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Coil Tuning

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>


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


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 ;-)