Re: FW: Re: Tesla Coil Efficiency Test

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

Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

John Couture wrote:

> Keep in mind that the lamp test is not dependent on the
> charateristics of the lamp.

It's appreciated that the single level comparison avoids
calibration or linearity issues.

However, the problem with the lamp test is that the number it
produces refers to the efficiency of energy transfer to that
particular lamp with that particular degree of coupling to the
secondary coil.

If you run the test with the lamp fairly loosely coupled to
the coil, you'll get a smaller value for the apparent efficiency
than you would if the lamp was coupled more tightly.

For the lamp test to be a viable method for assessing the 
efficiency of the coil when operating into a streamer loading,
then somehow you will have to adjust the coupling of the lamp
so that it dissipates the same fraction of stored energy per
cycle (on average) as does the streamer load during operation.

> Malcolm's transfer method for finding the TC efficiency does
> have merit.  However, it must be understood that this represents
> only the efficiency of a part of the TC system and some losses
> sre left out.

Yes, I agree. We only get the efficiency of the RF parts of the
system by using methods based on ringdown.  Losses in supply
transformers, ballasts, PFC, etc are invisible.  The lamp test
does give an overall efficiency, rather than just an RF efficiency.

I don't see any fundamental problem with defining a measurable
'efficiency' of a TC, providing you are clear on what you consider
the 'output' to be.  For example, if you choose the streamers to
be the output (as opposed to spark discharges to ground, or energy
coupled to a receiver coil), then by measuring the ringdown times
at just above and just below breakout, and treating these as loaded
and unloaded Q factors respectively, the RF efficiency can be
calculated in the normal way just as you would for any other tank
circuit.  As another example, if you were wanting to transfer
power to a wireless load, for example an inductively coupled lamp,
then you would measure the ringdown times with and without the
lamp circuit closed to obtain the RF efficiency of coupling to the
lamp.   Similarly for other loads which give a meaningful
average decay rate to the stored energy.  Spark discharges to
earth don't meet this qualification and a modification to the
ringdown test is required for this, but the RF efficiency is still
obtainable.

> The decay rate of the secondary base current sounds interesting.
> How would you do the metering to find the energies?

The RF efficiency obtained by ringdown tests must be qualified by
an input power measurement, the BPS, and either a firing voltage or
a peak primary current measurement in order to obtain the energies
and an overall efficiency figure

All in all, the lamp test would be a much simpler and more
accessible method, if some way could be found to ensure that the
lamp loaded the resonator down to the same Q (and same Fres for
that matter) as the operational streamer load (or some other
definition of output) does.
--
Paul Nicholson
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