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Re: Tesla Coil Power Factor

Hi John,

	I have posted 6 more pictures at:

www.peakpeak-dot-com/~terryf/tesla/misc/

They are john01.jpg to john06.jpg.  I refer to them below.

At 10:15 PM 9/19/98, you wrote:
>
>  Terry -
>
>  I believe your results with the power factor tests of your coil are an
>excellent example of how the PF test can show how well your coil is
>performing. The higher the PF the better the coil is working. A perfect
>performance would be close to 100% PF. At this stage there would be very
>little reactive power returning to the source (electric utility co).
>
>  For example, with your coil you obtained the following:
>
>  .285 PF - gap not firing - large amount of reactive power returning to
>source.
>
>  .49 PF - gap firing - less reactive power returning to source.
>
>  ,675 PF - gap firing and output sparks - much less reactive power
>returning to source.
>
>  Estimated .80 plus PF ? - gap firing - controlled output sparks - very
>little reactive power returning to source.
>
>  You may want to try the estimated .80 PF test using horizontal continuous
>sparks from the toroid to a ground point that is connected to the secondary
>coil ground. This test might also take some adjustments of the operating
>gap and the tuning/coupling.

John01.jpg shows the input voltage and current with a horizontal arc to
ground as shown in john04.jpg.  The phase difference is 2.5mS which gives a
power factor of 0.588 .  

Consider this:  If my 15000kV/60mA transformer were to deliver all of it's
900 watts to the coil, each bang (at 120 BPS) would need to contain 7.5
joules (900/120).  So I would have to charge the primary cap up to 7.5
joules for every bang.  At 21213 volts peek, the capacitor would have to be
33.33nF.  Almost impossible to charge with a neon.  I can charge a 19nF max
to that level without resonant charging which would give 4.275 joules or
513 watts for a total efficiency of 513/900 or 0.57.  So by this method it
is almost as perfect as it can be.  However, this isn't quite true...
explained below.

>
>  I checked out your imp.003.jpg etc waveforms but had trouble interpreting
>them. However, they are excellent photos and were easily printed out. I
>would like to see the top waveform as the primary coil voltage and the
>bottom waveform as the secondary coil voltage. This should show the pri
>waveform as a dampened wave going to almost zero indicating all the energy
>is being transferred to the sec coil. 

John02.jpg and john03.jpg show this situation.  John02.jpg is to a 1 foot
arc and john03.jpg is to the grounded target.  The bottom trace in both
pictures is the output voltage of the secondary at 200kV/div.  the top
trace is 10kV/div in john02.jpg and 20kV/div in john03.jpg.  I worry that
the grounded target case may not be realistic.  The arc occurs before the
secondary is fully charged.  In fact the coil has not quenched before the
arc starts.  This is not very realistic of how most people run their coils.

>
>The sec waveform would show the rising waveform as the energy is
>transferred. At the peak the wave would collapse when the output spark
>occurs. There would then be little or no energy left to feed back to the
>primary and then to the source. 

John06.jpg shows this situation and why there is almost always some voltage
left.  Gaps quench when the current across them reaches zero.  Since
voltage and current are 90 degrees out of phase, the voltage is at a peak
when the quench occurs.  John06.jpg shows that almost 1/4 of the energy is
left in the primary due to this reason.  A substantial loss indeed!
Perhaps fine tuning could reduce this effect but this is definitely a
considerable source of energy loss and is responsible for the gap never
quenching just when we would like it to.  Much work to be done here!

>
>  I believe the PF test and the waveforms could tell you exactly how your
>coil is performing. You could then make changes and determine if they
>improved the performance. I have never heard of any coiler who has
>coordinated these tests.

It ain't easy!  John05.jpg shows the test setup just so no one thinks I
just make this stuff up ;-)

	Terry Fritz

>
>  Comments welcomed.
>
>  John Couture
>
>------------------------------------
>
>