| 摘要 |
An electric motor assembly comprises a stator 12 having plural permanent magnets 13 and plural electro-magnets 14; a rotor having a rotation axis 15 with respect to the stator; and a circumferentially extending stator cover 20 comprises plural magnetic portions 21. A method of making the motor comprises adapting a thickness of the stator cover according to a determination of the total iron loss (fig 6) for various operating conditions, and the associated stator cover thickness required to minimise the total loss. The stator cover can be adjacent the outer or the end surface of the stator (fig 9) and move circumferentially, radially or axially with respect to the stator. A magnetic portion of the cover can move between positions that are remote from or proximate to a permanent magnet 13 and overlap an adjacent electro-magnet. Magnetic portions can be uniform in cross section, or non-uniform having a radially increasing (fig 7B, 7C) or stepped (fig 7D) thickness. Magnetic portions 21 can be: coupled together by non-magnetic portions 22; formed of iron; of a length equal to that of the permanent magnets; and of thickness between 2 and 30 mm. Movement of the stator cover allows for control of the efficiency of the electric motor which can be a flux-switching permanent magnet electric motor, and be applied to a vehicle drive train or an industrial machine such as a pump. |
