Doubly fed electric motors have two independent multiphase winding sets, which <answer>contribute active (i.e., working) power to the energy conversion process</answer>, with at least one of the winding sets electronically controlled for variable speed operation. Two independent multiphase winding sets (i.e., dual armature) are the maximum provided in a single package without topology duplication. Doubly-fed electric motors are machines with an effective constant torque speed range that is twice synchronous speed for a given frequency of excitation. This is twice the constant torque speed range as singly-fed electric machines, which have only one active winding set.
What advanage do independent multiphase winding sets have?
contribute active (i.e., working) power to the energy conversion process