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0.5*C*V*V vaild? (Was Output Voltages and Voltage/Leng
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From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Sunday, February 15, 1998 7:09 PM
To: Tesla List
Subject: Re: 0.5*C*V*V vaild? (Was Output Voltages and Voltage/Leng
HI John,
> Date: Fri, 13 Feb 1998 20:29:09 +0000
> From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: 0.5*C*V*V vaild? (Was Output Voltages and Voltage/Leng
>
>
> All -
>
> As D C Cox mentions the Q factor of a Tesla coil can be found by using the
> method I show in the Tesla Coil Notebook. I have never seen this test method
> for Q factor published before. This method requires an oscilloscope and is
> based on the equation
>
> Q = 3.1416/log dec
>
> The log dec can be found from the equation
>
> log dec = ln(a1/a3)
>
> The a1 and a3 can be found from the waveform shown by the scope and as
> shown in the Notebook. This test appears to be the only way to find the Q
> factor of a Tesla coil while operating at high voltage.
>
> John Couture
It is useful *as long as no corona is issued* because Q is a function
of loading. One also hopes that the ground is perfect or that figures
in the result as well. The real difficulty with that test though is
with quenching the gap while the secondary is at max amplitude on
completion of the first ringup. If you can't do that you are little
better than measuring system Q according to the overall beat
envelope decrement because the primary is the dominant loser in most
if not all systems that are prevented from issuing a secondary
discharge (check out the increased brightness of the gap if you
don't believe me). You can tell where the worst losses are under those
conditions because they will determine the beat envelope shape. If
the envelope is a linear one, the primary is governing its shape.
If it is logarithmic, you can do a lot better in the secondary
department. If a secondary discharge issues forth, it (and the
spark gap if not quenched) are losing power so what can you deduce
about the quality of the secondary itself under those conditions? I
suggest that this method is highly problematical.
Perhaps it is time to ask once again: hands up everybody whose
gap can effect a first notch quench under no breakout secondary
conditions? If anybody's gap system can do this I would *love* to hear
about it as it would be an answer to a lot of operational problems.
Malcolm