Coil Tuning

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

A post from elsewhere (4hv.org-Tesla Coils), but thought you all 
might enjoy too...
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I tend to use charts and graphs like this one for my SISG (could do 
DRSSTCs too). All that "computer stuff":

http://drsstc.com/~sisg/files/BigSISGCoil/Tuning.gif

The X axis is the primary inductance.  It shows that lower primary 
inductance really raises the primary peak current.  So if in doubt, 
go "up" not "down".  Interesting that higher coupling "lowers" the 
primary RMS current which is significant with the SISG.

Note how the higher coupling suddenly stops "helping" spark 
length.  The coil crosses over to needing higher BPS (coil power) at 
that point since the streamer starts starving for power.  So I need 
to push higher BPS there (with higher primary RMS current!!).  The 
bump in the arc length center trace at 19uH is probably an upper to 
lower pole transition.

Of course, all this does not take into account the coil being thrown 
into the trunk of the car and the toroid having to be duct(k) taped 
back together and all.  But if one sits there in the lab and 
carefully tunes everything (hours), the math matches reality very 
well.  But all this is usually meant as a "design guide".  Once put 
together, just tune for the biggest sparks :-)

These days, I tend to use the scopes, current transformers, antennas, 
etc. to tune the "programs" not the "coils"!  The programs are so 
good anymore, I often don't bother to measure since it is just a 
waist  of time.  The programs in many cases predict better than I can 
actually measure anything anyway...

BTW - By plotting "points" instead of "lines", the retrace graphing 
problem goes away ;-)

Cheers,

	Terry