Re: Pole Pig Wiring

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: DRIEBEN@xxxxxxxxxxxxxxx 

Gerry,

Yes, the core is bonded and grounded to the external
steel tank shell of the transformer. I'm no utility
company electrical engineer but I have taken a 10 kVA,
14,400 volt distribution transformer completely apart
and drained the oil out, then put it all back together
again and refilled with oil. And yes it did still work
once reassembled ;^) The internal core assembly is in-
ternally fastened to the tank shell in 3 places - one
at the bottom and two on the side of the shell, 180 de-
grees apart. It looks like you've pretty much answered
the rest of your own questions by ohming it out ;^)

David Rieben



----- Original Message -----
From: Tesla list <tesla@xxxxxxxxxx>
Date: Monday, May 2, 2005 4:37 pm
Subject: Re: Pole Pig Wiring

> Original poster: "Gerald  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Thankyou David,
>
> I might try to ohm out this thing, now that I'm curious.  Do you
> know if
> the core is tied to the case internally???
>
> I just ohmed it out.  The LV windings are indeed connected to the
> center
> post (and the two outer posts) and the resistance is too small to
> for a 2
> probe measurement.  I will run a current source thru the LV
> windings and
> measure the voltage drop.  This will tell me if the windings are
> in series
> or parallel (I hope in series for 240V operation).  Do you know if
> for 120V
> operation the LV windings are connected to the two outside posts
> and the
> center post is  internally unconnected???  The primary and
> secondary
> windings are isolated from case.  I just cant tell what is done to
> the core.
>
> Finished the resistance measurements  LV1 is 30 milli ohms and LV2
> is 20
> milli ohms and they are indead in series and the center tap is
> connected to
> the center post..  LV2 must be an inner winding cuz of the lower
> resistance. The HV windings (bushing to bushing) measures 180
> ohms.  A
> little better than an NST??  It is hard to imagine much of any
> temp rise in
> the pig since with 50 amps in LV and .83 amps in HV.   The I2R
> loss is 250
> watts (running a 5KVA pig at 12KVA).  Dont know what the core
> losses would be.
>
> Gerry R
>
> >Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
> >
> >Gerry,
> >
> >I don't think that the center secondary low terminal of a pig is
> internally>connected to the core although the untility company
> will often externally
> >connect a grounding buss strap from the center terminal to the
> case of the
> >external tank. That's the reason that you can run a pig with 240
> volts input
> >into the secondary low voltage terminals of the pig with one side
> of the
> >240 volts ballasted through a welder. If the center terminal was
> already>grounded, you would be unable to ballast  the input
> properly. For that
> >reason, this terminal is left unconnected.
> >
> >David
>
>
>
>
>