Cat's meow and 3-phase question was: Silly question?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 9/27/01 9:56:07 AM Central Daylight Time, tesla-at-pupman-dot-com
writes: 


>
> The site that shows the homebrew pig is located at 
> http://www2-dot-netdoor-dot-com/~maxz . The core is constructed by gluing together 
> the cores of small transformers. I collected a pile of transformers used to 
> supply street vapor lamps. The power company here does not care if you dig 
> in their dumpsters. The cores are easy to get apart with a hacksaw. I made a 
> good size square core by spot welding the cores together. I experimented by 
> using the existing primaries. By using a secondary with about 20 turns, I 
> found that the voltage output varied a lot when I changed the position of 
> the coil. I concluded that the performance of such a core was too erratic to 
> predetermine a set of design parameters. Also the core had a number of hot 
> spots during operation. Even though I made the core very uniform, it 
> probably had a complex of eddy currents. I am willing to bet that the wave 
> shapes of the output did not look anything like those of 60 cycles/sec. The 
> charging of a tank cap would be very erratic. In fact the owner of the site 
> e-mailed me that the transformer worked, but it blew his tank cap. I don't 
> know if rectifying the output of such a transformer would improve very much 
> the charging of the cap. By the way, it took the owner of the site 14 months 
> to hand wind the secondary. 
>
> Godfrey Loudner 



Godfrey, Luc, all, 

This just goes to show why most coilers (myself included) 
opt to purchase pre-made trannies instead of trying to con- 
struct one from scratch. Most of us just can't see the prac- 
ticality of going to all the headache of building our own tran- 
nies when you can purchase a like-new rebuilt 250 to 300 
lb. 10 kVA pole pig for around $300. And for us high powered 
coilers, piggies are built like the Rock of Gibraltar. Very sel- 
dom do you here of a coiler killing a pole pig in coiling activi- 
ties and if a pig does die in Tesla service, chances are it was de- 
fective in the first place. In my opinion, and from my personal 
experience, pole pigs are the cat's meow as power supplies 
for high powered Tesla systems! 

Now, I have a question about utility three phase transformer 
service that is bothering me and I was hoping some of the re- 
sident engineers could answer it  for me. I've read that a wye/ 
wye three phase transformer hookup is rarely used by the 
utility power companies because of harmonics and balancing 
problems. However, virtually all of the three phase pole pig 
banks that I see in my local area (Memphis, TN) are hooked 
up exactly this way (all three phases sharing a common 
ground return on both the primary and secondary sides of the 
transformer). I was wondering if anyone could shead light on 
this for me? 

Sparkin' in Memphis, TN, USA, 
David Rieben