Re: Calorimeter

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

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

Gary,

You're presenting an interesting piece of work here - for two reasons.
One - as you comment, we don't have an effective model of resonator
losses, and two - you're able to put enough power into the coil to
measure losses under breakout conditions.

A few comments and questions...

What is the coil former material?
What is the ground plane material?
How are you measuring the input resistance? Does the generator
deliver a sinusoidal voltage, or are you having to allow for its
harmonic content when calculating V/I?

The observation of variation of loss with humidity is very
interesting. I'd like to know whether this loss is attributable to
a) extra loss factor of the surrounding air due to water vapour
content.
b) shunt conductance loss due to condensation or absorption of
moisture onto the coil surface.
c) ditto, styrofoam surface.
d) ditto, coil former material - sonotube syndrome?

Perhaps you could hermetically seal the coil/topload inside a 
poly bag and see if the loss still varies as you vary the humidity
1) outside the bag? 2) inside the bag?

Does the variation of loss with humidity occur at both small signal
levels, and at breakout power levels? Are we seeing encouragement
of breakout by the humidity - in which case the phenomena ought to go
away with small signals?

> The 22 gauge coil has a lower input impedance and puts more power
> into the spark (faster temperature rise) for a given input power.
> John Freau is right when he suggests using smaller gauge wire!

I believe that John's argument is that a higher L/C ratio reduces the
effect of primary gap loss by increasing the characteristic impedance
of the primary circuit, so I don't see how your CW measurements apply to
this. A better explanation might be that the 22 gauge has a lower
loss due to reduced proximity effect arising from its wider spacing
ratio. But, in view of possibility (b) above, the extra insulation
thickness of the 22 gauge may have other benefits.

Have you tried measuring the coil temperature rise while passing DC
through the winding? Then the comparitive rise during AC operation can
be determined and the ratio between AC and DC resistance estimated.
Alternatively, measure the DC power necessary to give the same
temperature rise over a fixed time interval. Is the AC resistance thus
estimated commensurate with the overall AC loss as determined by input
resistance or Q factor, or is there a significant residual? 

As power is increased, does the input resistance start to rise before
corona is observed? Can you graph input resistance against input
power, for both high and low humidity?  If so, does the humidity alter
the power level at which the input resistance starts to rise, or does
it just alter the steepness of the rise?

I'll look forward to seeing further results.
 
Cheers,
--
Paul Nicholson,
Manchester, UK.
Secondary modeling project: http://www.abelian.demon.co.uk/tssp/
--