Importance

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Abstract

An electric machine (100) comprises a stator (112) and a rotor (114a, b) mounted for rotation about a rotor axis (120) with respect to the stator. Permanent magnets (124a, b) are carried by the rotor. The rotor has an output (190). The stator has coils (122) wound on stator bars (116) for interaction with the magnets. The rotor has two stages (114a,b) arranged one at either end of the stator bars, with two air gaps (126a,b) between the ends of the bars and the rotor stages. An annular housing (102, 142a, b, 146) retains and mounts the stator. A bearing (164a, b) is between the rotor and stator, the rotor being hollow around said rotor axis. There are two significant magnetic flux paths (30,30′) of the motor. The first passes between adjacent coils in a circuit on a substantially circumferential plane with respect to the axis (120). A second path 30′ is in an axial plane, passing around the bearing. The stator coils are spaced around the rotor axis and approach the rotor axis no closer than a first, stator radius (R₁) of the stator. The bearing comprises rolling elements rolling on a surface of the rotor that is no closer to the rotor axis than a second, rotor radius (r), which rotor radius is between 60% and 90% of the stator radius.

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