US Patent 8232700 Multi-rotor electric machine

Electric machines comprising a plurality of magnetized rotors, preferably including bi-pole magnets. The rotors are configured to drive and/or be driven by a common shaft, as for example by suitable configurations of gears. The rotors are magnetically indexed, in pairs, with respect to each other and to corresponding electrical windings, such that, when a current is passed through the one or more windings, the rotors provide phased rotary power to the common shaft; or, when torque is applied to the common shaft, a phased electrical output is provided to the windings.