Re: NST/cap sizes - was RE: Coil Woes

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 



No --- this is not correct.  No matter how much available potential your
xmfr has, the firing potential is determined by the sparkgap setting not the
xmfrs peak potential.  Ask Terry to post my sparkgap chart and you will see
it's usually around 16-18 kV for typical NST settings (200-260 mils).

http://hot-streamer-dot-com/TeslaCoils/Misc/SGapVolt.jpg

We usually apply a HV power supply and see where the gap starts firing ---
using our 50 kV DC probe to monitor and rectified HV from the NST.  Use this
value and not the calculated peak value of the NST.


Dr. Resonance


 >
 > C V-Bang 120*.5*C*Vbang*Vbang
 > .02uF 24.4kV 714W
 > .03uF 21.9kV 863W
 > .04uF 19.6kV 922W
 > .05uF 17.1kV 877W
 >
 > Note that with LTR caps, Vbang is considerably less than the peak cap
 > charging voltage.  For the .04uf cap, the peak voltage was about 22.2kV.
 >
 > I'm not sure that our NST simulation models accurately predict what
 > happens when the mains voltage is raised above nominal and the magnetics
 > become non-linear.
 >
 > Regards, Gary Lau
 > MA, USA
 >
 >
 >
 > Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>
 >
 > Hi John,
 >
 > That could very well be.  Unless I'm misinterperating the post, Gary's
 > 4.0*Cres was the results of an experiment with a dummy load.  I'm just
 > trying to get closure on results in a running SRSG system and if the 4.0
 > Cres continued to hold up.  I'm most interested in the bang voltage of
 > the
 > 15/60 system with 4.0 Cres.
 >
 > Gerry R
 >
 >
 >   > Original poster: FutureT-at-aol-dot-com
 >   >
 >   > In a message dated 10/12/04 11:59:27 AM Eastern Daylight Time,
 >   > tesla-at-pupman-dot-com writes:
 >   >
 >   > >Hi Gary,
 >   > >
 >   > >I remember your post.  Since Cres for your 15/60 NST is 10.6 nf
 > (call it
 >   > >0.01uf), your experiment would correspond to ~ 1 to 5 * Cres.  Im
 > wondering
 >   > >if the dummy load is affecting the results.  My computer simulations
 > show
 > at
 >   > >values above 3*Cres, the inductive kick can not get things fully
 > charged.
 >   > >My actual measurements were between 1.6 and 2.5 * Cres where I
 > scoped the
 >   > >primary durning actual SRSG operation.  At 2.5 * Cres, I was drawing
 > 1080
 >   > >watts from the power cord and charging to 24KV at the time of bang
 > (900
 >   > >watts thru the gap).  I haven't gone larger than 2.5 * Cres cause I
 > ran
 > out
 >   > >of cap.  So far the measured results agree with the simulation so Im
 >   > >wondering if 4 * Cres would hold up during real operation.
 >   > >
 >   > >Gerry R.
 >   >
 >   >
 >   > Gerry,
 >   >
 >   > It think possibly the secret is that Gary's NST is robust
 >   > and may deliver more current than expected.  This may be
 >   > partly due to the use of 140volts input voltage.   It seems
 >   > that all NST's are not the same regarding their current
 >   > capability.
 >   >
 >   > Cheers,
 >   > John
 >   >
 >   >
 >
 >
 >