Re: cap firing voltage scope measurements question

Hi John,

At 02:55 PM 6/16/99 -0400, you wrote:
> All,
> I'm seeing some strange results in my TC:
> Here are some cap voltage measurements under different conditions:
> I set my input variac at 60, and the scope indicated the output voltage
> of xfrmer was 15.2kVpeak, without the TC connected.
> At the same variac setting, but with TC connected, but with the 
> spark gap removed, the cap voltage reads 22.3kVpeak.  I suppose
> I'm getting some resonant charging here with this particular ballast
> setting.

Yes, the reactance of the primary cap is cancelling the reactance of the
ballast and allowing for resonant rise effects.

> At the same variac and ballast setting, but with the gap firing 
> (120bps), and the TC producing sparks, the cap voltage reads
> 30.4kV.  This means I'm obtaining a 2X voltage increase during 
> ~1/2 cycle, I thought this degree of resonant build up was possible
> only when using DC charging?

Such a high voltage rise seems strange to me but I could belive it in an
LTR setup with a sync gap.  Of course, the scope or probe may have bad
bandwidth characteristics or your getting noise which may be messing the
readings up.  However, I thought you were using pretty good HV probes and
such but that would be the first place I would look for a problem...  Do
you have safety gaps?  They should be firing like made at 30kV I would think...

> Does this seem normal?  I would have expected the voltage to be
> lower with the gap firing since there's less time for resonant voltage
> build-up.  In there a gap in my understanding?  Or is my scope
> reading wrong?  The 30.4kV makes sense from a Joule perspective,
> since it comes out to 840 cap watts or so, and the meter reads 1000
> watts, which seems about right. 
> Mystery, or insanity?
> Thanks,
> John Freau >>

Just a mystery at this point.  Much more work to be done before the
benefits of insanity start to simplify our investigations :-))

Very great work you are doing there!!