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Re: Pool Pig...



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

Hi Chip,

You may want to check if your pig with the selector switch has its voltage specified from bushing to ground or from bushing to bushing (assuming a two horned pig). The 7200Vac may be from bushing to ground and if two bushings, you would have 14400 between them.

Large PIGs do have large Cres and LTR (larger than resonant) operation may be expensive. Many operate STR (smaller than resonant). However, if you do go STR, you will need to get the BPS high to keep the output voltage low enough. A rough estimate once you choose your STR cap value and the voltage you want to operate at, is to calculate the BANG energy and divide this into the power level that you ballast at.

Example: assume the 100nf used in the green monster and ballasted at 15KW. Also assume that the maximum voltage allowed will be 14.4KVrms * sqrt(2). This will give you about 20400Vpeak. The BANG energy (at 20.4KV) will be 20.8 joules. Therefore, the needed BPS will be:

BPS = 15000 / 20.8 or 720.

You can see that you will need a very high speed ARSG to keep the voltage under control if you ballast for full power.

Gerry R.


Original poster: "Chip Ford" <chipford@xxxxxxxxxxxx>

Ok...there are many kinds of transformers out there. Seems that the really BIG coils use a pole pig. Such as "The green monster". His is a 15kva @ 14400 volts. Using the math KVA = ((VOLTS X AMPS) / 1000), I came up with an amperage of @ 1.042 Amps (15,000 watts). Since .001 Amps is equal to 1ma, he has 1042ma. According to my calculations, the resonant cap is @ .1919 uf. I think he said his cap was .1uf...close but not real close..Now, I think alot of the line transformers have a selector switch on them. I think they are like 7200, 6400, 5600 volts for the ones around here. So, if I have 15 kva transformer @ 7200 volts, it will have an amperage of @ 2 amps (2000ma)(15,000 Watts). At this rate, my cap is gonna be around .75 uf. This is really high and from a few calculations that I have made, A secondary coil 12" 81/2" dia. 48" tall will need over 10000 turns of #39 awg. wire on it. This pretty much makes this transformer unusable. Besides that, where is a hobbest ever gonna find a cap? Am I missing something here? Are my calculations incorrect? Am I looking at the transformer incorrectly? Please comment...Chip Ford