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RE: Cat's meow and 3-phase question was: Silly question?
Original poster: "Loudner, Godfrey by way of Terry Fritz <twftesla-at-qwest-dot-net>" <gloudner-at-SINTE.EDU>
Hello Dave
One possible reason you see a lot of wye-to-wye connections between three
single phase units is for economic reasons. The voltage of each unit is only
58% of the line voltage. The single phase units need only be insulated for
relatively low voltage with the resulting cost reduction. The grounding
procedure you see will permit unequal loads on the three leads to be carried
through the neutral back to the generator. A third winding in each single
phase unit can be provided to suppress third harmonic voltages.
Godfrey Loudner
> -----Original Message-----
> From: Tesla list [SMTP:tesla-at-pupman-dot-com]
> Sent: Thursday, September 27, 2001 9:27 PM
> To: tesla-at-pupman-dot-com
> Subject: Cat's meow and 3-phase question was: Silly question?
>
> 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
>