Patent ID: 6867525

Claim:
An electrical machine having an output rating (P x ), the electrical machine comprising: a shaft rotatable about an axis; a stator including a stator core and windings, the stator core having a fixed cross-sectional profile with respect to the axis; and a rotor coupled to the shaft and adapted to magnetically interact with the stator, the rotor having a periphery, the rotor being configured to include three or more axial sections, each of the axial sections having a respective magnetization pattern of alternating magnetic poles skewed with respect to the axis, the magnetization pattern for each of the axial sections being different than any adjacent axial section, the three or more axial sections defining a total length (L x ) in the axial direction with respect to the axis, where (L x ) satisfies the relationship (0.75 (P x /P m )≦(L x /L m )≦1.5 (P x /P m )), where (P m ) is a chosen maximum output rating for an electrical machine built with a stator core having the fixed cross-sectional profile, where (L m ) is the length corresponding to the length of the rotor for the maximum output rating (P m ), where (P x ) is less than the maximum output rating (P m ), and where each of the axial sections define an arc of skew (β) at the periphery, (β) being the same for each of the axial sections.