Re: Pri circuit effective resistance.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi DC,

At 08:17 PM 10/1/2006, you wrote:


> Did the 0.16 value include your total primary circuit or just the 
> value thru the SISG switching device?

The SISG is 0.16 ohms which "oddly drops lower" at higher firing 
voltages.  I "guess" at a total of 0.25 ohms, or an added 0.09 ohms 
for the wiring, coil, etc. which seems to be a high guess.  So the 
total R primary resistance should not be higher than 0.25 ohms 
total.  The resistance drop at higher voltage is probably the SISG 
just getting naturally more efficient and/or the anti-parallel diodes 
are lagging on a bit and just making it look more like a dead short 
as Dest mentioned.

The impedance of the primary circuit is SQRT(L/C) = SQRT(15e-6 / 
165e-9) = 9.54 ohms.  It is very hard to directly measure any effect 
of the 0.25 ohms of the primary "added resistance".  Ipeak = Vfire / R so:

4800 / 9.54 = 503.1 A

4800 / (9.54 + 0.25) = 490.3 A

A 2.5 % difference so It is almost impossible to measure directly 
just by firing voltage and current alone since the difference is well 
into the measurement error.  The only way I know of measuring it is 
to remove the secondary and look at the ringdown and figure out the Q 
from there.

http://drsstc.com/~sisg/files/SISG-coil/SISG-TPtest-FollowUp.pdf

http://drsstc.com/~sisg/files/SISG-coil/SISG-TPtest.pdf

In this case, I was worried about the MOT's proximity hurting the coil's "Q"...


> Regarding the effective resistance in the pri circuit, 3 Ohms vs 
> 0.16 Ohms is a tremendous difference as with regards to performance.

You Bet!!  That is why the PARANHA can push 40+ inch arcs from one 
laziliy running MOT!  The MOT's power factor to the AC line is 
excellent and it is still running about 105VAC in so core saturation 
is not even an issue!

http://www.pupman.com/listarchives/2006/Aug/msg00410.html


> Would you suspect also that the DRSSTC IGBT switched coils are also 
> seeing effective resistance in this range?   Anyone on the list like 
> Steve W. actually measured this value?

If the resistance was significantly higher than I "wish", the coil 
simply would not work...  For the SISG, if the primary resistance is 
too high, one does not need to worry about building the rest of the 
coil since it is already completely doomed!!  The RMS currents in the 
primary of an SISG coil like the PIRANHA are enormous!!!  Like 
35Arms.  With 820 watts in, one can find the primary resistance where 
there is no power left:

820 = 35^2 x R      R = 0.67ohms

So if the primary resistance reaches 0.67 ohms, ALL the coil's power 
is LOST!!!  It is sort of weird, but primary resistance is super 
critical in the SISG.  I used an aluminum standoff for a connection 
and it almost melted down!!.  Copper, brass, and normal plated 
non-inductive connectors run just a little warm without problem though.


> This would certainly explain why the DRSSTC's only require approx 
> 400 - 500 Watts per foot of spark output vs the usual 1 kW for classic coils.

PIRANHA is about 250 W/foot (which is an interesting way to look at 
things).  Another way to look at it is at my usual 4800V firing 
voltage nothing in the drive even gets "warm"...

http://drsstc.com/~piranha/PIRANHA/PIRANHA.pdf

I need to "update" a lot of the stuff there...  Nothing has changed, 
but much more info could be added...  I "only" use SISG coils now and 
I am extremely pleased with them!!!

Cheers,

        Terry


> Dr. Resonance