ayrton:
I have a condition where a second floor panel in a server room, is being fed at a distance of roughly 400'.
How about feeding a 45 KVA Transformer in the NER (Network Equipment Room), with a 70 Amp 480V 3 Phase Circuit.
The 125 Amp Panelboard in the NER is fed by the Transformer.
This would eliminate the balancing issues per the use of Boost Transformers.
Seeing that the Building is (at least) 2 floors, with a linear measurement of 400 Feet, it appears likely the Building would have a 480Y/277V 3 Phase 4 Wire Service.
Using this approach would give the NER Panelboard a "Clean" Dedicated feeder, and more control over the Voltage across certain points.
It also removes the Load from another SDS Transformer + Panelboard, making it an independent Load.
If you go the Boost Transformer way, here is a Schematic for connecting (3) Transformers into an Auto Transformer Wye configuration (use this method if Boosting 208Y/120V Circuitry):
Figure #1: 4 Wire Wye Auto Transformer:
* Input: 208Y/120V 3 Phase 4 Wire;
* Output: 229Y/132V 3 Phase 4 Wire.
(SCHEMATIC: 1 LINE DIAGRAM)(SCHEMATIC: PICTORIAL DIAGRAM)To increase the Output Voltage to 244Y/149V 3 Phase 4 Wire, connect the Secondary Windings in Series, instead of Parallel (per the Schematics).
Series connection would be Jumper between X2 & X3 only.
Refer to
Voltage Boost Transformers - Wye Connection for more information.
Just for fun, this is an Open Delta Auto Transformer (Voltage Boosting) configuration.
*** IMPORTANT NOTE ***This configuration is only to be used on 3 Phase 3 Wire Circuitry (Single Voltage in/out only)
i.e.: 240V 3 Phase 3 Wire Circuitry.
Do not use for a "Dual Voltage" Circuit - i.e.: 208/120V
Figure #2: Open Delta Auto Transformer:
(SCHEMATIC: 1 LINE DIAGRAM)(SCHEMATIC: PICTORIAL DIAGRAM)This configuration's results:
* Input: 240 VAC;
* Output: 252 VAC.
For an Output Voltage of 264V, connect the Secondary Windings of each Transformer in Series (X2 to X3).
Refer to
Voltage Boost Transformer Schematics - Open Delta Configurations for more information.
Scott