Re: VTTC output

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Herwig Roscher by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de>
> 
> Ed Phillips wrote:
> 
> > You didn't mention plate current
> 
> Ed,
> 
> - At full power it was 350 mA -at- Vp = 9000 Vdc and Vg2 = 1000 V.
> The plate remained at a middle red color.
> 
> > what was the net power input?
> - I'm using a 3 phase tranni and haven't got a 3 phase wattmeter.
> So I don't know the net input power.

	Looks as if it's 3150 watts.
> 
> > what is the operating frequency
> - It's around 200 kHz
> 
> > are you sure primary and secondary tune to the same
> frequency?
> - Yes I am. First I had some problems to understand frequency
> splitting, but with the assistance of Bert Hickman I found the
> correct tuning procedure.
> 
> > Have you played with the coupling?
> - I've changed the distance between the lowermost turn of the
> primary and the lowermost turn of the secondary from +45 mm
> (secondary above primary) to -15 mm (secondary below primary).
> Neither the voltage across the 5.1 Ohm resistor, which I've
> connected between the base of the secondary and rf ground, nor
> the visible shape of the brush changed. Below +30 mm the
> waveshape, which was nearly pure sinusodial before, started to
> become more and more distorted. Do you have an explanation for
> this?

	At least two possibilities and probably more.

1. The tuning changes with coupling, the output voltage and streamer
loading vary, and the plate tank circuit tuning changes.  At the same
time the circuit Q's get lower, making it easier for the circuit to
support harmonic voltages.

2. Much less likely is that you are observing the effect of the
non-linear streamer current.  On second thought, since you are measuring
the CURRENT flowing into/ out of the secondary, maybe the non-linear
impedance makes more of a difference than I think.  Several years ago
someone attempted to characterize these nonlinear effects, and put some
of the dope on this site.  I've lost it, but maybe Terry has it*.

	Finally, sounds to me as if you're doing pretty well!

Ed

	By the way, there is a possible way to measure efficiency (at least of
tube output power to the tank divided by input DC power).  It has long
been used in connection with adjustment of high power air-cooled tube
amplifiers where the plates run with color.  

1. Measure the plate temperature with an optical pyrometer under normal
conditions.

2. Apply DC current to the tube and measure the DC power input at the
point where the plate color is the same as that when the amplifier is
operating.

3. The net power output is the difference between the plate dissipation
determined above and the DC input power.

	Efficiency then is power output / power input.
---------------
* maybe...
http://hot-streamer-dot-com/TeslaCoils/MyCoils/CWCoil/CWImpedance.txt
http://hot-streamer-dot-com/TeslaCoils/Misc/impedance/impedance.html
-Terry