Single Phase Panel Fed from 3 Phase Transformer

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Brettmc13

New member
Location
Texas
This is more for my own curiosity, as we bit the bullet and purchased the proper transformers, but here is the back ground and my questions-

We have 16 trailers we are going to be using as offices at a jobsite. My initial plan was to have the utility company drop a 480v service to a panel with a disconnect and breakers, then from the panel to 2 240/480 to 120/240 single phase transformers, which would then supply 2 120/240v panels. Then from the panels, I would feed each trailer panel, as the trailers are coming pre-wired with 120/240v single phase.

After doing some looking around, I found out another job in our district had 2 transformers they were willing to send me, free of charge. The catch was they are 3 phase, but everything else matched. I have heard of using 3 phase transformers to supply single phase loads, but only in 120/208, which makes sense. I've never actually done it myself. Long story short, I mentioned it in passing and offered to look into it more, and was told to just order the right transformers, which I agree with.

My Questions-

Would the 3 phase set up work? If so, how? I work in the industrial sector, so aside from lighting and convenience receptacles, my knowledge on this type of stuff is pretty lacking.

Thanks in Advance.
 

kwired

Electron manager
Location
NE Nebraska
My initial plan was to have the utility company drop a 480v service to a panel with a disconnect and breakers, then from the panel to 2 240/480 to 120/240 single phase transformers, which would then supply 2 120/240v panels. Then from the panels, I would feed each trailer panel, as the trailers are coming pre-wired with 120/240v single phase.

Unless there is 480 volt load to also feed or long run/voltage drop issues, why not just have them drop a 120/240 service to begin with?
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
Unless there is 480 volt load to also feed or long run/voltage drop issues, why not just have them drop a 120/240 service to begin with?

I agree. Our biggest was an 800 amp 120/240v single phase service for an office that was expanding. It's not common, but sometimes the POCO can source larger than normal single phase transformers.

It's worth asking the POCO at least.
 

kwired

Electron manager
Location
NE Nebraska
I agree. Our biggest was an 800 amp 120/240v single phase service for an office that was expanding. It's not common, but sometimes the POCO can source larger than normal single phase transformers.

It's worth asking the POCO at least.
If the load is there and you don't balance it across all three phases they still need relatively large three phase transformer.

For temp service at a jobsite, it may still cost less to have multiple 120/240 single phase services then to eat costs on low voltage transformers.
 
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