Step up transformer

[Doug E]

Originally Posted by Doug E
Have a 208 3 phase service need to add 3 phase 480v 100a panel to feed some 480v equipment ( motors )
What size transformer is needed ?
What size breaker in 208v 3p panel to feed transformer
Is disconnect needed ? Xmmf located next to panel
Where can I purchase step up transformer 120v/208v 3p primary to 480v secondary this will only be feeding 480v motors so no neutral needed
Thank-you
Doug

 

[electrofelon]

Originally Posted by Doug E
Have a 208 3 phase service need to add 3 phase 480v 100a panel to feed some 480v equipment ( motors )
What size transformer is needed ?
What size breaker in 208v 3p panel to feed transformer
Is disconnect needed ? Xmmf located next to panel
Where can I purchase step up transformer 120v/208v 3p primary to 480v secondary this will only be feeding 480v motors so no neutral needed
Thank-you
Doug

To get things started look at 450.3(B), 240.21(C), 408.36.

Probably best to use a Delta -wye and ground the 480 side, even though you don't need a neutral.

A 75 KVA would be a common some for feeding a 100 amp 480 panel, bit it could be smaller depending on what the load is. Call a supply house and get a quote.

 

[jap]

I agree.

I was going to say, probably a 75, roughly a 225 or better, the disconnect is the breaker in the panel and any local supply house.

JAP>

 

[electrofelon]

I would also add, since lots of people mix this up at first, note 450.3 is just about the transformer itself NOT the conductors. That section doesnt allow you to protect the primary conductors above their ampacity.