Spoke permanent magnet machine with reduced torque ripple and method of manufacturing thereof

A method for assembling an internal permanent magnet machine, the method comprising:

• providing a stator assembly comprising a stator core having a plurality of stator teeth, with stator windings wound on the stator teeth to generate a stator magnetic field when excited with alternating currents;
• and
• providing a rotor assembly that is rotatable within a cavity formed by the stator assembly, wherein providing the rotor assembly comprises:
• providing a shaft comprising a plurality of protrusions, wherein the protrusions extend radially along an axial length of the rotating shaft and are formed circumferentially about the shaft;
• placing a plurality of stacks of laminations onto the plurality of shaft protrusions of the shaft such that the plurality of stacks of laminations are positioned circumferentially around the shaft and such that each of the plurality of stacks of laminations is arranged into a plurality of lamination groups along the axial length of the shaft, with the plurality of stacks of laminations being placed onto the plurality of shaft protrusions of the shaft such that adjacent lamination groups in each stack of laminations are positioned on the shaft to have an angular offset relative to each other;
• and
• securing a plurality of permanent magnets in openings defined by the plurality of stacks of laminations, the plurality of permanent magnets generating a magnetic field that interacts with the stator magnetic field to produce a torque.

A rotor assembly for use in an internal permanent magnet machine, the rotor assembly comprising:

• a shaft including a shaft body and a plurality of protrusions extending radially outward from the shaft body, the plurality of protrusions being formed along an axial length of the shaft and circumferentially about the shaft;
• a plurality of stacks of laminations disposed on the radial protrusions, wherein each of the plurality of stacks of laminations comprises a plurality of lamination groups arranged axially along the shaft and wherein each of the plurality of lamination groups comprises a plurality of laminations;
• and
• a plurality of permanent magnets disposed between the plurality of stacks of laminations;
• wherein a shape of the laminations in each of the plurality of lamination groups of a stack of laminations is different from the shape of the laminations in others of the plurality of lamination groups in a stack of laminations.