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RE: NST Charging Circuit Study
Hi John,
Neat! Looks like we are thinking alike and the data I am taking is
suffiecent to do these calculations.
I think I have the models pretty well iron out now and the "process"
automated a bit to make it go faster. I have Excel set up to do the
calculations now. I also have it set up so I can repeat the tests on real
equipment to be sure the numbers are real.
The BPS is good to know for various cap sizes. The firing rate goes from
stable to unstable in many cases and there are sort of "good and bad" cap
values. Back calculating the BPS works well but I am taking the "actual"
BPS too. The secondary currrent is good to know for power dissipation and
the stress on the NST.
Whew! It's a lot of work but the results so far are fascinating! Much
work still to do but all is going well. I still have to run the rest of
the transformers (they vary a lot from different manufacturers but I am not
sure that affects to results yet) and then get this all put together in a
coherent format to share.
I think Bart just posted his data on ballasted pig coils.
Cheers,
Terry
At 07:20 PM 9/7/00 -0700, you wrote:
>
>Terry -
>
>Thank you for the test data. How do you find the time to do all the work?
>The PFC problem is always difficult because of the varying load conditions.
>The surging currents and distorted waveforms don't help. However, it is a
>challenge worth trying. The question is how should the columns be set up for
>the various NSTs?
>
>My solution follows and is similar to yours.
>
>Type of NST 9/30
>Line amps 3.351
>VA 120 * 3.351 = 402.12
>Real AC watts 164.3
>% Power Factor 164.3/402.12 = .4086 * 100 = 40.86
>Phase angle degrees arc cos(.4086) = 65.88
>Var 402.12 * sin (65.88) = 367.01
>PFC cap 367.01/(6.823*60*120^2) = 67.60
>
>ammeter current 402.12/120 = 3.351
>wattmeter current 164.3/120 = 1.369
>Var current 367.01/120 = 3.058
>
>However, the 67.6 uf cap would not be correct for all 9/30 NST Tesla coils
>because the load would vary depending on how well the TC system is adjusted.
>For example, the load may be 9000*.03 = 270 watts
>This would require a 54.89 uf PFC cap. If a 67.6 uf cap is used it would
>give a leading current.
>
>For the VAR I used the trig function sine. You used the pythagorean theorem.
>There are several ways to solve the PFC problem.
>
>Are the BPS and Isec mARMS important? This would show up in the changes of
>currents? As you say it is messy.
>
>I would be interested in some data on pigs with ballasts.
>
>John Couture
>
>-----------------------------
>
>
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Wednesday, September 06, 2000 1:39 PM
>To: tesla-at-pupman-dot-com
>Subject: RE: NST Charging Circuit Study
>
>
>Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
>Hi John,
>
> Here is a "test" run I did. 9000 Volt 30mA NST with a static gap.
>
>
>Cpri AC line BPS Isec mARMS Real AC line
> Amps RMS Power In
>2.5nF 2.583 764 31.896 173.89
>5nF 3.043 392 37.927 185.05
>7.55nF 3.287 244 41.282 179.8
>10nF 3.351 120 41.8 164.3
>12.5nF 3.656 120 47.57 166.1
>15nF 3.85 76 48.796 142.84
>17.5nF 3.762 60 46.596 126.95
>20nF 3.79 48 47.53 123.6
>22.5nF 3.882 2 48.54 62.23
>25nF 3.77 1 47.33 51.88
>27.5nF 3.656 1 45.89 50.41
>30nF 3.628 0 45.43 39.46
>
>These are the "raw" numbers from which all kinds of stuff can be calculated.
>
>The 1 and 2 BPS numbers are just the gap firing right after the initial
>turn on surge. The gap does not fire in steady state.
>
>The resonant at around 5nF and the LTR values at around 10-12nF are clearly
>seen.
