Issue:
Transformers are capable of being wired in both forward and reverse directions, but often not without complications
Transformers are capable of being wired in both forward and reverse directions, but often not without complications
Product Line:
LV Transformers
LV Transformers
Environment:
Applies to all SquareD/Schneider Electric Transformers
Applies to all SquareD/Schneider Electric Transformers
Cause:
Customers often desire a voltage change that is reversed from the designed orientation of the primary and secondary windings
Customers often desire a voltage change that is reversed from the designed orientation of the primary and secondary windings
Resolution:
1. The practice of backfeeding a general purpose transformer is NOT recommended, especially in transformers smaller than 3Kva. Backfeeding is not allowed for any Industrial Control Transformers of any size, because windings are compensated and backfeeding will result in lower than expected output voltage.2. Backfeeding causes very high excitation inrush, making coordination to breakers or fuses difficult without exceeding the limits set by the National Electrical Code. Avoid backfeeding wherever possible for this reason.
3. If a Delta-Wye transformer is to be backfed so that the Wye side is the input, do not connect the neutral terminal to the primary system neutral, nor should the neutral terminal be connected to ground.
4. If the transformer has taps, when backfed the taps do not help compensate for poor (other than nominal) source voltage to provide the appropriate magnetic flux levels in the core as they are designed to do.
Released for: Schneider Electric Canada
