Re: TC Primary Capacitors.

[Terry Fritz <twftesla-at-uswest-dot-net>]

Just a note...

My small LTR 9kV/0.030 NST coil fires at 120BPS, 11000V, 27nF.
My large LTR 15kV/0.060 coil is 120BPS, 21000V, 24nF.
That is 196 and 635 watts into (and out of) the primary cap.  This
represents about a 71% efficiencies as compared to the NST's nameplate "VA"
rating.  No magic at all there...

Of course, you have to be sure of all the RMS current levels in these cases
which is not easy :-)  A 34nF cap on a 15/60 may have been working a bit
into the "going nuclear" saturation region (SLTR) where the current ratings
of the NST have no meaning.  Only the "fuse" rating is important there :-))

Cheers,

	Terry


At 04:45 PM 7/28/00 -0700, you wrote:
>
>To All -
>
>Back in April Mike H. said he had heard that the TC primary capacitor could
>be as large as four times the resonant cap size. I am finally getting around
>to commenting on this possibility. This is for a NST 15KV/60ma - 60 Hz -
>21000 volts (Vp) - 7.5 watt secs per break output. The efficiency refers to
>the amount of energy transferred from the NST output to the primary
>capacitor. The equation is
>
>   Watt secs * eff = .5 Cp Vp^2
>
>Listed below are some of the many possibilities.
>
>   Type cap       Cp uf         Eff. %
>
>  Max size         .034         100 %
>
>  Ver 3.1          .020          59 %
>
>  Resonant         .0106         31 %
>
>The max cap size is .034/.0106 = 3.2 times the resonant cap. However, this
>cap could not be charged to the peak 21000 volts because the efficiency
>would be less than 100% in the real world. What voltage would this cap be
>charged to at 59% efficiency?
>
>The Ver 3.1 (JHCTES) cap appears to be a good choice because the efficiency
>is reasonable and it is not a "sweet spot" capacitor. Most coilers use caps
>about this size for this size NST.
>
>Resonant Cap. It is interesting to note that if the current or wattage did
>not change because of the resonant condition this would not be a good
>choice. This cap (non resonant) would use only 31% of the possible charging
>capacity. This cap does not produce longer sparks because of the size of the
>cap but rather because the NST input current is increased. However, it is
>not a good choice if you value your NST.
>
>How do YOU determine the size of the primary capacitor for this NST?
>
>John Couture
>
>---------------------------
>