Re:RSG operational notes

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

Original poster: "Dr.Resonance by way of Terry Fritz <twftesla-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>


We run most of our medium size coils (4-6.5 kva) at around 380-450 pps using
a standard 1725 RPM motor.  No real advantage in running at 3450 RPM because
the sparks get to "stringy" indicating they don't have a lot of energy.  We
use a standard 1725 RPM 14 in dia rotor with 10-12 electrodes per rotor.  If
you do run at 3000 RPM or higher you need a very low series inductor in
conjunction with a pole pig to pump a lot of current into the caps.  Not
really worth the extra effort.

Also, if you run higher than 2000 RPM you really do need to use 1/2 brass
rod as the axial conductor on the rotor wheel.  Also 1/2 inch dia tungsten
electrodes --- 1/4 inch rod doesn't cut it --- too much heat.  Forget 1/8
inch for serious work above 5 kva.  Very poor quenching as the tungsten gets
red hot at the tip.  Shorting out the sec coil and running with a strobe
light you can clearly see this effect.

Usually no point in running additional series gaps as they dump a lot of
lost energy in heat and light.  Usually 2 gaps work best.  At around 8-10
kva then we use both sides of the rotor to get 4 separate gaps on larger
coils.  More than 4 just wastes energy.

Dr. Resonance




----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, December 02, 2002 7:39 AM
Subject: Re: MOT Coil operational notes


 > Original poster: "tesla by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<tesla-at-paradise-dot-net.nz>
 >
 > Hi Greg et al tnx for those thoughts
 > To answer your points
 >
 > 1) The ARSG can run up to 20000rpm  on a 12 bang per rev. I never actually
 > intended that it would be used up at 3000bps but I did mention it because
it
 > produced near vertical streamers nad I did not understand why at the time.
 >
 > 2) You are correct it does perform much better at lower bps. I dont know
the
 > optimum but it would have been around this 900 bps. Certainly a lot slower
 > that full speed
 >
 > 3) I did not run a static in series. I've done it in the past with SRSG at
 > 100bps and the results were very poor. Dwell time at 3000rpm is about
450us.
 > I'd question the requirment for dwell of 10us or so. With k of 0.1 (which
is
 > about what I have ) it will take some 10cycles of 57kHz for the first
notch
 > and this is 175uS to get the energy into the secondary. I do not
understand
 > why it would be seen as better to disconnect the primary before much of
its
 > energy has been transferred to the secondary. Can you perhaps amplify the
 > point on very low dwell times
 >
 > 4) Finn Hammer has given me much insight from his simulations and also
given
 > me much to think about. I'm currently querying him off list about the
model
 > parameters he is using. It is very clear that my firing times are very
wrong
 > and need changing. My historical thinking on how to calculate these was
just
 > plain wrong.
 >
 > 5) And no tank cap size has not been reduced. In fact I think I'll
actually
 > increase it to over 150nF and stay with the SRSG and see what this does
with
 > better firing times
 >
 > Best to you and list
 > Ted L in NZ
 >  >
 >  > (I'm not sure exactly on the type of gap you are using, but I seem to
 >  > recall you saying it was 15000 RPM)
 >  >
 >  > 3000BPS is pretty high - how does it go at say, 600-800 BPS.
 >  >
 >  > I think running over 1000BPS is really a waste of time.
 >  >
 >  > I would try running at about 600-800BPS, making sure the dwell time
 >  > is low. Are you running a decent static gap in series with the RSG??
 >  >
 >  > The problem you may have is this:
 >  >
 >  > To achieve 3000 BPS at 15000 RPM you need 12 electrodes. Therefore,
 >  > to run at 600 BPS, you must run at 3000 RPM. I don't know the size of
 >  > your electrodes and rotor, but I seem to recall it was just a
 >  > tungsten welding rod. Let's assume 200mm long, 5mm diameter.
 >  >
 >  > Soooo, D=200mm, Circumference= 628mm
 >  >
 >  > For 600BPS with 12 electrodes, you need to run at 50 RPS, which means
 >  > the velocity of the edege of the rod is 31.4 m/s
 >  >
 >  > Therefore, the absolute minimum dwell time is 0.005/31.4
 >  >
 >  > which is 0.00016 seconds, or 159 uS.
 >  >
 >  > This does not take into account the fact that the gap may fire just
 >  > before and until slightly after each presentation.
 >  >
 >  > Richard Hull, and the Corums did alot of work with async gaps and
 >  > found that the gap should quench in some TENS OF MICROSECONDS. There
 >  > is your problem right there. Your dwell time at "reasonable" break
 >  > rates is too high, so you get poor performance. You also need a
 >  > decent static gap in series to keep the quench time low.
 >  > SRSG quench times are less critical due to the extra time needed for
 >  > charging, etc etc.
 >  >
 >  >
 >  > Cheers,
 >  >
 >  > Greg.
 >  > Also, Have you tried using a slightly smaller tank cap?
 >  >
 >  >
 >  >
 >
 >