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RE: QUESTION FROM THE PAS


 > From: EDHARRIS-at-MPS.OHIO-STATE.EDU
 > Subject: Re: Question from the pas

 > Now you're talking about something I've been really interested 
 > in: Has anyone done a detailed analysis of the electric and    
 > magnetic fields around a tesla coil secondary?  -Ed

Well, the fields vary in size and shape with the design,
construction, and tune (tap point) of the coil system. No two
are alike.

These fields can be observed with the naked eye in an over-driven
test system. Use a small discharger, and really overcouple the
secondary to the primary. If the system is fired in the dark it
will be possible to actually see the field, and the coil inter-
action. The field will get so intense that it will ionize the air
between the primary and secondary and the corona will clearly map
the field size, shape, and intensity. Be careful, arcs may jump
between the coils if a little too much power is applied.

I was amazed when I first saw this effect using a long skinny
secondary coil (candlestick design from the 1970s) because even 
though the primary was a vertical helix with 5 turns, it only
coupled to the bottom third of the secondary windings. This was
clearly mapped out by the corona glow caused by the primary/
secondary field flux.

I have since found that primary/secondary field fluxes that
couple the entire secondary winding all the way to the very top
turn, but that do not couple the discharger, give the best
efficiency and performace. I advocate designs that achieve this.
This usually means the primary must be saucer or pancake shaped,
and the diameter of the primary should be as wide as the
secondary is tall (lots of primary turns, with the largest
inductance turns to the outside). This produces field flux lines
that bathe the secondary coil uniformly from top to bottom, and
drives the entire coil winding equally for the best performance.

Richard Quick

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12