[keithorr]

I need to make the primary connections from 480 delta to a machine transformer.

Do I need to be concerned with phase sequence? If I connect the leads "backwards" on a motor, the motor spins in the wrong direction, which is easy to identify and change.

Can a transformer (480primary/210secondary) be connected in any sequence?

[HuFlungDung]

Yes, it can be connected in any sequence. Each leg has the same potential and phase difference to either of the other two.

[Al_The_Man]

Do I need to be concerned with phase sequence? If I connect the leads "backwards" on a motor, the motor spins in the wrong direction, which is easy to identify and change.
Can a transformer (480primary/210secondary) be connected in any sequence?

As Hu pointed out it can be connected any sequence, but the usual way is to hook the transformer to the machine and test one of the non-critical 3 phase motors that the machine may have to see if the rotation is correct, and then if neccessary reverse two of the incoming phases, rather than reverse at the motors. There are some rare occasions that reversing the phases can cause damage and these machines are often fitted with a phase rotation detector, to prevent this. One typical use is in elevators, It would be a bit of a shock to push the down button and go up

:nono:
Al

[keithorr]

The transformer is stepping down 480 to a variety of voltages for a robot controller. AC servo motors, 15v for encoders, 24v for brakes, 5v for this, and -15v for that.
I hooked it up, no sparks, and now I get to play and try not to kill myself.
Fortunately, any encoder error or wire break shuts the whole thing down. I know, cause I just spent two hours rebuilding a plug to get rid of the wiggle which was causing from 1-6 axis to show error signals.
Thanks for your help.