RE: 3 phase pole pig (fwd), Zig zag transformer question (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 1 Nov 2007 22:49:25 -0700
From: Jim Mora <jmora@xxxxxxxxxxx>
To: 'Tesla list' <tesla@xxxxxxxxxx>
Subject: RE: 3 phase pole pig (fwd), Zig zag transformer question

Hello Ralph, et al,

Interesting, is the combined 120-0-120 180 degrees out of phase, or?
I have a 20KVA 3P diesel 480 delta genset for my big DC coil, a 480v 3p
delta to 208y configureable stepdown transformer and would like to have
120-0-120 for emergencies since I live in earthquake country. I am under the
impression that I can get 60% via this route, your thoughts?

Thanks,
Jim Mora
S.,Ca
   

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx] 
Sent: Thursday, November 01, 2007 10:09 PM
To: tesla@xxxxxxxxxx
Subject: RE: 3 phase pole pig (fwd)


---------- Forwarded message ----------
Date: Thu, 1 Nov 2007 23:39:21 -0500
From: sparks@xxxxxxxxxxxxxx
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: 3 phase pole pig (fwd)

> I think the Yyn0 would be my choice. I don't know what a "zig
> zag" winding is.

A zig-zag winding is used to connect a 3-phase transformer or alternator
to produce a single phase output, for instance, 120-0-120 volts.  In
this configuration, all three windings are connected in series as
follows:

(120)-/\/\/\/\-(0)-/\/\/\/\--/\/\/\/\-(120)

winding = /\/\/\/\/

Due to the phase angle between windings, 120 volts is produced across
one winding, and the other two windings in series produce an opposite
polarity voltage which is the sum of their phase angles that result in
120 volts.

The zig-zag configuration allows the device to handle in single phase
operation about 60% of the total rated 3-phase power.

I have a nice 40 KW 3-phase alternator here that happily makes 27 KW
single phase in zig-zag connection.

73,

Ralph   W5JGV - WD2XSH/7