happycamper002 wrote:
The usual tech term for dual phase is "two phase" which is derived from two totally separate power sources (i.e. two transformers, two generators etc.) ...no intermingling of the two power sources. This setup is common in industrial heavy demand load like 50-100 horsepower motors. Crushers for cement aggregate plants for example. Steel forging plants with those heavy hammers.
All legs of a motor physically have to be in phase (from the same source) for the load to stay balanced, and there is no NEC code section providing for seperate sources (seperate service) to intermingle, other than a few exceptions.