Transformer

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kiss

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Today I came across a job with the following: Transformer rated at Y - Delta. 120/208 primary 3 Phase - 480 Volts Secondary.
3 wires on primary NO nuetral 120/208 Volts. Secondary 480 Volts. This transformer was not grounded. What is the correct way to ground this type of an installation? I also believe that a Delta - Delta should have been used. Any help is appreciated. P.S. This is not part of any service , just an add on in a location where 480Volts is required.
 
Re: Transformer

The primary connection (coil configuration) is not really important on less than 600V transformers, we just need to bring in the 3 phase conductors. Almost never is a wye connected primary ever grounded because (among other things) it would effectively create a multiple neutral to ground connection.

Now to the secondary. The NEC requires all steel (equipment) to be bonded to the building ground system. However the line (phase) conductors of a 480V Delta connection are not required to be referenced to ground.
 
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