An electric machine includes a generally annular outer rotor supported to rotate about a rotational axis. The outer rotor defines an internal cavity therein and has a plurality of permanent magnets in the internal cavity generating a first magnetic field. An inner rotor is in the internal cavity and is supported to rotate about the rotational axis. The inner rotor has a plurality of permanent magnets about its perimeter that generate a second magnetic field. A generally annular stator is in the internal cavity between the outer rotor and the inner rotor. The stator has a stator winding supported by a non-magnetically conductive stator core. The stator winding is arranged to generate a field that interacts with the first and second magnetic fields. One of the outer rotor or the inner rotor is mechanically coupled to drive a load. The other of the outer rotor or the inner rotor is not mechanically coupled to drive the load.