transformer sizing
- Thread starter devosts
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- Illinois
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- retired electrician
If you are using a 3 phase transformer you will have 208/120 and not 120/240. Can you show us how you calculated 45 kva?
First the primary side of the transformer is a 600V 3 phase system. THe secondary side is a single phase 120/240V.
I was looking at 50 amps per trailer times 7 trailers. 350amps times 120v gives us 42kva roughly, that's why I was looking at 45 kva which is closest to a standard rating.
See Ya
devosts
I was looking at 50 amps per trailer times 7 trailers. 350amps times 120v gives us 42kva roughly, that's why I was looking at 45 kva which is closest to a standard rating.
See Ya
devosts
- Location
- Lockport, IL
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- Retired Electrical Engineer
You cannot have a three phase primary and a single phase secondary. You can have a hybrid, such as a 120/240 volt three phase with one phase having a grounded center tap. But only the one winding with the center tap will make 120 volts available. The other windings will only give you 240 volts. Calculating the KVA on such an animal is no trivial task.
If you had a single phase, 600 volt primary, and a single phase, 120/240 volt secondary, then the calculated KVA would be (7) times (50) times (240) equals 84,000.
If you had a single phase, 600 volt primary, and a single phase, 120/240 volt secondary, then the calculated KVA would be (7) times (50) times (240) equals 84,000.
If the 50A for each trailer(120/240v single phase) is correct, the total load will be 7x50x240=84000VA. The transformer shall be sized bigger than that.
There are single phase transformer and three phase transformer. In your situation, you need a single phase transfomer with primary voltage (600v) and second voltage (120/240v).
Hope this can help.
There are single phase transformer and three phase transformer. In your situation, you need a single phase transfomer with primary voltage (600v) and second voltage (120/240v).
Hope this can help.
If you have 3 phase 600 volt available I would go with a 3 phase transformer with 120/208 volt secondary. I would feed each trailer with 120/208 single phase. The only difference would be heating loads rated at 240 volts will only be rated at 75% based on the voltage supplied. The seventh trailer would be a little unbalanced but I don't think it would be a big concern. I think it would be a bigger concern using a single phase transformer off of a three phase primary system.
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