480 volt delta to 480 volt wye

[oldno7]

I need to get power to a machine in a weld shop. The building is supplied with 480v delta. There is a 480v bus duct that runs along where the machine is going to be installed. Power supply line has to be large enough to handle 245 full load amps at 480v, 3 phase, 60 hertz. Main circuit breaker in control 300 amps. Maximum short circuit interruption capacity of the main circuit breaker 30,000 amps.
In the specs it says the three phase power configuration must be a symmetrical 4 conductor WYE line supply network with a grounded neutral point. For all other line supply types (3 wire Delta), a customer supplied isolation transformer with a grounded neutral point on the secondary side is required.
This would be my first 480 Delta to 480/277 Wye install. Could anyone help me on this one? Anything different than 480 Delta to 208/120 Wye.

Do I need Transformer fault sensing installed?(in the form of donut type current transformers?)

 

[iwire]

Have you installed a 480 delt to 208Y/120 transformer?

If so this is the same thing only the transformer will have a 1 to 1 ratio.

If not take a look at the rules in Article 450 and 250.30

 

[kingpb]

The 480 delta to 480Y/277V is pretty straight forward. Since the short circuit capability of the main CB on the machine is 30KA, you should be fine seeing how it is doubtful you would need a 1500 KVA xfmr with a Z=5.75%.

You do need to make sure the KVA rating of the transformer, and impedance of the transformer are such that the machine will be able to start and operate. If the machine is predominantly one single motor that starts full voltage across the line, then the xfmr will need to be upsized at least 2X, maybe more, and possibly a lower then standard impedance.