Methods and apparatus for a permanent magnet machine with an added air barrier
An internal permanent magnet machine (“IPM machine”) of the type used, for example, with traction motors and hybrid electric vehicles, includes a rotor with an additional air barrier provided above the first magnet barrier in the same rotor slot. Each magnet only fills a portion of each cavity, thereby defining the air barriers. The added air barrier above the permanent magnet of the first layer acts as a barrier to the first layer magnet and lowers the magnet flux.
1. An interior permanent magnet machine comprising:
a wound stator;
a rotor configured to magnetically interact with the wound stator, the rotor having an outer surface and a rotational axis extending through a center of the rotor;
a pair of cavities provided within the rotor, each cavity having a total volume and a generally rectangular opening having a cavity axis, a width dimension, and a length dimension, wherein the length dimension is greater than the width dimension, the cavity axis lies parallel to the length dimension, and the cavity axes of the pair of cavities together define a plane that is orthogonal to the rotational axis;
a pair of magnets provided within respective cavities of the pair of cavities such that the total volume of each cavity is only partially filled by the respective magnet and such that air barriers are formed adjacent to each magnet;
wherein the pair of magnets each have top edges parallel to the cavity axis that together define an obtuse angle facing radially outward from the center of the rotor, and wherein the air barriers include a pair of top air barriers adjacent to and extending along substantially the entire length of the top edges of each of the respective magnets.
2. The interior permanent magnet machine of claim 1 , wherein the top air barriers are generally trianguloid.
3. The interior permanent magnet machine of claim 2 , wherein the generally trianguloid top air barriers each have an apex adjacent to a corner of the magnet closest to the outer surface.
4. The interior permanent magnet machine of claim 1 , wherein the air barriers further include a side air barrier adjacent to the top air barrier.
5. The interior permanent magnet machine of claim 1 , wherein the air barriers further include a bottom air barrier adjacent to the magnet opposite the top air barrier.
6. The interior permanent magnet machine of claim 1 , further including a second set of air barriers non-contiguous with the air barriers formed by the cavities.
7. A method of manufacturing an interior permanent magnet machine, the method comprising:
providing a wound stator;
providing a rotor having an outer surface and a rotational axis extending through a center of the rotor;
forming a plurality of cavities within the rotor, each cavity having a total volume and a generally rectangular opening having a cavity axis, a width dimension, and a length dimension, wherein the length dimension is greater than the width dimension, the cavity axis lies parallel to the length dimension, and the cavity axes of the pair of cavities together define a plane that is orthogonal to the rotational axis;
disposing a plurality of magnets within the plurality of cavities such that the total volume of each cavity is only partially filled by the respective magnet and such that air barriers are formed adjacent to each magnet, and such that a pair of magnets have respective top edges parallel to their respective cavity axes, wherein the top edges together define an obtuse angle facing radially outward from the center of the rotor, and the air barriers include a pair of top air barriers adjacent to and extending along substantially the entire length of the top edges of each of the respective magnets; and
placing the wound stator in magnetic communication with the rotor.
8. The method of claim 7 , wherein the top air barriers are generally trianguloid.
9. The method of claim 8 , wherein the generally trianguloid top air barriers have an apex adjacent to a corner of the magnet closest to the outer surface.
10. The method of claim 7 , wherein the air barriers further include a side air barrier adjacent to the top air barrier.
11. The method of claim 7 , wherein the air barriers further include a bottom air barrier adjacent to the magnet opposite the top air barrier.
12. The method of claim 7 , further including a second set of air barriers non-contiguous with the air barriers formed by the cavities.
13. A traction motor of the type used in connection with a hybrid electric vehicle, the traction motor comprising:
a wound stator;
a rotor configured to magnetically interact with the wound stator, the rotor having an outer surface and a rotational axis extending through a center of the rotor;
a plurality of cavities provided within the rotor, each cavity having a total volume and a generally rectangular opening having a cavity axis, a width dimension, and a length dimension, wherein the length dimension is greater than the width dimension, the cavity axis lies parallel to the length dimension, and the cavity axes of a pair of cavities together define a plane that is orthogonal to the rotational axis;
a plurality of magnets provided within the plurality of cavities such that the total volume of each cavity is only partially filled by the respective magnet and such that air barriers are formed adjacent to each magnet, wherein a pair of the plurality of magnets have respective top edges parallel to the cavity axes, the top edges together define an obtuse angle facing radially outward from the center of the rotor, and wherein the air barriers include a pair of top air barriers adjacent to and extending along substantially the entire length of the top edges of each of the respective magnets.
14. The traction motor of claim 13 , wherein the top air barriers are generally trianguloid.
15. The traction motor of claim 14 , wherein the generally trianguloid top air barriers have an apex adjacent to a corner of the magnet closest to the outer surface.
16. The traction motor of claim 14 , wherein the air barriers further include a side air barrier adjacent to the top air barrier.
17. The traction motor of claim 14 , wherein the air barriers further include a bottom air barrier adjacent to the magnet opposite the top air barrier.
18. The traction motor of claim 14 , further including a second set of air barriers non-contiguous with the air barriers formed by the cavities.
19. The interior permanent magnet machine of claim 2 , wherein each magnet of the pair of magnets has a first corner closest to the stator, and wherein each of the top air barriers has an apex that is adjacent to the first corner of its respective magnet.