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Re: 180 BPS synch? (fwd)



---------- Forwarded message ----------
Date: Thu, 19 Jul 2007 00:31:15 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: 180 BPS synch? (fwd)

Hi David,

The 1/16" gap between each stationary gap is about the norm I think. 
That's about where my gap is also. Your electrodes are larger than my 
own and can handle more power.  I'm not a machinist either, but I did 
have a machinist do the work (and it only cost me a case of Sierra 
Nevada!). You hinted that at higher power, brighter sparks. I can't 
really see that as I can't get the power high enough I guess. I've run 
my ballast to the point of smoking it, but after that (and a good 
cleaning), I decided to keep the power down to 7kva until I get a decent 
variac stack. I don't have my large coil any longer so I'm just running 
an 8.5" diameter coil with it (and kind of a high turn coil at 1789 
turns). Works ok, but nothing like my old 13" diameter coil did.

Take care,
Bart

Tesla list wrote:

>---------- 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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