Re: [TCML] NST's and ARSG's

[Sfxneon@xxxxxxx]

NSTs are very stressed when operated at anything other than their design  
ratings. They are built with little leeway for over voltage or current to keep  
production costs down on an already expensive item. NSTs can be used  
successfully in coiling, but not if you push them to the max. It's a  tradeoff...do you 
want reliability, or maximum spark length? You can't have both  with an NST! 
Just because an NST is _able_ to make sparks of a given length,  doesn't mean 
that it will do it reliably. 
 
Repeated info, but a couple of things to remember about NSTs:
 
A NST is a constant current source. It tries to maintain a constant current  
by raising or dropping the secondary voltage to match the load. That's the  
purpose of the magnetic shunts in the core.
 
Their secondary voltage rating (on the nameplate) is measured open circuit,  
while the current rating is measured short circuit...so your 15,000 Volt/30  
mA NST is rated at 15 kV _AND_ 30 mA, not 15 kV _at_ 30 mA.
 
The voltage rating of an NST is the "Striking Voltage" that the transformer  
will produce open circuit in order to initialize ionization in the neon tubes. 
 Just running them open circuit for too long can cause them to go bad. The  
instant the tubes strike, the load imposed will reduce the operating voltage to 
 about half, and the current draw should be about 80% of the nameplate 
rating.  So, a typical 15 kV/30 mA NST's job is to supply about 8000 Volts _at_ 24  
mA, into a largely resistive load. It'll do that day in and day out, because  
that's what they're built to do. Add capacitance and ring the voltage 
transients  up to 25 or 30 kV, and it won't last long!
 
Safety gaps, Terry filters and not running the NST 'flat out', will greatly  
increase the chances of it surviving for a long time, unless it's very old or  
just happens to be a 'lemon'. 
 
Tony G
 
 
 
In a message dated 6/11/2008 9:21:33 A.M. Central Daylight Time,  
pslawinski@xxxxxxxxx writes:

I'm  referring to the NST.  I haven't potted it or submerged in in  oil
yet.  This is mainly because the transformer keeps giving me  trouble
like this.  I'm beginning to hate NSTs they seem so  fragile.





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