Transformer isolation.

[Isaiah]

Maintenance wants to replace the primary side feeder of a 4160V-480/277V, power transformer. They want to LOTO the CB on the primary side feeder, but leave the secondary side CB closed, which connects to a 480V MCC bus. Maybe I'm missing something here, but isn't there a risk of back-feed into the primary windings from the secondary side?

 

[tom baker]

Yes a transformer works in either direction

 

[petersonra]

Maintenance wants to replace the primary side feeder of a 4160V-480/277V, power transformer. They want to LOTO the CB on the primary side feeder, but leave the secondary side CB closed, which connects to a 480V MCC bus. Maybe I'm missing something here, but isn't there a risk of back-feed into the primary windings from the secondary side?

If The transformer is feeding the motor control center and you shut off power to the transformer how are you going to get power from the MCC to backfeed?

 

[Isaiah]

If The transformer is feeding the motor control center and you shut off power to the transformer how are you going to get power from the MCC to backfeed?

Double-ended transformers with a Tie in between A and B busses.


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