Adding to Bjarney's excellent reply posts, I have some Questions to shoot at 'ya:
1: Does the Transformer Bank's connections resemble the ones in this schematic below:
Are the Transformers connected more like the way shown in this schematic below-as to the one on the left side:
2: Are the readings (testing voltage) with a DVM set on "X1" or readout for "000.00" VAC?
The readings might be a result of the Motor's contribution back into the supply, from unevenly loaded circuitry.
There are some methods to "Ballast" the input of Volt Meters, which might be a good topic for discussion here! (hinting towards Bjarney! He can describe much better what I mean and how to do it).
If the readings were taken at the Transformer's Secondary terminals, this might be a normal situation (Secondary voltage is read as + 104.5% rated output voltage during no-load situations - as a result of the Primary-to-Secondary %Z and Transformer's Regulation at idle).
The Voltage read when a moderate load is applied, brings it down to nominal rating area.
Looks like ØB / L-2 is the Grounded Conductor of this Corner Grounded Delta configuration.
Voltage readings of (apx.) 480 VAC from L-1 to L-2, L-2 to L-3, L-1 to L-3, L-1 to ground and L-3 to ground would be normal. L-2 to ground would be near zero Volts.
Refer to the above attached Schematics to find out why these Voltage readings would be normal.
For more information or Schematics, check the list of material posted at the Technical Reference area, by using the Menu For Technical Reference Section
, and selecting a link of interest.
FYI: If you right-click the link and open that item in a new window, you can keep the menu open/minimized for further selections!
Feel free to ask more questions.