Re: MOT Coil operational notes

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

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?
 >
 >
 >