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Re: More Tuning/Debugging



Quoting huffman <huffman-at-fnal.gov>:

> What is this 'star' 'delta' stuff anyway? I thought these pigs
> were single phase? I am familiar with these terms in a three 
> phase system however. I also realize that the  120/240 side is
> two phase 180 deg. (my roommates and I once got 240 by using 
> two separate wall sockets in our appartment). dave huffman

Pole pigs typically have three LV bushings, and two low voltage
windings connected to them. Most buildings use 120/240 volt
single phase juice. The transformers that supply this juice
usually have both of the LV windings in series. One end of each
LV winding is connected to the center LV bushing which is also
commoned to true earth ground. The center bushing then becomes
the neutral conductor. This configuration, even though everthing
is single phase, is commonly referred to as a "Delta" wired pig.

"Star, Wye, or Y" wired pigs, are pigs where only two out of the
three LV bushings are used. Both LV windings are placed in
parallel and 120 volts is the maxium potiential you can typcially
get, though you can pull twice the current.

These terms apparently carry over from the wiring configurations
typically used when more than one pig is employed to step-down HV
from a polyphase line. Since these two configurations (star=wye=y
& delta) apply to the LV wiring of pigs used in single phase
applications the terms are commonly used in the industry on ALL
pigs.

Good use of some basic utility vocabulary is almost essential if
you are interested in securing a pig from an industrial supplier.
Single unit orders are a pain for most of these guys, and they
want to feel comfortable that the pig will be used in a safe and
responsible manner. The Tesla coiler who gets on the phone
attempting to purchase a single pig should be able to respond
properly to a few buzz words that are inevitably thrown out. 


Richard Quick


... If all else fails... Throw another megavolt across it!
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