# Re: Re........ Measuring Coupling Coefficients (fwd)

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---------- Forwarded message ----------
Date: Mon, 15 Dec 1997 07:46:48 +0000
From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Re........  Measuring Coupling Coefficients

At 03:33 PM 12/11/97 +0000, you wrote:
>
>From: 	Barton B. Anderson[SMTP:mopar-at-mn.uswest-dot-net]
>Sent: 	Wednesday, December 10, 1997 8:12 PM
>To: 	Tesla List
>Subject: 	Re........  Measuring Coupling Coefficients
>
>Tesla List wrote:
>

>Here's a mood point: In an RF Coil, Q = 2 PI F L / re :::: where "re" is the ac
>effective resistance, not the dc resistance measured with a 9v battery
powered meter.
>At low frequencies, the coils resistance should be ok to use in a
calculation, but in
>an RF Coil, as frequency increases the effective resistance(re) increases
because "re"
>is a "resistive" component drawing in-phase current from the ac source, and
if "re"
>increases then Q decreases. By how much would be dependent on the I^2R
losses at the
>operational frequency and that might be a bit hard to calculate if not
impossible. It
>will be interesting to see how Marks program performs this function.
>
>Bart

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Bart -

You are one of the few coilers that recognizes the unique character of the
effective resistance Re in the equation   Q = Xl/Re .   Most coilers are
satisfied to call this resistance the AC resistance which it is not. Of
course, EE and Radio Handbooks do not recognize this TC resistance because
they do not discuss Tesla coils so information on this parameter is hard to
find .

The Tesla Coil Design Manual shows different graphs to find the the Re
resistance for Q factors and the AC resistance of a wire. The AC resistance
graph is from Knowlton's EE Handbook and is a standard for electrical
engineers. The graph for the effective resistance Re is one that I developed
for the JHCTES program. I think this graph is the only one of its kind so it
has not been verified but seems to work for the program. However, this type
of graph will have to be made by anyone who is going to make a TC computer
progran similar to the JHCTES program.

It should be noted that the only way to find the primary Q factor and
other parameters of an operating TC at high voltage is as shown in the Tesla
Coil Notebook. Knowing the Q factor it is then possible to find the Re of
the secondary coil circuit.

The understanding of classical Tesla coils by coilers still has a long way
to go.

John Couture

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