RE: NST Resonant Charging?

To: tesla-at-pupman-dot-com
Subject: RE: NST Resonant Charging?
From: Sulaiman Abdullah <sulaiman-at-lityan-dot-com.my> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Wed, 14 Oct 1998 11:28:45 -0600
Approved: terryf-at-verinet-dot-com
> Greg, first a disclaimer - I've 'blown' my NST so I can't give actual
> measurements, but;
> 
> Using simulation software you can prove to yourself that even though
> the capacitor is discharged every 1/2 cycle of the mains the highest
> voltage IS produced for the 'resonant charging' scheme, and very
> nearly at the zero-crossing of the mains input. By SIMULATION only at
> the moment a higher power/energy (fixed pps) is achieved with about
> 20% higher capacitance.
> 
> If anyone wants it I can e-mail PC-ECAP a shareware simple simulation
> software package and the relevant data file for resonant charging.
> Please e-mail me off-list (sulaiman-at-lityan-dot-com.my)
> 
> With just an NST and capacitor simple theory gives an ultimate voltage
> accross the capacitor of Q times NST voltage (and Q times rated
> current!), and if you use a variac at low voltages this is true, but
> ultimately the NST core saturates so in (theoretical) practice you
> will probably see a multiplication of two only. BTW this kind of
> experimenting is what caused the demise of my NST!
> 
> Anyone else got some info. here?
> 
> bye ... Sulaiman
	_____________________________________________________________
> Original Poster: Greg Leyh <lod-at-pacbell-dot-net> 
> 
> 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
> 
>