Tranformer selection, sizing, and calculations
Tranformer selection, sizing, and calculations
(OP)
Hello,
I would like to receive opinions on my transformer selection and calculation process to rectify any problems so I could be on the right track.
To feed a facility's electrical load via 3 phase, 800 A, 120/208V electrical service, I performed the following calculation to help me select a transformer. The utility line voltage is 25 KVA.
Minimum transformer size that I may require is 288 KVA, 3 phase. This may change based on how each phase is loaded to balance the system.
Usually utility may provide 288 KVA, 3 phase via either configuring three, 1 phase transformers of appropriate rating OR by supplying pad-mount transformer. Is it normal practice by the utility to provide 3 phase 288KVA via pole mount configuration?
Am I missing any other type of calculation that may be required in selecting and sizing a transformer correctly to send the information to the utility?
Thank you.
I would like to receive opinions on my transformer selection and calculation process to rectify any problems so I could be on the right track.
To feed a facility's electrical load via 3 phase, 800 A, 120/208V electrical service, I performed the following calculation to help me select a transformer. The utility line voltage is 25 KVA.
Minimum transformer size that I may require is 288 KVA, 3 phase. This may change based on how each phase is loaded to balance the system.
Usually utility may provide 288 KVA, 3 phase via either configuring three, 1 phase transformers of appropriate rating OR by supplying pad-mount transformer. Is it normal practice by the utility to provide 3 phase 288KVA via pole mount configuration?
Am I missing any other type of calculation that may be required in selecting and sizing a transformer correctly to send the information to the utility?
Thank you.






RE: Tranformer selection, sizing, and calculations
RE: Tranformer selection, sizing, and calculations
They like it when you can give them a breakdown of the type of loads you will have. Some are satisfied with a panel schedule that lists the type of loads and I have worked with some that wanted me to provide the breakdown to the nth degree.
Typically a breakdown like the follow is probably much more than they will need:
Lighting
Appliance (receptacle, etc.)
Plumbing (sanitation, etc.)
Mechanical (ventilating)
Mechanical (heating)
Mechanical (cooling)
Chiller
Transportation (elevators)
Kitchen
I did this breakdown for a utility on a smaller project and had to do more detailed breakdown on a larger project. Normally at most the transformer they provide will be 65% of what you calculated so I agree that a 150 kVA or 225 kVA would not be likely for them to provide.