RE: Q Factor and Overall Efficiency

["John H. Couture" <couturejh-at-worldnet.att-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Terry -

I tried this type of test several years ago. It doesn't work because
connecting anything to the secondary reduces the voltage an unknown amount
and may cause sparkovers. Apparently you haven't tried the test I mentioned
using a probe with no connection to the secondary. I don't have the
instrumentation to do the probe test.

As I recall you have made tests to determine the secondary voltage (Vs) of
one of your coils. How did the test Vs compare with calcs using the energy
equation and the sqrt(Cp/Cs) and sqrt(Ls/Lp) equations? The overall
efficiency would then be
     Eff = test Vs/energy Vs

The operating Q factor would be
      Q = test Vs/Vp
Vp = Peak primary voltage

If we could get about two dozen knowledgeable coilers to do these tests with
their coils we could then pin down the TC secondary voltage and operating Q
factor once and for all.

John Couture

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


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, August 27, 2000 11:55 PM
To: tesla-at-pupman-dot-com
Subject: Re: Q Factor and Overall Efficiency


Original poster: Terry Fritz <twftesla-at-uswest-dot-net>

Hi John,

	Assuming an arc is 220K ohms plus 1 pF per foot of streamer.  One can make
a little resistor and capaictor to simulate this streamer load.  Simply
connecting a secondary to ground through this load allows one to measure a
secondary systems Q as it is with a load with a signal generator and scope
looking for the center frequency divided by bandwidth method.  Nothing too
dramatic will be found but sort of fun to do...

Cheers,

	Terry


At 05:46 PM 8/27/00 -0700, you wrote:
>
>The Q factor tests have been discussed many times in past List posts.
>However, these tests give the Q factor in a low voltage condition. This is
>not the TC operating Q factor. The operating Q factor would give the
>secondary voltage with the equation
>    Vs = Vp * Q
>where Vp is the primary peak voltage.
>
>To find the operating Q factor would require only a scope and the proper
>probe and the knowhow. To do the test find the half power points while the
>Tesla coil is operating. Then determine the Q factor with the equation
>    Q = Fr/(Fh - Fl)
>where Fr is the resonant frequency, Fh is the higher half power frequency,
>and Fl is the lower half power frequency. The Q factor would be the voltage
>gain from the TC input to the TC output. This gain could then be used to
>find the overall efficiency of the TC system. This would be done using the
>energy equation
>     Vs = sqrt(2J/Cs)
>Overall efficiency would be the Vs(half power) test volts divided by the
>Vs(energy) theory volts.
>
>This operating Q factor and TC overall efficiency may be a first in the
>design and engineering of Tesla coils. However, Terry Fritz may have
already
>done this? Have other coilers done this?
>
>John Couture
>