>
>
>Is this data OK? I don't want to leave out anything but I don't want to
>take more numbers than needed. That static gap case is pretty easy but the
>sync rotary case will need the timing optimized for each, which will be a
>chore. The real power actually does add up to the heat loss in the system
>so it does work ;-))
>
>For power factor at say 10 nF:
>
>Real power = 164.3 watts
>VA = 120 x 3.351 = 402 VA or "apparent power"
>Power factor = Real power / Apparent power = 164.3 / 402 = 0.4087
>VAR = SQRT(402^2 - 164.3^2) = 367.11 VAR (that's sort of similar to using
>inverse trig functions ;-))
>ACOS (164.3 / 402) = 65.876 degrees lagging for a power factor of 0.4087
>(hey.. that's not good! ;-))
>Or 1.37 real amps and 3.351^2 - 1.37^2 = 3.058 amps reactive. That would
>take a 67.6uF cap to fix...
>
>One can multiply the energy stored on the cap by the BPS to get energy
>going into the system. Of course, I am just trying to get the base numbers
>and leave such calculations for later.
>
>Note that MicroSim is very good a piecewise integration and analysis. Thus
>it can "measure" things which would be difficult in real life. Real power
>and true RMS are child's play for it even when the signals contain DC to
>multi-megahertz or pulsed components. I think I will take the steady state
>values and eliminate to start up portion of the signals. The turn on
>portion is interesting but not valuable for this purpose.
>
>So from the basic numbers the study gives all the fun stuff can be derived.
> If there is anything that needs to be added, let me know.
>
>It should be noted that the waveforms are FAR FAR from nice sine waves.
>MicroSim does the piecewise integration but care should be used in
>generalizing to functions and definitions that were meant for sine waves.
>The phase angle has no meaning in some of these simulations but the
>"equivalent" average values do.
>
>I have or am getting data for the following NSTs:
>15/60
>15/30
>12/30
>9/30
>
>I guess 12/60 and 9/60 are "rare" ;-))
>
>I will do both static gap and sync rotary 120 (BPS) calculations. This
>should pretty much cover the NST Tesla coil spectrum. I could do OBIT too
>if I can find the data... I'll wait on the pig and PT stuff since others
>may beat me to the wire there ;-)) The addition of variable ballast and
>reactive vs resistive makes that really messy!
>
>Ideas or comments welcome.
>
>Cheers,
>
> Terry
>
>
>
>At 12:19 AM 9/6/00 -0700, you wrote:
>>
>>Terry -
>>
>>Note that to get the right answers you will need to set up MicroSim to use
>>the trig functions. The actual line side currents would have to be known.
>>This would give you the volt amps. The secondary volts and amps would give
>>you the watts. You could then easily determine the VAR.
>>
>>John Couture
>>
>>------------------------------
>>
>>
>>-----Original Message-----
>>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>>Sent: Tuesday, September 05, 2000 5:03 PM
>>To: tesla-at-pupman-dot-com
>>Subject: NST Charging Circuit Study
>>
>>
>>Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>>
>>Hi All,
>>
>> With all the recent talk of cap sizes, PFC caps, and break rates it would
>>not be that hard just to crunch through all the variables in MicroSim and
>>just come up with a set of tables. However, I don't have all the
>>transformer data.
>>
>>I need to know three things to model an NST:
>>
>>1. Primary DC resistance.
>>2. Secondary DC resistance.
>>3. Open load AC current draw at rated input voltage.
>>
>>The NST transformers that I need this data for are:
>>
>>15/30
>>12/60
>>12/30
>>9/60
>>and any others that people may have a use for.
>>
>>The resistances can be found with just about any ohmmeter. The input
>>resistance will probably be very low but close is fine.
>>
>>For the AC measurement, you will probably want to turn the voltage up and
>>down slowly with a variac. Just switching an NST on suddenly may cause a
>>current surge that will pop the fuse in the multimeter. Of course, beware
>>the output voltage. There must be nothing at all connected to the output
>>terminals for this test.
>>
>>If anyone would like to take this data or you already know it, please send
>>the info to:
>>
>>terrellf-at-uswest-dot-net
>>
>>Do be very careful of the high voltage and AC voltage on the third test!!
>>
>>Thanks a bunch!,
>>
>> Terry
>>
>>
>>
>
>
>