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Re: [TCML] No-load NST's
On Fri, Jun 27, 2008 at 1:27 AM, <Sfxneon@xxxxxxx> wrote:
> 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!!!)
On the contrary, I love those GFCIs :) They are a common failure point on
a NST, and I have a local shop that's giving me their broken NSTs. If the
GFCI fails it's quite a simple matter to drill out the rivets on the top and
hardwire the transformer.
>
>
> 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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