Re: 180 BPS synch? (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 19 Jul 2007 14:52:18 +0000
From: David Rieben <drieben@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Cc: drieben@xxxxxxxxxxx
Subject: Re: 180 BPS synch? (fwd)

Hi Bart,

My RSG setup is very similar to yours except that my stationary
electrodes are 1/2" x 3" long tungsten mounted in brass blocks. I
believe my rotary disc is actually 11 1/2" OD with about 10 1/2"
flying electrode centers. My design is pretty much homemade and
I am NOT a machinist, so I probably can't get my flying electrodes
as close to the stationaries at each presentation as you can without
an occasional "tap" - I have to keep appr. 1/16" gap spacing to in-
sure no electrode tapping throughout the motor's rpm range. Still, I 
don't see ~ 1/8" total gap spacing at each presentation as problematic 
for 14.4 kV. My ballasting allows me up to ~ 20 kVA if my coil can 
stand it ;^) but it seems that after a certain point, the streamers just 
get brighter but not that much longer.

Keep 'em sparking,
David Rieben

-------------- Original message -------------- 
From: "Tesla list" <tesla@xxxxxxxxxx> 

> 
> ---------- Forwarded message ---------- 
> Date: Wed, 18 Jul 2007 23:07:15 -0700 
> From: Barton B. Anderson 
> To: Tesla list 
> Subject: Re: 180 BPS synch? (fwd) 
> 
> Hi David, 
> 
> I know you run twice the power I do on your big coils. I'm using 1.5" x 
> 0.375" pure tungsten electrodes in the rotary and the same electrode in 
> the stationary, except that the stationary electrodes are mounted in 
> large brass masses. This is something we might have in common. Another 
> item in common for probably most rotary's is the disc diameter which 
> affects a similar airflow and cooling ability. 
> 
> I have a 12" disc with a running electrode diameter of 10.6". For my pig 
> coil, this equates to about 46ms of mechanical dwell time. 3rd notch 
> quenching occurs at 276us. After quench, I have about 2.7ms of charge 
> time before the next alignment. It takes 5.76ms for full charge, so I am 
> firing at about 18.8kV peak vs 20.3kV peak. Still 92% with a time 
> constant of 2.55. That's based on .04uF cap size. My ballast limits me 
> to about 7200 VA. My electrodes are as narrow as I can get without 
> colliding, thus timing is serving everything. Most likely, few 
> misfirings as the voltage is plenty capable of arcing the gap at 
> alignment at 340 bps. 
> 
> The gap should actually do ok at even higher bps from a charge vs speed 
> situation (to a degree), but as you and I mentioned, we are seeing 
> sparks decrease beyond the 350 mark. So, I expect it's simply down to 
> crossing an efficiency barrier with the gap itself. 
> 
> Take care, 
> Bart 
> 
> 
> 
> Tesla list wrote: 
> 
> >---------- Forwarded message ---------- 
> >Date: Thu, 19 Jul 2007 03:06:19 +0000 
> >From: David Rieben 
> >To: Tesla list 
> >Cc: drieben@xxxxxxxxxxx 
> >Subject: Re: 180 BPS synch? (fwd) 
> > 
> >Hi Bart, 
> > 
> >Funny thing, I've always ran my big coils asynch and I too have 
> >found the optimum bps rate to typically be in the 300 to 350 bps 
> >range. I use a variable speed, permanent magnet DC motor for 
> >my RSG and find that with bps much lower than 300, the out- 
> >put is not as smooth and at much over 350, the sparks tend to 
> >get shorter - almost identical to your observations. I am just 
> >estimating the bps by the motor rpms as well but I come to the 
> >same conclusion ;^) My primary cap is .1 uFd, and fired with 
> >a 14,400 volt 15 kVA pig. 
> > 
> >-- 
> >David Rieben 
> > 
> >-------------- Original message -------------- 
> >From: "Tesla list" 
> > 
> > 
> > 
> >>---------- Forwarded message ---------- 
> >>Date: Tue, 17 Jul 2007 19:34:58 -0700 
> >>From: Barton B. Anderson 
> >>To: Tesla list 
> >>Subject: Re: 180 BPS synch? (fwd) 
> >> 
> >>Hi Phil, 
> >> 
> >>No, the modeling does not. I expect others have noticed similar optimum 
> >>bps rates when running in this mode and I expect they found their 
> >>optimum in the 300's somewhere (if they used a variable speed drive of 
> >>some type). This is not a synchronous motor and that should be inserted 
> >>here. This is simply an arsg using a VFD to control the speeds, 
> >>direction, torque, etc. 
> >> 
> >>I have noticed that if I begin going too fast, the spark lengths 
> >>decrease rapidly. It doesn't take much more. It also runs more 
> >>erratically at lower speeds but the spark lengths are still pretty good. 
> >>There is simply a speed at which the sparks are good and the spark 
> >>operation is "really" smooth. It's at that point where you can't hear 
> >>the spark gap at all and all you hear are the sparks themselves. When 
> >>running srsg, I could run good, but I was still stuck in one domain or 
> >>another. By varying the bps to whatever I wanted, with the help of a VFD 
> >>maintaining a constant speed at whatever I set it to, I could find the 
> >>best possible bps, at least for this coil and gap setup. I'm sure others 
> >>would have better performance at other bps ranges and I'm sure it's 
> >>based on gap efficiency and coil parameters. 
> >> 
> >>I determined the bps not through measuring, but by calculating the bps 
> >>based on the speed of the VFD reading. So, the number is based on a back 
> >>calculation. If there were a great number of misfirings, I would be off 
> >>by whatever margin. So, as I am big into measurements, I want to make 
> >>sure that is clear. 
> >> 
> >>Take care, 
> >>Bart 
> >> 
> >> 
> >> 
> >> 
> >>>Very interesting! Does the modeling explain this in any way? Have you 
> >>>noticed any tuning that significantly affects this sweet spot? 
> >>>I may have to try a variable-speed setup with my pig coil when I get it 
> >>>running! 
> >>> 
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