Re: Pole Pig Question: (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Fri, 25 May 2007 10:01:09 -0700 (PDT)
From: J. Aaron Holmes <jaholmes@xxxxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Pole Pig Question: (fwd)

You really shouldn't refer to pole pig secondaries as
"center-tapped".  For the average U.S. 120/240V pig,
that is simply not true.  There are *two* 120V
secondaries configured in parallel or series according
to the service type, as I explained in my prior mail. 
If there really was only a single center-tapped
secondary, this would not be possible.

Actual "center taps" in distribution transformers seem
to be, in reality, a bit unusual.  The most common use
of a center tap that *I've* seen is on 240V delta
three-phase transformers, where one of the 240V
windings is sometimes center-tapped to provide 120V
without the requirement of a separate transformer.

Cheers,
Aaron, N7OE


--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: List moderator <mod1@xxxxxxxxxx>
> 
> 
> 
> ---------- Forwarded message ----------
> Date: Fri, 25 May 2007 10:40:53 -0400
> From: Jonathon Reinhart
> <jonathon.reinhart@xxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Pole Pig Question: (fwd)
> 
> OK, I guess I was a *little* off... but the general
> idea was right... I
> think... :-P
> 
> Sorry for any confusion...
> 
> Jonathon
> 
> On 5/25/07, Tesla list <tesla@xxxxxxxxxx> wrote:
> >
> > Original poster: List moderator <mod1@xxxxxxxxxx>
> >
> >
> >
> > ---------- Forwarded message ----------
> > Date: Fri, 25 May 2007 08:24:11 -0400
> > From: Jonathon Reinhart
> <jonathon.reinhart@xxxxxxxxx>
> > To: Tesla list <tesla@xxxxxxxxxx>
> > Cc: rrreinhart@xxxxxxxxx
> > Subject: Re: Pole Pig Question: (fwd)
> >
> > I always thought it was best to look at it first
> as just what you said: 1
> > Primary (HV) = 1 Secondary.
> >
> > X1            X2
> > O             O
> > |                |
> > vvvvvvvvvvvvvv   HV
> > =========
> > ^^^^^^^^^^^^^^   LV
> > |        |       |
> > O      O     O
> > L1     N     L2
> >   \     / \     /
> >    120   120
> >
> > Remember the secondary coil is center-tapped, so
> for now, just think about
> > the secondary coil as a whole. The voltage
> waveform across L1 and L2 will
> > look exactly like the waveform across X1 and X2,
> just as one would expect.
> > The tricky part comes in when you add that
> centertap, and the confusion is
> > this:  Voltage is relative.  Now without any
> grounds connected, all of
> > these
> > voltages on the LV side are simply relative to
> each other (I think they
> > might float at whatever actual voltage they wish).
>  But L1-L2 is 240VAC,
> > L1-N is 120VAC and L2-N is 120VAC.
> >
> > Now, we ground one of the terminals so that the
> voltage is stable and has
> > a
> > reference point. We COULD (but don't), decide to
> ground L1.  In this case,
> > we could get 120V to ground at N, and 240V to
> ground at L2.  In this case,
> > when N was at +120V, L2 would be at +240V (and
> same for the negative
> > side).
> >
> > However, it makes much more sense to ground that
> centertap.  Now the
> > difference between L1-N is 120VAC and L2-N is
> 120VAC, but at a given
> > instant
> > when L1 is at +120V to ground, and L2 is at -120V
> to ground, because they
> > are wound the same direction, but on opposite
> sides of the centertap.  We
> > ground this center tap, because now, we can still
> get 240VAC by connecting
> > to L1 and L2, but we can never get more than 120V
> to ground, which is
> > safer.
> > The only way to get a 240V shock is to touch both
> L1 and L2, which is
> > well,
> > pretty unlucky.
> >
> > Hope this helped,
> >
> > Jonathon
> >
> > On 5/24/07, Tesla list <tesla@xxxxxxxxxx> wrote:
> > >
> > > Original poster: List moderator
> <mod1@xxxxxxxxxx>
> > >
> > >
> > >
> > > ---------- Forwarded message ----------
> > > Date: Thu, 24 May 2007 16:14:32 -0500
> > > From: Jim < branley1@xxxxxxxxxxx>
> > > To: tesla-request@xxxxxxxxxx, Tesla list
> <tesla@xxxxxxxxxx>
> > > Subject: Pole Pig Question:
> > >
> > >
> > > Hi Folks:
> > >
> > > I have received from you a bucket truck load of
> insightful input on pole
> > > pigs that has helped me to better understand
> them, thanks.
> > > What seems to be evading me is  How can a single
> primary feed create 2 -
> > > secondaries that are alternating in current.
> > > I always assumed that 1 - primary feed equals 1
> - secondary wave form
> > > not 2 - alternating wave forms.
> > >
> > > Your help is greatly appreciated,
> > >
> > > Jim
> > >
> > >
> > >
> > >
> >
> >
> >
> 
> 
>