NST Resonant Charging?

• To: tesla-at-pupman-dot-com
• Subject: NST Resonant Charging?
• From: Greg Leyh <lod-at-pacbell-dot-net> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
• Date: Tue, 13 Oct 1998 21:36:45 -0600
• Approved: terryf-at-verinet-dot-com

Hi All,

I still don't understand how resonant charging could possibly
work in a practical NST-powered TC. 

Assume the cap is set to Xl of the NST's leakage inductance,
which gives 0.011uF for a 15kV 60mA NST (this seems to be the 
most popular method of choosing Cpri).  
Then the cap resonates with the NST at 60Hz, and the voltage 
will build with each cycle -- and if the gap is set to not fire, 
the voltage buildup will ultimately be limited by the Q (and the
breakdown strength) of the charging circuit.

But what if the gap fires at each peak, at 120BPS?
Then the energy is stolen from the cap every 8.3 mS, preventing
any significant resonant rise!  Remember, this charging circuit
resonates at 60Hz, and therefore requires a significant portion
of the 60Hz cycle to build past even the normal open ckt voltage!

The charging slope could of course be speeded up by using a smaller 
capacitor, but at the expense of ultimately limiting the available 
primary energy.  The other important point here is that the firing
rate *must* be 60BPS or a multiple thereof, in order to get any
decent performance out of a 60Hz-fed resonant charger.

What is really going on?  Does anyone have voltage waveforms 
of a NST resonant charge cycle in action?
-- 


-GL
www.lod-dot-org

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