Control Transformer Question

[keebler303]

I am getting ready to install a control transformer in a machine to supply 120 AC for various components. The transformer is 480V primary, 120V secondary. I am hooking the primary across 2 legs of the 480 3 phase supply. The question is should I connect the neutral of the secondary to ground or leave it floating? will this cause any problems if I use the true ground and the "floating" power from the transformer on my 120V devices?

Thanks in Advance
Matt

[Al_The_Man]

It is optional, but the customary way is to ground one side of the secondary immediately at the transformer terminals, this should be bonded to the system ground also.
If using an isolated 120v, i.e. no grounded neutral, then each 120v leg is fused.
On setting up a grounded neutral, only the 'live' side is fused.
Al.

[keebler303]

If I kept the 120V isolated, where would I connect the ground for the 120V devices?

Thanks
Matt

[Al_The_Man]

The same place as before, from the system ground point or ground plate to the metal case of the device.
The 120v circuit itself would be isolated from ground.
BTW, If grounding one side of the secondary, the neutral is also connected to this point, but this is used to supply the neutral side of all 120v devices.
Although at the same potential, the ground itself is never used a conductor.
Al.

[keebler303]

Ok

Thanks for the help Al.

Matt