Original poster: "Mike" <mike.marcum@xxxxxxxxxxxx>I think what he did was put 2 pig cores in 1 tank to reduce bulk. Tank looks tall enough to do that. But with no midpoint grounding between the 2 I would see why there would be corona with same clearances and 2x voltage.
Mike ----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx> To: <tesla@xxxxxxxxxx> Sent: Friday, October 20, 2006 3:17 PM Subject: Re: 10kva pole pig needed with 29kv primary
Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Scot,I seems like one could ground one of the bushings for each of the two PIGs and connect the two chassis to ground. If one phased the LV of the two PIGs correctly, you would have +14400V output from one PIG and -14400V from the other PIG and then connect them in series so you have 28800V across the two bushings but any one PIG would only see 14400V. Is this the case where you experienced corona sizzling inside the case. I thought that grounding one of the bushings of a two bushing PIG was an OK thing to do so I'm not clear on the need to "triple the insulation between the trannies and the case.Gerry R.Original poster: BunnyKiller <bunnikillr@xxxxxxx>looks like Bellsouth doesnt like alot of traffic.... thats why I dropped them and went to Cox Cable... but anyway..yes I seriesed 2 14.4KV piggies for 28.8 KV and when driven by the variacs can obtain a little over 30KV but at 10KVA ( both piggies are rated for 10KVA)when seriesed transformers are applied ( considering both are equally made) you get additive voltage but the amperage remains equal. If paralleled, you get the opposite... same voltage but additive amperage.If one plans on placing two piggies in series, you NEED to triple insulate the trannies from the case very well... seems that the clearances from the case walls and the trannies is minimal for the original voltage set. Dont throw away any of the "paper" insulative material found in the case and consider procuring even more, you will need as much as you can use. Pay attention to the way the trannies are originally set up when you open the case... draw a schematic of how it was connected. Also another thing to watch for is the "polarity" of the transformers output, its the same as in NST or MOT applications when going series.as far as connections, I paralled the "primary" ( input) side of the coil and seriesed the "secondary" ( output) side.Even tho I have a bundle of insulation in my piggie, at the higher input voltages ( when the output is getting into the 29KV plus) you can hear "corona sizzle" in the case. I also ground the case to a dedicated ground rod just in case something breaks down....Scot D Tesla list wrote:Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx> Hi Jim, Yes, you could do exactly that ;^) Or, if you have at least one of the pig trannies with 2 HV bushings, or "horns", you could "float" one at 14,400 volts and "piggy-back" it on the other one's output for additive voltage. Of course, you'd at least want the pig that's floating at 14.4 kV to be a 2 HV bushinged unit, as the outer tank of a pig floating at 14.4 kV, relative to ground, would be an electrocution waiting to hap- pen ;^0 The pigs' BIL rating should allow for piggy-backing of the HV output of one pig on another, though. I think Scot "Bunnykiller" Dingman uses 2 seriesed 14.4 kV pigs for up to ~30 kV input for his big coil's primary circuit. He discusses this on his website. http://bellsouthpwp.net/B/u/BunnyKiller/bigpig.html David Rieben