Re: Primary Heating - inner turns

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

Original poster: "sundog by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>



Hi All,
         Just idle speculation,  so I invite the experts to correct me, but 
would the coupling of the coil have anything to do with the heating?  I'm 
pretty sure the magnetic field of the secondary transferring the energy 
back to the tank circuit would be much differently shaped than the magnetic 
field of the primary when the gap fires.  I could see the innermost turns 
heating up more than the outermost turns simply because they would bear the 
brunt of the energy transfer back into the primary.  On my VTTC the whole 
primary heats up immensely from the RF current (2kw at 830khz), and the 
base of the secondary heats up pretty good also (heavy base current), but I 
don't think there's that much energy transferred back into the tank 
circuit, mostly because of running a breakout point.  Here's a good way to 
test my theory.

  Run a disruptive coil with a too-large topload and breakout for a set 
number of minutes on-off time.  Check and record primary heating with an IR 
thermometer in the inner, outer, and middle turns.  Now, remove the 
breakout so the coil is unable to break out on it's own, and repeat the 
tests.  You should see extra heating in the primary, I would guess across 
the innermost turns more than the outer turns, though heat conduction would 
let the temp rise spread pretty well.
         Does that make sense to anybody but me?  That would ensure you're 
dissapating the entire energy of the secondary in the sparkgap.  I'd 
recommend a low powered system (12/30 or thereabouts) with a *GOOD* MMC 
capable of handling lots of current (GG caps).    I would think that the 
coil being unable to break out would limit energy escaping from the 
circuit, so the gap would get pounded pretty bad.  I would suppose another 
possible angle would be to short the secondary to ground so it sucks all 
the energy out of the primary in a very short period of time, which should 
run the gap cooler and reduce primary heating (no energy being bounced back 
into the tank circuit).   Feasible, silly, or outright on the wrong track 
here?

         I wonder about this experiment because there is a *very* 
noticeable temp rise (from really hot to downright scorching) on my quad 
833's primary from running with a breakout vs running it without a breakout 
at 20-30% power (great for lighting up every flourescent in the 
garage!)  This is on a VTTC, but I would assume the some rules would apply 
to a disruptive coil.


Just me $.02 worth :)
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Shad (Sundog)
G-2 #1203
"Ever stop to think, and forget to start again?"
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