Re: Transformers

> >From kcravens-at-sound-dot-netSat Jul 27 20:48:34 1996  
> Date: Sat, 27 Jul 1996 16:21:47 -0500 (CDT)  
> From: Ken Cravens <kcravens-at-sound-dot-net>  
>  What I want to know is, after running for about 10 minutes (really 1 or 2  
> min. maximum,with cooling off in between firings) one of the neons started  
> smoking pretty good with a tar smell (understandably). The case doesn't even  
> get warm, nor do the terminals, but the primary cord does heat up a little  
> (about 18 gauge power cord) So I'm afraid they will eventually fry. I  
> understand this is not unusual for neons to burn up after enough such abuse  
> :o) I just was wonderin' if there are other (better) xformers between neons  
> and pole pigs, that would be better for tesla coil use? I'm not too sure I'm  
> ready for pigs yet, but don't wanna keep buyin' neons either.  Are there  
> smaller pole pig type xformers that can be used with 120v input? When I see  
> a pig that is 10KVA, that is 10,000 volts, but what kind of current rating  
> are they? I know my neons will work great at 1/2 or even 1/4 line  
> voltage...can I use a pole pig the same way? (lower input for lower output)  
> Any info will be much appreciated! Thanks!  
>                              Ken Cravens  
If you are running all four neons on one 18 gauge power cord you are going to 
start a fire.  For the transformers you are using that's 18 amps on the primary
side!  You need at the very least #14 AWG.

Yes there are other choices in between a neon and a pole mount.  PTs,
short for potential transformers, are used in high voltage metering to step
down the voltage to 120 volts.  They are typically found in 60:1 or 100:1 ratios,
with 7200 and 12000 volts being very common distribution voltages.  They are 
usually rated around 1.5 KVA a piece.  They are not current limited and will
reqire a ballast just like a pole mount.  There are smaller pole pigs with
5KVA ratings, but they aren't very common and would be hard to find.

When you see a pig that is 10 KVA, that is not 10,000 volts.  That is 10,000 volt-
amperes.  Roughly the wattage rating of the transformer.  A 10KVA pot
can come in any voltage from 2400 volts on up.  Typical voltages would be
7200, 12,470, 13,800, and 14,400.  The current available would be the 10,000 volt-
amperes divided by the rated voltage.  The 10 KVA rating is for distribution
system use 24 hours a day.  You could run one of these in excess of that rating
for short periods of time.

Yes, a lower voltage input will equal a lower voltage output.  The turns ratio
of the xformer never changes.  A 12000 to 120 volt xformer has a turns ratio
of 100:1 and the voltage ratio will always be 100:1.

-Mike McCarty