Interior permanent magnet machine for automotive electric vehicles
View Patent ↗Certain aspects relate to topologies for an interior permanent magnet (IPM) electrical machine having increased saliency torque, increased flux-linkage, reduced magnet leakage flux, and reduced detrimental slotting effects compared to existing IPM electrical machines. The IPM electrical machine includes a rotor having a number of poles and a flux barrier formed along the edge of the rotor between poles. The flux barrier contains a magnet or set of magnets having a varying thickness, with a central thickest portion located along the d-axis of the rotor. A magnet retention structure, which may be formed integrally with the rotor or provided as a separate structure, surrounds the rotor and magnets. The rotor and magnets combine to form a smooth circular profile having no air gaps.
1. A rotor assembly for an interior permanent magnet electrical machine, the permanent magnet assembly comprising:
a magnet retention structure comprising a circular inner perimeter having a radius;
a rotor body within the magnet retention structure, the rotor body having a plurality of pole shoes;
at least a first permanent magnet set including a plurality of permanent magnets positioned within the magnet retention structure and between two adjacent pole shoes of the rotor body, the first permanent magnet set having a varying thickness that is greatest at a central portion of the first permanent magnet set and tapers toward opposing edges of the first permanent magnet set; and
at least one magnet support extending from the rotor body to the magnet retention structure through the varying thickness of the first permanent magnet set.
2. The rotor assembly of claim 1 , wherein the at least one magnet support separates adjacent magnets of the first permanent magnet set.
3. The rotor assembly of claim 1 , further comprising:
a second permanent magnet set positioned within the magnet retention structure and between two adjacent pole shoes of the rotor body, the second permanent magnet set having the varying thickness that is greatest at a central portion of the second permanent magnet set and tapers toward opposing edges of the second permanent magnet set; and
at least one additional magnet support extending from the rotor body to the magnet retention structure through the varying thickness of the second permanent magnet set.
4. The rotor assembly of claim 1 , wherein the rotor comprises a magnetically permeable material, the magnet retention structure comprising the magnetically permeable material and formed integrally with the rotor body.
5. The rotor assembly of claim 4 , the at least one magnet support comprising the magnetically permeable material and formed integrally with the rotor body.
6. The rotor assembly of claim 1 , wherein the rotor body comprises:
the plurality of rotor pole shoes, an outer edge of each of the plurality of rotor pole shoes having the same radius as the circular inner perimeter of the magnet retention structure and positioned adjacent to the circular inner perimeter of the magnet retention structure; and
a plurality of curved edges each connecting outer edges of an adjacent two of the plurality of rotor pole shoes,
wherein the first permanent magnet set and the at least one magnet support are positioned between one of the plurality of curved edges and the magnet retention structure.
7. The rotor assembly of claim 6 , wherein the at least one magnet support extends from the one of the plurality of curved edges to the circular inner perimeter of the magnet retention structure.
8. The rotor assembly of claim 7 , wherein the at least one magnet support comprises a first magnet support and a second magnet support, and wherein the first and second magnet supports contact each other at the circular inner perimeter of the magnet retention structure and angle away from one another as they extend toward the one of the plurality of curved edges.
9. The rotor assembly of claim 1 , wherein the at least one magnet support comprises a first magnet support and a second magnet support arranged in a parallel configuration.
10. The rotor assembly of claim 1 , wherein:
the first permanent magnet set includes first, second, and third permanent magnets;
the at least one magnet support comprises a first magnet support and a second magnet support;
the first magnet support is positioned between the first and second permanent magnets; and
the second magnet support is positioned between the second and third permanent magnets.
11. The rotor assembly of claim 10 , wherein the first and second magnet supports angle away from each other as they extend toward the circular inner perimeter of the magnet retention structure.
12. The rotor assembly of claim 1 , wherein a point of contact between the at least one magnet support and the rotor body is radiused.
13. The rotor assembly of claim 1 , wherein a point of contact between the at least one magnet support and the magnet retention structure is radiused.