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Re: TC Critical Coupling (was Overcoupling


Hi John,

	I feel that we can measure "efficiency" very well.  There is little power
that is lost to unknown reasons.  MicroSim models are accurate and can be
used to find just about any current, voltage, RMS level, etc. one would
want to find.  These tools can be used for all kinds of wonderful things
and can especially be used to design for secondary arcs to the primary
(faults), larger than normal primary caps, spark gap effects, etc.  

	Electrically, we know a lot.  However, when it comes to what gives the
biggest output arcs, all the models don't mean all that much.  They
certainly get one through the technical details of building the thing so it
runs without burning up.  However, there is no output chart or graph of any
present model that shows how far, what color, what behavior, etc. the
output arcs will have.

	One very interesting thing that shows really how messy output arcs are is
this:  If I measure to output waveforms on an oscilloscope,  I can judge,
from the ringing, what the losses in the system are.  If the losses rise,
the ringing is lessened.  Better yet, given a waveform, I can reproduce
them with models to find what the loss is.  However, if I look at the
losses when the system is running before breakout (no arcs) and when the
system is pushing nice three foot streamers, the losses are not that much
greater.  In other words, the streamers seem to add little loss to the
system.  In fact I can account for most of the electrical loss in the
system just in the spark gap and primary loss.  No doubt, there is current
going into the streamers and some power too, but just as capacitors draw
current without loss, I am suspecting that streamers are really not
dissipating very much power.  Certainly not the hundreds of watts I am
pushing into the system.  I am beginning to think that the terminal
geometry and fields around the terminal have a far greater effect on
streamers than simply how much power is going into them (such as the larger
vs smaller terminal).  Perhaps, we are seeing more dielectric breakdown in
the terminal's space capacitance rather than power into a resistor.  I
suspect that one would want to heat one's house with the spark gap.  If you
depended on streamers for heat, you may freeze...


Just some quick thoughts after a long weekend of experimenting, perhaps too
much ozone :-))

	Terry


At 03:34 AM 5/17/99 +0000, you wrote:
>
>  Malcolm, All -
>
>  The Tesla coil overall efficiency issue is a conundrum like the power vs
>energy discussions of a couple years ago on this List. The equation
>    efficiency = output/input   looks simple enough  but for a researcher
>this equation represents many difficulties when applying it to electrical
>devices especially the Tesla coil. 
>
>  In the past many coilers have used the capacitor energy equation
>    joules = .5 C V^2     to find the TC efficiency. But is this correct?
>The losses found in this way do not represent all of the losses in the Tesla
>coil system. Left out are the losses for the power transformer, DC power
>supply, wiring, etc. Also there is the problem of the unknown amount of
>charge left on the capacitors before they are recharged by the power supply.
>This affects the efficiency. Note that the output of a capacitor is reactive
>and must be used with caution. The scope waveforms can tell you a lot about
>what is happening inside the TC system but have limited use for determining
>the overall efficiency.
>
>  These problems can be eliminated and all of the losses can be easily
>included by using the proper tests. Tests using known loads are the answer.
>For example to find the efficiency of an electric motor a Prony brake, a
>known output load, is used. For a Tesla coil a controlled spark or
>incandescent lamp which are known output loads can be used. There are other
>possibilities.
>
>  The "output" in the above efficiency equation means useful output, or
>useful work, that is, work done outside the TC system which can be easily
>measured. This output can be of a type selected to give the necessary data
>for finding the efficiency. The controlled spark can give you an "input
>watts per foot of spark" and the incandescent lamp can give you an "input
>watts per output watts". Efficiency graphs can then be developed using this
>data. I show in my books a preliminary start for this type of test. I also
>show an efficiency graph based on the limited data presently available.
>However, much more work needs to be done. 
>
>  I will be interested in what advanced coilers like you, Marco, Terry, etc,
>will produce regarding this thread in the near future.
>
>  John Couture
>
>----------------------------------------
>
>At 10:13 PM 5/12/99 -0600, you wrote:
>>Original Poster: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz> 
>>
>>Hi John,
>>
>>> Original Poster: "John H. Couture" <COUTUREJH-at-worldnet.att-dot-net> 
>>> 
>>>   Malcolm -
>>> 
>>>   Thank you for the reply. To determine the amplitude of the TC energy
don't
>>> you need to measure the amplitude of two parameters plus the time period?
>>> 
>>>   Energy = Volts x Amps x dt
>>
>>Not at all. Knowing capacitance and instantaneous voltage, E pops 
>>straight out. 
>>
>>>   To determine the overall efficiency you need the input energy and the
>>> output energy.
>>> 
>>>   % Efficiency = 100 x Output energy/Input energy  
>>> 
>>>   If I understand your reply correctly you measured only one parameter and,
>>> therefore, did not have the coil energy.  
>>
>>See above. E = 0.5CV^2.  In order to determine the energy retained by 
>>the system between secondary maximums as a percentage of initial 
>>energy, you go thus:
>>
>---------------------------   big snip
>