Motor with Electromagnets on Stator and Rotor?

What if you had a normal BLDC DD hub motor, but instead of magnets on the rotor you had another set of electromagnets? To make this work you could have separate batteries spin with the rotor, so no cord would get twisted. I'm imagining an even number of poles on the stater and rotor, which line up together. All poles would always be active, simply switching polarity in sync to keep attracting and opposing the one next to it.

Would a motor like this be any good in practice, and what pros/cons would it have? Obviously it couldn't self start reliably but i don't see that being a issue with ebikes (just give a little push first). It could also have 0 cogging when powered off i believe due to lack of permanant magnets.

It's called an "wound rotor synchronous motor" and the stator is usualy powered with brushes.
If the stator is closed loop on itself it's called an asynchronous motor or induction motor and the stator doesn't need external powering

Envoyé de mon Redmi Note 3 en utilisant Tapatalk

An induction motor is also a motor with electromagnets on the stator and rotor, The current in de rotor is induced via the stator windings.