RE: Neon Sign Transformers (was: spark length formula needed*)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>


Jim, All -

Your description of the NST as being "a big inductor in series with the
output" is a good one. In my tests the NST output load was an RC circuit. I
don't have my notes handy but the load was one that had small resistance and
large capacitive reactance. In other words very low power factor. The input
on the other hand had very good power factor, that is a low resistance but
also low reactance.

I believe that the above tests are an interesting representation of the
typical TC system using HPF NSTs. Of course the intermittent operation and
resonance is missing, however, the power factors and VA relationships can be
studied. It appears that some coilers have already looked into this aspect
of coiling. It should be noted that the real part of the secondary current
has a big effect on the spark length. In other words a high power factor is
better. But how do you achieve this in the design of Tesla coils?

I was also thinking about your comment regarding the primary circuit, that
is, that it "is outside the LC loop (secondary)".  This means that if the
NST was a 1:1 transformer (120 volt primary and 120 volt secondary) the
total current in the primary circuit could be less than the total current
circulating in the secondary circuit. In my tests the voltages were not the
same so the differences in VA involved both voltages and currents. Has any
coiler ever checked the power factor of both the primary and secondary
circuits of a TC at the same time?

John Couture

--------------------------------

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, December 24, 2001 10:21 AM
To: tesla-at-pupman-dot-com
Subject: Re: Neon Sign Transformers (was: spark length formula needed*)


Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>

ALmost certainly could be true.. consider the NST as basically an ideal
transformer with a big inductor in series with the output.  The load is R
and C.  There will be signficant reactive power in this set up which a
secondary ammeter would show.  The primary, on the other hand, is outside
the LC loop, so it won't measure the reactive current..

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, December 23, 2001 8:51 PM
Subject: RE: Neon Sign Transformers (was: spark length formula needed*)


> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
>
>
> Jim, All -
>
> The Tesla coil circuit is an RC type of load on the NST secondary. My
tests
> of NSTs indicate that under certain conditions the VA input to the NST
could
> be smaller than the VA output to the TC. Has anyone ever checked this
> possibility for a Tesla coil?
>
> John Couture
>
> -------------------------------
>
>
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Sunday, December 23, 2001 4:58 PM
> To: tesla-at-pupman-dot-com
> Subject: Re: Neon Sign Transformers (was: spark length formula needed*)
>
>
> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <jimlux-at-earthlink-dot-net>
>
> You could also have bigger volt amps on one side than the other because of
> reactive power circulation.  Consider an inductor and capacitor in
parallel
> across the AC power line (resonance not necessary, nor desired).  The
volts
> is the same everywhere.  However the current drawn from the line will be
> substantially less than the sum of the currents through the inductor and
> capacitor.
>
> measuring true power (Watts) rather than apparent power (Volt Amps) will
> make everything come out right...
>
>