Unrecognized Transformer

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ddragoo

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I have a job I am working on that the spec says requires a transformer with a configuration I am not familiar with. Does this make sense to anyone or does this look like a typo?

Transformer - An Isolation Transformer with the following characteristics shall be
provided: 25kVA, Electrostatic shielded, K-4 factor, Single-Phase Dual
Primary Voltage of 208 and 120/240, Secondary Voltage of 120/240,
Enclosure Type 2 (NEMA 2), Indoor Ventilated and Floor/Wall
mounting.
 
ddragoo said:
I have a job I am working on that the spec says requires a transformer with a configuration I am not familiar with. Does this make sense to anyone or does this look like a typo?

Transformer - An Isolation Transformer with the following characteristics shall be
provided: 25kVA, Electrostatic shielded, K-4 factor, Single-Phase Dual
Primary Voltage of 208 and 120/240, Secondary Voltage of 120/240,
Enclosure Type 2 (NEMA 2), Indoor Ventilated and Floor/Wall
mounting.
Click to expand...

what part of it do you think is a problem?
 
The part of it that LOOKS a bit unusual might be the "Primary Voltage of 208 and 120/240" on a single phase transformer. The center tapped primary side would not be standard (and makes little sense). Standard would be a 240x480V primary, with 2 x 5% taps FCBN and 1 x 5% FCAN, 120/240V secondary. At the lowest tap you would be at 216 on the primary, so with a 208V input your secondary would be at 115/230 on the secondary side.

You could get this exact configuration custom built, for a price. I've seen this sort of arrangement (minus the center tap) as a catalog item for Control Power transformers, but not larger than about 2kVA
 
It looks like the spec calls for a dual voltage primary that can work either L1 to L2 on a standard single phase 120/240 system or L to L on a three phase 208Y/120 system.
In practice one or the other will actually be present. And in either case you get 240 single phase with a center tap you will ground.
 
The problem I am having is I have contacted two different electrical suppliers and neither of them can figure out what I need. I am not doing the install, I am just on the purchasing side of this job and nobody seems to know what we need. Does anyone have any suggestions as to what I should be asking for? Is this truly an isolation transformer. What am I isolating. It seems more like a buck/boost set up. 120/240 in 120/240 out. I am not that versed in the ways of transformers. I am much more used to the standard set up. 480/277 -208/120 etc, etc. What should I be asking for?
 
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