Re: Tesla Coil Efficiency Test

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Paul,
          We figured out how to do this a number of years ago:

On 18 Jun 2002, at 7:37, Tesla list wrote:

> Original poster: "Paul Nicholson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>
> 
> Hi All,
> 
> Seems to me that trying to define and measure efficiency for a
> disruptive TC by the methods discussed so far in this thread
> is problematic.
> 
> Why not take a different approach...
> 
> Measure the overall Q factor of the dual-resonator ringdown,
> with the gap closed by a lossless switch (eg a switch!) at
> low voltage...Q1
> 
> Then measure the overall Q factor at a power level just below
> breakout, using the primary arc gap instead of a switch...Q2
> 
> And finally, measure Q again, this time with breakout...Q3
> 
> Since in each case the fraction of energy lost from the resonator
> per cycle is proportional to 1/Q, it should be possible to say
> something definate about the quality of the primary gap by
> comparing Q1 with Q2, and the ability of the resonator to dump
> its stored energy into the streamer load could be indicated by
> comparing Q3 with Q2.
> 
> For example, if Q2 is half that of Q1, then we can say that the
> primary gap is dissipating the same energy per cycle as the rest
> of the resonator.
> 
> Using Q3 and Q1 we can define a measurable standard of overall
> efficiency in a consistent manner (ie it is meaningful to compare
> different coils), eg by  
> 
>  Efficiency = 100 * (Q1 - Q3)/Q1  ...percent
> 
> Of course, this only defines the efficiency of the RF portions of
> the system.
> --
> Paul Nicholson
> Manchester, UK
> --

The method was so simple that it was a wonder it never received a 
mention in works of the time, Corums included. Ensure that Ep is such 
that secondary breakout cannot occur. Capture two successive beats on 
the scope (an aerial probe is all that is needed since a percentage 
rather than an absolute figure is all we are after). Measure the 
amplitude difference between the first two secondary maximums. The 
energy difference is proportional to V^2. This difference as a 
proportion of the first secondary maximum gives the proportion of 
energy lost over 2 transfers. Halving the loss figure gives an 
*indicative* figure for a single transfer. The loss over the first 
transfer will be higher than the second since the gap currents are 
higher. Secondary Q under these conditions is so high that the figure 
gives a fairly good indication of how badly the primary gap is doing 
if the quality of the primary is also several tens. Indeed, you will 
see a linear envelope imposed on the beat envelope over a number of 
trades showing exactly where the loss is occurring.

    As for the energy transferred to the sparks, waveform capture 
shows that for air streamers, several trades occur indicating that 
overall Qsys remains relatively high. This is the condition that 
Terry is measuring. More trades back to the primary = additional gap 
losses.
    For connected sparks however, the beat pattern is abruptly 
interrupted during a secondary maximum showing a sudden loss of 
energy to the secondary. The loss can be very rapid - just a cycle of 
oscillation more-or-less.

Regards,
malcolm