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Re: 180 BPS synch? (fwd)

---------- Forwarded message ----------
Date: Thu, 19 Jul 2007 03:06:19 +0000
From: David Rieben <drieben@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
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" <tesla@xxxxxxxxxx> 

> ---------- 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! 
> > 
> > 
> > 
> >