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Re: Pole Pig.

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Chip,

A few definitions may help:

ARSG = asynchronous rotory spark gap
SRSG = synchronous rotory spark gap (sync with line freq)
BANG energy (joules) = 0.5 * C * V^2 where V is the voltage that the cap charged to when the spark gap fired. 
Power (watts) is joules per second
BPS = Bangs per second (with rotary gaps sometimes called PPS or presentations per second). With ARSG not all presentation will fire so the actual BPS will be less than the PPS Average power processed by the spark gap is BPS * Average_Bang_Energy. Bang energy with ARSG will vary from one firing to the next.
Too high BPS can result in the RMS current getting too much for the caps and perhaps also waste too much power in the spark gap. There is also the practicality of having a high BPS in terms of rotary speed, size, and number of electrodes. There is a limit on how close together you can get the electrodes for a given RSG before it power arcs. Lot of these things you will gain a feel for with experience. For now, it is probably best to ask.
For most people, a ballast is nothing more than a high current capable inductor. Issues in its design (if you design one) is the wire guage for the desired current level, number of turns on the core, core area for the volts per turn that you end up with to prevent core saturation. Needed inductance can be calculated by first calculating the impedance needed to limit the current to the PIG:
ZL = Input_voltage(rms) / Desired_input_current(rms) - for low voltage ballasting of the PIG 

L = ZL/(2*pi*line_freq)
Note this inductance calculation is for short circuit conditions on the PIG output. With rotary spark gaps, the reactance of the tank capacitance can increase the current from this computed value. 

Gerry R.



Original poster: "Chip Ford" <chipford@xxxxxxxxxxxx>
Thanks for the almost over-whelming response from everyone. There seems to be some differences in opinion. I really don't understand everything you guys were talking about. Especially the "BANG" energy and figuring the joules. I assume this is what is released from the caps and dumped into the primary coil. The main differences seem to be the BPS. I assume that BPS = Bangs per Second. Is there such a thing as too many BPS? Also, instead of running the ARSG (Air Rotary Spark Gap I presume) faster. Couldn't you just add more moving electrodes or even better, a second set of stationary electrodes? If you do this, a 3450 rpm motor with 8 contacts will yield 460 BPS normally. When you add a second set of stationary electrodes at 45 deg. or maybe better 135 deg., you just doubled your BPS to 920 ! Does this sound right to everyone? Has anyone tried this?
Anyway, I am hoping to here something about my pole pig soon. I have acquired (2) Maxwell .03uf caps (37667). I am also hoping that the 7200 volts I spoke of earlier. is from bushing to ground. With a (2) Horned pig, This would yield 14,400 Volts indeed.
Now, can we talk about the ballast for a minute. The function of this and how to wire it in is a little fuzzy. I am thinking it will be wired in series with the with the primary curcuit. I have spent most of my "Tesla Time" working with NST. I have never used a "Ballast" with one. I am trying to understand what is going on with it. What I am getting so far is that this "Load" somehow keeps from over-volting things. I don't know how to figure what to use? I know where to get several different sizes of "Larger transformers" reasonabley priced, I just don't know what to look for yet nor what it's function is in a TC. I know that in an old automotive breaker point system, the ballast was a resistor used to keep from over-heating/over-volting the coil. I think that the "Ballast" in a fluoresent light is a Step-up transformer used to make the plasma in the bulb. I know that "Ballast" can also be wieght added to a ship or a race car for example. I'm sure someone out there will straighten me out on this stuff. 

My name is Chip and I'm an addict. To T.C's. that is......