480V Single Phase with Grounded Leg

[jbt260]

I am looking for a way create a 480V single phase feeder with one leg grounded. The load is 48KVA. I am trying to create this from a 480/277V, three phase feeder. Does anyone make a 50KVA, 480V-480V single phase transformer ?

Thanks in advance!

[bob]

Originally Posted by jbt260

I am looking for a way create a 480V single phase feeder with one leg grounded. The load is 48KVA. I am trying to create this from a 480/277V, three phase feeder. Does anyone make a 50KVA, 480V-480V single phase transformer ?

Thanks in advance!

Why do you have to have one leg grounded? Take 2 of the 3 phases plus an egc and you have 480 volts single phase.

[jbt260]

Sorry for lack of info. I have to re-feed an existing roadway lighting circuit that is 480V single phase with a grounded leg. The leg is grounded at every light pole.

[bob]

Originally Posted by jbt260

Sorry for lack of info. I have to re-feed an existing roadway lighting circuit that is 480V single phase with a grounded leg. The leg is grounded at every light pole.

I am not sure that meets the NEC groounding requirements. I believe you need a EGC to each pole rather that using the neutral. Maybe someone will confirm this.

[Cavie]

480 2 wire single phase. 1 hot 1 neutral and a ground. Very common in street lighting. Something I learned after being an electrican for 40 years.

[brian john]

Originally Posted by Cavie

480 2 wire single phase. 1 hot 1 neutral and a ground. Very common in street lighting. Something I learned after being an electrican for 40 years.

480 VAC Single phase is one hot, one grounded conductor and one EGC. I would think?

[Cavie]

Originally Posted by jbt260

Sorry for lack of info. I have to re-feed an existing roadway lighting circuit that is 480V single phase with a grounded leg. The leg is grounded at every light pole.

Check with your local POCO. Why arn't they supplying you?

[benaround]

Originally Posted by jbt260

. The leg is grounded at every light pole.

jbt, What does this mean?

[mattsilkwood]

Someone please tell me if im wrong, but wouldn't a regular 480v circuit (480 L1-L2) do the same thing? the light isnt going to know if one conductor is grounded, and you're not going to bond the poles.

[jbt260]

A tfmr manufacturer came up with a solution for a 50KVA, 480V-480V, single phase transformation. They suggest using two 25KVA, 240x480V Primary, 120/240V Secondary, single phase transformers. You wire the primaries in parallel for 480V. You wire the secondaries in series for 480V. See attached diagram. Any thoughts are welcome !