Re: 1-turn coil inductance nomogram

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

Original poster: "K. C. Herrick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <kchdlh-at-juno-dot-com>

Terry (& all)-

Rather than using a collapsible capacitance-changing structure as I had
suggested, you might consider a metal gazing ball.  Configure the toroid
so that its middle is open.  Then position a gazing ball inside that
opening so that it can be raised up and down.  Again, you won't have
sparks from the ball because its radius will be larger than the least
radius of the toroid.

Another way, as had been suggested on the List already, is to use a few
of the IGBTs, gating them so as either to function or not to.  That will
effectively change the C of the L-C primary circuit.  Yes, their
intrinsic diodes will conduct but I think, perhaps, only briefly until
the associated capacitors charge up.  If those diodes turn off too
slowly, you might supplant them with external, fast, ones.

Ken Herrick


On Mon, 26 Aug 2002 18:15:16 -0600 "Tesla list" <tesla-at-pupman-dot-com>
writes:
> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

[snipped]

> I have three 13.75 inch loops in parallel of 1/2 inch tubing.  The 
> chart
> gives 0.7uH for one.  Having three in parallel seems to have cut 
> that
> inductance almost in half!  I was starting to think have three loops 
> was
> silly but that is what got the frequency so high which is very nice. 
> I
> wonder if some simple way could be found to add tuning to such a 
> primary.
> Tuning these OLTCs is a bit tricky.  I imagine a lot of proximity 
> affects
> are significant too.