Re: Solid State TC Secondary Coil question

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

Original poster: "Justin Hays by way of Terry Fritz <twftesla-at-qwest-dot-net>" <pyrotrons2000-at-yahoo-dot-com>

Hi Dan,

> If i used the same driver circuit, but built a secondary 3" dia 
> coil and secondary 4" dia coil, both secondaries designed (with 
> toroid) to have same resonant frequency.  How would performance 
> differ between the two????

Provided that the coupling coefficient of the two coils remain the
same, your sparks won't change much. If anything, your sparks will be
longer because of the added capacitance associated with bigger coils.
I find that it's somewhat like using a bigger topload.

Here are my results with two completely different tesla coils, with
exact same driver and H-bridge:

--------------------
Tesla Transformer #1: 

Secondary: 4.5" O.D., 16.5" long, wound with #28 on PVC pipe.

Primary: 20 turns of #12 THHN, helically wound over the bottom 1/4 of
the resonator, with 1.25" spacing between the two coils.

Topload: Al foil covered 4" lightbulb.

Acs: measured 7.5" arcs when tuned.

--------------------
Tesla Transformer #2:

Secondary: 1.9" O.D., 10" long, wound with #37 wire, on PVC pipe.

Primary: 20 turns of #18 hookup wire, wound over the bottom 1/5 of
the secondary, form was 3" O.D. plastic

Topload: Al foil covered 4" lightbulb.

Arcs: measured 10" when tuned.

--------------------

So the arcs were 3" longer with a coil that was many times smaller.

This is probably due to the different coupling coefficients of the
separate systems. The smaller coil did better probably because the
coupling was closer. Yes, it did pull more current from the mains,
but that's not the concern here.

Want bigger sparks? Fool with the coupling!

The only reason I would use a bigger coil, is if I was destroying
smaller ones from overheating and/or turn-to-turn flashover. Bigger
coils can handle more power.

Take care,

Justin Hays
KC5PNP
Email: justin-at-hvguy-dot-com
Website: www.hvguy-dot-com