Overhead XFMR Bank - Picture
Overhead XFMR Bank - Picture
(OP)
Can someone provide some insight on the below Overhead XFMR Bank picture. Here is what is known (from top to bottom):
Top Conductors - 2400/4160Y, 4-wire, 3-Phase Primary
Middle Conductors - 120/240V, 3-wire, 1-Phase Secondary (taps are for house service drop from this pole)
Bottom Conductors - 240V, 3-Wire, 3-Phase Secondary
Each OH XFMR - 50 KVA (serve 240V, 3-Wire, 3-Phase Secondary)
My specific question involves the primary connection of the two 50KVA XFMRs.
I have been advised that the XFMRs are connected Open-Delta / Open-Delta.
It appears that one of the XFMRs is connected phase-to-phase (4160V), while the other XFMR is connected phase-to-neutral (2400V). What am I missing here?
Top Conductors - 2400/4160Y, 4-wire, 3-Phase Primary
Middle Conductors - 120/240V, 3-wire, 1-Phase Secondary (taps are for house service drop from this pole)
Bottom Conductors - 240V, 3-Wire, 3-Phase Secondary
Each OH XFMR - 50 KVA (serve 240V, 3-Wire, 3-Phase Secondary)
My specific question involves the primary connection of the two 50KVA XFMRs.
I have been advised that the XFMRs are connected Open-Delta / Open-Delta.
It appears that one of the XFMRs is connected phase-to-phase (4160V), while the other XFMR is connected phase-to-neutral (2400V). What am I missing here?






RE: Overhead XFMR Bank - Picture
Open-delta/open-delta could provide the two secondary voltages you describe by using the center-tap of one of the secondaries.
Are you sure the bottom primary is a neutral?
RE: Overhead XFMR Bank - Picture
RE: Overhead XFMR Bank - Picture
Please verify if the primary side (Y, 3 phase).
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RE: Overhead XFMR Bank - Picture
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RE: Overhead XFMR Bank - Picture
I'm leaning towards the 2-phase theory already presented by cuky2000, and, as also previously stated, it must be an old distribution system. Where is the picture from?
RE: Overhead XFMR Bank - Picture
So you may have either 2 neutrals amongst the four primary wires, or one of the three phases is there twice in an open-delta (say A phase on the top and bottom).
RE: Overhead XFMR Bank - Picture
With the help of the above posts, it took me about a 1 minute to figure out what was going on.
The picture below shows that the far right primary terminator does connect to either of the transformers.
It must be a remant from days past when there were actually 3 transformers mounted on this pole to provide 3-phase secondary service.
Thus, this is a simple Open-Wye / Open-Delta transformer configuration to provide 3-phase secondary service.
Thanks for the assistance. The key observation was the fact that there are only 2 primary cutouts.