Rotor for a synchronous reluctance machine
View Patent ↗A rotor for a synchronous reluctance machine wherein a torque ripple behaviour of the machine is optimized by altering the geometry of insulating barriers of the rotor. A q-axis pitch angle is used as a design variable instead of setting its value equal to the rest of the rotor slot pitches or binding its value to the stator slot pitch. The resulting rotor has a non-regular slot pitch across the q-axis and substantially regular slot pitch otherwise. Synchronous reluctance machines that employ rotor discs and rotor assemblies in accordance with the present invention may exhibit low torque ripple without sacrificing high torque values.
1. A rotor for a synchronous reluctance machine, a cross-section of the rotor comprising:
four pole sectors arranged symmetrically about a central aperture of the cross-section, each pole sector comprising a plurality of insulating barriers, each insulating barrier extending between two pitch points,
a plurality of q-axes, each q-axis defining a direction of maximum reluctance of the corresponding pole sector,
a perimeter defining the outer contour of the cross-section,
a plurality of reference points located on the perimeter symmetrically with regard to the q-axes, the angular intervals between the reference points defining reference angles which between two circumferentially adjacent q-axes have an equal value of α m =γ/(k−1), where γ is an angle between two pitch points that are furthest apart between two circumferentially adjacent q-axes and k is the number of pitch points between two circumferentially adjacent q-axes,
a q-axis pitch angle defined by an angular distance δ between two circumferentially adjacent pitch points on opposite sides of a q-axis, the q-axis pitch angle having a value which is different from δ=3*α m ,
the angular positions of each pitch point and the reference point closest to that pitch point have a deviation having a value Δ T less than 2.5 degrees, characterized in that
the q-axis pitch angle has a value δ 50 degrees or less.
2. The rotor according to claim 1 , wherein the angular positions of the pitch points and the closest reference points have a deviation having a value Δ T less than 2 degrees, such as less than 1 degree.
3. The rotor according to claim 1 , wherein the q-axis pitch angles differ from δ=3*α m by at least 1 degree, such as at least 2, 3, 5 or 10 degrees.
4. The rotor according to claim 1 comprising a radial rib across an insulating barrier for improving the mechanical strength of the rotor.
5. The rotor according to claim 1 comprising a cut-off at the rotor perimeter on a q-axis.