Abstract: A hybrid induction motor includes a fixed stator, an independently rotating Hybrid Permanent Magnet/squirrel Cage (HPMSC) outer rotor, and a Squirrel Cage (SC) inner rotor fixed to a motor shaft. The HPMSC rotor has spaced part permanent magnets and sets of first bars between consecutive permanent magnets. The SC rotor has groups of second bars, and slots in an outer surface between consecutive groups of the second bars. The HPMSC rotor is initially accelerated by cooperation of the stator with the first bars. The permanent magnets create a rotating magnetic field cooperating with the second bars to accelerate the SC rotor. As the HPMSC rotor accelerates towards synchronous RPM, the stator field reaches into the HPMSC rotor and cooperates with the permanent magnets to transition to synchronous operation. Salient poles created by cooperation of the permanent magnets with the slots lock the two rotors at synchronous RPM.

Abstract: A hybrid induction motor includes a fixed stator, an independently rotating outer rotor, and an inner rotor fixed to a motor shaft. In one embodiment the outer rotor includes spaced apart first bars and permanent magnets, and the inner rotor includes spaced apart second bars. In another embodiment the outer rotor includes angularly spaced apart first bars but no permanent magnets, and the inner rotor includes permanent magnets and may also include angularly spaced apart second bars. The outer rotor is initially accelerated by cooperation of a rotating stator magnetic field with the first bars. As the outer rotor accelerates towards synchronous RPM, the inner rotor is accelerated to transition to efficient synchronous operation. The outer rotor thus acts as a clutch to decouple the inner rotor from the rotating stator magnetic field at startup and to couple the inner rotor to the rotating stator magnetic field at synchronous speed.