# Re: How should we measure coil efficiency, was neon vs. potenti

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From: 	John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: 	Sunday, July 27, 1997 11:47 PM
To: 	Tesla List
Subject: 	Re: How should we measure coil efficiency, was neon vs.    potenti

At 07:49 PM 7/26/97 +0000, you wrote:
>
>From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
>Sent: 	Saturday, July 26, 1997 4:29 AM
>To: 	tesla-at-pupman-dot-com
>Subject: 	Re: How should we measure coil efficiency, was neon vs.   potenti
>
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John F. et al. -

Some time ago somone on the T. List asked how to determine the best tank
circuit for a certain power transformer. This means that a certain operating
frequency must be selected.

Tesla in the CSNotes mentioned that increasing the frequency would produce
more output because a higher frequency contains more energy. A wave with
more cycles contains more energy. However, Tesla also said that losses
increase faster than the gain in energy. This means that for every coil
there is an optimun frequency and tank circuit. This optimum frequency
should give the maximum spark length.

I have never heard of anyone including Tesla who has tried to find this
magic tank circuit. It should be possible to find an approximation using a
computer program and Fr, Lp, Cp, Ls, Cs, Vs, coil self capacity, and a few
other parameters. The independent variable would be Fr and there are plenty
of dependent variables. Anyone interested?

For a low frequncy, low gain coil the output energy will increase with a
gain in frequency. However, a point is reached where the gain is not enough
to overcome the losses and the optimum frequency and tank circuit is reached.

It should be noted that a large part of the losses in the TC secondary
circuit are due to the coil self capacitance. This capacitance is a loss
because it shorts out (loads) the sec voltage. The sec coil self capacitance
of a small TC is less than a large coil so this type of loss is less with
the small coil which is operating at higher frequencies.

John Couture

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>>   Where did you find that higher frequency gives shorter sparks?  I believe
>> it is the other way around.  The higher the frequency the longer the spark.
>
>>    Energy = hf    h = Planck's constant   f = freq.
>
>>    From the above equation the energy increases as the frequency increases,
>> other factors being equal. This would mean when the frequency increases the
>> spark length increases.
>
>John C,
>
>The above equation completely ignores radiation losses, and  plasma ion
>growth effects.  As you said, "other factors being equal", but in a TC other
>factors are not equal.  High frequency sparks tend to take on a short
>plasma flame-like appearance.
>
>John Freau
>
>>    But frequency is a minor factor. The major cause of air ionization is
>the
>> voltage and the higher voltages give longer sparks.
>
>>    As I have said in past posts, the quality and appearance of sparks is
>> subjective for Tesla coil ratings, so these ratings must be viewed from
>this
>> standpoint. Also, sparks cannot be converted to energy so they cannot be
>> used for findung the efficiency of a Tesla coil.
>
>     John Couture
>  >>
>
>
>
>

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