Interior magnet machine with reduced cogging
An interior permanent magnet machine has non-contiguous, non-magnetic radial slots between the magnets and the cylindrical periphery and the magnets have non-magnetic radial end slots.
1. A rotor comprising:
a cylindrical periphery having a central axis of rotation;
a cross-section taken perpendicular to the central axis of rotation, said cross-section of the rotor comprising:
a plurality of interior permanent magnets, each interior permanent magnet having two poles and having a longitudinal dimension which is greater than a transverse dimension;
a plurality of non-magnetic peripheral slots, at least one non-magnetic peripheral slot associated with each pole of the interior permanent magnets, each non-magnetic peripheral slot positioned between the cylindrical periphery and its associated interior permanent magnet, wherein each non-magnetic peripheral slot is not contiguous with its associated interior permanent magnet, wherein each non-magnetic peripheral slot has a longitudinal dimension which is greater than a transverse dimension, wherein an axis of the longitudinal dimension of each non-magnetic peripheral slot is not perpendicular to an axis of the longitudinal dimension of its associated interior permanent magnet, and wherein at least one non-magnetic peripheral slot has a substantially different shape than another non-magnetic peripheral slot; and
a plurality of non-magnetic end slots, each non-magnetic end slot contiguous to and integral with each end of each pole of each interior permanent magnet, wherein at least part of each non-magnetic end slot has a central axis which is not aligned with a radius of the rotor.
2. The rotor of claim 1 wherein the non-magnetic peripheral slots associated with each interior permanent magnet pole have different lengths.
3. The rotor of claim 1 wherein at least two non-magnetic peripheral slots are associated with each pole of the interior permanent magnets.
4. The rotor of claim 1 wherein the end slots have a longitudinal dimension which is greater than a transverse dimension and wherein adjacent end slots have parallel central axes along their longitudinal dimension.
5. The rotor of claim 4 wherein opposite end slots have aligned central axes along their longitudinal dimension.
6. The rotor of claim 1 wherein the interior permanent magnets have a rectangular cross-section taken perpendicular to the central axis of rotation.
7. The rotor of claim 1 wherein the peripheral slots and the end slots are spaced substantially the same distance from the periphery.
8. The rotor of claim 1 wherein the cross-section is symmetrical about a line perpendicular to the interior permanent magnets and intersecting the central axis of rotation.
9. The rotor of claim 1 wherein the axis of the longitudinal dimension of each non-magnetic peripheral slot does not intersect the central axis of rotation.
10. A machine comprising a stator and the rotor of claim 1 .
11. A rotor comprising:
a cylindrical periphery having a central axis of rotation;
a cross-section taken perpendicular to the central axis of rotation, said cross-section of the rotor comprising:
a plurality of interior permanent magnets, each interior permanent magnet having two poles and having a longitudinal dimension which is greater than a transverse dimension; and
a plurality of non-magnetic peripheral slots, at least one non-magnetic peripheral slot associated with each pole of the interior permanent magnets, each non-magnetic peripheral slot positioned between the cylindrical periphery and its associated interior permanent magnet, wherein each non-magnetic peripheral slot is not contiguous with its associated interior permanent magnet, wherein each non-magnetic peripheral slot has a longitudinal dimension, wherein an axis of the longitudinal dimension of each non-magnetic peripheral slot is not perpendicular to an axis of the longitudinal dimension of its associated interior permanent magnet, and wherein at least one non-magnetic peripheral slot has a substantially different shape than another non-magnetic peripheral slot.
12. The rotor of claim 11 wherein at least one non-magnetic peripheral slot is tear-shaped.
13. A machine comprising a stator and the rotor of claim 11 .
14. A rotor comprising:
a cylindrical periphery having a central axis of rotation;
a cross-section taken perpendicular to the central axis of rotation, said cross-section of the rotor comprising:
a plurality of interior permanent magnets, each interior permanent magnet having two poles and having a longitudinal dimension which is greater than a transverse dimension; and
a plurality of non-magnetic peripheral slots, at least one non-magnetic peripheral slot associated with each pole of the interior permanent magnets, each non-magnetic peripheral slot positioned between the cylindrical periphery and its associated interior permanent magnet, wherein each non-magnetic peripheral slot is not contiguous with its associated interior permanent magnet, wherein each non-magnetic peripheral slot has a longitudinal dimension, wherein an axis of the longitudinal dimension of each non-magnetic peripheral slot is not perpendicular to an axis of the longitudinal dimension of its associated interior permanent magnet, and wherein at least one non-magnetic peripheral slot is tear-shaped.
15. The rotor of claim 14 wherein a plurality of non-magnetic peripheral slots are tear-shaped.
16. The rotor of claim 14 wherein the cross-section of the rotor includes only tear-shaped non-magnetic peripheral slots.
17. A machine comprising a stator and the rotor of claim 14 .
18. A rotor comprising:
a cylindrical periphery having a central axis of rotation;
a cross-section taken perpendicular to the central axis of rotation, said cross-section of the rotor comprising:
a plurality of interior permanent magnets, each interior permanent magnet having two poles and having a longitudinal dimension which is greater than a transverse dimension; and
a plurality of non-magnetic peripheral slots, at least one non-magnetic peripheral slot associated with each pole of the interior permanent magnets, each non-magnetic peripheral slot positioned between the cylindrical periphery and its associated interior permanent magnet, wherein each non-magnetic peripheral slot is not contiguous with its associated interior permanent magnet, wherein each non-magnetic peripheral slot has a longitudinal dimension, wherein an axis of the longitudinal dimension of each non-magnetic peripheral slot is not perpendicular to an axis of the longitudinal dimension of its associated interior permanent magnet, and wherein at least one non-magnetic peripheral slot is S-shaped.
19. The rotor of claim 18 wherein a plurality of non-magnetic peripheral slots are S-shaped.
20. The rotor of claim 18 wherein the cross-section of the rotor includes only S-shaped non-magnetic peripheral slots.
21. A machine comprising a stator and the rotor of claim 18 .