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Re: [TCML] No-load NST's



Hi Gary,
 
I believe that NSTs are designed pretty well for their _intended_ purpose,  
although there seems to be a lack of quality control in the manufacturing  
process. This leads to some NSTs being nearly bullet proof, while others of the  
same make and kind will fail unexpectedly. I would imagine that the biggest  
problem is due to the potting methods and materials used most frequently.  
Anything except vacuum impregnated coils, or the whole core and coil assembly,  
just won't have a consistent quality at that kind of voltage, and there's  no way 
to tell what you have until it fails.
 
The transformer manufacturer has to walk a thin line between profit and  
reliability, and find an 'acceptable' failure rate THEY can live with. In  other 
words, it's usually cheaper to warranty a few transformers, than to make  them 
as reliable as possible. I suppose they are made on a continuous assembly  
line, and vacuum impregnation would likely be a batch process, which would add  
too much time and cost to an already expensive product. (Damn those  mandatory 
GFCIs!!!)
 
It's also interesting to note that the USA is about the only country to  make 
and use neon transformers with an output over 10 kV. Almost every one else  
has learned that insulation breakdown, both inside the NST and the external  
secondary wiring, becomes a real problem with anything over  that.
 
I wouldn't put much faith in those purple energy angels for my NST. Accept  
only "Genuine Tesla Purple Energy Discs" for your coiling protection! :)
 
Tony
******

In a message dated 6/26/2008 11:06:01 A.M. Central Daylight  Time, 
Gary.Lau@xxxxxx writes:
Hi Tony,

Thank you for chiming in and  sharing your experience.  The voice of 
experience trumps the voice of  speculation (mine) every time.

Unfortunately this does not bode well for  NST's in our (coiling) 
application, as spark gaps are routinely set to permit  voltages well in excess of the 
peak open circuit value.  And there's not a  thing we can do about it except to 
hobble performance with very closely set  gaps.  Filters (even with chokes!) 
can't help us.  Perhaps if we all  found religion and prayed to the patron 
saint of NST's.  There's the purple  energy angels so common on eBay.  That's an 
untapped market - the  equivalent of a St Christopher medallion for mounting 
atop your  NST.

Excellent point about the fence charger also.

Regards, Gary  Lau
MA, USA

> -----Original Message-----
> From:  tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of  Sfxneon@xxxxxxx
> Sent: Thursday, June 26, 2008 1:47 AM
> To:  tesla@xxxxxxxxxx
> Subject: Re: [TCML] No-load NST's
>
>  >> In a message dated 6/25/2008 4:26:25 P.M. Central Daylight  Time,
> _Gary.Lau@xxxxxxx (mailto:Gary.Lau@xxxxxx)   writes:
>
> << Yes - I too have heard many times that running  an NST with no load  will
> stress its insulation beyond what it was  designed for.  But it does  seem
> unlikely that an NST should  be designed to self-destruct should its  
connection to
> the load  fail.  So being the skeptic that I am, I have to  wonder about  
the
> origin of that belief.  Did it come from a source in the   sign or 
transformer
> industry, or just a coiler who observed that an  in-use NST  with a sign 
operates
> at well below its faceplate  voltage?
>
> Gary Lau
> MA, USA  >>
>
>
> Gary, all,
>
> It's common  knowledge in the neon sign trade that operating a neon
> transformer for  extended periods of time with no load, such as a with a 
broken   tube
> or
> wiring, _greatly increases_ the chances of a secondary  insulation  failure,
> not only inside the transformer but also in  the secondary wiring  itself.
>
> I have owned and operated a  commercial neon sign shop and plasma art studio
> for almost 30 years, and  I can say without a doubt that this is true. I'm 
not
> saying that _every_  NST run open circuit will fail, just that it greatly
> increases the  chance the longer it runs. In fact, this just happened to a  
neon
>  transformer on a border tubing installation at my own shop. I failed   to
> promptly fix a bad tube, and about a week later the transformer went  bad 
too.
>
> So, it's not likely that you are going to kill your NST  if you happen  to
> hook it up without a load, unless you leave it  that way for days, weeks or
> months. What really kills them in TC usage  is opening up that spark gap 
too  wide,
> or the voltage ringing up  to insane levels if the gap misfires a time or  
two.
> They really,  really don't like any capacitance across their output,  even
>  extended GTO runs or GTO in metallic conduit.
>
> >> In a  message dated 6/25/2008 7:20:42 P.M. Central Daylight  Time,
>  _evp@xxxxxxxxxxxx (mailto:evp@xxxxxxxxxxx)  writes:
>
>  << I ran a "skunk zapper" electric fence for
> several years  which  was powered by a 9 kV, 60 ma NST. >>
>
> PS: A  word of caution about using a NST for a "fence charger"! Common
>  practice...but bad idea. IT'S LEATHAL, not only to small animals, but  
humans  too!
> Real fence chargers send out a high voltage microAmp  pulse about once a
> second, which smarts like hell, but won't cause you  to go into cardiac 
arrest or
> become unable to let go of a 'hot' fence  wire. They will also not produce 
a hot
> enough or long enough duration  spark to burn you or set the 
grass/weeds/house
> on  fire when they  finally get that tall.
>
> However, your NST _WILL_ keep the skunks  out!! :)
>
> Tony Greer
> Special Effects Neon
>  Lubbock, Texas
> *************************
 



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