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Re: NST Resonant Charging?

Hi Mark, Ed, and All,

	I have my 15kV / 60mA neon well modeled so I punched in what would happen
if I put an 11nF cap on the output and clicked the switch.  

Maximum output voltage 298kV at 1.24A !! :-))

It took awhile to ring up that high.  This shows that a capacitor on the
output can very effectively blow a neon out.  The secondary windings and a
cap can easily ring to very high voltages limited only by the relatively
low losses in this system.  Of course, one will never get close to this
theoretical voltage in a real system.  The model does not account for the
core saturation that would kick in long before the voltage got that high.
Also, corona and arcing would quickly add losses as the voltage flies up.
And then there is the BANG factor as the neon and caps blow up :-)
	Safety and regular gaps basically add a giant loss to the system before
these destructive voltages can ring up and limit any damage.  Static gaps
will arc over and limit the voltage (and current) to safe values.  A rotary
gap without a safety gap will destroy the transformer or cap instantly
since its rotation will allow times were the gap can't fire when it should.
 If the speed of rotation is fast it may be able to catch itself but the
risk would be dramatically high.
	There is another risk modeling shows, if the neon is suddenly switched on,
there is a large initial current and voltage surge.  This is not a factor
at 11nF but at other capacitor values, it can cause a substantial voltage
spike on the neon's output which could easily cause damage.  It is very
desirable to turn up a variac slowly instead of just flipping an on switch.
 Safety gaps should protect against this too, however.

	Terry


At 07:16 PM 10/15/98 -0700, you wrote:
>"Hello All:
>        With AC resonant charging, the maximum attainable voltage is pi
>times the peak AC voltage.  This can occur after 1.75 cycles of the AC. 
>If
>your spark gap is set to fire every 1/2 cycle and misses a couple
>firings,
>the voltage can rise to extraordinary values: 10 kV x 1.414 x 3.14 =
>44.4 kV
>peak!  (So long, NST!)
>Regards,
>Mark S. Rzeszotarski, Ph.D."
>
>Mark:
>
>	Please explain that remark.  Around here the maximum attainable
>voltage, assuming no breakdown in either the gap, transformer, or
>capacitor is the transformer Q at sixty cycles times the open-circuit
>voltage, and I've satisfied myself to that by operating a transformer at
>low voltage.  The Q is certainly greater than pi.
>
>Ed
>
>
References: