This rotor arrangement can increase power volume density, efficiency, and reduce cogging torque.
The effect of the inner rotor is to reenforce the field from the stator.
[1] Because the stator slips behind the rotating magnetic field inducing a current in the rotor, this type of motor meets the definition of an induction motor.
[5] Vendors are working on both axial[6] and radial flux configurations.
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