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Re: Neonics wonderland!!!!

At 09:28 PM 6/10/99 -0700, you wrote:
>
>  Dr Resonance, All -
>
>  Would you hazard a guess as to what wattage the 15 KV  60 ma NST's would
>produce in Tesla coil operation? This is not a trick question. I have been
>contemplating this question for some time but so far have not come up with a
>reasonable answer.
>
>  John Couture
>


Hi John,

	There is a simple way of finding this that gets around all the distorted
waveforms and phase angle problems associated with trying to integrate the
real wave forms.  Simply find the firing voltage and calculate the energy
in joules stored in the primary cap and multiply by the break rate.

P = 0.5 x Vfire^2 x Cpri x BPS

In my LTR coil:

Vfire = 20500 volts
Cpri = 28 nF
BPS = 120
so the delivered power to the tank circuit (the transformer and protection
filter burns off some power) is:

0.5 x 20500^2 x 28e-9 x 120 == 706 watts

	I use a typical 15kV / 60mA transformer.  I should point out that in this
configuration the RMS current from the transformer is around 85mA and the
peak voltage is 21.8kV.  So the voltage is close to nominal while the
current from the transformer is about 41% over the rating.  However, my
runs are not real long and it is a new transformer run at room temperature
so it should do fine even though the windings dissipate 41% more heat than
they are really designed for.  Neons are, of course, over designed to
withstand the harsh environments they normally work in.  However, old
second hand devices my be at the end of their life anyway...

	It should be noted that the system runs that 85mA (actually it is 94mA
because of the filter caps which adds another 16 watts...) from the
transformer through two 5K ohm filter resistors that burn off another 72
watts bringing the total delivered power "from" the transformer up to 778
watts.  The windings (secondary) in the transformer are dissipating a total
of 35 watts.  With 10.6 amps RMS going into the primary (which dissipates
another 27 watts) the total power into the whole thing totals 805 watts
(really 821 watts...).

	If one simply multiplies the RMS voltage by the RMS current you get 1272
watts (10.6 x 120 = 1272).  However, that does not take into account the
phase angle and the distortion in the current waveform.  If one assumes the
voltage and current are pure sine waves, the input phase angle could be
assumed to be 50 degrees.  However, the 900VA nameplate rating of the
transformer is exceeded by 41%.  I guess you could say its running with
"enhanced" performance. :-)

At least, that's my "guess" ;-)

Cheers,

	Terry