2-speed motor wiring

[thinker]

We have to replace a standard induction motor with 2-speed motor which has 2 separately fed windings (Y1 for low speed and Y2 for high speed). We originally had a four conductor cable (three phase plus ground). There are a lot of arguments in our Eng. Dept. about wiring 2-speed motor. Variant 1: add the second four conductor cable and have each of Y1 and Y2 windings fed by separate cable. Variant 2: to use one cable with say 7 conductors (2x3-phase sets plus ground). Please give your comments on how to wire that motor in compliance with NEC.

 

[jraef]

You only need one ground connection. It is for safety, not for the actual windings themselves. The Y point in a motor winding is not grounded like in a transformer.

 

[waross]

I agree with jraef. The 7 conductor cable sounds good.
respectfully