	Monday, September 22, 1997 3:46 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Peak cap voltage, was 12kV, 30ma TC specs, 42" spark

In a message dated 97-09-22 01:08:07 EDT, you write:

<< 
> Hi John,
>           I may have an explanation of why the sync gap does better
> than the static. Unlike the static gap, the rotary electrodes are 
> drawing closer for a time while primary is oscillating and I would 
> think their losses are going down during this time (unlike my spark 
> blowing exercise where the losses (already high because of gap 
> distance) were being blown upwards.

Hi Malcolm, all,

This sounds reasonable, and I think there are also additional
advantages:  Using the static gaps, the gaps have to be run a little
closer than optimal to ensure steady firing, this limits the voltage
that the cap can charge to, to something below what can be reached
using the sync-gap.  It's also limiting the time available for cap 
charging, and I think this is what prevented steady 120 BPS firing
from occuring in my static gap trial ( a smaller cap may have helped
here, since I have found in the past that a small decrease in cap size
doesn't reduce the output spark much.)  Also, with wide static gaps,
the likelihood of "skipping" a firing is high, and that will allow the 
tranny voltage to go sky high under resonant charging conditions.  It
may be this "skipping" of firing (and the accompanying resonant rise,
that is the major cause of failure).  Often folks use extra air blasts to
help their quenching, esp. in magnifier systems.  This extra air is 
even more likely to cause firings to be "skipped", and this may explain
the frequent neon failures under these conditions.

The sync-gap never seems to skip a firing, thereby limiting the 
resonant rise to perhaps about 1.5 times the peak "normal" voltage.
It is possible that a neon tranny can withstand this voltage.  The 
regularly timed firings of the sync gap may also discourage other
chaotic resonances from occuring?

>     BTW, the neon sign people confirmed that tar tracking in neons is 
> a major cause of failure and realized straight away the implications 
> of resonant charging.

I agree that carbon tracking is a major cause of failure.  But my 
question would be; just what is it that most promotes carbon tracking?

I have seen folks destroy a neon in 5 minutes by opening their gaps
wide while obtaining wimpy 12" sparks.  Yet, I have been running my
sync-gap system for months with no problems.  I try to limit my runs
to 20 or 30 seconds, but often I have run much longer while doing 
quench measurements, etc.  This transformer has experienced 
punishing abuse before I installed in onto this TC, yet it survives.

There may be some combination of events, as mentioned above,
that allows a neon to survive in a synchronous environment.  Time
will tell how long my trannie will survive.  But even if it fails, it will
not give a conclusive answer because of three reasons;  1, the
trannie was used, maybe it was about to fail.  2, it had been punished
in chaotic TC work previously.  3, neon trannies often fail during TC
use despite all precautions (safety gaps, chokes, bypass caps, 
resistors, narrow gaps, smooth running, etc.)  So I think that only
large scale, long-term tests, will gradually give the true scoop on
how well neon trannies can survive in resonant mode sync-gap TCs. 

I do agree that a neon should not be run in resonant mode with
widely spaced static gaps; operation becomes just too erratic, and
destructive.  This sort of operation may also permit more destructive
RF to enter the transformer compared with sync-gap operation?

John Freau  

 ?
> Malcolm
  >>