[TCML] DRSSTC tuning - primary current modes

[David Kronstein <david_kronstein@xxxxxxxxx>]

Hi All,

I was working on tuning my DRSSTC (coil details at 
http://4hv.org/e107_plugins/forum/forum_viewtopic.php?63284), and I 
notice that the primary current goes very suddenly into a "notch" mode 
when moving the tap point. I've taken a series of scope shots of this 
and made a couple of animated GIFs.

Condtions: 100VDC bus, single shot, some breakout into air,  ~1' sparks. 
200A/div current, interrupter output shown on scope.

This one shows a relatively wide range of primay turns, ranging from 3 
11/12 to 4 9/12 turns, 1/12 turn per step:
http://4hv.org/e107_files/public/1235287411_347_FT63284_wide_range.gif

There's a very sudden change early on. I tried to take more steps, shown 
in the shot below, but the transition point is somewhere in the middle 
of the primary support, so I can't take extra shots in between. 4 2/36 
to 4 7/36 turns in 1/36 turn steps.

http://4hv.org/e107_files/public/1235287411_347_FT63284_narrow_range.gif

Why do these sudden changes occur with changing tap point? And what 
would you generally recommend for setting the best tap point? I've heard 
people say to tune the primary about 10% lower than the secondary.

Thanks,
David
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