Transformer voltages in a RV park

[Jimmyabtl]

On a bank of 3 120/208 600a 3 phase x-formers, can you get 120/240 single phase using the taps of all 3 x-formers???
This is used for a service to an RV campground. Thanks

 

[coulter]

Nope -

You can get two legs of 208 with the neutral, giving you 208 L-L and 120 L-N.

carl

 

[iwire]

Or you you may be able to get 3 phase 240 line to line with some tap changing, of course you would be about 138 volts line to neutral....a little tough on the 120 volt appliances.

 

[Smart $]

On a bank of 3 120/208 600a 3 phase x-formers, can you get 120/240 single phase using the taps of all 3 x-formers???
This is used for a service to an RV campground. Thanks

I believe you can! ...but I'd prefer some corroboration from the more knowledgeable transformer patrons...

Provided the transformers (or bank of such hereafter) have delta-connected primaries, reverse connect B and C on one of the transformers and the secondary of this transformer will be 60? out-of-phase with the "forward-connected" transformers. Where (') designates secondary terminal on reverse-connected transformer, a' to N-Grd will be 180? out-of-phase with b to N-Grd. The same goes for b' to a, and c' to c.

As to the practicability of this configuration, I make no warrants

 

[coulter]

I'm impressed. I can honestly admit I never would have thought of that. ----------thinking-----------Nope. Still haven't

 

[winnie]

Smart $, I agree: you would get the necessary 180 degree phase relationships to get 240V...though if anyone got a panel wired (using your notation) a, n, a' (or other similar sets), then they would have 120V line-neutral, and 120V line-line, essentially a corner grounded delta. That would probably cause a bit of head scratching.

The OP mentioned a bank of _3_ transformers. Question back to Jimmyabtl: It seems strange to me to have 3 each 3 phase transformers. Could they possibly be single phase transformers arranged in a three phase bank?

-Jon

 

[Smart $]

Smart $, I agree: you would get the necessary 180 degree phase relationships to get 240V...though if anyone got a panel wired (using your notation) a, n, a' (or other similar sets), then they would have 120V line-neutral, and 120V line-line, essentially a corner grounded delta. That would probably cause a bit of head scratching.

Agreed. It would be necessary to wire three 120/240 SDS panels to the respective terminals depicted to the right of the following image. After proper termination, each system would simply have L1, L2, and N... so ungrounded feeder conductors could be labeled, say...

a = 1-L1 and b' = 1-L2
b = 2-L1 and a' = 2-L2
c = 3-L1 and c' = 3-L2​