Re: LTR cap BPS?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi black moon (even white, blue, and harvest moons),

JavaTC has two LTR values,  one for SRSGs and one for static gaps.  The
static gap LTR is around 1.6 * Cres for your transformer.  This value will
give you about 100-120 BPS if the gap breakdown is set to Vpk of the NST.
The BPS prediction in JAVATC for static gaps is based on computer
simulations that I did and probably should be considered a "loose"
approximation.  The basis for the 1.6*Cres was originally 120BPS and also
has the benefit of limiting resonant rise.  It also should be realized that
the firing of a static gap is somewhat chaotic due to transient responses in
the charging circuit due to the gap firings (easy to see with a simulation)
and any breakrates can be obtained by changing either the gap setting and/or
the Cp value.  It doesnt necessarily lock onto 120 BPS.  With a given design
and gap setting you often will get some half cycles that do not fire and
other half cycles that fire multiple times,  You can also get periods of
time where only the positive cycle (or negative) will fire.

Last time I checked, JavaTC predicted 100BPS for a Cp = 1.6*Cres with gap
setting as described above (ie, Vsg set to Vpk of the NST, ie
1.414*Vs_oc_rms).  If the gap setting is larger than this, a lower BPS will
result and a larger than Vpk of the NST rating could result due to resonate
charging and transient effects.  If the gap setting is smaller than this, a
higher BPS will result.

Cres (nf) = 10^9 / (2*pi*line_freq*XL)
XL ~= Vs_oc_rms/Is_sc_rms
pi  ~= 3.1459

Gerry R


> Original poster: "Black Moon" <black_moons@xxxxxxxxxxx>
>
> Well, my question comes from
> http://www.classictesla.com/java/javatc.html
> Seems like if I use its LTR suggestion, it states 60~ or so BPS at any
> decently wide gap setting for the NST.
> Is this just the program screwing up and stateing 1/2 the BPS? or is it
> really 60bps at those gap settings?
>
> >From: "Tesla list" <tesla@xxxxxxxxxx>
> >To: tesla@xxxxxxxxxx
> >Subject: Re: LTR cap BPS?
> >Date: Tue, 30 Nov 2004 07:59:33 -0700
> >
> >Original poster: "Bunny Killer" <bunikllr@xxxxxxxxxxxxx>
> >
> >Hey Jamie...
> >
> >when using an LTR cap and NST the spark gap is the item that sets the
> >majority of the break rate...
> >
> >the cap will fill to the highest voltage the NST can provide during the
> >time it takes to make a complete sine wave ( well it will be a tad less
> >due to resistances) if your spark gap ( lets say its a static gap) is set
> >to fire at some voltage due to its gap width, the so called break rate (
> >in theory ) should be 120 BPS ...  this is considering that the gap width
> >is set for maximum voltage of your NST ( which is pretty much impossible
> >to set without dedicated measuring equipment)   if you set the gap too
> >wide the voltage will and can build to better than 2 times its rated
> >voltage  ( and by the way    the voltage ratings you see on the NST are
> >RMS ratings...  this is sort of an average rating of the sine wave,  not
> >the peak ratings the transformer is capable of...   a good reason to get
> >your caps voltage value at 2 times the name plate rating)
> >
> >if the gap width is set smaller, allowing the spark to be created in the
> >gap before the sine wave peaks,  it is possible to have 240+ BPS...
> >what happens in this situation is that the voltage builds and then jumps
> >the gap ( lets say at 50% of max NST voltage) the resonate circuit will
> >keep the voltage up a bit allowing the NST to recharge the cap set
quickly
> >and POP another spark jumps the gap before the sine wave peaks...  this
> >can happen several times before the peak of the sine wave....  thus 200+
BPS
> >
> >so  in a nut shell    the BPS should be 120    and resonate action will
> >cause it to go higher...
> >
> >why 120?   a complete sine wave has both a "positive" voltage swing and a
> >"negative" voltage swing..   thus  2 swings per complete cycle  ( and
> >there are 60 complete cycles per second in general USA applications
> >since the cap is capable of being charged in both directions ( an AC cap)
> >it is quite capable of the 120 BPS rate
> >
> >hope this helped..
> >
> >Scot D
> >
> >
> >
> >Tesla list wrote:
> >
> >>Original poster: "Black Moon" <black_moons@xxxxxxxxxxx>
> >>
> >>Hi, I was wondering, when using a LTR cap an a NST, is your break rate
> >>spost to be around 60? is the resonant action what causes it not to be
120+?
> >>
> >>
> >
> >
> >
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